A Robust Hydrothermal Sulfuration Strategy toward Effective Defect Passivation Enabling 6.92% Efficiency Sb₂S₃ Solar Cells

Sulfuration is an efficient route for fabricating metal sulfides photovoltaic devices with high‐quality absorber layer, reduced S vacancy, and high device performance. However, traditional sulfuration processes reported thus far generally suffer from low activity, inert atmosphere, high operating temperature, and ineffective defect passivation, all of which increase manufacturing dangerousness, complicacy, and cost. Simultaneously fulfilling the goals of high reactivity, mild fabrication condition, and efficient defect passivation remain a major challenge for sulfuration, which may be addressed, as demonstrated herein, with the development of a (NH 4 ) 2 S‐induced hydrothermal sulfuration process in Sb 2 S 3 solar cells. By optimizing the hydrothermal sulfuration process through the use of different amounts of (NH 4 ) 2 S, an encouraging efficiency of 6.92% has been reached. In addition, the crystallinity of the Sb 2 S 3 film can be obviously improved even under the mild heating conditions (i.e., 160 °C, 120 min). Furthermore, only one hole trap can be identified for the Sb 2 S 3 device after hydrothermal sulfuration, and the trap density is significantly reduced. This innovative sulfuration system introduces a robust approach toward the goal of high‐efficiency metal sulfide solar cells compatible with simple hydrothermal process.