Multifunctional Additive of Potassium Cinnamate Improve Crystallization and Passivate Defect for Perovskite Solar Cell with Efficiency Exceeding 22%

Perovskites with high film quality and low defect density are considered the essential condition for obtaining high‐performance perovskite devices. Herein, a simple and effective multifunctional additive of potassium cinnamate (PC) is doped into a perovskite precursor solution to improve the film quality and passivate the defect. It is revealed that the PC additives can react with the perovskite compositions, which affect the crystallization of perovskite and eventually form a high‐quality perovskite film. In addition, the PC additive still exists in the perovskite film after annealing, which effectively passivates the defects in perovskites. It is found that the PC‐doped devices exhibit improved photoluminescence intensity, increased carrier lifetimes, and reduced charge recombination. As a result, due to the improvement of film quality and efficient defect passivation, the doped device delivers a champion photoelectric conversion efficiency of 22.00%, which is significantly higher than 18.96% of the pristine device. The doped device maintains 86% of its maximum efficiency after aging for 5 months, which significantly improves long‐term stability compared to 62% of the original device. Herein, a new idea for designing efficient additives is provided to further enhance the performance and stability of perovskite solar cells.