TA-RH regulate the growth mechanism of CsPbIBr₂ inorganic perovskite thin films for photovoltaic applications

CsPbIBr₂ inorganic perovskite films have become one of the photovoltaic materials with great development potential due to their excellent wet thermal stability and excellent photovoltaic performance, as well as relatively simple preparation process. However, the preparation process and film-forming mechanism of CsPbIBr₂ thin films are still immature, and the films are prone to structural defects such as pinholes and grain boundaries, resulting in poor film-forming quality. Here, in this study, the controlled preparation of CsPbIBr₂ films was achieved under additive-free conditions by regulating the humidity and temperature during the film-forming process in combination with the substrate preheating treatment (SPT) strategy, and the ambient temperature–relative humidity influence on the grain growth of CsPbIBr₂₂ was systematically explored to achieve the highest film coverage at 80–90 °C, and different surface topographies were obtained under different environments, CsPbIBr₂ films with different surface morphology, crystallinity, light absorption properties, and grain size were obtained under different environments. Notably, the CsPbIBr₂ films prepared at 20 °C, RH: 10% exhibited smooth and flat surface morphology, with larger grain size and fewer grain boundaries, and the corresponding carbon-based PSC devices achieved excellent photovoltaic performance, with the Jsc: 10.98 mA/cm², Voc: 1.16 V, FF 0.55, and PCE of 6.95%.