Hot-casting process assisted air-compatible low-temperature CsPbI2Br perovskite solar cells

High-performance CsPbI2Br perovskite solar cells (PSCs) often use DMF/DMSO mixed solvents to obtain sufficient film thickness due to the solubility limitations of bromide in DMF. However, the need for high-temperature annealing to form the photoactive α-CsPbI2Br and the difficulty of completely removing DMSO greatly limit its application prospects for commercial. Herein, we report a low-temperature deposition strategy for obtaining high-performance CsPbI2Br-based devices without DMSO in an open-air environment. By adding CsPbI2Br/DMF solution dropwise to a substrate preheated at 80 ℃, the rapid volatilization of DMF will help drive heterogeneous nucleation with lower energy barriers, thereby increasing the thickness of CsPbI2Br film. Meanwhile, the α-CsPbI2Br microcrystals formed during the spin-coating process also facilitated the formation of high-quality perovskite films. Consequently, the efficiency of optimized CsPbI2Br-based PSC is significantly increased to 16.44%. To our knowledge, this efficiency value is the highest among all CsPbI2Br PSCs based on pure DMF solution.