The performance of the resulting In2S3/Cu2ZnSnS4 photovoltaic devices is on par with CdS/Cu2ZnSnS4 reference solar cells with similar values for short circuit currents and open circuit voltages, despite the overall quite low efficiency of the devices (~2%). Combinatorial photovoltaic device libraries with Al/ZnO/In2S3/Cu2ZnSnS4/Mo/SiO2 structure were built at optimal processing conditions to investigate the feasibility of the sputtered In2S3 buffer layers and for an accelerated optimization of the device structure. It is demonstrated that by tuning the sulfur partial pressure, phase pure β-In2S3 could be deposited using a broad range of substrate temperatures between 500☌ and ambient temperature. Here, In2S3 is investigated as a solar cell contact material utilizing a high throughput combinatorial screening of the temperature-flux parameter space, followed by a number of spatially-resolved characterization techniques.

However, the synthesis conditions for the sputter deposition of this material are not well established. A promising alternative to the commonly used CdS buffer layer in thin film solar cells that contain absorbers with lower electron affinity can be found in β-In2S3. The research and development of contact materials is difficult due to the inherent complexity that arises from its interactions at the interface with the absorber. An important part of the development of novel thin film solar cell technologies, that is still considered a bottleneck for both theory and experiment, is the search for alternative interfacial contact (buffer) layers. High-throughput computational and experimental techniques have been used in the past to accelerate the discovery of new promising solar cell materials. Maximum 94.8 % catalytic efficiency is obtained for the In2S3 nanocrystals using tetramethylammonium bromide (TMAB) ionic liquid. Furthermore, the adsorption driven catalytic and photocatalytic activity of as-prepared nanosized indium sulphide is confirmed by studying the degradation of crystal violet (CV) dye in presence of dark and visible light. Likewise, judicious choice of reaction temperature and precursors has a profound effect to obtain phase pure and morphology controlled nanocrystals. However in case of methylimidazolium bromides with longer pendant alkyl chains such as hexyl (C6), octyl (C8) or decyl (C10), nanoparticles of the tetragonal polymorph form. At 150oC, when no IL is used, pure tetragonal form of -In2S3 appears however in presence of Br, at the same reaction condition, a pure cubic phase crystallizes.

It is observed that crystallite size is significantly less when ILs are used compared to the synthesis without ILs keeping the other reaction parameters same. Selective tuning of size, shape, morphology and, most importantly, crystal phase of In2S3 is achieved by changing the alkyl side chain length, the H-bonding and aromatic -stacking ability of the 1-alkyl-3- methylimidazolium bromide ILs, Br (n=2,4,6,8 and 10). Phase tuned quantum confined In2S3 nanocrystals are accessible solvothermally using task-specific ionic liquids (ILs) as structure directing agents. The unique properties displayed by β-In 2 S 3 under different experimental pressure ranges can be reasonably explained by its crystalline structure observable from the microscopic observations of HRTEM and AFM images. However, when the sample is decompressed from the pressure below 10 GPa, the phase transition is reversible.

We determine that the phase transition of metallization is irreversible after decompression from the pressure above 40 GPa. When the pressure is released from 43.0 GPa, a single amorphous state is observed from Raman spectroscopy. A structural phase transition and a semiconductor-to-metal transition are observed at ∼7 GPa and ∼41.2 GPa, respectively. The high-pressure characteristics including structural phase transition, vibration and electronic transport of β-In 2 S 3 up to 43.0 GPa are determined using a diamond anvil cell (DAC)combined with AC impedance spectroscopy, Raman spectroscopy, atomic force microscopy (AFM)and high-resolution transmission electron microscopy (HRTEM).

Pushpal khadka