Suppressing the Light‐Soaking Effect of CsPbI 2 Br‐Based p–i–n Perovskite Solar Cells

The light‐soaking (LS) effect has been reported to limit the accuracy and stability of device power output of perovskite solar cells (PSCs) and it is significant to develop effective approaches and strategies to eliminate the LS effect in PSCs. There are very few reports on suppressing the LS effect in CsPbI 2 Br‐based all‐inorganic PSCs. Herein, a method to eliminate the LS effect by synchronous passivation of anionic and cationic defects in CsPbI 2 Br perovskite film is demonstrated. The 4‐(chlorosulfonyl)benzoic acid (CSBA) is added into perovskite precursor and the in situ generation of I 3 − effectively passivates the anionic halogen vacancy defects in CsPbI 2 Br. In the meantime, the Lewis base groups on CSBA coordinate with Cs + and Pb 2+ to passivate the cationic defects. This zwitterionic passivation effect of CSBA remarkably cuts off the path of defect‐induced charge recombination and thus eliminates the LS effect. This work offers a deep opinion for future researchers to modulate the LS effect of all‐inorganic PSCs.