A 0D/3D Heterostructured All‐Inorganic Halide Perovskite Solar Cell with High Performance and Enhanced Phase Stability

Abstract Although organic–inorganic hybrid perovskite solar cells (PVSCs) have achieved dramatic improvement in device efficiency, their long‐term stability remains a major concern prior to commercialization. To address this issue, extensive research efforts are dedicated to exploiting all‐inorganic PVSCs by using cesium (Cs)‐based perovskite materials, such as α‐CsPbI₃. However, the black‐phase CsPbI₃ (cubic α‐CsPbI₃ and orthorhombic γ‐CsPbI₃ phases) is not stable at room temperature, and it tends to convert to the nonperovskite δ‐CsPbI₃ phase. Here, a simple yet effective approach is described to prepare stable black‐phase CsPbI₃ by forming a heterostructure comprising 0D Cs₄PbI₆ and γ‐CsPbI₃ through tuning the stoichiometry of the precursors between CsI and PbI. Such heterostructure is manifested to enable the realization of a stable all‐inorganic PVSC with a high power conversion efficiency of 16.39%. This work provides a new perspective for developing high‐performance and stable all‐inorganic PVSCs.