Strategies for the preparation of high-performance inorganic mixed-halide perovskite solar cells

Inorganic halide perovskites have attracted significant attention in the field of photovoltaics (PV) in recent years due to their superior intrinsic thermal stability and excellent theoretical power conversion efficiency (PCE). CsPbI₃ with a bandgap of ∼1.7 eV is considered to be the most potential candidate for PV application. However, bulk CsPbI₃ films exhibit poor phase stability. The substitution of some iodide ions with bromide/chloride in CsPbI₃ results in the formation of mixed-halide CsPbX₃ perovskites, which exhibit a good balance between phase stability and efficiency. The halogen-tunable mixed-halide inorganic perovskites have a bandgap matching the sunlight region and show great potential for application in multi-junction tandem and semitransparent solar cells. Herein, the progress of mixed-halide CsPbX₃ PSCs is systematically reviewed, including CsPbI _x Br _y Cl_3-x-y - and CsPbIBr₂-based IPSCs. In the case of CsPbIBr₂ IPSCs, we introduce the low-temperature deposition of CsPbIBr₂ films, doping methods for the preparation of high-quality CsPbIBr₂ films and strategies for improving the performance of solar cells. Furthermore, the mechanism of crystallization/interface engineering for the preparation of high-quality CsPbIBr₂ films and efficient solar cells devices is emphasized. Finally, the development direction of further improving the PV performance and commercialization of mixed-halide IPSCs are summarized and prospected.