Materials for energy storage and conversion

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

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.

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.

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).

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

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.

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

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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