Cesium Cyclopropane Acid‐Aided Crystal Growth Enables Efficient Inorganic Perovskite Solar Cells with a High Moisture Tolerance
Yaochang Yue, Rongshen Yang, Weichao Zhang, Qian Cheng, Huiqiong Zhou, Yuan Zhang
Abstract
Abstract While all‐inorganic halide perovskites (iHPs) are promising photovoltaic materials, the associated water sensitivity of iHPs calls for stringent humidity control to reach satisfactory photovoltaic efficiencies. Herein, we report a moisture‐insensitive perovskite formation route under ambient air for CsPbI 2 Br‐based iHPs via cesium cyclopropane acids (C 3 ) as a compound introducer. With this approach, appreciably enhanced crystallization quality and moisture tolerance of CsPbI 2 Br are attained. The improvements are attributed to the modified evaporation enthalpy of the volatile side product of DMA‐acid initiated by Cs‐acids. As such, the water‐involving reaction is directed toward the DMA‐acids, leaving the target CsPbI 2 Br perovskites insensitive to ambient humidity. We highlight that by controlling the C 3 concentration, the dependence of power conversion efficiency (PCE) in CsPbI 2 Br devices on the humidity level during perovskite film formation becomes favorably weakened, with the PCEs remaining relatively high (>15 %) associated with improved device stability for RH levels changed from 25 % to 65 %. The champion solar cells yield an impressive PCE exceeding 17 %, showing small degradations (<10 %) for 2000 hours of shell storage and 300 hours of 85/85 (temperature/humidity) tests. The demonstrated C 3 ‐based strategy provides an enabler for improving the long‐sought moisture‐stability of iHPs toward high photovoltaic device performance.