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2015 Fall

Materials and devices for energy and environment applications


Materials for energy storage and conversion

Scientists of different communities exploring the new possibilities for materials for energy storage & conversion through their investigation. Hence, there should be E-MRS symposium dedicated to the connection between theory and experiments including both academia and industry.


The prolific growth of energy demand all over the world can be procured by the renewable energy harvesting and storage. Various new materials promise great potential for helping to solve important technological challenges in energy efficiency, storage and the conversion of renewable and sustainable energy. However, performing experiments in the laboratory scale can be quite expensive to test wide range of materials and their properties, which paves the way of computer aided theoretical prediction. Thus materials modeling come into the picture of our daily scientific life. In this symposium, computational and experimental materials scientists working both in academia and industrial environment throughout the world can discuss profoundly the future of materials for energy applications. Leading world experts will provide the insights to the complex science of novel materials for energy applications which will motivate the young researchers in this field.

The proposed workshop aims at bringing together world-leading experts in all these fields to improve interdisciplinary cooperation and overcoming traditional boundaries between scientific disciplines, especially traditional fundamental research and the applied sciences..

The scientific objectives of the proposed workshop are:

  • Bring together researchers from materials science, chemical synthesis, hydrogen, catalysis, photo-catalysis, electro-catalysis, electrochemistry, fuel cells, supercapacitors, and photovoltaics to highlight recent progress and discuss challenges and opportunities in the research and development for energy applications.
  • To discuss possibilities for optimizing the materials properties and device design. The interdisciplinary character of the workshop will help finding solutions for overcoming current drawbacks.
  • Provide opportunity to form new worldwide interdisciplinary collaborations on nanostructured energy materials for the mutual benefit of theoretical, experimental and applied researchers.

Hot topics to be covered by the symposium:

According to the theme of our symposium, which is primly motivated by the fact of energy applications, the following area would be given:

  1. Solar-driven fuels: hydrogen and other organic fuels
  2. Hydrogen production and fuel generation
  3. Hydrogen storage
  4. Organic and Inorganic Solar Cell and Photovoltaic
  5. Hybrid Interfaces for the quest of novel energy efficient materials
  6. Supercapacitors
  7. Fuel cells
  8. Organic and Inorganic Battery Materials
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Authors : Chris G. Van de Walle
Affiliations : Materials Department, University of California, Santa Barbara, California, USA

Resume : First-principles studies of hydrogen interactions with storage materials provide direct insight into the processes of hydrogen uptake and release. The defects involved in kinetics of semiconducting or insulating storage materials are charged, and hence their formation energy is Fermi-level dependent and can be affected by the presence of impurities [1,2]. This provides an explanation for the role played by transition-metal impurities in the kinetics of NaAlH4, LiBH4, MgH2, etc. Desorption of hydrogen is accompanied by decomposition of the storage material and requires not only mass transport of H but also of host atoms. This process is mediated by native defects. We have investigated the structure, stability, and migration enthalpy of native defects based on density functional theory. The results allow us to propose specific mechanisms to explain the observed activation energies. We can also distinguish between formation of defects on the surface versus in the interior of the material, thus explaining the particle-size dependence of the activation energy for decomposition of lithium amide (LiNH2) [3]. Work performed in collaboration with K. Hoang, A. Janotti, A. Peles, and G. B. Wilson-Short. [1] A. Peles and C. G. Van de Walle, Phys. Rev. B 76, 214101 (2007). [2] G. B. Wilson-Short, A. Janotti, K. Hoang, A. Peles, and C. G. Van de Walle, Phys. Rev. B 80, 224102 (2009). [3] K. Hoang, A. Janotti, and C. G. Van de Walle, Angew. Chem. Int. Ed. 123, 10352 (2011).

Authors : Pedro Gómez-Romero
Affiliations : Institut Catala de Nanociencia i Nanotecnologia, ICN2 (CSIC-CERCA), 08193 Bellaterra (Barcelona) Spain.

Resume : If nanotechnology is an Enabling Technology, Energy Storage is also increasingly recognized as a key technology to enable our ongoing transition to a sustainable energy model. Electrochemical energy storage will be key to this transition but is still far from optimal. That is why there is still plenty of room for novel types of materials in this trade. Hybrid Nanocomposite Materials offer opportunities for synergy and improved properties. [1] Those formed by electroactive and conducting components are of particular interest for energy storage applications. [2, 5] We have developed a whole line of work dealing with hybrid electroactive and conductive materials for energy storage applications. In this conference we will address some of our recent work towards hybridizing energy storage discussing hybrid electrodes formed by nanocarbons and polyoxometalates or oxides. [3, 4] Furthermore, we will show how hybrids can be designed to take advantage of dual energy storage mechanisms by combining the typical capacitive behavior of supercapacitors with the characteristic faradaic activities of batteries. [5] [1] P. Gomez-Romero Adv.Mater. 2001, 13(3), 163. [2] P. Gomez-Romero et al. J.Solid State Electrochem. 2010 14(11), 1939 [3] V. Ruiz, J. Suárez-Guevara, P. Gomez-Romero Electrochem. Comm. 2012, 24, 35. [4] J. Suarez-Guevara, V. Ruiz and P. Gomez-Romero J.Mat.Chem.A, 2014, 2, 1014. [5] D.P. Dubal, V.Ruiz, O.Ayyad, P.Gomez-Romero Chem.Soc.Rev.2015 44(7):1777-90

Authors : Stephane NEUVILLE
Affiliations : TCE

Resume : Some outstanding properties of different type of carbon materials have started to be used for energy storage and conversion and can now be considered for decisive new improvements of many different devices. It is especially concerning electric battery capacity and power with optimized electrode materials, OLED encapsulating and different kinds of renewable energies such as solar cells antireflective encapsulating and tribology of wind/water mills gears. This is now expected to be easier achievable with in-depth comprehensive use of recent progress of corresponding fundamentals, allowing straightforward sorting out and optimization of all involved aspects especially concerning growth mechanisms, defects and structure identification with which carbon structures can now be produced and selected in practice and tailored upon requested property combination. Many solid state aspects are here involved: disorder and mix of different kind of carbon materials which will particularly affect work function, electric, electro-chemical, opto-electronic, and also optical, thermal, diffusion barrier and mechanical properties. We will describe these differentiated aspects and discuss some examples showing their importance on achievement of improved practical results.

Authors : Aparabal Kumar, P. Banerji
Affiliations : Materials Science Centre, Indian Institute of Technology Kharagpur, Kharagpur - 721302, West Bengal, India

Resume : Cu3SbSe4 is one of the thermoelectric materials synthesized with elements abundant in earth crust and shows promising thermoelectric properties above room temperature (300 - 650 K). Polycrystalline Cu3SbSe4 ingot with high phase purity was prepared with melt growth technique followed by spark plasma sintering (SPS) at 300 °C and 65 MPa for 5 min. The resultant samples were annealed in vacuum furnace at different sintering time to study the effect of grain growth on thermoelectric properties. Structural characterizations were performed to study the phase purity, crystal structure and crystallite size of the sample. Electrical and thermal transport properties were investigated from 300 to 600 K to study thermoelectric properties. Electrical transport properties were explained using single parabolic band model considering the acoustic phonon scattering approximation. It was found that the increase in annealing time leads to increase in electrical conductivity and effective mass. The electrical resistivity and thermal conductivity decrease monotonically with increase in temperature for all the samples. Thermopower represents that the major charge carriers are hole and contributed by Cu deficiency. Small decrease in its value above 550 K shows thermal excitation of charge carrier above that temperature.

Authors : Daniel I. Bilc 1-2, Geoffroy Hautier 3, David Waroquiers 3, Gian-Marco Rignanese 3, and Philippe Ghosez 1
Affiliations : 1 Département de Physique, Université de Liège, 4000 Liège, Belgium; 2 National Institute for Research & Development of Isotopic & Molecular Technologies, Ro-400293 Cluj-Napoca, Romania; 3 Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium

Resume : Thermoelectrics are promising to address energy issues but their exploitation is still hampered by low efficiencies. So far, much improvement has been achieved by reducing the thermal conductivity but less by maximizing the power factor. The latter imposes apparently conflicting requirements on the band structure: a narrow energy distribution and a low effective mass. Quantum confinement in nanostructures or the introduction of resonant states were suggested as possible solutions to this paradox but with limited success. We propose an original approach to fulfill the seemingly conflicting requirements within the same electronic band of certain bulk semiconductors. The approach exploits the highly-directional character of some orbitals to engineer the band structure and produce a type of low-dimensional transport similar to that targeted in nanostructures, while retaining isotropic properties [1]. Using first-principles calculations, the theoretical concept is demonstrated in Fe2YZ Heusler compounds, yielding power factors 4-5 times larger than in classical thermoelectrics. Our findings are totally generic and rationalize the search of alternative compounds with a similar behavior. Realizing such low-dimensional transport in bulk isotropic compounds is totally exotic and relevant also in the context of photovoltaic, electronic, or superconducting applications. 1. D. I. Bilc, G. Hautier, D. Waroquiers, G. M. Rignanese, and Ph. Ghosez, Phys. Rev. Lett. 114, 136601 (2015).

Authors : N.M. White, M. Burton, E. Koukharenko, I.Nandhakumar
Affiliations : University of Southampton

Resume : There is overwhelming evidence that our increasing consumption of fossil fuels and the associated emission of carbon dioxide is leading to climate change. This has brought new urgency to the development of clean, renewable sources of energy. Thermoelectric (TE) materials are an important class of materials that can directly convert thermal waste heat into useful electrical energy. With approximately 15 terawatts of available energy being lost to the environment as heat the potential for TE materials in sustainable waste-heat-recovery systems such as TE power generation is huge. However, barriers exist to the widespread adoption of TE technology which is due to the low efficiency of current TE materials. Clearly a step change in the cost and performance of TE materials is required to make them more economically viable and to promote their wider adoption in a number of application areas. In the current work we propose to achieve this by 1. employing electrodeposition as a low-cost, low-temperature route to the fabrication of highly efficient TE materials from, abundant, non-toxic and cheap materials and by employing soft-template directed nanostructuring to produce TE materials

Authors : Konstantin Glaser, Stefan Gärtner, Christian Sprau, Felix Nickel, Sivaramakrishnan Sankaran, Alexander Colsmann
Affiliations : Karlsruhe Institute of Technology (KIT), Lichttechnisches Institut, Engesserstrasse 13, 76131 Karlsruhe, Germany

Resume : The industrial fabrication of organic solar cells is often hampered by toxic solvents that require strong safety precautions. Whereas the use of chlorinated solvents or toxic hydrocarbons is feasible in the lab, their use in large scale printing processes would lead to enormous operational costs, which conflicts with the goal of cost effective production. In this work, we present efficient organic solar cells that were fabricated from non-halogenated solvents. To advance this concept and to enable device fabrication from non-toxic solvents, we synthesized organic solar cells entirely from aqueous and alcoholic solvents. For the absorber layer, we disperse, investigate and use P3HT:ICBA nanoparticles in environmentally friendly dispersion agents such as ethanol. In an inverted solar cell architecture with a nanoparticulate P3HT:ICBA layer the power conversion efficiency of 5% nearly matches the performance of reference devices that were fabricated from dichlorobenzene. We further demonstrate that this device fabrication concept is well suited for upscaling.

Authors : Chun-Guey Wu
Affiliations : National Central University

Resume : lanar heterojunction organic-perovskite hybrid solar cell is one of the most promising photovoltaic architecture to achieve high efficiency with low temperature process. A new two-step solution process to synthesis high quality perovskite film at room temperature was disclosed. Combining with smooth PEDOTLPSS hole transport layer and high mobility electron transport (PC71BM) layer, the planar heterojunction perovskite-PC71BM solar cell achieves the power conversion efficiency above 16%. This champion cell shows no current hysteresis both in voltage scan directions and rates.. The crystalline perovskite film was made by first spin-coating PbI2 film then adding CH3NH3I via spin-coating. The growth and purity of perovskite film can be manipulated individually, providing a simple and reproducible way to fabricate perovskite based solar cells via low temperature solution process in an ambient atmosphere

Authors : Simrjit Singh, Neeraj Khare
Affiliations : Nano Functional Oxide and Superconductivity Laboratory,Physics Department, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India.

Resume : Photoelectrochemical water splitting is an advanced chemical process for the generation of hydrogen (H2) using solar energy. Since the discovery of photoelectrochemical water splitting using TiO2 semiconductor, many metal oxide semiconductors have been extensively used as photoelectrodes for water splitting. However, due to the larger band gap of most of the oxide semiconductors, they use only UV light which is only 5 % of the solar spectrum incident on the earth’s surface. Therefore, for the generation of hydrogen on a larger scale, there is a need to develop visible light active photoanode materials for water splitting. Among visible light active semiconductor materials, CdS has attracted much attention due its optical band gap of 2.4 eV and has an optimal position of band edges for splitting of water into hydrogen. However, the phototelectrochemical activity of CdS is limited by various factors such as (i) CdS is unstable in aqueous solution and readily become deactivated through photocorrosion and (ii) high rate of charge carrier recombination. In order to address these limitations and improving the solar energy conversion efficiency of CdS, we have synthesized CdS/CoFe2O4 (CdS/CFO) core/shell nano heterostructure having a type-II band-edge alignment and coupled it with reduced graphene oxide (RGO). CFO has a band gap of 1.8 eV and is very much chemically and thermally stable. The key strategy in the designing of CdS/CFO/RGO nanostructure is to achieve the efficient transfer of electrons within the coupled components for enhancing the activity for phototelectrochemical water splitting and also to protect CdS from photocorrosion in aqueous solution using CFO as an outer layer of CdS. CdS/CFO/RGO nanostructure is synthesized by self assembly using a soft chemical method. First, CdS nanorods are synthesized by hydrothermal method using cadmium nitrate and thiourea in 50 ml ethylenediamine. Before growing CFO, the surface of the CdS nanorods is functionalized using a suitable functionalizing agent which leaves the surface of the nanorods with negatively charged ions. The core/shell nanostructures of CdS/CFO are obtained by using hydrothermal technique by keeping functionalized CdS nanostructures in cobalt nitrate and iron nitrate solution. The hydrothermal reaction is carried out in Teflon lined stainless steel autoclave at 120 °C for 10 hours. Afterwards, the synthesized CdS/CFO core/shell nanostructure is coupled with RGO by using chemical method. The synthesized CdS/CFO/RGO nanostructures are characterized by X-ray diffraction, UV-visible spectroscopy and Transmission electron microscopy. Photoelectrochemical measurements are performed using a three electrode electrochemical cell assembly. The thin films of CdS, CdS/CFO and CdS/CFO/RGO nanostructures are deposited by spray coating technique and are used as working electrodes. The CdS/CFO/RGO nanostructured film shows significant improvement in the photocurrent density and the incident photon conversion efficiency as compared to CdS and CdS/CFO nanostructure films. The enhancement in the photoelectrochemical activity in CdS/CFORGO nanostructure is due to the faster charge transfer between the coupled components and thus improves the overall photocurrent conversion efficiency.

Authors : Taekjib Choi, Chul min Youn, Heejin Lee
Affiliations : Hybrid Materials Research Center and Department of Nanotechnology and Advanced Materials Engineering, Sejong University, 143-747

Resume : Transition metal oxides are attractive as photoelectrodes for solar water splitting because of their stable photochemical activity in aqueous solutions. However, photoelectrochemical performance is usually limited by poor charge carrier separation. Thus, Hybrid photoelectrodes based on two-dimensional nanomaterials/ semiconducting ferroelectric materials offer promising potential for achieving efficient solar water splitting by enhancing charge conduction and promoting photogenerated-charge carrier separation due to spontaneous electric polarization leading to an increase in the effective electric field. In this study, we have fabricated two-dimensional nanomaterials decorated BiFeO3 thin films as hybrid electrodes. The structural and optical properties of single and hybrid electrodes were comparatively characterized. The hybrid electrodes exhibited a stronger absorption of visible light and produced a higher photocurrent than that of single electrode. For hybrid electrodes, photoelectrochemical characterization demonstrated a large enhancement of the interfacial charge transfer kinetics as well as an efficient charge carrier separation, which greatly contributed to the improved photoelectrochemical performances. In addition, we will discuss poling effect of electric polarization on interface reduction/oxidation (REDOX) through electrolyte ions. Therefore, our results provide useful information for developing highly efficient hybrid photoelectrodes for solar water splitting.

Authors : Hyunuk Kim, Young-Ju Lee, Yoonjong Yoo
Affiliations : Korea Institute of Energy Research

Resume : Carbon papers (CPs) with high electrical conductivities and gas permeabilities have been historically used as gas diffusion layers (GDLs) in proton exchange membrane fuel cells (PEMFCs). CPs with high electrical conductivities are fabricated by the high temperature carbonization of a thermosetting resin, which acts as a binder and makes the CPs brittle to bending. Herein, we report the fabrication of CPs containing a conducting polymer poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) under mild fabrication conditions. These CPs were prepared by combining pristine CP and PEDOT:PSS solutions with ethylene glycol (EG) and graphite powder (GP) and annealing the mixture at 100 C. The CP containing PEDOT:PSS-EG-GP possessed an electrical conductivity higher than that of conventional CPs that were fabricated by high-temperature carbonization of a thermosetting resin. The mechanical stability of the CPs containing PEDOT:PSS-EG-GP was much higher than that of conventional CPs because of the flexibility of the conducting polymer. Moreover, the novel CP maintained its electrical conductivity after bending. We evaluated the performance of a single-cell for used as a PEMFC in which the GDL was a CP containing PEDOT:PSS-EG-GP.

Authors : Paulina Poniatowska1, Daniel Jastrzebski1, Maciej Bialoglowski1, Dorota Brzuska1, Krzysztof Wozniak2, Roman Gajda2, Slawomir Podsiadlo1
Affiliations : 1 Faculty of Chemistry, Warsaw University of Technology; 2 Faculty of Chemistry, University of Warsaw

Resume : Semiconductors based on or related to tin sulfides, such as SnS, SnS2, and Cu2ZnSnS4, have recently lured the attention of researchers around the world. Having the bandgaps relatively close to the optimum of Shockley-Queisser limit, makes them especially interesting as potential absorbing materials in solar cells. This study reports a method for obtaining single crystals of Sn2S3, with a calculated bandgap of 1.1 eV. The syntheses have been carried out using chemical transport in vacuum. The obtained crystals have been characterized with X-ray diffraction methods, transmission electron microsocpy and Raman scattering spectroscopy.

Authors : C. Alegre*, C. D’Urso, S. Siracusano, E. Modica, C. Lo Vecchio, A.S. Aricò, V. Baglio
Affiliations : Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano” (CNR-ITAE),

Resume : Electrocatalysts for the oxygen reduction and/or the oxygen evolution reactions play a key role to determine the performance of energy conversion/storage devices, such as fuel cells, electrolysers, regenerative fuel cells or, recently, metal–air batteries. Oxygen electro-oxidation/electro-reduction presents slow kinetics, thus, in order to achieve high current densities, porous electrodes are required. Carbon materials are commonly used to increase the electrode surface area. The main disadvantage is that carbon corrosion processes can occur in particular during the oxygen evolution process at very positive potentials, thus affecting the stability of the catalysts. In this work, several carbonaceous (Vulcan, Ketjenblack) and non-carbonaceous (Ti-based) materials were used as supports for Pd electrocatalysts. The electrochemical investigation of these catalysts for the oxygen reduction and evolution processes was carried out in an alkaline medium. ACKNOWLEDGMENTS: Authors thank “Accordo di Programma CNR-MiSE, Gruppo tematico Sistema Elettrico Nazionale – Progetto: Sistemi elettrochimici per l’accumulo di energia” for the financial support.

Authors : Yong-Duck Chung1,3, Woo-Jung Lee1, Dae-Hyung Cho1, Jae-Hyung Wi1, Won Seok Han1, Jisu Yoo2, Yeonjin Yi2, Je-hyung Seo4, Myung-Woon Choi4
Affiliations : 1Components & Materials Research Laboratory, Electronics and Telecommunications Research Institute, Daejeon 305-700, Korea; 2Insitute of Physics and applied physics, Yonsei University, Seoul 120-749, Korea; 3Department of Advanced Device Engineering, Korea University of Science and Technology, Daejeon 305-350, Korea; 4System Development Team, YAS Co., Ltd. Paju-si 413-843, Korea.

Resume : It has been reported that Cu(In,Ga)Se2 (CIGS) exhibits the highest efficiency among all materials for thin-film solar cells. In general, the p–n heterojunction is formed by depositing a thin buffer layer on CIGS. Among buffer materials, Zn-based buffer has been steadily studied because of their beneficial properties, for examples, good transparency with large direct bandgap and less toxicity than Cd-based buffers which are typically used. In this study, we have characterized the interface of p-n heterojunction between Zn-based buffer and CIGS by measuring the impedance spectroscopy (IS) and investigated its influence on the photovoltaic performance with the variation of deposition process. The Zn-based buffer layer was deposited with two types of process. One was the formation of ZnS layer through the sulfurization of Zn film with S cracker and the other was chemical bath deposition (CBD) which was conventionally used. The interfacial properties of p-n heterojunction were investigated as a function of buffer layer thickness for cracking process and the concentration of chemical constituents for CBD process. The equivalent circuit was suggested, consisting of resistance and capacitances about junction interface. From the IS results, we discovered the direct correlation between photovoltaic performance and capacitance values, demonstrating the importance of interfacial quality in terms of the device performance.

Authors : A. Elfakir1,, G. Schmerber2, S. Colis2, A. Belayachi1, A. Dinia2, A. Slaoui3 and M. Abd-Lefdil1
Affiliations : 1 University of Mohammed V- Agdal, Materials Physics Laboratory, P. B. 1014, Rabat, Morocco; 2 IPCMS, CNRS-Université de Strasbourg, 23 rue du Loess, F-67037 Strasbourg cedex 2, France; 3 ICube, CNRS-Université de Strasbourg, 23 rue du Loess, F-67037 Strasbourg cedex 2, France.

Resume : Neodymium and thulium codoped ZnO (NTZO) thin films were deposited on glass substrates by chemical spray pyrolysis method. The influence of both doping concentration on structural, optical and electrical properties were characterized by various techniques. X-ray diffraction (XRD) patterns revealed that all the films have a polycrystalline nature fitting with a hexagonal wurtzite structure. Transmittance measurements showed that the addition of Tm reduced the optical transmittance from 80% to about 50% in the visible region while the optical band gap increased slightly with Tm doping concentration. Photoluminescence spectra were dominated by an emission band due to the radiative recombination of excitons, which decreased and shifted toward lower wavelength region after Tm doping. Electrical resistivity value around 4 10-2 Ω.cm was achieved for NTZO films.

Authors : S. Polivtseva, A. Katerski, E. K?rber, I. Oja Acik, A. Mere, V. Mikli, M. Krunks
Affiliations : Tallinn University of Technology, 19086 Tallinn, Ehitajate tee 5, Estonia.

Resume : SnS is an attractive absorber material for solar cells due to its direct optical bandgap of 1.35 eV and absorption coefficient higher than 104 cm-1. In this study SnS films were deposited by the chemical spray pyrolysis technique using tin chloride (SnCl2) and thiourea (SC(NH2)2) at molar ratios of Sn:S= 1:1 and 1:8 in aqueous solution. The precursor solution was sprayed onto soda-lime glass substrates at 200 ?C in air. We studied the effect of post-deposition annealing in nitrogen (N2) and in vacuum on properties of sprayed films. Post-deposition treatments were performed at 450 ?C for 60 min in both environments. Films were characterized by XRD, Raman and UV-Vis spectroscopies, SEM and EDX. Both the 1:1 and 1:8 as-deposited films grown at 200 ?C are composed of SnS as a main crystalline phase, an unknown crystalline phase is present additionally. According to XRD, annealing of 1:1 and 1:8 films in N2 resulted in SnO2 and Sn2S3 as main phases, respectively. Raman study supports the results obtained by XRD, and confirms the presence of SnS in both films. An unknown phase, present in as-deposited films was still present in trace amounts. Annealing of 1:1 and 1:8 films in vacuum resulted in Sn and SnS as main phases, respectively. Unknown phase present in as-sprayed films was not detected anymore. The 1:37 eV optical bangap of SnS film could be obtained by spray at 200 ?C using thiourea-rich spray solutions and applying post-deposition thermal treatment in vacuum at 450?C

Authors : Oleksandra Korovyanko1,2, Mykhailo Sytnyk3,4 Eric Daniel Glowacki1, Wolfgang Heiss3,4, Philipp Stadler1
Affiliations : 1 Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University Linz, Altenberger Straße 69, 4040, Linz, Austria; 2 Chernivtsi National University, 2, Kotsyubynskogo, 58012, Chernivtsi, Ukraine; 3 Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstraße 7, 91058 Erlangen, Germany; 4 Energie Campus Nürnberg (EnCN), Fürther Straße 250, 90429 Nürnberg, Germany

Resume : Lead-sulfide (PbS) nanocrystals (NCs) have demonstrated promising results in photovoltaic (PV) applications. It has stimulated an immense interest in the development of IR-active NCs, including synthesis, surface functionalization, and properties investigation. Nevertheless, an additional step of ligand-exchange is required in order to improve charge transport, which can be carried out after the film deposition by a ligand exchange. Post-deposition ligand-exchange strategies lead to a more full replacement of bulky organic ligands and to a better photoconductivity of obtained materials. Searching an appropriate ligand is of utmost importance for the optimization of applicable NC films properties. The objective of this research is to develop and characterize PbS quantum dot solids for the next generation PV technology. The optically active films are produced using PbS NCs colloids and applying solid-state ligand exchange with short conjugated ligands during film preparation. We performed complex investigations both for PbS NCs films optical properties before and after ligand exchange procedure and PV device characterization. This development of the post-synthetic ligand exchange procedure facilitates charge transport in the NC film while increasing the electronical communication between PbS NCs and reducing charge trapping states. Our results provide important insights on how to get better charge transfer and experimental control on the fabrication of efficient NC PVs.

Authors : Krunoslav Juraic (1,2), Davor Gracin (1), Milivoj Plodinec (1), Daniel Meljanac (1), Krešimir Solomon (3), Sigrid Bernstorff (4), Miran Čeh (5)
Affiliations : (1) Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; (2) Institute of Inorganic Chemistry, Graz University of Technology, Graz, Austria; (3) Institute of Physic, Bijenička cesta 46, 10000 Zagreb, Croatia; (4) Elettra-Sincrotrone Trieste, SS 14, km 163.5, 34149 Trieste, Italy; (5) Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia

Resume : TiO2 is one of the most intensively investigated compounds in material science due to its essential properties. It is a wide band gap semiconductor having band-edge positions appropriate for solar cell applications and for hydrogen generation by water splitting. It is also known as a non-toxic, environment friendly, corrosion-resistant material. Nano-forms of TiO2 such as nanoparticles, nanorods, nanowires and, in particular nanotubes can be used as photo-electrode in dye sensitized solar cells. The conversion efficiency of solar cells can be significantly improved by using oriented nanorod-like materials on top of transparent conductive oxide. For this purpose we prepared TiO2 nanotube arrays by anodizing titanium thin film deposited on ZnO covered glass substrate. Initial Ti films were prepared by evaporation or magnetron sputtering. The diameter and length of the nanotubes were controlled by the parameters of anodization, mainly voltage and etching time. The structural properties of the obtained TiO2 nanotubes arrays were estimated by simultaneous small and wide angle x-ray scattering under grazing incidence geometry. The results will be also correlated to the deposition parameters and results obtained by high resolution electron microscopy, scanning electron microscopy and Raman spectroscopy. It will be also discussed a possible application in dye sensitized solar cells.

Authors : Tina Nestler1, William Förster2, Wolfram Münchgesang1, Stanislav Fedotov3, Charaf Cherkouk1, Stefan Braun2, Falk Meutzner1, Tilmann Leisegang1, Dirk C. Meyer1
Affiliations : 1Institute of Experimental Physics, TU Bergakademie Freiberg, Freiberg, Germany, 2Fraunhofer-Institute of Material and Beam Technology IWS, Dresden, Germany, 3Department of Chemistry, Moscow State University, Moscow, Russia

Resume : The constantly increasing demand for high-energy-density batteries as well as the shortage of lithium resources spurs the need to investigate other battery materials and concepts. Aluminum, with its theoretically high capacity and its high abundance, would be an excellent candidate. Up to the present, there are only a few reports on rechargeable Al-ion batteries due to the fact that the high valence of Al3+ places high demands on cathode intercalation materials and electrolytes. Finding suitable solid electrolytes is an even greater challenge. Solid electrolytes, however, could enable reliable on-chip power supply with outstanding volumetric energy densities for sensors and other applications. Literature reports on Al2(WO4)3 hint on ionic conductivity at least above 300 °C. Even though the bond valence sum mapping performed here suggests no ion conductivity at room temperature, this material was chosen as model system. Thin films have been prepared by pulsed laser deposition. The phase purity and morphology of thermally annealed thin films and thin films crystallized by flash-lamp annealing (FLA) are compared. For a deeper understanding of results of the FLA treatment, the temperature distribution is modeled. Pure Al2(WO4)3 thin films have been synthesized for the first time by thermal treatment of deposited multistacks derived from Al2(WO4)3- and Al2O3-targets. To evaluate the conduction mechanism of these films, temperature-dependent impedance spectroscopy measurements are discussed.

Authors : Marius Treideris, Arunas Setkus, Irena Simkienė, Alfonsas Reza, Viktorija Strazdiene, Jevgenij Visniakov
Affiliations : Center for Physical Sciences and Technology, A. Goštauto 11, Vilnius LT01108, Lithuania

Resume : Silicon solar cells are the most widely manufactured due to well developed technology and comparatively low manufacturing cost. However future perspectives of such cells as independent devices and as integrated to system-on-the chip compared to new emerging materials in photovoltaic’s depends on new technological procedures and new solar cell concepts based on increasing the pn junction area. In this work we present solar cell based on the electrochemically etched nanotunnel matrix. Nanotunnel matrix for the solar cell was made by the low cost electrochemical etching method on n-type monocrystalline silicon wafers. P-n junction was formed by boron diffusion from spin-on borosilicate glasses. Front contact was made by chemically plated nickel grid and the back contact by depositing silver. Optical measurements have shown that electrochemically formed nanotunnel matrix can reduce reflectance in the visible range from the cell surface to less than 3%. Electrical measurements we carried under one sun illumination. In the present development phase, we demonstrate solar cell with electrochemically etched nanotunnel matrix on n-type silicon without the passivating layer with the open circuit voltage ~0.6V, short circuit current ~10 mA/cm2 and the fill factor ~0.6.

Authors : S.-J. Joo, B.S. Kim, B.-K. Min, J.-E. Lee, B.K. Ryu, H.W. Lee, S.D. Park
Affiliations : Thermoelectric Conversion Research Center, Korea Electrotechnology Research Institute

Resume : In this study, Bi2Te3 and Sb2Te3 thin films were deposited by using an RF magnetron co-sputter, and the relationship between the process parameters and the thermoelectric properties were investigated. Oxidized silicon wafers as well as thin polyimide films (thickness=25 μm) were used as substrates, and the deposition temperature was varied in the range of 200 and 350 ℃. The maximum Seebeck coefficient of the stoichiometric Bi2Te3 films was about -193 μV/K, and a power factor (PF) of 0.97 mW/mK^2 (at 32 ℃) was obtained at the optimum deposition condition. Also, the PF increases significantly when (00L) is the preferred orientation. In case of Sb2Te3, the maximum PF of 1.34 mW/mK^2 (at 98 ℃) was obtained from the nearly stoichiometric as-deposited film, which increases to 2.03 mW/mK^2 after post-deposition annealing at 350 ℃. (00L) peaks get stronger after annealing; confirming again that (00L) preferred orientation accompanies the enhancement of thermoelectric properties. The flexibility of the Bi2Te3 films deposited on the polyimide films were tested by repeatedly winding and releasing them around the metal cylinders with specific radii, and the electrical resistance was monitored with respect to the number of bending. Noticeable increase of the film resistance was not observed when the radius of the metal cylinder was larger than 5 mm, and the resistance was only 7.5 % higher than the initial value after bending 300 times using a cylinder with 5 mm radius.

Authors : E. Napolitano*,1, L. Fernández Albanesi2, F.C. Gennari2, M. Hoelzel3, S. Garroni4, P. Moretto1, S. Enzo4
Affiliations : 1 European Commission -DG JRC-Institute for Energy and Transport, Westerduinweg 3, NL-1755 Petten, The Netherlands. 2 Centro Atómico Bariloche (CNEA) and CONICET, (8400) San Carlos de Bariloche, Argentina. 3 Forschungs Neutronenquelle Heinz Maier-Leibnitz (FRM II),Technische Universität München, Lichtenbergstrasse 1, D-85747 Garching, Germany. 4 Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari and INSTM, Via Vienna 2, I-07100 Sassari, Italy.

Resume : In the field of solid-state hydrogen storage, the alkali amides and alkaline-earth analogues present promising hydrogen mass and volume ratios together with remarkable reversibility in terms of hydrogen release and up-take processes [1]. Unfortunately, the formation of new unclassified phases during intermediate steps of the absorption/desorption reaction pathways may constitute a severe limitation to understanding the basic mechanisms of the reaction kinetics. Recently, with the intent to improve sorption characteristics and to modify thermodynamic properties of the well-known LiNH2-LiH system, a study on AlCl3-doped composite describing the formation of a new Li-Al-N-H-Cl compound was reported in literature [2], without its crystal structure being established. In order to elucidate the reaction pathways in complex hydrogen storage materials, the new Li-Al-N-H-Cl composite was synthesized from deuterated precursors and neutron plus laboratory X-ray diffraction data were combined with the so called ab-initio numerical methods [3] also supplemented by FT-IR, DSC and TPD-MS experimental data with the objective to solve the crystal structure and to shed light on the hydrogen atom interactions. References [1] P. Chen, et al., Nature 420 (2002) 302. [2] Fernández Albanesi et al., Int. J. Hydrogen Energy 38 (2013) 12325-12334. [3] R. Cerný, Zeit. Kristall. - Cryst Mat. 223 (2008) 607-616.

Authors : S. Vatavu, N. von Morze, S. Wiesner, V. Hinrichs, M.-Ch. Lux-Steiner, and M. Rusu
Affiliations : Institut für Heterogene Materialsysteme, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, Berlin, 14109, Germany

Resume : In this contribution, CuInSe2-nanocrystals (CuInSe2-NCs) are investigated for application in hybrid organic/inorganic solar cell devices. We report CuInSe2-NCs prepared by chemical close-spaced vapor transport (CCSVT) at 450C from precursors of Cu-nanoparticles on Mo/Na barrier/glass substrates. Cu-nanoparticles were prepared by the spray ion layer gas reaction (spray-ILGAR) method at 430C. The linear dimensions and spacing of Cu nanoparticles were controlled by the substrate temperature, deposition time, flow rate and molar concentration of the sprayed ethanol solution of Cu(hfac)2. The average diameter and height of Cu nanoparticles varied depending on the deposition time as 40-60 nm and 30-80 nm, respectively. The resulting CuInSe2 nanostructures had thickness in the range of 30-170 nm. The elemental composition of the as-prepared CuInSe2-nanostructures were analyzed by Inductively Coupled Plasma Mass-Spectrometry (ICP-MS), while the phase composition was investigated by grazing incidence X-ray diffraction (GI-XRD). Stoichiometric composition was revealed by ICP-MS for optimum deposition conditions. GI-XRD (0.1-1.1 deg.) revealed diffraction peaks from (112), (204)/(220) and (116)/(332) planes of CuInSe2. Formation of (111) Cu2-xSe or (006) InSe phases were suppressed for optimum preparation conditions.

Authors : Victor Timoshenko (1,2), Kairola Sekerbayev (3), Gulden Botantayeva (3), Dana Yermukhamed (3), Yerzhan Taurbaev (3), Tokhtar Taurbaev (3)
Affiliations : (1) Physics Department of Lomonosov Moscow State University, Moscow, Russia. (2) National Research Tomsk State University, Lenina Avenue 36, Tomsk 634050, Russia; (3) Physico-Technical Department of al-Farabi Kazakh National University, Almaty, Kazakhstan.

Resume : We report results of the photoluminescence and Raman spectroscopy of thin films of organometal perovskites, which are now attracting a great attention of the photovoltaic community. The films of organometal halides are deposited by spin coating from solutions or by evaporation in vacuum conditions on quartz and glass substrates covered with fluorine-doped tin oxides and titanium dioxide. The prepared perovskite thin films are investigated by means of the electron microscopy and optical spectroscopy. Characteristics of the prepared perovskite solar cells with different parameters of the structure and composition are studied by using photoelectrical measurements. The formed perovskite solar cells are tested to reveal dependences of the conversion efficiency and stability on the preparation conditions. The obtained results are used to find the optimal structural and optoelectronic properties of perovskite thin films for creation of highly efficient solar cells.

Authors : M. S. Islam, G. S. Rao, T. Hussain and Rajeev Ahuja
Affiliations : Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala, Sweden

Resume : Owing to its highest energy density per mass, the potential of hydrogen (H2) as energy carrier has been immense, however its storage remained to be a big obstacle [1]. By means of density functional theory (DFT) in spin polarized generalized gradient approximation (GGA), we have investigated the structural, electronic and hydrogen storage properties of light metals functionalized fluorographene monolayer [2]. The light metals considered here include Li, Na, Be, Mg and Al. All of these metal adatoms bind to the fluorographene with reasonable high binding energy, much higher than their cohesive energies, which help to achieve the uniform distribution of metal adatoms on the monolayer and consequently the reversibility. Each metal adatom transfer a significant amount of their charge to the fluorographene monolayer and attain a partial positive state, this facilitate the adsorption of multiple H2 molecules around the adatoms by electrostatic as well as van der Waals interaction. To get a better description of H2 adsorption energies with the metal doped systems, we have also performed the calculations using van der Waals corrections [3]. For all the functionalized systems, the results indicate a significantly high H2 storage capacity with the H2 adsorption energies fall into the range for the practical applications. References: 1. L. Schlapbach, Nature 460, 809 (2009) 2. R. R. Nair, W. C. Ren, R. Jalil et

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Authors : Francois Aguey-Zinsou
Affiliations : MERLin, School of Chemical Engineering, The University of New South Wales, Sydney, Australia

Resume : Storing hydrogen in materials is based on the observation that metals can reversibly absorb hydrogen. However practical application of such a finding has found to be rather challenging especially for vehicular applications. The ideal material should reversibly store a significant amount of hydrogen under moderate conditions of pressures and temperatures. To date, such a material does not exist and the high expectations of achieving the scientific discovery of a suitable material simultaneously with engineering innovations are out of reach. Of course, major breakthroughs have been achieved in the field, but the most promising materials still bind hydrogen too strongly and often suffer from poor hydrogen kinetics and/or lack of reversibility. Clearly, new approaches have to be explored, and the knowledge gained with high-energy ball milling needs to be exploited, i.e. particle size does matter! The properties of nanomaterials are known to be size depend. Such size depend effect could offer powerful means to finally control both the thermodynamic and kinetic properties of hydride materials at the molecular level. Here, the potential of this new approach and the major breakthroughs we have achieved in recent years through nanosizing will be discussed. In particular, the effects of particle size restriction on some of the most promising hydrogen storage light materials, e.g. magnesium, lithium, aluminum, and borohydrides will be reported.

Authors : Jeha Kim, Yong-Duck Chung, Dae-Hyung Cho
Affiliations : Cheongju University; ETRI; ETRI

Resume : We studied the CIGS film growth incorporated with Na by using NaF evaporation in which Na ions from the soda-lime glass substrate were controlled by a presence or an absence of a SiOx barrier. Gradually increasing Na content in CIGS was found in the structures of CIGS/Mo/SiOx/SLG, CIGS/Mo/SLG, CIGS/5 nm-NaF/Mo/SiOx/SLG, CIGS/5 nm-NaF/Mo/SLG, CIGS/15 nm-NaF/Mo/SiOx/SLG, and CIGS/15 nm-NaF/Mo/SLG. With increasing Na content, the CIGS film exhibited (112) preferential growth along the surface normal with the (220/204) textures. The sample with a CIGS/5 nm-NaF/Mo/SiOx/SLG structure achieved the comparable (112)/(220/204) peak ratios, grain sizes, as well as the cell performances to a CIGS/Mo/SLG structure that contains the same Na content in the CIGS. Using the X-ray diffraction (XRD) techniques of high resolution θ-2θ scan and reciprocal space mapping, we discerned the (220)- and (204)-oriented textures of CIGS that independently depended on both substrate nature and Na presence. For a solar cell fabricated in a structure of ITO/i-ZnO/CdS/CIGS/Mo/SiOx/soda-lime glass (SLG), we found that the energy conversion efficiency η increased for relatively low Na content but the thick NaF led to a degradation of η because of poor adhesion between the CIGS and the Mo. It was observed that the hole concentration of CIGS was enhanced as the Na content increased, while the band-gap was nearly constant, which led to a lower Fermi level in the CIGS towards its valence-band edge. The Na-induced increment in the built-in potential (Vbi) across the n-(ITO/i-ZnO/CdS)/p-CIGS junction yielded an increment of open-circuit voltage that well agreed with the calculated Vbi.

Authors : Boyun Jang, Chanhi Moon, Sunho Choi, Joonsoo Kim
Affiliations : Korea institute of energy research

Resume : Wafer charges on more than 30 % of production cost for single crystalline silicon (Si) solar cells. Multiwire with free-abrasive (slurry on wire) or fixed-abrasive (diamond on wire) are usually used for slicing Si brick. Both of them, however, are based on mechanical fracture of Si by abrasive, which causes wafer breakage during the slicing and physical defects such as saw marks and micro-cracks on the sliced wafer. Therefore, slicing using multiwire without mechanical fracture of Si has a competitive potential as a new wafering process. Electrical discharge (ED) is an excellent energy source to slice Si brick because there is no mechanical stress between wire and Si. Electrical discharge is well known for precise machining of metal. We have developed pulsed-direct current (DC) ED source to slice Si brick. Single crystalline Si brick (1.65 ~ 1.72 ohm•cm) with dimension of 25 x 25 mm2 was sliced by pulsed-DC ED on 3-wires of Zn-coated Brass. Slicing speed was 20 mm2/min, which indicated that 156 x 156 mm2 wafers could be obtained only for 1,216 mins. The wafer thickness and kerf were 180 and 100 um, respectively. Details of new wafering process and wafer properties including microstructures will be presented. Some wafer samples will be exhibited as well.

Authors : G. Wang1, R. van den Berg1, K.P. de Jong1, C. de Mello Donega2, P.E. de Jongh1*
Affiliations : 1 Inorganic Chemistry and Catalysis; and 2 Condensed Matter and Interfaces Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands *

Resume : Cu2O is a p-type semiconductor with a band gap of ~2.2 eV which attracts much attention for application in photovoltaics, photocatalysis and solar water splitting, but is not intrinsically stable under illumination in aqueous solutions. Cu2-xS compounds have a much higher intrinsic stability, and fascinating, though not completely understood, optoelectronic properties. However, synthesis of particles with well-defined size and morphology is a great challenge. We explore new strategies to assemble Cu-based semiconductor nanoparticles with controlled size and morphology, amongst others using mesoporous silica supports.1,2,3 For instance the size of Cu2O nanoparticles was tuned from 2 nm to 16 nm by varying either the concentration of the Cu-precursor or the pore diameter of the supporting silica, followed by subsequent conversion to Cu2O by gas-phase reduction with carbon monoxide.3 The activity, stability and selectivity of the as-obtained nanoparticles, for different sizes and compositions, were examined for solar-driven H2 evolution and in photocatalytic oxidation. A few examples will be highlighted, such as the relatively high stability of silica-supported Cu2O nanoparticles, and the possibility to influence the selectivity of the photocatalyzed oxidation reactions. Acknowledgement: The research is funded by the Dutch NRSCC-Solar Fuels program. References: 1 G. Prieto, P.E. de Jongh et al. Nature Mater. 12 (2013) 34-39. 2 W. van der Stam, C. de Mello Donega et al. Chem. Mater. 27 (2015) 283-291. 3 G. Wang et al. Submitted (2015)

Authors : Daniel Jastrzebski1, Maciej Bialoglowski1, Stanislaw Bednarz1, Edyta Pesko1, Piotr Dluzewski2, Cezariusz Jastrzebski3, Slawomir Podsiadlo1
Affiliations : 1 Faculty of Chemistry, Warsaw University of Technology; 2 Institute of Physics, Polish Academy of Sciences; 3 Faculty of Physics, Warsaw University of Technology

Resume : A vast proliferation of studies that seek novel photovoltaic materials and technologies has been observed recently. Tin(II) sulfide – a stable compound consisting of abundant and non-toxic elements – seems to be especially interesting. Owing to its electron and structural properties, it might become a promising material for highly efficient multi-junction solar devices. In this study, direct and indirect bandgap modifications of SnS nanopowders have been explored. The syntheses have been carried out in organic solvents, using tin salts and sulfur. The obtained materials have been characterized with X-ray powder diffraction, Raman scattering spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and spectrophotometry UV/Vis/NIR.

Authors : Yong-Mook Kang*, Kyeongse Song, Mihui Park, Jaepyeong Jung, Daniel Adjei Agyeman
Affiliations : Department of Energy & Materials Engineering, Dongguk University-Seoul, 100715 Seoul, Republic of Korea

Resume : Rechargeable lithium batteries have the potential to provide an energy storage solution to depletion of fossil fuel resources and global warming because they are also considered as clean power sources from renewable energy sources for next-generation electric applications such as electric vehicle (EV), portable electric appliances, and large-scale energy storage system. The energy density of the conventional lithium ion battery cannot meet the stringent requirements for these applications, whereas lithium-air batteries have significantly high theoretical specific energy coming up to 11,140 Wh/kg because lithium–air batteries are based on discharge reaction between Li and oxygen to yield Li2O2. However, regardless of its high energy density, low cycling capability remained as an important hurdle for commercialization. A major drawback about lithium-air batteries is its low round trip efficiency coming from very large potential difference between ORR and OER (Oxygen evolution reaction). Various types of materials have been adopted for the catalysts to reduce potential hysteresis and thus attain high round-trip efficiency. In particular, α-MnO2 has received great attention as an oxide catalyst for lithium-air batteries since its superior catalytic activity was introduced by P.G. Bruce et al.. Because the relatively good catalytic activity of α-MnO2 among various metal oxides results from easy accommodation of Li2O2 inside its large 2x2 tunnel structure, many researchers have tried to vary the macrophysical properties such as porosity, surface-to-volume ratio and so on to enhance the electrochemical properties of lithium-air batteries using α-MnO2. However, such kind of piecemeal approaches without detailed understanding on the fundamental physical properties governing the catalytic activity of materials failed to make a breakthrough in the development of commercially available catalysts. Hence, the shape or surface structure of catalysts has been regarded as the crucial physical factors to determine its catalytic activity in various applications. However, very little is known about the catalyst shape-dependent activities or the structure sensitive catalytic activities for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the cathode of lithium-O2 battery. Hence, we here try to change the crystal structure, surface structure and shape of noble metal catalysts to elucidate their effects on the catalytic activities. Various catalysts such as PdCu, Pt3Co, Pt, etc. have been used to figure out the fundamental design principles of noble metal catalysts for Li-O2 batteries. As a result, we knew that surface energy, crystal structure and elemental composition are all important to develop the most optimum metal catalysts to attain high reversibility of Li-O2 batteries.

Authors : Eylül Saraç, Uğur Ünal
Affiliations : Graduate School of Science and Engineering, Koç University, Rumelifeneri Yolu, Sarıyer, Istanbul, Turkey; Chemistry Department, Koç University, Rumelifeneri Yolu, Sarıyer, Istanbul, Turkey

Resume : Electrochemical Capacitors (ECs) are in the focus of electrical energy storage research field due to their long term stability, environmental compatibility, and high energy density without sacrificing any power density. In the study of interest, composites of graphene oxide and different metal ions (Fe, Co, Cu, Mn, Ni, and Ag) are combined to produce electrodes for ECs; the effect of reducing graphene oxide on specific capacitance (SC) is examined. Graphene obtained from reduction of graphene oxide has several advantages compared to graphene obtained from direct exfoliation of graphite. Former one has dispersibility in aqueous environment, and pseudocapacitative properties due to remaining functional groups. Composite electrodes are tested on HOPG (highly oriented pyrolytic graphite) electrodes by Cyclic voltammetry in different electrolyte solutions and in different potential ranges for different metal ions. It has been observed that there is a significant increase in SC values of composite electrodes after reduction of graphene oxide. Before reduction, maximum SC are obtained with Fe2+ and Cu2+ composites having SC of 28.3mF/cm2 and 25.8mF/cm2 at scan rate of 20mV/s, respectively. Whereas after reduction, maximum SC having samples are Co2+ and Mn2+ with 144.0mF/cm2 and 134.5mF/cm2 (at scan rate 20mV/s), respectively. Moreoever, there is almost twenty fold increase in SC in Mn2+, Co2+, and Ni2+ composites before and after reduction of samples. The reasons behind the enhanced capacitance are examined by X-ray photoelectron spectroscopy, Raman spectroscopy, and Field-Emission scanning electron microscopy by analyzing the electrodes before and after reduction of graphene oxide.

Authors : Zbigniew Łodziana
Affiliations : Institute of Nuclear Physics PAN, Department of Structural Research, ul. Radzikowskiego 152, 31-342 Kraków, Poland.

Resume : Metal borohydride complexes and their derivatives are of interest due to their potential as an energy storage materials. Tuning of their thermodynamic and kinetic properties is achieved via formation of mixed-metal borohydride complexes; ammonia-containing metal borohydrides; confinement in small nanopores. Any of such procedures leads to materials with complex crystalline structure that is difficult to study due to large fraction of light elements. This complexity is a challenge for theoretical description. Challenges in theoretical description of tuned complex hydrides will be presented, and simple descriptor of their stability based on ionic potential will be introduced. Such descriptor is related to well-known relation between stability and Pauling electronegativity, however it can be accurately calculated for crystalline materials.

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Authors : Anja Bieberle-H?tter
Affiliations : DIFFER (Dutch Institute for Fundamental Energy Research)

Resume : The direct conversion of solar energy into storable fuels is a holy grail in the area of sustainable energy solutions. Photo-electrochemical solar fuel conversion is considered as a very promising route for the production of fuel from sunlight. It is believed to reach higher overall efficiencies than water splitting through an electrolyser powered by photovoltaics [1]. However, since the early studies of Fujishima et al. [2], a commercial breakthrough has not yet been achieved, mainly due to efficiency and stability issues of the photoelectrodes. Current research focuses mainly on experimental studies; modeling & simulation studies are in general rare and strongly focus on combinatorial studies in order to find alternative materials. In this presentation, we will summarize the current approaches which are taken to model the photo-electrochemical interface in order to gain a better understanding of the mechanisms taking place there. We will discuss the challenges in general and with individual approaches. Then, we will discuss our multi-scale approach of modeling & simulations of photo-electrochemical interfaces where we strive to compare experimental and simulated data directly. Experimental results on hematite model electrodes and Density Function Theory (DFT) calculations of the same surfaces will be presented. 1 van de Krol, R. & Gr?tzel, M. Photoelectrochemical Hydrogen Production (Springer, 2012). 2 Fujishima, A. & Honda, K. Nature 238, 37-38 (1972).

Authors : N.L. Saini
Affiliations : Dipartimento di Fisica, Sapienza Universit? di Roma, P.le Aldo Moro 2, 00185 Roma, Italy

Resume : Transition metal oxides are commonly used in Li-batteries, however their peculiar physical properties can be limiting factors for the desired battery characteristics. Here, we will briefly review site-selective structural properties of LiCoO2 and V2O5 battery materials, measured by x-ray absorption spectroscopy. The nanostructuring of LiCoO2 is found to have direct effect on the bondlength characteristics, with a substantial change in the force constant of Co-O bonds while Co-Co bonds showing hardly any change. Therefore, both random disorder and Co-O bondlength flexibility should be the factors to limit the charging/discharging characteristics of the LiCoO2 nanoparticles. On the other hand, study of morphologically different V2O5 reveals distinct local structure properties as well the electronic structure. It is found that the nanowires have a significantly ordered chain structure in compare to the V2O5 bulk, having direct implication on the use of nanowires as battery materials. We have also determined local structure of LiMnO2, LiMn(1-x)Cr(x)O2 and LiMn(1-x)Ni(x)O2 compounds, showing the Jahn-Teller distortions in LiMnO2 and their suppression in substituted systems. Distinct local disorder in differently substituted LiMnO2 seems to be the reason for distinct battery characteristics of these materials.

Authors : E. Senokos 1 2, R. Marcilla 2, J.J. Vilatela 1, V. Reguero 1, J. Palma 2
Affiliations : [1] IMDEA Materials Institute, Eric Kandel 2, Madrid, Spain; [2] IMDEA Energy Institute, Av. Ramón de la Sagra 3, Mostoles, Madrid, Spain

Resume : Carbon nanotubes fibers have been synthesized by the direct spinning process from the gas-phase during growth of CNTs by floating catalyst chemical vapor deposition. This method enables the production of kilometres of macroscopic fibres that can be assembled as films. In this work, we show that such materials are good candidates as electrodes for robust supercapacitors. They combine: high-performance mechanical properties, such as specific tensile strengths around 1 GPa/SG, modulus close to 40 GPa/SG, toughness of 36 J/g and high-flexibility; high electrical conductivity (3.5x10^5 S/m), and high specific surface area (˃ 100 m^2/g). The intrinsic electrochemical performance of CNT fibers is studied by cyclic voltammetry in three-electrode system using PYR14 TFSI as ionic liquid electrolyte. The results show a capacitance of 54 F/g at 10 mV/s and 3.5 V. Symmetric supercapacitor devices produced by assembling two CNT fibers electrodes and PYR14 TFSI electrolyte were also tested. The devices have an energy density of 11 Wh/kg and power density of 11 kW/kg at 5 mA/cm^2 and 3.5 V. A comparison of specific capacitance and toughness of CNT fibers (54 F/g and 36 J/g) with activated carbon (80 F/g and 0.2 J/g) and carbon fibers (1.3 F/g and 19 J/g) shows potential applications of this material in multifunctional structural supercapacitors.

Authors : L. Simonelli1, W. Olszewski1, 2, M. Avila Perez1, C. Marini1, T. Mizokawa3, 4, N.L. Saini5, and T. Broux6 ,7, L. Croguennec6, F. Fauth1, M. Bianchini6, 7, 8, C. Masquelier7
Affiliations : 1Alba Synchrotron Light Facility, Crta. BP 1413, Km. 3.3, 08290 Cerdanyola del Vall?es, Barcelona, Spain, EU 2Faculty of Physics, University of Bialystok, 1L K. Cio lkowskiego Str., 15-245 Bia lystok, Poland, EU 3Department of Physics, University of Tokio, 5-1-5 Kashiwanoha, Kashiwa, Chiva 277-8561, Japan 4Dep. of Complexity Science and Engineering, Univ. of Tokio,5-1-5 Kashiwanoha, Kashiwa, Chiva 277-8561, Japan 5Dipartimento di Fisica, Universit?a di Roma ?La Sapienza? - P. le Aldo Moro 2, 00185 Roma, Italy, EU 6Institut de Chimie de la Mati?re Condens?e de Bordeaux (ICMCB), Univ. Bordeaux, Bordeaux INP, Pessac, France 7Laboratoire de R?activit? et de Chimie des Solides (LRCS), Universit? de Picardie Jules Verne, Amiens, France 8Institut Laue-Langevin, Grenoble, France

Resume : The raising necessity in energy conversion and storage requires a constant development of cathodes with higher energy and power densities as well as cost-effectiveness, safety, sustainability, eco-friendliness, rate capability, and large-scale manufacturing. Beside lithium ions derived cathode materials, whose outstanding electrochemical performance have been demonstrated in Lithium-ion batteries [1, 2], several sodium-rich cathode materials have been recently proposed. Indeed, sodium-ion batteries have attracted growing attention because of the natural abundance and low toxicity of sodium [3-5]. The lifetime and efficiency of a battery are obviously key points, and are strongly related to the reversibility of deintercalation and intercalation reactions. During the charging/discharging processes the cathode crystal structure could undergo bond variations that have direct consequences on the reversibility of ion migration in the cathode [1,6,7]. For example it has been shown that the structural and electronic properties of the layered cobaltate NaxCoO2 vary after electrochemical intercalation or deintercalation of sodium [8, 9] strongly influencing the incredibly high Na diffusion speed [10]. More in general distortion could not occur at long range and could not be detected by conventional diffraction techniques. X-ray absorption spectroscopy (XAS) is the most suitable technique to access to the local structure as a function of the charge state, giving at the same time access to complementary information about the electronic properties. Here we report on the sodiation/desodiation effects on the local electronic and structural properties of NaxCoO2 cathode material by an ex-situ temperature dependent Co K-edge X-ray absorption spectroscopic study, comparing the obtained results with those gathered at the most used LixCoO2 material, and demonstrating clearly different intercalation chemistry for the two systems. This result reinforces the suitability of NaxCoO2 for applications and clearly underlines the key role of local atomic displacements in the CoO6 octahedra and disorder, being limiting factors for the diffusion and the reversibility of ions in cathodes for batteries. Finally we report on the operando investigation of the redox processes involved during sodium deintercalation from the Na3V2(PO4)2F3 cathode material [11]. X-ray absorption near edge structure measurements collected at the V k-edge finally reveal the charge compensation mechanism on the V site, in a system where a complex phase diagram is formed as a function of the charge state [12]. References: [1] J. M. Tarascon and M. Armand, Nature, 2001, 414, 359?367; [2] J. M. Tarascon, Philos. Trans. R. Soc., A, 2010, 368, 3227?3241; [3] H. K. Song, K. T. Lee, M. G. Kim, L. F. Nazar and J.Cho, Adv. Funct. Mater. , 2010, 20, 3818?3834; [4] V. Palomares, P. Serras, I. Villaluenga, K. B. Hueso, J. Carretero-Gonzalez and T. Rojo,Energy Environ. Sci., 2012, 5, 5884?5901; [5] B. L. Ellis and L. F. Nazar, Curr. Opin. Solid State Mater. Sci., 2012, 16, 168?177; [6] J.B. Goodenough, Y. Kim, Chem. Mater. 22 (2010) 587; [7] P. He, H. Yu, D. Li, H. Zhou, J. Mater. Chem. 22 (2012) 3680; [8] Q. Huang et al., PHYSICAL REVIEW B 70, 184110 (2004); [9] R. Berthelot et al., Nature Materials 10, 741780 (2011); [10] Takayuki Shibata et al., SCIENTIFIC REPORTS 5, Article number: 9006 (2015); [11] M. Bianchini, N. Brisset, F. Fauth, F. Weill, E. Elkaim, E. Suard, C. Masquelier and L. Croguennec, Chem. Mater., 26(14), (2014), 4238; [12] M Bianchini, F Fauth, N Brisset, F Weill, E Suard, C Masquelier, and L. Croguennec, Chem. Mater. 27 (8), (2015) 3009

Authors : B. Breitung, A. Schneider, P. Baumann, H. Sommer, J. Janek, T. Brezesinski
Affiliations : B. Breitung 1; A. Schneider 1; P. Baumann 2; H. Sommer 1,2; J. Janek 1,3; T. Brezesinski 1 1:Battery and Electrochemistry Laboratory (BELLA), Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany 2: BASF SE, 67056 Ludwigshafen, Germany 3: Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany

Resume : Nanoscale silicon (Si) is gaining significant attention as anode material for rechargeable lithium-ion batteries (LIBs) in recent years. Part of the reason for this is the high abundance of silicon and its exceptionally high theoretical gravimetric and volumetric capacity when fully lithiated (corresponding to Li22Si5). This capacity is much higher (approx. 4200 mAh/g or 9800 mAh/cm?) than that of graphite (372 mAh/g or 840-1200 mAh/cm?), which is currently the benchmark anode material in LIBs. Nevertheless, severe issues arise from large volume expansion upon alloying with Li. This volume change adversely affects the cyclability, thereby impeding the use of silicon anodes on a commercial level. The areal capacity of Si-containing anodes must be sufficiently high (>2 mAh/cm?) for ?real world? applications. Here, we report on a systematic study of Si-based electrodes with various loadings ? the goal was to find a good balance between stability and areal capacity. Furthermore, we describe a novel pyrolysis process to produce advanced carbon/silicon nanocomposites, able to dramatically improve cycling performance, including rate capability and capacity retention. Batteries using our carbon/silicon nanocomposites demonstrate specific capacities >2000 mAh/g at C/2 and areal capacities >2 mAh/cm? over hundreds of cycles. All materials employed were thoroughly analyzed via TEM, Raman spectroscopy, and galvanostatic charge/discharge measurements. In addition, we present insights into the cell ?breathing? and SEI formation from in operando AFM.

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Authors : Anna-Lisa Chaudhary,1 Natalia Aubrift,1 Klaus Taube,1 Giovanni Capurso,1 Guanqiao Li,2 Motoaki Matsuo,2 Shin-ichi Orimo,2 Claudio Pistidda,1 Thomas Klassen1 and Martin Dornheim1
Affiliations : 1Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Geesthacht , Germany; 2WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, Japan

Resume : Hydrogen technology can be incorporated into intermittent renewable energy systems to realize a complete clean, green energy harvesting and storage cycle. An efficient hydrogen storage system based on solid state hydrogen requires optimized material – tank systems to enable the storage of excess energy produced from sustainable energy sources to be used at times when direct production from renewables is not possible. High pressure tanks up to 700 bar are becoming more and more cost effective, thus opening up new potential for high pressure hydrogen storage materials. Complex hydrides are very promising hydrogen-storage materials, due to their high gravimetric and volumetric capacities. At moderate temperatures and pressures both borohydride and alanate systems have not yet met the criteria required for either mobile or stationary applications. However, these materials may have increased functionality once introduced into high pressure tank systems. Presented here are several complex hydride systems including light metal borohydrides composites with magnesium iron hydride, as well as lithium alanates combined with transition metal halide additives. Sorption properties of these systems will be discussed in relationship to the potential storage in high pressure hybrid tank systems.

Authors : Aadesh P. Singh and Bodh R. Mehta
Affiliations : Department of Physics, Indian Institute of Technology Delhi, Hauz, Khas, New Delhi110016, INDIA

Resume : Photoelectrochemical (PEC) splitting of water appears to be the most promising, economically viable and sustainable way for the production of hydrogen. Although, there are a series of new engineering strategies which have emerged towards development of highly efficient PEC water splitting for hydrogen generation. Yet, finding an optimal material for PEC cell is a very difficult task due to three main requirements in a single material system: 1) chemical stability 2) visible light absorption and 3) band edges matching to redox levels of water. This talk will summarize the major results obtained in the last years for photoelectrochemical water splitting. Our attention has been devoted to further modify the old workhorses viz. α-Fe2O3, TiO2 and BiVO4 etc by using various engineering strategies such as band structure engineering, material disordering, nano/micro engineering, surface/interface engineering to improve the performances of metal oxide-based materials, especially favoring the photoelectrochemical activity under simulated sunlight. Recently, a new engineering strategy, i.e., band re-alignment of BiVO4/TiO2 at the heterostructure was achieved by gas–phase modification technique of the top TiO2 layer which strongly promotes interfacial interaction at the junction and leads to an effective interfacial charge separation and charge transport. The modified BiVO4/TiO2 heterostructures exhibit significant enhancement of visible light absorption and improve the photoelectrochemical response.


Symposium organizers
Joanna K. BENDYNAMintres B.V.

De Nieuwe Erven 8 5431 NT Cuijk, The Netherlands
John F. ZEVENBERGENTNO - Netherlands / Organisation for Applied Scientific Research

Lange Kleiweg 137 2288 GJ Rijswijk The Netherlands
Rajeev AHUJA (Main Organizer)Department of Physics and Astronomy, Uppsala University

Box-516 SE-75120 Uppsala, Sweden
Sudip CHAKRABORTYApplied Materials Physics, Royal Institute of Technology (KTH) Stockholm

SE-10044 Stockholm, Sweden