Phosphotungstic Acid Regulated Chemical Bath Deposition of Sb2S3 for High‐Efficiency Planar Heterojunction Solar Cell

Abstract Chemical bath deposition is a convenient method for preparing Sb 2 S 3 film which is considered as a promising photovoltaic material. However, impurity phases such as Sb 2 O 3 , SbOCl, Sb 2 (SO 4 ) 3 and Sb(OH) 3 are inevitably generated in this solution process. Herein, we demonstrate that phosphotungstic acid in the precursor solution is able to suppress the formation of oxide and oxyhalide by‐products, leading to considerably optimized composition and crystallinity for solar cell applications. With this method, a remarkable improvement of power conversion efficiency from 1.91 % to 4.61 % is obtained, which is also the highest efficiency in planar heterojunction solar cells by solution processed Sb 2 S 3 absorber layer.