Cadmium Sulphide Thin Film with ZnO:Bi Buffer Layer for Heterojunction Solar Cell Window Layer Applications

Solar cells need improved efficiencies to reduce electricity costs, which can be achieved through a window layer. Candidate window layer films were fabricated using CdS and bismuth doped zinc oxide (ZnO:Bi). Analyses on the structural, electrical and optical properties were conducted. CdS films with ZnO:Bi buffer layer displayed ohmic contact behavior, high conductivity and low resistivity. Optical properties showed wider band gaps (2.49 - 3.29 eV) than silicon (1.1 eV), low reflectance and high transmittance, in the visible light range, and refractive indices lower than Si. Results confirm that films made of CdS and ZnO:Bi can potentially improve solar cell efficiency.