Significant increase in efficiency and limited toxicity of a solar cell based on Sb2Se3 with SnO2 as a buffer layer

Antimony selenide (Sb2Se3) thin films are attractive light-absorbing materials used in low-cost and highly efficient thin-film solar cells. In order to increase the efficiency of Sb2Se3 solar cells based on a tin oxide (SnO2) buffer layer, an ultrathin cadmium sulfide (CdS) film was introduced at the interface between the fluorine doped SnO2 glass (FTO) and the SnO2 film. Different thicknesses of the CdS/SnO2 compound buffer layers were used to form p–n junctions with the Sb2Se3 film. The ultrathin CdS layer not only increased the carrier connection and transport, but also decreased the conduction band offset and grain boundary density of the Sb2Se3 film. Lastly, an efficiency of 5.27% for the FTO/CdS (10 nm)/SnO2 (40 nm)/Sb2Se3/Au solar cells was obtained, which is higher than the reported highest efficiency of Sb2Se3 solar cells based on a SnO2 buffer layer.