Stabilizing the black phase of cesium lead halide inorganic perovskite for efficient solar cells

Inorganic perovskite cesium lead halide is extensively studied because of its potential in improving the thermal stability of perovskite materials. However, the tolerance factor of this type of perovskite is near the critical value, which leads to phase instability. The optoelectronic active black phases (α, β, and γ phases of CsPbI₃) are metastable at room temperature, which can be easily transferred into an optoelectronic inactive yellow phase (γ-CsPbI₃). This review highlights recent progress in stabilizing the black phase for efficient and stable perovskite solar cells.