Methylammonium Iodide-Mediated Controlled Crystal Growth of CsPbI2Br Film for Efficient and Stable All-Inorganic Perovskite Solar Cells

High-quality perovskite film is a key aspect contributing to high photovoltaic performance of all-inorganic perovskite solar cells. We herein demonstrate that the addition of methylammonium iodide (MAI) influences effectively on both tailored film morphology and precise crystal growth to construct a high-quality CsPbI2Br films. It is found that the MAI additive retards the crystallization kinetics to control the inorganic perovskite films to be highly crystalline α-CsPbI2Br structure consisting of micro-sized grains and reduced defect density. The optimal MAI additive (10 wt%) achieves 10.40% of power conversion efficiency (PCE) of the CsPbI2Br-based all-inorganic perovskite solar cells, which is >30% enhancement from 6.95% of the pristine one. The solar cells employing the MAI additive possess high operational and thermal stability, retaining > 70% of original PCE after ageing for 1500 h in ambient atmosphere, and under continuous heating at 85 °C for 30 h, respectively. The photovoltaic performance under indoor light source was also examined using white light emitting diode (6500 K, 1000 lux), showing promising PCEs of 23.51% with a stabilized power output of 21.15%.