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

•A facile two-step spin-coating procedure has been developed to prepare high-quality CsPbBr3 perovskite films.•Perovskite solar cells (PSCs) based on the resulting films afford a maximum power conversion efficiency of 8.11%.•The unencapsulated PSC devices exhibit excellent thermal and humidity stability at ambient conditions. 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. [Display omitted] A facile two-step spin-coating method is developed to prepare high-quality CsPbBr3 films. The application of the films in planar perovskite solar cells leads to a maximum power conversion efficiency of 8.11% with excellent stability.