Chemical etching induced surface modification and gentle gradient bandgap for highly efficient Sb2(S,Se)3 solar cell

Recently, due to its excellent photovoltaic features, Sb2(S,Se)3 is regarded as a promising photovoltaic absorber material. However, the interfacial property of Sb2(S,Se)3-based solar cell still needs to be studied due to limited efficiency improvement resulting from interfacial defects. In this paper, we focus on Sb2(S,Se)3 film prepared by hydrothermal method to investigate the effects of surface modification on the properties of the Sb2(S,Se)3 film as well as its solar cell performance. Interestingly, the chemical etching performed on Sb2(S,Se)3 film using potassium fluoride aqueous solution not only improved the crystallinity and uniformity of Sb2(S,Se)3 film but also decreased the interfacial defects, leading to a reduced carrier recombination loss of the device. As a result of chemical modification, the current density and fill factor of Sb2(S,Se)3-based superstrate structure solar devices were improved, resulting in maximum efficiency of 9.58%. Overall, this research offers a comprehensive understanding of the hydrothermally processed Sb2(S,Se)3 film as well as a viable alternative method for reducing interfacial defects in other chalcogenide semiconductors.