Improvement of the photoelectrical properties of chemical bath-deposited Sb2S3 thin films with low copper doping

Abstract

The chemical bath deposition method was used to prepare Cu-doped Sb2S3 thin films from complexes of Cu and Sb with triethanolamine. The as-deposited films with orange coloration had good adherence to the substrate. After an annealing treatment at 300 °C for 30 min in an Ar atmosphere, the resulting films acquired a brown color and exhibited the orthorhombic phase of Sb2S3 with the preferential growth of [hk0] grains. The Sb2S3 films were formed by rod-shaped nanoparticles, while the insertion of Cu ions in Sb2S3 promoted the formation of ribbon-like structures. The analysis of optical properties indicated the narrowing of bandgap energy from 1.9 to 1.8 eV due to the presence of Cu ions. In addition, the photoconductivity of the films increased from 8.3 × 10–6 to 30.5 × 10–6 Ω−1cm−1, while the photosensitivity factor was enhanced by more than 3 times. The performance of photovoltaic devices based on CdS/Sb2S3 and CdS/Cu:Sb2S3 heterojunctions were investigated. Compared with the device using a Sb2S3 layer, the one using a Cu-doped Sb2S3 layer exhibited an increase in open circuit voltage from 118.2 to 205 mV, short circuit current density from 0.14 to 0.34 mA/cm2 and conversion efficiency from 0.02 to 0.12%. The best performance was obtained by a photovoltaic device with a 500 nm Cu-doped Sb2S3 layer reaching an open circuit voltage of 226 mV, a short circuit current density of 0.94 mA/cm2 and conversion efficiency of 0.32%.