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Functional materials


Materials, components and characterization of energy harvesters for self-powered electronics

Energy harvesting, the collection of small amounts of energy from the environment to power devices, can help solve the global energy challenge without depleting natural resources. Piezoelectric, multiferroic, photovoltaic, thermoelectric and electromagnetic are some examples of materials that transduce energy from one to another. The implementation of these materials has notably prompted a shift in the design approach of electronic systems towards the goals of miniaturization, multi-functionality, high levels of integration, light weight and self-powered.

This symposium will address current challenges and strategies in materials synthesis and micro-/nanofabrication technology, device integration and advanced characterization with special emphasis on energy generation for self-powered electronics.

Hot topics to be covered by the symposium:

  • Synthesis and fabrication of nanomaterials and nanostructures (including ALD/CVD, solution processing, sputtering, plasma)
  • Fundamental physics of energy conversion/harvesting systems based on mechanical energy, thermal energy, chemical energy, solar energy
  • Atomic scale (structure, chemical, electrical, optical) characterization
  • Multisource energy harvesting
  • Flexible, portable, wearable devices
  • Energy-efficient emerging memory technology
  • Power challenges in emerging devices
  • Applications in IoT, AI

Confirmed invited speakers:

  • Yang Bai, University of Oulu, Finland “Band gap engineering of piezoelectrics for multi-energy harvesting - Tricks, lessons, and opportunities
  • Mari Napari, University of Southampton, UK “Atomic layer deposition for emerging energy scavenging  technologies in low-power electronics
  • Marina Freitag, Newcastle University, UK, “Zombie Solar Cells for Ambient Applications"
  • Naoufal Bahlawane, LIST, Luxembourg “Hybrid ALD-CVD processing of tailored nanocomposite coatings for energy applications
  • Inkyu Park, KAIST, Korea “Micro/nano-engineered, self-powered physical/chemical sensors for smart IoT
  • Sohini Kar-Narayan, University of Cambridge, UK,"Materials-related Strategies for Highly Efficient Triboelectric Energy Generators"


Selected papers will be published in a special issue of Applied Research (Wiley).

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09:05 Welcome    
Multienergy Harvesting : Ana Borrás
Authors : Yang Bai
Affiliations : Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, FI-90570 Oulu, Finland

Resume : High-performance piezoelectric materials are used for kinetic energy harvesting and piezoelectric energy harvesters made from these materials are considered the most efficient among counterparts. High-performance piezoelectrics are usually oxide perovskite ferroelectrics which also exhibit photovoltaic effect. This fact offers a unique opportunity to integrate light harvesters with the piezoelectric ones in a single material to achieve multi-source energy harvesting. Coupling multiple energy in one material promotes self-sufficiency and sustainability of energy harvesters and associated electronic systems. Strong piezoelectricity has been thought to inevitably lead to wide photonic band gaps, and vice versa, narrow band gaps eliminate piezoelectricity. This view, however, is being changed. In order to efficiently absorb visible lights, e.g., solar and indoor lights, the band gap needs to be reduced whilst retaining the piezoelectricity. This talk will walk through the achievements in recent years in terms of band gap engineering of piezoelectric materials with an emphasis on works carried out by the speaker’s research group. It has not been an easy task so this talk will highlight lessons learnt through recent experimental studies. It will also tell the tricks of obtaining truly reduced band gaps instead of misleading observations or unfavoured in-gap states. The speaker aims to motivate peer researchers working in similar fields to explore this emerging research topic by giving insights of future opportunities for both fundamental investigations and applications.

Authors : J. Groten, O. Werzer, K. Krawczyk, P. Schäffner, A. Alvarez, G. Domann, X. Wang, C. Rusu, M. Shousha, T. Herndl, M. Moser, B. Stadlober
Affiliations : J. Groten; O. Werzer; K. Krawczyk; P. Schäffner; A. Alvarez; B. Stadlober: JOANNEUM RESEARCH Forschungsgesellschaft mbH, Weiz, Austria, G. Domann: Fraunhofer-Institut für Silicatforschung ISC, Würzburg, Germany, X. Wang; C. Rusu: RISE Research Institutes of Sweden, Göteborg, Sweden, M. Shousha: Wuerth Elektronik eiSos GmbH & Co. KG, Garching, Germany, T. Herndl: Infineon Technologies Austria AG, Graz, Austria, M. Moser: Eologix Sensor Technology GmbH, Graz, Austria

Resume : The current digital transformation creates a huge demand on smart, interconnected objects. To monitor the object’s inner state or environment, smart sensor systems are required that can form an integral part of the object while being energy self-sustained. A strong focus is hereby on enabling technology that relies on non-toxic, recyclable materials and low-cost, sustainable fabrication methods. Within the H2020 EU-project SYMPHONY [1] we aim at developing an innovative energy autonomous sensor system. The energy harvesting is completely realized by printed, recyclable and non-toxic materials including the ferroelectric polymer P(VDF-TrFE), printable silicon-based rectifiers, redox polymer batteries and cellulose based supercaps. Multiple energy sources such as mechanical deformation, vibration and magnetic stray fields are harvested with piezoelectric, triboelectric and magnetoelectric transducers. Main application fields are condition monitoring of renewable energy infrastructure, urban mobility and smart living. We will present novel material developments as well as innovative integration concepts. These include stretchable piezoelectric materials and conductors, printed magnetic nanocomposites as well as power management and rectifier materials. Cost effective and scalable methods to print these materials on flexible films and to combine them with energy efficient electronics and sensor technologies are introduced. [1]

Affiliations : School of Engineering and Material Science and Materials Research Institute, Queen Mary University of London

Resume : With the consumption of fossil fuels and the increasing awareness of environmental protection, more and more efforts are being put into the development of renewable and clean energy. Mechanical energy is the one of the most abundant and accessible energy sources, and has been widely harvested by large-scale technologies such as wind power or tidal stream generators. Piezoelectric nanogenerators (PENGs) provide a potential way to convert small mechanical energy such as body motion or vibration into electricity, which can be used to power small portable electronics, medical bio implants, remote wireless sensors etc. Also, solar energy offers the potential to provide much higher power levels than motion since the sun delivers more energy to the earth in 1 h than the entire planet consumes in one year. However, light is not always available, nor is movement, therefore a hybrid energy harvester that can make use of both sources provide a more reliable and high-level of power for small, portable or self-powered devices. Here, a simple solar and piezoelectric hybrid energy harvester (HEH) combining PENGs and perovskite solar cell with the structure of PET/ITO/ZnO seed layer/ZnO nanorods/perovskite/hole transport layer/Au was designed, fabricated and tested. Oscillation (NG) and illumination (PV effect) testing indicated that HEHs operated as kinetic and solar energy harvesters both separately and simultaneously. The length and diameter of ZnO nanorods were optimised to achieve the enhancement of both PV and NG output performance. The coupling effect between perovskite and piezoelectric ZnO nanorods, as known as the piezo-phototronic effect, was also found and investigated.

Authors : Xabier García-Casas 1, Ali Ghaffarinehad 1, Francisco J. Aparicio 1,2, Javier Castillo-Seoane 1, Carmen López-Santos 1,2, Jorge Budagosky-Marcilla 1, Jorge Gil-Rostra 1, Juan Ramón Sánchez-Valencia 1, Ángel Barranco 1, Ana Borrás 1
Affiliations : 1. Nanotechnology on Surfaces and Plasma, Instituto de Ciencia de Materiales de Sevilla (Consejo Superior de Investigaciones Científicas – Universidad de Sevilla), Sevilla, Spain 2. Departamento de Física Aplicada I, Universidad de Sevilla, Sevilla, Spain

Resume : Microelectronics and wireless technologies have spread all over the globe in recent decades. The new paradigm of smart cities and wireless sensor networks is becoming a reality, but the unstoppable demand for wearables, smart electronics, and tiny connected sensors bring us some issues on how to deal with the energy management of billions of wireless and portable devices. Providing a little battery to every single portable piece of electronics and charging it once and again from the electricity produced hundreds of kilometers far away is completely unsustainable in terms of maintenance, energy losses, waste or pollution, and due to the lack of resources. Energy harvesters and nanogenerators propose a solution by generating the necessary electric power from the local environment and the residual distributed energies. The eventual realization of self-powered microsystems and on-site energy harvesting yet requires the development of multisource and multifunctional energy scavengers and scalable, high yield, and low costs fabrication processes. Physical vapor deposition, plasma enhanced chemical vapor deposition, and plasma polymer functionalization have been already scaled and optimized in areas such as microelectronics, optics, and solar cells where they are present at several levels of the fabrication and materials and device processing. Herein we share a multi-step process combining these techniques for the fabrication of 1D core@shell functional nanostructured surfaces for its application on hybrid piezo and triboelectric nanogenerators [1]. The methodology is based on the application of small-molecule organic nanowires as supported 1D scaffolds [2]. These ONWs serve as well as flexible support for the deposition of a core@multishell system including a thin metallic shell working as an inner electrical contact and a highly texturized ZnO piezoelectric shell. The fabrication method is compatible with the use of polymeric supports as PET and the growth in high density of the core@multishell nanowires with under design length and thickness[3]. Finally, the NWs are embedded in PDMS to build a top-bottom triboelectric architecture. Factors like crystalline texture, ZnO thickness, nanowires aspect ratio, and surface chemical modification of the PDMS are explored to optimize the power output of the nanogenerators aimed for harvesting from low-frequency vibrations. Just by manual triggering, the hybrid device can charge a capacitor to switch on an array of color LEDs. Outstandingly, this simple three-layer architecture allows for harvesting vibration energy in a wide bandwidth, thus, we show the performance characteristics for frequencies between 1 Hz and 50 Hz and demonstrate the successful activation of the system up to ca. 800 Hz. 1. Garcia-Casas, X., Borras, A. et al. (2022) Nano Energy 91: 106673 2. Macias-Montero, M., Borras, A. et al. (2013) Adv. Func. Mater. 23:5981-5989. 3. Filippin, A. N., Borras, A. et al. (2019) Nano Energy 58:476-483.

10:30 Coffee break    
Triboelectric Generators : Ana Borras
Authors : Dipankar Mandal
Affiliations : Quantum Materials and Devices Unit, Institute of Nano Science and Technology, Knowledge City, Sector 81, Mohali, 140306, India

Resume : With rising population of the world, demand of energy and portable electronics is on its full swing. Self-powered devices and sensors are like the panacea to full fill this gap. Triboelectric nanogenerator (TENG) is a promisingly desired technology to fabricate a self-powered devices and sensors, due to its low cost, wide choice of materials and easy fabrication techniques.1-3 The working principle of the TENG is primarily based on the coupled effect of contact electrification and electrostatic induction. Surface area, roughness and charge density of the contacting surfaces plays a key role to determine the overall performance of TENG. Conventionally, to fabricate a TENG, two materials with two different triboelectric nature is preferred. However, choice of a combination of different materials based on their charge density is one of the prime challenging tasks. Here, we have proposed, an effective way to fabricate a TENG with a single active material only (abbreviated as S-TENG). For instances, S-TENG comprises of electrospun nylon nanofibers, surface potential of the nanofibers are tuned by changing the voltage polarity in the electrospinning setup. The difference in surface potential leads to generate different charge density, gives rise to change in work function, a key factor to design S-TENG. Further, S-TENG is demonstrated as an ultrahigh sensitive wearable acoustic sensor with mechanoacoustic sensitivity of ≈27 500 mV Pa–1. Owing to its high sensitivity in the low-to-middle decibel (60–70 dB) sounds, S-TENG is plausibly capable in recognizing different voice signals depending on the condition of the vocal cord. Effective voice recognition ability of S-TENG indicates that it has high potential to open an alternative pathway for medical professionals to detect several diseases such as neurological voice disorder, muscle tension dysphonia, vocal cord paralysis, and speech delay/disorder related to laryngeal complications. References: 1. Babu, A; Malik, P; Das, N; Mandal, D. Surface Potential Tuned Single Active Material Comprised Triboelectric Nanogenerator for High Performance Voice Recognition Sensor. Small. 2022, 2201331. 2. Wu, C.; Wang, A. C.; Ding, W.; Guo, H.; Wang, Z. L. Triboelectric Nanogenerator: A Foundation of the Energy for the New Era. Adv. Energy Mater. 2019, 9, 1–25. 3. Guo, H.; Pu, X.; Chen, J.; Meng, Y.; Yeh, M. H.; Liu, G.; Tang, Q.; Chen, B.; Liu, D.; Qi, S.; Wu, C.; Hu, C.; Wang, J.; Wang, Z. L. A Highly Sensitive, Self-Powered Triboelectric Auditory Sensor for Social Robotics and Hearing AIDS. Sci. Robot. 2018, 3, 1–10.

Authors : Suman Nandy1*, Sumita Goswami2, Guilherme Ferreira1, Elvira Fortunato1, Rodrigo Martins1
Affiliations : 1. CENIMAT/i3N, Department of Materials Science, NOVA School of Science and Technology, NOVA University Lisbon (FCT-NOVA) and CEMOP/UNINOVA, Campus de Caparica, 2829-516 Caparica, Portugal 2. Almascience, Campus da Caparica, 2829-516 Caparica, Almada, Portugal Email:

Resume : In this digital era, from lifestyle to sports and health to security, wearable technology is an inevitable trend, which has the capability of transforming businesses into smarter, informative, and more communicative through an impact on human-machine interaction. For an example, a simple heating cloth of 10W power requires 1 Kg of Li-ion battery to run 10h. Powered prostheses for walking consume up to 20 W with a 0.49 kg-battery, that needs charging every 3 h. Such high demand of power may not be fulfilled by batteries alone which has a limitation of flexibility, recharging or replacement. Therefore, the biggest challenge in the smart technology is sustainable power source, that can back up the electronics unconditionally. This situation considers a new platform of self-powered technology, operating without any external power sources! In this context, the principal vision of us is to speed up the concept of self-powered technology based on different wearable and low-cost platform, by constructing in such a way, that will buckle paper/textiles and electronic platform to bring a new smart technology which will have inbuilt self-powered system. The core idea is mechano-stimuli power harvesting mechanism, when two different layers comes together and make a contact with stress (either rubbed/sliding or pressing), resulting a current generation due to charge transfer mechanism. Given that, conjugated polymer (CP) is a new low-cost option. Energy harvesting abilities of CPs are based on the energy-transfer process through the π─π* interaction in its backbone, that can easily be modulated through a simple doping-dedoping process. Proof of concept of our manufactured devices based on paper and textile platforms has been used for security system and gesture monitoring applications. References: 1. Nandy, S.; Goswami, S.; Marques, A.; Gaspar, D.; Grey, P.; Cunha, I.; Nunes, D.; Pimentel, A.; Igreja, R.; Barquinha, P.; et al. Cellulose: A Contribution for the Zero e‐Waste Challenge. Adv. Mater. Technol. 2021, 6, 2000994. 2. Nandy, S; Fortunato, E; Martins, R., Green economy and waste management: An inevitable plan for materials science. Prog. Nat. Sci. 2022. 3. Ferreira, G.; Opiniao, A.; Das, S.; Goswami, S.; Pereira, L.; Nandy, S.; Martins, R.; Fortunato, E. Smart IoT Enabled Interactive Self-Powered Security Tag Designed with Functionalized Paper. Nano Energy 2022. 4. Ferreira, Guilherme; Goswami, Sumita; Nandy, Suman; Pereira, Luis; Martins, Rodrigo; Fortunato, Elvira. "Touch-Interactive Flexible Sustainable Energy Harvester and Self-Powered Smart Card". Advanced Functional Materials 30 5 (2019): 1908994. 5. Goswami, Sumita; Santos, Andreia dos; Nandy, Suman; Igreja, Rui; Barquinha, Pedro; Martins, Rodrigo; Fortunato, Elvira. "Human-motion interactive energy harvester based on polyaniline functionalized textile fibers following metal/polymer mechano-responsive charge transfer mechanism". Nano Energy 60 (2019): 794-801. 6.Goswami, Sumita; Nandy, Suman; Banerjee, Arghya Narayan; Kiazadeh, Asal; Dillip, Gowra Raghupathy; Pinto, Joana V.; Joo, Sang Woo; Martins, Rodrigo; Fortunato, Elvira. "“Electro-Typing” on a Carbon-Nanoparticles-Filled Polymeric Film using Conducting Atomic Force Microscopy". Advanced Materials 29 47 (2017): 1703079.

Authors : M. Neuber, A. Viegas*, M. Lederer, K. Kühnel, M. Czernohorsky
Affiliations : Fraunhofer IPMS, Center Nanoelectronic Technologies, An der Bartlake 5, 01109 Dresden, Germany e-mail:

Resume : The unexpected discovery of ferroelectricity and in turn pyroelectricity in hafnium oxide (HfO2), lead to a plethora of new applications in the field of sensors, energy harvesters, thermal imaging and so on. In comparison to the commonly used pyroelectric materials like lithium tantalite (LiTaO3) and lead zirconate titanate (PZT), doped HfO2 is CMOS compatible with a pyroelectric coefficient that can be enhanced through 3D structures. Recent studies show that Al doped HfO2 (HAO) with 1.0 to 1.4 % aluminum can achieve a pyroelectric coefficient of up to 71 µCm-2K-1 [2]. An even higher pyro-coefficient of 79 µCm-2K-1 was reported for hafnium zirconium oxide (HZO) with 75 % Zr [1]. In this study, 10 nm HfO2 thin films were deposited through atomic layer deposition (ALD) using Hafnium(IV)-chloride and water. These films were doped by adding ALD cycles of ZrO2 and Al2O3 to HfO2 in a controlled manner to generate our novel co-doped films (HZAO). Zirconium doped hafnium oxide (HZO) with a ratio of 1:1 was used as the base material and zirconium was gradually replaced by aluminum in small increments. The resulting thin films were measured with spectral ellipsometry (SE) and x-ray photoelectron spectroscopy (XPS) before being treated with rapid thermal annealing at 400, 650, 800, 1050 °C. The XRD revealed that the HZAO films mainly consist of orthorhombic/ tetragonal orientated crystals, which are the crystalline phases showing ferroelectricity. HZAO films with higher Al dopant concentration have to be annealed at higher temperatures (> 800°C) to show these crystal phases. For the electrical characterization, the pyroelectric films were implemented into an MIM stack with Ti/Pt as top electrode. The pyroelectric coefficient is measured using the Sharp-Garn method [2]. Prior to the pyroelectric measurement, the films were polarized using an electrical field of 3 MV/cm for 10000 cycles. The influence of doping concentration and thermal treatment of HZAO thin films on the pyroelectric coefficient is discussed in this work. [1] C. Mart, 2021; Pyroelectric and electrocaloric effects in hafnium oxide thin films, doctoral dissertation, [2] L.E. Garn, E.J. Sharp; Use of low‐frequency sinusoidal temperature waves to separate pyroelectric currents from nonpyroelectric currents. Part I. Theory; Journal of Applied Physics 53, 8974 (1982)

Authors : Sontyana Adonijah Graham, Mandar Vasant Paranjape, Anand Kurakula, Jae Su Yu*
Affiliations : Department of Electronics and Information Convergence Engineering. Kyung Hee University. 1732 Deogyeong-daero, Giheung-gu, Yongin-Si, Gyeonggi-do 17104, Republic of Korea

Resume : Energy harvesting technologies are currently being advanced in order to realize and build self-powered battery-free devices. Renewable energy harvesting technologies such as tribo-, piezo-, and pyroelectricity are drawing substantial interest owing to their unique advantages of simple design, readily available materials, low cost, biocompatibility, eco-friendly feature, importantly, high conversion efficiency, and high-power density. As compared to the traditional materials used in energy harvesting, composite semiconductor materials have a great potential application in ferroelectric photovoltaic devices along with pyroelectric and piezoelectric generators. Among various ferroelectric materials, bismuth-based composites have gained more interest due to their tunable properties. For example, bismuth ferrite has a bandgap of 2.2-2.7 eV and large remnant polarization, which is highly advantageous in photovoltaic technologies. Furthermore, owing to its ferroelectric property, it can also be used in piezoelectric energy harvesting. In this presentation, we reported the synthesis of various bismuth composite materials and its material and electrical properties were investigated. Especially, enhancing the efficiency of energy harvesting was systematically studied by optimizing the dopant material in the bismuth ferrite crystal structure. The optimized composite material was further loaded in the ferroelectric polymer to produce a flexible and durable film. Due to the fabrication of a hybrid metamaterial flexible film, it was further used in the fabrication of pyro-, piezo-, and triboelectric nanogenerators for energy harvesting. The fabricated device produces high electrical output and also has a high ability to harvest various energies. The harvested energy was finally used in self-powered electronic gadgets.

Authors : Mandar Vasant Paranjape, Sontyana Adonijah Graham, Anand Kurakula, Jae Su Yu*
Affiliations : Department of Electronics and Information Convergence Engineering, Institute for Wearable Convergence Electronics, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-Si, Gyeonggi-do 17104, Republic of Korea

Resume : Triboelectric nanogenerator is an emerging technology which can be employed to harvest kinetic energy generated from various mechanical motions into electricity. The energy generated while human walking is one of the most commonly available non-utilized mechanical energy around us. In this presentation, we proposed a multistage consecutively-connected hybrid nanogenerator (MCHCF) and it was employed for floor mechanical energy harvesting system. Initially, Sr doped BaTiO3 microparticles were prepared and then, loaded into a PDMS polymer to form a hybrid film with piezo- and triboelectric properties. Furthermore, the Sr-BaTiO3/PDMS film was operated against the aluminum to fabricate a top-contact mode hybrid nanogenerator (HNG) device. The Sr was doped in BaTiO3 to enhance its ferroelectric and dielectric properties to result in producing high electrical output. The Ba0.8Sr0.2TiO3 loading concentration in PDMS was further optimized to get constant and stable electrical output. Eight similar HNG devices were fabricated and assembled within the 3D printed MCHCF system along with a simple electronic circuit. The force applied to a single HNG device within the MCHCF system could produce a highly stable direct-current voltage of 15.5 V. The harvested electricity was further stored and used to power small electronics. This prototype MCHCF system can be implemented in real-time flooring systems with an enlarged surface area to harvest mechanical energy from human walking.

12:30 Lunch    
TEG : Mariona Coll
Authors : Sohini Kar-Narayan
Affiliations : Department of Materials Science & Metallurgy, University of Cambridge, UK

Resume : Triboelectric energy harvesting technologies have received a substantial amount of attention as they constitute one of the most efficient ways of transforming vibrational and frictional energy into electrical energy, regardless of location and environmental conditions. One of the most significant advantages of this technology is in the suitability of a very wide range of materials that can be readily incorporated into devices. In order to achieve efficient energy harvesting performance, advances in materials science and nanotechnology have been applied to develop high-performance triboelectric nanogenerators. In this talk, I will discuss materials-driven progress related to triboelectric energy harvesting, with emphasis on the study of materials-related operating mechanisms and emergent materials design strategies for highly efficient triboelectric devices. In particular, I will focus on the role of polymer crystallinity and surface polarization in determining the triboelectric energy harvesting properties of polymeric nanowires. As an example, the strong hydrogen bonding in α-phase nylon-11 serves to enhance the molecular ordering, resulting in exceptional intensity and thermal stability of surface potential, and consequently enhanced triboelectric performance compared to other polymorphs of nylon-11. In this context, I will also discuss how we developed smart triboelectric yarns comprising a conducting carbon nanotube yarn electrode coated with polymer fibers with optimised triboelectric properties, deposited by a customized electrospinning process for textile-based applications. [1] Y Choi, S-W Kim, S Kar-Narayan, Advanced Energy Materials DOI: 10.1002/aenm.202003802 (2021) [2] T Busolo, PK Szewczyk, M Nair, U Stachewicz, S Kar-Narayan, ACS Applied Materials & Interfaces 13, 16876-16886 (2021)

Authors : C. Rodrigues1, M. Kumar1,2, M. P. Proença1,3, R. Melo4, J. M. Salazar4, A. Pereira1 and J. Ventura1
Affiliations : 1IFIMUP and IN - Institute of Nanoscience and Nanotechnology and Department of Physics and Astronomy, Faculty of Sciences, University of Porto, Porto, Portugal; 2Organisation for Science Innovations and Research, Bah-283104 India; 3Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040 Madrid, Spain; 4Repsol S/A – Technology Lab / Upstream, Madrid, Spain.

Resume : There is an increasingly need to monitor crucial safety and environmental parameters in extraction wells in order to prevent disasters. However, present solutions to feed sensors are inefficient, costly and risky. Furthermore, present energy harvesting technologies do not cope well with the extreme conditions encountered in oil and gas wells that operate at high temperatures, high pressures and involve a highly corrosive environment. The demonstration of new energy harvesting technologies able to operate in these extreme conditions would make a leap forward in their applicability. Triboelectric nanogenerators (TENGs) appearing just in 2012 are the most promising energy harvesting technology able to convert ambient mechanical energy into usefull electrical power [1-3]. Here, we demonstrated a TENG able to generate electrical energy in harsh conditions similar to those found in extraction wells (pressures up to 830 bar and temperatures up to 120 ºC) in direct contact with methane and crude oil [4]. The electrical performance of the assembled device shows a slight increase with increasing pressure from 28 to 119 bar, in methane. However, the electrical outputs decreased strongly with increasing temperature from 25 up to 80 ºC. This clearly demonstrates that temperature is the most critical parameter for TENGs operating in harsh environments. Furthermore, energy harvesting experiments performed in crude oil reveal a decrease of the electric outputs with increasing crude temperature and pressure, but the assembled device continued to generate electrical energy up to pressures of 830 bar and temperatures of 120 ºC. This study clearly demonstrates the suitability of triboelectric devices to harvest energy in harsh environments opening a wide new range of possible applications. References: 1. F-R. Fan et al, Nano Letters,12 (2012). 2. C. Rodrigues et al., Energy and Environmental Science,13 (2020). 3. T. Cheng et al, Advanced Materials Technologies, 4 (2019). 4. C. Rodrigues et al., Nano Energy, 72 (2020)

Authors : Ali Ghaffarinejad,+1 Xabier García-Casas,+1 Fernando Núñez-Gálvez,1,2 Carmen López-Santos,1,2 Juan Ramón Sánchez-Valencia,1 Ángel Barranco,1 Ana Borrás1*
Affiliations : 1) Nanotechnology on Surfaces and Plasma Laboratory, Consejo Superior de Investigaciones Científicas (CSIC), Materials Science Institute of Seville (CSIC-US). c/ Américo Vespucio 49, 41092, Seville (Spain) 2) Departamento de Física Aplicada I, Universidad de Sevilla, C/ Virgen de Africa 7, 41011, Seville (Spain)

Resume : harvesting the energy of rainfall drops as a clean and renewable source of energy is being investigated by researchers where it is a young concept compared to solar and wind powers. triboelectric nanogenerators have been revealed among the most promising technology for this process. However, despite widespread attempts by researchers, the drop energy harvesters' output power is still low, mainly due to the limitations in triboelectric and wetting properties and also the non-optimal and centimeter-scale device architecture that prevents the conversion of the complete kinetic energy of falling drops. In this report, a microscale triboelectric nanogenerator is introduced that can harvest a high density of electrical power from drops through a single, micro-second long-lasting step. The mechanism relays on instantaneous capacitance variation due to the high-speed contact of the drops with the electrodes' active area. The capacitive and micro-scale structure of the device resembles the pixels in a charge-coupled device (CCD), allowing for the production of densely packed arrays. The proposed architecture can be adjusted to different liquids, and scales and is compatible with a variety of triboelectric surfaces, including thin-film approaches

Authors : Sugato Hajra, Hoe Joon Kim
Affiliations : Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu-42988, South Korea

Resume : Energy demand has increased a lot in the recent era due to modernization and the industrial revolution. Smart wearable devices and low-power electronics depend on battery units that own less lifetime and less accessibility. Hence, a sustainable power source is necessary to develop which can act as an alternative to batteries. Nanogenerators having piezoelectric, triboelectric and pyroelectric effects have become popular. Triboelectric nanogenerators (TENG offers many advantages like wide material choice, high power density, simple fabrication process, and several working modes. In this present work, the zeolite imidazole framework (ZIF-8) is synthesized by two approaches: solvent-assisted (SA) and solvent-free (HG), and used for the fabrication of TENG. The structural and morphological analysis elucidates a highly crystalline ZIF-8 is formed. The surface roughness and surface potential were investigated to explore their possibility in addition to conventional triboelectric series. A cost-effective 3D printing of waste printed models was reused to design the TENG. ZIF-8 (HG)/Kapton-based dual-mode TENG device to deliver higher electrical output. The triple-unit TENG was designed and fabricated using an additive manufacturing route which delivered a voltage of 150 V and a current of 4.95 µA. Further, TENG devices were utilized to explore self-powered applications by integration with robotics tilt table as well as biomechanical energy harvesting.

15:30 Coffee Break    
Triboelectric Nanogenerators III : Mariona Coll
Authors : R. D. I. G. Dharmasena
Affiliations : Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, LE11 3NR, United Kingdom

Resume : Introduction Triboelectric Nanogenerators (TENGs), that can convert ambient movements into electricity, are a major candidates in powering next generation portable electronics [1]. TENGs can work as energy harvesters and self-powered sensors, which will massively benefit future internet of things, 5G and advanced wearable developments. Despite reaching high instantaneous power densities (>100W/m2) and efficiencies (>50%), the main drawback of TENGs is their discontinuous and irregular electrical outputs [1]. Typically, a TENG would have a current crest factor of ~7, being 500% higher than a sinusoidal signal. This severely disrupts their ability to continuously power electronic devices [2]. Various power management circuits were developed to counter this, however, such circuits consume significant amounts out of scavenged energy of the TENG, while being unable to eliminate the discontinuity issues [3]. As a solution, several direct current TENGs (DC-TENGs) were reported to generate near-DC output signals, however, these were restricted to sliding mode operation [3]. Therefore, developing DC TENG technologies which can operate on contact-separation mode excitations is a critical need as it would encompass the majority of all TENG types [3]. Methods We introduce a novel contact-separation mode DC-TENG with built-in phase shifting of multiple poles. Multiple TENG units are used which act as different poles of the device, whose spatial position is engineered to systematically control their excitation. When the DC-TENG is subjected to movements (linear or rotary), the poles are excited with engineered time-intervals, creating a phase shift between their output signals. These outputs are rectified and superimposed to develop the sustainable DC-TENG. Results and Discussion The design of this technology was based on the distance-dependent electric field (DDEF) theory [4], which was used to simulate and optimise the structure of the poles and their spatial arrangement. The simulations predicted a current crest factor of ~1.08. A demonstrator DC-TENG device was constructed with 6 poles, each consisting of polyethylene terephthalate and polyethylene triboelectric surfaces, and operating in contact-mode free-standing TENG architectures. The device provided excellent electrical outputs with a current crest factor of 1.1 (~80% reduction in output variations) at relatively low operating frequencies (<8 Hz), one of the best current crest factors reported for TENGs. The applicability of the technology was demonstrated by continuously lighting LEDs and a photodetector. Therefore, this technology addresses one of the key drawbacks of TENGs, accelerating the path towards their commercialisation. References [1] Wu et al., Adv. Energy Mater. 2018, 1802906 [2] Ryu et al., Energy Environ. Sci. 2018, 11(8), 2057-2063 [3] Dharmasena et al., Nano Energy, 2020, 75, 104887 [4] Dharmasena et al., Energy Environ. Sci. 2017, 10(8), 1801-1811

Authors : Elin Dypvik Sødahl, Julian Walker, Kristian Berland
Affiliations : Department of Mechanical Engineering and Technology Management, Norwegian University of Life Sciences, Norway; Department of Materials Science and Engineering NTNU, Norwegian University of Science and Technology; Department of Mechanical Engineering and Technology Management, Norwegian University of Life Sciences, Norway;

Resume : Hybrid molecular crystals have gained attention due to their promising piezoelectric properties. The piezoelectric coefficients of these materials are reported as large as 100 pC/N [1, 2]. In this work, we compute dielectric, piezoelectric and ferroelectric properties of 11 materials using van der Waals density functional theory. These materials are built up of small organic molecular cations and inorganic anions. The best performing materials have organic cations with a cage-like globular geometry. We find the piezoelectric coefficients dij of the hybrid molecular crystals to be comparable to phase-pure inorganic piezoelectrics, such as AlN and LiNbO3. Particularly, the shear piezoelectric responses are large, with a d24 of −94 pC/N calculated for HQReO4*. The same material also shows a large piezoelectric anisotropy with a d16/d33 of 119. Phase pure inorganic perovskites have far smaller anisotropies, such as BaTiO3 with d15/d33 = 6 [1]. The large piezoelectric anisotropy of the molecular piezoelectrics can in part be understood from rotations of the constituent molecules. This effect is similar to the rotation of the polarization vector observed in inorganic perovskites with compositions near a morphotropic phase boundary [1]. The computed electromechanical coupling coefficients vary for the hybrid molecular crystals. However, HdabcoReO4 ** has a coupling coefficient of 0.8, making the material competitive with PZT-5H which has a coupling coefficient of 0.76 [2]. Coupling coefficients this large make hybrid molecular crystals promising for piezoelectric energy harvesting devices. * Quinuclidinium perrhenate ** 1,4–diaz-abicyclo[2.2.2] octane perrhenate [1] J. Harada, Y. Kawamura, Y. Takahashi, Y. Uemura,T. Hasegawa, H. Taniguchi, and K. Maruyama, Plastic/Ferroelectric Crystals with Easily Switchable Polarization: Low-Voltage Operation, Unprecedentedly High Pyroelectric Performance, and Large Piezoelectric Effect in Polycrystalline Forms, J. Am. Chem. Soc. 141, 9349 (2019). [2] J. Harada, N. Yoneyama, S. Yokokura, Y. Takahashi, A. Miura, N. Kitamura, and T. Inabe, Ferroelectricity and Piezoelectricity in Free-Standing Polycrystalline Films of Plastic Crystals, J. Am. Chem. Soc. 140, 346 (2018). [3] M. Davis, M. Budimir, D. Damjanovic, and N. Setter, Rotator and extender ferroelectrics: Importance of the shear coefficient to the piezoelectric properties of domain-engineered crystals and ceramics, Journal of Applied Physics 101, 054112 (2007). [4] B. Chen, H. Li, W. Tian, and C. Zhou, PZT Based Piezoelectric Sensor for Structural Monitoring, Journal of Electronic Materials 48, 2916 (2019)

Authors : Anand Babu and Dipankar Mandal
Affiliations : Quantum Materials and Devices Unit, Institute of Nano Science and Technology, Knowledge City, Sector 81, Mohali, 140306, India

Resume : With the growing demand for portable electronics, self-powered devices and sensors are promising, it need not give any external source or energy storage device to operate, rather can employ our daily activities such as walking, jogging, and even talking as input for functioning. To make the devices self-powered, piezoelectric polymer shows superiority as these are stretchable, flexible, and mostly biocompatible in nature and not required any external bias like piezoresistive and piezo capacitive to operate. Dipole alignment and crystallinity are the key parameters to determine the piezoelectricity in a material, researchers used numerous complex methods such as stretching, bending, and quenching to enhance piezo response. Here, we have proposed an effective way to enhance the degree of dipole alignment and crystallinity, leads to increase the piezo response in the material. This phenomenon is observed in the nanofibers, producing from the electrospinning by applying negative polarity voltage. Conventionally, nanofibers are produced by applying the positive voltage (positive electric field) between the tip of the syringe and the collector in an electrospinning setup. Here, we have reversed the electric field direction by applying the negative voltage polarity, which results in a high degree of dipole alignment and subsequently elevates the crystallinity, achieving a piezoelectric charge coefficient d33 of 27 pm/V; this was three times higher than their positive voltage counterpart. Piezoelectric nanogenerators (PNGs) are fabricated to assess the piezoelectric performance of nanofibers manufactured by applying positive and negative polarity voltage. It is further noticed that the PNG based on negatively biased nanofibers exhibited mechanosensitivity 11 times higher than the PNG based on positively biased nanofibers. As a result, excellent bio-sensing capabilities of negative bias generated nylon-11 nanofibers enable tracking of physiological events such as arterial pulse, carotid pulse, and various facial expressions for a next-generation health care system.

Authors : Qinrong He, Han Zhang, Joe Briscoe*
Affiliations : School of Engineering and Material Science and Materials Research Institute, Queen Mary University of London, London, E1 4NS

Resume : “Internet of Things” (IoT) has attracted intensive interest for the field of wireless, portable and monitoring fields. In the regard, wearable nanogenerators hold great potential because they can harvest the energy from body movement and surrounding environment to provide sustainable power supply for these electronic devices. Zinc oxide (ZnO) nanostructures have been extensively investigated for harvesting mechanical power owing to its low cost, non-toxicity and easy synthesis. [1-3] Flexible substrates, such as textile and carbon fibre, have attract lots of attention due to its unique properties of lightweight, comfort and mechanical durability. Herein, PEDOT:PSS/CuSCN/ZnO based devices are successfully fabricated on conductive Cu/Ni coated textile and carbon fibres, respectively. PEDOT:PSS/CuSCN structure was fabricated on ZnO nanorods to reduce the rate of screening to achieve higher performance output. The textile-based device generated increasing output voltage from 0.2 V to 1.81 V as the shaking frequency increases from 19 Hz to 26 Hz. The output voltage from the device can activate an LCD screen display by shaking at its resonant frequency. Carbon fibre-based devices were also fabricated, which generated increasing output voltage from 1.4 V to 7.6 V as the acceleration from an impacting force increased from at 0.1 m/s2 to 0.4 m/s2. Both of the above flexible devices exhibited high stability and durability under 26000 cycles test, which were also able to harvest energy from biomechanical forces such as impacting, flicking and gentle finger tapping and bending. In addition, based on carbon fibre its composite, carbon fibre-reinforced plastic (CFRP), CFRP-based self-power sensor was also fabricated, which exhibited output voltage from 0.27 V to 3.53 V under different impacting acceleration from 0.1 to 0.4 m/s2 with good stability during the 26000 cycles test. The results provides an efficient method to develop energy harvester on carbon fibres, which hold great potential for the future designing of flexible self-powered devices and wearable electronics.

Authors : Andris Šutka,1 Linards Lapčinskis,1 Kaspars Mālnieks,1 Artis Linarts,2 Osvalds Verners1
Affiliations : 1. Institute of Materials and Surface Engineering, Faculty of Materials Science and Applied Chemistry, Riga Technical University 2. Institute of Technical Physics, Faculty of Materials Science and Applied Chemistry, Riga Technical University

Resume : Polymer contact electrification (CE) has taken an important role for harvesting wasted mechanical energy from ambient noise, biomechanical movements, or mechanical vibrations. Devices which exploit polymer CE are called triboelectric nanogenerators (TENG). These devices can be integrated in various systems to harvest energy from different sources. Harvested energy can be used for powering microdevices, thus replacing batteries, or excluding the necessity for wiring to supply power. This is especially important for Internet of Things (IoT). IoT describes the network of physical objects, that are embedded with sensors, software, and other technologies for the purpose of connecting and exchanging data with other devices and systems over the internet. It is estimated that the IoT will host at least 40 billion connected devices by 2025. The successful integration of TENG devices highlight the pathway to reduce the environmental burden. Different approaches exist to magnify the surface charge on polymer from CE, including surface functionalization, adjustment of the physicochemical properties between contacting materials, or by increasing the specific contact area via nanostructuring. In addition, strategy inspired from natural spider silk can be applied. It has been shown that the irregularities in surface hardness end up with the stress accumulation, which reduce the energy for covalent bond break. Covalent bond break and material transfer is well proven mechanism for polymer contact electrification. The output of the TENG device can be enhanced also by applying ferroelectric polymers in contacting layers where piezoelectric charges contribute to surface charge for electrostatic induction, thus increasing the output. The combination of different approaches allows to develop high performance TENG devices.

Authors : Yan Zhang, Steve Dunn, Hamideh Khanbareh, Chris R Bowen, Nguyen Phuc Hoang Duy, Pham Thi Thuy Phuong
Affiliations : Yan Zhang1; Steve Dunn2; Hamideh Khanbareh3; Chris R Bowen3;Nguyen Phuc Hoang Duy4; Pham Thi Thuy Phuong4 1 ~ State Key Laboratory of Powder Metallurgy, Central South University, Changsha, 410083, Hunan, China 2 ~Chemical and Energy Engineering, London South Bank University, London, SE1 0AA 3 ~ Department of Mechanical Engineering, University of Bath, Claverton Down, Bath, BA2 7AY, UK 4 ~ Institute of Chemical Technology, Viet Nam Academy of Science and Technology, Ho Chi Minh, Vietnam

Resume : A number of studies have reported the use of vibration coupled with ferroelectric materials for water splitting. However, improving the efficiency and stability of these systems continues to remain a challenge, including long-term stable produce of products and the formation of a stable suspension. Here we report the production of a nanofluid based on BaTiO3 containing a mixture of cubic and tetragonal phases that splits water under ultrasound. X-ray analysis shows that the BaTiO3 is a mixture of cubic and tetragonal phases. The particle size reduces from an initial distribution of approximately 400 nm as delivered to a distribution of approximately 150nm after the application of ultrasound. This fine scale nature of the particulates leads to the formation of a stable nanofluid of suspended BaTiO3 particles. We demonstrate stable H2 and O2 evolution at the predicted 2:1 ratio. In further lifetime tests we show repeatable H2 evolution over a period of 4 days with a continuous 24-hour period of stable catalysis. The maximum rate of H2 evolution found was 270 mmol/h/g for a loading of 5mg/L of BaTiO3 in 10% MeOH/H2O leading to the highest efficiency of piezoelectrically driven water splitting that has been reported thus far. This work indicates that the potential of harnessing vibration for water splitting in functional materials systems.

Poster session Symp A : Ana Borras, Joe Briscoe, Anjana Devi
Authors : R. D. I. G. Dharmasena
Affiliations : Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, LE11 3NR, United Kingdom

Resume : Introduction Triboelectric Nanogenerators (TENGs) are a leading candidate to power the future portable and wearable electronics [1]. TENGs operate through triboelectric charging and electrostatic induction to convert ambient movements into electricity [2]. Studies on triboelectric charging have been limited to symmetric charging, where dissimilar TENG contact surfaces obtain equal amounts of static charges with opposite polarities [3]. This leaves a gap on the understanding of TENG outputs during asymmetric charging situations. Moreover, reports on how identical TENG surfaces can be used successfully for TENG output generation are scarce. Such drawbacks limit the versatility of TENGs in terms of optimising materials, device designs and output generation [4]. Methods This work studies triboelectric charging of dielectric TENG surfaces by analysing the material transfer between their contact surfaces. The nanoscale materials transfer during the operation of a contact-mode TENG is studied using X-ray photoelectron spectroscopy and electron microscopy for different material types, contact pressures and motion profiles. Based on these outcomes, a charge density engineering technique is introduced where selected TENG surfaces are contact charged at nanoscale against an external material surface. This creates an asymmetrically charged TENG with significantly improved outputs. Consequently, the distance-dependent electric field platform is used to develop the first theoretical model which can simulate the outputs of asymmetrically charged TENGs. This platform is used to design and fabricate asymmetrically charged TENGs consisting of dissimilar contact surfaces [TENG surfaces - polydimethylsiloxane (PDMS) and polyethylene terephthalate (PET), external surface - nitrile] as well as identical TENG contact surfaces [contact surfaces - PET and PET, external surface - nitrile]. Results and Discussion The TENG with dissimilar contact surfaces provided 469% power output increase (avg. power under 1m, 1Hz sine motion) through asymmetric charging (24.4 mW/m2) compared to the conventional TENG design (5.2 mW/m2), whereas the TENG with identical contact surfaces provided 6076% power output increase (9.48 mW/m2) via asymmetric charging compared to conventional TENG (0.156 mW/m2), showing remarkable improvements. This method enables the identical contact surfaces to be used to generate significant TENG outputs. The stability of the asymmetrically charged TENGs were examined, showing only 2.5% output reduction within 24 hours. Moreover, this study revealed several new factors affecting triboelectric charging, and significantly improved the outputs and design versatility of TENGs, paving the way towards practical TENG applications. References [1] Wu et al., Adv. Energy Mater. 2018, 1802906 [2] Dharmasena et al., Energy Environ. Sci. 2017, 10(8), 1801-1811 [3] Dharmasena et al., Adv. Energy Mater. 2018, 8, 1802190 [4] Dharmasena et al., Nano Energy 2021, 90, 106511

Authors : A. Alvarez, A. Petritz, P. Schäffner, M. Belegratis, M. Adler, J. Groten, B. Stadlober
Affiliations : MATERIALS Institute of JOANNEUM Research Forschungsgesellschaft mbH, 8160 Weiz, Austria

Resume : There is an increasing demand in smart sensor nodes for condition monitoring and predictive maintenance of industrial engines and critical energy infrastructure. These sensor nodes collect data of a target object (e.g. an electric engine or generator) and/or its environment in order to detect any malfunction or failure and instantly trigger necessary maintenance actions. This way, further damage and extended downtimes can be prevented and consequently enable an extended lifetime, reduced material waste and CO2 emission. To power such deployed sensor nodes, energy harvesting of environmental energy is most suitable and preferred over environmentally problematic batteries. One energy source readily available especially in industrial environments or power plants is vibration energy from machines driven by electric engines or electric generators. Since this vibration has usually a fixed fundamental frequency of 50 Hz or 25 Hz, resonating structures like cantilevers with piezoelectric transducers are promising harvesters. While piezoelectric ceramics offer higher piezoelectric parameters, piezoelectric polymers are less brittle, more flexible and easier to process in large scale, reducing costs per unit. Usually, these transducers consist of the piezoelectric layer sandwiched between two electrodes on a flexible substrate. To push their output power level, stacking of multiple transducers or processing multilayers of the piezoelectric material is required. In this work, we compare such approaches for P(VDF-TrFE)-based transducers under realistic conditions. These conditions imply the aforementioned fixed low vibration frequency and rather low vibration acceleration, around 1-2 m/s² (RMS value). Furthermore, a higher output voltage level improves the conversion efficiency during rectification and storage, but should be adjusted to the operation voltage of the sensor node. For a given active volume, multistacking increases the current output due to higher electrode area, but a single, thick layer increases the voltage output of the transducer. Thus, output voltage/current optimization is necessary. For doing so, P(VDF-TrFE) transducers were fully screen-printed on PET substrates both in single and multiple stack configuration. The resonance frequency was kept constant by controlling the length of the cantilever as well as by adding a tip mass. A normalized average output power of 42 µW/ms-2 was achieved at 25 Hz (24.6 cm² transducer area). The performance of the transducers in combination with a full wave rectifier and a charging capacitor is demonstrated both in lab as well as in industrial environments.

Authors : Donghyun Kim, Bong-Gu Kim, Haeun Kim, Haeun Seo, Dong Gyeong Kim, Hyeryang Choi, Junseong Kim, SeungCheol Yang
Affiliations : Department of Materials Convergence and System Engineering, Changwon National University

Resume : Flow-electrode Capacitive Mixing(F-CapMix) system is a new renewable energy technology that generates electricity using the ion adsorption/desorption system made of porous carbon material in flow electrode and the difference in concentration between flow electrode and feed water. However, activated carbon (AC) with relatively low electrical conductivity compared to other carbon materials(graphene, CNT) causes low electron percolation and power generation. In this study, to improve power generation performance of the F-CapMix, Nitrogen-rich precursor Melamine was heat-treated to dope the AC surface with nitrogen, and then surface analysis, powder resistance and change in F-CapMix power generation performance were measured. C-N, C=N binding to activated carbon surfaces was confirmed through XPS and Raman, FT-IR, and the power generation of N-doped AC (6 wt%) was 41.38% higher than that of conventional AC. Through these results, it is believed that the limitation of F-CapMix power generation, which still has a lower power generation amount than other Salinity Gradient Power(RED, PRO), can be improved.

Authors : Ki Chang Kwon, Hosun Shin
Affiliations : Korea Research Institute of Standards and Science (KRISS)

Resume : 2D transition metal dichalcogenides (2D TMDs) have attracted considerable attention recently owing to their superior physical and chemical properties. These 2D materials have shown great potential for thermoelectric (TE) energy generation due to their unique electrical and thermal transport properties originated from their unique atomic structures. The calculated and predicted thermoelectric performance should exhibit outstanding TE performance, however, it still lacks of experimental confirmation. Furthermore, a reliable and a robust preparation and characterization methodologies for proving the 2D TMDs-based TE materials are underdeveloped. The measured and reported TE performance of 2D TMDs is still much lower than that of conventional bulk TE materials such as BST, because of higher thermal conductivity and lower seebeck coefficient. Here, we demonstrate that the enhanced TE performance of 2D TMDs by a facile anion-engineering. Phosphorus doped 2D TMDs show the highly enhanced seebeck coefficient and electrical conductivity, which can lead high power factor. Furthermore, the low thermal conductivity can be achieved by defects and doped phosphorous atoms in 2D TMDs atomic structure. This work can pave a way to achieve high TE performance of 2D TMDs-based TE materials.

Authors : Niklas Huster, David Zanders, Detlef Rogalla, Anjana Devi
Affiliations : Inorganic Materials Chemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44801 Bochum, Germany; RUBION, Ruhr University Bochum, 44801 Bochum, Germany

Resume : The fabrication of SnOx in thin film form via chemical solution deposition (CSD) processes is favored over vacuum-based techniques as it is cost effective and simpler. The precursor employed plays a central role in defining the process conditions for CSD. Particularly for fabricating SnO2 layers that are appealing for sensor or electronic applications, there are limited precursors available for CSD. Thus, the focus of this work was to develop metalorganic precursors for tin, based on the ketoiminate ligand class. By systematic molecular engineering of the ligand periphery, a series of new homoleptic Sn(II) β-ketoiminate complexes was synthesized and thoroughly analyzed by spectroscopy and thermogravimetry methods. The solid state molecular structure of [Sn(MPKI)2] was analyzed by means of single crystal X-ray diffraction (SCXRD). Interestingly, this class of compounds features excellent solubility and stability in common organic solvents alongside good reactivity towards H2O and low decomposition temperatures, thus fulfilling the desired requirements for CSD of tin oxides. In this study, we have demonstrated the possibility to directly deposit SnOx layers via hydrolysis upon exposure to air followed by heat treatment under oxygen at moderate temperatures. Most importantly, the precursor solution is readily prepared without need for additives or long stirring times which are often required in the preparation of CSD precursor solutions. A range of complementary analytical methods were employed, namely X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to analyze the structure, morphology, and composition of the deposited SnOx layers. The deposited nanocrystalline, oxygen rich SnO2 thin films feature a high surface area and oxygen vacancies based on film composition analysis, thus bear promising properties for application as sensor material.

Authors : M.I Rodríguez-Tapiador1, J. Merino2, T. Jawhari3, A.L Rosales4, J.Bertomeu4, S. Fernández1
Affiliations : 1Energy Department, CIEMAT, Av. Complutense 40, Madrid 28040, Spain. 2University Rey Juan Carlos, Technology Support Center CAT, Tulipán, s/n, Móstoles 28039, Madrid, Spain 3Unitat d'espectroscòpia, Raman Centres Científics i Tecnològics de la Universitat de Barcelona – CCiTUB, Lluís Solé i Sabaris, 1-3 08028 Barcelona, Spain 4Departament de Física Aplicada, Universitat de Barcelona, Barcelona, Spain

Resume : Nowadays, the copper nitride (Cu3N) is of great interest as a new solar absorber material, flexible and lightweight thin film solar cells. This material is a metastable semiconductor, non-toxic, composed of earth-abundant elements, and its band gap energy can be easily tunable in the range 1.4 to 1.8 eV. Cu3N shows different properties depending on the structure of the material: Cu-N bonds can offer metallic electrical properties (Cu4N) or a semiconductive behavior (Cu3N). For this reason, it has been proposed for many applications in the solar energy conversion fields. For the deposition of Cu3N films, reactive magnetron sputtering is one of the most used because the film properties can be easily modified by changing the sputtering parameters. The main aim of this work is to evaluate the properties of the Cu3N thin films fabricated by reactive radio-frequency (RF) magnetron sputtering at different RF power values to determine its potential as light absorber. The Cu3N films were fabricated at room temperature (RT) from a commercial 3-inch diameter Cu metallic target (purity: 99,99%) on different substrates (silicon and glass). The layers were deposited at the RF power values ranged from 25 to 200 W. The pure nitrogen flux was set to 20 sccm, and the working pressures were 3,5 Pa and 5 Pa. The morphology and microstructure of the Cu3N thin films were characterized by Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR), RAMAN spectroscopy and X-ray Diffraction (XRD), respectively. AFM images revealed a granular morphology, while FTIR and RAMAN spectra exhibited the characteristics peaks related to Cu-N bonds of Cu3N, that became narrower when the RF power increased. Finally, to stablish the suitability of these films to be used as absorber, the optical properties were obtained from transmission spectra carried out with a Perkin Elmer 1050 spectrophotometer.

Authors : Le Hanh Vi (1), Mekan Piriyev (1), Gabriel Loget (2), Bruno Fabre (2), Tony Rohel (1), Antoine Létoublon (1), Christophe Levallois (1), Karine Tavernier (1), Yoan Léger (1), Nicolas Bertru (1), Charles Cornet (1)
Affiliations : 1. Univ Rennes, INSA Rennes, CNRS, Institut FOTON-UMR 6082, F-35000, Rennes, France. 2. Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes)-UMR6226, Rennes F-35000, France.

Resume : One of the most important problems facing humanity nowadays is the production and storage of clean, renewable and low-cost energy. Solar photoelectrochemical (PEC) hydrogen production could potentially meet the above criteria, through the direct conversion of solar energy into hydrogen, one of the most eagerly awaited solar fuels. Developing stable, low cost and efficient photoelectrodes for PEC cells is thus an essential step of this research field. Among the forecast materials for photoelectrodes, group III-V semiconductors have exhibited remarkable performance thanks to their appropriate and tunable band gap [1], transport properties and high quantum yield [2], making them good candidates for unassisted PEC water splitting. In particular, GaAs was shown to have a high theoretical solar energy conversion efficiency of 33% [3]. However, the most significant drawbacks of III-Vs are the overall instability of the semiconductor/liquid interfaces, their high substrate cost and their composition, based on critical resources. To address these issues, in this work, we report on the photoelectrochemical behavior of a 1 µm-thick GaAs film grown on a low-cost p-type Si substrate by Molecular Beam Epitaxy. GaAs/Si photoelectrodes exhibited both cathodic and anodic photocurrents in 0.2 M H2SO4 (aq), indicating that our electrodes could be used to trigger both hydrogen and oxygen evolution reactions. A photocurrent density of 7 mA/cm2 at -1 V vs Reversible Hydrogen Electrode (RHE) was measured in the photocathode regime and 17 mA/cm2 at 1.5 V vs RHE in the photoanode regime. These values are competitive compared to the performances of electrodes based on GaAs commercial wafers. More than this, the GaAs/Si photoelectrode showed a good lifetime of more than 15 hours in cathodic regime. Electrochemical impedance spectroscopy and Mott-Schottky measurements were also performed, revealing additional surface or interface states in GaAs/Si photoelectrodes compared to GaAs-wafer based electrodes. These findings reveal interesting optimization paths for our photoelectrodes based on III-V thin films on silicon and towards the fabrication of unassisted PEC cells for green hydrogen production. References [1] S. Tiwari et D. J. Frank, «Empirical fit to band discontinuities and barrier heights in III–V alloy systems,» Applied physics letters, vol. 60(5), pp. 630-632, 1992. [2] G. Siddiqi, Z. Pan et S. Hu, «III–V semiconductor photoelectrodes.,» Semiconductors and Semimetals , vol. 97, pp. 81-138, 2017. [3] J. R. Bolton, S. J. Strickler et J. S. Connolly, «Limiting and realizable efficiencies of solar photolysis of water.,» Nature, vol. 316(6028), pp. 495-500, 1985.

Authors : Kyota Uda1, Tensho Nakamura1, Yuki Tsuda2, Lina Sun3, Yoshiyuki Suzuri3, Masatoshi Yanagida4, Tsukasa Yoshida1
Affiliations : 1 Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan 2National Institute of Advanced Industrial Science and Technology (AIST), Osaka, Japan 3 Innovation Center for Organic Electronics (INOEL), Yamagata University, Yonezawa, Yamagata, Japan 4 National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, Japan

Resume : Copper(I) thiocyanate (CuSCN) is known as a wide bandgap p-type semiconductor and recently demonstrated its high ability as a hole-transporting material in perovskite solar cells and light emitting diodes fabricated by simple solution coating and drying [1]. In fact, little is known for physical properties of CuSCN, such as bandgap, band positions, optical transparency and mobility. We have established methods to electrodeposit well-crystallized CuSCN thin films in various forms. Although the electrochemistry is fairly simple as limited by diffusion of 1 : 1 complex ([Cu(SCN)]+), the [Cu2+] : [SCN-] ratio, its absolute concentration and solvent can alter the morphology and crystal orientation of resulting CuSCN [2]. These unique features of the electrodeposition technique let us anticipate possibilities to tailor-tune physical properties of CuSCN to match the demands for flexible device applications. In this study, we have carried out electrodeposition of CuSCN to vary its morphology and crystal orientation by tuning the bath composition and studied their band structure to explore the room for tuning its physical properties for thin film diodes and hybrid electroluminescence devices. Morphologies of CuSCN thin films electrodeposited from stoichiometric (REF), Cu-rich and SCN-rich baths are changed. While the REF sample has an open structure made of relatively large bulky particles, the Cu-rich sample is dense, made of tiny grains to expose their hexagonally shaped top. XRD patterns have found almost parallel orientation for the SCN-rich and a high degree of preference of the Cu rich to orient the c-axis of β-CuSCN perpendicular to the substrate. Although all these films indicate nearly the same energy gap of about 3.6 eV estimated by Tauc plot, significant difference was found for their work function (WF) measured by photoelectron yield spectroscopy (PYS). The threshold energy moved downwards from 5.23 to 5.66 eV vs. VAC from Cu-rich to SCN-rich film. The result indicates a high level of p-type doping in the presence of excess SCN-, probably due to increased concentration of Cu2+ as stabilized by SCN- bound to it. Simple devices as ITO / electrodeposited CuSCN / Aluminium were fabricated to examine their diode behaviour. While all of the devices employing the electrodeposited CuSCN thin films showed good rectifications in the J-V curves, the change in onset voltage from Cu-rich to SCN-rich samples confirm tunability of the device property by conditions of the electrodeposition. Successful operation of organic light emitting diode was also achieved by employing the electrodeposited CuSCN as a hole-injection layer. The device employing the electrodeposited CuSCN achieved a smaller turn-on voltage than that with spin-coated CuSCN in the I-V-L measurements. Furthermore, the electrodeposited CuSCN also functioned as perovskite solar cells. [1] Vinod E. Madhavan et al., ACS Energy Lett., 1, 1112, 2016 [2] Lina Sun et al., Physics Procedia, 14,12, 2011

Authors : Pamela Machado, Pol Salles, Mariona Coll
Affiliations : ICMAB-CSIC

Resume : Complex oxides are of great interest for their rich variety of chemical and physical properties including magnetism, ferroelectricity, multiferroicity, catalytic behavior, and superconductivity. Up to date, the preparation of crystalline complex oxide thin films has been mainly limited on substrates that can stand high temperature thermal treatments and on single crystal substrates when epitaxial growth is pursued. These requirements dramatically limit their applicability excluding the possibility to prepare many artificial multilayered architectures to investigate emergent phenomena that arise in thin films and at their interfaces. To tackle this bottleneck, herein, we will present a facile and sustainable chemical route to prepare water-soluble epitaxial Sr3Al2O6 thin films to be used as sacrificial layer for future free-standing epitaxial complex oxide manipulation. Two solution processes are put forward based on metal nitrate and metalorganic precursors to prepare dense, homogeneous and epitaxial Sr3Al2O6 thin films that can be easily etched by milli-Q water. [1] Thorough investigation of the precursor-solvent compatibility, thermogravimetric analysis and film crystallization is performed. Additionally, we demonstrate the viability of Sr3Al2O6 to subsequently prepare and transfer a wide variety of atomic layer deposited functional oxides (Al2O3, Co3O4, Fe2O3, CoFe2O4, BiFeO3) on arbitrary substrates ranging from flexible polymers to silicon substrate. [2] This robust and low-cost procedure could be adopted to prepare a wider family of thin film compositions to fabricate artificial heterostructures and 2D materials with monolayer by monolayer control to go beyond the traditional electronic, spintronic, and energy storage and conversion devices. [1] P. Salles, M.Coll et al. Adv. Mater. Interf, (2021), 8, 2001643 [2] P. Salles, M. Coll ACS Applied Materials Interfaces (2022)

Authors : Onuralp Cakir1, Doga Doganay1, Melih Ogeday Cicek1, Sahin Coskun2, Ozge Demirtas3, Alpan Bek3,4 , Husnu Emrah Unalan1
Affiliations : 1. Department of Metallurgical and Materials Engineering, Middle East Technical University (METU), 06800, Ankara, TURKEY; 2. Department of Metallurgical and Materials Engineering, Eskisehir Osmangazi University (ESOGU), 26040, Eski?ehir, TURKEY; 3. Micro and Nanotechnology Program, Middle East Technical University (METU), 06800, Ankara, TURKEY; 4. Department of Physics, Middle East Technical University (METU), 06800, Ankara, TURKEY.

Resume : Production of a transparent and conductor silver nanowire (AgNW) network involves a trade-off between the two main variables that are optical transmittance and sheet resistance. Even though AgNWs themselves have a defect free structure, the surrounding polyvinyl pyrrolidone (PVP) layer hinders the wire-to-wire electron transfer and creates junction resistance in the order of M? levels. This incomplete metal-metal contact of AgNWs create a challenge in the production of high-performance transparent conductors. Great efforts have been made to solve this problem. However, the literature still is incomplete as in all of the works, the used AgNWs have different lengths, diameters, PVP thicknesses and purities. As a result, the effectiveness of a particular post treatment on AgNWs with different properties is still unknown. There is no consensus on what a good and facile combination of methods is. In this study, various post treatment methods available in the literature are examined and the most successful post treatment method was developed. The combination of the optimal post treatments on the AgNW networks resulted in the reduction of the sheet resistance from 5000 ?/sq to 24 ?/sq with an optical transmittance of 92%. Furthermore, the use of optimized AgNW networks in a liquid-solid interface triboelectric nanogenerator system as the current collector layer is explored. A thin PDMS layer is spin coated onto the AgNW network to fabricate transparent TENG electrodes. The triboelectric response between water droplets and the PDMS layer is investigated. The TENG device is found to produce up to 1.8 V and 40 nA per water droplet. The resulting transparent self-powered sensor with optimized AgNW network is suitable for many sensing applications such as chemical concentration measurement and heater activation. This work was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) under Grant No: 121N708 and No: 119N413.

Authors : Onur Demircioglu, Melih Ogeday Cicek, Doga Doganay, Günay Gazaloglu, Ahmet Cevdet Yalciner, Husnu Emrah Unalan
Affiliations : Department of Metallurgical and Materials Engineering, Middle East Technical University (METU), 06800, Ankara, TURKEY; Department of Metallurgical and Materials Engineering, Middle East Technical University (METU), 06800, Ankara, TURKEY; Department of Metallurgical and Materials Engineering, Middle East Technical University (METU), 06800, Ankara, TURKEY; Department of Civil Engineering, Middle East Technical University (METU), 06800, Ankara, TURKEY; Department of Civil Engineering, Middle East Technical University (METU), 06800, Ankara, TURKEY; Department of Metallurgical and Materials Engineering, Middle East Technical University (METU), 06800, Ankara, TURKEY, Energy Storage Materials and Devices Research Center (ENDAM), Middle East Technical University (METU), 06800 Ankara, Turkey

Resume : Triboelectric nanogenerators (TENGs) have been of great interest since they were proposed. Power is generated by static electricity caused by the contact of two separate surfaces. Therefore, any place where there is motion can be an effective workplace for TENGs to be used as both self-powered sensors and energy harvesting units. Given situations like these, water waves are one of the best places to get most out of TENGs to harness waste energy. In this study, a low-cost adaptation of a TENG is made by modifying a commercial buoy used by sailors and marine workers for an alarm or guidance system. TENG is prepared by coating inside of a buoy with polyurethane (PU) foam and hiring a pendulum mechanism as a counter triboelectric layer by coating an aluminum ball with poly (dimethyl siloxane) attached to a spring in the buoy. As a result, triboelectrification is provided in a frequency independent regime by contact-separation. From the measurements taken in a coastal port laboratory to simulate a real case of sea waves an open circuit voltage (Voc) of 141 V and short circuit current (Isc) of 8.89 µA is obtained. In addition, a power of 1.07 W/m2 is obtained under a wave frequency of 1 Hz and a wave height 11.8 cm, which is characteristic of Turkey’s typical coastal waves, at an impedance match of 300 MΩ.

Authors : Abhishek Ghosh*, Prashant Bisht, Narinder Kaur, Chandan K Vishwakarma, Mujeeb Ahmad, Per Erik Vullum, Branson D.Belleb, Bodh Raj Mehta
Affiliations : Department of Physics, Indian Institute of Technology Delhi, New Delhi, 110016, India

Resume : The present study demonstrates a significant enhancement in the Seebeck coefficient and thermoelectric (TE) power factor in Sb2Te3- AgSbTe2 nanocomposite thin film. The addition of Ag leads to the in-situ formation of AgSbTe2 secondary phase in the Sb2Te3 matrix during the growth resulting in a large Seebeck coefficient. X-ray photoelectron spectroscopy (XPS) valance band spectra in conjunction with first-principal density functional theory-based electronic structure calculation provide conclusive evidence of the formation of Ag induced deep resonant-like states in the valance band, which modifies the density of states (DOS) and results in a two-fold increase in DOS effective mass in the composite samples. In addition, the formation of hetero interface is responsible for carrier filtering in Sb2Te3, which also contributed to the enhanced TE properties. The results highlight the importance of a combined effect of band structure modification and energy-dependent charge carrier scattering for enhancing thermoelectric properties.

Authors : *Atanas Katerski, Robert Beglaryan, Ilona Oja Acik, Malle Krunks *presenting author
Affiliations : Laboratory of Thin Film Chemical Technologies, Department of Materials and Environmental Technology, Tallinn University of Technology, Estonia

Resume : The development of low-cost solar cells based on technology that uses only earth-abundant and non-toxic elements is always in demand and of great interest. Antimony sulphide (Sb2S3) is one such material that is suitable for semi-transparent solar cell applications. The low cost, earth abundance, the suitable direct band gap of around 1.7 eV and the single stable phase1 make Sb2S3 a promising material for use as the absorber in thin-film solar cells. It has been shown2, that ultrasonic spray pyrolysis (USP), which is a low-cost, simple and scalable thin film deposition method, is a suitable technique for depositing Sb2S3 solar cells. The following study aims to investigate the means of controlling the Sb2S3 absorber layer growth and properties, by varying the Sb to S precursor ratios and the deposition temperatures. The Sb2S3 absorber was deposited from a precursor solution of SbCl3/SC(NH2)2 = 1:3 and 1:6 (60mM SbCl3) at 3 different temperatures ? 195°C, 220°C, and 245°C using Glass/FTO/TiO2 as a substrate. Afterwards, the absorber was annealed in a flowing Nitrogen atmosphere at 250°C for 5 minutes. Films were characterized by SEM, XRD, Raman and UV-Vis spectroscopies. The films grown at 195°C were amorphous, whereas when grown at 220°C or 245°C, crystalline stibnite films were obtained, as was confirmed by XRD and Raman spectroscopy measurements. Annealing of amorphous films in a nitrogen atmosphere resulted in crystalline Sb2S3 films, no other phases were detected. The optical bandgap value of crystalline films depended on the film deposition temperature and decreased from 1.78 to 1.66 eV when increasing the deposition temperature from 195°C to 245°C. The crystalline films grown under different conditions were used as an absorber in solar cell devices. Solar cells were built in superstrate configuration Glass/FTO/TiO2/ Sb2S3/P3HT/Au where TiO2 as electron transport layer was grown by USP technique and P3HT as hole transport material was applied by spin coating, followed by annealing in a flowing Nitrogen atmosphere at 175 °C for 5 minutes before the Au back contacts were thermally evaporated. Current-voltage (I-V) measurements were used to evaluate the photovoltaic performance of the fabricated solar cell devices. The results have shown, that there is a drop in open-circuit voltage and power conversion efficiency (PCE) values when increasing the Sb2S3 deposition temperature from 195°C to 245°C. The highest PCEs of ca 5.2 % were achieved using a two-step procedure for the absorber preparation ? first depositing amorphous Sb2S3 and then crystallizing afterwards. Differences in growth mechanisms and properties of crystalline Sb2S3 films deposited at different temperatures will be discussed. 1. Yang Yang, et al. Solar Energy, 2021, 217, 25-28 2. Jako S. Eensalu, et al. Beilstein J Nanotechnol. 2019; 10: 2396?2409. 3. Xin Jin, et al. Adv. Funct. Mater, 2020, 30: 2002887

Authors : Madsar Hameed, Oliver Jelley, Lokeshwari Mohan, Joe Briscoe
Affiliations : Queen Mary University of London

Resume : Perovskite solar cells (PSC’s) have revealed remarkable development in recent years with rapid increases in efficiency, from about 3% in 2009 to over 25% today. While perovskite solar cells have emerged to be highly efficient in a very short time, still various challenges remain before they can become a competitive commercial technology. Hence it is a dire need to improve the PSC’s stability, degradation and efficiency by enhancement of thin film homogeneity, grain size (eliminating grain boundaries) and by morphological and compositional modification. However, solvent processing and thermal annealing generates relatively small grains during rapid perovskite crystallization. The presence of small grains is an indication of the existence of local inhomogeneity in these films in terms of lattice strains and material composition with the local inhomogeneity being observed not only intergrain but also intragrain. In addition, the grain boundaries can host defects an increase recombination rates, as well as degradation. Therefore, eliminating the local inhomogeneities, particularly at the grain boundaries, is a crucial path to enhance performance of perovskite optoelectronic devices[1]. Formamidinium lead iodide (FAPbI3)-based perovskites have emerged as one of the most promising candidate materials for high efficiency and stable perovskite solar cells due to their high thermal sta-bility, excellent optoelectrical properties and ideal bandgap energy. However, the phase degradation of black FAPbI3 perovskite phase to yellow non perovskite phase at ambient conditions restricts the long-term stability of FAPbI3 perovskite solar cells. We have previously demonstrated a method for performance and stability improvements in formamidinium lead iodide (FAPbI3)-based perovskites by crystallisation in the presence of a solvent aerosol[2]. Here, we develop this method further by adding methylammonium thiocyanate (MASCN) to the solvent aerosol for crystallisation of FAPbI3 perovskite films, following our previous work demonstrating additive-enhanced post-treatment of perovskite films[3]. Adding MASCN to the aerosol leads to further improvements in crystallinity and grain size compared to solvent-only treated films. These changes lead to prolonged charge-carrier lifetimes and ultimately improved device efficiencies. By demonstrating the benefit of additives in this aerosol-assisted crystallisation process, this work opens up wider processing options to enhance the crystallinity, grain size, film homogeneity and efficiency of perovskites. References [1] T. Du, S.R. Ratnasingham, F.U. Kosasih, T.J. Macdonald, L. Mohan, A. Augurio, H. Ahli, C.‐T. Lin, S. Xu, W. Xu, R. Binions, C. Ducati, J.R. Durrant, J. Briscoe,* M.A. McLachlan,*Adv. Energy Mater. 2101420 (2021). [2] Du, T., Macdonald, T. J., Yang, R. X., Li, M., Jiang, Z., Mohan, L.,& Briscoe, J. (2022),Advanced Materials, 34(9), 2107850. [3] T. Du,F. Richheimer,K. Frohna, N. Gasparini, L. Mohan, G. Min, W. Xu, T.J. Macdonald, H. Yuan, S.R. Ratnasingham, S. Haque, F.A. Castro, J.R. Durrant, S.D. Stranks, S. Wood, M.A. McLachlan, J. Briscoe,Nano letters.(2022).

Authors : Byeong-Cheol Kang, Sang-Joon Park, and Tae-Jun Ha*
Affiliations : Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Korea

Resume : With an increasing demand for powering various electronics, energy-harvesting devices have attracted considerable attraction in the fields of self-powered systems [1]. In this regard, researchers have demonstrated various types of nanogenerators such as triboelectric, piezoelectric, and pyroelectric nanogenerators [2]. However, these nanogenerators produce instantaneous alternating output current and exhibit low energy conversion efficiency, which is not suitable for self-powered electronics requiring sustainable direct current (DC) power [3]. In this presentation, we will demonstrate solution-processed nanocomposites for high-performance hygroelectric generators, which enable to produce continuous and stable electricity for self-powered systems. Effective collecting charges directly generated from atmospheric humidity are investigated to investigate the effect of nanocomposition on the device performance of hygroelectric generators. We will also discuss the characteristics of open-circuit voltage and short-circuit current in nanocomposite-based hygroelectric generators under different relative humidity conditions. Long-term sustainability and reliability of the electrical output performance are demonstrated in the developed hygroelectric generators. We believe that this work can open-up a new route for emerging nanocomposite materials for self-powered electronics. [1] M. Ha, J. Park, Y. Lee, H. Ko, ACS Nano 9, 3421-3427 (2015). [2] S. Korkmaz, İ. A. Kariperbc, Nano Energy 84, 105888 (2021). [3] D. Liu, X. Yin, H. Guo, L. Zhou, X. Li, C. Zhang, J. Wang, Z. L. Wang, Sci. Adv. 5, eaav6437 (2019). Acknowledgments This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2021R1A2C2012855)

Authors : Safa Ali Al Siyabi Charl F. J. Faul
Affiliations : University of Bristol

Resume : It is not hidden to any of us the impact that the different environmental issues have on the health of living organisms in general, and on humans in particular. Polluted water and climate change can be considered as the most challenging problems threatening the global health. CO2 capture, storage, and conversion (Leung, Caramanna, and Maroto-Valer 2014) are now being researched in a variety of research fields and technologies. In addition to that, a great attention was given to the studies focusing in the possible techniques that can be applied in the purification of water through heavy metals removal (Senguttuvan et al. 2021). In the recent decades, the porous polymers showed a significant role in many applications that enhance the environmental health aspects. One category of these polymers is the conjugated microporous polymers (CMPs)(Cooper, 2009): the materials that known to combine many favourable properties like; π-conjugated networks with permanent porosity and high chemical and thermal stabilities. Therefore, polyaniline-based conjugated microporous polymers have attractive capabilities due to the inherent redox states of polyaniline and the ability to fine-tune their pore size distribution and surface area (Liao, Weber, and Faul 2014) & (Chen et al. 2019). In this approach, we synthesized different forms of aniline-based redox-active polymers based on Tris(4-bromophenyl)amine as a core with different linkers through Buchwald-Hartwig cross coupling reaction. Different characterizations were done to understand the properties of the polymers including determination of porosity parameters like, surface area and pore size distribution (PSD). The synthesized polymers showed moderate surface area (468 m2/g and good CO2 uptake (9.3 wt %).

Authors : Xingmin Liu1,a, Dan Xu2,a, Hui Ding1, Marc Widenmeyer1, Wenjie Xie1, Maximilian Mellin1, Fangmu Qu1, Guoxing Chen3, Ye Shui Zhang2,4, Zhenyu Zhang2, Aasir Rashid1, Leopoldo Molina-Luna1, Dan J. L. Brett2, Ralf Riedel1, Anke Weidenkaff1
Affiliations : 1 Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 2, 64287, Darmstadt, Germany 2 Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London WC1E 7JE, UK 3 Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS, Brentanostraße 2a, 63755 Alzenau, Germany 4 School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK

Resume : Co-production of carbon nanotube composites (CNCs) and hydrogen (H2) via the pyrolysis-catalysis method provides a promising way for the sustainable upcycling of waste plastics. However, the state-of-the-art catalysts used for the pyrolysis-catalysis of waste plastics suffer from poor conversion efficiency in terms of specific carbon and H2 yields mainly manipulated by the (micro)structure and materials types of the catalysts, thus seriously limiting their industrial applications. In this work, multiscale designed 3 dimension (3D) rose-like CoxMn3–xO4 spinels providing an active site rich structure were developed as smart pre-catalysts for the high-efficiency upcycling of waste plastics. The targeted Co catalysts were formed in situ on a smart support material (here: MnO from reduced CoxMn3–xO4), combining supporting and promoting functionality and hence enabling superior carbon and H2 yields and unprecedented high specific carbon and H2 yield. At a pre-catalyst to plastic weight ratio of 1:14, the carbon and H2 yields can reach 41 wt.% and 36 mmol·g˗1pla., respectively, while the specific carbon and H2 yield can reach as high as 7.48 g˗1cat. and 634 mmol·g˗1pla·g˗1cat., which is more than one order of magnitude higher than that reported in the literature. Density functional theory calculations indicate that the in situ Co based catalyst exhibits an excellent activity in the dissociation of alkanes (e.g., CH4 and C2H6). The resulting carbon demonstrated an excellent discharge capability and extended cycling performance when they were used as a lithium-ion battery anode. This work finds an innovative idea and novel insight for developing advanced catalyst materials as the next generation catalysts for the upcycling of waste plastics.

Authors : A.L. Muñoz-Rosas1,2, J.M. Asensi1,2, J. López-Vidrier1,2, J.M. Asensi1,2, T. Tom1,2, J. Bertomeu1,2
Affiliations : 1 Departament de Física Aplicada, Universitat de Barcelona, Barcelona, Spain 2 Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain

Resume : Cupric oxide (CuO) is considered a sustainable semiconductor for large scale photovoltaic (PV) applications. This is because it is a p-type material with a direct band gap of 1.3-2.1 eV, and high absorption coefficient. In this work, CuO films were deposited on non-heated substrates by RF magnetron sputtering to determine its suitability as light absorber material for solar cells applications. A pure 99.99% CuO target of 3-inch diameter was used to deposit the thin films on Corning glass and silicon substrates. The effect on the film properties of argon and hydrogen + argon atmospheres under chamber pressures of 5, 15, 25, 35 and 45 mTorr at 200 W were studied. Structural, optical and electrical properties of the films were obtained through electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible-NIR optical transmittance, FTIR spectroscopy, and four-point probe analysis. X-ray diffraction patterns present a crystalline CuO layer for the samples deposited in argon atmosphere. However, it is observed a mixture of CuO and Cu2O phases in the samples deposited in hydrogen+argon atmosphere. The latter agrees with the observed FTIR spectra of these samples under these conditions since a little Cu2O shoulder appears in addition to the dominant CuO peak, decreasing when increasing deposition pressure. These peaks could be related to the electrical resistivity observed in the samples. The effect of annealing on the samples at 300°C in forming gas and air, revealed an effect on their electrical and optical properties. Increased resistivity after annealing is found in samples deposited with argon, meanwhile decreased resistivity was observed in samples deposited under hydrogen + argon atmosphere.

Authors : Shane Graham Davies, Steven Paul Hepplestone
Affiliations : University of Exeter

Resume : With ~60% of all generated energy wasted as heat[1], energy harvesting is an important avenue of study to help provide for our worlds increased power demand in a sustainable way. Thermoelectrics (TEs) offer the unique opportunity to recover this previously wasted energy, and improve performance, via a direct conversion of heat to electricity in a solid state device. The key limitation of TEs is their poor power conversion efficiency, characterised by the dimensionless figure of merit, ZT. This value depends on both the electron and phonon transport characteristics, which themselves are heavily interdependent. For optimal TE behavior the electronic conductivity should be high whilst the thermal conductivity is kept to a minimum. However, in the majority of cases an increase in electrical conductivity is accompanied by an increase in thermal conductivity due to the Wiedemann-Franz Law[2], which links the thermal conductivity of electrons to the charge carrier density. It is this interdependence which has effectively limited the maximum ZT achievable to its current value of ~3[3]. Therefore, the ideal technique for raising ZT further would break this interdependence and optimise these characteristics independently. With this in mind, we investigate interfacial patterning as a method for controlling the transport properties of phonons. This method utilises the fundamental difference in electron and phonon wavelengths to selectively scatter phonons and hence reduce thermal conductivity, whilst having a minimal effect on electronic transport. Using density functional theory, we demonstrate the effectiveness of interfacial patterning on Si/Ge structures. We investigate three differently patterned interfaces, noting how subtle changes in the patterning can have dramatic effects on properties such as the effective mass and the lattice thermal conductivity. This patterning provides a technique to enhance ZT and a framework for producing more viable devices from any heterostructure-based TE materials, including materials not traditionally considered for the application. 1. Perspectives on thermoelectrics: from fundamentals to device applications, Energy & Environmental Science, 2012, 5, 5147 2. Ueber die Wärme-Leitungsfähigkeit der Metalle, Annalen der Physik, 1853, 165, 8, 497 3. Advances in thermoelectric materials research: Looking back and moving forward, Science, 2017, 357, 6358, 9997

Authors : Anand Nivedan, Sunil Kumar
Affiliations : Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India

Resume : Temperature-dependent photo-Seebeck effect is reported in a bulk single crystalline Bi2Te3 topological insulator. On light illumination, inhomogeneous laser heating of the thermoelectric material Bi2Te3 leads to the development of a thermoelectric potential across its two ends. The sample shows distinguishable contributions in the measured current due to both the Seebeck effect and the normal photo-generated carriers within a narrow layer of the sample. Experiments are performed to distinctly separate the Seebeck contribution from the photogenerated current. The temperature-dependence of the photocurrent without Seebeck contribution shows a sign reversal from negative to positive at ~220 K with the increasing sample temperature. Moreover, the temperature corresponding to the sign reversal of the photocurrent is not unique and depends on the wavelength of the excitation light. These results are significant for the understanding of Seebeck effect and the photocarrier generation in bismuth telluride for its potential use in thermoelectric and photodetector applications.

Authors : Oleksii Smirnov, Rada Savkina
Affiliations : V. Lashkaryov Institute of Semiconductors Physics, NAS of Ukraine, Nauky av.41, 03028 Kyiv, Ukraine

Resume : The losses in the solar cells are due to a large amount of solar radiation is dissipated by heat. A significant part of the photons has an energy greater than that required for photogeneration of charge carriers and the residual energy is converted into kinetic energy, that is, into heat. Therefore, an important task is to use the dissipated energy. Our main idea is in the combination of photo- and thermo-electrical properties in a single hybrid system to the most efficient conversion of solar energy as well as using the supercapacitor function to increase the energy density of the system and energy storage. We propose the photo-thermoelectric cell based on transitional metal oxide (Fe2O3 and Cr2O3) combined into a hybrid material with organic photo- and thermal- active conjugated polymers (poly-3-hexylthiophene (P3HT), poly (3,4) -ethylene dioxythiophene, polystyrene sulfonate (PEDOT: PSS) on Si substrate. Transitional metal oxide component will be created in the form of nanoscale amorphous films and/or nanoparticles by laser deposition and chemical synthesis respectively. The combination of silicon with a layered system of organometallic compounds will make it possible to obtain a new multifunctional structure for solar energy converters. Additional function of the proposed converter is collecting and storing energy by supercapacitors. The concept of energy storage is based on the combination of iron oxide with carbon nanomaterials.

Authors : Gopa Sadar
Affiliations : India

Resume : A blue light-emitting conjugated polymer, namely aryl-polyfluorene (aryl-F8), having a high neat-film photoluminescence quantum yield (73%) and radiative decay rate (2 × 109 s-1) is reported. Excimer emission from the polymer is significantly reduced in its neat film unlike many other wide band-gap blue-emitters achieved as a result of the bulky aryl groups attached in the polymer chain. Amplified spontaneous emission (ASE) under optical excitation is observed in pristine film at an excitation fluence, Eth ~ 3 μJ cm-2, which is one of the lowest among polymer-based optical gain media in this spectral range, reported so far. The well-separated spectra of stimulated emission and long-lived triplet absorption and very low triplet yields explain the achievement of a low ASE threshold. Under electrical excitation, no singlet-triplet annihilation (STA) is detected in the light-emitting diode (LED) fabricated with this polymer in a hybrid structure. Thus, aryl-F8 emerges as an attractive optical gain medium for lasing application.

Authors : Kashimul Hossain, Shivam Singh*, Dinesh Kabra*
Affiliations : Department of Physics, Indian Institute of Technology Bombay, Mumbai, India 400076

Resume : Perovskite solar cells (PSCs) are the fastest growing photovoltaic devices in the solar cells community and offer a bright future for cheap solar electricity. In the last few years, it has been observed that the efficiency and stability of the PSCs can be enhanced by introducing multi cations into the perovskite crystal structure. Herein, we have examined the triple monovalent cation-based PSC (FA0.83MA0.17)0.95 Cs0.05Pb(I0.90Br0.10)3 (CsFAMA) over single monovalent cation based PSC MAPbI3 (MAPI) through frequency-dependent photo-current and dielectric measurements in terms of the dielectric relaxation process. The dielectric relaxation time constant (τd) is lower for the CsFAMA based PSC as compared to the MAPI based PSC. The lower τd is attributed to lower defect density in the CsFAMA based PSCs. Unprecedentedly, the relaxation process is correlated with the presence of monovalent cation of CsFAMA vs MAPI as an absorber in PSCs, which is well correlated with the presence of relative defect density. Our study suggests that τd is higher for higher defect density semiconductors in PSCs. Further, defects formation under illumination conditions reduces JSC as major in the case of MAPI, however, it is relatively insignificant in CsFAMA based PSCs and can be hypothesized based on relative ion density accumulation at the interface of charge extracting contact. This study provides a unique in-depth knowledge towards the role of monovalent cation in the dielectric relaxation process and their connection with the defects and thermal stability of halide perovskite semiconductors-based solar cells.

Authors : Romualdas Jonas Čepas*(1), Egidijus Kamarauskas (1), Kristijonas Genevičius (1), Aistė Jegorovė (2)
Affiliations : (1) Institute of Chemical Physics, Vilnius University, Saulėtekio al. 3, Vilnius 10257, Lithuania (2) Department of Organic Chemistry, Kaunas University of Technology, Radvilenu pl. 19, Kaunas 50254, Lithuania

Resume : Organic materials gained a lot of attention as promising materials for solar cells, field-effect transistors and detectors, due to their solution processability and tunable optoelectronic properties by chemical structure modification. Although organic materials suffer from instability under ambient conditions, various techniques are used to improve chemical stability and mechanical strength. One of the promising methods is cross-linking. Cross-linkable materials possess solvent/heat/ resistance, high hydrophobicity, mechanical durability and excellent film-processing ability [1, 2, 3]. At the same time cross-linking can affect material properties such as charge transfer, charge mobility, energetic and spatial disorders. In this work novel cross-linkable hole transporting materials containing vinyl groups were investigated. Temperature-dependent measurements of mobility were made in room and below ambient temperatures using the time-of-flight (TOF) technique. Herein we present, how cross-linking affects charge carrier mobilities, spatial and energetic disorder in crosslinked and non-crosslinked thin films made from investigated compounds. References 1. X. Sun, X. Deng, Z. Li, B. Xiong, C. Zhong, Z. Zhu, Z. Li, A. K.-Y. Jen, Advanced Science 2020, 7, 13 1903331. 2. Z. Li, Z. Zhu, C.-C. Chueh, J. Luo, A. K.-Y. Jen, Advanced Energy Materials 2016, 6, 21 1601165. 3. J. Wu, M. Hu, L. zhang, G. Song, Y. Li, W. Tan, Y. Tian, B. Xu, Chemical Engineering Journal 2021, 422 130124.

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Light harvesting : Joe Briscoe
Authors : Marina Freitag
Affiliations : School of Natural and Enviromental Sciences, Newcastle University

Resume : By 2025 about 75 billion IoT devices will be installed, of which the majority will reside indoors. It is therefore crucial to find an energy source that yields high efficiencies in this environment.[1,2] At high efficiencies under ambient light, while being more environmentally friendly, sustainable to produce and to recycle. Dye-sensitized solar cells (DSCs) are known for efficient conversion of ambient light. Fast charge separation in a variety of organic dyes and tuneable energy levels in CuII/I redox systems combined with negligible recombination processes allow DSCs to maintain a high photovoltage under ambient light [1,3,4] We tailored dye-sensitized photovoltaic cells based on a copper (II/I) coordination complexes hole transport material for power generation under ambient lighting with an unprecedented conversion efficiency of PCE 38 %, at 1000 lux from a fluorescent lamp using a novel co-sensitization strategy [2] and electrolyte modifications. Under 1000 lux lighting, 64 cm^2 photovoltaic area gives 152 J or 4.41 10^20 photons sufficient energy for training and testing of an artificial neural network in less than 24 hours. Ambient light harvesters enable a new generation of self-powered and "smart" IoT device to be powered by a previously untapped energy source. 1. Muñoz-García, A. B. et al. Dye-sensitized solar cells strike back. Chemical Society Reviews 50, 12450–12550 (2021). 2. Michaels, H. et al. Dye-sensitized solar cells under ambient light powering machine learning: towards autonomous smart sensors for the internet of things. Chemical Science 11, 2895–2906 (2020). 3. Freitag, M. et al. Dye-sensitized solar cells for efficient power generation under ambient lighting. Nature Photonics 11, 372–378 (2017). 4. Michaels, H., Benesperi, I. & Freitag, M. Challenges and prospects of ambient hybrid solar cell applications. Chemical Science (2021) doi:10.1039/D0SC06477G.

Authors : Rituraj Sharma, Matan Menahem, Zhenbang Dai, Lingyuan Gao, Roman Korobko, Omer Yaffe and Andrew Rappe
Affiliations : Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel; Department of Chemistry, University of Pennsylvania, Philadelphia, USA

Resume : Halide perovskites (HPs) are known to have strongly coupled electronic and structural dynamics. The thermally induced, low-energy structural fluctuations create a strong scattering of charge carriers and thus affect their optoelectronic properties. However, the microscopic nature and origin of the complex structural dynamics within the crystal have been elusive. Using low-frequency Raman measurements with polarized light, we have investigated the symmetries of low-frequency lattice modes in the orthorhombic phase of methylammonium lead iodide (CH3NH3PbI3, MAPI). Combining temperature evolution of Raman scattering with ab-initio molecular dynamics, we show that such atomic motions are dominated by temperature-activated liquid-like relaxational motion of the PbI6 octahedra and MA molecules in the higher temperature tetragonal and cubic phases. The continuous damping and all-axis unlocking of PbI6 octahedral modes correlate well with the soft mode-like character of the observed Raman features. Our results indicate that the strongly anharmonic liquid-like relaxational motions observed in HPs cannot be explained by the standard harmonic phonon picture.

Authors : Kalsoom Fatima, Zareen Akhter, Muhammad Sultan, Lukas Schmidt- Mende, Joe Briscoe
Affiliations : Kalsoom Fatima 1,4; Zareen Akhter 1; Muhammad Sultan 2; Lukas Schmidt- Mende 3; Joe Briscoe 4 1. Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad, Pakistan 2. Department of Physics, Kohsar University Murree, 47150 Punjab, Pakistan 3. Department of Physics, University of Konstanz, D-78457, Konstanz, Germany 4. School of Engineering and Materials Science, Queen Mary University of London, UK.

Resume : The various imperfections in perovskite absorbers and their interfaces greatly reduce the efficiency and stability of perovskite solar cells (PSCs). Surface passivation is an efficient approach to cope with these problems. Herein, we use the defect post-passivating method to improve the performance of inverted device having architecture of ITO/NiOX/Perovskite/EDA/C60/LiF/Cu. The amine based passivated material ethylene diamine (EDA) is selected to passivate the CsPbI2Br films via bonding between uncoordinated lead atoms in CsPbI2Br and the nitrogen atoms in the EDA molecule. The EDA passivation layer improves the photoelectric properties by significantly reducing the surface trap density and induces a shift in the energy band edge of the CsPbI2Br layer leading to efficient hole transfer at the CsPbI2Br/HTL interface. All these factors lead to increase in efficiency of solar cell from 7.3% to 9.4%. The work provides an effective strategy to fabricate efficient and stable CsPbI2Br PSCs.

Authors : Soumen Kundu , Sushobhan Avasthi
Affiliations : Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, Karnataka – 560012, India

Resume : There is a need to search for high efficiency Pb-free metal halide perovskites. Here we report a novel organic cation (Acetamidinium) for substituted formamidimium tin iodide perovskite. Using the acetamidinium-substituted formamidinium tin perovkite as the absorber, we demonstrate solar cells in the p-i-n configuration. The best device exhibited a power conversion efficiency ≈ 1%; with a short-circuit current density (Jsc) of 8.53 mA/cm2,open circuit-voltage (Voc) of 0.3V, and fill-factor (FF) of 39%. Poor Voc of the device is due to conduction band offset of absorber layer with PCBM and interfacial recombination.

Authors : Atif Suhail, Gunadeep Teron, Monojit Bag
Affiliations : Advanced Research in Electrochemical Impedance Spectroscopy Laboratory, Indian Institute of Technology Roorkee, Roorkee 247667, India

Resume : Highly fluorescent Cesium Lead-based (CsPbX3, X=Br, Cl, I) inorganic metal halide semiconductor perovskites have gained immense popularity in the last decade due to the economic and straightforward fabrication techniques involved in these materials along with their excellent electrical and optoelectronic properties. Cesium lead halide nanocrystals are well known for their fluorescence in the visible region with extremely high quantum efficiencies (as high as 90%) thus making them highly suitable for commercialization as materials for the fabrication of efficient light-emitting diodes. Such desirable properties encouraged the researchers to study as well as improve the optoelectronic performance of these materials for their application in highly efficient photovoltaic cells, photodetectors, light-emitting devices, transistors, and perovskite Light Emitting Diodes (PeLEDs). Although quantum dots are more fluorescent compared to their bulk counterpart, there have been very few reports on the synthesis and characterization of CsPbX3 perovskite quantum dots. In this work, we have synthesized and investigated the CsPbX3 quantum dots to understand the fundamental optoelectronic properties and structural integrity. We have estimated ~10 nm average particle size of CsPbBr3 nanocrystals from high-resolution transmission electron microscopy (HRTEM) while CsPbBr2I has ~16 nm average particle size with high polydispersity. CsPbBr3 nanocrystals are relatively more stable than the mixed halide perovskite nanocrystals due to fewer defects. Anomalous behavior is observed in the PL intensity with the variation in particle concentration indicating a complex nature in these systems. Keywords: Perovskite nanocrystals, CsPbX3, PeLEDs

10:30 coffee break    
Authors : Harsh Bhatia, Christopher Savory, David Scanlon, Robert Palgrave, Bob C. Schroeder
Affiliations : University College London

Resume : Bismuth based materials especially perovskites have found huge applications in the field of photovoltaics and photocatalysts. On the other side, the fundamental photophysical properties of coordination complexes of bismuth (III) have not been studied extensively. The complexes of transition metal atoms like Fe, Ru, Pd, Pt, Cu, Au, Ag, Os, Zn have been the focus of the scientific community for decades to harness solar light. These transition metal-based complexes are well explored and have been commercialized, however, many of these metal atoms are highly expensive, toxic, and suffer from various other problems. Due to these reasons a non-toxic and easily available substitute is required to overcome the needs of the present time. Therefore, to overcome these issues, herein we report a series phenanthroline substituted complexes of BiCl3, BiBr3 and BiI3. The complexes of different coordination number (6, 7 and bioctahedron) are synthesized and characterized using various spectroscopic tools. All the complexes vary by different number of halogen(s) and ligands bound to bismuth (III) centre, hence affecting the photophysical properties of the complexes. In this work we present the design strategy to synthesize novel bismuth (Bi) coordination complexes and studied their photophysical properties to understand their applications for the solar light absorption. We developed the complexes with different coordination bonds and varying electronic density along the bismuth atom. The molecular packing of the complexes was compared with the 3D packing of the perovskites. Moreover, the photophysical properties of the complexes were found to vary by changing the coordination geometry of the complexes as well as the electronic density of the ligand. The detailed ground and excited state photophysical studies along with theoretical analysis provide the information that one coordination geometry leads to strong absorption of visible light, hence favor application in photovoltaics while a different molecular geometry leads to the strong phosphorescence emission. The combined comparative studies illustrate a design principle to develop novel bismuth coordination complexes which can be used to harness the solar light efficiently.

Authors : Benjamín Pusay, Rosa Almache-Hernández, Kunal Tiwari, Eloi Ros, Alex Jimenez, Gerard Mastmitja, Isidro Martín, Cristóbal Voz, Joaquim Puigdollers, Edgardo Saucedo, Pablo Ortega
Affiliations : Departament d?Énginyeria Electrónica, Universitat Politécnica de Catalunya, Barcelona, Spain; Catalonia Institute for Energy (IREC), Barcelona, Spain

Resume : Nowadays, kesterite (Cu2ZnSn4/S4) has become an attractive material in photovoltaics as an alternative to indium and gallium-based CIGS solar cells. The certificated record efficiency for kesterite solar cells is 12.6% using CdS/ZnO/ITO and MoSe/Mo stacks as front and rear contact schemes, respectively. The industrial implementation of this photovoltaic technology requires the use of non-toxic and environmentally friendly materials. In this scenario, Cd-free solar cells become an important issue. In addition, the application of transparent selective contacts has become a challenge in thin-film photovoltaic technologies. These transparent contacts would open the door for its use in building-integrated photovoltaics or alternatively as a top cell in tandem solar cells. The Atomic Layer Deposition (ALD) technique is a technological and economically viable process for thin-film PV, allowing conformal and uniformly deposited layers on large-area devices. In this work, the implementation of fully ALD-based transparent electrodes for the front and back contacts for Kesterite solar cells is analyzed. The back contact is formed by a thin layer of V2O5 of about 10 nm as Hole Transport Layer deposited on an FTO/glass substrate. FTO has been chosen for its robustness and good stability at high temperatures. The thin V2O5 layer exhibits high transmittance and low light absorbance. The transmittance of the whole contact structure (V2O5/FTO/Glass) reaches 80% for the visible light range. The front contact is formed by a ZnO/PEI/AZO stack. Optical measurements of this contact corroborate a high transmittance and almost zero absorbance in the light visible range. Fabricated solar cells have not been exposed to any additional post-annealing stage. The EQE response of the best device confirms the high absorption in the UV-Vis spectrum range due to the transparent front contact, reaching a remarkably Jsc of 35 mA/cm2 illuminating by the front side. Curiously, a noticeable Jsc value of 5 mA/cm2 is achieved if the cell is illuminated by the rear side, obtaining a true bifacial solar cell by taking profit of both transparent electrodes. It is also important to remark the relatively high EQE response in the 800-1000 nm range, compared with conventional kesterite solar cells. These latest results confirm both the good quality of the absorber layer and an improvement of surface passivation in the V2O5-based contact layer. With an open-circuit voltage Voc of 250 mV, an improvement in the efficiency of up to 1.2% is achieved in our devices in comparison with a counterpart using a standard CdS-based ETL approach. The impact of the ALD temperature during deposition of the transparent electrodes, as well as the role of the PEI interlayer dipole in the device performance will be presented at the conference.

Authors : Juneja, N. (1), Mandati, S. (1), Katerski, A. (1), Spalatu, N. (1), Daskeviciute-Geguziene, S. (2), Vembris, A. (3), Getautis, V. (2), Karazhanov, S. (4), Krunks, M. (1), and Oja Acik, I. (1)
Affiliations : 1. Laboratory of Thin Film Chemical Technologies, TalTech, 19086 Tallinn, Estonia 2. Department of Organic Chemistry, Kaunas University of Technology, 50254 Kaunas, Lithuania 3. Institute of Solid State Physics, University of Latvia, Kengaraga Str. 8, Riga, Latvia 4. Institute for Energy Technology (IFE), P.O Box 40, NO 2027, Kjeller, Norway.

Resume : Antimony sulphide (Sb2S3) is a promising candidate for semi-transparent solar cells because of its appropriate optoelectronic properties [1]. Their applications are limited due to low-efficiency and expensive hole transport materials (HTMs) [2]. In this study, we have tested a series of HTMs – V808, V1385, V1386 and V1236 as an alternative to conventionally used HTM – P3HT. These novel HTMs are being investigated for the first time in Sb2S3 solar cells. Unlike P3HT, they are significantly cheaper, optically transparent, and do not require high temperature activation. The solar cells are fabricated in glass/FTO/TiO2/Sb2S3/HTM/Au configurations, with TiO2 and Sb2S3 deposited with ultrasonic spray pyrolysis. The as deposited Sb2S3 are then annealed in N2 at 260 oC for 5 minutes. Following that, spin coating is employed to deposit all the HTMs. Thermal evaporation is then used to deposit the Au contacts. The morphological and opto-electronic properties of the fabricated solar cells are analyzed using SEM, UV-visible spectrophotometer, JV and External Quantum Efficiency (EQE) measurements. Further, the impact of concentration variations of HTM solutions on the performance of Sb2S3 devices has been studied. The solar cells with fluorene unit linked HTMs have yielded higher conversion efficiencies than solar cells fabricated using P3HT. Furthermore, as compared to P3HT devices, the transparency of the solar cell stack with novel HTMs is enhanced by over 20% while yielding greater PCEs. The study demonstrates the successful fabrication of solar cells with cost-efficient novel fluorene-based HTMs in Sb2S3 solar cells for semi-transparent applications. References 1. Versavel M.Y, et al. 2007, Thin Solid Films, 515(18):7171-71762 2. Messina S, et al. 2007, Thin Solid Films, 515(15):5777-5782

Authors : Lidia Contreras-Bernal, Javier Castillo-Seoane, Jorge Gil-Rostra, Juan Antonio Anta, Ángel Barranco, Juan Ramón Sánchez-Valencia, Ana Borrás
Affiliations : Institute of Materials Science of Seville, (Spanish National Research Council (CSIC) – Univ. Seville), Seville, Spain: Lidia Contreras-Bernal;Javier Castillo-Seoane; Jorge Gil-Rostra; Ángel Barranco; Juan Ramón Sánchez-Valencia; Ana Borrás. Department of Physical, Chemical and Natural Systems, (Univ. Pablo de Olavide), Sevilla, Spain: Juan Antonio Anta

Resume : The worldwide increasing number of electronic devices working at the same time suppose a huge demand for on-site power that cannot be supplied by conventional batteries. So, the development of environmental energy harvesters is critical to prompt the self-powered actuation of small, portable-wearable, and wireless electronic devices. In this context, the nanogenerators arise as efficient nanoelectrodes that avoid energy losses and enhance multifunctionality. The nanoscale design of conductive and transparent materials for these nanoelectrodes is a crucial step for different applications that include optoelectronics and photovoltaics devices energy harvesters. One of the main interests in this direction is the use of new transparent conducting nanoelectrodes consisting of a wide range of materials with different compositions and texturing such as metal nanowires networks, carbon nanotubes, graphene, transparent conducting oxides (TCOs) nanostructures, etc. In this work, we have synthesized 1-dimensional (1D) and hierarchical Indium Tin Oxide (ITO) nanoelectrodes by a soft-template multistep method that combines vacuum and plasma techniques in a “one-reactor/chamber” configuration, i.e., every step of this procedure is developed in the same vacuum chamber combining several deposition methods. [1] Here, we combined magnetron sputtering (MS) and thermal evaporation, two industrially spread deposition techniques. In particular, we have synthesized high-quality ITO nanotubes and nanotrees with resistivities on single-nanotube comparable with single-crystal nanowires reported by other authors. These nanoelectrodes present desirable optical properties in the visible spectra for enhancing the light trapping in energy harvesting applications. The implementation of these nanostructures in Dye-Sensitized Solar Cells (DSSCs) was carried out following a standard architecture of a photovoltaic device. The photoanode was prepared in two steps to cover the ITO nanostructures with anatase-TiO2: 1) a conformal shell by Plasma Enhanced Chemical Vapor Deposition (PECVD) for then 2) embedding in a mesoporous matrix by screen-printing. Finally, the multilayered system was sensitized with the standard N719 dye and assembled to the counter-electrode. We used the iodide/triiodide pair in acetonitrile as the electrolyte. The main results of this study are the development of optically active ITO@TiO2 nanoelectrodes (1D and hierarchical systems) using a vacuum and plasma “one-reactor” configuration and their implementation in a DSSC with remarkable efficiencies obtained for indoor light applications. References: [1] Castillo-Seoane J., et al. Nanoscale 2021, 13, 13882-13895

Authors : I.Markevich1), N.Korsunska1), N.Stara1), I.Vorona1), O.Melnichuk2), L.Khomenkova1,3)
Affiliations : 1) V. Lashkaryov Institute of Semiconductor Physics, 45 Pr.Nauky, 03028 Kyiv, Ukraine; 2) Nizhyn Gogol State University, 2 Grafska str., 16600 Nizhyn, Ukraine; 3) National University of Kyiv-Mohyla Academy, 2 Skovorody str., 04070 Kyiv, Ukraine.

Resume : In ZnO:Mn ceramics, the correlation between Mn-related extrinsic photosensitivity and intrinsic one was revealed. The samples were prepared by sintering for 3 hours in air at 1100oC. Photoluminescence, photoconductivity (PC) and diffuse reflectance spectra were measured at room temperature. The concentration of the centres of photosensitivity (sensitizing centres - SC) responsible for the intrinsic PC was varied by co-doping of ZnO:Mn with Li or Cu. It was found that the formation of LiZn SC resulted in the enhancement of both intrinsic and Mn-related PC, while the decrease of SC concentration due to Cu co-doping caused a drastic reduction of the photosensitivity in the whole investigated spectral region. At the same time, as diffused reflectance spectra showed, the photo-ionization of MnZn2 centres took place in ZnO:Mn:Cu samples as well as in ZnO:Mn and ZnO:Mn:Li ones. Obtained results have confirmed the previous supposition on the interaction of MnZn2 centres with SC that are zinc vacancies in ZnO:Mn samples and LiZn acceptors in ZnO:Li ones. As a result of such an interaction, the transfer of photo-ionized hole from MnZn3 ion to SC and following recombination of photo-ionized electron on the latter take place.

Authors : Gabriella Rossi, Antonio D'Angelo, Claudia Diletto, Salvatore Esposito, Antonio Guglielmo, Michela Lanchi
Affiliations : ENEA - Italian National Agency for New Technologies, Energy and Sustainable Economic Development - Department for Energy Technologies and Renewable Energy Sources

Resume : The current European framework with the evolving conflict scenario urges cost-effective solutions to reduce dependence on fossil fuels, to be replaced by renewable sources. From this perspective, an attractive candidate is represented by concentrated solar power (CSP), a technology that uses large sun-tracking reflective surfaces to concentrate the direct solar radiation on a focal spot where a heat transfer fluid absorbs the radiation as high temperature heat, subsequently provided on demand for thermal and/or electrical applications. In CSP linear collector plants (Parabolic Trough Collector PTC and Linear Fresnel Collector LFC), receiver tube represents a key component with a high technological content. In particular, spectrally selective coating deposited on stainless steel tube is a strategic element due to its significant impact on the overall solar plant efficiency. These coatings work in absence of atmosphere (vacuum receivers) to limit thermal losses and protect their metallic components from oxidation processes. Presently, this technology, able to operate at temperature not exceeding 550°C, guarantees the maximum photo-thermal efficiency. However, in air receiver tubes to be employed in CSP linear collector plants operating at low temperatures (? 300 °C) or able to achieve temperatures up to 800 °C, can be particularly useful in terms of reduction of receiver cost as well as of provision of simple and sturdy structural component. Moreover, the in air receiver tubes developed for temperature ? 550 °C could represent, at date, the only available technical solution for CSP linear collector plants operating at temperature ? 550 °C. Nevertheless, it is to be taken into consideration that at high temperatures and in presence of atmosphere, spectrally selective coatings undergo degradation processes undermining their optical properties and thermal stability. In this regard, our work proposes an approach to go beyond these drawbacks by achieving satisfactory optical properties and thermal stability for coating in air at temperature higher than 550°C. The highly selective absorber coating, conceived to work in air and developed through industrially scalable route, is deposited on a AISI 321 stainless steel and composed by a first self-passivating alloy deposited by sputtering technique, on which two antireflective layers based on ceramic oxides are subsequently deposited through reactive sputtering and sol-gel methods. The ?as-deposited? coating exhibits good photo-thermal properties in terms of solar absorptance, which is higher than 0.78, and thermal emittance equal to 0.18 at 600 °C. Besides, a good thermal stability is demonstrated up to 600 °C in air condition, with absorptance of 0.71 and satisfactory low value emittance of 0.18 after 464 hours in air at 600 °C. These results pave the way for further developments expected to provide a contribution to replace fossil fuels in the next future in many relevant economic sectors.

13:00 Lunch Break    
Self-powered devices and Thermoelectric materials : Mariona Coll
Authors : Inkyu Park
Affiliations : KAIST Endowed Chair Professor of Mechanical Engineering, KAIST, South Korea

Resume : In the era of 4th industrial revolution, the importance of internet of things (IoT), which is the network of physical objects, has been rapidly growing. Among many core components for IoT, sensors measure physical parameters and status of objects including pressure, strain, temperature, pH, gas concentration, etc. As more sensors are deployed in numerous objects, especially in remote places, the power supply for the sensor operation is becoming a highly challenging issue. Accordingly, a number of low-power or self-powered sensors are being actively developed. In this talk, I will introduce recent development of self-powered physical and chemical sensors at our research group. In particular, the following research topics will be discussed: (1) wearable self-powered pressure sensor by integration of piezo-transmittance microporous elastomer with organic solar cell [1], (2) self-powered strain sensor based on the piezo-transmittance of a mechanical metamaterial [2], (3) self-powered H2 gas sensor based on chemo-mechanically operating palladium-polymer nanograting film [3], (4) self-powered gas sensor based on a photovoltaic cell and a colorimetric film with hierarchical micro/nanostructures [4], and (5) self-powered humidity sensor using chitosan-based plasmonic metal-hydrogel-metal filters [5]. References [1] J. Choi, I. Park, et al., “Wearable self-powered pressure sensor by integration of piezo-transmittance microporous elastomer with organic solar cell”, Nano Energy 74, 104749 (2020) [2] J. Gu, I. Park, et al., “Self-powered strain sensor based on the piezo-transmittance of a mechanical metamaterial”, Nano Energy 89, 106447 (2021) [3] M.Seo, I.Park, et al., “Chemo-mechanically operating palladium-polymer nanograting film for self-powered H2 gas sensor”, ACS Nano 14, 12 (2020) [4] K.Kang, I.Park, et al., “Self-powered gas sensor based on a photovoltaic cell and a colorimetric film with hierarchical micro/nanostructures”, ACS Applied Materials & Interfaces 12, 35 (2020) [5] J. Jang, I. Park, et al., “Self-powered humidity sensor using chitosan-based plasmonic metal-hydrogel-metal filters”, Advanced Optical Materials 8, 1901932 (2020)

Authors : Divya Rawat, Juhi Pandey, Shriparna Mukherjee, Ramesh Chandra Malik, and Ajay Soni*
Affiliations : School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175075, India; School of Basic Sciences, Indian Institute of Technology Mandi, Mandi 175075, India; Interdisciplinary Center for Energy Research, Indian Institute of Science, Bangalore 560012, India; Thermoelectric Materials and Device Laboratory, Department of Physics, Indian Institute of Science, Banglore 560012, India.

Resume : Superionic Cu2-xTe compounds belong to a family of copper chalcogenides which are promising p-type thermoelectric (TE) materials. The layered structure and loosely bound metal cations in Cu2-xTe compounds provide a new mechanism of Phonon-Liquid-Electron-Crystal to achieve ultra-low thermal conductivity.[1] Additionally, the TE performance of Cu2-xTe compounds can be modulated by optimizing structural parameters, carrier concentration, and thermal conductivity (κ).[2] The vibrational properties of Cu2-xTe compounds play a very important role in achieving ultra-low thermal conductivity. [3] Our study on the vibrational properties of Cu1.25Te, Cu1.6Te, and Cu2Te, using temperature and laser power-dependent Raman studies, revealed complex structural and compositional transitions which can be categorized as Cu deficit and Cu rich classes. The presence of the CuTe phase is established by the dominant A1g mode ~ 133 cm-1. On the contrary, the Cu-rich Cu2Te phase demonstrates the structural transition from trigonal to orthorhombic and cubic phases above ~ 553 K.[4] Interestingly, the intensity of Raman modes having Raman shift greater than 100 cm-1 showed strong dependence on charge carriers because of strong plasmon-phonon coupling. References 1. Liu, H., et al., Copper ion liquid-like thermoelectrics. Nature Materials, 2012. 11(5): p. 422-425. 2. Mukherjee, S., et al., Investigation on the structure and thermoelectric properties of CuxTe binary compounds. Dalton Transactions, 2019. 48(3): p. 1040-1050. 3. Salmón-Gamboa, J.U., et al., Vibrational and electrical properties of Cu2−xTe films: experimental data and first-principle calculations. Scientific Reports, 2018. 8(1): p. 8093. 4. Pandey, J., et al., Raman Spectroscopy Study of Phonon Liquid Electron Crystal in Copper Deficient Superionic Thermoelectric Cu2–xTe. ACS Applied Energy Materials, 2020.

Authors : Ievgen Nedrygailov, Kamil Rahme, Scott Monaghan, Anjali Ashokan, Rupa Ranjani, Paul Hurley, Subhajit Biswas, Justin D. Holmes
Affiliations : School of Chemistry & Tyndall National Institute, University College Cork, Cork, Ireland; AMBER Centre, Environmental Research Institute, University College Cork, Ireland

Resume : Thermoelectric energy harvesting is a promising, environmentally friendly way to generate electricity that could lessen our dependence on fossil fuels and reduce the harmful emissions associated with their combustion. At present, the use of thermoelectricity is severely limited due to the low efficiency of converting low-grade waste heat into electricity, which is about 63% of the total unused thermal energy released into the environment [1]. Thus, the development of new methods for efficient thermoelectric power generation from waste heat is of great importance. In this presentation, we show that the efficient recovery of low-grade heat can be achieved in well-aligned nanochannels with electrically charged walls, based on the ionic thermoelectric effect. The nanochannels, with diameters of approximately 10 nm and lengths ranging from a few micrometers to several millimeters, are created by the two-stage anodisation of aluminium, the chemical treatment of natural wood and other methods. The charge density on the walls of the nanochannels can be increased through surface functionalisation with organic ligands, leading to the formation of overlapping electrical double layers (EDLs). These EDLs can act as ion filters in the presence of a temperature gradient across the nanochannels, allowing ions with a certain charge to move freely through the pores, resulting in the generation of thermopower. Such ionic thermoelectric converters can transform low-grade heat into electricity with thermopowers of up to 3 mV/K, using aqueous electrolytes such as NaCl and KCl, which is higher than that of conventional solid-state thermoelectric converters. By varying the geometric parameters of the nanochannels, e.g. the type and concentration of the electrolyte, surface charge density, higher thermopowers should be achievable in these systems. Ionic thermoelectric power converters therefore have the potential of becoming game changers in the field of thermoelectric power conversion. [1] K. Zeb et al., Renewable and Sustainable Energy Reviews, 2017, 75, 1142. [2] T. Li et al., Nature Materials, 2019, 18, 608

Authors : Carolina Duque Sierra[1], Jose Manuel Sojo Gordillo[1], Merce Pacios, Alex Morata[1], Albert Tarancón[1][2].
Affiliations : [1] Catalonia Institute for Energy Research (IREC), Jardins de Les Dones de Negre 1, Sant Adrià de Besòs, Barcelona, Spain [2] Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, Barcelona, Spain

Resume : The tremendous increase in energy demand and interest in expanding the internet of things (IoT) to build more sustainable cities and communities led to a much-needed boost in energy sources for low-power microelectronics. Thermoelectric (TE) materials present a versatile and environmentally beneficial option to harvest energy from ambient waste heat to power this transition. Moreover, thanks to nanostructurization, commonly poor TE materials (i.e., silicon) have remarkably enhanced their TE properties; this is the case for nanowires and Si-based fabrics made of nanotubes. Nonetheless, the scalability of Si-based nanostructured materials remains a challenge. Silicon alloys (SiGe and silicides) fibers were studied in the present work due to their easy integrability in the electronics industry, abundance, and low extraction environmental impact. Most importantly, the fabrication of TE nanotubes was up-scaled to large areas. The nanotubes were fabricated using an electrospun fiber template and chemical vapor deposition (CVD). Different strategies to improve Silicon-alloys performance as TE materials were explored to optimize their Figure of Merit zT =(S^2 σ)/κ. The thermal conductivity κ was tuned by fast thermal treatments and measured with Laser Flash; the Seebeck coefficient was modified by varying the ratio between silicon and the alloying elements. We have also studied the change of σ by controlling the material’s doping and the thickness of the nanostructures. Likewise, a complete morphological and compositional characterization was performed using electron microscopy techniques, EDX, and XRD. The suitability of electrospinning and CVD to fabricate TE materials were successfully accessed. Furthermore, the TE properties were investigated, and steps to optimal morphology and compositional conditions of the Si-alloy materials were found.

Authors : Mujeeb Ahmad, Khushboo Agarwal, Sergio Gonzalez Munoz, Abhishek Ghosh, O.V. Kolosov* and B.R. Mehta*
Affiliations : International Research Centre MagTop,Institute of Physics, Polish Academy of Science, Aleja Lotnikow 32/46,PL-02668 Warsaw, Poland

Resume : Efficient thermoelectric (TE) conversion of waste heat to usable energy is a holy grail promising to address major societal issues related to energy crisis and global heat management. For these to be economical, synthesis of a solid-state material with a high figure-of-merit ZT values is the key, with characterisation methods quantifying TE and heat transport properties being indispensable for guiding development of such materials. In the present study, we report a large enhancement of the TE power factor in Sb2Te3/MoS2 multilayer structures. Work function values based on the Kelvin probe force microscopy (KPFM) measurements clearly show the formation of a potential barrier at the interfaces, which is favourable for carrier energy filtering and phonon scattering. We also use a new approach to simultaneously experimentally determine the values of in-plane (kxy) and out-of-pane (kz) thermal conductivities for multilayer samples with characteristic layer thickness of few nanometres, essential for the quantification of the figure-of-merit, or ZT – the key parameter for the TE material. Combining simultaneous enhancement in the value of in-plane power factor (to 4.97 mWm-1K-2) and reduction of the in-plane value thermal conductivity (to 0.7 Wm-1K-1) for Sb2Te3/MoS2 multilayer sample led to high values of ZT of 2.08 at room temperature. The present study therefore sets the foundation for a new methodology of exploiting the properties of 2D/3D interfaces for development of novel fully viable thermoelectric materials.

15:30 coffee break    
Authors : Binbin Xin, Arnaud Le Febvrier, Lei Wang, Niclas Solin, Biplab Paul and Per Eklund
Affiliations : Binbin Xin, Arnaud Le Febvrier, and Per Eklund: Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden; Lei Wang, and Niclas Solin: Electronic and Photonic Materials Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden; Biplab Paul: Platit AG, Selzach, Switzerland

Resume : Flexible thermoelectrics is an emerging area of research, in particular for wearable applications. The electronic, thermal, and mechanical properties of thin films can be altered by porosity, but controllable engineering of the nanoporosity in layered crystalline inorganic materials such as Ca3Co4O9 remains a challenge. The formation mechanism and how to control porosity in materials with laminated crystal structures were researched. The key factors are Ca(OH)2, the bilayer thickness, and Ca elemental ratio in multilayers film to determine the formation of nanopores in textured Ca3Co4O9 film. The oriented nanopores formation in textured Ca3Co4O9 is driven by local epitaxy and strain relaxation between Ca(OH)2 and Co3O4 during annealing. The porosity and average pore size of Ca3Co4O9 films can be tuned by adjusting individual layer thickness in the multilayers. With decreasing Co content, the morphology of pure Ca3Co4O9 in the annealed films on mica change from a nanoporous continuous film morphology, via larger pores, to a discontinuous film of textured islands. The nanoporous Ca3Co4O9 films not only show a higher electrical conductivity of ~90 S cm-1 and a high Seebeck coefficient of ~135 μV K-1, but also a thermal conductivity as low as ~1 Wm-1 K-1. Moreover, the nanoporous Ca3Co4O9 films exhibit a greater mechanical compliance and resilience to bending than the bulk. The nanoporous Ca3Co4O9 films incorporating organic PEDOT:PSS fillers can form hybrid films and show high mechanical flexibility with only a slight decrease of the thermoelectric properties, with potential use in mechanically flexible energy-harvesting applications.

Authors : Jose Manuel Sojo Gordillo[1], Carolina Duque Sierra[1], Nerea Alayo[1], Marc Salleras[2], Denise Estrada[2], Luis Fonseca[2], Alex Morata[2], Albert Tarancón[2,3].
Affiliations : [1] Catalonia Institute for Energy Research (IREC), Jardins de Les Dones de Negre 1, 08930, Sant Adrià de Besòs, Barcelona, Spain [2] Institute of Microelectronics of Barcelona, IMB-CNM (CSIC), C/Til⋅lers s/n (Campus UAB), 08193, Bellaterra, Barcelona, Spain [3] Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, 08010, Barcelona, Spain

Resume : Currently employed materials in Thermoelectric Generators (TEGs) such as bismuth telluride or lead telluride are scarce, expensive, toxic, and environmentally harmful, relegating this technology to specific niches. However, in recent years, the thermoelectrics paradigm has changed mainly due to the introduction of low-dimensional materials. This miniaturization enabled the tailoring of some properties of materials, such as reducing thermal conductivity by phonon scattering. Consequently, materials previously discarded due to a large bulk thermal conductivity have gained significant interest. Semiconductor nanowires (NWs) – particularly Si and SiGe NWs – have demonstrated fascinating properties with application in a wide range of fields, including energy and information technologies. Despite this interest, a proper evaluation of the compositional, morphological, and thermoelectrical properties in such nanostructures still represents a significant challenge. Typically, the study of individual integrated NWs following the bottom-up approach faces two main issues. The first is the need for catalyst nanoparticle precursor deposition to grow them, usually performed by colloidal solution depositions. The randomness of this process dramatically hinders the precise allocation of the desired NW into the employed test microdevices. The second challenge relates to the different architectures of test microdevices devoted to measuring one nanomaterial property. These challenges often result in using different NW to measure each of the studied properties, being one of the primary sources of error in the characterization of NWs. This work presents the conceptual design, simulation, fabrication, and testing process of a micro-machined device for the complete evaluation of a single bottom-up integrated NW. In the exhibited design, the NWs can grow between multiple pairs of detachable cantilevers. This approach allows the user to select the most suitable sample among the available in the chip after the random deposition of the catalyst precursor and discard the rest. The design also incorporates micro-trenches, which, added to a diameter of 3 mm- enable the use of Transmission Electron Microscopy for detailed morphology analysis and compositional characterization techniques such as EELS and EDX. In the same architecture, electrical collectors and isolated heaters are available at both ends of the trenches for thermoelectrical measurements of the NW. Moreover, through micro-Raman measurements, thermal conductivity evaluation is improved thanks to the lack of substrate below the NW and the electrical and thermal access to the NW for in-operando analysis. Finally, the fabrication process is designed without anisotropic etching processes, allowing the chip to be fabricated in any crystallographic direction. The device presented here shows remarkable utility in the challenging thermoelectrical characterization of integrated nanostructures and the development of multiple devices such as thermoelectric generators.

Authors : Dawid Janas
Affiliations : Silesian University of Technology, Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Krzywoustego 4, 44-100 Gliwice

Resume : Carbon nanostructures such as carbon nanotubes or graphene are some of the most vigorously researched materials of the XXI century. Ever since it was discovered that they can facilitate many energy transformation processes, they have been envisioned as key elements of many technologies in this area. In particular, carbon nanotubes revealed a notable potential for harvesting waste heat and turning it into valuable electrical energy, capitalizing on the Seebeck effect. This contribution will display the application opportunities of carbon nanotubes for thermoelectrics. The impact of the carbon nanotube structure and chemical composition on the capabilities for the generation of thermoelectric power will be analyzed in detail. The presentation will illustrate how appropriate structure control and assembly greatly enhance the thermoelectric properties of carbon nanotubes. Purification, powerful doping, and seamless material processing gave rise to a substantial improvement in the electrical and thermoelectric parameters of carbon nanotube networks.

Authors : Hyeon-Ju Jang and Woong-Ryeol Yu
Affiliations : Department of Materials Science and Engineering, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea

Resume : Continuous carbon fiber-reinforced polymer composites are widely used in the aerospace, automobiles, and military fields due to their high tensile strength and light weight. In recent years, 3D printing has been emerged as a viable method to produce a continuous carbon fiber-reinforced plastic, in particular thermoplastic composite. In this study, we developed 3D printing process of continuous carbon fiber-reinforced shape memory polymer (cCF-SMP) that can produce free-standing structures without supports via frontal polymerization (FP). FP is a polymerization process in which monomer is converted into polymer by the heat of self-catalytic exothermic reactions without external energy supply. In the other hand, the degree of resin impregnation of carbon fibers should be increased to secure the physical properties of cCF-SMP. In this study, we aimed to improve the degree of impregnation through In situ pin-assisted printing head. Finally, a new printing system was developed and the printability of frontal polymer with continuous carbon fibers was investigated, focusing on the degree of impregnation of carbon fibers. Then, the shape memory performance of printed cCF-SMP including its mechanical properties was evaluated.

Authors : Cosimo Anichini,1 Sanjay B. Thorat,1 Stefano Bortolotti,1 and Francesco Bonaccorso1,2
Affiliations : 1. BeDimensional S.p.A., Via Lungotorrente Secca 30R, 16163 Genova, Italy 2. Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy

Resume : Reducing the carbon footprint of terrestrial and aerial transportation is key to tackle the issue linked with climate change. One of the most promising strategies to improve energy efficiency and reduce carbon emissions of cars, planes, and other transportation is devoted to the reduction of their total weight. Graphene-based polymer composites (GPCs) have demonstrated improved stiffness and toughness compared to their pristine polymers. [1] Thanks to their mechanical properties[2], the use of GPCs allows a physical reduction of the structural elements, and consequently a decrease of the weight. In addition, the GPCs show higher resistance to wear[1], which ultimately may lead to an increased lifespan of the components when compared to their pristine ones. However, car parts made by additive manufacturing (AF) of GPCs with enhanced performances have not been prototyped yet. In this view, we designed and produced graphene loaded thermoplastic polymer filaments for their use in AF. Polyamide12 (PA12) and polypropylene (PP) composites containing up to 25% wt. of few-layer graphene (FLG) and carbon black (CB) were produced by melt-compounding and extruded into filaments for the AF of fuel pipelines. The GPCs have shown an improvement in elastic modulus and strength up to ~200% and ~55%, respectively (PA12 containing 25% of FLG+CB) compared to the bare polymers. Furthermore, the GPSs exhibited also electrostatic discharge properties (electrical conductivity in the 10-4 -10-3 S/m range), as well as flame-retardant features. Therefore, the exploitation of GPCs filaments will produce light AF car components with added multifunctionalities.

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Processing of materials for electronics and energy : Anjana Devi
Authors : Mari Napari
Affiliations : School of Electronics and Computer Science, University of Southampton, United Kingdom

Resume : Harvesting energy from stray sources, also known as energy scavenging, provides sustainable energy supplies for low-power electronic devices. These energy scavenging technologies can utilize mechanical energy via piezoelectricity, thermal energy via thermo- and pyroelectricity, as well as stray radio frequency (RF) and magnetic fields. The miniaturization of the electronics means that the functional materials used to collect and convert the energy need to be in a form of high-quality thin films. Atomic layer deposition (ALD) has already become a critical thin film fabrication technique for microelectronics due to its unique ability to grow conformal thin films with superior uniformity. ALD is also a key technique in encapsulating devices and components, protecting them from environmental degradation. These encapsulation layers can have a dual purpose as surface passivation, enhancing the performance and lifetime of the devices. In recent years, there has been a significant interest in extending the potential of the ALD to functional materials for energy harvesting and scavenging. This has resulted in several reports of ALD-grown films with piezo-, thermo-, pyro-, and magnetoelectric properties. In this presentation I will review the current state-of-art of the use of ALD in the energy scavenging technologies, and focus specifically on the recent developments in the fabrication of the functional thin films for low-power device applications.

Authors : Naoufal BAHLAWANE
Affiliations : Luxembourg Institute of Science and Technology (LIST) Materials Research and Technology Department 28, Avenue des hauts-Fourneaux ; L-4362 Esch-sur-Alzette ; Luxembourg

Resume : Carbon nanotubes (CNT) are versatile building blocks for the design of nanocomposite coatings with appealing applications. The high specific surface area, light absorption, electrical and thermal conductivities of CNTs make them valuable for the solar-thermal and solar-chemical energy conversion. Addressing the integration challenges is, however, a prerequisite that continuously trigger the development of innovative approaches and chemistries for their synthesis and modification. A single-step CVD process is reported via the implementation of a catalyst-promoter dual approach for the thermal growth of CNTs at 330-500°C. Randomly oriented and vertically aligned CNTs could be achieved with distinguishable characteristics. While the as-prepared randomly oriented CNT carpets feature a super-hydrophilic behavior, the vertically aligned CNTs are super-hydrophobic. The optical properties of both films are clearly distinguishable, although both qualify as super-black coatings. Promoting the mechanical properties and tailoring the surface chemistry is readily assessable on the randomly oriented CNTs using ALD as a subsequent step in the CVD reactor. CNT/metal oxide, core/shell, structures with strong UV-Vis-IR absorption withstand accelerated aging under conditions relevant to the space qualification. The resulting super black coating reduce substantially the stray light in optical instruments destined to space applications. Further CNT nanoengineering is demonstrated using a core-shell structure involving a transparent conducting oxide (TCO) shell and strongly correlated oxides. Hereby, the coatings are advantageous for solar-thermal energy harvesting, including at elevated temperatures (up to 1000K in vacuum). The coated electrically conducting CNT core with a semiconducting metal oxide shell is a promising nanoengineering approach for the design of photoelectrochemical (PEC) water splitting electrodes. The approach enables a 5-fold increase of the film performance under sun illumination. The overall presented results evidence the pertinence of the hybrid CVD-ALD process for the deposition of nanostructures and their nanoengineering to fit the requirements of contrasting applications.

Authors : Xabier García-Casas1, Gloria P. Moreno1, Francisco J. Aparicio1,2*, Qinrong He3, Ali Ghaffarinejad1, Juan R. Sanchez-Valencia1, Joe Briscoe3, Angel Barranco1, Ana Borras1.
Affiliations : 1. Nanotechnology on Surfaces and Plasma Group (CSIC-US), Materials Science Institute of Seville (Consejo Superior de Investigaciones Científicas – Universidad de Sevilla), c/Americo Vespucio 49, 41092 Seville, Spain 2. Departamento de Física Aplicada I, Escuela Politecnica Superior, Universidad de Sevilla, c/ Virgen de Africa 7, E-41011 Seville. 3. School of Engineering and Material Science and Materials Research Institute, Queen Mary University of London, E1 4NS, London. *presenting author.

Resume : The synergy between semiconducting, photonic and piezoelectric properties makes ZnO one of the preferred and more studied materials for the development of advanced piezoelectric, piezotronic, and piezo-phototronic devices. However, the efficiency of these systems is limited by polarization screening effects induced by free charge carriers inside ZnO thin films and nanostructures. This effect can be mitigated by two different interface engineering approaches. On the one hand, oxygen plasma and thermal annealing treatments are effective ways to reduce the concentration of intrinsic oxygen vacancies. On the other hand, the incorporation of organic p-type semiconductor and dielectric layers at the interface between the piezoelectric oxide and the metal contact is used to boost the device performance, by limiting the injection of free carriers into the piezoelectric active layer. In our previous work, we demonstrated the fabrication of a hybrid piezo-triboelectric nanogenerator based on multishell Ag@ZnO microstructures deposited by combing vacuum deposition and plasma-enhanced chemical deposition (PECVD) methods.1 In this communication, we present the advantages of the application of a remote plasma-assisted vacuum deposition (RPAVD) method for the interface engineering of ZnO-based piezoelectric nanogenerators and UV piezo-phototronic detectors by the incorporation of functional organic layers. The RPAVD technique, developed in our laboratory, has been successfully applied for the fabrication of photonic films2 based on organic dyes and small functional molecules working as optical sensors,3 optical filters, tunable photoluminescence emitters, and lasing gain media;4 and now it is extended to piezoelectric based systems. Thus, this plasma method is used for the synthesis of nanocomposite layers from organic functional molecules such as adamantane (dielectric) and piezoelectric polymers such as PVDF, whereas Spiro-OMETAD (p-type semiconductor) layers were deposited by vacuum sublimation. The RPAVD synthesis is carried out by a solvent-less and room-temperature procedure at low power plasma activation in an ECR-MW (Electron Cyclotron Resonance – Microwave) reactor to avoid energetic species or UV radiation of the plasma to reach the substrate surface, which makes it fully compatible with delicate substrate materials. In this communication, we exploit this approach to a nearly all-in-vacuum fabrication of piezoelectric nanogenerators and UV photodetectors in combination with texturized ZnO thin films also fabricated by a plasma method (PECVD)5 and Au contacts deposited by thermal evaporation under vacuum. 1. Xabier Garcia-Casas et al., Nano Energy 91 (2022), 106673. 2. Francisco J. Aparicio et al., Advanced Materials 23 (2011), 761. 3. Francisco J. Aparicio et al., Sensors and Actuators B 228 (2016), 649. 4. Maria Alcaire et al., ACS Appl. Mater. Interfaces 9 (2017), 8948. 5. Jorge Budagosky et al., Plasma Processes and Polymers 19 (2022), 2270008

Authors : Ander Reizabal, Paula González, Senentxu Lanceros-Mendez, Paul Dalton
Affiliations : Phil and Penny Knight Campus for Accelerating Scientific Impact, University of Oregon, 1505 Franklin Boulevard, Eugene 97403, OR, USA BCMaterials, Basque Center for Materials, Applications and Nanostructures, Bldg. Martina Casiano, UPV/EHU Science Park, Barrio Sarriena s/n, 48940 Leioa, Spain Macromolecular Chemistry Research Group (LABQUIMAC), Dept. of Physical Chemistry. Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Spain

Resume : Melt electrowriting (MEW) is a electrohydrodynamic (EHD) 3D printing technology able to generate microfibers and precisely deposit them without using any solvent. This enables the printing of complex macrostructures, while controlling their micro features and micro behavior. In just a few years of development, the limits of MEW have been consistently pushed, allowing for growth in designs, features, and applications. Recently, the potential of MEW for the development of active structures has been demonstrated, opening a wide spectrum of possibilities for electronics miniaturization. However, there are still some limitations to overcome, as MEW requires high processing temperatures and the use of thermoplastics with high thermal stability. This hinders the processing of new materials and makes it difficult to expand the technology into new fields. To solve this, we recently develop a novel technique based on EHD processing of aqueous solutions, which conserve the potential for high-resolution microscale printing. In addition, it does not require complex components, avoids the use of toxic solvents, and simplifies the processing of new materials. By using a freezing collector and a highly viscous silk aqueous solutions, high-resolution microscale models for tissue regeneration were successfully printed by EHD 3D processing. The printed structures made by microfibers (30 µm) show excellent biological response, but also present micro channels inside which invite to explore their potentials for electronics miniaturization. In the present work, silk microfibers with variable electrical properties have been processed through aqueous EHD 3D printing. Silk gives the main physical-chemicals properties of fibers, and conductive fillers make possible the control of electrical behavior. Different fibers micro designs such as solid, porous, hollow, and core-shell, have been explored, with the final goal of develop 3D printed nanogenerators and harvesters. The scalability and adaptability of the technology, combined with the possibility of multi material printing, and the control of microfeatures bring the possibility for fully printed devices development. Further, materials biocompatibility and light weight makes the technology suitable for body integration and wearables development.

15:30 coffee break    
Authors : Lina Sun, Tatsuki Sasaki, Tsukasa Yoshida, Yoshiyuki Suzuri
Affiliations : Innovation Center for Organic Electronics (INOEL); Graduate School of Science and Engineering, Yamagata University, Japan

Resume : Photochemical conversion of metal-organic solution precursors to thin film using Vacuum ultraviolet (VUV) radiation at low temperature and at ambient pressure is a promising approach because it enables application of thus obtained thin films in a cost-efficient way for realization of large-area fabrication of flexible electronics. In this talk, we will present the recent developed room temperature solution processed functional thin films and their applications in optoelectronic devices. Photochemical solution-processed thin film encapsulation (TFE) with a seamless organic/inorganic multilayer in a structure of polydimethylsiloxane (PDMS)/SiOx/SiNy/SiOxNy with a built-in compositional gradient, has achieved a low water vapor transmission rate <10–5 g/m2/day stability, totally equal the level of conventional glass-cap encapsulation to an organic light emitting diodes (OLEDs); In addition, photochemical gel conversion of the precursor solution made of zinc acetate and monoethanolamine (MEA) followed by a short irradiation of VUV light, resulted in core-shell structure of ZnO nanocrystal thin films with violet to blue-green photoluminescence (PL). The color-tunable PL based on this unique mechanism appears to be both efficient and stable, enabling potential application in flexible thin-film optoelectronic devices.

Authors : Xuan Li, Stoichko Dimitrov
Affiliations : School of Physical and Chemical Sciences, Queen Mary University of London

Resume : Large area perovskite film deposition has been drawing a considerable amount of interest to achieve the commercialization of perovskite PV. Differing from conventional spin coating, scale-up methods require a different approach to achieve high-quality films. In spin coating, anti-solvent treatment is normally adopted to optimize perovskite film formation, but the reproducibility of this approach is notoriously poor due to errors such as injection timing, injection rate, alignment, and height variations. Here, we report an antisolvent bath approach which achieves large area high quality perovskite films deposited via slot-die coating with high reproducibility. A newly developed in-situ photoluminescence (PL) and transmittance analysis equipment were used to probe the kinetics of perovskite formation and optimize the antisolvent and the thermal annealing stages. For PL analysis, peak intensity, peak position and peak full width at half maximum were tracked and analyzed. Several antisolvents with a different miscibility to the host solvent (dimethylformamide and dimethyl sulfoxide) were chosen as candidates for the study. Diethyl ether showed better results with the highest peak intensity and slowest intensity increase rate. Similarly, the in-situ transmittance analysis showed that diethyl ether provides the most optimum drying kinetics leading to uniform and dense films, confirmed by scanning electron microscope analysis. Applying the new antisolvent approach to device fabrication in entirely ambient conditions produced a champion device (ITO/SnO2/MAPbI3/PTAA/Au) with 15.72% efficiency, 22.76 mA/cm2 short circuit current density, 1.04 V open circuit voltage and 0.67 fill factor. The antisolvent bath treatment proved successful for depositing large area high-quality perovskite films. Coupled with the in-situ analysis, it enables precise optimization of perovskite film deposition, which will be a benefit for industrial operations.

Authors : Pumza Mente, Rafa? Zbonikowski, Jan Paczesny
Affiliations : Institute of Physical Chemistry, Polish Academy of Science

Resume : Self-assembly is a simple and useful strategy for connecting small building blocks into complex structures. Electrostatic interactions have a more extended range than hydrophobic and hydrogen bonding interactions. Therefore, electrostatic assemblies can be formed by the attraction of particles far from each other. This study engineers hydrophobic surface flat nanoparticles of different shapes with ionic charges using charged ligands. The synthesized flat nanoparticles can self-assemble at the air-water interface using the Langmuir-Blodgett technique. The strategically positioned negative and positive charges control the electrostatic interactions that cause electrostatic hierarchical self-assembly of the nanoparticles into 2D systems with unique properties. The self-assembled 2D films are transferred to silicon substrates and characterized by Brewster-Angle microscope, SEM, and AFM. These assemblies have potential applications in bio-sensing, energy storage, information storage, catalysis, and photovoltaics. The dynamic self-assembly characteristics of the system will be explored by assembling responsive structures that will rearrange upon changes in temperature, pH, and pressure. This project is funded by NCN under OPUS grant 2019/35 / B / ST5 / 03229

Authors : Solbin Yun, Yeonsong Kim, and Woong-Ryeol Yu
Affiliations : Department of Materials Science and Engineering and Research Institute of Advnaced Materials (RIAM), Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744, Republic of KOREA

Resume : Shear stiffening effect is a unique phenomenon where mechanical properties are strengthened by increased external strain rates. Owing to the dynamic boron-oxygen dative bonds (B:O), intermolecular hydrogen bonds, and chain entanglement, poly(borodimethylsiloxane) based shear stiffening gel (SSG) exhibits a typical shear stiffening effect by phase transition; i.e., liquid-like state at no external force and solid-like state at external loading conditions. This SSG has a limitation in practical applications because it has liquid-like properties in natural state. To overcome this problem, this study was aimed to investigate a thin film that can be used into multi-layer structures where shock absorption properties are required in such as display materials, energy device, and body armors. SSG-based high functional composite films were fabricated using phase separation of UV-curable resins. Due to the hydrophilicity of SSG, pure SSG was self-assembled inside hydrophobic UV-curable resin layers, resulting in three-layered SSG film. Morphological and chemical characterization by scanning electron microscope and energy-dispersive X-ray spectroscopy confirmed that a pure SSG layer was formed in the middle of the three-layer film. The impact absorption behavior of SSG-based functional film was investigated, showing excellent shock absorption properties. In addition, this SSG-based composite film showed excellent flexibility, optical property, which are very useful for applications in displays.

Authors : Sanjee Lamsal1, Joao Garretto1, Srikanth Itapu2*, Frank X. Li1, Pedro Cortes3, Vamsi Borra1
Affiliations : 1 Electrical and Computer Engineering, Youngstown State University, Ohio, USA 2* Department of Electronics and Communication Engineering, Alliance University, Karnataka, India 3 Chemical Engineering, Youngstown State University, Ohio, USA

Resume : Implantable antennas have gained significant interest owing to their applications in medical implant technologies such as wireless sensors, stimulators, and others. However, the design is constrained by miniaturization, transmission path loss via the human body, regulatory requirements, and biocompatibility. For identifying small items of concern in biomedical applications, sufficient resolution across the thickness is required. The initial focus of implantable antenna research was on linear polarized antennas. Because of the antenna's invisibility within the human body, it proved impossible to properly detect the orientation of the implanted antenna. As a result, circular polarization (CP) is preferred for implantable antennas to establish effective and efficient communication [1]. The proposed antenna is printed using an aerosol jet printing technology, and offers advantages such as compact size, simplicity of manufacturing, a larger impedance spectrum, simple design, and high performance. On a flexible FR4 substrate, an asymmetric-fed Coupled Stripline (ACS) antenna with an impedance bandwidth of 2 GHz to 20 GHz is 3D-printed using aerosol jet printing technology. To ensure optimal antenna performance, the printing process precisely controls the placement, geometry, and thickness of the deposit. The simulations were carried out with Ansys high frequency structural simulator (HFSS) Electronics Desktop v.20, and the results were confirmed with the help of Keysight Vector Network Analyzer (VNA). References [1] L.-J. Xu, X. Jin, D. Hua, W.-J. Lu, and Z. Duan, “Realization of Circular Polarization and Gain Enhancement for Implantable Antenna”, doi: 10.1109/ACCESS.2019.2963744.

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Fabrication and characteriation of materials : Anjana Devi, Joe Briscoe
Authors : Wei-Chen Yang, Yan-Cheng Lin, Shin Inagaki, Hiroya Shimizu, Ender Ercan, Li-Che Hsu, Chu-Chen Chueh, Tomoya Higashihara,* and Wen-Chang Chen*
Affiliations : National Taiwan University-Department of Chemical Engineering (Taiwan) Wei-Chen Yang; Yan-Cheng Lin; Ender Ercan; Li-Che Hsu; Chu-Chen Chueh; Wen-Chang Chen* Yamagata University-Department of Organic Materials Science Graduate School of Organic Materials Science (Japan) Shin Inagaki; Hiroya Shimizu; Tomoya Higashihara*

Resume : Neuromorphic computation possesses the advantages of self-learning, highly parallel computation, and low energy consumption, and is of great promise to overcome the bottleneck of von Neumann computation. In this work, a series of poly(3-hexylthiophene) (P3HT)-based block copolymers (BCPs) with different coil segments, including polystyrene, poly(2-vinylpyridine) (P2VP), poly(2-vinylnaphthalene), and poly(butyl acrylate), are utilized in photosynaptic transistor to emulate paired-pulse facilitation, spike time/rate-dependent plasticity, short/long-term neuroplasticity, and learning−forgetting−relearning processes. P3HT serves as a carrier transport channel and a photogate, while the insulating coils with electrophilic groups are for charge trapping and preservation. Three main factors are unveiled to govern the properties of these P3HT-based BCPs: i) rigidity of the insulating coil, ii) energy levels between the constituent polymers, and iii) electrophilicity of the insulating coil. Accordingly, P3HT-b-P2VP-based photosynaptic transistor with a sought-after BCP combination demonstrates long-term memory behavior with current contrast up to 105, short-term memory behavior with high paired-pulse facilitation ratio of 1.38, and an ultralow energy consumption of 0.56 fJ at an operating voltage of −0.0003 V. As far as it is known, this is the first work to utilize conjugated BCPs in an electret-free photosynaptic transistor showing great potential to the artificial intelligence technology. (Published in Advanced Science, 2022)

Authors : Osvalds Verners (1), Linards Lap?inskis (2), L?va ??rmane (2), Aarne Kasikov (3), Martin Timusk (3), Amanda V. Ellis (4), Peter C. Sherrell (4), Andris ?utka (1)
Affiliations : 1 Institute of Materials and Surface Engineering, Faculty of Materials Science and Applied Chemistry, Riga Technical University; 2 Institute of Technical Physics, Faculty of Materials Science and Applied Chemistry, Riga Technical University; 3 Laboratory of Low Temperatures Structure, University of Tartu; 4 Department of Chemical Engineering, The University of Melbourne

Resume : Understanding contact electrification between chemically identical polymer surfaces is a key issue underlying general polymer triboelectrification. Developing models that can accurately predict surface change in these systems will enable the future design of highly efficient mechanical-to-electrical energy harvesting. Here, we present a combined experimental and computational approach to develop such a model of the contact electrification of chemically identical polymers, describing how the relative surface roughness influences surface charge. Experimentally, chemically identical polymer pairs show an increase in the surface charge when the difference in surface roughness is increased. More importantly, these results revealed that, in case of chemically identical polymer contact, the surface with a higher roughness as a rule will present a positive surface charge, and the lower roughness surface a negative charge. Computational results revealed a consistently lower strain for the rougher surfaces during contact-separation. Molecular dynamics simulations demonstrated the relationship between this strain (and hence roughness) with bond-scission and ionic material transfer. The energy needed for scission of strained chain is smaller, thus the material transfer should occur at a higher intensity from smooth to rough polymer. However, an opposite trend is observed for the desorption energies of free end fragments of polymers. Critically, a correlation between the direction of positive and negative charge fragment transfer is observed in the simulations, desorption energies, and bond-scission energies is observed in the simulations. If a chain is broken then the a negative charge will be transferred with a higher statistical probability due to smaller scission / desorption energy. Thereby, by choosing correctly which material in triboelectric nanogenerator (TENG) device should be rough and which should be smooth, it will be possible to increase performance of all types of TENG devices.

Authors : Nagasarvari Garikapati and P. Swaminathan
Affiliations : Garikapati Nagasarvari 1; P. Swaminathan 1, 2 1 Electronic Materials and Thin Films Lab, Department of Metallurgical and Materials Engineering, IIT Madras, Chennai, India 2 Ceramics Technologies Group-Centre of Excellence in Materials and Manufacturing for Futuristic Mobility, IIT Madras, Chennai, India

Resume : Flexible electronics has permeated diverse fields owing to its ease of fabrication, robustness, light weight, and cost effectiveness. Touch sensors are used in various areas such as biometric authentication and display devices. Among the plethora of touch sensing techniques adopted, capacitive sensing is popular owing to its high sensitivity, simple structure, thermal stability, and low power consumption [1]. Silver nanowires (AgNWs) have excellent electrical, optical, and mechanical properties and can withstand small bending radii and high strain without affecting the optoelectronic properties. They are thus a viable candidate for transparent flexible and foldable devices [1]. In this work, we fabricated a capacitive force sensor on a flexible polyethylene terephthalate (PET) substrate. The sensing circuit is printed using a custom-built direct writer using AgNW ink. Polydimethylsiloxane (PDMS), an elastomer, is used to encapsulate the device to provide it with mechanical stability as well as environmental protection. PDMS has a low surface energy and is well known for its flexibility, thermal stability, biocompatibility, transparency in the visible region, hydrophobicity, and chemical resistance [2, 3]. Moreover, PDMS can be spin coated directly on the device and cured below 150 ⁰C, which is compatible with many flexible substrates. The capacitance of the printed network varies with the thickness of the PDMS layer, which can be adjusted using the spin coating parameters. When metal oxide nanoparticles such as zinc oxide (ZnO) are added to the PDMS matrix, porosity in the polymer matrix tends to reduce and the barrier protection is increased. Moreover, ZnO possesses high hardness, low refractive index, and hydrophobicity [4]. Therefore, PDMS-ZnO is also used as an encapsulant in this work and the force response of the sensors with PDMS and PDMS-ZnO coatings is compared. The change in intrinsic capacitance on touch is sensed by an LCR meter and the applied force is measured as a function of the change in capacitance to calibrate the touch sensor as a force sensor. References [1] N. M. Nair, K. Daniel, S. C. Vadali, D. Ray, and P. Swaminathan, Flexible and Printed Electronics, 045001 (2019) [2] J.M. Han, J.W. Han, J.Y. Chun, C.H. Ok, and D.S. Seo, Japanese Journal of Applied Physics, 47, 8986-8988 (2008) [3] X. Cui, G. Zhu, Y. Pan, Q. Shao, C. (xinxin) Zhao, M. Dong, Y. Zhang, Z. Guo, Polymer, 138, 203-210 (2018) [4] Sh. Ammar, K. Ramesh, B. Vengadaesvaran, S. Ramesh, A.K. Arof, Progress in Organic Coatings, 92, 54-65 (2016)

Authors : Abhirup Das1, Samik Mallik2, Prof. D. K. Goswami1,2
Affiliations : 1Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur – 721302, India 2School of Nanoscience and Technology, Indian Institute of Technology Kharagpur, Kharagpur – 721302, India

Resume : XRR is a non-destructive method, used for evaluating the electron density, thickness, and surface roughness of a multilayer film composed of layered synthetic microstructures like as single crystalline, poly-crystalline, or amorphous material. Pentacene is a widely used organic semiconductor in the field of organic electronics due to its high field effect mobility. In this work, an XRR study has been carried out to extract the structural information and molecular arrangement of thin pentacene film grown on the silicon substrate. We have grown pentacene on the silicon substrate using organic molecular beam deposition system with chamber pressure ~ 1.5 x 10-6 mbar. Specular x-ray reflectivity measurements were performed using Rigaku Smartlab studio II x-ray diffractometer with CuKα (1.54 Ȧ) x-ray source of 9 kW energy. By using Parratt’s recursion formula we have given a theoretical model and we have compared the experimental reflectivity data with the modeled one. By performing 5x5 μm scan we have got rms roughness 2.9 nm of the pentacene film. We have divided the penatacene film into bulk phase and thin film phase and followed by fitted the Bragg peak. Based on the fitted parameters we have obtained an electron density profile, from which we have explained an idea about molecular arrangement of the pentacene thin film.

Authors : Santosh K. Tiwari
Affiliations : Faculty of Chemistry , University of Warsaw, Poland

Resume : This work consists of two parts; (I) synthesis of graphene, graphene oxide (GO), reduced graphene oxide (rGO) and (II) their application as nanofillers for the fabrication of polymer nanocomposites. In the present work, we have developed a green method for the production of graphene via electrochemical exfoliation without using hazardous chemicals. In this electrochemical approach we have used waste zinc-carbon batteries as a sourceof graphite. During the experiment we have found that 4.5 voltage is optimum for the exfoliation of graphene layers using the electrode (graphite electrode used in Zinc carbon batteries). This work also explored an efficient transformation for the graphene oxide to reduced graphene oxide. The developed reduction approach is time effective and can be used for the bulk production of the reduced graphene oxide. Different spectroscopic and morphological techniques were used to characterize physical and chemical properties of synthesized graphene and reduced graphene oxide. To test efficacy of graphene and their derivatives as nanofiller, we have used a set of compatible [Poly (carbonate): PC & Poly(methyl methacrylate): PMMA], partially compatible [PC &Poly[imino(1,6-dioxohexamethylene) iminohexamethylene]: Nylon 6,6) and incompatible polymers (PC & Poly(propene): PP) as polymer matrices. For the homogeneous dispersion of graphene oxide and reduced graphene oxide herein wehave applied a mixing sequence and different loading methodology. During the study it has been found that melt viscosity of blend components, covalent interaction,π-π interaction, dipole interaction, hydrogen bonding and other weak interactions plays a crucial role in defining selective migration and aggregation ofnanofillers. In the present work it has been pointed out that 0.5% and 1% loading of graphene oxide is optimum which results in maximum reinforcement for the compatible (PC/PMMA) and incompatible(PC/PP) polymerblends respectively. Similarly, in the case of mixing sequence the highest thermo-mechanical stability were noted in the case of PmGoPc for the compatible blend (mixing of PMMA first with graphene oxide and then PmGo mixed with PC)whereas for nanocomposites PPGoPc (mixing of polycarbonate first with graphene oxide and then PPGo mixed with polycarbonate ) in the incompatible polymer blends. The properties of these blend nanocomposites were tested using UTM (Universaltesting machine), DMA (Dynamic mechanical analysis), DSC (Differential scanning calorimetry), TGA (Thermogravimetric analysis), HRTEM,XRD and other techniques. In the last, we have also used graphene oxide nanosheets co-assisted with maleic anhydride grafted polypropylene to test thermo-mechanical properties aforesaid polymer nanocomposites .


Symposium organizers

Nanotechnology on Surfaces, c/ Américo Vespucio, 49, 41092 – Isla de la Cartuja, Sevilla, Spain

+34 954 48 95 92
Anjana DEVIRuhr- Universität Bochum

Universitätsstr. 150 - Building NC, Room 2/71 - 44801 Bochum, Germany

+49 234 3224150
Joe BRISCOEQueen Mary University of London

Engineering 113, Mile End Road, London E1 4NS, U.K.

+44 (0)20 7882 3552
Mariona COLLInstitute of Materials Science of Barcelona (ICMAB-CSIC)

Campus UAB 08193, Bellaterra, Barcelona, Spain