Efficient and stable planar all-inorganic perovskite solar cells based on high-quality CsPbBr₃ films with controllable morphology

All-inorganic cesium lead bromide (CsPbBr₃) perovskite is attracting growing interest as functional materials in photovoltaics and other optoelectronic devices due to its superb stability. However, the fabrication of high-quality CsPbBr₃ films still remains a big challenge by solution-process because of the low solubility of the cesium precursor in common solvents. Herein, we report a facile solution-processed approach to prepare high-quality CsPbBr₃ perovskite films via a two-step spin-coating method, in which the CsBr methanol/H₂O mixed solvent solution is spin-coated onto the lead bromide films, followed by an isopropanol-assisted post-treatment to regulate the crystallization process and to control the film morphology. In this fashion, dense and uniform CsPbBr₃ films are obtained consisting of large crystalline domains with sizes up to microns and low defect density. The effectiveness of the resulting CsPbBr₃ films is further examined in perovskite solar cells (PSCs) with a simplified planar architecture of fluorine‒doped tin oxide/compact TiO₂/CsPbBr₃/carbon, which deliver a maximum power conversion efficiency of 8.11% together with excellent thermal and humidity stability. The present work offers a simple and effective strategy in fabrication of high-quality CsPbBr₃ films for efficient and stable PSCs as well as other optoelectronic devices.