Defect Compensation and Lattice Stabilization Enables High Voltage Output in Tin Halide Perovskite Solar Cells

Abstract

AbstractTin halide perovskite solar cells (PSCs) are regarded as the most promising lead‐free alternatives for photovoltaic applications. However, they still suffer from uncompetitive photovoltaic performance because of the facile Sn2+ oxidation and Sn‐related defects. Herein, a defect and carrier management strategy by using diaminopyridine (DP) and 4‐bromo‐2,6‐diaminopyridine (4BrDP) as multifunctional additives for tin halide perovskites is reported. Both DP and 4BrDP induced strong interaction with tin perovskites by coordinate bonding and N─H···I hydrogen bonding, which greatly suppresses the micro‐strain and Urbach energy of tin halide perovskite films. The strong hydrogen bonding inhibits the formation of I3− and related defect density. Meanwhile, the electron‐donor species of halogen bond in 4BrDP provides higher reactivity of 2 and 6 sites, which indicates stronger passivation ability with tin halide perovskites. These advances enable a champion power conversion efficiency (PCE) of 13.40% in 4BrDP‐processed devices with remarkable improvement in both open‐circuit voltage (Voc) of 881 mV and fill factor (FF) of 71.26%. The 4BrDP devices retain 91% and 82% of the pristine PCE after 2000 h storage in N2 atmosphere and 1000 h under 85 °C, respectively. Therefore, this work provides new insight into molecular design for high‐performance and stable lead‐free optoelectronics.