Defect Passivation for High Performance Lead‐Free Tin Halide Perovskite Solar Cells

Tin perovskite solar cells (TPSCs) have attracted considerable research attentions as promising lead‐free perovskite photovoltaics due to their ideal bandgap structure and excellent optical properties. However, the fast crystallization process, chemical instability, and high concentration of defective centers induce severe carrier recombination and affects the device performance. Therefore, effective passivation of this high concentration of defects is particularly critical to enhance their photovoltaic performance and stability. In this study, a π ‐conjugated molecule, 4‐aminobenzonitrile (AZ) was introduced into the tin perovskite precursor. The interaction between AZ and Sn ²⁺ can delay the crystal growth and achieve secondary crystallization. In addition, the introduction of para‐amino group in AZ exhibited symmetrical electron cloud characteristics, which effectively reduces the recombination of defects in perovskite. A series of photophysical characterizations have proved that the defect concentration in the AZ film was significantly reduced, and the carrier separation and extraction were greatly improved. Finally, the device showed a power conversion efficiency enhancement from 9.77% to 11.09%, together with notably improved device stability.