Controlled n‐Doping in Air‐Stable CsPbI2Br Perovskite Solar Cells with a Record Efficiency of 16.79%

Abstract Cesium‐based inorganic perovskites, such as CsPbI 2 Br, are promising candidates for photovoltaic applications owing to their exceptional optoelectronic properties and outstanding thermal stability. However, the power conversion efficiency of CsPbI 2 Br perovskite solar cells (PSCs) is still lower than those of hybrid PSCs and inorganic CsPbI 3 PSCs. In this work, passivation and n‐type doping by adding CaCl 2 to CsPbI 2 Br is demonstrated. The crystallinity of the CsPbI 2 Br perovskite film is enhanced, and the trap density is suppressed after adding CaCl 2 . In addition, the Fermi level of the CsPbI 2 Br is changed by the added CaCl 2 to show heavy n‐type doping. As a result, the optimized CsPbI 2 Br PSC shows a highest open circuit voltage of 1.32 V and a record efficiency of 16.79%. Meanwhile, high air stability is demonstrated for a CsPbI 2 Br PSC with 90% of the initial efficiency remaining after more than 1000 h aging in air.