Effect of the junction barrier on current-voltage distortions in the Sb2Se3/ Zn(O,S) solar cells

A spike-like energy level alignment of Sb2Se3 absorber with a Zn(O,S) buffer layer is one of the crucial features for high efficiency solar cells based on Sb2Se3/Zn(O,S) heterojunction combination. Zn(O,S) has been considered a suitable substitute for the conventional CdS buffer layer in the Sb2Se3 solar cells. Because of the wider bandgap of Zn(O,S), more blue photons are collected, and consequently higher photocurrent is achieved. However, in some cases, distortions are observed in the current-voltage (J-V) characteristic in Sb2Se3 solar cells with Zn(O,S) buffer layer. In this paper, a simple approach is used to describe the effect of the junction barrier at Sb2Se3/Zn(O, S) interface on distortions in J-V curves. The results show that the junction barrier at Sb2Se3/Zn(O,S) interface is strongly affected by the conduction-band offset (CBO), whose height is varied depending on the carrier density of Zn(O,S), sulfur fraction in Zn(O,S), and operating temperature. The presence of a large junction barrier at Sb2Se3/Zn(O,S) interface leads to both red kink and crossover distortions, which are eliminated with increasing carrier density of Zn(O,S), increasing operating temperature, and decreasing sulfur content in Zn(O,S). The distortion-free and well-behaved J-V curves improve the performance of Sb2Se3/Zn(O,S) solar cells.