High Photosensitivity Nanocrystalline p-Cu2S/n-FTO Heterojunction Photodetectors Prepared by Dip Coating Method

Abstract

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.