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

[Display omitted] • A novel chemical etching for Sb 2 (S,Se) 3 film by KF solution was first proposed. • Properties of Sb 2 (S,Se) 3 film and interfacial defects of device are improved. • Mild gradient band gap is formed, promoting the carries transfer between the absorber and hole transport layer. • The device efficiency based on chemical etched Sb 2 (S,Se) 3 film reaches 9.58%. Recently, due to its excellent photovoltaic features, Sb 2 (S,Se) 3 is regarded as a promising photovoltaic absorber material. However, the interfacial property of Sb 2 (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 Sb 2 (S,Se) 3 film prepared by hydrothermal method to investigate the effects of surface modification on the properties of the Sb 2 (S,Se) 3 film as well as its solar cell performance. Interestingly, the chemical etching performed on Sb 2 (S,Se) 3 film using potassium fluoride aqueous solution not only improved the crystallinity and uniformity of Sb 2 (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 Sb 2 (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 Sb 2 (S,Se) 3 film as well as a viable alternative method for reducing interfacial defects in other chalcogenide semiconductors. [ABSTRACT FROM AUTHOR]