Solvent-engineering toward CsPb( IxBr1-x) 3 films for high-performance inorganic perovskite solar cells

All-inorganic perovskites have aroused great interest recently because of their prominent photoelectric properties and thermal stability for stable, highly efficient perovskite solar cells. Herein, a two-step multiple spin coating method has been developed for the first time to prepare cesium halide perovskite films. In particular, dimethyl sulfoxide (DMSO) is introduced into CsBr/methanol precursor solution to increase the solubility of CsBr; in the meantime, it can also remarkably influence the morphologies, optical properties and photovoltaic performance of CsPb(IxBr1-x)(3) (0 < x < 1) films. By regulating the content of DMSO, as high as 13.27% power conversion efficiency (PCE) has been achieved with a steady-state PCE of 12.5% under optimal conditions, which can maintain 98% of the initial PCE for 480 h under ambient conditions without encapsulation. The synergistic effect of the solvent-engineering method can provide a new access for good quality all-inorganic perovskite thin films for high performance optoelectronic devices.