Objective: The aim of present work is to fabricate nanocrystalline p-Cu2S/n-FTO heterojunction photo detectors with high photosensitivity. Methods: Copper sulphide (Cu2S) is semiconductor compound belonging to I-VI group. Cost effective chemical method was used to synthesize thioglycerol capped Cu2S nanoparticles with improved optoelectronic and physical properties. These nanoparticles were investigated by ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM). Cu2S films were deposited on fluorine doped tin oxide (FTO) glass slides using cost effective dip coating method at different dip times and heat treated in air atmosphere. Wide band gap fluorine doped tin oxide, n-type semiconductor was used as transparent window material together with narrow band gap Cu2S, p-type semiconductor used as absorber layer in case of Cu2S/FTO heterojunction photo detectors under reverse biased mode and illumination. Results: Cu2S films were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Analysis by X-rays (EDAX), Mapping and Atomic Force Microscopy (AFM). Selected Area Electron Diffraction (SAED) images showed ring patterns indicating that Cu2S nanoparticles are polycrystalline in nature and spot patterns indicating that Cu2S nanoparticles are monocrystalline in nature. Conclusion: Previously, preparation of optoelectronic devices such as photo detectors using Cu2S films has not been reported. In this study, photo detectors having enhanced photosensitivity were prepared using Cu2S films. I-V characteristics of p-Cu2S/n-FTO heterojunctions under dark and illumination conditions were examined. It was observed that film conductivity decreases under dark condition and increases under illumination condition with increase in dip time in case of Cu2S/FTO heterojunction photo detectors.

Cadmium Sulphide (CdS) [II-VI group n-type semiconductor] and Copper Sulphide (Cu2S) [I-VI group p-type semiconductor] have large commercial applications like solar cell, gas sensor etc. Wide band gap CdS semiconductor was used as the transparent window material together with narrow band gap Cu2S semiconductor used as the absorber layer. Thioglycerol capped CdS and Cu2S nanoparticles were synthesized by using the non-aqueous chemical method at room temperature. CdS and Cu2S films were prepared on fluorine doped tin oxide (FTO) glass substrates by using the simple dip coating method at different dip times and heat treated in air. CdS and Cu2S nanoparticles were analysed by Ultraviolet-Visible absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM). CdS and Cu2S films were investigated by scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDAX), mapping and atomic force microscopy (AFM). Thicknesses of films were determined using laser profilometer. Previously, preparation of solar cells using CdS and Cu2S films deposited by dip coating method has not been reported. In this study, thin-film solar cells with p-n heterojunction having enhanced conductivity, excellent solar energy conversion efficiency, enhanced fill factor, low cost and easy fabrication were prepared to increase the quality of solar cells.