Effective Passivation Enables High Performance CsPbI ₂ Br Perovskite Solar Cells

Abstract CsPbI ₂ Br perovskite solar cells have garnered significant attention due to their superior photo‐thermal stability and impressive photoelectric conversion efficiency. However, a substantial number of under‐coordinated Pb ²⁺ ions exist in CsPbI ₂ Br perovskite films, leading to severe non‐radiative recombination losses and the films exhibit poor humidity stability. Herein, a “two birds with one stone” strategy is proposed to introduce 2‐Amino‐N‐(2,2,2‐trifluoroethyl) acetamide hydrochloride (AAH) into the perovskite precursor solution, which can simultaneously enhance the photovoltaic performance and humidity stability of CsPbI ₂ Br perovskite solar cells. First, the electron‐donating groups in the AAH effectively passivate defects within the perovskite films, while the nitrogen‐containing functional groups in AAH can form hydrogen bonds with halide anions. Moreover, the fluorine atoms in the dopant contribute to the water‐repellent effect, thereby enhancing the humidity stability of devices. Additionally, that the addition of AAH is found markedly slowed down the crystallization rate of the perovskite, resulting in larger crystal grain sizes and substantially improved film quality. Devices with the optimal doping concentration achieve a champion efficiency of 17.82%. Notably, the unencapsulated devices retained over 90% of the initial efficiency after being stored in ambient air for 1000 h.