Efficient Surface‐Defect Passivation by Sulfurous‐Acyl‐Included Small Molecule for High‐Performance Perovskite Photovoltaics

Perovskite photovoltaics have drawn tremendous attention due to their excellent photoelectric performance and possess promising potential in the field of renewable energy. Although the photoelectric conversion efficiency of perovskite solar cells has made a quantum leap, stability is still a limitation to its long‐term development and has become the main issue that needs to be solved urgently. The defects in the perovskite films and at the grain boundaries are important factors affecting the stability of perovskite photovoltaics. It is reported that the surface defect of the perovskite film is two to four orders of magnitude higher than the bulk defect. Herein, 4‐bromobenzenesulfonyl chloride to modify the surface defects of perovskite films is introduced. Through the interaction between S = O in 4‐bromobenzenesulfonyl chloride and the bare Pb 2+ in the perovskite film, the crystal quality of the perovskite film is significantly improved and the surface defects are effectively passivated. The optimized device achieves a champion power conversion efficiency of 21.84%, and the efficiency can retain 92% of the initial value after 1200 h. This finding provides a method to improve the device performance of perovskite solar cells.