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SEMICONDUCTORS

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New materials for organic electronics: from synthesis to processing, characterization and device physics

Organic semiconductors enable a wide range of applications such as solar cells, thin-film, transistors, sensors and thermoelectrics. The molecular design, nanostructure and device performance are intimately linked. This symposium aims to bring together key researchers in thisfield to discuss the main challenges towards the widespread application of organic electronics.

Scope:

New materials are being added to the plethora of already existing organic semiconductors every day. Their use in opto-electronic devices such as solar cells, thin-film transistors, sensors and thermoelectric generators continuously adds to our understanding of relevant structure-property relationships. This insight then provides critical feedback for the design of the next generation of organic semiconductors. As a result, the performance of organic electronic devices is rapidly improving and has reached a point where first applications have reached the verge of commercialization. Despite this progress, great challenges still have to be faced, mainly regarding: 

Synthesis

  1. The impact of defects on structure formation and opto-electronic properties is poorly understood.
  2. Many synthesis schemes are not scalable to larger volumes.

Processing

  1. Device optimization is typically done by a trial-and-error approach. General processing schemes that lead to reproducible nanostructures must be developed.
  2. New materials are first tested with lab-scale devices. The transfer of lab-scale to large-area processing routines has proven difficult. 

Characterisation of nanostructures

  1. Many opto-electronic processes occur on length-scales that are only difficult to access with traditional X-ray diffraction and microscopy techniques.
  2. Characterization of nanostructure formation must be carried out in-situ and in real time during drying of the processing solution.

Devices

  1. The environmental stability must be improved in order to pave the way for real products.
  2. Theoretical models that describe device operation do not capture the complexity of poorly ordered organic semiconductors.

Hot topics to be covered by the symposium:

  • synthesis of small molecular and polymer semiconductors;
  • organic semiconductor blends and (nano)composites;
  • processing additives, dopants, binder polymers;
  • thin-film processing schemes for e.g. patterning, orientation and anisotropic textures;
  • structure-processing-property relationships of organic semiconductors;
  • in-situ and real-time characterization tools;
  • device physics of organic solar cells, field-effect transistors, sensors, thermoelectrics etc.;
  • long-term stability and lifetime of materials and devices;
  • large-area processing and production;
  • improvement of performances of all-printed micro- and opto-electronics devices and circuits

List of invited speakers:

  • T. Anthopoulos (Imperial College London)
  • A. Bakulin (Cambridge)
  • P. Blom (MPI Mainz, Germany)
  • M. Brinkmann (ICS Strasbourg)
  • M. Campoy-Quiles (ICMAB-CSIC)
  • E. Da Como (University of Bath)
  • C. Deibel (Chemnitz University)
  • S. Fabiano (Linköping University)
  • E. Gomez (Penn State)
  • M. Heeney (Imperial College London)
  • R. A. Janssen (TU Eindhoven)
  • H. Klauk (Max Planck, Stuttgart)
  • C. Luscombe (University of Washington)
  • W. Maes (University of Hasselt)
  • Q. Nguyen (UC Santa Barbara)
  • Y.-Y. Noh (Dongguk University)
  • A. Salleo (Stanford University)
  • V. Subramanian (University of California, Berkeley)
  • J. Zaumseil (University of Heidelberg)
  • Feng Gao (Linköping University)
  • Daniele Fazzi (Max Planck Institut für Kohlenforschung, MPI-KOFO)

Publication:

Following the Symposium, a special issue will be published in Advanced Electronic Materials (Wiley) to which all invited speakers will be asked to contribute.

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Structure Property Relationships I : Enrique Gomez, Enrico Da Como, Artem Bakulin, Mario Caironi
09:00
Authors : Martin Brinkmann (1), Amer Hamidi-Sakr (1), Laure Biniek (1), Patrick Lévêque (2), Jean-Louis Bantignies (3), David Maurin (3), Nicolas Leclerc (4).
Affiliations : (1) Université de Strasbourg, CNRS, ICS UPR22, F67000 Strasbourg, France (2) Université de Strasbourg, CNRS, ENGEES, INSA, ICube UMR 7357, F-67000 Strasbourg, France (3) Université de Montpellier, Laboratoire Charles Coulomb, F34095 Montpellier, France (4) Université de Strasbourg, CNRS, ICPEES, UMR 7515, F67000 Strasbourg, France

Resume : This contribution focuses on recent advances in growth control and oriented crystallization of semi-conducting and conducting polymers. Particular emphasis will be given to the progress made in high-temperature rubbing of such polymers. This effective large scale alignment method can orient a large palette of polymer semiconductors (PSCs) with n- or p-type character without the use of an alignment substrate. The concurrent roles of the polymer molecular weight distribution and the rubbing temperature (TR) on the in-plane orientation have been rationalized for P3HT and PBTTT. Correlations are drawn between nanomorphology/crystallinity on one side and charge transport and optical properties on the other side. It is shown that the exciton bandwidth in P3HT crystals is determined by the length of the average planarized chain segments in the crystals. The high alignment and crystallinity observed for TR > 200 °C cannot translate to high hole mobilities parallel to the rubbing because of the adverse effect of amorphous interlamellar zones interrupting charge transport between crystalline lamellae. In a second part of this presentation, we show that soft doping of aligned PSCs yields highly oriented conducting polymer films with anisotropic charge conductivity and thermoelectric properties that are enhanced along the rubbing direction. The unique in-plane orientation in such conducting polymer films helps rationalizing the mechanism of redox doping.

L.1.1
09:30
Authors : Bob C. Schroeder, Tadanori Kurosawa, Tianren Fu, Yu-Cheng Chiu, Jaewan Mun, Ging-Ji Nathan Wang, Xiaodan Gu, Leo Shaw, James W. E. Kneller, Theo Kreouzis, Michael F. Toney, Zhenan Bao.
Affiliations : Bob C. Schroeder, James W. E. Kneller, Theo Kreouzis (Queen Mary University of London) Tadanori Kurosawa, Tianren Fu, Yu-Cheng Chiu, Jaewan Mun, Ging-Ji Nathan Wang, Xiaodan Gu, Leo Shaw, Michael F. Toney, Zhenan Bao (Stanford University)

Resume : Over the course of the last twenty years the field of semiconducting polymers has experienced huge developments, both in the fields of physics and materials chemistry. For a long time, chemists primarily focused on developing of new and ever more exotic conjugated materials. Even though novel organic semiconductors became more challenging to synthesize, physical properties like charge carrier mobilities started to stagnate. The focus therefore shifted from new material design to gradually improving the physical properties of organic semiconductors by modest chemical alterations. The most striking example of this development is increased interest in the alkyl side chains, which are no longer regarded primarily as solubility providing groups, but as attractive functional groups that can have a profound impact on the physical properties of organic semiconductors. Early studies on conjugated polymers came to the conclusion that an edge-on orientation of the polymer chains on the substrate was beneficial for efficient charge transport. This assumption however does not hold-up anymore with the emergence of high performing “push-pull” polymers, which show exceptionally high charge carrier mobilities in OFET devices without necessarily adopting a highly ordered edge-on orientation. In contrast, those materials show a strong preference for face-on orientations and relatively poor long range order. In this work, we will outline how modest structural changes to the alkyl side chains of a high-performing diketopyrrolopyrrole based polymers can lead to dramatic morphological changes and consequently affects the charge carrier mobility. These findings help to establish new design, respectively processing rules, and show that careful side chain design is absolutely essential in maximising the device performance of conjugated polymers.

L.1.2
09:45
Authors : Nathan J. Cheetham, Jinyi Lin, Xuhua Wang, Yiren Xia, Wei Huang, Donal D.C. Bradley, Paul N. Stavrinou
Affiliations : Department of Physics and Centre for Plastic Electronics, Imperial College London; Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), China; Department of Physics and Centre for Plastic Electronics, Imperial College London; Department of Engineering Science, University of Oxford; Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), China; Departments of Engineering Science and Physics, Division of Mathematics, Physical & Life Sciences, University of Oxford; Department of Engineering Science, University of Oxford & Department of Physics and Centre for Plastic Electronics, Imperial College London.

Resume : Recent work has shown that the polydiarylfluorene PODPF, like the related polyfluorene PFO, appears to form ‘beta-phase’ chain segments with a well-defined, planarised conformation and a characteristic red-shifted vibronic absorption and emission compared to the amorphous phase [1,2]. However, unlike PFO, beta-phase segments in PODPF are formed via high-temperature thermal annealing. As the active material in polymer LEDs, PODPF has shown improved electrical stability and, significantly, the absence of ‘green band’ defect emission frequently seen in electrically driven PFO devices [3]. By varying annealing temperature, we have examined the onset of formation and the fraction of beta-phase segments, as well as beta-phase formation kinetics. From time-resolved studies, we find that the energy transfer rate between amorphous and beta-phases is significantly slower for PODPF compared to PFO. We have also observed the emergence of a crystalline phase, in addition to amorphous and beta-phases. Our studies indicate the competition between crystalline and beta-phase formation may be controlled through a combination of annealing route and film thickness. We will show that the co-existence and varying fraction of the three phases, via processing route, has profound effects on structural, photophysical and device properties. 1. M. Grell et al., Macromolecules 32, 5810 (1999). 2. J. Lin et al., Macromolecules, 47, 1001 (2014). 3. B. Liu et al., ACS Appl. Mater. Interfaces, 8, 21648 (2016).

L.1.3
10:00 Coffee break    
10:30
Authors : Alberto Salleo, Jesus Guardado
Affiliations : Department of Materials Science and Engineering, Stanford University

Resume : Gating conjugated polymers with ionic liquid or ion gels has attracted widespread interest as it raises interesting fundamental questions and opens unexplored avenues for new functionality. An interesting question that has emerged is whether ions penetrate polymers at all voltages, i.e. whether the polymer capacitance is always volumetric or whether ion gating can occur in a field-effect modality. We use synchrotron-based XRD on semicrystalline P3HT films to show that depending on gating conditions (voltage and frequency) ions penetrate the crystallites or remain confined to the amorphous regions of the polymer. Pole figure measurements suggest that even if the ions only penetrate the amorphous regions, they do disrupt crystal alignment. Understanding ion interactions with conjugated polymers can lead to new devices, such as transistors exhibiting neuromorphic behavior opening up new application fields for organic semiconductors.

L.1.4
11:00
Authors : Tobias Rödlmeier, Sebastian Beck, Martin Held, Lars Müller, Christian Müller, Anthony Morfa, Ralph Eckstein, Jana Zaumseil, Annemarie Pucci, Uli Lemmer, Robert Lovrincic, Gerardo Hernandez-Sosa
Affiliations : Karlsruher Institut für Technologie, Lichttechnisches Institut, Engesser Straße 14, 76131 Karlsruhe, Tobias Rödlmeier, Anthony Morfa, Ralph Eckstein, Uli Lemmer, Gerardo Hernandez-Sosa; Universität Heidelberg, Kirchhoff-Institut für Physik, Im Neuenheimer Feld 227, 69120 Heidelberg, Christian Müller, Sebastian Beck, Annemarie Pucci; Universität Heidelberg, Physikalisch-Chemisches Institut, Im Neuenheimer Feld 253, 69120 Heidelberg, Martin Held, Jana Zaumseil; TU Braunschweig, Institut für Hochfrequenztechnik, Bienroder Weg 94, 38106 Braunschweig, Christian Müller, Lars Müller, Robert Lovrincic; InnovationLab GmbH, Speyerer Straße 4, 69115 Heidelberg, Tobias Rödlmeier, Sebstian Beck, Lars Müller, Christian Müller, Anthony Morfa, Ralph Eckstein, Robert Lovrincic, Gerardo Hernandez-Sosa;

Resume : Solution-processed organic semiconductors are expected to enable mass production, high throughput, low-cost, flexible and transparent electronics. Particularly for OFETs, highly ordered, patterned thin films are desirable to obtain high charge-carrier mobilities, low leakage currents and high device performance reproducibility. Recently, highly ordered films have been achieved by coating processes such as solution shearing and slot die coating, resulting in improved OFET performance. However, these techniques lack spatial deposition control compared to printing techniques and would require additional patterning steps for eventual applications. In this work, we present a one-step method for the formation of ordered semiconducting polymer films with highly anisotropic properties through inkjet printing. The functional ink consist of poly(3-hexylthiophene-2,5-diyl) (P3HT) in chlorobenzene plus a crystallization agent that is used as a template to orientate the semiconducting polymer chains and can be removed after deposition through a sublimation process. The deposited film consists of aligned polymer fibers which can be extended over several centimeters and can be deposited in arbitrary shapes independently of the chosen substrate. Characterization by UV-VIS absorption, scanning electron microscopy, X-ray diffraction and polarization dependent infrared spectroscopy demonstrate that the polymer chains extend in the printing direction. Electrolyte gated OFETs were f abricated and show improved performance due to the high degree of fiber alignment.

L.1.5
11:15
Authors : Guillaume Schweicher, Vincent Lemaur, Yoann Olivier, David Beljonne, Jérôme Cornil, Yves H. Geerts
Affiliations : Dr. G. Schweicher; Prof. Y. H. Geerts Laboratoire de Chimie des Polymères Faculté des Sciences Université Libre de Bruxelles (ULB) CP206/1, Boulevard du Triomphe, 1050 Brussels, Belgium E-mail: ygeerts@ulb.ac.be Dr. V. Lemaur; Dr. Y. Olivier; Dr. D. Beljonne; Dr. J. Cornil Laboratory for Chemistry of Novel Materials University of Mons Place du Parc 20, B-7000 Mons, Belgium

Resume : In spite of tremendous progress in molecular design, engineering and processing, only few small molecule organic semiconductors (OSCs) have reached field-effect mobilities higher than 10 cm2/Vs, typically with single-crystal devices. However, charge carrier mobility is a material property and not a molecular one. It is thus of paramount importance to take supramolecular order into consideration at all length scales. As evidenced in recent literature, the best OSCs tend to self-organize into large plate-like single-crystals exhibiting a layer-by-layer herringbone packing motif. Due to their electronic properties and favorable crystalline morphology, BTBT derivatives exhibit record charge carrier mobility above 10 cm2/Vs. We will report on our latest results on the molecular and supramolecular engineering of BTBT semiconductors: design by theory, crystal engineering, quantum-chemical calculations and evaluation of electrical performances in thin-film and single-crystal field-effect transistors. [1] Our work highlights that the molecular packing, driven by the molecular structure, has not only a strong impact on the charge carrier mobility but also on the ionization potential due to changes in the magnitude of electronic delocalization and electronic polarization effects. [1] a) J. Mater. Chem. C 2015, 3, 674 b) Adv. Mater. 2015, 27, 3006 c) Adv. Mater. 2016, 28, 7106 d) J. Mater. Chem. C 2016, 4, 4863 e) ACS Appl. Mater Interfaces 2015, 7, 1868 f) Nat. Commun. 2016, 7, 10736

L.1.6
11:30
Authors : A.Sanchez-Díaz, X. Rodríguez-Martínez, E. Pascual-San José, M. Campoy-Quiles
Affiliations : Nanostructured Materials Department, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Spain

Resume : So far, there is not fundamental limit suggesting that organic photovoltaic materials with extremely high efficiency cannot be synthetized. The issue is how to find such material considering the infinite combinations possible. While theory points towards specific directions, the performance of the synthetized compounds strongly depends on specific properties such as molecular weight, sidechains, solubility or packing tendency, thus one should be talking about material families. One of the major bottlenecks is the time needed to evaluate each compound, let alone a full system family. At lab scale, the fabrication of an organic solar cells takes between days to a few hours (if processed in parallel), while measuring its efficiency takes just minutes. We propose the use of combinatorial processing in the form of samples with controlled gradients in the parameters of interest to make 100 faster the photovoltaic evaluation and optimization of a system. For this, we introduce a fabrication platform that combines blade coating using controllable velocity profiles (thickness gradients), 3D printed microfluidic chip dispensers (composition gradients) and controlled lateral annealing variations (nanostructure gradients). Films exhibiting 2D gradients are then produced which substitute more than 100 conventional (homogeneous) samples. These samples are then analyzed using photocurrent and Raman imaging in order to correlate one to one the device performance and structural information (thickness, composition, nanostructure). In order to verify the strength of the developed technology, we optimize three different systems, namely P3HT:ICBA, PCDTBT:PC70BM and PffBT4T-2OD:PC70BM, obtaining efficiencies approaching 4%, 6% and 10%, respectively, using less than 100 mg of each polymer in the process.

L.1.7
12:00 Lunch    
 
Structure Property Relationships II : Martin Brinkmann, Alberto Salleo, Mariano Campoy-Quiles
14:00
Authors : Renxuan Xie, Wenlin Zhang, Youngmin Lee, Scott Milner, Ralph Colby, Enrique Gomez
Affiliations : The Pennsylvania State University

Resume : Polymers may play an important role in various emerging optoelectronic applications because they can combine the chemical versatility of organic molecules and the flexibility, stretchability and toughness of polymers with dielectric or semiconducting properties. Nevertheless, in order to achieve the full potential of polymers for electronic applications, a clear description of how their structure, morphology, and macroscopic properties are interrelated is needed. We propose that the starting point for understanding conjugated polymers includes a description of chain conformations and phase behavior; unfortunately, further efforts to measure these crucial parameters are needed. Predictions and measurements of the persistence length of various conjugated polymers have significantly refined our intuition of the chain stiffness, and have led to predictions of the nematic coupling parameter and nematic-to-isotropic transitions. We show that the consequence of stiff backbones is a ubiquitous alignment layer near interfaces. Rheological measurements have led to refined estimates of the entanglement molecular weight and the glass transition temperature of both poly(3-alkylthiophenes) and push-pull copolymers, leading to new ways of thinking about how crystallites are interconnected within semicrystalline structures. Exploring mixing between conjugated polymers and small molecules or other polymers has demonstrated tremendous advancements in attaining the needed properties for various optoelectronic devices. Current efforts continue to refine our knowledge of chain conformations and phase behavior and the factors that influence these properties, thereby enabling the prediction of novel optoelectronic materials based on conjugated polymers. For example, more complex architectures, such as fully conjugated block copolymers, provide opportunities to control the microstructure of the active layer of electronic devices and therefore enhance electrical performance.

L.1.1
14:30
Authors : Bernhard Dörling, Antonio Sanchez-Diaz, Oriol Arteaga, Andrea Veciana, M. Isabel Alonso, Mariano Campoy-Quiles
Affiliations : Institute of Materials Science of Barcelona (ICMAB-CSIC), Campus of the UAB, Bellaterra, 08193, Spain; Institute of Materials Science of Barcelona (ICMAB-CSIC), Campus of the UAB, Bellaterra, 08193, Spain; Department of Applied Physics, University of Barcelona, 08028 Barcelona, Spain; Institute of Materials Science of Barcelona (ICMAB-CSIC), Campus of the UAB, Bellaterra, 08193, Spain; Institute of Materials Science of Barcelona (ICMAB-CSIC), Campus of the UAB, Bellaterra, 08193, Spain; Institute of Materials Science of Barcelona (ICMAB-CSIC), Campus of the UAB, Bellaterra, 08193, Spain

Resume : Control over the alignment of conjugated polymers allows to influence their degree of order, which directly affects the phonon and electrical charge transport. Additionally, qualitatively new effects such as polarized absorption or emission can be attained. One possible alignment mechanism is the formation of spherulites. These densely branched, polycrystalline regions of radially extending fibers can be obtained by epitaxial growth of films using the crystallizable solvent additive 1,3,5-trichlorobenzene (TCB). But thus far, control over the site of initial nucleation has not been demonstrated, hampering reproducible sample preparation. In this contribution we present a method to control the number and location of conjugated polymer spherulites during spin- and blade-coating. We show that their nucleation and growth can be influenced by locally controlling solvent evaporation rate. This allows to prepare polythiophene films containing single, cm-sized spherulites at a defined position, as well as ordered arrays of spherulites. By capping them with PCBM, these structures can be used in bilayer OPV devices. As revealed by imaging polarimetry measurements, their optical response strongly depends on polarization, which makes them particularly well suited for applications as polarization sensitive photodetectors. Importantly, the presented method is very general, and can be applied to many other polymers (e.g. PCPDTBT, PFO, PFBT) and crystallizable solvents (e.g. naphthalene).

L.1.2
14:45
Authors : Thomas Schmaltz, Euan G. P. Smith, Holger Frauenrath
Affiliations : Ecole Polytechnique Federale de Lausanne (EPFL) - Institute of Materials (IMX) Laboratory of Macromolecular and Organic Materials (LMOM) Address: EPFL- STI - IMX – LMOM, Station 12 1015 Lausanne, Switzerland E-mail: thomas.schmaltz@epfl.ch

Resume : Current challenges in the field of organic semiconductor-based electronics include the realization of efficient large-area patterning and the ability to control the orientation of the semiconductors.[1] Both can be achieved by a wetting/dewetting-based deposition approach on substrates with micropatterns of self-assembled monolayers (SAMs).[2–4] We report on the aligned and region-selective deposition of organic semiconductor nanowires on SAM-patterned substrates, for transistor applications. Substrates with hydrophilic/fluorinated SAM-micropatterns were prepared to provide wettable areas in a non-wettable matrix. Nanowires of dioctyl perylenebisimide and hexathiapentacene were grown in solution, dispersed into non-solvents, and deposited on these substrates. Dewetting occured in the fluorinated areas leading to a region-selective deposition of the nanowires in the hydrophilic areas. Beyond the mere patterning, an alignment of the nanowires was achieved by adjusting the dimensions of the wettable regions to be smaller than the length of the nanowires. This approach allows for the first time to efficiently pattern and align organic nanowires at the same time and thus to incorporate them efficiently into transistor devices. References [1] Kang, B.; et al. ACS Appl. Mater. Interfaces 2013, 5, 2302 [2] Schmaltz, T.; et al. Adv. Mater. 2017, DOI:10.1002/adma.201605286 [3] Giri, G.; et al. Adv. Mater. 2014, 26, 487 [4] Park, S.; et al. Adv. Mater. 2015, 27, 2656

L.1.3
15:00
Authors : L. Biniek,1 N. Genevaz,1 P. Chavez,2 S. Fall,3 M. Brinkmann,1 N. Leclerc,2 P. Lévêque3
Affiliations : (1) Université de Strasbourg, CNRS, ICS UPR 22, F-67000 Strasbourg, France (2) Université de Strasbourg, CNRS, ICPEES UMR 7515, F-67000 Strasbourg, France (3) Université de Strasbourg, CNRS, ENGEES, INSA, ICUBE UMR 7357, F-67000 Strasbourg, France

Resume : Diketopyrrolopyrrole (DPP) based semiconductors have been the center of intense research efforts in the last decade. This is mainly due to the ease of functionalization of the DPP core that allows tuning the photophysical and electronic properties to a large extent. DPP based materials display some of the highest charge carrier mobilities due to their strong aggregation properties. Herein we focus on two DPP-co-thienothiophene derivatives that differ in their side chains (n-hexyl vs 2-ethylhexyl) grafted on the DPP core. The single crystal structures of both compounds were determined. Electron diffraction confirms that only the single crystal structure of both derivatives is formed in solution casted and evaporated films. For the latter films, the side chain impacts strongly the charge transport properties in OFETs: the 2-ethylhexyl derivative shows hole mobility of 0.3 cm²/V.s, i.e. two order of magnitude larger than for the n-hexyl analogue. Films of both DPP analogues grown on oriented PTFE substrates are highly dichroic: their colour turns from orange to blue-violet when the light polarization is turned from 0° to 90° (resp. PTFE chain direction). Polarized UV-Vis spectroscopy shows that he UV-vis absorption of the DPP semiconductors results from two sets of absorption bands with orthogonal polarizations that are centered around 400 and 650 nm. These results are rationalized in terms of the dipolar transition orientation in the crystal structure of the two derivatives.

L.1.4
15:15
Authors : Younggul Song; Jingon Jang; Daekyoung Yoo; Youngrok Kim; Woocheol Lee; Takhee Lee;
Affiliations : Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea

Resume : Many studies on organic memory have focused on scientific and technical issues of the materials, device structures, switching mechanisms, and performance enhancement. However, the strongly disordered and complex structures hindered the elaborated understanding of the mechanism of organic resistive memory. In particular, the charge conduction in organic nanocomposite memory materials is greatly influenced by the charge traps. In addition, bistable switching can occur from the accumulation of trapped charges, which affect the injection of charges into the organic material and often produce a negative differential resistance (NDR) in the I-V characteristics. Modulating the applied voltage in NDR, the multi-stable current levels of organic memory can be achieved. Here, we studied the noise characteristics of nanocomposite for the organic memory material [1,2]. The current fluctuations were investigated over a bias range that covers various intermediate states and NDR in organic nanocomposite unipolar resistive memory devices. From the analysis of the 1/f^γ type noises, scaling behavior between the relative power spectral density and resistance was observed, indicating a percolating behavior. Furthermore, the multi-stable behavior of our organic resistive memory is attributed to the current pathway reduction and fluctuation in NDR. Temperature and bias dependent telegraphic noise at the NDR region suggested that the current pathway fluctuation is originated from the charge carrier trapping/detrapping at the deep trap levels in organic nanocomposite material. This study will provide a better understanding of the resistive memory devices and promote the development of more practical and sophisticated resistive memory devices [1] Y. Song, H. Jeong, J. Jang, T.-Y. Kim, D. Yoo, Y. Kim, H. Jeong, and T. Lee, ACS Nano 9, 7697 (2015) [2] Y. Song, H. Jeong, S. Chung, G. H. Ahn, T.-Y. Kim, J. Jang, D. Yoo, H. Jeong, A. Javey & T. Lee, Scientific Reports 6, 33967 (2016)

L.1.5
15:30 Coffee    
16:00
Authors : Enrico Da Como*
Affiliations : Department of Physics and Centre for Photonics and Photonic Materials, University of Bath, Bath, BA2 7AY, UK

Resume : Among the distinctive features of organic semiconductors there is the strong coupling between charge carriers and phonons. While this has been recognized as a fundamental aspect in improving carrier mobility in transistor devices or exciton dynamics in organic photovoltaics[1], the description and the measurement of the coupling between electrons and molecular vibrations is often based on qualitative observations. In this talk I will discuss our efforts in describing quantitatively some of the most spectacular effects originating from phonons and molecular vibrations in organic semiconductors. The first part of the talk will deal with donor-acceptor copolymers and the appearance of vibrational modes with giant intensity [2], i.e. comparable to that of electronic or polaronic transitions. The results are rationalized by ab-initio quantum chemical calculations showing the importance of coupling between vibrations and polarons. In the second part I will describe the role of intermolecular phonons in the phase stability of coronene and its recently discovered polymorphism[3]. References [1] A. Troisi, Chem. Soc. Rev. 40, 2347 (2011). [2] D. Di Nuzzo, C. Fontanesi, R. Jones, S. Allard, I. Dumsch, U. Scherf, E. von Hauff, S. Schumacher, and E. Da Como, Nature Comm. 6, 8, 6460 (2015). [3] J. Potticary et al., Nature Comm. 7 (2016).

L.1.6
16:30
Authors : Francesca Leonardi, Qiaoming Zhang, Stefano Casalini, Inés Temiño, Sergi Galindo, Marta Mas-Torrent
Affiliations : Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) and CIBER-BBN, Campus de la UAB, 08193, Bellaterra, Spain

Resume : During the last decades, organic electronics has impressively grown due to breakthroughs in material synthesis and processing. Ultra-high vacuum sublimation and spin-coating deposition are often the main choices for depositing small molecules organic semiconductors (OSCs) but, they still remain quite far from a real industrial upscaling. Our strategy exploits the combination of blended materials together with bar-assisted meniscus shearing (BAMS) technique. The active material is prepared by blending an insulating polymer (e.g. polystyrene) with a small molecule organic semiconductor (e.g. TIPS-pentacene, DB-TTF, diF-TES-ADT, etc.). Furthermore, BAMS permits to deposit in one-step the blended material reaching higher electrical performances than the single semiconducting component [1]. This deposition approach features the following pros: i) high-crystalline domains, ii) smooth and compact surface and iii) self-encapsulation layer resulting in a robust device. The electrical performances of our devices were successfully tested in dry (e.g. OFET) and wet (EGOFET) state [2][3]. Our devices reach excellent performances and exceptional water stability, which make them suitable candidates in the field of printed electronics. [1] del Pozo F. et al., Adv Mater., 2016, 26, 2379-2386. [2] I. Temiño et al., Adv. Mater. Technol., 2016, 1, 1600090. [3] F. Leonardi et al., Adv. Mater. 2016, 28, 10311.

L.1.7
16:45
Authors : Giulio Pipan1, Marco Bogar1, Andrea Ciavatti2, Laura Basiricò2, Tobias Cramer2, Beatrice Fraboni2, Alessandro Fraleoni Morgera1,3,4
Affiliations : 1Dept. of Engineering and Architecture, University of Trieste, Italy 2 Department of Physics, University of Bologna, Italy 3 CNR-NANO S3, Via Campi 213/A, Modena, Italy 4 Sincrotrone Trieste S.C.p.A., Italy

Resume : Organic semiconducting single crystals (OSSCs) have been studied during the last years because of their good electrical properties, which allow to fabricate transistors or direct x-ray detectors. Inkjet printing techniques can be used to print solutions from which OSSCs are grown. However, being able to grow OSSCs onto irregular substrates is not straightforward because of the presence of a wide number of possible nucleation points, originating usually polycrystalline films. Here we report on the production of TIPS-Pentacene single crystals via inkjet printing onto interdigitated gold electrodes on flexible PEN. In particular, a chemical confinement-based technique has been developed in order to precisely define the crystal growth position, avoiding unwanted drop spreading and achieving in this way high quality single crystals with good electron injection properties with respect to the underlying electrodes. In particular, well performing UV-VIS photodetectors with responsivity up to 70A/W at 50V and S/N up to 10E4 and x-ray detectors up to 7,5nC/Gy@1V are reported, demonstrating a good electrical contact between the printed crystals and the underlying electrodes.

L.1.8
17:00
Authors : Ram Kumar C. B., Samuel J. Ippolito, Suresh K. Bhargava, Selvakannan R. Periasamy, Ramanuj Narayan, and Pratyay Basak
Affiliations : Ram Kumar C. B; Ramanuj Narayan - Polymers and Functional Materials Division; RMIT-IICT Joint Research Centre, CSIR-Indian Institute of Chemical Technology (CSIR-IICT) Pratyay Basak- Nanomaterials Laboratory, Inorganic and Physical Chemistry Division CSIR-Indian Institute of Chemical Technology (CSIR-IICT) Ram Kumar C.B; Samuel J. Ippolito - School of Electrical and Computer Engineering and Centre for Advanced Materials and Industrial Chemistry (CAMIC) Royal Melbourne Institute of Technology (RMIT) 124 La Trobe St, Melbourne VIC 3000, Australia. Suresh K. Bhargava; Selvakannan R. Periasamy - School of Applied Sciences and Centre for Advanced Materials and Industrial Chemistry (CAMIC); Royal Melbourne Institute of Technology (RMIT), 124 La Trobe St, Melbourne VIC 3000, Australia.

Resume : In this contribution, we have directed our efforts to provide significant insights on the structure-property-device performance of fused 1,4 dihydro pyrrolo [3,2, -b] pyrroles (DHPPs) as resistive switching elements for the first time. To this end, we have investigated the impact of structural tuning on the optical, electrochemical and electrical properties governing the device performance. The molecules exhibit interesting optical properties with an unprecedented λmax as high as 550nm and amphoteric redox behavior. It is noteworthy to mention that DHPPs are not known to exhibit dual redox characteristics. Characterization by SEM, AFM and XRD provide significant insights into the self-assembly, surface topography and crystalline orientation of the molecules in thin films directed by preferred intermolecular interactions. The molecules exhibit resistive switching properties when embedded in a typical two terminal MIMs (Metal-Insulator-Metal) configuration and are well suited to memory storage applications. The performance varied from a Write-Once-Read-Many times (WORM) behavior, FLASH memory with an excellent retention time and endurance tested for 500 write-read-erase cycles to a volatile re-programmable D-RAM behavior with ON/OFF ratio of ~10^4, 10^1 and 10^6 respectively. The contrasting memory behavior of the molecules is ascribed to the altered charge trap dynamics and Inter/Intra molecular charge transfer stabilization in the thin film as a function of structural tuning.

L.1.9
17:15
Authors : Alise Virbule, Johannes Lischner, Jenny Nelson
Affiliations : Centre for Doctoral Training in Theory and Simulation of Materials, Department of Physics, Imperial College London

Resume : Organic semiconductors have shown great promise as candidate materials for solar cells, whose efficiency depend on many properties, including the absorption strength within the visible spectrum. Recent studies suggest that the molecular organisation in a polymer film can have a great effect on the absorption strength without changing the material’s chemical composition. I have applied density functional theory and its time-dependent formalism to model the optical properties of oligomers and study their dependence on chain length and conformation. Additionally, these calculations can be used as a starting point to develop a coarse-grained model for the optical absorption strength. Current work involves applying and verifying an exciton model that uses Wannier functions as its basis to different model systems, including polythiophene, polyphenylene and polyphenylene-vinylene. The long-term goal of this project is predicting spatially averaged optical properties of a material using the knowledge of the excited states on an atomic scale and a given molecular organisation, as the understanding of the macroscopic absorption properties of known compounds can be used to aid the design of new organic materials exhibiting high optical absorption.

L.1.11
 
Poster Session I : Mario Caironi
17:30
Authors : Aye Myint Moh1, Kimihiro Sasaki1, Seiji Watase2, Tsutomu Shinagawa2, Masanobu Izaki1
Affiliations : 1 Graduate School of Engineering, Toyohashi University of Technology; 2 Osaka Municipal Technical Research Institute

Resume : Organic light-emitting diode (OLED) and organic photovoltaic devices (OPV) are attracted increasing attentions to saving the energy and to reduce carbon dioxide emission in electrical and electronics applications. The performance of the devices strongly depends on the electrical characteristics of organic semiconductors, and the low carrier mobility limits the application of organic semiconductors. Since the carrier existed in organic semiconductors are scattered by the ionized impurity and defects of the molecular arrangement, it is needed to control the molecular arrangement including the preferred orientation and morphology. In this study, we prepared 5-100-nm-thick layer of organic semiconductor, 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8-BTBT), on a single crystal <0001>-aluminum oxide (Sapphire) by a thermal evaporation technique and investing the effects of the preparation temperature and thickness on the preferred orientation and morphology estimated with X-ray diffraction techniques and atomic force microscopic (AFM) observation. The C8-BTBT layers showed diffracted X-ray peaks assigned as (00n), (n = 1, 2,…) on the X-ray diffraction pattern recorded by theta/2theta scanning technique, indicating the formation of (001)-out-of-plane orientation irrespective of the preparation temperature and thickness. And, only diffraction spots could be observed on the X-ray diffraction image taken with an imaging plate, suggesting the formation of in-plane orientation in addition to the out-of-plane orientation, although it was impossible to decide the crystal index, regardless of the preparation temperature and thickness. The morphology changed depending on the thickness, and the dimension changed depending on the preparation temperature. The step and terrace were observed clearly on the surface of annealed C-sapphire substrate. Plate-like and round shape islands with a flat top surface were formed over the step-and-terrace structure formation of C-sapphire at the initial growth stage of the C8-BTBT layer. The plate-like and round shape islands grew in the direction parallel to the substrate surface and then formed the continuous layer by the coalescence of isolated plate-like and round shape islands. The height of the continuous layer changed depending on the preparation temperature. And, the growth mode was transferred from the layer-by-layer growth to tridimensional growth mode, since the isolated islands stacked on the continuous layer and the surface irregularity increased with increase in the thickness.

L.1.1
17:30
Authors : L. Raimondo1, S. Trabattoni1, M. Moret1, N. Masciocchi2, M. Masino3, A. Sassella1
Affiliations : 1 Dept of Materials Science, University of Milano Bicocca, via Cozzi 55, 20125 Milano (Italy); 2 Dept of Science and High Technology and ToScaLab, University of Insubria, via Valleggio 11, 22100 Como (Italy); 3 Dept of Chemistry, University of Parma, parco Area delle Scienze 17/a, 43124 Parma (Italy)

Resume : Rubrene (RUB) has been a benchmark organic semiconductor since orthorhombic RUB single crystals were demonstrated to possess relevant properties in terms of charge carrier mobility and exciton diffusion length. This has triggered great research efforts not only on RUB itself, but, in particular, on the growth and study of crystalline RUB thin films, the most suitable choice for applications of semiconductors in electronic devices. At the same time, their possible oxidation under ambient conditions has been investigated widely, because oxidation is known to strongly affect the semiconductor properties of RUB single crystals. Nonetheless, in the literature contradictory results are often reported. Here, the study of the formation and properties of the interface between RUB and its oxide is carried out, considering thin crystalline films grown by organic molecular beam epitaxy. Experimental studies of the optical properties of as-grown films and of similar films stored in air for months show the evolution of both optical absorption and Raman response. In particular, the comparison between the Raman spectra of stored films and those of a crystalline powder of RUB peroxide (RUBox) of known crystal structure, grown on purpose, permits the attribution to RUBox of the observed optical response of films stored in ambient conditions. In addition, the matching of the crystal structures of RUB and RUBox suggests the oxide growth to be driven by organic epitaxy with the original RUB thin films.

L.1.2
17:30
Authors : M. Ruscello, S. Stolz, F. Ulrich, E. Mankel, A. Briseno, G. Hernandez-Sosa
Affiliations : InnovationLab, Speyerer Strasse 4, 69115 Heidelberg, Germany (M. Ruscello; S. Stolz, F. Ulrich; E. Mankel; G. Hernandez-Sosa) Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany (M. Ruscello; S. Stolz; G. Hernandez-Sosa) Technische Universität Darmstadt, Materials Science Department, Surface Science Division, Jovanka-Bontschits-Straße 2, 64287 Darmstadt, Germany (F.Ulrich; E. Mankel) Department of Polymer Science and Engineering, University of Massachusetts, 120 Governors Drive, Amherst, Massachusetts 01003, United States (A. Briseno)

Resume : Reducing charge injection/extraction barriers is a crucial issue for obtaining high-performance organic optoelectronic devices.(1) Particularly in solution-processed OLEDs, a large effort is currently made to substitute commonly used electron-injection layers based on low work-function alkaline earth metals or alkali metal halides.(2) These materials need to be evaporated, have poor chemical stability in ambient conditions and are therefore not compatible with printing/coating techniques. Poly(sulfobetaine methacrylate) (PSBMA) is an air stable and solution-processable zwitterionic polymer. Due to its strong molecular dipole, which lowers the work-function of electrodes, it has been utilized as an interlayer in highly efficient inverted organic solar cells.(3) In this work, we employ it for the first time in regular and inverted polymer OLEDs as a work-function modifier for Al and ZnO cathodes, respectively. PSBMA thin films are characterized by Atomic Force Microscopy, Kelvin Probe and X-ray Photoelectron Spectroscopy, revealing that the polymer forms a thin, smooth film, yielding a work function reduction of up to ~1 eV. For both architectures, PSBMA significantly improves the OLED performance when compared to reference devices without it. Particularly in the inverted stack, PSBMA remarkably improves the surface morphology of the ZnO film and passivates its trap states, leading to a more stable and better performing device. 1) N. Koch, ChemPhysChem, 2007, 8, 1438−1455. 2) T. Chiba et al., J. Mater. Chem. C, 2015, 44, 11567−11576 3) H. Lee et al., J. Am. Chem. Soc., 2015, 137, 540−549

L.1.3
17:30
Authors : Marc Courté (a), Sandeep G. Surya (b), Ramesh Thamankar (c), Chao Shen (a), V. Ramgopal Rao (b), Subodh G. Mhaisalkar (d,e), Denis Fichou (a,f,g)
Affiliations : a. School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore; b. Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400 076, India; c. School of Engineering and Technology, CMR University, Bangalore 560043, India; d. School of Material Science and Engineering, Nanyang Technological University, 639798, Singapore; e. Energy Research Institute@NTU (ERI@N), Nanyang Technological University, 637141, Singapore; f. CNRS, UMR 8232, Institut Parisien de Chimie Moléculaire, F-75005, Paris, France; g. Sorbonne Universités, UPMC Univ Paris 06, UMR 8232, Institut Parisien de Chimie Moléculaire, F-75005, Paris, France;

Resume : With the miniaturization of transistor to nanoscale, silicon based semiconductor devices become less stable and so less efficient. A large variety of new materials using electrical bistability like ferroelectric material have been study in alternative. Recently organic memory devices have received intensive interest due to his low cost fabrication and its electrical properties could be easily tune by chemical synthesis. Moreover the possibility to store information through molecule could overcome the limitation of silicon based microelectronics. Here, the charge transport properties of 2,2’,6,6’-tetraphenyldipyranylidene, a large planar quinoïdal pi-conjugated heterocycle, are investigated in field-effect transistor (FET) configuration and by conductive atomic force microscopy (c-AFM). The FET properties show a clear p-type behavior with a hole mobility up to 2×10^-2 cm2/V.s and on/off ratio of 10^4. The transfer characteristics Id/Vg present a clear hysteresis typical of a resistive memory effect. This memory effect is again observed by means of c-AFM in lateral mode using a nearby gold top-contact as the counter-electrode. Repeated “write-read-erase-read” cycles performed at low frequency reveal a non-volatile memory effect in the form of high-resistance and low-resistance states. M. Courté; S. G. Surya; R. Thamankar; C. Shen; V. R. Rao; S. G. Mhaisalkar; D. Fichou, RSC Advances, 2016, DOI: 10.1039/ C6RA26876E

L.1.4
17:30
Authors : Ilaria Meazzini, Jonathan M. Behrendt, Michael L. Turner, Rachel C. Evans
Affiliations : I. Meazzini; R. C. Evans School of Chemistry and CRANN, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland. J. M. Behrendt; M. L. Turner School of Chemistry, University of Manchester, Oxford Road, M13 9PL Manchester, United Kingdom.

Resume : Poly(fluorenes) (PFs) are a promising class of materials for application in polymer light-emitting diodes. PFs present a rich phase morphology which includes an amorphous α-phase and a π-stacked β-phase. β-phase formation has been linked to improved optoelectronic properties, such as higher charge carrier mobility, amplified spontaneous emission and low lasing threshold limit. Here, we report the targeted formation of the β-phase through covalent grafting of a hydroxyl-functionalised PF to poly(oxyalkylene)/siloxane organic-inorganic hybrids (ureasils) using sol-gel chemistry. Steady-state fluorescence studies reveal that in a good solvent the PF adopts the disordered α-phase with a typical structured emission band from 400 to 500 nm and an excitation band at 380 nm. However, upon incorporation into the solid-state, local confinement from the rigid siliceous network induces a conformational change leading to the β-phase formation, which is confirmed by its unique optical fingerprint: a red-shift in the emission maximum and the formation of a new peak at 435 nm in the excitation spectrum. Structural characterisation by FTIR and 29Si NMR spectroscopies shows that while grafting of the PF chains occurs at the silica domains, is the degree of branching of the organic framework of the hybrid that governs the packing and organisation of the PF chains. These results represent a promising step towards the design of new PF-ureasil materials with tailored optical properties.

L.1.5
17:30
Authors : A. Zubarev 1 2, Ana-M Iordache 1, A. Balan 1, A. Cucu 1, S. M. Iordache 1, M. Cuzminschi 1; I. Stamatin 1
Affiliations : 1 University of Bucharest, Bucharest, Romania 2 INFLPR, Magurele, Romania

Resume : In this work we study synthesis of different carbon nanostructure with various using of arc discharge method in various liquids. For the experiment was executed special installation composed by a current source and two carbon electrodes inside a site with selected liquid. The discharge properties were studied by recording of voltage, current oscillations and their spectra characteristics. The experiment was repeated with different liquids media: water, benzene, benzene-toluene mixture and xylene. The nanoparticles obtained during the experiment were separated by liquid medium centrifugation and by filtering of residual gases. The crystalline structure of obtained substances was analysed using Raman spectroscopy, FTIR and X-ray diffraction. The particles dimensions and zeta-potential were determined by DLS. For the investigation of nanoparticles microstructure was used high resolution tunneling electron microscopy. Effectuated tests prove synthesis of graphene for arc discharge benzene and xylene medium and creation of an instable organic compound in case of benzene toluene mixture. The experimental results were compared with modeling by Density functional method. This work was partially supported by the Romanian Ministry of National Education by the contract PN 16 47 0101 with UEFISCDI

L.1.6
17:30
Authors : Gil Sheleg,Nir Tessler
Affiliations : Technion Institute of Technology Electrical Engineering department, Israel

Resume : Field effect transistors (FETs) are the fundamental building block for electronic circuits and driver electronics. In the context of amorphous materials based transistors the challenge is in applications requiring current-driving where high charge and current densities activates degradation mechanisms. To reduce the burden on the material synthesis we, and others, have developed the patterned source vertical field effect transistor. In this type of transistor, the switching is of the injection properties of the source electrode making it difficult to obtain characteristics that are similar to those of standard FETs. We report thin layer vertical FETs based on PTCDI, ZnO, and a-Si. We correlate 2D device simulations with device fabrication and characterization. The study comes to understand how all the intricate mechanisms of the vertical transistor structure plays a role in the overall device performance and characterization. By making the source electrode a stack of metals and insulators we can control the switching characteristics of the transistor and decouple it. Moreover, we found that it is possible to design the source such that the drain has no effect on the injection properties enabling flat saturation regime also when the channel material is doped (as ZnO often is). In this presentation we will discuss the design criteria, using the 2D device simulations, and demonstrate the operation of such structures implemented using organic molecule (PTCDI), ZnO, and a-Si.

L.1.7
17:30
Authors : Andreas H. Hubmann, Julia Rittich, Sebastian Mäder, Matthias Wuttig, Andreas Klein
Affiliations : Technische Universität Darmstadt, Rheinisch-Westfälische Technische Hochschule Aachen

Resume : As ITO is a standard electrode material for organic electronics and considering the variety of organic semiconductors, the ability of tuning its work function to achieve best possible band alignment is of great interest. The work function of In2O3 is strongly affected by its surface orientation and atomic composition which can be influenced by the surface treatment and growth conditions. Further, it is known that the work function of metals and oxides can be modified by the deposition of organic molecules exhibiting a dipole moment. Epitaxial and polycrystalline ITO films were grown by reactive magnetron sputtering. Organic molecules were thermally evaporated. The influence of surface orientation and surface treatment onto surface potentials and the contribution of the organic molecules was investigated by in-situ XPS and UPS measurements. The epitaxial ITO films do not show the expected variation in work function, which is attributed to Sn surface segregation and faceting. Different surface treatments, however, allow adjusting the ITO work function between 6.0 eV and 4.1 eV. This value can be decreased down to 3.0 eV by adsorption of the organic molecules, which show a limited growth behavior. The induced work function reduction of approximately 1.3 eV is found to be rather independent on the ITO surface orientation and treatment.

L.1.8
17:30
Authors : E. Steveler (1), T. Han (1), Y. El Khoury (2), I. Bulut (3), J. Léonard (2), S. Haacke (2), T. Heiser (1), N. Leclerc (3)
Affiliations : (1) Université de Strasbourg, CNRS, ENGEES, INSA, ICube UMR 7357, F-67000 Strasbourg, France; (2) Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France; (3) Université de Strasbourg, CNRS, ICPEES UMR 7515, F-67000 Strasbourg, France

Resume : Planar conjugated small molecules are attractive materials for photovoltaic devices.(a) In thin films, their exciton and charge carrier dynamics, which are crucial to device operation, are controlled by intermolecular interactions and depend in a non-trivial way on possible molecular crystalline or semi-crystalline phases. We have studied exciton generation and recombination in thin films of a thiophene-thienopyrroledione-thiophene derivative functionalized with two planar triazatruxene units. We have previously used molecules with a similar structure as efficient electron-donor in bulk heterojunctions.(b) These molecules have been found to adopt various molecular packings, changing from a nematic-columnar mesophase to a crystalline phase, depending on the thin film deposition and post-deposition annealing treatments. Randomly oriented, hundreds of nanometers long crystalline needles are formed upon cold crystallization. In this report, we present UV-visible absorption and time-resolved photoluminescence experiments done on both phases. The results reveal a significant increase in exciton lifetime with structural order as well as the existence of two distinctive radiative recombination pathways, suggesting the contribution of different molecular environments. The relatively high exciton lifetime found is consistent with the good performances obtained previously in solar cells. (a) Leliège et al. Chem. Eur. J. 2013, 19, 9948 (b) Bulut et al. J. Mater. Chem. C 2016, 4, 4296

L.1.9
17:30
Authors : SunJoong Park, Kyungmok Kim, and Duk Young Jeon
Affiliations : Dept. of Materials Science and Engineering, Korea Advanced Institute of Science and Technology

Resume : For solution-processable organic light emitting diodes (OLEDs), many researchers have been studied on electron injection layer (EIL) by using ZnO nanoparticles (NPs). Because ZnO NP has appropriate properties; it has deep valence band (~7.8 eV), large bandgap (~3.4eV), high intrinsic electron mobility (~ 200 cm2V-1S-1), and it can be deposited via solution process. However, the ZnO NPs have two weaknesses. First, since ZnO NPs have many defects on the surface, it results in an exciton quenching, and it have an effect on OLED performance. Second, due to the large barrier between the conduction band (CB) of ZnO NPs and the lowest unoccupied molecular orbital (LUMO) of emissive layer, electron cannot be injected efficiently. Herein, we suggest introduction of hybridization between ZnO NPs and Polyethylenimine (PEI:ZnO hybrid layer), called organic/inorganic hybrid materials. PEI passivated the defect of ZnO NPs and increased the efficiency by reducing the energy barrier through dipole effect. And we compare conjugated polyelectrolyte(CPE):ZnO hybrid layer. It is reported that CPE:ZnO hybrid materials also passivate the defect and increase efficiency. PEI passivates ZnO defect, injects electrons efficiently, and blocks holes and exciton quenching. The device with PEI hybridized ZnO nanoparticles shows the highest device efficiency and good stability.

L.1.10
17:30
Authors : Ikue Hirata, Giorgio dell’Erba, Andrea Periont, Mario Caironi
Affiliations : Istituto Italiano di Tecnologia

Resume : Printing is a key factor for the electronics fabrication, yet one of the major problems is the high driving voltage of the devices due to the polymer gate dielectrics. To solve this, we used materials with higher permittance such as ceramic nanoparticles to increase the capacitance of the gate dielectrics, with the processes that is compatible printing. We sandwiched TiOx layer formed by sol-gel method with poly (methyl methacrylate) (PMMA) layers to lower the driving voltage and to maintain the semiconductor-gate dielectrics interface at the same time. On glass substrate, we first printed PEDOT:PSS source and drain electrodes with channel length of 80 μm and width of 1000 μm, then an n-type organic semiconductor of poly{[N,N’-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5’-(2,2’-bithiophene)} using an inkjet printer. Then a 200 nm-thick hybrid dielectric composed of PMMA/TiOx/PMMA was formed by spincoating. Finally PEDOT:PSS gate electrode was formed by inkjet printing. The PMMA/TiOx/PMMA capacitor showed an areal capacitance of 28 nF/cm2 and the transistors could be operated under 20 V with a mobility of 0.06 cm2/Vs. To further decrease the driving voltage and to reduce the leakage current, the bottom PMMA layer was replaced by a mixture of cross-linked PMMA and poly (4-vinylphenol) (PVPh), keeping the same total thickness. The breakdown voltage of the capacitor was increased from 22 V to more than 100 V and the leakage current was suppressed from 600 nA/cm2 to 14 nA/cm2.

L.1.11
17:30
Authors : A. Artemenko1, M. Marton2, K. Hruška1, A. Kromka1
Affiliations : 1 Institute of Physics of CAS, Cukrovarnická 10,162 00, Prague 6, Czech Republic; 2 FEI STU, Ilkovičova 3, 812 19, Bratislava, Slovakia

Resume : Carbon-based materials such as nanocrystalline diamond (NCD) and diamond-like carbon (DLC) films exhibit extraordinary properties suitable for biomedical applications which require prolonged surfaces stability towards aging in the open air. This work focuses on aging of H-, O-, NH2-terminated NCD and DLC films studied by X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) measurements and scanning electron microscope (SEM). The initial surface terminations were done by radio frequency plasma in appropriate gas mixtures (hydrogen, oxygen, ammonia). The XPS and WCA measurements of O-terminated NCD and DLC films showed significant increase of oxygen content (up to 8 at.%). The WCA for both oxidized samples was <10°. The hydrogen termination caused decline of oxygen concentration (~3 at.%) and increase of water contact angles (>70°) for both materials. Aged hydrogenated diamond and DLC films demonstrated a strong hydrophobic character and constant oxygen concentration (~4 at.%) whereas oxidized samples had degraded. The chemical composition changes will be discussed. The obtained XPS data revealed twice higher amount (~10 at.%) of nitrogen bonded on DLC films rather than on diamond after NH 3 plasma treatment. The WCA of aged aminated NCD and DLC film was >65° and <50°, respectively. Although nitrogen content of both aged samples slightly decreased the concentration of C-N/C=N bonds is sufficient for bioapplications. This work was supported by the project GACR 15-01687S.

L.1.12
17:30
Authors : Tuğbahan Yılmaz Alıç1,2,3, Mamatimin Abbas3, Mahmut Kuş1,4, Mustafa Can5
Affiliations : 1Selcuk University, Advanced Technology Research and Application Center, Konya/TURKEY 2Selcuk University, Departmant of Physics, Konya/TURKEY 3Université de Bordeaux, Laboratoire IMS, UMR CNRS 5218, ENSCBP, 16 Avenue Pey Berland, 33607 Pessac Cedex, FRANCE 4Selcuk University, Departmant of Chemical Engineering, Konya/TURKEY 5Katip Celebi University, Departmant of Engineering Sciences, İzmir/TURKEY

Resume : Organic semiconductors have attracted remarkable interest in the field of electronics due to good mechanical stability, interesting properties in the solid state, such as electrical, optical, photoelectrical/magnetic properties and the advantage of large area fabrication, solution processability and low temperature deposition. Organic Field Effect Transistors (OFETs) are essential components for electronic circuits. In an OFET, besides the semiconducting active layer, other components such as electrodes and dielectric insulators play significant role in device performance. Self-assembly is one of the most effective and versatile strategy for surface functionalization. Different Self-Assembled Monolayers (SAMs), such as alkylsilanes and alkylphosphonic acids [1-3], have been used to passivate the dielectric surfaces in OFETs, which showed strong effect on device performances. In this study, we investigated the effect of boronic acid based molecules on the performance of OFETs as an initial effort. Clear enhancement in the performance has been observed when the SiO2 surface was treated with these molecules, which is evidenced by smaller hysteresis, higher mobility, higher current on/off ratio and smaller subthreshold slope. Contact angle, Atomic Force Microscopy(AFM) and Scanning Electron Microscopy(SEM) have been applied to understand the mechanism behind such an effect. Our results opens up an area for a new class of functionalnized molecules based on boronic acid to be applied in organic electronics. [1] D. J. Gundlach et al.,. Nat. Mater. 7, 216–21, 2008. [2] L. Bürgi, T. J. Richards, R. H. Friend, H. Sirringhaus, J. Appl. Phys. 94, 6129, 2003. [3] S. Casalini, C. A. Bortolotti, F. Leonardi and F. Biscarini, Chem. Soc. Rev. 2017.

L.1.13
17:30
Authors : Logesh Karunakaran, Soumya Dutta
Affiliations : Department of Electrical Engineering, Indian Institute of Technology Madras, Chennai 600036, India

Resume : Over last two decades, a considerable amount of efforts has been implemented on the improvement of OFETs due to their tremendous potential in circuit application, sensing, photo-detection, light emission etc. together with availing the advantages such as low temperature and low cost processing, mechanical flexibility and excellent optical properties. However, from circuit application standpoint, there exists a huge gap between devices level to integrated circuits. These devices have certain issues like reliability, reproducibility, degradation, hysteresis in current-voltage characteristics, which need to be addressed before successful implementation. In this presentation, we will discuss the adaptation of microelectronic technology to improve reliability by realizing an array of identical OFETs, consisting of an isolated gate with patterned bottom source/drain contact on polymer dielectric material. In addition, we will discuss the role of drain-source contact in deciding the hysteresis in transfer characteristics of Poly (3-hexylthiophene) (P3HT) based transistors. The bottom-gate-bottom-contact transistor with different contact metals, channel length and channel width are studied thoroughly to understand the correlation between the contact effect and hysteresis in transfer characteristics. This study enables us to design better transistors with minimum hysteresis toward circuit application.

L.1.15
17:30
Authors : Sol Yee Im†, Junsoo Kim†, Jung Yoon Kwon, Jaewoo Lee, Jong Pil Im, Seung-Min Lee, Seung Eon Moon*
Affiliations : ICT Materials Research Group, Electronics and Telecommunications Research Institute, Daejeon 34129, Republic of Korea † These authors contributed equally to this work.

Resume : Recently, soft and flexible pressure sensors have been widely researched to use as a artificial tactile sensor by utilizing flexibla and conductive materials such as carbon nanomaterials, inorganic nanomaterials, structured polymeric structures and liquid metals. These materials can be deformed according to the external pressure, so that their resistance or capacitance varies, resulting in sensing the pressure. In order to increase the sensitivity, many researches focued on the interface of two conductive substrate that are designed to measure the physical signals for the sensitive response, because the interface states are easily varied with the pressure. However, these mechanisms are valunerble to the repetitive operation and the initial state can be changed due to the weak adhesion state of the two substrate. Here, we introduce the crossed prism-like microfluidic channel structure, where the ionic liquid fill the channel. The two microfluidic channels were fabricated with prism like structure by using silicon-based polymers, and then, the sharp sides are orthogonally sandwitched to realize the nano-sized gap, that are highly robust and reversible. This nano-gap provide very sensitive response according to the external touch because the pressure is concentrated to the nano-gap region and the wall of the microfluidic channel is sufficiently soft and robust. We have demonstrated this system and characterized the performance, thereby realizing the transparent, stretchable and robust pressure sensor.

L.1.16
17:30
Authors : Joaquin Puigdollers, Luis Guillermo Gerling, Cristobal Voz, and Ramon Alcubilla
Affiliations : Dept. Enginyeria Electrònica. Universitat Politècnica Catalunya Barcelona (Spain)

Resume : In this work a series of picene Organic Thin-Film Transistors (OTFTs) were fabricated and characterized. The output characteristics of the devices were measured in air and showed typical p-type electrical characteristics. For low VDS values a supralinear behavior is observed, together with a moderate crowding effect, an indication that carrier injection at the electrodes determines the output characteristic in this regime. However, for higher VDS values a Negative Differential Resistance (NDR) behavior was clearly observed [1]. The presence of NDR behavior (to different extent) is sometimes observed in the saturation region of the output characteristics in OTFTs. Although this phenomenon can be observed with some frequency, a conclusive interpretation has not been proposed yet. Different explanations have been reported to describe the NDR behavior in OTFT characteristics. In a previous paper, the authors interpreted this effect by considering that an increasingly wider region of the channel is pinched off in the saturation regime. This region of high resistivity would act as a voltage divider, thus reducing the voltage drop at the electrodes available for carrier injection [1]. Nevertheless, the NDR phenomenon is typically more pronounced for OTFTs with very thin semiconductor layer. That is, for active layer thicknesses comparable to that of the dielectric. Considering this, in this work we propose a new approach to interpret the NDR effect. The conductance of the accumulation channel is proportional to the product of the carrier concentration and charge-transport mobility. The carrier concentration given by the density of states (g(E)) and occupation probability of these states (Fermi-Dirac distribution). The application of a VGS voltage shifts the density of states in the energy axis, increasing consequently the carrier concentration in the accumulation layer [2]. Organic semiconductors used to fabricate OTFTs have relative dielectric constants (relative permittivities) in the range of 2–4, similar to that of standard Silicon Dioxide (3.7–3.9) commonly used as a dielectric layer. Moreover, typical thicknesses of the semiconductor layer are 50-100 nm, again similar to the typical thickness of the Silicon Dioxide dielectric layer. Thus, the application of large VDS voltages (for a fixed VGS) will shift the density of states counteracting the gate voltage near the drain electrode. This reduces the effective density of states available for charge carrier transport across the channel. This approach has been used to successfully describe the NDR behavior observed in thermally evaporated picene TFTs. [1] Voz C., Marsal A., Moreno C., Puigdollers J. and Alcubilla R., “Comparison between the density-of-states of picene transistors measured in air and under vacuum”, Synthetic Metals, Vol. 161 (2012), pp 2554–2557. [2] Datta S., “Lessons from Nanoelectronics: A New Perspective on Transport (Lessons from Nanoscience: A Lecture Note)”, 1st edition, Word Scientific Publishing (2012).

L.1.17
17:30
Authors : Giulia Casula, Beata Tkacz Szczesna, Yan Busby, Katarzyna Soliwoda, Emilia Tomaszewska, Grzegorz Celichowski, Jaroslaw Grobelny, Jean-Jacques Pireaux, Piero Cosseddu, Annalisa Bonfiglio
Affiliations : G. Casula, P. Cosseddu, A. Bonfiglio - Dept. of Electrical and Electronic Engineering, University of Cagliari, , Piazza D'Armi, 09123 Cagliari, Italy; B. Tkacz Szczesna, K. Soliwoda, E. Tomaszewska, G. Celichowski, J. Grobelny - Department of Materials Technology and Chemistry, University of Lodz, Pomorska St. 163, 90-236 Lodz, Poland; Y. Busby, J.-J. Pireaux - Research Center in Physics of Matter and Radiation (PMR), Laboratoire Interdisciplinaire de Spectroscopie Electronique (LISE), University of Namur, rue de Bruxelles 61, B-5000 Namur, Belgium.

Resume : Organic semiconductor-based devices are attracting considerable interest as they can be fabricated on thin, flexible substrates with cost-effective large area techniques. Memory devices are essential for any electronic system, but currently organic memories can be still considered in an early stage of the research. Indeed features like reliable operation in ambient conditions, long term stability, lifetime and large-area processing are still not satisfactory. Recently, we employed an organic semiconductor, ActivInk™ N1400, for fabricating non-volatile resistive memories with record retention time in ambient conditions. In this work, we explore scalability of this structure to large-area processing by developing and optimizing a functional ink made of N1400 and gold nanoparticles (NPs) for the fabrication of high-performance organic memories through inkjet printing. NPs concentration influence on resistive switching and ink formulation for effective memory application are investigated. Fabricated devices are operated in ambient conditions with reproducible memory behavior, high ION/IOFF and low programming voltages. In-depth materials characterization are carried out to shine a light on resistive switching mechanism. Time-of-Flight Secondary Ions Spectrometry results show that NPs inside the organic layer can rearrange upon operation to form vertical conductive filaments, which may be reversibly formed and unfolded only if a suitable NPs density is present in the hybrid layer.

L.1.18
17:30
Authors : Hae Rang Lee, Sang Myeon Lee, A-Reum Han, Junghoon Lee, Changduk Yang, Joon Hak Oh
Affiliations : Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang, Gyeongbuk 37673, South Korea; Department of Energy Engineering, School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan 44919, South Korea; Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang, Gyeongbuk 37673, South Korea; Department of Energy Engineering, School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan 44919, South Korea; Department of Energy Engineering, School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan 44919, South Korea; Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang, Gyeongbuk 37673, South Korea;

Resume : A central approach in the design of materials for organic field-effect transistors (OFETs) is to manipulate donor (D) and acceptor (A) blocks in π-conjugated semiconducting polymers to achieve controllable energy band gaps and tunable charge transport properties in the conjugation systems. Despite beneficial characteristics of D-A polymers for use in electronics, good processability in environmentally benign solvents remains a challenge because of their rigid DPP skeleton. Given that furan-based materials have better solubility in various solvents than analogous thiophene-based materials, we have synthesized and characterized furanyl-diketopyrrolopyrrole polymer (PFDPPTT-Si) together with its thienyl-diketopyrrolopyrrole-based analogue (PTDPPTT-Si) The chloroform-cast OFETs of PTDPPTT-Si exhibited a greater mobility compared to that of PFDPPTT-Si because of tightly aggregated π-stacking structures. By contrast, because of its enhanced solubility, PFDPPTT-Si using chlorine-free solution processing results in a device with the highest performances among furan-containing polymers reported to the best of our knowledge for non-chlorinated solvents. Our study demonstrates an important step toward environmentally compatible electronics, and we expect the results of our study to reinvigorate the furan-containing semiconductors field.

L.1.19
17:30
Authors : Olga N. Kazheva, Irina D. Kosenko, Andrey V. Kravchenko, Denis M. Chudak, Vladimir A. Starodub, Vladimir I. Bregadze, Oleg A. Dyachenko
Affiliations : Institute of Problems of Chemical Physics, Russian Academy of Sciences, Semenov Av. 1, 142432, Chernogolovka, Moscow Region, Russia; V. N. Karazin Kharkiv National University, Svoboda Sq. 4, 61077, Kharkiv, Ukraine; A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Str. 28, 119991, Moscow, Russia; RUDN University, 6 Miklukho-Maklaya st, 117198, Moscow, Russia; Institute of Chemistry, Jan Kochanowski University, Checinska Str. 5, 25020 Kielce, Poland

Resume : New radical-cation salts based on bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) were synthesized: (ЕТ)2[8,8’-Cl2-3,3’-Fe(1,2-C2B9H10)2] (1), (ЕТ)2[8,8’-Br2-3,3’-Fe(1,2-C2B9H10)2] (2) and (ЕТ)[8,8’-I2-3,3’-Fe(1,2-C2B9H10)2] (3). Their crystal structures were studied by X-ray analysis, electroconducting and magnetic properties were measured in a wide temperature range. All the salts were found to be paramagnetic. Their room temperature conductivities were 5, 2 and 10-6 Ohm-1cm-1, respectively for (1), (2) and (3). Compounds (1)-(3) are the first bi-functional salts containing [8,8’-Cl2-3,3’-Fe(1,2-C2B9H10)2]-, [8,8’-I2-3,3’-Fe(1,2-C2B9H10)2]- and [8,8’-Br2-3,3’-Fe(1,2-C2B9H10)2]- anions, respectively. In the literature the [8,8’-I2-3,3’-Fe(1,2-C2B9H10)2]- and [8,8’-Br2-3,3’-Fe(1,2-C2B9H10)2]- anions are presented for the first time. Summarizing the data for salts (1)-(3) we come to the conclusion that at reducing in the I-Br-Cl row the substituent’ sizes of a bis(dicarbollide) ligand of the [8,8’-X2-3,3’-Fe(1,2-C2B9H10)2] anion (X = I, Br, Cl) there is a tendency for electroconductivity rise of the corresponding ET salt: at reducing the halogen substituent size a compression of the anion sublattice occurs with the corresponding radical-cation packing compaction, which in its turn, favors with the growth of crystals electroconductivity. Acknowledgements This work was supported by the Russian Foundation for Basic Research

L.1.20
17:30
Authors : Alexis Claveau, Roman Marty, Thomas Schmaltz, and Holger Frauenrath
Affiliations : Ecole Polytechnique Federale de Lausanne (EPFL) – Institute of Materials (IMX) Laboratory of Macromolecular and Organic Materials (LMOM) Address: EPFL- STI - IMX – LMOM, Station 12 1015 Lausanne, Switzerland

Resume : The laterally restricted geometry of one-dimensional organic nanostructures renders them ideal model systems for the understanding of charge generation and transport under confinement.[1] We have recently prepared self-assembled organic nanowires comprising a single stack of π-conjugated molecules at their core using oligopeptide-functionalized perylene bisimides.[2] The synergistically enhanced π-π interactions and hydrogen-bonding give rise to stable nanowires with uniform lateral dimensions and strong interactions of the chromophores. Here, we report on a thorough spectroscopic study based on UV/Vis, circular dichroism, and infrared spectroscopy, showing a two-fold odd-even effect of certain molecular parameters on the optical and electronic properties of the nanowires.[3] Additionally, we investigated the electronic properties of the nanowires in transistor devices, with and without illumination. A direct correlation between the charge transport properties, the spectroscopic results, and the investigated molecular structure parameters was observed. These results reveal the impact of even small variations in the molecular design on the overall properties of such nanowire systems that we attribute to the strict confinement of its lateral dimensions. References 1. Haedler, A.T. et al., Nature 523, 196-199 (2015). 2. Marty, R. et al., ACS Nano 7, 8498–8508 (2013). 3. Marty, R. et al., J. Am. Chem. Soc. 136, 3919–3927 (2014).

L.1.21
17:30
Authors : S.A. Ponomarenko, O.V. Borschev, E.V. Agina, M.S. Polinskaya, A.S. Sizov, A.A. Trul, V.P. Chekusova, M.A. Shcherbina, S.N. Chvalun
Affiliations : Enikolopov Institute of Synthetic Polymer Materials of Russian Academy of Sciences (ISPM RAS), Moscow, Russia; Moscow State University, Chemistry Department, Moscow Russia; National Research Centre "Kurchatov Institute", Moscow, Russia; Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, Russia

Resume : Development of efficient self-assembled monolayer field-effect transistors (SAMFETs) is a great challenge for organic electronics [1]. Recently we reported organosilicon derivatives of oligothiophenes capable to monolayer formation on the water-air interface, which were used for SAMFET fabricated by Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques [2,3]. In this work we synthesised different organosilicon derivatives of [1]benzothieno[3,2-b][1]-benzothiophene (BTBT) and used them for efficient LB and LS SAMFETs [4]. The LB and LS SAMFETs with charge carrier mobilities up to 0.02 cm2/Vs, threshold voltage close to 0V and on/off ratio up to 10,000 based on chlorosilane and disiloxane derivatives of BTBT were fabricated. The results obtained demonstrate that the presence of covalent bonds between a semiconducting monolayer and a substrate is not crucial for the SAMFETs performance. In this presentation, influence of chemical structure of the molecules synthesized on the morphology, molecular ordering and semiconducting properties of their monolayers will be considered. Their potential for ultrasensitive gas sensors will be discussed. This work was supported by Russian Foundation for Basic Research (grants 16-29-05321 and 17-03-00222). [1] O.V. Borshchev, S.A. Ponomarenko, Polym. Sci. Ser. C, 2014, 56, 32 [2] A.S. Sizov, et al., Langmuir, 2014, 30, 15327 [3] E.V. Agina, et al., Proc. SPIE, 2015, 9568, 95680Z [4] O.V. Borshchev, et al., Chem. Commun., 2017, 53, 885

L.1.22
17:30
Authors : A.Stanculescu(1), C.Breazu(1,3), M.Socol(1), A.-M.Catargiu(2), L.Vacareanu(2), M.Grigoras(2), F.Stanculescu (3), G.Socol(4), M.Girtan(5)
Affiliations : (1)National Institute of Materials Physics, 105 bis Atomistilor Street, Magurele-Bucharest, 077125 Romania, sanca@infim.ro; (2)P. Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487-Iasi, Romania; (3)University of Bucharest, Faculty of Physics, 405 Atomistilor Street, Magurele-Bucharest, 077125 Romania; (4)National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, Nr. 409, Magurele-Bucharest, 077125, Romania; (5)Laboratoire LPHIA, Université d’Angers, LUNAM, 2 Bd. Lavoisier 49045, Angers, France

Resume : The synthesis of new organic semiconductors and development of new device configurations represent alternatives for obtaining an efficient charge carriers transport and devices with improved performances. This paper proposes new organic compounds as donor poly(arylenevinylene)s containing carbazole units substituted at 2,7- and 3,6-positions [poly(N-(2-ethylhexyl)-2,7-carbazolylene-vinylene or poly(N-(2-ethylhexyl)-3,6-carbazolylene-vinylene)] and as acceptor perylene tetracarboxidiimide (N,N’-bis-1-dodecyl)perilene-3,4,9,10-tetracarboxidiimide) blended in different weight ratios(1:1; 1:2 and 1:3). The layers have been deposited by spin coating from chloroform at a rotation speed of 1500-3000 rpm for 10-30 sec on glass/ITO substrate previously treated in oxygen plasma. A metallic electrode of Al has been deposited by vacuum evaporation on top of the heterostructures. The layers have been characterized by spectroscopic (UV-VIS, PL) and microscopic methods (AFM, SEM) and the effect of the blend composition on the optical and electrical properties of the heterostructure has been investigated. The properties of the heterostructures prepared by spin-coating have been compared with those of the same heterostructures prepared by matrix-assisted pulsed laser evaporation/MAPLE from the same solvent at the same donor:acceptor weight ratios.

L.1.23
17:30
Authors : Hsaio-Ping Lai, Yian Tai*
Affiliations : Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, 10607 Taiwan, *ytai@mail.ntust.edu.tw

Resume : The low band gap (LBG)polymer poly{2,6-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,4-b]dithiophene-alt-5-dibutyloctyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-dione}(PBDTT-DPP) is an emerging material in the field of organic electronics, particularly organic solar cell (OSC). However, its usage in OTFT applications is still lacking of detailed studies. Due to more complicate structures, in general, post deposition-annealing of LBG polymer is not a suitable process when utilizing these polymers in OSC. However, with the present study, we fabricated top gate bottom contact (TGBC) configuration OTFT using PBDTT-DPP as active layer, and found that various transistor characteristics can be enhanced using parametric optimization of annealing conditions. Moreover, higher annealing temperature in comparison to previously used have significantly reduced the leakage current and increased the mobility and On/off ratio. The devices also showed remarkable stability even after kept for several days under ambient conditions without packing.

L.1.24
17:30
Authors : C. Haddad, S. Jacob, M. Charbonneau, X. Mescot, A.Revaux, G. Ghibaudo
Affiliations : Univ. Grenoble Alpes, CEA-LITEN, Grenoble, 38000, France ; Univ. Grenoble Alpes, CEA-LITEN, Grenoble, 38000, France ; Univ. Grenoble Alpes, CEA-LITEN, Grenoble, 38000, France ; IMEP-LAHC, INPG – Minatec, Grenoble, 38000, France ; Univ. Grenoble Alpes, CEA-LITEN, Grenoble, 38000, France ; IMEP-LAHC, INPG – Minatec, Grenoble, 38000, France

Resume : During the last ten years, organic thin film transistors performance has increased dramatically and is now comparable with amorphous silicon devices, especially mobility wise. Furthermore, organic devices can be processed in solution at room temperature and on flexible substrate, which opens new perspectives in display and sensor addressing applications [1]. For this experiment, printed top gate bottom contact P-OTFTs have been processed on flexible plastic substrate using a commercially available p-type semi-conductor polymer (SP400 from Merck) with a mobility range from 0.5 to 1 cm²/Vs. The transport in this new semi-conductor has been investigated by performing low temperature measurements. Transfer curves measurements have been carried out on OTFTs at different temperatures from 300K down to 125K and then going back up to 300K without degradation, confirming the good stability of the device. In order to exclude contact resistance effects, the Y function method [2] has been employed for threshold voltage and mobility extraction. Mobility evolution versus temperature supports the hypothesis of thermally activated hopping transport. Moreover, the activation energy which can give an insight into the effective width of localized states will be discussed. [1] S. Jacob et al., Proceedings of IEEE International Electron Devices Meeting (IEDM), 2015 [2] Y. Xu et al, Journal of Applied Physics, 107, 11, pp.114507-7, June, 2010.

L.1.25
17:30
Authors : V.A. Trukhanov, V.V. Bruevich, D.Yu. Paraschuk
Affiliations : International Laser Center and Faculty of Physics of Lomonosov Moscow State University, Moscow, Russia

Resume : Organic field-effect transistors (OFET) are perspective basic elements for low-cost, large-area electronic devices. The crucial parameter that determines the OFET performance is the charge carrier mobility. The common method of mobility measurement in OFET consists in approximation of the transfer characteristics by Shockley equations in the linear and saturation regimes. However, this method can lead to incorrect estimation of charge mobility in organic semiconductor. In the common top-contacts and bottom-gate OFET geometry, the current needs to pass through the thickness of organic semiconductor layer under the source and drain contacts, and the voltage can drop across the layer due to space charge limited current (SCLC). In this work, we study how the SCLC under the source and drain electrodes affects the apparent mobility determined from the transfer characteristics. We developed both numerical and analytical models of OFET with SCLC under the contacts and found how the fitted OFET mobility changes with the active layer thickness. The modeling showed that the apparent OFET mobility drops with increasing the active layer thickness and decreasing the transverse charge mobility (across the active layer). These findings allow evaluation of the intrinsic OFET mobility and provide guidelines for further improvement of OFET performance. This work was supported by Russian Science Foundation (grant 15-12-30031).

L.1.26
17:30
Authors : Susumu Ikeda
Affiliations : WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Japan

Resume : In 2006, we first reported organic graphoepitaxy, in-plain oriented growth on artificial microstructures, observed in sexithiophene (6T) [1]. In the experiments, thermally oxidized silicon substrates with periodic microgrooves were prepared and 6T thin films were grown on the substrates by molecular beam deposition. It is interesting to note that in-plane orientation changed 90 degrees depending on the surface conditions; c-axis was parallel to the extension direction of the grooves on hydrophobic surface while c-axis was perpendicular to the direction on hydrophilic surface (b-c plane was on the surface) [2]. Recently, I started molecular dynamics (MD) simulations to clarify the mechanism of such interesting phenomena of graphoepitaxy at a molecular level. MD simulations revealed that three in-plane orientations, c-axis is parallel, perpendicular, and about 45 degrees to the groove direction, are stable both on hydrophilic and hydrophobic surface, and further investigation is needed to completely clarify the mechanism of the in-plane orientational change. Dynamic processes of deposition and crystallization were simulated using pentacene molecules and graphoepitaxial growth could be partially reproduced. It is expected that deep understanding of the mechanism will lead to the practical application of graphoepitaxy to improving the performance of organic devices. [1] S. Ikeda et al., Appl. Phys. Lett., 88, 251905 (2006). [2] S. Ikeda et al., J. Appl. Phys., 103, 084313 (2008).

L.1.27
17:30
Authors : V.A. Trukhanov, E.V. Parygin, V.V. Bruevich, D.Yu. Paraschuk
Affiliations : International Laser Center and Faculty of Physics of Lomonosov Moscow State University, Moscow, Russia

Resume : Organic light-emitting transistors (OLETs) are emerging organic electronic devices which combine electrical switching ability of organic field-effect transistors and light-generation capability of organic LEDs. While it was reported that the OLET quantum efficiency may exceed that of organic LEDs [R. Capelli, et al. Nat. Mater. 9, 496 (2010)], the power conversion efficiency (PCE) of OLETs is still significantly lower compared to organic LEDs. This is particularly due to the lack of understanding of the OLET device physics, especially the main energy loss channels. In this work, we present a one-dimensional drift-diffusion numerical model of OLET and study the OLET performance for various parameters and properties of active layer and electrode materials. We have found that the OLET PCE is the most sensitive to the work functions of source and drain electrodes, while the most of geometrical and material parameters of the OLET channel give a far less pronounced effect on the OLET performance. We analyze the energy losses due to low carrier mobility, insufficient selectivity and high contact resistance of the electrodes, energetic disorder, and non-radiative recombination. Approaches for minimizing these losses are discussed. Our findings can help to improve the OLET performance. This work was supported by Russian Science Foundation (grant 15-12-30031).

L.1.28
17:30
Authors : Jun-Seok Yeo, Oh Young Kim, Seok-Ho Hwang
Affiliations : Department of Polymer Science & Engineering and Soft Chemical Materials Research Center, Dankook University

Resume : Recently, thermally activated delayed fluorescent OLEDs are used great attention of many researchers. Thermally activated delayed fluorescence (TADF) OLEDs convert 75% of non-radiative triplet excitons into radiative singlet excitons by reverse intersystem crossing (RISC). To be efficient TADF emitting materials, the energy gap between singlet excited state and triplet excited state should be small enough to occur RISC at room temperature. Therefore, distribution of HOMO and LUMO should be highly separated by donor-acceptor structure to reduce the singlet excited state energy of molecules. According to the rules, several TADF materials have been developed. With an increasing requirement on device performance, especially efficiency stability, in recent years, much attention has been paid to TADF host material development with a focus on molecular engineering pertinent to structural and optoelectronic characteristics of specific TADF dyes. Ideal host materials for the TADF dopant much have high singlet and triplet energy for energy transfer, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) for exciton blocking, large overlap of the host PL emission with dopant absorption and bipolar charge transport properties for charge balance. In this study, the bipolar host materials for TADF emitting device were synthesized to study the effect of new acceptors on physical properties and device performances. It was coupled between phthalimide as acceptor and carbazole as donor to build up narrow singlet-triplet energy gap. Also, it was demonstrated the effect of linkage positions such as orth-, meta- and para-positions on the photoluminescence quantum yield and device performances.

L.1.29
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Organic Photovoltaics : Martin Heeney, Wouter Maes, Martin Brinkmann
08:30
Authors : Sarah Holliday (1), Christine Luscombe (1,2)
Affiliations : (1) Materials Science and Engineering Department, University of Washington, Seattle, WA 98195-2120, USA; (2) Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA

Resume : Organic photovoltaics based on semiconducting polymers offer a promising route towards low cost, printable and flexible technologies for solar energy conversion. Significant advances have been made in recent years towards improving the power conversion efficiency (PCE) of these devices up to 10-12%, now approaching those required for commercial applications. However, the successful implementation of this technology remains limited by operational lifetime, which is largely due to the unstable nature of the organic semiconductors themselves. Many of the best performing polymers in terms of efficiency are in fact highly unstable, including the widely studied benzodithionene polymer PTB7 and its derivatives. Currently the mechanism causing such polymers degrade is poorly understood, which hinders the development of more stable derivatives with competitive operating lifetimes. In this work, we investigate the photooxidative stability of polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) and its analogue PTB7-Th with alkylthienyl side chains on the central benzodithiophene unit. We reveal how these side chains play a critical role in the rate of photochemical degradation, and how this impacts device operating lifetimes. In addition, we discuss the important role of high boiling point solvent additives such as 1,8-diiodooctane on polymer reactivity, with the rate of degradation seen to be critically dependent on the extent of drying of the thin film during device fabrication. These insights can in turn help in the design of more air- and light-stable polymers for organic photovoltaics that maintain both high efficiencies and competitive operating lifetimes.

L.1.1
09:00
Authors : Nutifafa Y. Doumon *1 G. Wang 2 Ryan C. Chiechi 1,2 L. Jan Anton Koster 1
Affiliations : 1 Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG, Groningen-The Netherlands 2 Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, NL-9747 AG, Groningen-The Netherlands

Resume : Novel design of polymers has brought more attention to bulk heterojunction polymer:fullerene solar cells (PSCs) in the past ten years. A typical example is the synthesis, through chemical structure engineering, of the benzodithiophene-co-thieno[3,4-b]thiophene (BDT-TT) polymers leading to power conversion efficiency (PCE) of over 10%. In this work, we study both device PCE and stability for a set of PBDT-TT polymers and the effect of an additive on the solar cell performances. Our results show an enhancement in efficiency (0-56 % rise in PCE) and an accelerated UV-degradation for devices processed with additive. Additionally, we conducted a systematic UV-degradation study on the solar cells. We found that based on the polymer chemical structure, PSCs of polymers with alkoxy side chains are more stable (~20 % loss in PCE) than those with alkylthienyl side chains (~40% loss in PCE). These findings pave the way for new materials that yield efficient as well as stable organic solar cells.

L.1.2
09:15
Authors : Derya Baran, Andrew Wadsworth, David A. Hanifi, Shahid R. Ashraf, Sarah Holliday, Marios Neophytou, Thomas Kirchartz, Alberto Salleo, Aram Amassian, Iain McCulloch
Affiliations : Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, UK King Abdullah University of Science and Technology (KAUST), KSC, Thuwal 23955-6900, Saudi Arabia IEK5-Photovoltaics, Forschungszentrum Jülich, 52425 Jülich, Germany Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA

Resume : -Preferable a contributed talk. Organic photovoltaics have surpassed 11% power conversion efficiency through the careful design of low bandgap polymer donors to be used with fullerene acceptors. Despite this impressive progress, most of these high performance devices exhibit poor stability. Additionally, P3HT remains the only cost-effective donor polymer and the limitations of using fullerenes in photovoltaic devices continue to persist. We have recently shown that the efficiencies of P3HT devices can reach as high as 6.4% by replacing PCBM with a non-fullerene small molecule acceptor.1 The use of these acceptors in multi-component heterojunctions can further increase the efficiencies achieved by the P3HT devices. We have developed a novel approach towards high efficiency organic photovoltaic devices; where P3HT is combined with two non-fullerene acceptor molecules in a ternary blend. Ternary blends that make use of two polymer materials have been explored in the past, however the lack of entropic driving force and the potential for intermolecular interactions between polymer chains renders this approach problematic.2 The introduction of small molecule acceptors into the P3HT binary devices leads to an increase in efficiency up to 7.7% and importantly a vast improvement in device stability. Tuning of the second acceptor’s LUMO allows a higher VOC to be achieved, and through careful selection of the acceptors and their ratios a favourable blend morphology can be achieved, thereby reducing recombination in the blends. This is the highest efficiency value reported for P3HT based solar cells, to date. The universality of the method is proved with a commercially available low band gap polymer PCE10 and a power conversion efficiency up to 11.0 ± 0.4% have been achieved with a high open-circuit voltage of 1.03 ± 0.01 V. 1. S. Holliday et al. High-efficiency and air-stable P3HT-based polymer solar cells with a new non-fullerene acceptor, Nat. Commun., 2016, 7, 11585 2. C. B. Nielsen et al. Non-fullerene electron acceptors for use in organic solar cells, Acc. Chem. Res., 2015, 48, 2803-2812

L.1.3
09:30
Authors : Artem A. Bakulin*, Tom Hopper*, Vincent Lami**, David Leibold**, Paul Fassl**, Yvonne J. Hofstetter**, David Backer-Koch**, Paul E. Hopkinson**, Yana Vaynzof**
Affiliations : *Imperial College London, U.K. **Heidelberg University, Germany

Resume : We present the first investigation of the use of N-heteroacenes as acceptors in bulk heterojunction solar cells. The optical and electronic properties of tetraazapentacene (TIPS-TAP), triptycene-tetraazapentacene (TIPS-TAP-1T) and bistriptycenyl-tetraazapentacene (TIPS-TAP-2T) compounds are characterised by means of optical and electronic spectroscopies and correlated with photovoltaic performance. The cells with TIPS-TAP-2T significantly outperform those with other acceptors, achieving power conversion efficiency of 2.5% without the use of additives. We investigate the photophysics of charge separation at the donor/acceptor interface and find that it is fundamentally different from ‘conventional’ polymer-fullerene systems. For example, in the blends with the tetraazapentacene derivatives, exciton dissociation is relatively slow and charge separation is strongly field dependent. In agreement with photovoltaic device characterisation, we observe that charge generation is improved in TIPS-TAP-2T and TIPS-TAP-1T compared to TIPS-TAP, and that geminate recombination is significantly reduced in the case of TIPS-TAP-2T as compared to the other derivatives. The combination of improved film microstructure and more efficient charge separation result in the observed enhancement in the photovoltaic performance.

L.1.4
10:00 Coffee break    
10:30
Authors : Feng Gao
Affiliations : Linköping University

Resume : Compared with inorganic or perovskite photovoltaics, the key limiting factor for organic solar cells (OSCs) is large voltage loss, which is usually over 0.7 V. A significant contribution of the large voltage loss in OSCs is due to strong non-radiative recombination, which causes voltage loss of more than 0.35 V in most cases. The origin of the strong non-radiative recombination in OSCs has been puzzling the community for almost one decade, limiting rational design of materials to overcome this critical issue. In this study, we systematically investigate several exceptional OSC systems (including fullerene and nonfullerene electron acceptors), where the voltage loss is reduced to <= 0.7 V. We find that the quantum efficiency of electroluminescence in these systems have been significantly increased. Our work would pave the way to rational design of novel OSC materials for small voltage loss and high efficiency.

L.1.5
11:00
Authors : Ralph Eckstein1,2,, Tobias Rödlmeier1,2, Uli Lemmer1,3, Gerardo Hernandez-Sosa*1,2
Affiliations : 1 Karlsruhe Institute of Technology, Light Technology Institute, Engesserstr.13, 76131 Karlsruhe, Germany 2 InnovationLab GmbH, Speyerer Str. 4, 69115 Heidelberg, Germany 3 Karlsruhe Institute of Technology, Institute of Microstucture Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Resume : Organic semiconductors offer very promising and unique properties towards light sensing applications e.g. tunable absorption spectra, solution processability, mechanical flexibility and high internal quantum efficiencies. For that reason, optical sensors using these materials fabricated by industrial relevant printing techniques will become more and more relevant for many applications in e.g. sensing in wearables and medical diagnostics, environmental monitoring, or automotive industry. In this work we present highly efficient multi-layer organic photodiodes based on the polymer-fullerene blend PTB7:PC70BM, an AZO electron transport layer, and PEDOT:PSS electrodes, which were entirely aerosol jet printed on flexible PET substrates. Furthermore, we demonstrate a new direct-printed patterning technique comprising aerosol jet and inkjet printing, which allows for very precise, reproducible and highly registration accurate deposition of a multi-layer devices with feature sizes down to a few micrometers. We present a comprehensive electrical and optical characterization of the printed layers and devices in dependency of the active layer thicknesses, surface topography and transparency. The devices exhibited specific detectivities of >1E12 Jones over a broad wavelength range (400-750 nm) and maximum responsivities of 0.25 A/W.

L.1.6
11:15
Authors : Pierre Lienhard, Amelie Revaux*, Alexandre Pereira, Stéphanie Jacob, Jerome Faure-Vincent, David Djurado
Affiliations : Pierre Lienhard, Amelie Revaux, Alexandre Pereira, Stéphanie Jacob CEA-LITEN, Univ. Grenoble Alpes; Jerome Faure-Vincent CEA-INAC, Univ. Grenoble Alpes; David Djurado CNRS-INAC, Univ. Grenoble Alpes

Resume : Over the past few years, great improvement has been made in organic devices performances even if problems with their stabilities still persist, constraining the use of costly encapsulations. In operating conditions, organic photodiodes (OPD) are exposed to many stresses (light, water, oxygen, temperature, electrical bias) which induce degradations and performances losses. In this work we aim to understand and uncorrelate the role of each stress in the device degradation by investigating the impact of environment and light on electrical characteristics of operating semi-transparent OPD. For this purpose, different ageing have been performed in dark, under light and in different atmospheres such as inert gas, dry air, and ambient air. Scenarios are proposed to explain the degradation based on the analysis of the device figures of merit and numerical simulations. Finally, complementary electrical and chemical characterizations have been performed in order to highlight the degradation mechanisms. For instance, we show that oxygen induces acceptor traps in the bandgap of the active layer that reduces photocurrent and increases charges injection and capacitance in the quasi-static regime in the dark. An asymmetry of the external quantum efficiency depending on the illumination side is also found. This highlights the irreversible impact of oxygen on the reliability of optoelectronics devices even in the absence of light.

L.1.7
11:30
Authors : Carsten Deibel
Affiliations : Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany

Resume : Organic bulk heterojunction solar cells contain a complex morphology of two organic semiconductors. The energetic distribution of localised states depends strongly on both, the properties of the neat materials and the blend morphology. Therefore, energetics and morphology play a major tole for the physical processes involved in photocurrent generation, for instance the recombination of charge carriers. This nongeminate recombination occurs across the donor-acceptor interface through charge transfer states. In disordered materials with low charge carrier mobilities it is usually described by the so called reduced Langevin rate. The latter is often orders of magnitude smaller than predicted by the Langevin rate, which is proportional to the sum of electron and hole mobility. Based on kinetic Monte Carlo simulations, we find that for typical phase dimensions, the nongeminate recombination is governed rather by the geometric mean of mobilities [1,2]. Another property of nongeminate recombination in organic blend systems is that the recombination order is often, particularly at low temperatures, increased above the expected order of two as two particles are involved. We present transient absorption data of organic semiconductor blends and show how the order or recombination relates to both, the diode ideality factor [3] and the energetic disorder. We will discuss what is required to bring these different perspectives into one unified picture for recombination in organic solar cells. [1] M. C. Heiber et al. Phys. Rev. Lett. 114, 136602, 2015 [2] M. C. Heiber et al. Phys. Rev. B 93, 205204, 2016 [3] K. Tvingstedt and C. Deibel. Adv. Ener. Mater. 6, 1502230, 2016

L.1.8
12:00 Lunch    
 
Synthetic Approaches : Artem Bakulin, Feng Gao, Carsten Deibel
14:00
Authors : Martin Heeney, Adam Creamer, Abby Casey, Pierre Boufflet, Zhuping Fei, Yang Han, Thomas D. Anthopoulos, Joshua Green, Shengyu Cong
Affiliations : Dept. Chemistry, Imperial College London, London SW7 2AZ

Resume : The tuning of the electronic properties of a conjugated polymer post-polymerisation is a potentially interesting approach to materials development. Provided functionalization chemistries can be found with close to quantitative yields, then the role of the substituent on the polymer properties can be investigated within the same batch of polymer. This eliminates the problems associated with batch-to-batch variations or differences in polymer chain length. If the functionalization can be performed under mild conditions such an approach can also be used to incorporate sensitive functionalities onto the polymer backbone. In this talk I will present out recent work towards developing functionalization approaches. I will discuss the incorporation of reactive endgroups and co-monomers which can be easily modified under mild conditions. I will discuss the role of the substituent on polymer properties and demonstrate how these approaches can be used to introduce reactive groups which can be cross-linked under very mild conditions.

L.1.1
14:30
Authors : Francesco Carulli, Wojciech Mróz, Silvia Luzzati, Mariacecilia Pasini, Francesco Galeotti, Guido Scavia, Sergio Brovelli, Silvia Luzzati and Umberto Giovanella
Affiliations : F. Carulli; W. Mróz; M. Pasini; F. Galeotti; G. Scavia; S. Luzzati; U. Giovanella - CNR - Istituto per lo Studio delle Macromolecole (ISMAC), via Corti 12, 20133, Milano, Italy. S. Brovelli, Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca Via R. Cozzi 55, 20125 Milano, Italy

Resume : Interfacial engineering has been recently identified as a fundamental strategy for maximizing efficiency and stability of organic electronic devices. To this aim, a new class of water/alcohol soluble materials comprising a π-conjugated backbone with pendant polar or ionic groups has been recently developed. The advantage of polar conjugated polymers is found in the combination of desirable properties: facile solution processability, chemical tunability, lightness and flexibility with the growing demand for eco-friendly materials. Moreover, the solubility in water and alcohols orthogonal to common solvents used for active layer deposition opens the way to all-solution-processed organic multilayer devices. In this view, we design, synthesize and test a whole series of polar conjugated polymers featuring a fluorene-based backbone with pendant phosphonate and/or amine groups [1]. We highlight their role as the cathode interfacial layer in performance enhancement of three types of common optoelectronic devices, i.e. polymer-based OLED [2], colloidal quantum dot LEDs [1] and organic solar cells. [1] A. Castelli, F. Meinardi, M. Pasini, F. Galeotti, V. Pinchetti, M. Lorenzon, ... & S. Brovelli, Nano Letters, 2015, 15(8), 5455. [2] W. Mróz, R. Ragni, F. Galeotti, E. Mesto, C. Botta, L. De Cola, G. M. Farinola, U. Giovanella. J. Mater. Chem. C, 2015, 3, 7506

L.1.2
14:45
Authors : Amparo Ruiz-Carretero, Phuong Tran, Frederic Tang
Affiliations : Amparo Ruiz-Carretero, Phuong Tran: Institut Charles Sadron, CNRS, Strasbourg. Frederic Tang: Université Pierre et Marie Curie (UPMC), Paris.

Resume : Securing the world’s population energy supply in a renewable way is one of the biggest challenges of our generation. Solar energy is a great alternative to solve fossil fuel exhaustion and climate change. Organic solar cells are attractive due to their light weight, flexibility and scalability, but several issues need to be solved to make this technology competitive. One of the main challenges is achieving the optimal active layer morphology. So far, none of the common materials used (pi-conjugated polymers or small molecules) form the desired structures to obtain devices with correct working mechanism: connection among semiconductors to form percolating domains and correct orientation (face-on with respect to the electrodes) of such domains. Therefore, the search of new materials is necessary. Here we introduce supramolecular strategies in organic photovoltaics and present a library of hydrogen-bonded materials to address the issue of achieving strong percolating domains not disrupted when acceptor materials, such as fullerenes or non-fullerene based molecules are added. Recently, the use of hydrogen-bonded semiconductors has shown 50% improvement in device efficiency. However, this is just the tip of the iceberg because only one hydrogen-bonding unit was used. A study of the hydrogen-bonding strength (amide, urea or semicarbazone), number (1, 2 or 4 hydrogen bonds) and position within the molecular structure is proposed to explore the role of self-assembly in achieving percolating domains and morphology improvement.

L.1.3
15:00
Authors : C. Brochon, G. Garbay, G. Hadziioannou, E. Cloutet
Affiliations : Laboratoire de Chimie des Polymères Organiques (LCPO) - UMR 5629 - University of Bordeaux /CNRS/IPB

Resume : Semi-conducting polymers are promising for the development of low-cost flexible optoelectronic devices. These technologies are not yet mature and several limitations emerge. Synthetic routes rely on complex protocols using costly and hardly removable catalysts. Residual metal traces affect performances, involving numerous purification steps. It is necessary to develop versatile, economically viable and “green” approaches for large-scale syntheses. In this contribution, we develop new synthetic tools for efficient polymers, by taking care of purity; variety of targeted structures and versatility of synthetic processes. Original polymers with aryl-vinyl repeating units are targeted, with the possibility to tune (minimize) the energy gap, photo/electro luminescence properties. More particularly, original alternated squaraine-based -conjugated polymers and/or -conjugated polyazomethines have been successfully synthesized, through metal-free condensation reactions. They exhibit interesting optical properties, such as a strong absorption and good emitting properties. Finally, the most promising polymers have been integrated in OLED as active materials.

L.1.4
15:15
Authors : Marco A. Squillaci1, Feng Liu2, Fan Zhang2, Xinliang Feng2,3 and Paolo Samorì1
Affiliations : 1 Université de Strasbourg, CNRS, ISIS, F-67000 Strasbourg, France. 2 School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China 3 Center for Advancing Electronics Dresden (CFAED) & Department of Chemistry and Food Chemistry, Technische Universität Dresden, Mommsenstraße 4, 01062 Dresden, Germany

Resume : The past decades have witnessed a remarkable increase in the performance of organic electronic devices such as thin-film transistors, light-emitting diodes, solar cells and sensors, but the patterning techniques that are compatible with these materials are still very few. In this work we report on a new approach to directly pattern functional organic polymers with photolithographic techniques and a minimal loss in terms of performances. This result is achieved by blending the chosen organic polymer with a new molecule, consisting in an aromatic core, functionalized with triple boron-fluorine groups (3BNF2), as cross-link agent to allow a facile and direct patterning. 3BNF2 can undergo cross-link upon irradiation with white and UV light sources commonly used in commercial photolithography setups. Thanks to its particular design, 3BNF2 can react just with itself, without affecting the structure and the properties of any other molecule in the systems. Furthermore, this molecule is extremely soluble in chlorinated solvents and in toluene, like the most common and performing organic functional polymers currently available on the market. To prove the effectiveness of our approach we used 3BNF2 in blend with a commercial N-type semiconducting polymer to make photo-curable Organic Thin-Film Transistors (OTFTs) with arbitrary shapes and high mobility.

L.1.5
15:30 Coffee break    
16:00
Authors : Pieter Verstappen, Tim Vangerven, Jeroen Brebels, Geert Pirotte, Dries Devisscher, Jurgen Kesters, Jean Manca, Dirk Vanderzande, Wouter Maes
Affiliations : UHasselt – Hasselt University, Institute for Materials Research (IMO-IMOMEC), Design & Synthesis of Organic Semiconductors (DSOS) / Organic and Nanostructured Electronics & Energy (ONE2), Agoralaan, 3590 Diepenbeek, Belgium

Resume : Donor-acceptor or push-pull type conjugated polymers have become a dominating class of active materials in the field of organic electronics. Their adjustable light-harvesting, charge transfer and charge transport characteristics have been beneficially applied in organic photovoltaics, photodetectors and thin-film transistors. The conventional synthetic approach towards these push-pull polymers is based on Suzuki or (mostly) Stille cross-coupling of complementary functionalized heterocyclic precursors. In the ideal world, this should give rise to a perfect alternation of the employed building blocks throughout the polymer backbone and this alternation of electron rich (donor/push) and electron deficient (acceptor/pull) moieties leads to a substantial decrease of the bandgap. In recent years, however, it has become increasingly clear that the ‘real’ structure of the resulting alternating copolymers is often quite different from the projected one. Structural imperfections can for instance result from homocoupling of two identical building blocks. Furthermore, the end groups of these donor-acceptor copolymers are often also not those expected or targeted. In this contribution, recent results from our group providing insights on the impact of homocoupling ‘defects’ on the device characteristics of organic solar cells will be presented. On the other hand, end group analysis of different types of low bandgap copolymers via MALDI-TOF mass spectrometry showed some surprising results.

L.1.6
16:30
Authors : Yiming Xiao, Danli Zeng, Xiaolu Su, Martin Brinkmann, Benoît Heinrich, Bertrand Donnio, Ji-Seon Kim, Jeong Weon Wu, Jean-Charles Ribierre, Emmanuelle Lacaze, Thierry Barisien, David Kreher, André-Jean Attias, Fabrice Mathevet
Affiliations : Institut Parisien de Chimie Moleculaire, UPMC-CNRS, 4 place Jussieu, Paris, France; Institut Charles Sadron, 23 rue du Loess, Strasbourg, France; Département des Matériaux Organiques, IPCMS, 23 rue du Loess, Strasbourg, France; Centre for Plastic Electronics, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom; CNRS-Ewha International Research Center, CERC, Ewha Womans University, Korea; Institut des NanoScience de Paris, UPMC-CNRS, 4 Place Jussieu, Paris, France

Resume : The self-organization of pi-conjugated organic materials forming highly ordered supramolecular architectures has been extensively investigated in the last two decades in view of optoelectronic applications. Indeed, the control of both the mesoscopic and nanoscale organization within thin semiconducting films is the key issue for the improvement of charge transport properties and achievement of high charge carrier mobilities. These well-ordered materials are currently either self-organized semiconducting polymers or liquid crystals. In this context, we endeavored to investigate the self-organization of semiconducting liquid crystalline materials incorporating different kind of pi-conjugated systems in unique molecular or macromolecular architectures. Here we describe the design and synthesis of (i) dyads and triads combining discotic or calamitic pi-conjugated mesogens, and (ii) side-chain liquid crystal semiconducting polymers where the backbone is a pi-conjugated polymer and the side groups are pi-conjugated discotic mesogens. In this work, we will give the details on the synthesis, structural characterization and morphology studied by Polarized-light Optical Microscopy (POM), Differential Scanning Calorimetry (DSC), Temperature-dependent small-angle X-ray diffraction, Grazing-incidence X-ray scattering (GIXS) and Atomic Force Microscopy (AFM). Moreover, their charge transport properties studied in OFET configuration will also be depicted.

L.1.7
16:45
Authors : Rukiya Matsidik,†,ǁ Alessandro Luzio,‡ Özge Askin, ‡ Daniele Fazzi,§ Alessandro Sepe,◊ Ullrich Steiner, ◊ Hartmut Komber,⊥ Mario Caironi,‡,* and Michael Sommer †,ǁ,#,*
Affiliations : † Universität Freiburg, Institut für Makromolekulare Chemie, Stefan-Meier-Str. 31, 79104 Freiburg, Germany ∥ Freiburger Materialforschungszentrum, Stefan-Meier-Str. 21, 79104 Freiburg, Germany ‡ Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133, Milano, Italy § Max-Planck-Institut für Kohlenforschung (MPI-KOFO), Kaiser-Wilhelm-Platz 1, D-45470, Mülheim an der Ruhr, Germany ◊ Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700, Fribourg, Switzerland ⊥ Leibniz Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany # FIT Freiburger Zentrum für interaktive Werkstoffe und bioinspirierte Technologien, Georges-Köhler-Allee 105, 79110 Freiburg, Germany

Resume : Backbone coplanarity of donor-acceptor conjugated polymers is an important factor that determines all properties from the single chain to aggregates and thin films, and hence is of importance for the performance of such materials in opto-electronic devices. Here we report the synthesis, characterization and charge transport performance of novel copolymers PNDIFu2 made from alternating naphthalene diimide (NDI) and bifuran (Fu2) units is reported. Usage of potentially biomass-derived Fu2 as alternating repeat unit enables quasi-flat polymer backbones due to reduced steric interactions between the imide oxygens and Fu2 units. Backbone planarization induces stronger aggregation in solution with respect to PNDIT2, which eases directional alignment of polymer chains within aggregates using off-center spin-coating. As a consequence, optimized PNDIFu2 films show a markedly stronger transport anisotropy when tested in FETs, achieving a ratio of 18.3 for PNDIFu2-C20 for backbones aligned perpendicular and parallel to the electrodes. Overall, optimized FETs made from PNDIFu2 show a maximum electron field-effect mobility of 0.21 cm2/Vs, which is approximately three-times lower compared to PNDIT2. Thus, the initially thought beneficially greater backbone planarity, closer π-π stacking distance and stronger aggregation leading to enhanced anisotropy for PNDIFu2 do not result in superior transport properties than in PNDIT2. A likely reason for this unexpected behavior is a higher intra-molecular reorganization energy than in PNDIT2, counterbalancing the otherwise beneficial properties of PNDIFu2 owing to stronger polaron localization.

L.1.8
17:00
Authors : A. V. Lunchev, A. Jaggi, V. Chandra, A. Ghosh, A. C. Grimsdale
Affiliations : Nanyang Technological University

Resume : Pentacene is one of the most investigated molecules in the field of organic field effect transistors (OFETs). Incorporation of nitrogen atoms into the aromatic core of an acene increases its electron affinity and stabilizes the frontier molecular orbitals. Thus, azaacenes have become widely studied materials due to their potential application as n-type semiconductors in OFETs [1]. Additionally, azaacenes and their derivatives are currently the object of study in the fields of organic light emitting diodes (OLEDs) and hole transporting materials in organic photovoltaics. This significant interest to azaacenes has led to the development of synthetic pathways for these molecules. Currently, a variety of azaacenes, especially tetraazaacenes containing two pyrazine rings, are readily available for structural studies and device fabrication due to well-developed synthetic procedures [2]. However, some nitrogen doped acenes, which should be important for understanding of various structure-property relations in the field of OFRETs, including 5,7-diazapentacene (quinolino[3,2-b]acridine) and its derivatives, have never been synthesized, and, thus, studied. Here we report our progress towards synthesis of 5,7-diazapentacene derivatives using the Friedlander condensation as a key step for building a pentacyclic framework. This involves a novel approach to synthesis of aromatic diamino diketones, via Sonogashira coupling followed by the one-pot reduction of nitro groups and the hydrolysis of triple bonds using SnCl2 in ethanol. The synthetic route allows attachment of various functional groups onto the framework of 6,8-diazapentacene. A variety of 5,7-diazapentacene precursors bearing alkyl chains have been synthesized in order to improve the solubility. The precursors with additional benzene rings were synthesized as well in order to improve stability of the final acene aromatic system as per “Clar’s rule”. All the precursors demonstrate strong fluorescence, which makes them interesting materials for studies in the field of OLEDs. Friedlander condensation of 2-aminobenzophenone with various diketones (1,2-, 1,3-, 1,4-cyclohexanediones and 2,3,7,8-tetrahydroacridine-4,5(1H,6H)-dione) followed by dehydrogenation gives a variety of nonlinear azaacenes. The optoelectronic properties of these materials are being studied to study their suitability for use in devices such as OFETs or OLEDs. 1. Anthony, J.E., Chemical Reviews, 2006. 106(12): p. 5028-5048. 2. Bunz, U.H.F., Accounts of Chemical Research, 2015. 48(6): p. 1676-1686.

L.1.9
17:15
Authors : Benlin Hu, and Martin Baumgarten
Affiliations : Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

Resume : The exploration of strong acceptors to develop excellently organic semiconductors with high carrier mobility and excellent stability is an intensive research topic in the community of organic electronics. Naphthalenediimide (NDI), benzothiadiazole (BT) and N-heteroacene (NHT) are the most frequently used electron-deficient units to design high performance n-type and ambipolar organic semiconductors. Herein, strong acceptors, benzothiadiazole-fused naphthalenediimides (BT-f-NDI), that combine naphthalenediimide (NDI), benzothiadiazole (BT) and N-heteroacene (NHT) in the same molecule are firstly reported. A series of BT-f-NDIs were synthesized by the condensation of tetrabromo-NDI and benzothiadiazole diamine. The strong acceptors with LUMO energy levels of ~4.5 eV were obtained. Organic field-effect transistors (OFETs) based on the BT-f-NDI were fabricated by solution process, showing good n-chanel field-effect character of high electron mobility and stability under ambient conditions.

L.1.10
17:30
Authors : Wei-Jie Huang, Sheng-Hsiung Yang
Affiliations : Institute of Lighting and Energy Photonics, National Chiao Tung University

Resume : We demonstrate an ionic polyfluorene (PF) derivative containing trimethylammonium hexafluorophosphate groups –(CH3)3N+PF6–, namely P1-PF6, into [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the electron transporting layer (ETL) for the fabrication of inverted perovskite solar cells (PSCs). The P1-PF6-doped PCBM layer was characterized with miscellaneous techniques, including SEM, AFM, UPS, PL quenching, and 4-probe conductivity measurements. The incorporation of the ionic polymer P1-PF6 helped to smooth the PCBM layer and to achieve better contact between PCBM and top electrode. Moreover, the results from PL quenching, UPS, and conductivity measurements indicated that the introduction of P1-PF6 enhanced the electron transporting and charge extraction of the doped PCBM film. Inverted PSCs with the configuration of ITO/PEDOT:PSS/CH3NH3PbI3/doped PCBM/Ag were fabricated and evaluated. The devices were characterized under the standard AM1.5G illumination condition in the ambient environment without encapsulation. The enhanced JSC of 17.32 mA/cm2 and PCE of 12.55% were observed from the PCBM:P1-PF6-based device compared with the un-doped one (JSC = 15.68 mA/cm2, PCE = 10.67%). In conclusion, a conjugated polyelectrolyte P1-PF6 was successfully incorporated into PCBM as the ETL to improve photovoltaic performance of inverted planar heterojunction PSCs for the first time.

L..0
17:30
Authors : Danny E. P. Vanpoucke
Affiliations : UHasselt, Institute for Materials Research (IMO-IMOMEC), Agoralaan, 3590 Diepenbeek, Belgium IMOMEC, IMEC vzw, 3590 Diepenbeek, Belgium

Resume : Metal-Organic Frameworks (MOFs) are a versatile class of crystalline materials showing great promise in a wide range of applications (e.g. gas sensing and storage, luminescence, pressure sensors, and catalysis ). They consist of inorganic nodes, often metal-oxides, which are linked through organic molecules leading to highly porous crystal structures. As a result, their very structure puts them at several cross-sections: classical solids and molecules, surfaces and bulk,. . . Furthermore, since they combine properties either intrinsic to solids or molecules, these materials also provide ample opportunities to investigate fundamental materials properties from both physical and chemical perspective.[1] In short, they are a dream-come-true playground for the material scientist. By changing the metal-oxide or modifying the organic linker molecules, the electronic structure of these materials can be modified at will. In this work, we show how, based on DFT calculations, linker functionalization modifies the global electronic structure of MOFs.[2,3] We compare the results for the luminescent UiO-66 and flexible MIL-47 MOFs revealing the role of the metal-oxide nodes and propose other functional groups to further reduce the band gap size.[3] [1] Beilstein J. Nanotechnol. 5, 1738-1748 (2014) [2] Inorg. Chem. 54(22), 10701-10710 (2015), [3]“Linker functionalization in MIL-47(V)-R Metal-Organic Frameworks: Understanding the electronic structure”, D.E.P. Vanpoucke, submitted (2016)

L..0
17:30
Authors : M.S. Kotova, K.A. Drozdov, E.A. Kuzmina, T.V. Dubinina, R.B. Vasilev, L.G. Tomilova
Affiliations : Lomonosov Moscow State University, Department of Physics; Lomonosov Moscow State University, Department of Physics; Lomonosov Moscow State University, Department of Chemistry; Lomonosov Moscow State University, Department of Chemistry and Institute of Physiologically Active Compounds, Russian Academy of Sciences; Lomonosov Moscow State University, Department of Chemistry; Lomonosov Moscow State University, Department of Chemistry and Department of Chemistry and Institute of Physiologically Active Compounds, Russian Academy of Sciences

Resume : Development of compact, cheap and fast memory elements is one of the most rapidly growing areas of the modern electronics. Since the number of possible memory device applications is very high, it is important to consider alternative approaches for the memory technologies. In particular, the Resistive Random Access Memory (RRAM) is non-volatile, fast and endurable[1]. Active elements may be inorganic, organic as well as composite materials[1]. Advantages of the organic-based RRAM technology are low cost, easy processing and good scaling opportunities. The operation principles of resistive memory presume an ability of the system to switch between at least two states “ON” and “OFF” with different resistances (resistive switches RS). By variation of working conditions multiple stable states can be achieved. RS speed can be less than 15 ns, switches are non-volatile, on/off ratio over 2 orders of magnitude, switching electric field below breakdown values, retention time 3.5 months, number of rewriting cycles 105 or higher[2,3]. Samples can be fully fabricated by printing techniques, and we demonstrated that there are no significant differences in their performance compared to samples on hard substrates. As it was mentioned, it is important that organic-based memory devices are technologically adaptive and flexible. Therefore we have chosen widely spread commercially available polymers polystyrene (PS), polyvinylchloride (PVC) and polycarbonate (PC) as base materials for our experiments. These polymers are electrically isolating in pristine conditions, soluble in organic solvents and very cheap. To modify the RSE features organic photoactive semiconductor particles were added to the polymer matrix[4]. These particles of various sizes (1.3-2.3 nm in length and 0.3-0.8 nm height) allowed us to control switching voltage using external light source[4]. Introduction of inorganic nanoparticles (NP) can lead to increase in photoresponse in composite structures due to charge transport between NP and organic media. In this work we observed RS in composite structures consisting of polystyrene matrix with incorporation of colloidal CdSe nanoplates, tert-butyl-substituted lutetium diphthalocyanine, hexadecachloro-substituted lutetium triphthalocyanine and other dyes. By varying current compliance (by device settings or by series resistance) we obtained RS not only between ON and OFF states, but also between several intermediate states. For each state we performed impedance spectroscopy and observed typical single semicircles. Such type of impedance spectra is attributed to the equivalent scheme of parallel resistance Rc and capacitance C. Shift of the semicircles from zero at Z` axes is described by a series resistance R0, which is contributed to the contact resistance. For each impedance spectrum we performed theoretical fitting and calculated parameters Rtotal=Rc+Ro, R0, C. In the intermediate states with Rtotal 12.4 kOhm, 10.15 kOhm, 7.4 kOhm contact resistance R0 and capacitance C stay quite stable. After the switch to the highest conducting state with Rtotal=2.3kOhm the value of R0 is reduced in 2 times and C increases in more than 3 times. Drastic change in the capacitance is Maxwell-Wagner (M-W) effect and is usually explained by appearance of structural heterogeneities. This concept is well explained by filament formation mechanism of RS: metal or carbon filaments are built. In intermediate states only single filaments appear and in the highest conducting state a system of interwoven filaments arises. Single filaments in the intermediate state do not influence the sample capacitance, but in the case of multiple filaments the M-W effect takes place. Thus by in situ impedance spectroscopy we observed the formation of filamentary structure. We demonstrated that incorporation of CdSe nanoplates into organic matrix provides a promising material for construction of high density and efficient memory. Application of impedance spectroscopy is a powerful method for investigation RS filament formation mechanism. This work was supported by RFBR (project № 16-07-00961, 15-03-05890, 16-33-60005). [1] F. Pan, S. Gao, C. Chen, C. Song, F.Zeng; Materials Science and Engineering R, 83, 2014, 1 [2] M.S. Kotova, M.A. Dronov, A.V. Rzhevskiy, S.V. Amitonov, T.V. Dubinina, V.E.Pushkarev, L.I. Ryabova, D.R. Khokhlov; Organic Photonics and Photovoltaics, 4, 1(2016), 17-23 [3] M. Dronov, I. Belogorokhov, D. Khokhlov, MRS Proceedings, 2011, 1337 [4] M. Dronov, I. Belogorokhov, M. Kotova, MRS Proceedings, 2015, 1729

L..0
17:30
Authors : Yohei Yamamoto
Affiliations : University of Tsukuba

Resume : Optical microcavities play an important role for the next-generation light technology. Recently, we succeeded in fabricating spherical microcavities from π-conjugated polymers (CPs) by simple self-assembly process.[1,2] We found that the microcavities show whispering gallery mode (WGM) resonant photoluminescence (PL) upon focused laser excitation, where PL generated inside the sphere is confined via total internal reflection at the polymer/air interface.[3–9] The resonance occurs when the wavelength of the light is an integer multiple of the circumference of the microsphere. The CP-based microcavities have benefits to the conventional microcavities in the following points: [1] simple and low-energy fabrication process to obtain well-defined microspheres, [2] the microcavities function as both cavity and emitter, [3] the microcavities have high refractive index and photoabsorptivity, and [4] potent use for electrically-driven WGM and laser oscillation. In this seminar, recent results on the fundamentals of the self-assembly of the CPs, resonant PL from the CP microspheres, intra- and intersphere light energy conversion, and the future prospects to realize light-, electrically-, and chemically-driven WGM and lasing will be presented. References 1) T. Adachi, et al., J. Am. Chem. Soc. 2013, 135, 870−876. 2) L. Tong, et al., Polym. Chem. 2014, 5, 3583−3587. 3) K. Tabata, et al., Sci. Rep. 2014, 4, 5902/1−5. 4) S. Kushida, et al., Macromolecules 2015, 48, 3928−3933. 5) S. Kushida, et al., ACS Nano 2016, 10, 5543–5549. 6) D. Braam, et al., Sci. Rep. 2016, 6, 19635/1–6. 7) S. Kushida, et al., RSC. Adv. 2016, 6, 52854–52857. 8) Y. Aikyo, et al., Chem. Lett. 2016, 45, 1024–1026. 9) Y. Yamamoto, Polym. J. 2016, 48, 1045–1050.

L..0
17:30
Authors : Jung-Hwa Kim1, Yonung-nam Kwon1, Ji Young Jung2, EunKyung Lee2, Jeong-Il Park2, Ajeong Choi2, Jai-Kwang Shin1
Affiliations : 1 Platform Technology Lab, Samsung Advanced Institute of Technology, 130, Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea ; 2 Organic Materials Lab, Samsung Advanced Institute of Technology, 130, Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea

Resume : Organic semiconductors have been attracting lots of attention because they are applied especially to organic thin-film transistors (OTFTs). It is well known that OTFT device performance is influenced by the molecular packing structure and the surface morphology of the organic layer. Here we present the crystal structure and surface morphology of the Dph-DBTTT organic semiconductor thin film grown on the Si substrate investigated by grazing incidence wide angle x-ray scattering (GI-WAXS) and atomic force microscopy (AFM). Our results show that Dph-DBTTT forms a typical herringbone crystal structure. However, it is observed that the orientations of Dph-DBTTT molecules gradually changes as the distance from the interface near the substrate to the film surface increases, which may degrade OTFT performance. Further details on the crystal structures and the film thickness dependence of the morphology will be discussed in this presentation.

L..0
17:30
Authors : Chin-Han Liao, Cheng-Yi Liu
Affiliations : Department of Chemical and Materials Engineering National Central University, Taoyuan city, Taiwan

Resume : In this study, the hybrid organic/inorganic white-light emitting heterostructure is produced by combining the organic conjugated polymer F8T2 with the inorganic GaN-based epi-layers. The emitted white light consists of the green/yellow light and the blue light of GaN-based LED. Furthermore, the International Commission on Illumination (CIE) coordinate of the white light emission of the present device is at (0.28, 0.30), which is close to the standard white light (0.33, 0.33). The most important things in this study is that (1) organic/inorganic interface can produce light efficiently; (2) the main mechanism of this emitting organic/inorganic interface is electroluminescence; (3) this interface could be polarized, which might be the key to provide efficient recombination at the region near the heterojunction interface. These results are proved by the experiment of insetting the SiO2 layer into hybrid interface and the ultraviolet photoelectron spectroscopy (UPS) measurement. Then, to observe the transportation and the recombination of carriers in the F8T2/GaN-based LED, time-resolved photoluminescence (TRPL) and time-resolved electroluminescence (TREL) are used. By separating the green/yellow light and the blue light in TRPL and TREL measurement, the characteristic of the recombination carrier of the green/yellow light and the blue light can be defined, respectively. Also, it is worth noting that the electron-hole recombination time at the hybrid interface is much shorter than that of the GaN-based LED due to the polarized interface. Our work explores the applicability of polymer/GaN epi-layers emitting diodes for electrical and optical characteristics. The more detail would be discussed during this talk as well.

L..0
17:30
Authors : S. Schlißke, S. Menghi, A. Morfa, G. Hernandez-Sosa, U. Lemmer
Affiliations : Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany (S. Schlißke, S. Menghi, A. Morfa, G. Hernandez-Sosa, U. Lemmer) InnovationLab, Speyerer Strasse 4, 69115 Heidelberg, Germany (S. Schlißke; S. Menghi; A. Morfa; G. Hernandez-Sosa)

Resume : Direct printing allows solution processing of functional materials and opens a new route to fabricate low-cost electronic devices. One crucial parameter that influences the wettability of inks in all printing techniques is the surface free energy (SFE) of the substrate. Siloxanes, with their huge variety of sidechains, and their ability to form self-assembled monolayers, offer the possibility to control the SFE of substrates from e.g. hydrophilic to hydrophobic. This is a suitable approach to adjust the substrate conditions to the used ink, instead of the ink to a substrate. In this work the influence of different fluorinated and non-fluorinated siloxanes on the SFE of glass substrates is examined. Several different siloxanes were mixed and a fine tuning of the surface energy is demonstrated. The polar and disperse components of the SFE are determined with the OWRK-method. Furthermore, the influence of the SFE on the pinning of droplets and wet films is determined with dynamic contact angle measurements. The obtained results were used to directly influence the resolution of inkjet printed silver structures. A nano-particulate silver ink was used for printing single drops, squares and source-drain structures for transistors. These structures are examined in terms of diameter, edge quality, thickness homogeneity and functionality. We show that by adjusting the SFE of the substrate, the printed resolution could be increased by up to 70 % by decreasing the printed drop size.

L..0
17:30
Authors : Veroniki P. Vidali (1), Maria Vasilopoulou (1), Dimitra Niakoula (1), Anna Kapella (1),(2), Apostolos Verykios (1), Stella Kennou (3), Daman R. Gautam (1), Evangelos Gogolides (1), Elias A. Couladouros (1),(2), Panagiotis Argitis (1)
Affiliations : (1) Institute of Nanoscience & Nanotechnology, NCSR "Demokritos", Athens, Greece; (2) Chemical Laboratories, Agricultural University of Athens, Athens, Greece; (3) Department of Chemical Engineering, University of Patras, Patras, Greece.

Resume : Low molecular weight amorphous organic materials, have been receiving growing attention, exhibiting interesting optical, electrical, photoelectrical, magnetic and lithographic properties, opening up the road to the development of organic devices in the nanoscale with new functions and substantially enhanced performance. Herein, a design strategy for the synthesis of solution-processable anthracene-based semiconducting materials with well-defined molecular structures is presented. Multi-ring aromatic moieties are attached to a polyfunctionalized planar or tetrahedral core, also incorporating other groups, such as esters or cycloaliphatic moieties. Combination of groups is performed in such a way that provides control of physicochemical properties, such as solubility, thermal stability, and Tg. Depending on the targeting application, the crystallization of the films formed by these molecules can be also controlled. Selected compounds bearing suitable non-planar groups provide amorphous homogeneous films stable at temperatures well-above 100 °C, reaching up to 150 °C. These molecules provide frontier orbital and emission spectrum tuning capabilities and have been evaluated as main components in the active area of OLEDs, providing very promising results. Additional incorporation of suitable acid sensitive functional groups and sulfonium salts, as photoacid generators, allows self-patterning, where the UV exposed part of the film is removed. A flexible, efficient and cheap methodology, suitable for the preparation of these anthracene-based molecules in large scale will be also described.

L..0
17:30
Authors : Joan Ràfols-Ribé, Paul-Anton Will, Christian Hänisch, Marta González-Silveira, Javier Rodríguez-Viejo, Simone Lenk, Sebastian Reineke
Affiliations : joan.rafols@uab.cat, Group of Nanomaterials and Microsystems, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; paul-anton.will@iapp.de, Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01069 Dresden, Germany; christian.haenisch@iapp.de,Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01069 Dresden, Germany; marta.gonzalez@uab.cat, Group of Nanomaterials and Microsystems, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Javier.Rodriguez@uab.cat, Group of Nanomaterials and Microsystems, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; simone.lenk@iapp.de,Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01069 Dresden, Germany; sebastian.reineke@iapp.de,Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01069 Dresden, Germany;

Resume : Amorphous layers prepared by means of physical vapour deposition of small organic molecules are widely used in organic light-emitting diodes (OLEDs). While most of the research is mainly focused on the development of new materials and device architectures, little attention has been paid to the properties of each glassy layer. For many organic small molecule glass-formers it has been shown that the kinetic and thermodynamic stability, the density, or orientation of the molecules can be improved by properly setting the substrate temperature during deposition. Here we use a simple phosphorescent OLED stack, consisting only on two organic layers, to check the influence of the deposition temperature on the OLED performance. OLEDs comprising a green emitter achieve external quantum efficiencies of 19.4 % and 23.9 % at a current density of 1 mA/cm2 for deposition temperatures of 300 K and 343 K, respectively, reflecting a significant enhancement of 23 %. Other emitters (red and blue) were tested at these two temperatures using the same OLED stack achieving also significant improvements of 18 % and 103 %, respectively. The improvement of thermodynamic and kinetic stability of the emission and electron transport layer as a function deposition temperature is presented as a possible cause for this significant enhancement. This simple possibility to optimize the deposition conditions of the active layers provides a new strategy to achieve high efficiency OLEDs.

L..0
17:30
Authors : Artur A. Mannanov 1-2, Dmitry I. Dominskiy 2, Viktor A. Tafeenko 3, Oleg V. Borshchev 4, Sergey A. Ponomarenko 4, Dmitry Yu. Paraschuk 2, and Maxim S. Pshenichnikov 1
Affiliations : 1 - Zernike Institute for Advanced Materials, Rijksuniversiteit Groningen, the Netherlands; 2 - Faculty of Physics & International Laser Center, Lomonosov Moscow State University, Russia; 3 - Faculty of Chemistry, Lomonosov Moscow State University, Russia; 4 - Institute of Synthetic Polymer Materials, RAS, Russia

Resume : Single crystals of thiophene-phenylene co-oligomers (TPCO) have demonstrated high potential for organic optoelectronics due to unique combination of high charge carriers mobility and excellent photoluminescence (PL) efficiency [1]. Despite a considerable amount of experimental research, the detailed understanding of high PL in TPCO single crystals is still lacking. Time-resolved, polarization-sensitive PL parameters can provide important insights for establishing the relationship between the molecular structure and optical properties of TPCO. In this contribution, we analyze time-resolved PL anisotropy in a TPCO crystal based on the 1,4-bis{5-[4-(trimethylsilyl)phenyl]thiophen-2-yl}benzene molecule. X-ray diffraction experiments indicated the herringbone packing motif as have been reported for crystals based on analogous TPCO with the same terminal group [1]. Regardless of the excitation polarization, PL is mainly polarized along the molecule axis. However, quite surprisingly, PL induced by the excitation orthogonally polarized with respect to the molecular axis exhibits much higher intensity as compared to the parallel one. Such an unexpected PL anisotropy geometry is discussed in relation to the J-aggregates crystal packing and the impact of a luminescent impurities. This work was partially supported by Russian Science Foundation (grant 15-12-30031). [1] S.Hotta et al.,JMCC, 2(6),965(2014); L. Kudryashova et al., ACS Appl. Mater. Interfaces, 8(16),10088(2016)

L..0
 
Poster Session II : Mario Caironi
17:30
Authors : Te-Hua Fang1,*, Yu-Jen Hsiao2, Shi-Hong Yang1
Affiliations : 1 Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan. 2National Nano Device Laboratories, National Applied Research Laboratories, 741, Taiwan

Resume : In this study the sensing La2O2CO3 nanomaterials were coated on Au/SiO2/Si substrate by electrostatic spray method. The objective being to observe the effects of temperature and concentration of polyvinylpyrrolidone (PVP) on the nanopartiles for sensing the impact of carbon dioxide performance. The results showed that high-resolution transmission electron microscope (TEM) image and energy-dispersive x-ray spectroscopy (EDS) analysis of the La2O2CO3 structure had a polycrystalline structure, and when the polyvinylpyrrolidone polymer concentration was 6 wt%, the sample had a preferable characteristic. When the carbon dioxide at 2000 ppm, the response was close to 18% at 400 ° C. The increase in collection time can make it more responsive to carbon dioxide gas, which improved the gas sensing ability. We expect these results to open up the way towards high performance La2O2CO3 nanomaterials for gas sensors.

L.1.1
17:30
Authors : Yong Tae Kim1, Seong-Il Kim1, F. Gamiz2
Affiliations : 1Semiconductor Materials & Devices Lab, Korea Institute of Science and Technology, Seoul 136-791, Korea 2Departamento de Electronica y Tecnologıa de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada, Spainy

Resume : We will present a simple, cost effective and precisely controllable methods to fabricate high-quality and controllable band gap graphene oxide (GO) films as a hole injection layer (HIL) for high efficiency polymer light-emitting diodes (PLEDs). The electrophoretic deposition (EPD) method and the electrical reduction method to tune the GO to the reduced graphene oxide (RGO) thin films show better luminance and current density for making high efficiency PLEDs by comparing the performance of PLEDs with RGO film as HIL with GO and (poly (3,4-ethylenedioxythiophene) polystyrene sulfonate) (AI4083). Each layer of PLEDs is the non-alkali or non-alkaline earth metals, it facilitates us to fabricate PLEDs in the ambient environment. The thickness of the GO films could be controlled from 80 to 350 A with the EPD system. These deposited GO films were reduced by the electrical method. The GO films with various thicknesses and the RGO films with a different reduction degree were prepared to optimize the film for HIL layer. It has been observed that GO with 80 A thickness followed by 10 s reduction is the best candidate as HIL of PLEDs. The optimum condition could be confirmed by Raman spectroscopy, XPS, UPS and UV–Vis spectroscopy. Finally, we fabricated high efficiency PLEDs using RGO as HIL and compared the performance of the device with AI4083 HIL device. The maximum luminance was 12830 (RGO HIL) and 3,958 cd/m2 (AI4083 HIL). The EPD process and the electrical reduction method are expected to be useful as an industrial approach in fabrication of high efficiency PLEDs.

L.1.3
17:30
Authors : Sebastian Stolz, Yingjie Zhang, Uli Lemmer, Gerardo Hernandez-Sosa, Hany Aziz
Affiliations : Karlsruhe Institute of Technology, Light Technology Institute, Engesserstr. 13, 76131 Karlsruhe, Germany: Sebastian Stolz; Uli Lemmer; Gerardo Hernandez-Sosa. InnovationLab, Speyerer Str. 4, 69115 Heidelberg, Germany: Sebastian Stolz; Gerardo Hernandez-Sosa. University of Waterloo, Department of Electrical and Computer Engineering & Waterloo Institute for Nanotechnology, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada: Yingjie Zhang; Hany Aziz. Karlsruhe Institute of Technology, Institute of Microstructure Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany: Uli Lemmer.

Resume : The fabrication of organic light-emitting diodes (OLEDs) by high-throughput printing techniques requires the development of solution-processable electron injection layers (EILs). Over the last few years, amine-based EIL materials like Polyethylenimine (PEI) have received a lot of attention as they can be used in combination with a multitude of electrode materials in normal as well as inverted device architectures.1–3 In this work, we fabricate solution-processed OLEDs, which use PEI as EIL, and we investigate their performance and operational stability. We show that the cathode metal that is in contact with the EIL plays a crucial role for the operational lifetime of the devices. In case of Al, the primary degradation mechanism during electrical driving is caused by excitons which reach and subsequently degrade the emitter/PEI interface. At a current density of 20 mA cm-2, an LT50 lifetime of ~ 200 h is achieved. In contrast, in case of Ag, an additional mechanism degrades the OLED performance; during operation holes accumulate at the emitter/PEI interface and as a result the emitter quantum yield drops. Consequently, the operational lifetime of such OLEDs is significantly shorter with an LT50 value of < 10 h. Finally, we show that the degradation by excitons can be significantly slowed down by the use of a PEI:ZnO composite EIL. As a result, the LT50 lifetime of OLEDs with an Al cathode is increased by a factor of five, without adversely affecting OLED performance. 1: Zhou et al., Science 2012, 336 (6079), 327–332. 2: Stolz et al., ACS Appl. Mater. Interfaces 2014, 6 (9), 6616–6622. 3: Stolz et al., ACS Appl. Mater. Interfaces 2016, 8, 12959–12967.

L.1.3
17:30
Authors : Akkuzina A.A., Kozlova N.N., Saifutyarov R.R., Khomyakov A.V., Avetisov R.I., Avetissov I.Ch.
Affiliations : Dmitry Mendeleev University of Chemical Technology of Russia

Resume : The new method of nonstoichiometry investigation in the metal-organic (MO) crystalline materials has been developed. Using a quasi-closed ampoule system the method allowed monitoring the changes in fluorescent characteristics of metal–organic samples with temperature, annealing time and partial pressure of ligand-forming substance (pL) in situ. When combined with X-ray analysis the method made it possible to find the conditions for the synthesis of single-phase metal-organic crystalline samples with a certain disordering in the crystal lattice determined by atomic defects similar to the nonstoichiometry phenomenon in classic semiconductors. The influence of pL and temperature on structural and luminescent properties of MO crystalline samples (99.9985 wt%) has been also studied for the samples quenched after annealing’s. It was found that direct changes of pL at the fixed annealing temperature caused the systematic changes of photoluminescent spectra maximum, decay kinetics and structural characteristics. The OLED devices were fabricated by vacuum thermal evaporation using single-phase MO samples with different nonstoichiometry, as emitting materials. It was found that OLED-devices based on nonstoichiometric MO demonstrated improved stability versus OLED based on stoichiometric MO. The research was financially supported by the Russian Foundation for Basic Research (Contract 16-32-60035).

L.1.4
17:30
Authors : Anastasia V. Glushkova, Elena Yu. Poimanova, Vladimir V. Bruevich, Yuriy N. Luponosov, Sergei A. Ponomarenko, Dmitry Yu. Paraschuk
Affiliations : Anastasia V. Glushkova, Vladimir V. Bruevich, Dmitry Yu. Paraschuk - Faculty of Physics & International Laser Centre of Lomonosov Moscow State University, Leninskiye gory 1/62, 119991 Moscow, Russia; Elena Yu. Poimanova - Department of Chemistry of Donetsk National University, Universitetskaya, 24, 83001, Donetsk, Ukraine; Yuriy N. Luponosov, Sergei A. Ponomarenko - N.S. Enikolopov Institute of Synthetic Polymeric Materials of Russian Academy of Sciences, Profsoyuznaya Str. 70, 117393 Moscow, Russia; Sergei A. Ponomarenko - Faculty of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1/3, Moscow 119991, Russian Federation

Resume : Single-crystal organic filed effect transistors (OFETs) can provide electrical performance exceeding that of a-Si devices. Solution-processed devices could be more advantageous enabling low production costs. For industrial applications of organic single crystals, their high morphological homogeneity and thickness uniformity on large areas are needed. As charge transport in OFETs occurs within a few monolayers of organic semiconductor, ultrathin devices are beneficial from the viewpoint of low material consumption, mechanical flexibility and optical transparency. Herein, we report on solution-processed oligothiophene-based monolayer single crystals with sizes up to a few mm and study their performance as OFET active layers. As materials we used oligothiophenes and oligothiophene-phenylenes with five conjugated rings and different terminal linear alkyl substituents, which were proved to be crucial for 2D crystallization in monolayers. The monolayer single crystals were grown on various surfaces, both with high and low surface energies, and studied by optical polarization microscopy, atomic-force microscopy, spectroscopic ellipsometry, and x-ray diffraction. Our in situ studies of crystal growth allowed us to suggest a possible growth mechanism. The OFET mobility was increased tenfold with use of oligomers with longer alkyl substituents. The best devices showed the charge mobility exceeding by an order of magnitude the highest reported mobilities for oligothiophene-based monolayer OFETs [1]. Thus, large-area solution-processed monolayer single crystals can be a promising platform for ultrathin organic electronic field-effect devices. 1. Smits E.C.P., et al., Nature, 2008, v.455 p.956.

L.1.4
17:30
Authors : Thomas R. Hopper, Jianhui Hou, Deping Qian, Feng Gao and Artem A. Bakulin
Affiliations : Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom; State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden; Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-58183, Sweden; Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom

Resume : The development of new materials with tunable optoelectronic properties is key to the continued evolution of organic photovoltaics (OPV). In this work, we present a novel push-pull molecule composed of acceptor (A) moieties bonded to each side of a donor (D) core (A-D-A). By making subtle changes to the position of octyl groups on the alkylthiophene-substituted benzodithiophene (BDT) D core, the overall D or A character of the molecule can be changed. Here we compare two regioisomers, oBDT and mBDT, which were individually blended with a well-studied D or A; namely the polymer PBDTBDD (P141) or the fullerene PC71BM, respectively. The four “D:A” pairings (P141:oBDT, P141:mBDT, oBDT:PC71BM and mBDT:PC71BM) were integrated into bulk heterojunction OPV devices, and their photophysics was studied using photoluminescence (PL), transient absorption and pump-push photocurrent techniques. Of the four devices, the highest short-circuit current and power conversion efficiencies were obtained from the oBDT:PC71BM and P141:mBDT blends. In correlation with device performance, we observe efficient charge separation in these two blends in contrast to mBDT:PC71BM and P141:oBDT. These results indicate that oBDT has more D character, while mBDT has more A character. We speculate that the position of the bulky octyl groups sterically influences the degree of ‘twisting’ between the D and A units, thereby changing the extent of conjugation, and hence photophysical behaviour, of the A-D-A molecule.

L.1.6
17:30
Authors : Riccardo Di Pietro(a), Tim Erdmann(b), Joshua Carpenter(c), Harald Ade(c), Dimitri Ivanov(d), Anton Kiriy(b) and Dieter Neher(e)
Affiliations : (a) Hitachi Cambridge Laboratory, CB3 0HE Cambridge, United Kingdom (b) Leibniz-Institut für Polymerforschung Dresden e.V. (IPF), Hohe Straße 6, 01069 Dresden, Germany (c) North Carolina State University, Raleigh, NC 27695, United States of America (d) Lomonosov Moscow State University, GSP-1, 1-51 Leninskie Gory, Moscow, Russia (e) Universität Potsdam, 14476 Potsdam, Germany

Resume : We present an in-depth study of the correlation between molecular weight, processing conditions and charge transport in high molecular weight diketopyrrolopyrrole copolymers. We observe a rapid increase in aggregation in solution with increasing molecular weight which strongly limits solubility and processability beyond MW = 200 kg mol-1, causing severe limitation in the charge transport properties. We also isolate the presence of bulk electronic defects manifest itself as an apparent charge density dependence of the mobility. High molecular weight polymer chains are already obtained after as little as 15 minutes of reaction time and by limiting aggregation they allow the formation of highly textured films. Defects are passivated by exposure to ambient atmosphere or by chemical doping using 2,2-(perfluoronaphthalene-2,6-diylidene)dimalononitrile, which leads to a filling of the trap states.[1] By combining fast reaction times without further washing steps (partially responsible for the formation of trap sites) we are able to achieve high and balanced hole and electron transport, among the best reported for an isotropic, spin coated DPP polymers. [1] Di Pietro, R. et al. (2016), The impact of molecular weight, air exposure and molecular doping on the charge transport properties and electronic defects in dithienyl-diketopyrrolopyrrole-thieno[3,2-b]thiophene copolymers. J. Mater. Chem. C, 4, 10827 doi: 10.1039/c6tc03545k

L.1.7
17:30
Authors : Kazuki Kudo, Hirokazu Yano, and Hidenori Okuzaki
Affiliations : Graduate Faculty of Interdisciplinary Research, University of Yamanashi; Graduate Faculty of Interdisciplinary Research, University of Yamanashi and Organic Materials Research Lab., Tosoh Corporation; Graduate Faculty of Interdisciplinary Research, University of Yamanashi

Resume : The organic electronics originated from low cost, lightweight, and flexible electronics is developing through the printed electronics, stretchable electronics, and recently into wearable electronics for the applications to flexible displays, touch panels, soft sensors and actuators. Here, wet-processable, stretchable, and highly conducting polymer is one of the promising candidates for the key materials of the organic electronics. Poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonic acid) (PEDOT:PSS) is one of the most successful conducting polymers which can be applied to the electrical and optical devices such as antistatic coatings, aluminum solid capacitors, organic light-emitting diodes, and solar cells. However, there are still technical issues for the practical applications: The PEDOT:PSS is available in the form of an aqueous dispersion of colloidal particles, which is disadvantageous to form an ultra-thin layer in the molecular order and to fill into an etching pit of the aluminum solid capacitors. Moreover, the “solvent effect” is necessary to improve the electrical conductivity by a few orders of magnitude, the mechanism of which can be explained in terms of the crystallization of the PEDOT molecules and the removal of an excess PSS from the surface of the colloidal particles preferable to the transport of charge carriers. This study deals with synthesis and characterization of novel self-doped highly conducting polymers. The oxidative polymerization of the derivatized EDOT monomer, in which the ethylenedioxy ring is substituted with an alkoxy sulfonate group, was carried out under vigorous stirring at room temperature for 24 h. The dark blue aqueous solution of the self-doped PEDOT (SD-PEDOT) was obtained with concentration, viscosity, and pH of 1.0 wt%, 22.4 mPas, and 1.9, respectively. It is seen that the dynamic light scattering measurement clearly indicates the narrow particle size distribution of the SD-PEDOT with the average diameter (median diameter: D50) of 2.5 nm. We should emphasize here the D50 of the SD-PEDOT is much smaller compared to the PEDOT:PSS colloidal gel particles (D50 = 16 nm), suggesting that the SD-PEDOT is fully dissolved in water. Surprisingly, the electrical conductivity of the SD-PEDOT film was found to be 875 S/cm, which is comparable to the most conductive PEDOT:PSS (Clevios PH1000, Heraeus). Thus, we have succeeded in synthesizing the water-soluble self-doped highly conducting polymers.

L.1.8
17:30
Authors : Deepak Bhat, Sanjoy Jena, Debdutta Ray
Affiliations : Department of Electrical Engineering, Indian Institute of Technology (IIT) Madras, Chennai-600036, India

Resume : In this work, we study Chemical Vapor Deposition (CVD) as an alternate route for polymer film deposition in order to achieve non-solution based organic optoelectronic devices. Polymer semiconductors are generally deposited by spin coating from a solution. Spin coating is not feasible for up-scaling. The conventional route for up-scaling, which uses a printing/coating technology, yields films with inferior electronic properties compared to spin coated films. Poly (p-phenylene vinylene) (PPV) is a polymer with high absorption in the blue to green region of the electromagnetic spectrum and hence has the potential to be used as an active material in solar cells. CVD allows good control over the deposition of the film. The film grown is a pre-polymer and can be polymerized by annealing or by exposure to UV light. Since the deposition is at room temperature and polymerization post growth can be done by UV treatment, it is possible to deposit the film on flexible substrates. We study the electrical properties of the CVD grown PPV using field effect transistors. CVD grown PPV shows good transistor characteristics. Realization of organic field effect transistors based on CVD of PPV is being demonstrated for the first time. The electrical characteristics of the film with various post growth treatments are studied. We investigate the gate bias dependent mobility of the PPV films. We model the carrier dependent mobility to understand charge carrier transport in CVD grown PPV.

L.1.9
17:30
Authors : Morgane Diebold, Elliot Christ, Laure Biniek, Benoît Heinrich, Sadiara Fall, Suhrit Ghosh, Philippe Mesini and Martin Brinkmann
Affiliations : Institut Charles Sadron, 23 rue du Loess, 67034 Strasbourg, France. Email: morgane.diebold2@etu.unistra.fr; Institut de Physique et Chimie des Matériaux de Strasbourg, 23 rue du Loess, 67034 Strasbourg, France ; ICube, 23 rue du Loess, 67034 Strasbourg, France; Indian Association for the Cultivation of Science, Polymer Science Unit, 2A & 2B Raja S. C. Mullick Rd., Kolkata, India.

Resume : Rylene diimides form a unique and interesting class of organic semiconductors showing for instance n-type behavior in OFETs or high luminescence of interest for sensor applications. The electronic and optical properties of rylene diimide molecules can be tuned by molecular engineering and adequate choice of substituents. But, in the solid state, their collective properties depend on the molecular packing. For instance, they can form different polymorphs made of either J- or H-type aggregates, as observed for perylene bisimide derivatives*. In this case, a competition between H-bonding and π - π stacking interactions determines the polymorphism, hence the electronic properties in the solid state. In the present study, we have studied a naphthalene-bisimide based organogelator named NDIC8. We have correlated the structure, especially polymorphism, with optical and electronic properties in the solid state. Three polymorphs were prepared: gel, liquid crystalline and crystalline phases and their molecular packing was investigated by X-ray and electron diffractions. The UV-vis and Infra-red spectra of the NDIC8 polymorphs uncover the nature of intermolecular H-bonding between amides. Temperature-dependent TEM, UV-vis and FTIR help understand the molecular reorganization upon transformation between the different polymorphs. Finally, a global phase diagram has been obtained. * A. Sarbu, L. Biniek, J.M. Guenet, P.J. Mesini, M. Brinkmann, J. Mater. Chem. C., 2015, 3, 1235-1242

L.1.10
17:30
Authors : Michele Giorgio, Andrea Perinot, Mario Caironi
Affiliations : Center for Nano Science and Technology (CNST) of Italian Institute of Technology (iit) and Politecnico di Milano

Resume : Organic electronics is gaining more and more attention from scientific public and from industries because of his unique properties such as flexibility, transparency, and solution-processability. High throughput manufacturing methods such as roll-to-roll coating and inkjet printing allow organic electronics to be suitable for new and diverse applications and to be an attractive viable way to make low cost electronics. Before employing this technology for the production of complex circuits, the performance of the elementary block, i.e. the transistor, has to be optimized. This task is nowadays favored by the recent improvements in polymers charge carrier mobility. The willingness to fabricate transistors capable of high frequency operation is spurred by possible applications like high-resolution flexible displays or devices able to communicate via wireless. Nevertheless, a record frequency of transition of 27 MHz is achieved for transistors with lithographic contacts and evaporated semiconductor, while of 3 MHz for transistors fabricated without using masks in the production flow. In order to reach an high frequency operation preserving the advantages of the low cost manufacturing methods discussed before, not only the chemistry of the polymers but also the device architecture should be optimized. The latter problem is the subject of my thesis work. The channel length was downscaled in maskless approach by means of laser sintering technique, down to a minimum of 1 um. The semiconductor layer was deposited with a large-area, roll-to-roll compatible coating technique which optimizes charge transport and the effects of contacts treatments and of semiconductor doping were investigated. The overlap capacitance, another critical factor in limiting the frequency of transition, was minimized by reducing the finger widths of the contacts again relying on a laser sintering technique. Mobilities of 0.07 cm^2/Vs for holes and 0.3 cm^2/Vs for electrons were extracted for a downscaled transistors channel of 1 um, and a frequency of transition of 3 MHz and 10 MHz was found for p-type and n-type OFETs. Such frequencies are among the highest ever achieved for solution-processed polymer FET fabricated with a completely maskless approach.

L.1.10
17:30
Authors : P.Lhéritier
Affiliations : CEA GRENOBLE

Resume : PVDF-TRFE based terpolymers such as PVDF-TRFE-CTFE (VDF: vinylidene fluoride, TRFE: trifluoroethylene, CTFE: chlorotrifluoroethylene) present an important electromechanical response, making of them interesting candidates for actuation based devices. Before considering industrial applications, the deformation of the material while submitted to an activation input signal has to be determined. However for frequencies below a few dozens of Hertz, the electrostriction equation linking polarization to the mechanical deformation doesn’t describe the physical reality correctly. The device behavior is modified by leakage currents, ions movement and viscoelastic response. Based on the electrical and mechanical response in a static regime, a mathematical model of polarization response in dynamic regime is proposed. The quantification of the different components of the electrical device response permits afterwards a correct prediction of the low frequency mechanical deformation of the polymer based devices. Applying experimentally different test signals to a cantilever and measuring the device response, allows then the comparison of the measured device response to the modeled material deformation.

L.1.11
17:30
Authors : Rakibul Islam, Roch Chan-Yu-King, Carole Gors, and Frederick Roussel
Affiliations : University of Lille- Sciences and Technologies, Unité Matériaux et Transformations (UMET) – UMR CNRS 8207, UFR de Physique, Bat P5, 59655 Villeneuve d’Ascq, France,University of Science and Arts of Oklahoma, Chickasha, OK 73018, USA, University of Lille- Sciences and Technologies, Unité Matériaux et Transformations (UMET) – UMR CNRS 8207, UFR de Physique, Bat P5, 59655 Villeneuve d’Ascq, France,University of Lille- Sciences and Technologies, Unité Matériaux et Transformations (UMET) – UMR CNRS 8207, UFR de Physique, Bat P5, 59655 Villeneuve d’Ascq, France

Resume : In this study, polyanilines (PANI)/single wall carbon nanotubes (SWCNT), PANI/ multi wall carbon nanotubes (MWCNT), and PANI/reduced graphene oxide (RGO) nanocomposites are synthesized via in situ polymerization. The core-shell structures are evidenced by SEM and TEM images whereas XRD and Raman spectroscopy are employed to investigate structural properties. In addition, electrical, thermal and thermoelectric (TE) transport properties are investigated as a function of nano-fillers content. The power factor and figure of merit (ZT) of the composites are deduced from measurements of the electrical conductivity (σ), Seebeck coefficient (S) and thermal conductivity (k). The electrical transport properties are explained by using mixing rule and percolation model. Effective mass approximation (EMA) model is used to explain the thermal properties. It is shown that inclusion of the three different kinds of fillers into polymer matrix exhibits three different behaviors which are explained by an existing physical model. Compared to that of pure PANI, the TE performance of the composites exhibits a ZT enhancement of few orders of magnitude.

L.1.12
17:30
Authors : Manuel Gruber, Fatima Ibrahim, Samy Boukari, Loïc Joly, Victor Da Costa, Michal Studniarek, Moritz Peter, Hironari Isshiki, Hashim Jabbar, Vincent Davesne, Jacek Arabski, Edwige Otero, Fadi Choueikani, Kai Chen, Philippe Ohresser, Wulf Wulfhekel, Fabrice Scheurer, Eric Beaurepaire, Mebarek Alouani, Wolfgang Weber and Martin Bowen
Affiliations : Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, Strasbourg, France Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany Synchrotron SOLEIL, Gif-sur-Yvette, France

Resume : The organic spinterface describes the spin-polarized properties that develop, due to spin-dependent hybridization and charge transfer, at the interface between a ferromagnetic (FM) metal and the molecules of an organic semiconductor [1,2]. The organic spinterfaces were also indirectly observed by the strong coupling that may exist between paramagnetic molecules and the FM substrate [3-6]. However, the study of spinterfaces was so far limited to sublimable molecules deposited in ultra-high vacuum conditions in order to prevent the oxidation of the FM substrate. Alternatively, the strong interaction of the molecules with the FM layer may alter molecular properties, such as spin-crossover [7]. While intercalating a graphene layer [8] is one solution that introduces strong constraints on the FM selection, we investigated the possibility to use interlayer exchange coupling as the mediator of the molecule/FM magnetic coupling. Using X-ray magnetic circular dichroism (XMCD), we studied the magnetic coupling between manganese phthalocyanine (MnPc) molecules and a Cu(001)/Co FM substrate separated by a wedge-shaped Cu spacer. The XMCD data show that the Mn ion within MnPc molecules can be magnetically coupled to the Co substrate at room temperature when separated by up to 4 ML of Cu. The XMCD intensity evolves in an oscillatory manner with increasing Cu thickness, in agreement with ab initio calculations. By decreasing the temperature, we could observe stronger oscillations in the magnetic coupling and this over a much larger Cu thickness range (up to 12 ML). The phase and the periods of the oscillatory coupling is found to be the same than that of the prototypical Cu(001)/Co/Cu/Co system. Finally, we theoretically considered the spintronic performance of a Co/Cu(3ML)/MnPc stack. The calculations reveal a spin-polarization of the density of states in the vicinity of the Fermi level that reaches +74% suggesting thus promising spintronic performance [9]. [1] Methfessel et al., Physical Review B 84, 224403 (2011) [2] Djeghloul et al., Scientific Reports 3, 1272 (2013) [3] Scheybal et al., Chemical Physics Letters 411, 214 (2005) [4] Wende et al., Nature Materials 6, 516 (2007) [5] Javaid et al., Physical Review Letters 105, 077201 (2010) [6] Iacovita et al., Physical Review Letters 101, 116602 (2008) [7] Miyamachi et al., Nature Communications 3; 938 (2012) [8] Hermanns et al., Advanced Materials 25, 3473 (2013) [9] Gruber et al., Nano Lett. 15, 7921 (2015)

L.1.12
17:30
Authors : Parrenin, L.; Prunet, G.; Fleury, G.; Brochon, C.; Pavlopoulou, E.; Hadziioannou, G.; Cloutet, E.
Affiliations : [1] Université de Bordeaux, Laboratoire de Chimie des Polymères Organiques (LCPO), UMR 5629, B8 Allée Geoffroy Saint Hilaire, F‐33615 Pessac Cedex, France [2] Centre National de la Recherche Scientifique (CNRS) ,Laboratoire de Chimie des Polymères Organiques (LCPO), UMR 5629, B8 Allée Geoffroy Saint Hilaire, F‐33615 Pessac Cedex, France [3] Institut National Polytechnique de Bordeaux (INP Bordeaux), Laboratoire de Chimie des Polymères Organiques (LCPO), UMR 5629, B8 Allée Geoffroy Saint Hilaire, F‐33615 Pessac Cedex, France

Resume : Organic conducting polymers are of increasing scientific interest and are promising candidates for various applications [1]. Nowadays, one the most important challenges faced by the community concerns their processability along with their long term stability. In this context, herein, I'd like to present one approach consisting in the preparation of photoactive materials stable as inks in environment-friendly phases through miniemulsification or nanoprecipitation techniques [2-3]. For instance, composite particles made of the low band-gap PCDTBT polymer together with the n-type PC71BM have been prepared in aqueous media. The materials ratio was varied and the properties of composite particles were studied along with their integration. (1) Skotheim, T. A.; Reynolds, J. R. Handbook of Conducting Polymers, CRC Press, NY, 2007, 1680 pages. (2) Cloutet, E. and coll. Macromol. Rapid Commun. 2015, 36(20), 1816-1821. (3) Cloutet, E. and coll. Langmuir 2017 under revision.

L.1.13
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Transistors I : Wouter Maes, Paul Blom, Carsten Deibel
08:30
Authors : Yong-Young Noh
Affiliations : Department of Energy and Materials Engineering, Dongguk University

Resume : For at least the past 10 years, printed electronics has promised to revolutionize our daily life by making cost-effective electronic circuits and sensors available through mass production techniques, for their ubiquitous applications in wearable components, rollable and conformable devices, and point-of-care applications. While passive components, such as conductors, resistors and capacitors, had been already fabricated by printing techniques at industrial scale, despite the great potentiality, printing processes have been struggling to meet the requirements for mass-produced electronics and optoelectronics applications. In the case of logic integrated circuits (ICs), the main limitations have been represented by the need of suitable functional inks, mainly high-mobility printable semiconductors and low sintering temperature conducting inks, and evoluted printing tools capable of higher resolution, registration and uniformity than needed in the conventional graphic arts printing sector. In this presentation, I will give a talk on the recent progressive of my group on development of printed organic integrated circuits. I will mainly talk about on development of high performance inkjet printed unipolar and ambipolar polymer field-effect transistors (FETs), and applications to elementary organic complementary inverter, ring oscillators and various logic circuits. Several issues should be addressed including method to improve charge injection properties, reducing operating voltage, and deposition over a large area by graphic art printing processes. By development of organic semiconductors and gate dielectrics, printing processes, contact resistance, and mobility of organic semiconductors, we have obtained high field-effect mobility more than 6 cm2/Vs for both of p-channel and n-channel FETs with less than 5 V operating voltage, and ambipolar OFETs and the CMOS polymer ring oscillator showed very high operating frequency of 50 KHz. In addition, various logic circuits were demonstrated.

L.1.1
09:00
Authors : Hakan Usta, Mehmet Ozdemir, Choongik Kim, Donghee Choi, Antonio Facchetti
Affiliations : Hakan Usta; Mehmet Ozdemir: Department of Materials Science and Nanotechnology Engineering, Abdullah Gül University, Kayseri 38080, Turkey Choongik Kim; Donghee Choi: Department of Chemical and Biomolecular Engineering, Sogang University, Mapo-gu, Seoul 121-742, Korea Antonio Facchetti: Polyera Corporation, 8045 Lamon Avenue, Skokie, Illinios 60077, United States

Resume : π-conjugated electron-deficient molecules have demonstrated great potential as n-channel semiconductors for the realization of cost-effective and flexible printed optoelectronic devices. Over the past few decades, considerable research efforts have focused on the theoretical design and synthetic development of various families of electron-transporting molecular semiconductors with a wide range of electrical and optical properties. To this end, 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) stays as a relatively unexplored π-core for use in semiconductor structures, despite it has been heavily studied in the past decades as highly fluorescent functional dyes for chemosensors, fluorescent switches and biochemical labels. Here, we describe the molecular design, synthesis, full characterization, and OTFT device performance of novel solution-proccessable BODIPY-based small molecules for organic thin-film transistors (OTFTs). Solution-processed top-contact/bottom-gate OTFTs exhibited electron mobilities as high as 0.01 cm2/V·s and extremely high current on/off ratios of >108. Film microstructural and morphological characterizations indicate the formation of relatively long (~0.1 mm) and micron-sized (1-2 μm) crystalline fibers and ribbons along the shearing direction. To the best of our knowledge, these OTFT performances are the highest reported to date (~10-1000× improvement) for BODIPY-based molecular semiconductors, and our findings demonstrate that BODIPY core holds great promise to become a key player for enabling solution-processed, electron-transporting semiconductor films.* * M. Ozdemir, D. Choi, G. Kwon, Y. Zorlu, B. Cosut, H. Kim, A. Facchetti*, C. Kim*, H. Usta* "Solution-Processable BODIPY-Based Small Molecules for Semiconducting Microfibers in Organic Thin-Film Transistors" ACS Applied Materials & Interfaces, 2016, 8, 14077–14087. Acknowledgements: This work is supported by the Scientific and Technological Research Council of Turkey (TUBITAK Grant-114M226)

L.1.2
09:15
Authors : Riccardo Di Pietro (1), Iyad Nasrallah (2), Joshua Carpenter (3), Eliot Gann (4), Lisa Sophie Kölln (5), Lars Thomsen (6), Deepak Venkateshvaran (2), Kathryn O’Hara (7), Aditya Sadhanala (2), Michael Chabinyc (7), Christopher R. McNeill (4), Antonio Facchetti (8), Harald Ade (3), Henning Sirringhaus (2), and Dieter Neher (5).
Affiliations : 1) Hitachi Cambridge Laboratory, CB3 0HE Cambridge, United Kingdom 2) University of Cambridge, CB3 0HE Cambridge, United Kingdom 3) North Carolina State University, Raleigh, NC 27695, United States of America 4) Monash University Wellington Road, Clayton, Victoria 3800, Australia 5) Universität Potsdam, 14476 Potsdam, Germany 6) Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia 7) University of California Santa Barbara Santa Barbara, CA 93106-5050, USA 8) Polyera Corporation, 8045 Lamon Ave, STE 140, Skokie, IL 60077-5318, USA

Resume : We present a study on charge transport on two widely used semiconducting polymers, poly{[N,N′-bis(2-octyl- dodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5′-(2,2′- bithiophene)} (P(NDI2OD-T2)) and poly(3-hexylthiophene) (P3HT). [1] The electrical characterisation of field effect transistors reveals an increase in charge density dependence of the mobility connected to an overall improvement of device performance. We unambiguously tie such observation to the increase of the average crystallite size of the polymer film by combining the results of optical spectroscopy and X-ray characterization. The picture that emerges from the experimental evidence demonstrates that charge transport in semicrystalline polymers cannot be described using any disorder based model such as for example multiple trap and release or variable range hopping. To explain the experimental observation we propose a mechanism that explicitly accounts for the presence of interdispersed crystalline and amorphous regions within the polymer film and for the Coulomb interaction between charge carriers accumulated within the same crystallite. With this approach we are able to provide a coherent picture of charge transport that can capture all the unique features we observed experimentally. [1] Di Pietro, R. et al. (2016), Coulomb Enhanced Charge Transport in Semicrystalline Polymer Semiconductors. Adv. Funct. Mater., 26, 8011, doi:10.1002/adfm.201602080.

L.1.3
09:30
Authors : Vivek Subramanian, Gerd Grau, Hongki Kang, and Rungrot Kitsomboonloha
Affiliations : EECS Department, University of California, Berkeley

Resume : Recent advances in gravure printing allow realization of highly-scaled fully printed transistors with channel lengths in the single micron range. The ability to realize such transistors requires a complete re-working of the transistor structure and process, including development of layouts that exploit the improved resolution while dealing with substrate distortion induced overlay limitations, as well as realization of aggressive scaling of all printed layers to improve electrostatics in such highly scaled OTFTs. Here, I review our work on scaling gravure printing resolution, and the accompanying changes in device structure and material choices to enable realization of high-performance fully-printed organic thin film transistors based on leading edge gravure printing technology

L.1.4
10:00 Coffee break    
10:30
Authors : Hung Phan, Ming Wang, Michael Ford, Guillermo C. Bazan, Thuc-Quyen Nguyen
Affiliations : Department of Chemistry and Biochemistry, University of California Santa Barbara

Resume : Polymer field effect transistors (PFETs) have potential applications in large-area flexible displays, sensors, radiofrequency identification tags, and logic circuits with low-cost processability. However, they are still inadequate for commercialization and practical implementation due to their operational instability. We investigated the mechanism of the electrical instability of high performing PFETs that show a certain degree of ambipolarity and unraveled the effect of electron conduction on the stability of hole current and the double-slope behavior. The model polymer used in this study is regioregular D-A copolymer poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] (PCDTPT). While performing current-voltage measurement, we found that consecutive sweeping of gate voltage changed the shape of the transfer curves. We conducted a thorough study of bias-stress of the system and found that electron trapping at the gate dielectric/polymer interface greatly alters the device characteristics including the occurrence of the double-slope. We provide several solutions to improve the device operational stability.

L.1.5
11:00
Authors : Yong Xu, Huabin Sun, Yong-Young Noh
Affiliations : Dongguk University, Department of Energy and Materials Engineering, 30 Pildong-ro, 1-gil, Jung-gu, Seoul 04620, Republic of Korea

Resume : Conjugated polymers recently made great progress in building organic electronics. Nonetheless, the conventionally processed polymer transistors face challenges to develop high-performance devices and our understanding of them remains very limited. Here we present planar-processed polymer transistors using the promising donor-acceptor (D-A) copolymers, which are enabled by a planar ohmic contact engineering like that used for silicon metal-oxide-semiconductor field-effect transistors (MOSFETs). These novel polymer transistors exhibit ideal p-FET characteristics with unparalleled performance. In particular, the lowest subthreshold slope observed of 85 mV/dec approaches the theoretical limit of 60 mV/dec at room temperature given simple solution-based processes. Our results shed light on the ambiguous operating principle of ambipolar OFETs and demonstrate the versatility in doping D-A copolymers, thereby paving a clear path toward the practical application of polymer transistors.

L.1.6
11:15
Authors : Ana Pérez-Rodríguez, Inés Temiño, Marta Mas-Torrent, Carmen Ocal, Esther Barrena
Affiliations : Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), 08193-Bellaterra (Spain)

Resume : Blending small conjugated molecules as organic semiconductor with an amorphous insulating polymer has been demonstrated to improve the organic field effect transistors (OFETs) processability, reproducibility and stability.[1-2] The key at the basis of the superior performance of OFETs fabricated with blended films seems to be the vertical phase separation of the two components. Thus, deciphering the vertical stratification of the blends and how it changes as a function of the processing parameters is of fundamental importance. This issue is addressed here for blends of 2,7-Dioctyl[1]benzothieno[3,2–b][1]benzothio-phene (C8-BTBT), a promising organic semiconductor with some of the highest mobilities reported to date, and polystyrene (PS) processed by a solution-shearing technique.[2] We show that Friction Force Microscopy can be used to discriminate pure C8-BTBT and PS regions due to their different frictional behavior, allowing us to obtain a nanoscale characterization of their lateral and vertical distribution. The deciphered vertical structure has been correlated with the macroscopic electrical performance of the OFETs for three ratios of C8-BTBT and PS. In addition, Kelvin Probe Force Microscopy measurements help quantifying the electrical potential along the channel during operation of the OFETs and contacts-related effects. [1] M. R. Niazi et al. Nat. Commun. 6, 8598 (2015). [2] I. Temiño et al. Adv. Mater. Technol. 1, 1600090 (2016).

L.1.7
11:30
Authors : Hagen Klauk
Affiliations : Max Planck Institute for Solid State Circuits

Resume : Organic thin-film transistors (TFTs) can typically be fabricated at temperatures below 150 °C and thus not only on glass, but also on unconventional substrates, such as plastics, paper and textiles, which makes them potentially useful for flexible, large-area electronics applications, such as rollable or foldable displays and sensors. In some of the more advanced applications envisioned for organic TFTs, such as the integrated row and column drivers of flexible active-matrix displays, the TFTs have to be able to control electrical signals of a few volts at frequencies of several megahertz. The first requirement for achieving high switching frequencies is efficient charge transport in the semiconductor. This requirement can be met by choosing small-molecule organic semiconductors that provide good molecular ordering and large carrier mobilities even when processed at low temperatures. The second requirement is a small channel length. To meet this requirement, we have developed a process in which the TFTs are patterned using high-resolution silicon stencil masks, which makes it possible to fabricate bottom-gate, top-contact organic TFTs with a channel length of 1 µm. For 11-stage complementary and unipolar ring oscillators based on TFTs with a channel length of 1 µm, signal propagation delays per stage as short as 6.6 µs and 420 ns have been measured at a supply voltage of 3 V.

L.1.8
12:00 Lunch    
 
OLEDs and Optical Devices : Yong-Young Noh, Vivek Subramanian, Thuc-Quyen Nguyen
14:00
Authors : Naresh Kotadiya1, Davood Abbaszadeh2, Irina Crăciun1, Paul Blom1, and Gert-Jan Wetzelaer1
Affiliations : 1 Max-Planck-Institut für Polymerforschung, Mainz, Germany. 2 Zernike Institute for Advanced Materials, University of Groningen, Netherlands

Resume : A fundamental disadvantage of semiconducting polymers is that their charge transport is unbalanced because electron transport is hindered by traps. This electron trapping seems to be universal in organic semiconductors and is dominated by a trap located at ~3.6 eV below vacuum. This universal defect also quenches the excitons in conjugated polymers. However by blending poly(p-phenylene vinylene) (PPV) derivatives with wide band gap polymers the electron traps are deactivated. PLEDs made from such a blend exhibit a balanced transport and enhanced efficiency due to the strong reduction of non-radiative trap-assisted recombination. An important question is whether the strong electron trapping is specific for polymers or is also present in films from evaporated small molecules. To this end electron transport in a series of small molecules has been studied. It is found that also for a range of small molecules the electron transport is severely limited by traps with a concentration of ~1024 m-3. This indicates that electron trapping is a generic property of organic semiconductors, ranging from vacuum-deposited small-molecules to solution-processed conjugated polymers.

L.1.1
14:30
Authors : L. Basiricò, A. Ciavatti, T. Cramer, P. Cosseddu, A. Bonfiglio, B. Fraboni
Affiliations : University of Bologna – Department of Physics and Astronomy, viale Berti Pichat 6/2, Bologna, Italy University of Cagliari – Department of Electrical and Electronic Engineering, Piazza d’Armi, Cagliari, Italy

Resume : The research interest on alternative materials for innovative ionizing radiation detection is rapidly growing, in particular to envisage the need of large-area conformable sensor flat panels for applications that span from cultural heritage preservation to the security of public buildings. Organic materials have a strong potential for such an application, thanks to their mechanical flexibility and the possibility of deposition over large and bendable substrates by means of low-cost wet-technologies as printing techniques. Therefore, these feature permits to overcome the constraint of traditional inorganic materials, i. e. expensive or complex growth techniques and stiff mechanical properties. Recently, the employment of solution-grown organic materials as reliable direct X-ray detectors, operating at room temperature, have been demonstrated [1,2]. These studies opens the way to the development of a new class of fully flexible organic-based direct detectors with higher performances. In this work, we will report about results on organic thin-films based, fully bendable, devices as direct X-ray detectors, obtaining sensitivity values up to several hundreds of nC/Gy at ultra-low bias of 0.2 V. An analytical model accounting the signal amplitude and sensitivity values achieved and describing the mechanisms of collection and transport of the X-ray generated charges have been also developed. Finally, we assessed the possibility to use the detector under mechanical strain and gave the first demonstration of a 2×2 pixelated matrix organic detector. [1] A. Ciavatti, E. Capria, A. Fraleoni-Morgera, G. Tromba, D. Dreossi, P.J. Sellin,P.Cosseddu, A.Bonfiglio, B. Fraboni : Advanced Materials 27 7123 (2015) [2] L.Basiricò, A.Ciavatti, T.Cramer, P.Cosseddu, A.Bonfiglio, B.Fraboni : Nature Communications 7,13063 (2016)

L.1.2
14:45
Authors : Kwon-Hyeon Kim1, Jia-Ling Liao2, Chang-Ki Moon1, Hyo Jung Kim3, Yun Chi2, Jang-Joo Kim1
Affiliations : 1. Department of Materials science and engineering, Seoul National University, Seoul, Korea (the Republic of). 2. Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan. 3. Department of Organic Material Science and Engineering, Pusan National University, Busan, Korea (the Republic of).

Resume : Recently, the emitting dipoles with perfect horizontal orientation parallel to the substrate result in the theoretical external quantum efficiency (EQE) limit over 45% without any extra light extraction structures compared to 25~30% for randomly oriented emitting dipoles. Large effort has been poured to increase the horizontal emitting dipole ratio (Θ) to get 70~82%. However, it will be difficult to obtain an even higher Θ due to the amorphous nature of typical emitting layers. In this regard, organic crystals would be the better emitters because of the orientational and positional ordering. However, organic crystals have rarely been used for OLEDs due to low stability and efficiency. In this work, we realized a crystal OLED with unprecedented high EQE of 38.8% using the perfectly oriented Pt based thin film emitting layer possessing PLQY of 96% and Θ of 93%. We investigated the emitting dipole orientation of the thin films fabricated using Pt complexes and discussed the structural relationship between X-ray structural analyses and structures in thin films based on quantum chemical calculations. The emitting dipole orientation of the crystal emitting layers was largely affected not only by the crystallinity of the emitting layer but also by the molecular arrangement in the crystal. (K.-H. Kim, J.-J. Kim et al. Adv. Mater. 2016, 28, 2526)

L.1.3
15:00
Authors : Noah Strobel, Ralph Eckstein, Uli Lemmer, Gerardo Hernandez-Sosa
Affiliations : Noah Strobel; Ralph Eckstein; Uli Lemmer; Gerardo Hernandez-Sosa: Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany Noah Strobel; Ralph Eckstein; Uli Lemmer; Gerardo Hernandez-Sosa: InnovationLab, Speyerer Strasse 4, 69115 Heidelberg, Germany: Uli Lemmer: Institute of Microstructure Technology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany:

Resume : Organic photodiodes (OPDs) have been under major investigation for the past years, as they enable low cost fabrication of sensor systems for imaging, medical or industrial applications. While the device performance regarding responsivity and detectivity is continuously improving, the increase in detection speed still lacks behind. One of the major limiting factors can be attributed to trapping and detrapping effects. Especially for low light intensities, the bandwidth is strongly influenced by the lower generation of free charges. Interface and interlayer engineering can be used to reduce these effects. Unfortunately, this burdens the fabrication by printing processes since additional steps and layers are necessary. In this work, we are following an approach of blending insulating polymers into a P3HT:PCBM-system, which has already shown beneficial effects in OFETs or OSCs. The device stack corresponds to the inverted structure and is fabricated solely based on materials allowing for fully printed OPDs. Starting from a basic morphological study using PMMA with different molecular weights, we examined both the steady-state and dynamic characteristics of the OPDs. Transient photocurrent measurements show that the inclusion of PMMA results in an increase of the 3dB-bandwidth without adversely affecting steady-state performance under illumination or in the dark. This increase is attributed to a reduced trap density in higher ordered P3HT when PMMA is present.

L.1.4
15:15
Authors : Francesco Zinna, Mariacecilia Pasini, Francesco Galeotti, Chiara Botta, Lorenzo Di Bari; Umberto Giovanella
Affiliations : M. Pasini, F. Galeotti, C. Botta, U. Giovanella Istituto per lo Studio delle Macromolecole (ISMAC), CNR, Via A. Corti 12, 20133 , Milano, Italy F. Zinna, L. Di Bari Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, I-56124 Pisa, Italy

Resume : Organic Light-Emitting diodes (OLEDs) able to directly emit circularly polarized (CP) electroluminescence (CP-OLEDs) are gaining much interest, due to their possible applications in anti glaring screens, 3D-displays and in medical diagnosis. We have recently demonstrated that chiral lanthanide complexes can be employed in solution processed CP OLEDs, obtaining highly CP emission [1]. Here, we present a strategy to improve devices efficiency both in terms of external quantum efficiency and degree of polarization of emitted photons, based on the optimization of the active layer formulation and devices architecture [2]. In this way, 75 % of emitted photons at 595 nm are circularly polarized with an EQE enhanced by one order of magnitude with respect to our earlier proof-of-concept prototype. Moreover, by comparing experimental data and modeling the main factors affecting polarization inside such devices are identified: the position of the recombination zone allied with the reflection on the cathode plays a major role on the polarization outcomes. The development of devices embedding other classes of chiral emitters can be envisaged to possibly bring the organic chiral photonic technology to the next readiness level. [1] F. Zinna, U. Giovanella, L. Di Bari, Adv. Mater. 2015, 27, 1791. [2] F. Zinna, M. Pasini, F. Galeotti, C. Botta, L. Di Bari, U. Giovanella, Adv. Funct. Mater. 2017, 27, 1603719.

L.1.5
15:30
Authors : Francesco Pastorelli
Affiliations : Organic Energy Materials, Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, 4000, Roskilde, Denmark

Resume : Printed electronics is emerging as a new, large scale and cost effective technology that will be disruptive in fields such as energy harvesting, consumer electronics and medical sensors. The performance of printed organic electronic devices relies principally on the carrier mobility and molecular packing of the polymer semiconductor material. Unfortunately, the analysis of such materials is generally performed with destructive techniques, which are hard to make compatible with in situ measurements, and pose a great obstacle for the mass production of printed electronics devices. A rapid, in situ, non-destructive and low-cost testing method is needed. In this study, we demonstrate that nonlinear optical microscopy is a promising technique to achieve this goal. Using ultrashort laser pulses we stimulate two-photon absorption in a roll coated polymer semiconductor and map the resulting two-photon induced photoluminescence (TPPL) and second harmonic response. We anticipate that this non-linear optical method will substantially contribute to the understanding of printed electronic devices and demonstrate it as a promising novel tool for non-destructive and facile testing of materials during printing of the device and at any moment during its lifespan. This will help the production and development of high quality printed technologies where the semiconductor material can be accessed by infrared light, such as solar cells, displays and sensors.

L.1.6
15:45
Authors : Ji Hwan Kim, Chang-Hyun Kim, Myung-Han Yoon*
Affiliations : School of Materials Science and Engineering, Gwangju Institute of Science and Technology

Resume : Organic Field-Effect Transistor (OFET)-based memory devices are the most promising candidate for the flash memory function of organic electronics because of its nondestructive read out, single transistor realization, and ease of the integration of circuit. But the repetitive bias stress applied to the OFET-based memory device during electrical programming/erasing process impedes the reproducible, and long-term operation of memory functionality. In this study, optically programmable memory device based on plasmonics effect is suggested. Thermally deposited noble metal nanoparticles (NPs) on the semiconducting dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT) layer of OFET provide enhanced light-absorption characteristics introduced by the localized surface plasmon resonance (LSPR) of noble metal NPs. Direct correlation between enhanced light-absorption and photogenerated current was confirmed by short-term transient photocurrent measurement. Also, the charge trapping and retention characteristics of noble metal NPs was confirmed by measuring long-term transient photocurrent measurement. The detailed mechanism of enhanced light-absorption and the charge trapping and retention properties induced by noble metal NPs was described. This novel device is expected to be a promising candidate for optically programmable organic memory devices with stable and reproducible operation.

L.1.7
16:00 Coffee break    
16:15 Plenary Session    
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Doping : Thomas Anthopoulos, Hagen Klauk, Vivek Subramanian
08:30
Authors : Daniele Fazzi
Affiliations : Max-Planck-Institut für Kohlenforschung (MPI-KOFO)

Resume : The concept of polaron in nowadays high charge mobility (i.e. > 1 cm2/Vs) p-conjugated polymers will be reinvestigated. I will survey and compare the physico-chemical properties of polarons (i.e. localization length, electronic transitions, spin density) in state-of-the-art homo-polymers and donor-acceptor polymers, relevant for photovoltaic and thermoelectric applications. In particular, I will discuss three case studies: 1) photoinduced infra-red active vibrational features (IRAV) of crystalline and amorphous polymers (e.g. P3HT and PCPDTBT) [1,2]; 2) polaron localization vs. delocalization phenomena in donor-acceptor systems (e.g. P(NDI2OD-T2)) [3]; 3) polaron transfer mechanisms [4] and their connection to macroscopic thermoelectric properties (e.g. Seebeck coefficient) in polymers. For each case study joint theoretical and experimental insights will be discussed. [1] J. Yin, Z. Wang, D. Fazzi, Z. Shen, and C. Soci, J. Phys. Chem. C, 2016, 120, 1994–2001 [2] S. Kahmann, D. Fazzi, G. Matt, W.Thiel, M.A. Loi, C. J. Brabec J. Phys. Chem. Lett. 2016, 7, 4438–4444 [3] S. Wang, H. Sun, U. Ail, M. Vagin, P. O. Å. Persson, J. W. Andreasen, W. Thiel, M. Berggren, X. Crispin, D. Fazzi, S. Fabiano Adv. Mater., 2016, DOI: 10.1002/adma.201603731 [4] D. Fazzi and M. Caironi Phys. Chem. Chem. Phys., 2015, 17, 8573-8590.

L.1.1
09:00
Authors : Beth Rice, Jarvist Frost and Jenny Nelson
Affiliations : Imperial College London

Resume : Charge mobility in organic semiconductors is modest, due mainly to the soft, amorphous nature of these solution processed materials. This limits the efficiency and technological utility of organic electronics. Disorder makes calculating the underlying electronic structure and simulating charge transport challenging. Here we study fullerene adducts, solution processable derivatives of C60. We generate assemblies (1000 molecules) of different fullerene adducts using a coarse-grained molecular dynamics. 1 We build a tight binding model of the electronic structure of these assemblies, with parameters from quantum chemical calculations, and calculate electronic densities of states for different fullerene adducts. Organic materials are soft, and deform in the presence of a free charge to form a localised charge (a polaron). We have developed a model for polaron formation by self-consistently solving the tight-binding Hamiltonian for the system with the site energies perturbed by the dielectric response of the lattice to the charge density. This allows us to study the spatial delocalisation of the polaron state and polaron transport in these large assemblies, as a function of fullerene structure and composition. In order to study the dynamic response of the coupled lattice and electronic system, we build a simplified 1D system and directly propagate the joint equations of motion. 1 F.Steiner et al, Materials Horizons, 2014, 2, 113-119.

L.1.2
09:15
Authors : Julie Herrbach, Amélie Revaux, Dominique Vuillaume; Antoine Kahn
Affiliations : Univ. Grenoble Alpes, CEA-LITEN, Grenoble, 38000, France ; Univ. Grenoble Alpes, CEA-LITEN, Grenoble, 38000, France ; IEMN, CNRS, Univ. Lille, Villeneuve d'Ascq, 59652, France ; Dept. of Electrical Engineering, Princeton University, Princeton, NJ, 08544, USA

Resume : Chemical doping of organic semiconductors is known to increase conductivity, as well as carrier mobility at low concentration due to trap filling. At higher concentration, doping is used to enhance charge injection through effective barrier lowering at electrode/organic interfaces. However, the impact of molecular dopants on the electronic structure of the host, in particular with regards to the formation of new gap states, is not well understood, and a deeper understanding of this issue is necessary to push the boundaries of this new technology. In this work, we investigate the doping process at different regimes for poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b′)dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-c) p-doped with the complex Mo(tfd-COCF3)3. Admittance spectroscopy measurements performed at temperatures ranging from 100 to 300K highlight the presence of two gap states. The first energy level is situated ca. 280 meV above the polymer HOMO and is intrinsic to the semiconductor. With doping, a second peak is observed suggesting the formation of a gap state ca. 450 meV above the polymer HOMO. This is consistent with the appearance of sub-gap absorption peaks by UV-visible spectroscopy and photoluminescence quenching. Such result highlights the interplay between doping and deep gap state creation, and represent a step towards organic technology optimization for a more efficient doping process.

L.1.3
09:30
Authors : V.V. Bruevich (1), V.G. Konstantinov (1), N.V. Gultikov (1), O.D. Parashchuk (1), O.V. Borshchev (2), N.M. Surin (2), S.A. Ponomarenko (2, 3), D.Yu. Paraschuk (1)
Affiliations : 1) Faculty of Physics & International Laser Center, Lomonosov Moscow State University 2) Institute of Synthetic Polymeric Materials of Russian Academy of Sciences 3) Chemistry Department, Lomonosov Moscow State University

Resume : Thiophene-phenelyne co-oligomers (TPCO) single crystals are promising materials for organic light emitting transistors and injection lasers as they combine high luminescence yield with efficient charge transport. However, the nature of excellent luminescent properties of TPCO single crystals have not yet been totally understood. In this work, we demonstrate that luminescent properties of TPCO can be dominated by impurities that are longer TPCO appeared during the synthesis. We have studied TPCO with the conjugated cores PTTP and PTPTP (P and T are phenylene and thiophene rings, respectively) with various end groups by using different synthetic routes. The TPCO crystals were grown from the vapor phase and solution. We have found that the photoluminescence (PL) of the TPCO single crystals can be dominated by the unintentional dopants, which act as an excitation energy funnel significantly increasing the PL efficiency. Furthermore, we show that intentional doping of TPCO crystals with longer TPCO can be used to control the energy transfer and maximize the PL quantum yield in single crystals. Doping level was controlled down to 100 ppm by using sensitive photodeflection and photoluminescence methods. Doping of TPCO by longer co-oligomers is a promising route to create highly efficient optoelectronic and light emitting materials and to tune their luminescence properties. This work was supported by Russian Science Foundation (project № 15-12-30031).

L.1.4
09:45
Authors : Masahiro Hiramoto
Affiliations : Institute for Molecular Science

Resume : Conversion efficiency of organic thin-film solar cell reached 12%. In 1991, I proposed pin junction incorporating co-deposited i-interlayer consisting of donor/acceptor organic semiconductors (so-called bulkheterojunction), which is an indispensable for present organic solar cells [1,2]. In this paper, effects of impurity doping at ppm level in photovoltaic organic semiconductors, including (i) ‘seven-nines’ purification of organic semiconductors [3], (ii) pn-control of single and co-deposited organic semiconductors by impurity doping [4-9], (iii) Ionization sensitization of doping showing the doping efficiency of 100% [10], (vi) ppm-doping effects in the simplest n+p-homojunction organic photovoltaic cells [11], and (v) ppm-doping effects in the organic single crystals, will be presented. 1. M. Hiramoto et al., Appl. Phys. Lett., 58, 1062 (1991). 2. M. Hiramoto et al., J. Appl. Phys., 72, 3781 (1992). 3. M. Hiramoto, M. Kubo, Y. Shinmura et al., Electronics, 3, 351 (2014). 4. M. Kubo et al., Appl. Phys. Lett., 98, 073311 (2011). 5. M. Kubo et al., AIP Advances, 1, 032177 (2011). 6. Y. Shinmura et al., AIP Advances, 2, 032145 (2012). 7. Y. Shinmura et al., Appl. Phys. Express, 7, 071601 (2014). 8. N. Ishiyama et al., Appl. Phys. Lett., 99, 133301 (2011). 9. N. Ishiyama et al., Org. Electron, 14, 1793 (2013). 10. Y. Shinmura et al., Appl. Phys. Lett., 105, 183306 (2014). 11. C. Ohashi et al., Org. Electron., 27, 151-154 (2015).

L.1.5
10:00 Coffee break    
10:30
Authors : Jana Zaumseil, Chloe Francis, Daniele Fazzi
Affiliations : Universität Heidelberg, Institute for Physical Chemistry, D-69120 Heidelberg, Germany; Universität Heidelberg, Institute for Physical Chemistry, D-69120 Heidelberg, Germany & University of York, York YO10 5DD, United Kingdom; Max-Planck-Institut für Kohlenforschung (MPI-KOFO), D-45470 Mühlheim an der Ruhr, Germany

Resume : Raman spectroscopy is a powerful tool to characterize electron-phonon coupling in various semiconductors. Here, we investigate the polaronic nature of two well-known high-mobility, thiophene-based polymers (PBTTT and DPPT-TT) by Raman spectroscopy combined with Density Functional Theory (DFT) calculations. Chemical and electrochemical hole doping of these polymers leads to characteristics changes in the intensity ratios of prominent Raman-active modes but no significant frequency shifts. The data suggest a localization of positive polarons on the electron-rich thienothiophene cores that are present in both polymers. DFT calculations also show that the mode intensity ratio variations are most likely caused by the local electric field that originates from negatively charged dopant molecules or electrolyte anions and the positive polaron on the polymer chain. The characteristic changes of the Raman mode intensities with the degree of doping also enable in-situ mapping of charge carrier concentration in the channel of electrolyte-gated polymer transistors with high spatial resolution.

L.1.6
11:00
Authors : Hofmann, A.I.; Katsigiannopoulos, D.; Mumtaz, M.; Pecastaings, G.; Fleury, G.; Pavlopoulou, E.; Brochon, C.; Hadziioannou, G.; Cloutet, E.
Affiliations : [1] Université de Bordeaux, Laboratoire de Chimie des Polymères Organiques (LCPO), UMR 5629, B8 Allée Geoffroy Saint Hilaire, F‐33615 Pessac Cedex, France [2] Centre National de la Recherche Scientifique (CNRS) ,Laboratoire de Chimie des Polymères Organiques (LCPO), UMR 5629, B8 Allée Geoffroy Saint Hilaire, F‐33615 Pessac Cedex, France [3] Institut National Polytechnique de Bordeaux (INP Bordeaux), Laboratoire de Chimie des Polymères Organiques (LCPO), UMR 5629, B8 Allée Geoffroy Saint Hilaire, F‐33615 Pessac Cedex, France

Resume : Organic conducting polymers are of increasing scientific interest and are promising candidates for various applications [1]. Nowadays, one the most important challenges faced by the community deals with their processability along with their long term stability. In this context, herein, I'd like to present one approach consisting in the search for an alternative to polystyrenesulfonate (PSS) in the stabilization process of poly(3,4-ethylenedioxythiophene) (PEDOT) inks. A solution is for instance based on (trifluoromethanebis(sulfonyl)imide) (TSFI) side groups attached to a polystyrene backbone. This PEDOT:polyelectrolyte system showed interesting features as compared to PEDOT:PSS, for instance its rheological behavior, its doping, opto-electronic performance and long term stability. The influence of the synthesis parameters and the composition on the named properties were studied. The new PEDOT:polyelectrolyte system was finally successfully integrated as transparent electrode in OLED and OPV devices [2] and as channel material in organic electrochemical transistors [3]. (1) Skotheim, T. A.; Reynolds, J. R. Handbook of Conducting Polymers, CRC Press, NY, 2007, 1680 pages. (2) Cloutet, E. and coll. Angew. Chem. Int. Ed. 2015, 54 (29), 8506–8510. (3) Hadziioannou, G.; Malliaras, G.G. and coll. J. Polym. Sci.: Part B, Polym. Phys. 2016, 54(2), 147-151.

L.1.7
11:15
Authors : Wouter A. Koopman, Marco Natali, Giovanni P. Donati, Michele Muccini, Stefano Toffanin
Affiliations : Wouter A. Koopman Universität Potsdam, Institute of Physics & Astronomy, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany; Marco Natali CNR-ISMN, Bologna Via P. Gobetti 101, 40129 Bologna (BO), Italy; Giovanni P. Donati CNR-ISMN, Bologna Via P. Gobetti 101, 40129 Bologna (BO), Italy; Michele Muccini CNR-ISMN, Bologna Via P. Gobetti 101, 40129 Bologna (BO), Italy; Stefano Toffanin CNR-ISMN, Bologna Via P. Gobetti 101, 40129 Bologna (BO), Italy;

Resume : Charge-exciton interaction is the main dominating mechanisms limiting the efficiency in Organic Light-emitting Transistors (OLETs). Thus, a comprehensive physical understanding of this detrimental process in charge accumulation devices is mandatory in order to unlock the technological potentiality of OLETs in real-setting applications. We have recently introduced a novel confocal microscopy method for mapping the charge density spatial distribution in OFETs based on the photoluminescence electro-modulation (PLEM) [1]. Here, we implement time-resolved PLEM spectroscopy on the picosecond timescale to investigate throughout the charge-exciton interaction in organic transistors [2]. The results show that the injected charges reduce the exciton radiative recombination in two ways: (i) charges may prevent the generation of excitons and (ii) charges activate a further non-radiative channel for the exciton decay. Moreover, the measurements clearly reveal that not only trapped charges, as it was already reported, but rather the entire injected charge density contributes to the quenching of excitons. Based on these insights we suggest possible measures to achieve high exciton density in OLETs, which might foster the development of high brightness OLETs. [1] Koopman W., Toffanin S., Natali M., Troisi S., Capelli R., Biondo V., Stefani A., Muccini M. Nano Lett. 2014, 14, 4. [2] Koopman W., Natali M., Donati G. P., Muccini M., Toffanin S. ACS Photonics DOI: 10.1021/acsphotonics.6b00573.

L.1.4
11:30
Authors : Simone Fabiano
Affiliations : Laboratory of Organic Electronics, Dept. of Science and Technology (ITN), Linköping University, Norrköping, SE-601 74, Sweden

Resume : Conducting polymers are an emerging class of materials for large-area solid-state energy conversion and storage applications. These materials enable new paths toward more sustainable energy-related technologies without the need of expensive, or even toxic metal-based compounds. Unlike their p-type counterparts, n-doped conducting polymers typically suffer from a low electrical conductivity (< 0.01 S/cm). Despite continuous efforts to understand charge transport mechanism in these materials and how it affects the device performance, the interplay between chemical structure, polaron delocalization lenght, and conductivity remains unclear. Here we show that n-doped polymers do not necessarily have to follow the typical design rules of semiconducting polymers for field-effect transistors. In contrast to undoped polymers where in fact regioregularity of the backbone and crystallinity are pursued for their beneficial effect on charge carrier mobility, polymers used in their doped state should be designed to have long polaron delocalization lengths in order to reach high conductivity. In particular, we will show that linear torsion-free polymer backbones enable a delocalized anion to form upon doping, leading to high conductivity as compared to distorted n-doped donor-acceptor polymers. Understanding these principles will guide the design of next-generation high-conductivity polymers that can find applications in batteries, supercapacitors, and thermoelectrics.

L.1.9
12:00 Lunch    
 
Structure Property Relationships III : Simone Fabiano, Jana Zaumseil, Daniele Fazzi
14:00
Authors : Thomas D. Anthopoulos
Affiliations : 1. Department of Physics and The Centre for Plastic Electronics Imperial College London, London SW7 2AZ (U.K.) 2. Materials Science and Engineering, Division of Physical Sciences and Engineering King Abdullah University of Science and Technology Thuwal 23955-6900 (Saudi Arabia)

Resume : The continuous demand for organic thin-film transistors (OTFTs) with improved performance has been the driving force behind the tremendous progressed witnessed during the past decade in the field of printed electronics. The most common approach towards this goal has been the development of new semiconductors with enhanced charge transport characteristics accompanied by in-depth understanding of the material’s structure-property relationship. In this presentation I will discuss an alternative strategy to materials, and ultimately OTFT and integrated circuits, development based on the use of molecular dopants/additives in combination with binary semiconducting small-molecule/polymer blends. I will describe how the incorporation of different types of dopants can lead to semiconducting systems and devices that combine highly attractive features such as solution processability and high carrier mobility with significantly improved OTFT bias stability. The role of the dopant and the underlying mechanism responsible for the performance enhancement observed in several different material systems will also be discussed.

L.1.1
14:30
Authors : Mark Nikolka1; Iyad Nasrallah1; Katharina Broch1; Iain McCulloch2; Henning Sirringhaus1
Affiliations : 1 Optoelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom; 2 Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom

Resume : Due to their ease of processing, organic semiconductors are promising candidates for applications in high performance flexible displays and fast organic electronic circuitry. Recently, a lot of advances have been made on organic semiconductors exhibiting surprisingly high performance and carrier mobilities exceeding those of amorphous silicon1. However, there remain significant concerns about their operational and environmental stability. Here, we report a novel technique for dramatically improving the operational stability, performance and uniformity of high mobility polymer devices such as field-effect transistors and diodes by the addition of specific small molecule additives to the polymer semiconductor film. We demonstrate for the first time polymer FETs that exhibit stable threshold voltages with threshold voltage shifts of less than 1V when subjected to a constant current operational stress for 1 day under conditions that are representative for applications in OLED active matrix displays. The approach constitutes in our view a technological breakthrough; it also makes the device characteristics independent of the atmosphere in which it is operated, causes a significant reduction in contact resistance and bulk trap density and significantly improves device uniformity2. We will discuss in detail the microscopic mechanism by which the molecular additives lead to this significant improvement in device performance and stability. [1] D. Venkateshvaran*, M. Nikolka* et al., Nature, 515, 384−388 (2014) [2] M. Nikolka*, I. Nasrallah* et al., Nature Materials, In Press

L.1.2
14:45
Authors : Luiz G. S. Albano, Miguel H. Boratto, Carlos F. O. Graeff
Affiliations : São Paulo State University (Unesp), School of Sciences, Bauru, SP, 17033-360, Brazil

Resume : Electrodes based on silver nanowires have been demonstrated using techniques such as dip-coating, spin-coating, and roll to roll combined with different processing steps. This applicability is interesting for solar cells, light emitting diodes, and vertical organic field effect transistors (VOFETs). A VOFET is essentially a semiconductor diode stacked on capacitor separated by a common source electrode, so when the capacitor is charge up with gate voltage the channel region is affected due to the electrical transparency required from source electrode. Intermediate metal electrodes deposited by thermal evaporation are most heavily used, although its limited transparency resulting in devices operating at high voltages. In this work, we report a VOFET with silver nanowires deposited by Meyer rod coating as source electrode using cross-linked polyvinyl alcohol as gate insulator and C60 fullerene as n-type semiconductor. Silver nanowires electrodes were characterized previously on dielectric surface showing sheet resistance of 22.7 ± 1.55 Ω/sq and 85.2 ± 20.5 nm of roughness surface. Devices presented high current density (mA/cm²) and ON/OFF ratio of ~700 with supply voltages of 2V. A frequency operation of 13 MHz was recorded operating at 1.5V drain and gate voltages, in agreement with theoretical cutoff calculated. Such results are mainly due to the low capacitance by area of dielectric (~20nF/cm²) and the high transparency to the DC electric fields of source electrode.

L.1.3
15:00
Authors : Peter HO, Cindy TANG
Affiliations : National University of Singapore

Resume : To make high-performance semiconductor devices, a good ohmic contact between the electrode and the semiconductor layer is required to inject the maximum current density across the contact. Achieving ohmic contacts requires electrodes with high and low work functions to inject holes and electrons respectively. However, it is challenging to produce electrically conducting films with sufficiently high or low work functions, especially for solution-processed semiconductor devices. Hole-doped polymer organic semiconductors are available in a limited work-function range, but hole-doped materials with ultrahigh work functions and, especially, electron-doped materials with low to ultralow work functions are not yet available. The key challenges are stabilizing the thin films against de-doping and suppressing dopant migration. Here we report a general strategy to overcome these limitations and achieve solution-processed doped films over a wide range of work functions (3.0–5.8 eV), by charge-doping of conjugated polyelectrolytes and then internal ion-exchange to give self-compensated heavily doped polymers. Mobile carriers on the polymer backbone in these materials are compensated by covalently bonded counter-ions. Although our self-compensated doped polymers superficially resemble self-doped polymers, they are generated by separate charge-carrier doping and compensation steps, which enables the use of strong dopants to access extreme work functions. We demonstrate solution-processed ohmic contacts for high-performance organic light-emitting diodes, solar cells, photodiodes and transistors, including ohmic injection of both carrier types into polyfluorene—the benchmark wide-bandgap blue-light-emitting polymer organic semiconductor. We also show that metal electrodes can be transformed into highly efficient hole- and electron-injection contacts via the self-assembly of these doped polyelectrolytes. This consequently allows ambipolar field effect transistors to be transformed into high-performance p- and n-channel transistors. Our strategy provides a method for producing ohmic contacts not only for organic semiconductors, but potentially for other advanced semiconductors as well, including perovskites, quantum dots, nanotubes and two-dimensional materials.

L.1.8
15:15
Authors : René Janssen
Affiliations : Eindhoven University of Technology

Resume : The efficiency of bulk-heterojunction polymer:fullerene solar cells critically depends on the dominant length scale of the morphology formed during drying of the photoactive film. Time-resolved studies that allow studying the kinetics of film and morphology formation have been performed on a blend of a diketopyrrolopyrrole-based polymer with a fullerene derivative, deposited from solvents with and without co-solvent. Using in-situ time-resolved optical and diffraction techniques, combined with ex-situ transmission electron microscopy, we are able to determine the parameters that influence the dominant length scales in the phase separated films. Without co-solvents, large fullerene domains are formed by liquid-liquid phase separation, whose size is governed by the drying rate when normalized to the final thickness. With co-solvents, on other hand, the dominant length scale is not determined by liquid-liquid demixing, but by polymer aggregation. The width of the polymer fibers that are formed by the aggregation can be controlled by adjusting the nature of the co-solvent mixture and by several other factors such as molecular weight of the polymer, introducing branching in the polymer, and the temperature at which the layers are processed from solution. With these studies we have established some guide lines that assist to find the optimal morphology via rational steps.

L.1.5
15:45 Coffee break    

No abstract for this day


Symposium organizers
Christian MÜLLERChalmers University of Technology

Department of Chemical and Biological Engineering, Göteborg, Sweden

christian.muller@chalmers.se
Elizabeth VON HAUFFVU Amsterdam

Department of Physics & Astronomy, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands

e.l.von.hauff@vu.nl
Mario CAIRONICenter for Nano Science and Technology

Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy

mario.caironi@iit.it
Michael SOMMERUniversity of Freiburg

Department for Macromolecular Chemistry, Stefan-Meier-Str. 31, 79104 Freiburg, Germany

michael.sommer@chemie.tu-chemnitz.de