Evaluating physio-chemical and optoelectronic properties of CuInSn(S,Se)4 thin films and its photoelectrochemical cell application

In this work, CuInSn(S,Se)₄ (CITSSe) thin films were synthesized using a self-organized, facile arrested precipitation technique at room temperature. The variation in physio-chemical and optoelectronic properties of the thin films was systematically studied by probing the In³⁺ ion concentration. The synthesized CITSSe thin films exhibited significant improvements in optostructural and optoelectronic properties. Optical absorption studies confirmed a direct allowed transition with a band gap energy ranging from 1.40 to 1.54 eV. X-ray diffraction analysis verified the formation of a cubic crystal structure, while a peak shift from (220) to (511) with increasing In³⁺ ion concentration indicated successful incorporation of In³⁺ ions into the CITSSe matrix. A notable modification in surface morphology was observed, transitioning from nanocubes to nanocorals from sample I₀ to I₄. The elemental composition of the CITSSe thin films was confirmed through energy-dispersive X-ray spectroscopy. Furthermore, the nanocrystalline nature of the pentanary CITSSe thin films was validated using high-resolution transmission electron microscopy and selected area electron diffraction patterns. Photoelectrochemical and impedance characteristics were analyzed using a two-electrode cell configuration, where the highest photoelectrochemical efficiency of 0.61 % was achieved for the bare CITSSe thin film, exhibiting low charge transfer resistance.