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Materials and devices for energy and environment applications


Solution-based emerging hybrid solar cells

Introduction and scope:

Recent progress in solution-based, emerging technology photovoltaic research has generated significant milestones for efficient solar energy conversion. In particular, hybrid perovskite materials demonstrate hallmark performances breaking 20% power conversion efficiency. In light of its successful development this symposium concentrates know-how and insights from various potential solution-based emerging material classes in order to pursue high-efficiency scenarios for each. Scientists working at various central fronts in perovskite, quantum-dot, polymer-organic and dye-sensitized solar cells are invited to contribute to a multidisciplinary platform to present their insights. The symposium will entangle know-how and foster discussion across borders in order to analyse present loss mechanisms and overcome device limits using alternative, elaborate strategies. The symposium aims at a technology transfer within emerging material classes to design a high-performance scenario for all.

Solution-based emerging photovoltaic absorber materials have been matter of research for decades and various thin-film technologies have passed the pioneer-phase and entered now an elaborate degree of maturity in terms of physical understanding, thin-film processing and efficiency optimization. Still, the full potential of these materials is not harnessed and a directed, to-the-point material research is needed to push present device strategies a step forward for implementing them into discrete large-area solar applications. To satisfy the requirements for a sustainable terawatt-scenario, materials used have to be abundant and stable, active thin-films have to be printed from solution and their environmental impact has to be manageable. However, the key-requirement finally represents a strong performance of the solution-cast absorber itself to allow efficient power-conversion. Among others, perovskites appear therefore outstanding, as performances developed within a few years towards 20%. The fact, that they convert light to electricity so efficiently, has appealed scientist to shift their focus to this material class. Consequently a technology transfer of insights across solution-based emerging organic, hybrid, quantum-dot and dye-sensitized solar cell absorbers to perovskites has been observed. This symposium pursues now a parallel back-transfer of insights from perovskites to original emerging materials, in order to create a high-efficiency scenario for all of them. On basis of insights from perovskites, the scientific scope will handle a sensible analysis of loss mechanisms and possible ways to work around them to focus the material research for high-performance scenarios. The scope of the symposium will include all important aspects of photovoltaic energy conversion starting from optical considerations, electrical transport and charge extraction as well as recombination and trap-evaluation and interface management in the corresponding solution-processed thin-film absorbers. The discussion will help all contributors to exchange important key-insights to break present limitations for future light-harvesting strategies. The symposium therefore aims at creating networks as platform for technology-exchange to overcome existing losses and to implement high-performance, efficient solar cell scenarios as realistic as possible.

Hot topics to be covered by the symposium:

  • Emerging photovoltaic material insights
  • Solution-processing of thin-films
  • Light management and optical improvements
  • Inherent photovoltaic losses

List of invited speakers:

Scientific committee:

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Organic Solar Cells : Philipp Stadler
Authors : Yasushi Nishihara
Affiliations : Research Institute for Interdisciplinary Science, Okayama University

Resume : Transition metal-catalyzed cross-coupling and cyclization reactions have been utilized to synthesize picene, a compound consisting of five fused benzene ring with an armchair structure and its derivatives. We further designed to replace two terminal benzene rings with thiophene rings to yield phenanthro[1,2-b:8,7-b']dithiophene (PDT). Moreover, we synthesized the low-band gap semiconducting polymers containing a PDT core in the polymer backbone These PDT-based polymers have some superior features, including strong intermolecular interaction, high thermal stability, deep HOMO energy levels, and dense packing structure in their solid state. The solar cell devices using PDT-isoindigo (IID) copolymer or PDT-benzothiadiazole (BT) exhibited high power conversion efficiency (PCE) with 5.28% and 6.56%, respectively. In particular, PDT-BT copolymers formed a desirable face-on orientation, which can promote the efficient carrier transport in solar cells, reading to high PCE. We measured DSC (differential scanning calorimetry) and TG-DTA (thermogravimetry -differential thermal analysis) in order to investigate the thermal stability of the solid states of several PDT polymers, which were copolymerized with IID (isoindigo), DPP (diketopyrrolopyrrole) and BZT (benzothiadiazole) units. From DSC measurements, P3HT, which has been widely studied for various electronics devices, showed phase transition peak around 200 oC in heating and cooling processes. On the other hand, these polymers showed no peak ascribed to a phase transition in the range of 50-250 ºC. The thermal decomposition temperatures estimated by TG/DTA was higher than 300 ºC, which is inferior to that of P3HT. These results show that the devices composed of these polymers maintain the solid state, and thus the device performances. Furthermore, these polymers are stable than P3HT. The HOMO level measured by PYS (photoelectron yield spectroscopy) shifted to a more negative side upon storage in air, but the degree of a change was smaller than that of P3HT. This indicates that the device composed of these polymers may keep the good performance longer than that composed of P3HT.

Authors : Alexander V. Akkuratov, Iliya E. Kuznetsov, Irina V. Klimovich, Diana K. Susarova, Fedor A. Prudnov, and Pavel A. Troshin
Affiliations : Institute for Problems of Chemical Physics of RAS, Semenov ave. 1, Chernogolovka, Moscow region, 142432, Russia; Skolkovo Institute of Science and Technology, Nobel st. 3, Moscow, Russian

Resume : Organic solar cells based on conjugated polymers demonstrated efficiencies approaching 8 10%. Unfortunately, the best-performing materials undergo rapid photochemical degradation. On the contrary, long operation lifetimes (7-15 years) have been projected for some less efficient polymers possessing robust chemical structures, e.g. PCDTBT. In the present talk we will present our strategy of designing PCDTBT-like polymers with narrowed band gaps using alternating DADAD architectures as building blocks (D – electron donor such as thiophene, while A is an acceptor like benzothiadiazole or benzoxadiazole) [1-3]. Synthesized polymers demonstrated diverse optoelectronic and photovoltaic characteristics. The best materials showed solar cell efficiencies approaching 7% in combination with long-term operation stability. Higher performances of 10-11% are feasible for single junction devices due optimal band gaps (1.60-1.65 eV) and deep-lying HOMO energy levels (~ -5.5 eV) of the designed materials. The developed polymers enabled fabrication of larger area solar cells under ambient conditions in air using slot die coating which is a roll-to-roll compatible film deposition technology [4]. The power conversion efficiency of the coated devices exceeded 6%. [1] A. V. Akkuratov, et al., Macromolecules 2015, 48, 2013 [2] I. E. Kuznetsov, et al., Chem. Comm., 2015, 51, 7562 [3] A V. Akkuratov, et al., J. Mater. Chem. C, 2015, 3, 1497 [4] I. Burgués-Ceballos et al., ChemSusChem, 2015, 8, 4209

Authors : Rupali R. Jadhav, 1,2, Nadia Camaioni,3 Prakash P. Wadgaonkar,2 and Daniel A. M. Egbe1
Affiliations : 1Linz Institute for Organic Solar Cells and Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria 2Polymer & Advanced Materials Laboratory, Polymer Science and Engineering Division, CSIR - National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, Maharashtra, India 3Instituto per la Sintesi Oragnica e la Fotoreattivita, Consiglio Nazionale delle Ricerche, via P. Gobetti 101, I-40129 Bologna, Italy

Resume : Four 2-dimensional conjugated poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene) polymers containing lateral bi(thienylenevinylene)thiophene unit (BTE-PVs) sharing the same conjugated structure, but differing in the anchoring positions of solubilising linear octyloxy/branched 2-ethylheylox side-chains were synthesized. UV-vis spectra of polymers in dilute chloroform solutions and on thin films were studied. X-ray diffraction patterns as well as the bulk charge transport of polymer films cast from chlorobenzene solutions were also investigated. A dramatic effect of the solubilising side-chains on charge carrier mobility of BTE-PV films was observed, with bulk hole mobility values ranging between 1.3x10-5 cm2 V-1s-1 and 2.2x10-2 cm2 V-1 s-1, which is not ascribable to evident structural variations of the polymer films. It is shown that the combinations of linear octyloxy and branched 2-ethylhexyloxy side-chains is favorrable fo rthe charge transport properties of BTE-PVs, compared to the incorporation of only linear or only branched side-chains.1

Authors : Hideo Ohkita
Affiliations : Kyoto University

Resume : Solution-processed photovoltaics have made rapid progress in the last decade and are currently attracting a great deal of attention as next generation solar cells. Recently, most of organic photovoltaics have shown a power conversion efficiency (PCE) of more than 10%. However, further improvements are still required for practical applications. In this talk, I will discuss the efficiency limiting factors of solution-processed photovoltaics such as polymer/fullerene solar cells and perovskite solar cells. For polymer solar cells, there is still room to improve not only short-circuit current density (Jsc) but also open-circuit voltage (Voc). In order to improve the photocurrent generation furthermore, we have recently developed ternary blend polymer solar cells based on a wide-bandgap polymer, poly(3-hexylthiophene) (P3HT), a fullerene derivative (PCBM), and a near-IR dye molecule such as silicon phthalocyanine bis(trihexylsilyl oxide) (SiPc). This approach can break through the light-harvesting limit of polymer/fullerene binary blend solar cells. We will demonstrate how such molecular design can improve the photovoltaic performance of ternary blend solar cells effectively. We next focus on the charge generation efficiency in polymer solar cells studied by transient absorption spectroscopy. By analyzing the charge generation dynamics, we found that highly crystalline polymer solar cells are likely to exhibit the higher charge dissociation efficiency. More interestingly, high charge dissociation was observed for one of the most highly crystalline polymers (PNOz4T) even though the LUMO–LUMO offset energy is negligibly small. This finding suggests that the photon energy loss in polymer solar cells would be minimized to improve the Voc furthermore. For perovskite solar cells, we have studied how grain sizes of perovskite impact on the photovoltaic performance. As a result, we found that all the photovoltaic parameters increase with increasing grain size: Jsc is almost saturated up to ~23 mA cm−2, Voc increases up to 1.08 V, FF increases to 0.75, and hence PCE is improved to more than 19% with a grain size of ~500 nm. We will discuss the relationship between the photovoltaic performance and grain purity of perovskite materials.

Tandem and High-Voltage PV : Yasushi Nishihara
Authors : Ning Li, Christoph J. Brabec
Affiliations : N. Li; C. J. Brabec; Institute of Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander University Erlangen-Nürnberg, Martensstrasse 7, 91058 Erlangen, Germany. C. J. Brabec; Bavarian Center for Applied Energy Research (ZAE Bayern), Haberstrasse 2a, 91058 Erlangen, Germany.

Resume : The multi-junction concept is especially attractive for the photovoltaic (PV) research community owing to its potential to overcome the Schockley-Queisser limit of single-junction solar cells. By stacking and connecting single cells with complementary absorption spectra, the multi-junction concept has been successfully validated in the conventional PV technologies. Tremendous research interests are now focused on the development of high-performance absorbers and novel device architectures for emerging PV technologies, such as organic and perovskite PVs. The construction of multi-junction architectures is directly determined by the functionality and reliability of interfacial layers. The energy barriers between electrodes and absorbing layers have to be minimized by employing effective interfacial layers. The free charge carriers selectively extracted by the interfacial layers have to be conducted to the corresponding electrodes or to the intermediate layer with minimized losses. However, the commonly used p-type interfacial layer, PEDOT:PSS, does not perform well when coated on top of most high-performance organic donors, thus restricting their application in printed multi-junction technologies. In this contribution, we will demonstrate design rules for solution-processed, effective interfacial layers, which can be used for realizing highly functional organic and hybrid multi-junction solar cells. The interfacial layers designed by engineering are fully compatible with state-of-the-art organic donors, exhibiting great potential for realizing high-performance, fully-printed multi-junction solar cells. Moreover, a simple but elegant approach to fabricating organic and hybrid multi-junction solar cells will be introduced. By laminating single organic/hybrid solar cells together through an intermediate layer, the manufacturing cost and complexity of large-scale multi-junction solar cells can be significantly reduced.

Authors : Hiroshi Segawa
Affiliations : Department of General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba 4-6-1, Meguro-ku, Tokyo 153-8904, Japan

Resume : Next-generation solar cells based on new concepts and/or novel materials are currently attracting wide interests. In this study, several types of hybrid photovoltaics are investigated. Among the emerging solar cells, dye-sensitized solar cells (DSSCs) have received much attention as the low-cost solar cells [1]. In order to improve the energy conversion efficiency, the extension of absorption range of the sensitizers to near-infrared regions is an important issue [2]. In our study, panchromatic photoelectric conversion up to around 1000 nm has been accomplished by the use of new sensitizers DX1, 2, and 3. The panchromatic DSSC with DXs are useful for a series-connected tandem solar cell. We prepared the various tandem DSSCs showing a high overall power conversion efficiency (η). A spectral splitting organic photovoltaics of the DX3-sensitized solar cell and the nano-structured perovskite solar cell shows the power conversion efficiency of about 21.5% [3]. Since the mechanisms of DSSC include electrochemical reaction, it can be hybridized with an electrochemical storage battery. We have reported a three-electrode solar rechargeable battery, namely “energy-storable dye-sensitized solar cell (ES-DSSC)”, composed of the photoanode, the counter electrode and the charge-storage electrode. The ES-DSSC not only generates output power, but also stores the electricity by itself. Therefore the output voltage and power of the ES-DSSC can be stabilized under various photoirradiation conditions. Additionally, we constructed design panels of the ES-DSSC, namely "annabelle" [4]. References [1] O’Regan B., Graetzel M., Nature, 1991, 353, 737. [2] Kinoshita T., Dy J. T., Uchida S., Kubo T., Segawa H., Nature Photonics 2013, 7, 535. [3] Kinoshita T., Nonomura K., Jeon N. J., Giordano F., Abate A., Uchida S., Kubo T., Seok S. I., Nazeeruddin M. K., Hagfeldt A., Graetzel M., Segawa H., Nature Communications 2015, 6, 8834. [4] Ogura R., Sasaki M., Segawa H., Convertech & e-Print, 2014, 4, 72.

Authors : Shafi Ullah, Miguel Mollar, Hanif Ullah, Bernabé Marí
Affiliations : Institut de Disseny i Fabricació, Universitat Politècnica de València, Camí de Vera s/n, 46022 València, SPAIN

Resume : CuGaS2 polycrystalline thin films absorbers were prepared by subsequent sulfurization of electrodeposited CuGaSe2 films. CuGaSe2 films were obtained in one-step electrodeposition procedure from an aqueous electrolyte containing CuCl2, GaCl3, and H2SeO3. Subsequent sulfurization of electrodeposited CuGaSe2 precursor films was performed at 400 °C for 10 min in presence of molecular sulphur and under forming gas atmosphere. The effect of sulfurization is the complete conversion of CuGaSe2 into CuGaS2. The formation of CuGaS2 thin films is evidenced by the shift observed in X-Ray diffraction pattern and by the blue shift of the optical band gap, which rises from 1.66 eV for CuGaSe2 to 2.2 eV for CuGaS2. When part of Ga is substituted with Cr a broad intermediate absorption band associated to Cr and centred at 1.63 eV was observed in CuGaS2 films. Then, numerical simulations using Solar Cell Capacitance Simulator Software were used to estimate the behaviour of a solar cell based in CuGaS2:Cr absorbers containing an in-gap band. The quantum efficiency of simulated Mo/CuGaS2:Cr/CdS/ZnO solar cells was obtained for different amount of Cr. As expected, the in-gap absorption related to Cr, rises up the quantum efficiency. Further, the short circuit current increases proportionally to the Cr content and the photoconversion efficiency of the simulated devices changes from 14.7% for CuGaS2 to 31.6% for CuGaS2:Cr absorbers.

Authors : He Sun1, Tsubasa Kimura1, Tatsuhiro Chiba1, Matthew White2, Shingo Mori3 and Tsukasa Yoshida1
Affiliations : 1; Yamagata University 2; The University of Vermont 3; Shinshu University

Resume : Dye-sensitized solar cells (DSSCs) are solution processible, cost-effective alternative, but suffer from large voltage loss to limit their efficiency. One of the strategies to increase the voltage is to employ redox electrolytes with potentials lying more positive than the typically used I-/I3-, such as [Co(bpy)3]2 /3 . However, the expected increase of the voltage can only be achieved when the adsorbed dye layer strongly rectifies the charge transfer, namely, prevents back transfer while the forward electrolyte to dye electron transfer is favored. We have discovered that the triphenyl amine dye, D35, specifically achieves significantly high voltages over 1 V, when it is adsorbed onto porous ZnO electrodes in contact with [Co(bpy)3]2 /3 . Despite of the reasonably high IPCE of about 70% around the absorption of maximum of D35, however, its JSC was much smaller than the expected value to achieve only 0.9% conversion efficiency, due to slow hole transport by the Co redox electrolyte, as found by measurements of current linearity in a 0.01 to 2 sun range employing a variable solar simulator. By optimization of the ZnO layer thickness as well as the composition of the electrolyte solution, we have overcome the problem to achieve a linear current increase up to 2 sun and an improved efficiency of 3.1% under AM 1.5.

Charge Transfer Solar Cells : Ning Li
Authors : K. Nakayama1,2; T. Okura1; C. Katagiri1; M. Mamada1; J. Matsui1; A. Masuhara1; M. C. Scharber3; M. S. White4; C. Yumusak3; P. Stadler3; N. S. Sariciftci3; T. Yoshida1
Affiliations : 1 Yamagata University; 2 Osaka University; 3 Johannes Kepler University Linz; 4 The University of Vermont

Resume : Power Conversion efficiency of organic photovoltaic devices has exceeded 11% by taking advantage of bulk heterojunction (BHJ) structure. A remained problem is photovoltage loss from absorbed photon energy. In the BHJ system, LUMO offset is required to promote photodissociation at donor-acceptor interface, causing serious photovoltage loss. To solve this problem, we are approaching it from single absorber cells, where there is no donor-acceptor interface. Generally, photogeneration efficiency in organic film bulk is quite low because of large exciton binding energy. Here we focus on intramolecular charge transfer (CT) molecules having donor and acceptor units, because charge transferred excited state is expected to promote photodissociation in film bulk. We fabricated single absorber devices composed of ITO/PEDOT:PSS/absorber/Ca/Al using several kinds of intramolecular CT molecules. Among them, 2-{[7-(4-N,N-ditolylaminophenylen-1-yl)-2,1,3-benzothiadiazol-4-yl]methylene}malononitrile (DTDCPB) showed good J-V curves with Jsc exceeding 1 mA/cm2 and Voc around 1 V under AM1.5G illumination. In the single absorber device, exciton binding energy is a key factor to be overcome. The exciton binding energy was calculated by Gaussian09 by using solvation model. Those intramolecular CT molecules tend to have smaller exciton binding energy compared to other normal organic semiconductors.

Authors : J Matsui, K. Nakayama, A. Masuhara, M. Mamada, M. C. Scharber, P. Stadler, C. Yumusak, M. S. White, N. S. Sariciftci, T. Yoshida
Affiliations : Yamagata University; Osaka University; Kyushu University, Johannes Kepler University Linz; The University of Vermont

Resume : Charge transfer crystals (CTC), which composed by donor-acceptor type molecules (intramolecular charge transfer) or donor and acceptor molecules (intermolecular charge transfer) have been well studied for their application in non-linear optics, molecular conductors etc. We expect that CTCs will be a unique absorber for organic solar cell because excitation of charge-transfer absorption bands directly creates charge transfer state with small energy loss. Therefore organic solar cell using CTCs as an absorber has a possibility to produce organic solar cells with high open circuit voltage (VOC). For this context, we fabricate several CTCs and studied their photoconductivity. One example is a cyanine dye, HB194. We found that HB194 formed a single crystal fiber array onto a glass substrate by slowly evaporating the saturated acetone solution. The fibers are aligned vertical to the liquid surface. X-ray diffraction spectrum indicates that the fibers are formed by HB194 single crystals. UV-vis absorption peak of the fiber is shifted ~ 70 nm to the longer wavelength compared to that in solution, which support a strong π-π interaction between the molecules. HB194 fiber shows negligible current under dark condition. On the other hand, a clear photoconductivity was observed by irradiation of 633 nm, which indicate HB194 is a photoactive molecule. Moreover, the photoconductivity was increased more than four times by capping the fiber with poly(vinyl alcohol), which indicate using a high dielectric constant matrix is a method to increase photocurrent. Finally our approach for preparing CTC film will be presented.

Authors : Tsukasa Yoshida1, Taichi Yasuhara1, Jun Matsui1, Akito Masuhara1, Ken-ichi Nakayama2, Matthew Schuette White3, Philipp Stadler4, Markus Clark Scharber4, Niyazi Serdar Sariciftci4
Affiliations : 1; Yamagata University 2; Osaka University 3; The University of Vermont 4; Johannes Kepler University, Linz

Resume : Carrier generation in organic solar cells relies on the energy offset of donor / acceptor and thus inherently lose voltage to limit their efficiencies. We envision substantial increase of voltage (= minimization of voltage loss) by employing organic charge transfer crystals (CTC) in which direct formation of CT excited state upon light absorption can be expected. In this study, we have synthesized and characterized a novel CTC by combination of 1,3-bis(dicyanomethylidene)indan (TCNIH2) and methylviologen (MV2+). TCNIH2 undergoes deprotonation in polar solvents to form deeply blue-colored TCNIH- anion. Slow evaporation of solvent from ethanolic mixed solution of TCNIH- and MV2+ resulted in a formation of shiny black crystalline powder. XRD analysis of the product revealed a formation of (MV2+)(TCNIH-)2 salt. The mixed crystal exhibited a strong light absorption into the NIR range, centered at around 760 nm and extended upto about 1,000 nm, that was not seen for the TCNIH- salt stabilized by alkylammonium cation. Evaluation of the HOMO-LUMO levels of TCNIH- and MV2+ by cyclic voltammetry suggested a CT energy gap of 1.64 eV between HOMO of TCNIH- and LUMO of MV2+, exactly matched to the observed NIR absorption. A weak photoluminescence centered at 1,040 nm was observed upon excitation of the CT band for which TCNIH- and MV2+ being donor and acceptor, respectively. Although weak, this CTC layer deposited onto an interdigitated electrode exhibited a photoconductivity.

Authors : Sebastian Dunst, Mihai Irimia-Vladu*, Gregor Trimmel
Affiliations : Dr. Sebastian Dunst, Assoc. Prof. Dr. Gregor Trimmel-Technische Universität Graz, Institut für Chemische Technologie von Materialien Dr. Mihai Irimia-Vladu (presenting author)-Joanneum Research mbH, Department of Materials, Institute for Surface Technologies and Photonics

Resume : In this work we investigated an entirely new class of organic semiconductors with respect to their applicability in air stable organic photovoltaic cells. These materials are based on derivatives of natural pigments like Anthraquinone or Acridone. Their predicted properties in photovoltaic applications are very high charge carrier mobilities and high dielectric constants and thus very low exciton binding energy. Within this work many H-bonded semiconductors have been evaluated and selected, functionalized for better processability, and in a last step used for the fabrication of organic homojunction photovoltaic cells. With these materials organic homojunction photovoltaic cells with power conversion efficiencies in the range of 0.2 % have been demonstrated by our research group for both vacuum and solution processed layers.

Poster session : Matthew White
Authors : Kazuhiro Nakabayashi, Masaya Yamada, Haruka Fukuzawa, Hideharu Mori
Affiliations : Graduate School of Organic Materials Science, Yamagata University

Resume : A cross-coupling reaction between dihaloarylene monomers and unsubstituted arylene monomers in the presence of a palladium catalyst, the so-called palladium-catalyzed direct arylation, has been paid numerous attention for an environmentally-friendly, efficient, and low-cost method for the synthesis of conjugated polymers compared to conventional cross-coupling reaction, such as the Stille coupling reaction and Suzuki coupling reaction. In recent years, the synthesis of conjugated donor polymers by direct arylation has been widely reported; in contrast to synthesis of conjugated donor polymers, the synthesis of conjugated acceptor polymers by direct arylation is less developed and still a challenging issue. Herein, we developed the efficient direct arylation methodology for the synthesis of arylene bisimide-based acceptor polymers, which were known well as one of high performance acceptor polymers for organic field-effect transistors and photovoltaics applications. Three novel arylene bisimide-based monomers, which were designed for the direct arylation, were synthesized by the two-step reaction from conventional dibromoarylene bisimide-based monomers. Then a series of arylene bisimide-based acceptor polymers with the high molecular weights (Mn = 10000—30000) were successfully synthesized using these monomers under the optimized direct arylation conditions. The obtained results demonstrated that the direct arylation had a huge potential for the synthesis of acceptor polymers.

Authors : Matthias J. Kogler, Thomas Rath, Sebastian F. Hoefler, Gregor Trimmel
Affiliations : Institute for Chemistry and Technology of Materials (ICTM), NAWI Graz, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria

Resume : Polymer/copper indium sulfide (CIS) nanoparticle hybrid solar cells represent an interesting solar cell system combining advantages of inorganic semiconducting materials with these of solution processable, lightweight and flexible polymers. In this study, we prepare the CIS nanoparticles directly in the polymer matrix. This in situ formation of the CIS nanoparticles from copper and indium xanthates as precursors makes them, besides other benefits, suitable for cheap production routes at temperatures compatible with flexible substrates.[1] So far, the highest power conversion efficiencies (PCEs) of solar cells prepared via this route have been obtained with the conjugated polymers PSiF-DBT and PCDTBT. An important factor currently limiting the overall PCE of these solar cells is the strong thickness dependence of the PCE. Best PCEs were achieved with thicknesses of 70-90 nm and in layers with this thickness only a part of the incoming light can be absorbed and used for conversion. In this study, we investigated the influences of the polymer phase, polymer/nanoparticle ratio, morphology and the hybrid interface on the characteristic solar cell parameters and the thickness dependency of the PCE. We compared the currently commonly used PCDTBT to state of the art conjugated polymers used in polymer/fullerene solar cells (e.g. PBTTT, DT-PDPP2T-TT or PffBT4T) which show higher charge carrier mobility or lower dependency of PCE on absorber film thickness. As the polymer/CIS nanoparticle ratio is also strongly influencing morphology, and is thereby critical for the efficiency, these ratios also have been investigated for all used polymers. Additionally, the influence of different molecular weights of the polymers was tested. In particular, for testing PffBT4T with a high molecular weight, which led to polymer/fullerene solar cells with very high PCEs (up to 10.8%),[2] the coating and processing conditions of the absorber layer fabrication had to be adjusted as this polymer requires elevated temperatures to form stable solutions and to be processed. Regarding the hybrid interfaces and the inorganic phase, we incorporated organic additives into the fabrication process aiming to modify the polymer/nanocrystal interface and we also added hexylamine, which is known for improving the crystallinity of the nanoparticle phase.[3] Morphological aspects in the absorber layers were analyzed by AFM or TEM and the optical properties of the films were studied by UV-VIS absorption spectroscopy. The electrical properties of the prepared solar cells were characterized by current-voltage (IV) curves and external quantum efficiency (EQE) measurements. [1] C. Fradler et al., Sol. Energy Mater. Sol. Cells, 2014, 124, 117. [2] Y. Liu et al., Nature Commun., 2014, 5, 5293. [3] N. Bansal et al., Sci. Rep., 2013, 3, 1531.

Authors : Masaki Takeda1, Yoshiki Aita2, Jun Matsui3, N. S. Sariciftci4, Philipp Stadler4, Markus Scharber4, Matthew White5, Tsukasa Yoshida6, and Akito Masuhara6
Affiliations : 1. Graduate School of Science and Engineering, Yamagata University 2. Department of Chemistry and Chemical Engineering, Yamagata University 3. Faculty of engineering, Yamagata University 4. LIOS, Johannes Kepler University Linz 5. The University of Vermont 6. Research Center for Organic Electronics, Yamagata University

Resume : Non-radiative recombination of excitons, which consist of electrons and donors bound by Coulomb attraction, is one of the problems for significant increase of efficiency on organic photovoltaics (OPVs). Recently, to solve this problems, there are several reports on incorporating a ferroelectric polymer, β-phase poly(vinylidenefluoride-trifuloroethylene) (β-phase P(VDF-TrFE)) using Langmuir-Blodgett films and spin-coating films in active layers-electrodes interface, respectively. Ferroelectric polymers show electric field, therefore we can have enhancement of charge separation efficiency and charge extraction efficiency. Here, we presented a very simple approach to improve the power convention efficiency of OPVs. We used ferroelectric polymer nanocrystals (NCs) dispersion as a good solvent for photoactive materials, instead of pure solvents usually selected in typical OPVs. Only using NCs dispersion, we can be achieved OPV active layers dispersed ferroelectric polymer NCs. Ferroelectric polymer NCs dispersion was prepared by reprecipitation method. P(VDF-TrFE) solution in acetone was injected into vigorously stirred chlorobenzene. The initial amorphous nanoparticles (NPs) dispersion was annealed to crystallize the P(VDF-TrFE) for ferroelectricity β-phase. A NCs dispersion was used in a dissolve solvent of photoactive materials, and fabricated inverted OPVs. In this poster details of experimental conditions and results will also be discussed.

Authors : A. Masuhara, N. Ito, J Matsui, M. C. Scharber, P. Stadler, C. Yumusak, M. S. White, N. S. Sariciftci, and T. Yoshida
Affiliations : Yamagata University; Osaka University; Johannes Kepler University Linz; The University of Vermont

Resume : Almost bulk-hetero junction forms nanostructure by annealing. The phase separations by annealing depend on inherent nature of molecules. Therefore precise control of nano domain size and shape are difficult. In addition, from the viewpoint of contact area of p-n organic semiconductor, carrier production and transport are advantageous, and therefore columnar structure is the optimal. Nakamura’s group has been succeeded in construction of columnar structure using heat transformation materials. But, this technique needs the advanced synthetic technique. Therefore, we tried fabrication of columnar-like structure by simple technique such as electrophoretic deposition and liquid-liquid interfacial assembly technique using organic semiconductor nanocrystals. By using this technique, we can simplify the controlling inner structure of OPV. Along these backgrounds, our final purpose is fabrication of the precise columnar-like nanostructure using nanocrystals for organic solar cells. In this paper, as a first step to achieve the final purpose, we investigated CO2 effect for nanocrystal growth inhibition of C60 in reprecipitation method. For example, when we use (S)-(-)-1-phenylethylamine as a good solvent and methanol and ethanol as a poor solvent in the reprecipitation, nanocrystal growth was inhibited. In addition, (S)-(-)-1-phenylethylamine was used as an additive, we could also inhibit nanocrystal growth. The reason for inhabitation of the nanocrystal growth has not been clearly understood. However, it is speculated that CO2 in the reprecipitation system plays a vital role on the crystal growth inhabitation. CO2 react with atomic nitrogen in the reprecipitation medium and production of reaction generated on the surface of nanocrystals. The obtained production is a causal force for inhabitation of the nanocrystal growth. Finally our approach for investigating C60 nanocrystals growth inhabitation will be presented.

Authors : Shaimaa A. Mohamed(a, b,c), Jacek Gasiorowski (d, e), Kurt Hingerld (d), Dietrich R.T. Zahn (e), Markus C. Scharber(a), Salah S.A. Obayya (b), Mabrouk K. El-Mansy(c), Niyazi S. Sariciftci(a), Daniel A.M. Egbe (a), Philipp Stadler (a).
Affiliations : a) Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, A-4040 Linz, Austria b) Center for Photonic and Smart Materials (CPSM), Zewail City of Science and Technology, Sheikh Zayed District, 6th of October City, 12588, Giza, Egypt c) Department of Physics, Faculty of Science, Benha University, Stadium Street, 13518 Benha, Egypt d) Center for Surface- and Nanoanalytics, Johannes Kepler University Linz, Altenbergerstr. 69, 4020 Linz, Austria e) Technische Universität Chemnitz, Semiconductor Physics, 09107 Chemnitz, Germany

Resume : A crucial element in optimizing organic solar cells relies on the efficient extraction of the carriers at the interfaces in combination with an adapted light management. In this work, we introduced a solution-processed Copper (I) iodide as a hole-selective and transparent electrode for an organic solar cell. We took the view to its optical and electrical properties as well as its discrete applications in a photovoltaic device. Therefore, we use an anthracene-containing PPE–PPV block–copolymers bulk-heterojunction solar cell, which has shown remarkable performances recently. Our study shows that copper iodide offers excellent properties as p-type selective and transparent contact – it represents a stable, solution-processible inorganic material, suitable as a serious alternative to commonly used PEDOT:PSS.

Authors : Halime Coskun*a, Abdalaziz Aljaboura,b, Dominik Farkaa, Philipp Stadlera, Niyazi Serdar Sariciftcia
Affiliations : a Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University of Linz, A-4040 Linz, Austria b Advanced Technology Research and Application Center, Department of Chemical Engineering, Selcuk University, 42075, Konya, Turkey

Resume : Melanins are naturally occurring pigments responsible for eye, hair and skin colors in animals. They can be distinguished between the black, insoluble eumelanin and the yellow to red-brown pigment pheomelanin. [1, 2] Polydopamine is a major pigment of the eumelanin family. Due to similarities in optical, electrical and magnetic properties similar to melanins, polydopamine has attracted much attention for broad family applications such as coating material or biomedical applications. Although the synthesis of poyldopamine is straightforward from dopaminhydrochlorid polymerized via oxidation in solution, or electropolymerization or enzymatic oxidation, the important limiting factors are the less defined structure of the material as well as the inhomogenity of film formation. [3] Herein we report a new synthetic pathway for the polydopamine film formation. We apply the chemical vapor deposition technique in a tube furnace in the presence of dopaminhydrochlorid in order to form polydopamine films directly on desired substances. The films obtained in this manner are investigated optically, spectro-electrochemically and electrically. [1] P. J. Gonçalves, O. Baffa Filho, C. F. O. Graeff, J. Appl. Phys., 99, 104701, 2006 [2] Marco d’Ischia, Alessandra Napolitano, Vincent Ball, Chun-Teh Chen, Markus J. Buehler, Acc. Chem. Res., 47, 3541−3550, 2014 [3] Yanlan Liu, Kelong Ai, Lehui Lu, Chem. Rev., 114, 5057−5115, 2014

Authors : Pavel Urbanek, Ivo Kuritka
Affiliations : Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Tr. T. Bati 5678, 760 01 Zlín, Czech Republic; Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Tr. T. Bati 5678, 760 01 Zlín, Czech Republic

Resume : We present a fundamental experimental study based on the optical and fluorescence investigation of thin σ- and π-conjugated polymer films, where the dependence of optical and optoelectrical properties on film thickness ranging from nano- to microscale was studied. Extensive and detailed study was performed and observed spectral shifts in emission and excitation spectra and UV degradation retardation point towards the conclusions that there exists a threshold thickness where the material degradation behavior, electron delocalization and structure suddenly change. The development of well aligned polymeric chain structure between the nano- and micrometer thickness (on the mesoscale) was shown responsible for the manifested phenomena. As representatives of σ-conjugated polymer poly(methylphenylsilane) (PMPSi) and copolymer poly[(dimethylsilane)-(methylphenylsilane)] (P[DMSi-MPSi]) were used. On the other hand, as representatives of π-conjugated polymers were used Poly(9,9-di-(2-ethylhexyl)-9H-fluorene-2,7-vinylene), Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] and Poly(9,9-dioctylfluorene-alt-benzothiadiazole) were used. Films were prepared by the spin coating method using spin coater Laurell WS-650-MZ-23NPP and by drop-casting from the solution in mixture of toluene and chloroform. The absorption spectra were measured by the UV/VIS Spectrometer Cary 100 (Varian) and by Lambda 1050 UV/VIS/NIR spectrometer from Perkin Elmer. The fluorimeter FSL 920 from Edinburgh Instruments (UK) was used for the measuring of PL spectra. The thickness of films varied from 10 to 1000 nm, depending on process conditions. The thickness was measured by using the profilometer Dektak XT-E (Bruker) with resolution less than 1 nm. In case of σ-conjugated polymers, the material thicker than critical 500 nm has extremely small Stokes shift, maximum extended σ-delocalization along the silicon polymer backbone and exhibits remarkable UV degradation slowdown and self-recovery ability. On the contrary, the electronic properties of thin films below 80 nm resemble those of random coils in solutions. The films of moderate thickness show relatively steep transition between these two modes of structural ordering and resulting properties. In case of π-conjugated polymers, we have observed that the microstructure of the thin conjugated polymer film may vary with the film thickness in a non-trivial way and that it is allied to different levels of manifestation of nonlocalized (aggregate states) and localized (intrachain) transitions. The competitive interplay between these two modes due to electronic-vibrational coupling is governed by the development of intrachain ordering and by the ordering level of π-stacking of polymer chains of π-conjugated polymers. We have shown that the microstructure changes from the dominant chain conformations promoting intrachain interaction in thin films of tens nm up to the structure with increased ordering of more ordered domains and prevailing chain stacking which is manifested by higher degree of interchain interaction in the films with thickness of hundreds nm. Moreover we observed a thickness threshold in PL emission, where PL emission changes suddenly its character from prevailing intrachain interaction to the behavior promoted by π-stacking as proven by the study of the vibronic structure of the emission peak. Altogether, we consider this complex phenomenon as a consequence of the mesoscale effect, which is an only recently introduced concept in polymer thin films.

Authors : Philipp Stadler,a* Daniele Marinotto,b,c Silvia Giulia Danelli,c Anna Giaretta,c Elena Lucenti,b Elisa Tordin,a Renato Ugo,c and Elena Cariati*c
Affiliations : aInstituto di Organic Solar Cells (LIOS) and Institute of Physical Chemistry, Johannes Kepler University Linz, Altenberger-str. 69, 4040 Linz, Austria bIstituto di Scienze e Tecnologie Molecolari del CNR (ISTM-CNR), via Golgi 19, 20133 Milano, Italy and UdR di Milano dell?INSTM. cDipartimento di Chimica and Centro di Eccellenza CIMAINA dell?Università degli Studi di Milano, UdR dell?INSTM, 20133 Milano, Italy

Resume : Inorganic-organic hybrid materials have shown excellent optoelectronic device performances from single-layer solution-processed thin-films. Their electronic bands are coupled to the ionic interactions within the organic and the inorganic moieties. Despite high-performances in lead-containing perovskite structures, detrimental aspects shadow recent efforts in solar cells suffering from instability and high environmental impact. We therefore present an alternative material class, which relies on a similar concept of inorganic-organic hybrid entanglement. The materials of interest are copper-iodide-based complexes readily used for non-linear optics. In particular the system [DAMS][Cu5I6] offers superior stability up to 250°C. We highlight all aspects of the solution-based film processing elucidating the potential to serve as versatile and robust active material for powerful lead-free alternative emerging solar cells.

Authors : Oleksandra Korovyanko1,2, Mykhailo Sytnyk3,4, Eric Daniel Głowacki1, Wolfgang Heiss3,4, and Philipp Stadler1
Affiliations : 1 Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University Linz, Altenberger Straße 69, 4040, Linz, Austria 2Chernivtsi National University, 2, Kotsyubynskogo, 58012, Chernivtsi, Ukraine 3 Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstraße 7, 91058 Erlangen, Germany, and 4Energie Campus Nürnberg (EnCN), Fürther Straße 250, 90429 Nürnberg, Germany

Resume : Ligand exchange strategy introduce a viable alternative for solution-processing lead sulfide quantum dots (PbS QDs), significantly expanding the scope of applications for this class of materials. Colloidal PbS QDs after synthesis are typically surrounded by long aliphatic ligands that provide solubility, surface passivation and prevent ripening or aggregation. These ligands, however, also act as a barrier to charge transfer and transport between neighboring QDs, and must therefore be removed for electronic device applications. Searching an appropriate ligand is of utmost importance for the optimization of NC films for light harvesting devices and photodetectors. The purpose of this research is to follow ligand replacement for solution-processed oleate-caped PbS QDs with extremely small inorganic weakly coordinating anions like BH4. We performed several solid-state ligand exchange strategies for PbS colloidal NCs in combine with complexity investigations of optical and photovoltaic properties of obtained material both before and after ligand exchange procedure. Different types of device structure architecture were used to investigate the effect of ligand exchange for device fabrication based on PbS QDs solids. The optimal device structure so called “inverted geometry” made of PbS NCs capped with extremely small ligands thin layers post-deposition procedure were presented, exhibiting high light responsivity and photocurrent values of more than 20 mA/cm2 with relatively lower open circuit voltage and fill factor. This high performance is enabled by a combination of high photosensitivity of the PbS QDs and effective electron transport, enabling efficient solution-processed field-effect transistors (FETs), solar cells,and photodetectors.

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Perovskite Solar Cells : Ken-ichi Nakayama
Authors : Joseph Berry, Jeff Blackburn, Anne-Marie Dowgiallo, Jeffery Christians, Andrew Ferguson, Maikel van Hest, Rachelle Ihly, Michael Irwin, Zhen Li, Joseph Luther, David Ostrowski, Obadiah Reid, Matthew Reese, Erin Sanehira, Philip Schulz, Noah Stanton, Mengjin Yang, Kai Zhu
Affiliations : National Renewable Energy Laboratory

Resume : Photovoltaic devices based on hybrid organic-inorganic perovskite absorbers have reached outstanding performance over the past few years, surpassing power conversion efficiency of over 22%. In this talk we discuss the role of the interface in optimizing device performance as measured by both power conversion efficiency and stability. We present an examination of different perovskite active layers and interfacial electronic structure of these remarkable materials. Interface formation of the active layer with different carrier transport materials has direct implications for performance of the resulting devices. We present interface studies, which permit identification of charge transfer mechanisms across the interface with chemical specificity and insight into the requirements for realizing high performance devices. We will also discuss chances in the interface and change transport properties across different halide/hybrid perovskite absorber layers as well as different process approaches. Our findings from surface science approaches are combined with time resolved spectroscopy, structural studies and device level studies to validate impacts and demonstrate their technological relevance for these materials in the PV application.

Authors : Martin Kaltenbrunner
Affiliations : Johannes Kepler University Soft Matter Physics

Resume : Flexibility, compliance and weight will turn out to be key metrics for future electronic appliances and their power supplies. Imperceptible electronic wraps integrate nanometer thin film active components on sub-2-μm polymer foils and create devices unmatched in mechanical flexibility, stretchability and weight. Emerging applications like solar powered aviation or wearable electronics require photovoltaic technologies that are highly efficient, light-weight, low-cost, and stable during operation. Organolead halide perovskites constitute a highly promising class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. In this talk we introduce methods, materials and design strategies for ultrathin (3 µm), highly flexible perovskite solar cells with stabilized 12% efficiency and a record power-per-weight as high as 23 W/g. To facilitate air stable operation, we introduce a chromium oxide-chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. We show prolonged stable operation in the maximum power point in ambient air of non-encapsulated planar perovskite solar cells with gold, and low-cost copper and aluminium electrodes. The use of a transparent polymer electrode treated with dimethylsulphoxide (DMSO) as bottom layer allows the deposition - from solution at low temperature - of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles - from airplanes to quad-copters and weather balloons - for environmental and industrial monitoring, rescue and emergency response, and tactical security applications. In a hybrid architecture laminated atop pre-strained elastomers, such solar cells are highly stretchable and conformable. We introduce surface structuring as a light-trapping microstructure for improved efficiency. Prolonged operational lifetime and stability towards water ingress by superhydrophobic coatings will be discussed. We acknowledge funding from the FWF Wittgenstein award and the ERC advanced investigators grant “Soft Map”. M. Kaltenbrunner et al., Nature Communications 3, 770 (2012) M. Kaltenbrunner et al., Nature 499, 458 (2013) M. Kaltenbrunner et al., Nature Materials 14, 1032-1039 (2015)

Authors : Hyungdo Kim, Hideo Ohkita, Hiroaki Benten, Shinzaburo Ito
Affiliations : Kyoto University, Kyoto, Japan

Resume : The power conversion efficiency (PCE) of perovskite solar cells based on organometal halides such as CH3NH3PbI3 and CH3NH3PbI3−xClx has skyrocketed from 3.8 to more than 20% in the past several years. Recent studies have shown that some factors underlying such efficient device performance are due to excellent light harvesting property, long charge carrier diffusion length, high charge carrier mobility, ultrafast charge generation and slow charge carrier recombination, and small exciton binding energy. However, most of perovskite solar cells exhibit poor reproducibility in the device performance with J–V hysteresis even though they are fabricated by the same fabrication procedures. This is probably because crystalline growth of perovskite materials cannot be well controlled for efficient and reproducible photovoltaic performances. Consequently, it has been difficult to discuss the relationship between the photovoltaic performance and device structure quantitatively. In this study, we fabricated planar heterojunction solar cells with a layer structure of FTO/d-TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au in which dense CH3NH3PbI3 layers were prepared by fast deposition–crystallization (FDC) method. The average grain size of CH3NH3PbI3 was varied from 100 to 500 nm by changing the concentration of stock solutions. The perovskite layer obtained consists of monograins in the direction normal to the substrate. As a result, the CH3NH3PbI3 perovskite solar cells exhibiting 19% achieved for the largest grain size of ≈500 nm by optimizing the condition of device fabrication. Using these devices, we investigated the relationship between the open-circuit voltage (Voc) and the grain size of perovskites. Based on analysis of the intensity-dependent Voc by considering both direct and SRH recombinations, we found that the trap density (Nt) decreases with increasing grain size of perovskites, leading to increasing Voc. This enhancement is ascribed to the reduced trap-assisted SRH recombination. On the basis of the experimental data, we further discuss the potential for improvement in the device performance of perovskite solar cells if Nt of perovskite films was suppressed to the order of <10^13 cm−3 as reported for mm-scale perovskite crystals.

Authors : B. Slimi(a,b,c), M. Mollar(a), I. Ben Assaker(b), I. Kriaa(c), R. Chtourou(b), B. Marí(a)
Affiliations : a) Institut de Disseny I Fabricació, Universitat Politècnica de València, Camí de Vera s/n, 46022 València, SPAIN; b) Laboratoire Photovoltaïques, Centre de Recherches et des Technologies de l’Energie Technopole Borj Cedria, Bp 95, Hammam Lif 2050, Tunisie; c) Faculté des Sciences de Bizerte, Université de Carthage, Tunisie; d) Laboratoire de Chimie Moléculaire Organique, 5 Avenue Taha Houssein Monfleury, 1089 Tunis, Tunisie

Resume : Formamidinium (FA) lead iodide/bromide perovskite thin films were synthetized in a single step from a solution containing a mixture of FAI, PbI2 and FABr, PbBr2, respectively. Then by mixing halide components in the desired proportions FAPbI3Br3-x perovskite thin films were also produced. Perovskite thin films were deposited from then mentioned solutions onto indium-tin oxide substrates by spin-coating method. X-ray diffraction analyses indicated the formation of a cubic phase Pm-3m in all composition range (0≤x≤ 3). Mixed formamidinium lead iodide/bromide perovskites showed a high absorbance in the UV–vis range. The band gap energy of mixed thin films was estimated from absorbance spectral measurements and it can be tuned by choosing the desired x ratio for the halides. It was found that the onset of the absorption edge for FAPbBr3-xIx (x ≤ 1) thin films is ranging between 1.47 to 2.2 eV. Photoluminescence emission energies for mixed halide perovskites presented intermediate values from 810.4 nm for FAPbI3 to 547.3 nm for FAPbBr3.

Fundamental Processes in Perovskite Semiconductors : Joseph Berry
Authors : Emilio J. Palomares
Affiliations : 1. Institute of Chemical Research of Catalonia ( ICIQ). Avda. Països Catalans, 16. Tarragona. E-43007. Spain. 2. ICREA. Passeig Lluís Companys 23. Barcelona. E-08010. Spain

Resume : During my lecture I will present our latest results on the characterization of different type of devices that include MAPI as light harvesting material using advanced photo-induced time resolved techniques1-4. Using PICE (Photo-induced charge extraction), PIT-PV (Photo-induced Transient PhotoVoltage) and other techniques, we have been able to distinguish between capacitive electronic charge, and a larger amount of charge due to the intrinsic properties of the perovskite material. Moreover, the results allow us to compare different materials, used as hole transport materials (HTM), and the relationship between their HOMO and LUMO energy levels, the solar cell efficiency and the charge losses due to interfacial charge recombination processes occurring at the device under illumination. These techniques and the measurements carried out are key to understand the device function and improve further the efficiency and stability on perovskite MAPI based solar cells.

Authors : G. A. Nemnes (1,2) , Cristina Besleaga (3) , A. G. Tomulescu (3) , Ioana Pintilie (3) , L. Pintilie (3) , K. Torfason (4) , A. Manolescu (4)
Affiliations : (1) Horia Hulubei National Institute for Physics and Nuclear Engineering, 077126, Magurele-Ilfov, Romania ; (2) University of Bucharest, Faculty of Physics, MDEO Research Center, 077125, Magurele-Ilfov, Romania ; (3) National Institute of Materials Physics, Atomistilor 105 bis, Magurele, 077125, Romania ; (4) School of Science and Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik, Iceland

Resume : In the past few years halide perovskite based solar cells have shown an unprecedentedly rapid development in terms of photoconversion efficiency (PCE). While the high PCEs and potentially low production costs are important assets, a number of challenges and open questions still need to be addressed. One of these is the anomalous dependence of the current-voltage response on the bias scan direction, rate and range [1]. The origin of the dynamic hysteresis is still under debate and has been attributed to different phenomena, such as ferroelectric effects, trapping and de-trapping of the charges and ion migration [2]. We introduce a dynamic electrical model in order to investigate the hysteresis effects in the I-V characteristics of perovskite based solar cells. By making a simple ansatz for the polarization relaxation, our model is able to reproduce qualitatively and quantitatively detailed features of the measured I-V characteristics. Pre-poling effects are discussed, pointing out the differences between initially over- and under-polarized samples. Furthermore, the dynamic hysteresis is measured and analyzed with respect to changing the bias scan rate, the obtained results matching also other experimental reported data [3]. Additional analysis is performed by taking into account single and multiple relaxation times. [1] Bo Chen, Mengjin Yang, Shashank Priya and Kai Zhu, J. Phys. Chem. Lett. 7, 905 (2016) ; [2] S. van Reenen, M. Kemerink, and H. J. Snaith, J. Phys. Chem. Lett. 6, 3808 (2015) ; [3] W. Tress, N. Marinova, T. Moehl, S. M. Zakeeruddin, M. K. Nazeeruddin and M. Gratzel, Energy Environ. Sci. 8, 995 (2015).

Authors : Satyaprasad P Senanayak, Bingyan Yang, Aditya Sadhanala, Prof. Sir Richard Friend and Prof. Henning Sirringhaus
Affiliations : Optoelectronics Group, Department of Physics, Cavendish Laboratory,University of Cambridge, JJ Thomson Avenue, CB3 0HE

Resume : Organometal halide based perovskite are emerging materials for wide range of optoelectronic applications which includes high efficiency solar cells, color pure LEDs and optical pumped lasers. Despite this a lot needs to be understood regarding the underlying charge transport which required fabrication of field effect transistors. Here, we report the demonstration of a high performance field effect transistor fabricated from iodide perovskite material at room temperature. The devices exhibit clean saturation behavior with electron field effect mobility > 3 cm2/Vs and current modulation in the range of 10^6 – 10^7 which are till date the best performance achieved with these class of materials. This high performance is attributed to a combination of novel film fabrication technique and device engineering strategies. Detailed understanding of the observed band-like transport phenomenon is developed by tuning the different sources of dynamic and static disorder prevalent in the system. These finding are expected to pave way for developing next generation electronic application from perovskite materials.

Authors : Sebastian F. Hoefler< sup>a< /sup>, Indira Zahirovic< sup>a< /sup>, Thomas Rath< sup>a< /sup>, Christine Latal< sup>b< /sup>, Dorothee Hippler< sup>b< /sup>, Gregor Trimmel< sup>a< /sup>
Affiliations : < p>< sup>a< /sup> Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria< p> < p align="justify">< sup>b< /sup> Institute of Applied Geosciences, Graz University of Technology, Rechbauerstraße 12, 8010 Graz, Austria< p>

Resume : < p align="justify">Bismuth(III) halide perovskites are currently investigated as alternative solution-processable absorber materials for photovoltaic applications to circumvent the toxicity and stability issue of lead halide perovskites. In addition to the low toxicity and ambient stability, bismuth(III) halide perovskites are due to their optical bandgaps in the range of 2.0-2.4 eV promising absorber materials in particular for multi-junction solar cells.< sup>[1,2]< /sup> < p> < p align="justify">The focus of this contribution is on alternative hybrid organic-inorganic bismuth(III) halide perovskites with organic methylammonium (CH< sub>3< /sub>NH< sub>3< /sub>< sup>+< /sup>) as A-site cation, inorganic bismuth (Bi< sup>3+< /sup>) as B-site cation and halide counter ions (I< sup>-< /sup>, Cl< sup>-< /sup>) incorporated on the X-site of the perovskite structure. The perovskite absorber materials (CH< sub>3< /sub>NH< sub>3< /sub>)< sub>3< /sub>Bi< sub>2< /sub>I< sub>9< /sub> and (CH< sub>3< /sub>NH< sub>3< /sub>)< sub>3< /sub>Bi< sub>2< /sub>I< sub>9-x< /sub>Cl< sub>x< /sub> were prepared in a one-step, solution-based processing route at low temperatures and were evaluated with regard to their photovoltaic performance in planar (compact TiO< sub>2< /sub>) and meso-structured (compact TiO< sub>2< /sub>/mesoporous TiO< sub>2< /sub>) perovskite solar cells. < p> < p align="justify">In addition, the influence of fullerene-based passivation layers on the characteristic solar cell parameters as well as hysteresis effects was investigated. Therefore, interlayers of [6,6]-phenyl-C< sub>71< /sub>-butyric acid methyl ester ([70]PCBM) and indene-C< sub>60< /sub> bisadduct (ICBA) were introduced between the electron-transport and the perovskite layers.< sup>[3]< /sup> The bismuth(III) halide perovskites were characterized optically (UV/VIS spectroscopy, light microscopy), structurally (X-ray diffraction), and electronically with regard to their performance as absorber materials in perovskite solar cells. < p> < p> References < p> < p align="justify">[1] Eckhardt et al., Chem. Commun. 2016, 52, 3058-3060.< p>[2] Park et al., Adv. Mater. 2015, 27, 6806-6813.< p>[3] Ip et al., Appl. Phys. Lett. 2015, 106 (14), 143902.< /p>

Authors : Dorota Brzuska-Kamoda (1), Karolina Pietak (1), Grzegorz Matyszczak (1), Michal Wrzecionek (1), Daniel Jastrzebski (1), Slawomir Podsiadlo (1), Cezariusz Jastrzebski (2), Roman Gajda (3), Krzysztof Wozniak (3)
Affiliations : (1) Faculty of Chemistry, Warsaw University of Technology; Noakowskiego 3, 00-664 Warsaw, Poland (2) Faculty of Physics, Warsaw University of Technology; Koszykowa 75, 00-662 Warsaw, Poland (3) Chemistry Department, Warsaw Univeristy, Pasteura 1, 02-093 Warsaw, Poland

Resume : In times of very high electricity consumption, scientists try to improve amount of electricity produced from all kinds of energy sources. In photovoltaics, to gain the low-cost and non-toxic materials that will absorb light in a wide range of wavelength is one of greatest importance. An example of such a material could be MnSnS3. This compound has not been synthetized yet, but some attempts were made, and the first samples are being tested already. There are indications that MnSnS3 will show semiconductor and ferromagnetic properties. These give some hope of using this material for improving efficiency of solar cells.

Stability of Perovskite PV : Emilio J. Palomares
Authors : Dr. Saif Haque
Affiliations : Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom

Resume : Solution processed hybrid inorganic-organic materials (e.g metal chalgodenide and hybrid perovskites) are generating huge interest for application in range of optoelectronic and electronic devices such as solar cells, light emitting diodes and transistors. In this presentation, I will start by talking about some of our recent work on hybrid perovskites and in particular, our work aimed at identifying the key factors affecting the stability of hybrid perovskite solar cells. In recent years, spectacular advances have been made in the power conversion efficiency of perovskite solar cells with recent reports of devices exhibiting PCE’s over 20%. However, the relatively low stability of this technology still remains a concern. A number of factors have been shown to influence the stability of perovskite materials; these include water, UV and temperature. In this talk I will consider the affect of light and oxygen on the stability of perovskite materials and devices [1, 2]. I will first consider the effect of light and oxygen on the absorption properties of the films, device performance / stability and photo-induced charge separation yields. I will then go onto discuss the mechanism of how light and oxygen causes degradation of the perovskite absorber [2]. I will then go onto outline two strategies that can be used to reduce the severity of light and oxygen degradation in perovskite materials and devices, namely (i) the use of electron extraction layers within the deices structure [3] and (ii) via structural modification of perovskite absorber itself.  In the final part of the talk will conclude by discussing some of the lessons that can be learnt from the hybrid perovskite technology to the design of more efficient and stable metal chalogenide (e.g. tin(II) sulfide) solar cells. References: [1] O’Mahony et al. J. Mater. Chem. A. 2015, 3,7219 –7223. [2] Aristidou et al. Angew. Chemie. Int. Ed. 2015, 54,8208 –8212   [3] Bryant et. al. Energy Environ. Sci., 2016, 9, 1655-1660

Authors : Martina Stumpp, Raffael Ruess, Manuel Weiß, Jonas Horn, Derck Schlettwein
Affiliations : Justus-Liebig-University Giessen, Institute of Applied Physics, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany

Resume : Organic-Inorganic Hybrid Perovskites have not only turned out to be technically very promising as absorber layers in high-efficiency large-scale photovoltaics but also provide a number of challenges on the level of basic research. From our point of view, three central questions still have to be answered: - How can the layers be stabilized against chemical decomposition ? In this contribution we will discuss detailed investigations on the hydrolysis characteristics of methylammonium lead halides CH3NH3Pb(I1-xBrx)3 in the dark and under illumination [1]. Different degradation mechanisms were characterized. Bromide can successfully suppress the transformation of the perovskite to the monohydrate, presumably caused by stronger hydrogen bonding interactions with the organic cation. Under illumination in humid air, however, a rather rapid decomposition of the perovskites was still observed. - Can the toxic element Pb be replaced ? Tin is one of the chemical elements discussed to replace lead. We have prepared layers of methylammonium tin iodide (CH3NH3SnI3) in a two-step process by spin-coating a solution of methylammonium iodide (MAI) onto SnI2 prepared by physical vapor deposition [2]. Full surface coverage of the substrate was reached, the films consisted of 200 nm large crystalline domains and the films turned out to be remarkably stable even after exposure to air. - What is the origin of electrical hysteresis often observed in layers ? CH3NH3PbI¬3 and CH3NH3Pb(I¬0.95Br0.05)3 were prepared as thin films via different established deposition techniques also on microstructured gold electrode arrays on Si/SiO2 wafers to characterize the hysteresis of I-V characteristics in the dark and under illumination [3]. Persistent changes in the polarization of the perovskite films was observed following positive or negative poling. At higher bias voltages additional inverted hysteresis loops were measured pointing at a decrease in barrier width at the blocking perovskite/metal contact by migrating iodide ions leading to characteristics of two diodes operated back-to-back. - Implications of these different results for use of the materials for next-generation solar cell devices are discussed. [1]. R. Ruess, F. Benfer, F. Böcher, M. Stumpp and D. Schlettwein, ChemPhysChem, Article first published online: 3 MAR 2016 DOI: 10.1002/cphc.201501168. [2]. M. Weiss, J. Horn, C. Richter, D. Schlettwein, Phys. Status Solidi A, 213, 975-981 (2016). [3]. M. Stumpp, R. Ruess, J. Horn, J. Tinz, C. Richter, D. Schlettwein, Phys. Status Solidi A, 2016, 213, 38–45.

Authors : Thomas Rath, Sebastian Dunst, Gregor Trimmel
Affiliations : Institute for Chemistry and Technology of Materials (ICTM), NAWI Graz, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria

Resume : Besides hybrid perovskite-based solar cells, which have attracted much attention in recent years, also the interest in hybrid polymer/nanocrystal photovoltaic technologies has increased markedly. Polymer/nanocrystal solar cells have power conversion efficiencies now reaching 5.5% [1] and are promising due to their ability to incorporate the attractive qualities of both material classes, conjugated polymers and inorganic nanocrystals in one device. These hybrid solar cells can take advantage of the high absorption coefficients and easy solution-based processability of organic materials as well as the superior electronic properties and chemical stability of inorganic semiconductors.
The conventional approach to prepare polymer/nanocrystal hybrid absorber films is to blend a conjugated polymer with semiconducting nanocrystals, which are stabilized by capping agents. Besides the advantage that nanocrystals with well-defined sizes and shapes can be used, the main drawback of this approach is that the capping ligands can partly remain in the absorber layers, where they limit the efficient charge separation and transport in the final device. Consequently, in the last years, we have targeted our research on the in situ preparation of nanocrystals directly in the conjugated polymer film leading to ligand-free hybrid interfaces. Using metal xanthates as precursors, hybrid solar cells based on various metal sulfides and conjugated polymers have already been studied.[2-5]
Key issues to further develop these in situ prepared hybrid solar cells are an improved control of materials synthesis, a good control over nanomorphology formation as well as contacting the absorber layer with suitable selective electrode materials including proper interfacial layers. In this study, we therefore focused on electrode materials and the influence of device architecture (regular and inverted geometry) and different interlayers on the performance and lifetime of polymer/nanocrystal hybrid solar cells. The absorber layers of the investigated solar cells consist of the low band gap conjugated polymer PCDTBT and in situ prepared copper indium sulfide (CIS) nanocrystals.[6] In regular device architecture, the interlayers PEDOT:PSS, V2O5 and MoO3 were investigated as hole extraction layers between absorber layer and anode. Here, the best performance was obtained in solar cells with PEDOT:PSS interlayer. Preparing PCDTBT/CIS hybrid solar cells in inverted device architecture unveiled interesting results. In the device architecture glass/ITO/TiO2/PCDTBT-CIS/PEDOT:PSS/Ag, open circuit voltages up to 550 mV combined with high photocurrents could be obtained. Achieving such high photovoltages with this absorber material was so far only possible by using low work function metal electrodes like aluminum, which resulted in poor device stability. Using MoO3 as interlayer instead of PEDOT:PSS in inverted solar cells, led to similar photocurrents compared to devices with PEDOT:PSS interlayer, however, the observed photovoltages were significantly lower. In the inverted devices with PEDOT:PSS interlayer, only the fill factor is lower compared to solar cells in regular geometry, which is limiting the PCE of the inverted solar cells to 2.1% up to now. However, solar cells in inverted architecture having a PEDOT:PSS interlayer and an additional CIS layer show good stability and maintain their high open circuit voltages over hundreds of hours of continuous illumination.
[1] Z. Liu et al., Adv. Mater., 2013, 25, 5772.
[2] T. Rath et al., Hybrid Mater., 2014, 1, 15.
[3] A. J. MacLachlan et al., Adv. Funct. Mater., 2015, 25, 409.
[4] T. Rath et al., Adv. Energy Mater., 2011, 1, 1046.
[5] N. Bansal et al., Adv. Energy Mater., 2013, 3, 986.
[6] S. Dunst et al., Synth. Met., 2016, doi:10.1016/j.synthmet.2016.04.003.

Authors : Itaru Osaka
Affiliations : RIKEN, Center for Emergent Matter Science

Resume : Development of Semiconducting Polymers

Poster session : Tsukasa Yoshida
Authors : He Sun1, Lina Sun1, Takashi Sugiura,2 Matthew Schuette White3,4, Philipp Stadler4, Niyazi Serdar Sariciftci4, Akito Masuhara1 and Tsukasa Yoshida1*
Affiliations : 1 Research Center for Organic Electronics (ROEL), Yamagata University, Jonan 4-3-16, Yonezawa, Yamagata, 992-8510, Japan 2 Materials Chemistry Course, Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu 501-1193, Japan 3 Department of Physics, University of Vermont, Burlington, VT 05405, United States 4 Institute for Physical Chemistry/LIOS Johannes Kepler University Altenbergerstraße 69 4040 Linz, Austria

Resume : Nanoparticles of oxide semiconductors play crucial roles in mesoscopic solar cells such as dye-sensitized solar cells (DSSCs), quantum dot solar cells and perovskite solar cells. Not only the absolute size of the particles but also their shape and preferentially exposed crystal facets are expected to cause drastic changes in their performance, because it serves as the interface for carrier extraction and also for recombination. Also expected is the influence of the chemical stability of the light absorber (dye, Q-dot, perovskite) to be deposited on the oxide electron extracting layer. While titanium dioxide is widely used, zinc oxide (ZnO) is an attractive alternative due to its high electron mobility and flexibility in its structure control. We have succeeded in synthesis of size and structure controlled ZnO nanoparticles by rapid hydrothermal crystallization employing microwave radiation and structure directing agents (SDAs). Here, the synthetic methods, structural characterizations and their properties in DSSC applications are to be reported. Rapid microwave radiation for only 30 mins to aqueous solution containing Zn(CH3COO)2 and structure directing agents (SDAs) such as triethanolamine (TEOA) and 1,2,4,5-benzenetetracarboxylic acid (BTCA) with controlled pH by addition of KOH resulted in formation of differently shaped ZnO. The precipitates were centrifuged, washed and dried in oven. Well crystallized ZnO but with totally different morphology was obtained by using TEOA or BTCA. Use of TEOA resulted in nanoparticles with hexagonal and bi-pyramidal (HBP) shape in about 50 to 100 nm size. Combination of the observation techniques of transmission electron microscope (TEM), selected area electron diffraction (SAED) revealed that the axis connecting two tips of HBP corresponds to the c-axis of ZnO. While the rectangular sides in 6-fold symmetry obviously correspond to (100), the triangular facets could possibly be (101), (102) or (103). The angle between ridges and the horizontal line of HBP fell in the range between 38 and 41˚ from the scanning electron microscope (SEM) images, so that the triangle is most likely (102) with its occupancy to the total surface area of ca. 84%. On the other hand, the use of BTCA resulted in formation of nanosheet (NS) ZnO. TEM and SAED lattice images of NS identified that the mainly exposed facets are of the (100) planes of ZnO. Surface area and dye (D149) adsorption capability were checked for the synthesized ZnO in HBP and NS shapes in comparison with a commercial ZnO (MZ). Such difference was found for the area occupied a D149 molecule as 0.68 (commercial), 0.62 (HBP) and 1.2 (NS) nm2 indicating the dye adsorption stability on (102) ZnO crystal facets is greater than that on (100). Besides, the synthesized ZnO shows some interesting properties applying to DSSCs. The cells employing (100) dominated NS ZnO achieved about 30mV higher Voc than MZ and 40mV higher than that of HBP when using D149. The higher surface concentration of the dye on (102) resulted in a higher IPCE as compared to the other samples and Jsc is 2 mA/cm2 higher than that on (100) , despite of the reduced Voc and FF to limit the conversion efficiency. Their differences in charge extract properties are also studied and discussed.

Authors : < BR>Indira Zahirovic, Sebastian F. Hoefler, Thomas Rath, Christine Buchmaier, Birgit Kunert, Roland Resel, Gregor Trimmel
Affiliations : < BR>Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria; < BR>Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria

Resume : Organo-lead halide perovskite solar cells can be prepared in a cheap an energy-efficient way and show high power conversion efficiencies already exceeding 20%. Not only high power conversion efficiencies, but also solution processability at low temperature make perovskite solar cells a very attractive method for solar energy conversion. The morphology of the perovskite films is one of the most critical issues to realize high efficient perovskite solar cells. Crucial process parameters to control the morphology of the perovskite films are the heating rate, annealing temperature and time.< sup>[1]< /sup> They have also a great effect on the structural, electronic and optical properties of the perovskite material.< sup>[1, 2, 3]< /sup> In order to investigate the different annealing conditions and coating techniques, solar cells were built on glass substrates coated with patterned indium tin oxide (ITO) films and have a configuration glass/ ITO/ c-TiO< Sub>x< /Sub>/ mp-TiO< Sub>x< /Sub>/ CH< Sub>3< /Sub>NH< Sub>3< /Sub>PbI< Sub>3< /Sub>/ Spiro-OMeTAD/ Au. In the first approach, perovskite films were deposited by doctor blading using precursor solutions in different dilutions. For further experiments, a dilution of 1:4 was chosen because solar cells prepared with this concentration revealed the best power conversion efficiency (PCE), highest I< Sub>SC< /Sub> and highest V< Sub>OC< /Sub>. In the second approach, spin coating was used for the preparation of the perovskite absorber layers. In the annealing temperature experiments, the perovskite films were annealed at 70, 80, 90 and 100°C with a one-step method and from 70 to 100°C with a slow annealing multi-step method as well as by gradual heating at different rates. It was evident that the solar cells annealed at 90°C had the best performance. Also the open circuit voltage and the fill factor showed the highest values for perovskite films prepared at this temperature. The I< Sub>SC< /Sub> is the only parameter which was highest at an annealing temperature of 100°C and decreased when lower annealing temperatures have been applied. For the determination of the solar cell parameters, current voltage curves were measured and optical properties of the layers were characterized using UV/Vis spectroscopy. Characteristics like roughness, crystallinity, chemical composition, purity and morphology of the prepared perovskite films were investigated by surface profilometry, X-ray diffraction and scanning electron microscopy. < p> References: < BR> [1] Eperon GE et al., Adv. Funct. Mater., 24 (2014), pp. 151?157 < BR> [2] Dualeh A et al., Adv. Funct. Mater., 24 (2014), pp. 3250?3258 < BR> [3] Tripathi B et al., Sol. Energy Mater. Sol. Cells, 132 (2015), pp. 615?622

Authors : Dorothea Scheunemann, Sebastian Wilken, Jürgen Parisi, Holger Borchert
Affiliations : Energy and Semiconductor Research Laboratory, Department of Physics, University of Oldenburg, Carl-von-Ossietzky-Straße 9–11, 26129 Oldenburg, Germany.

Resume : Heterojunction solar cells consisting of a wide band gap n-type semiconductor and a p-type nanocrystal film as absorber have shown remarkable improvements in performance in the last decade. However, this progress is limited to merely two materials, PbS and PbSe, while solar cells based on other materials, as for example copper-based compounds show lower power conversion efficiencies. Much less effort has been made to gain a deeper understanding of factors limiting the performance of these material systems. Here, we present a detailed study on the photocurrent loss mechanisms in nanocrystalline CuInS2/ZnO heterojunction solar cells. For this purpose, we combined steady-state characterization methods using different illumination conditions with transient photocurrent and photovoltage measurements. We demonstrate the presence of two different loss mechanisms: An extraction barrier at the CuInS2/ZnO interface, which can be reduced upon illumination with UV light, as well as significant trap-assisted recombination in the CuInS2 layer. The presented results confirm the potential of heterojunctions made from CuInS2 and ZnO nanocrystals in solution producible solar cells, but also clearly highlight the importance of a substantial reduction of sub-band gap states to improve the performance.

Authors : Daniel Jastrzebski (1), Piotr Ostapowicz (1), Grzegorz Matyszczak (1), Michal Wrzecionek (1), Karolina Pietak (1), Dorota Brzuska-Kamoda (1), Cezariusz Jastrzebski (2), Slawomir Podsiadlo (1)
Affiliations : (1) Faculty of Chemistry, Warsaw University of Technology; Noakowskiego 3, 00-664 Warsaw, Poland (2) Faculty of Physics, Warsaw University of Technology; Koszykowa 75, 00-662 Warsaw, Poland

Resume : A growing interest of two-dimensional (2D) layered nanostructures has been observed due to their peculiar nanoscale phenomena and promising future applications. Particularly gallium (II) sulfide (GaS) nanoplates show appealing features as novel materials for electronics. Single crystals of gallium(II) sulfide were obtained by chemical transport method. We present a method of obtaining single GaS crystals size up to 2,5x2x0,5mm useful for a single-layer exfoliation. The crystals were prepared from elements with amounts of iodine in quartz ampoules closed under vacuum and heated in a tube furnace at 750°C for 10 to 30 days. The obtained crystals and layers were characterized by X-ray, TEM and Raman studies.

Authors : Yuji Hirai, He Sun, Yuta Matsushima, Tsukasa Yoshida
Affiliations : Yamagata University

Resume : ZnO has various applications in photocatalysis, transparent electrode, sensors and solar cells. In this study, ZnO nanocrystals are synthesized via a microwave (MW)-assisted hydrothermal reaction employing benzene carboxylic acids (BCs) as structure directing agents (SDAs). Evolution of unique nano-sheet ZnO (NS ZnO) has been discovered and conditions for its structure control has been studied. Typically, an aqueous mixture of 0.1 M Zn (CH3COO) 2 0.1 M BC, such as 1, 2, 4, 5-benzenetetracarboxylic acid (BTCA), trimesic acid (TMA), trimellitic acid (TMLA), phthalic acid (PA), isophthalic acid (IPA) and terephthalic acid (TPA) whose pH was adjusted to ca. 13 by addition of KOH was put into a pressure-withstanding vessels and subjected to a 2.45 GHz MW radiation to promote reaction at 150°C for 30 min. The precipitates were washed, dried and analyzed by XRD, SEM and TEM. While NS ZnO of a few hundred nm width and a few tens of nm thickness, and with predominant exposure of (100) facets were obtained by addition of BTCA, TMA, TMLA, PA and IPA, a drastically different result was obtained with TPA. Crystalline nanoparticles seemingly that of Zn/TPA metal-organic framework (MOF) was formed. Due to insertion of TPA into the ZnO matrix, its reaction yield was in the range of 130% and showed a significant exothermic weight loss around 450°C in the TG-DTA analysis. Studies about the properties of NS ZnOs as well as Zn/IPA MOF are also under way.

Authors : Nobuyuki Nishiumi1, He Sun1, Philipp Stadler2, Tsukasa Yoshida1
Affiliations : 1; Yamagata University 2; Johannes Kepler University, Linz

Resume : Doping of cobalt ions into zinc oxide yields magnetic semiconducting properties to be a promising material in spintronic devices. Also, introduction of new bands arising from the d-orbital of the cobalt ion leads to a deep coloration of ZnO in the visible range, suggesting its possible application as a light absorber in solar cells. In this study, we have attempted microwave (MW)-assisted hydrothermal synthesis of oxide nanoparticles of zinc, cobalt and their mixtures. Aqueous solutions of 0.1 M ZnCl2 and 0.1 M CoCl2 were mixed at various ratios to which an appropriate amount of NaOH was added to achieve pH ca. 12. The precursor solution was put into a pressure-withstanding vessel and subjected to a 2.45 GHz MW radiation to promote reaction at 160°C for 30 min. The resultant precipitates were centrifugally separated, washed with water and ethanol, and dried at 100°C for overnight. While crystalline white nanoparticles of ZnO were obtained from ZnCl2 solution, those of black Co(OH)2 were obtained from CoCl2. For the mixed solutions, addition of CoCl2 up to ca. 30% still retained crystalline ZnO structure, although the powder turned into dark-green to black. Further addition of CoCl2 resulted in phase-separated co-precipitation of ZnO and Co(OH)2. It is likely that Co ion can be doped into ZnO as long as the Co concentration is kept small. Fabrication of thin film electrodes by printing of these nanoparticles and their photoelectrochemical studies are under way.

Authors : Satoru Toyoda, Akito Masuhara, Tsukasa Yoshida
Affiliations : Yamagata University

Resume : Solution processible lead halide perovskite solar cells have achieved strikingly high efficiencies over 20%. Carrier selective charge extraction layers play crucial roles in such devices, as TiO2 and spiro-OMeTAD are typically used for electron and hole, respectively, in the perovskite cells. Not only for the perovskite cells but also all other thin film p-i-n solar cells, these contact layers need to be optimized in terms of their energy levels, carrier mobility and chemical stability. The method of film fabrication should also be versatile and tunable for various kinds of thin film solar cells, facile for structure control and scaling up. In this context, electrochemical processing could bear advantages. We have developed a versatile method to electrodeposit thin films of poly-oxometallates (POM) of Ti(IV), Al(III), Si(IV), Nb(V) and Ta(V), hybridized with benzoquinone (Q) by anodic oxidation of hydroquinone (H2Q). When alkoxides of these metals are hydrolyzed with bulky tetra-alkylammonium hydroxides (R4NOH), they produce clear alkaline colloidal solution of layered POM stabilized by insertion of R4N . Oxidation of H2Q to Q releases proton to exchange with R4N , leading to an aggregation of the colloid to deposit (POM)(Q) hybrids. Annealing of these films result in formation of corresponding metal oxides. In case of Ti(IV), relatively compact and flat anatase TiO2 was obtained. Performance of such metal oxide layers is to be tested by employing perovskite as light absorber.

Authors : Yuki Tsuda1, He Sun1, Lina Sun1, Shuji Okada1, Philipp Stadler2, Tsukasa Yoshida1
Affiliations : 1; Yamagata University 2; Johannes Kepler University, Linz

Resume : Inorganic / organic layered hybrid compound of [DAMS ]Cu5I6 has been synthesized by Cariati et al. (DAMS : trans-4-(4-dimethylaminostyryl)-1-methylpyridinium) [1]. Due to a high ordering of the stilbazolium chromophore in a J-aggregate form, it gives a rise to SHG (second harmonic generation). In this study, we have attempted electrochemical self-assembly of CuSCN-DAST hybrid thin films by addition of DAST (4-N,N-dimethylamino-4’-N’-methylstilbazolium tosylate) to the bath for cathodic electrodeposition of CuSCN, namely, methanolic solution of 2.5 mM Cu(ClO4)2, 2.5 mM LiSCN and 0.1 M LiClO4. Cathodic electrolysis at 0.2 V (Ag/AgCl) at an FTO coated glass RDE (500 rpm) for 10 min at room temperature lead to a deposition of homogeneous red-colored CuSCN-DAST hybrid thin films. Increase of DAST concentration in the bath up to 250 μM resulted in a systematic increase of DAST concentration in the film, increase of the film thickness for about 30%, as well as significant change of the film morphology, despite of the unchanged current during the electrodeposition. The absorption peak of the hybrid film is clearly red-shifted compared to that of the DAST solution, indicating certain ordering of the stilbazolium. Detailed characterization for the crystalline structure, composition, as well as applications for SHG and solar cells are under way. [1] E. Cariati, et al., Adv. Mater., 13, 1665-1668 (2001).

Authors : S. Ullah, M. Mollar, B. Marí
Affiliations : Institut de Disseny i Fabricació, Universitat Politècnica de València, Camí de Vera s/n, 46022 València, SPAIN

Resume : Cd1-xZnxS films suitable for solar cell photovoltaic devices have been produced by chemical bath deposition (CBD) on to indium thin oxide (ITO) coated glass substrates using an aqueous solutions for solar cell photovoltaic application. Cadmium sulfide, zinc sulfide and thiourea were used as sources of Cd+2, Zn+2, and of S-2, respectively. Triethenolamine was used as complexing agent to control the Cd+2 and Zn+2 ions concentrations and ammonia to adjust the pH 10±5 of the solution. The temperature of the bath was kept at 70 °C. The as deposited films are well adherent, homogeneous and free from pinholes. The incorporation of Zn in CdS was found to be dependent on the annealing temperature and The structure of the films as observed by X-ray diffraction was polycrystalline with hexagonal structure and (100), (101), (102) and (110) as main peaks. Energy dispersive spectroscopy (EDS) shows non-stoichiometric films due to a deficit of sulfur by increasing Zn content. The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as the Zn content increases. The values of the absorption edge are found to shift towards the shorter wavelengths with Zn content and hence the direct bandgap energy varies from (Eg ~ 2.42 eV) for the CdS film and (Eg ~ 3.30 eV) for the ZnS film. Cd1-xZnxS thin films can be useful as buffer and window layers in Cu(In,Ga)Se2 and Cadmium telluride (CdTe) thin films solar cells due to ability to tune the band gap through the Zn/Cd ratio present in the chemical bath.

Authors : S. Mashhoun, M. Dehghani, A. Behjat, F. Tajabadi, N. Taghavinia
Affiliations : Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran, 145888969, Iran; Department of Physics, Sharif University of Technology, Tehran, 11155-9161, Iran; Department of Physics, Yazd University, Yazd, 5116787317, Iran; Nanotechnology and Advanced Materials Department, Materials and Energy Research Center, Karaj, 3177983634, Iran; Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran, 145888969, Iran & Department of Physics, Sharif University of Technology, Tehran, 11155-9161, Iran

Resume : This study investigates all-solution-processed CuInS2 (CIS) solar cells with the superstrate architecture: FTO/TiO2/In2S3/CuInS2/Carbon. The hole-blocking TiO2 and buffer In2S3 layers are fabricated by spray pyrolysis prior to the spin-coating of the CIS precursor ink. A conductive carbon paste is deposited by doctor blade method afterward. The impact of Indium Sulfide layer deposition conditions on cell performance is studied. The In2S3 layer is made by spray pyrolysis using an aqueous solution of indium chloride tetrahydrate and thiourea with the molar ratio of [1]:[6]. Spray rates of 2ml/min and 4ml/min and the substrate temperature of 250°C, 350°C and 450°C are examined. XRD measurement shows improvement in crystallinity – in the desired beta phase – for deposition temperate of 350°C compared to that of 250°C. The best cell performance is gained with the buffer layer sprayed at 350°C with the rate of 4ml/min with the efficiency of 4.1%. With the substrate temperature of 450°C, cell efficiency is not improved due to the phase transition of In2S3 at 420°C and potential diffusion of Copper atoms in the interface between In2S3 buffer and the CIS absorber layer. To avoid the diffusion, the spray pyrolysed In2S3 layer is subjected to chemical treatment with Na2S bath. The chemical treatment improves the solar cell efficiency from 0.36% and 0.6% to 0.72% and 1% for the deposition rate of 2 and 4 ml/min respectively.

Authors : Abdalaziz Aljaboura,b,c,Dogukan Hazar Apaydinc, Halime Coskunc, Faruk Ozeld, Mustafa Ersozb, Philipp Stadlerc, Niyazi Serdar Sariciftcic and Mahmut Kus*a,b
Affiliations : a-Selcuk University, Department of Chemical Engineering, 42075, Konya, Turkey b-Selcuk University, Advanced Technology Research and Application Center 42075, Konya, Turkey c-Linz Institute for Organic Solar Cells (LIOS)/Physical Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz, Austria d-KaramanogluMehmetbey University, Department of Metallurgical and Materials Engineering, Faculty of Engineering, 70100, Karaman, Turkey

Resume : Herein we report the application of chalcopyrite, p-type semiconductor CuInS2 (CIS) in nanofibrous structure for the reduction of CO2 to CO with faradaic efficiency of 70-80%. Initially the synthesis of CuInS2nanofibers was carried by adaptable electrospinning technique. In order to reduce the imperfection in the crystalline fiber polyacrylonitrile (PAN) was selected as template polymer [1]. Afterwards the desired chemical structure of nanofibers was achieved through sulfurization process. Making continuous CuInS2nanofibers on the cathode surface by electrospinning method brings the advantages of being economical, environmentally safe and versatile. The obtained nanofibers have well uniform size and diameter according to the Scanning Electron Microscope (SEM). An improvement of faradaic efficiency was achieved with the catalytic active CuInS2 in nanofibrous structure as compared to the solution processed CuInS2. The CuInS2nanofiber electrodes prepared by the electrospinning technique, show four times higher faradaic efficiency as compared to the solution prepared films. Electrode nanostructure and less contamination as compared to solution processed films and having a better defined chemical composition play a role in this improvement. Fabrication and application of nanofibrous materials through electrospinning technique might be of interest for other electrocatalytic systems for CO2 reduction as well [2]. [1] Ozel F.; Kus, M.; Yar, A.; Arkan, E.; Yigit, M. Z; Aljabour, A.; Büyükcelebi, S.; Tozlu, C.; Ersoz, Materials Letters. 2015, 140, 23–26 [2]Ozel F.; Journal of alloys and compounds. 2016, 657, 157-162

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Quantum Dot and Nanoparticle PV : Saif Haque
Authors : Takaya Kubo1), Haibin Wang1), J. Nakazaki1), Hiroshi Segawa1,2)
Affiliations : 1) Research Center for Advanced Science and Technology, The University of Tokyo 2) Department of General System Studies, Graduate School of Arts and Sciences, The University of Tokyo

Resume : Development of high efficiency solar cells using a cost effective way is of great importance to achieve low generation cost and expansion of application areas. In this respect, colloidal quantum dots (CQDs) are promising absorbers and carrier transporter for the solar cells. This is because of high degree of freedom for controlling absorption band positions so as to cover a wide range of solar spectrum, and because CQDs are compatible with solution-based technology. Recently, depleted heterojunction solar cells made up of ZnO electron transporter and CQD have been steadily increasing its performance. However, short carrier diffusion length of CQD films limits the film thickness, namely, light harvesting efficiency in the near IR region. To avoid this problem, we then have focused on solar cells composed of PbS CQD/ZnO nanowire structures (NW-type), aiming at efficient carrier transport and light absorption in the near infrared region. We developed air-stable and high efficiency solar cells yielding a power conversion efficiency of 7% and a maximum EQE of 60% in the near-IR region (at 1020 nm) and over 80% in the visible region [1-3], and reported that NW-type solar cells gave a carrier diffusion length of over 1000 nm [4]. Although the implementation of spatially separated carrier pathways was verified effective for fabricating high efficiency CQD-based solar cells, there are much room to increase solar cell performance such as Voc and FF. In this presentation, we discuss the strategy for further increase in the performance by focusing on surface engineering of PbS CQDs and ZnO NWs. 1) J. Phys. Chem. Lett., 4, 2455 (2013); 2) Phys. Stat. Solidi (rrl), 8, 961 (2014); 3) ACS Nano, 9, 4172(2015); and 4) J. Phys. Chem. C, 119, 27265 (2015).

Authors : Ebuka S. Arinze, Botong Qiu, Gabrielle Nyirjesy, Susanna M. Thon
Affiliations : Johns Hopkins University

Resume : Plasmonic enhancements for solution-processed organic, inorganic, and hybrid photovoltaic technologies have been explored as a light trapping technique to help improve absorption in the transport-limited films. Despite optimistic predictions, experimental performance enhancements based on surface plasmonics have been limited. Here, we overview an effective medium model designed to predict realistically achievable photocurrent enhancements based on embedded plasmonic nanoparticles in solution-processed thin film solar cells. This model is used to critically evaluate the prospects for realizing plasmonic enhancements in practical devices including perovskite, organic, and colloidal quantum dot solar cells. Parameters such as nanoparticle size, shape, material type, and concentration are considered, and strategies for achieving a balance between optical field enhancement in the photovoltaic film verses parasitic absorption in the metal nanoparticles are quantified. We find that further plasmonic gains may be possible in organic photovoltaic cells and discuss specific experimental implementations.

Authors : Sjoerd Hoogland Edward H. Sargent
Affiliations : Department of Electrical and Computer Engineering University of Toronto, 10 King’s College Road, Toronto, ON, M4S 3G4, Canada

Resume : Currently used solar materials are limited to harvest light from the visible and near-infrared portions of the solar spectrum. A full 30% of solar power is in the infrared spectral region and is thus effectively wasted by conventional solar cell technologies. Colloidal quantum dots are an innovative class of low-cost liquid-based materials for converting light into electricity. What makes them so appealing is that their optical properties are strongly dependent on their physical size: different-sized quantum dots will operate upon different parts of the solar spectrum with a range that extends from the visible all the way into the infrared. This unique feature can be applied to improve the solar power conversion efficiencies of mainstream commercial technologies such as silicon by integrating the infrared colloidal quantum dot solar cells in a hybrid configuration with the conventional solar technology. Alternatively, true tandem operation can also be realized for example with perovskite solar cells. We will present the recent results in the development of colloidal quantum dot solar cells which can harvest infrared solar radiation in an efficient and cost-effective way.

Advanced Characterization and Materials For Solar Energy : Kubo Takaya
Authors : Gunther Wittstock
Affiliations : Carl von Ossietzky University of Oldenburg, Faculty of Mathematics and Science, Institute of Chemistry, D-26111 Oldenburg, Germany

Resume : In the feedback mode of SECM an added redox mediator is converted under diffusion controlled conditions at a microelectrode (ME) probe. For the analysis of a DSC the reduced form of the redox electrolyte is formed in this process. If the ME is brought to a distance of a few ME radii to an illuminated DSC anode, the dye regeneration process at the photoanode also regenerates the original for of the mediator. This additional source of mediator is sensitively detected as a current increase at the ME. Two experimental approaches have been used for the analysis of photoanodes of dye sensitized solar cells (DSC) by scanning electrochemical microscopy (SECM). The first is the recording of an approach curve during which the flux of redox mediator reaching the sample is systematically varied. The current can be compared to numerical simulation, from which an effective pseudo-first order rate constant keff is accessible. By measuring such curves under with different light intensity and mediator concentration, the change of keff with experimental parameters can be used to deduce more details of the regeneration process. Recent progress in correlating these values to the performance of entire DSCs is reviewed. Another approach aims for resolving lateral heterogeneities of DSC performance. Despite the fact that SECM MEs are larger than the used nanaostructure and the strong light scattering in photoanodes, steady progress in this direction will be reviewed.

Authors : Shaimaa A. Mohamed (a, b), Markus C. Scharber (a), Misha Sytnyk (c), Wolfgang Heiss (c), Florian Hackl (d), Thomas Fromherz (d), Salah S. A. Obayya(b), Niyazi S. Sariciftci(a), Daniel A.M. Egbe (a), Philipp Stadler (a),
Affiliations : a) Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, A-4040 Linz, Austria b) Center for Photonic and Smart Materials (CPSM), Zewail City of Science and Technology, Sheikh Zayed District, 6th of October City, 12588, Giza, Egypt. c) iMeet, Friedrich-Alexander University Erlangen-Nuremberg. d) Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstr. 69, A-4040 Linz, Austria

Resume : Lead-chalcogenide colloidal quantum dots represent a promising absorber class for photovoltaic cells. The ease of processing from solution and the optoelectronic properties result in an emerging technology. However, fabricating efficient photovoltaic devices using quantum dot materials has often been limited by non-radiative recombination. In this work the shows a pathway to suppress non-radiative losses resulting in an effective improvement of the open circuit voltage. This is performed by shifting the excitonic peak towards the infrared and by using an amine-based route to protect the surface from building defect state while processing. Thus our results show the pathway to a scenario with less non-radiative losses in a quantum dot solar cells .

Authors : Seçkin AKIN* and Savaş SÖNMEZOĞLU
Affiliations : Department of Metallurgical and Materials Engineering, Karamanoğlu Mehmetbey University, Karaman, Turkey

Resume : This work is focused on the synthesis of novel Cu(In1–xGax)(Se1–yTey)2 (CIGST) nanostructures via hydrazine–free solution method and utilization as absorbing layer for the thin film solar cells. A preferential orientation along the [112] direction without secondary phases, an enhanced crystal quality, a better electrical conductivity, and a morphological transformation from nanoparticles to nanosheets were determined with increasing (Se+Te)/Se ratio by XRD, Raman, Van der Pauw, SEM/EDX, and AFM results. Furthermore, the UV–Vis–NIR spectra indicated that band gap of chalcopyrite compounds can be tuned by changing the (In+Ga)/In and (Se+Te)/Se ratio in the range of 1.15–1.57 eV and 1.32–1.73 eV, respectively. By optimizing the device architecture, a high power conversion efficiency (PCE) of 11.37% with Voc of 0.67 V, Jsc of 26.78 mAcm–2, and FF of 63.36% has been achieved for Cu(In0.50Ga0.50)(Se0.50Te0.50)2 based cell. This efficiency is the best record among the chalcopyrite based thin film solar cells in which each layers are performed by solution processable method. Besides, all the solar cells exhibited a quantum efficiency over 75% in the visible region. Consequently, low–cost Te has a favourable contribution on the photovoltaic performance of the solar cells due to the its high photoconductivity, and recombination reduction potential seen at grain boundaries around the Mo back contact. Our results not only demonstrate a method of producing all layers of thin film solar cells in a hydrazine–free solution processable route, but also provide important scientific insights that will facilitate further improvement of the low cost chalcopyrite based solar cells. Keywords: Cu(In1–xGax)(Se1–yTey)2 (CIGST), Thin Film Solar Cells, Sol–Gel Method. Acknowledgment Authors would like to thank the European Cooperation in Science and Technology through COST Action MP1302 Nanospectroscopy and the Scientific and Technological Research Council of Turkey (TUBITAK Grant number 112T981) for the financial support of this research.

Authors : Astrid-Caroline Knall,1,2 Christian B. Nielsen,2 Mindaugas Kirkus,3 Thomas Rath,1 Gregor Trimmel,1 and Iain McCulloch2,3
Affiliations : (1) Institute for Chemistry and Technology of Materials (ICTM), NAWI Graz, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria; (2) Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK; (3) Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), SPERC, Thuwal 23955-6900, Saudi Arabia

Resume : Electron-deficient tetrazine-based building blocks have been already successfully applied as strong acceptors in donor-acceptor copolymers.[1] One limiting factor, however, is their poor solubility, which requires to combine them with electron-rich comonomers with large solubilising alkyl chains. As benzothiadiazole (BTD), one of the most successful electron-deficient units to date also lacks in solubility, 2,1,3-benzothiadiazole-5,6-dicarboxylic imide has been developed to improve solubility and processability. Copolymers with this acceptor unit led to excellent efficiencies of over 8% without requiring processing additives or additional processing steps such as thermal annealing.[2] This highly soluble building block also allows variation of the alkyl chains on both electron-rich and electron-deficient components to tailor the alkyl chain substitution pattern, which has a profound influence on blend morphology and consequently device performance.[3] In this contribution, we will discuss the preparation of novel acceptor monomers (6-alkylpyrrolo[3,4-d]pyridazine-5,7-diones, PPD) via inverse-electron-demand Diels-Alder reactions of tetrazines and N-alkyl substituted maleimides.[4] By this synthetic approach, alkyl chains and flanking aromatic units can be easily varied to study structure-property relationships. The PPD monomers are obtained in good yield and purity. Furthermore, conjugated polymers were derived from Pd-catalyzed Stille-type polymerizations with (4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane) (BDT) and (4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane) (oBDT). The obtained copolymers (BDT-PPD and oBDT-PPD) show good solubility and film forming properties. Besides testing their performance in combination with PCBM in organic solar cells, we also focused on evaluating their properties in polymer/nanocrystal hybrid solar cells. Therefore, inorganic nanocrystals (e.g. copper indium sulfide) have been synthesized in situ in films of these novel polymers using metal xanthates to obtain hybrid bulk heterojunction absorber layers. [1] Z. Li et al., J. Am. Chem. Soc., 2010, 132, 13160-13161. [2] C. B. Nielsen et al., Adv. Mater., 2015, 27, 948-953. [3] I. McCulloch et al., Acc. Chem. Res., 2012, 45, 714-722. [4] Q. Ye et al., Org. Lett., 2014, 16, 6386-6389.

Authors : D. Farka , C. Ulbricht, H. Heilbrunner, H. Coskun , C. Cobet , K. Hingerl , L. M. Uiberlacker, S. Hild , T. Greunz , D. Stifter , M. C. Scharber & P. Stadler
Affiliations : Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria ;Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria ;Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria ;Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria ;Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria; Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria; Institute of Polymer Science, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria; Institute of Polymer Science, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria; Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria;Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria; Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria ;Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria; Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria ;Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, 4040 Linz, Austria

Resume : A stringent limitation in many optical devices, such as solar cells and light emitting diodes, is the intrinsic need for a transparent electrode. Uniting relevant aspects, indium tin oxide (ITO) is often the material of choice with present alternatives being in particular found in conductive polymers. In this work, we present the use of PEDOT:sulphate films prepared by chemical vapour deposition (CVD) as a transparent electrode in optical devices. The application of PEDOT:sulphate is especially advantageous as it is directly coated on top of the substrate, intrinsically doped and combines characteristics such as high conductivity (4000 S/cm), high degree of order, and high purity. Additionally, PEDOT:sulphate is in its application water-free which makes it a promising candidate for devices with moisture-sensitive components such as perovskites. Preliminary results of PEDOT:sulphate electrodes integrated in optical devices such as bulk heterojunction solar cells (glass/Cr/Au/PEDOT:sulphate/P3HT:PCBM/LiF/Al) and organic light emitting diodes (glass/Cr/Au/PEDOT:sulphate/MH-PPV/LiF/Al) will be shown.


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Symposium organizers
Gregor TRIMMELInstitute for Chemistry and Technology of Organic Materials, Graz University of Technology

Stremayrgasse 9 8010 Graz, Austria
Matthew WHITEDepartment of Physics, University of Vermont

Cook Building 82 University Pl, Burlington, VT 05405-0125, USA
Philipp STADLERLinz Institute for Organic Solar Cells (LIOS), Institute for Physical Chemistry, University of Linz

Altenbergerstr 69 4040 Linz, Austria
Tsukasa YOSHIDAResearch Center for Organic Electronics (ROEL)

4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan