Although all‐inorganic perovskite solar cells (PSCs) demonstrate high thermal stability, cesium‐lead halide perovskites with high iodine content suffer from poor stability of the black phase (α‐phase). In this study, it is demonstrated that incorporating InCl3 into the host perovskite lattice helps to inhibit the formation of yellow phase (δ‐phase) perovskite and thereby enhances the long‐term ambient stability. The enhanced stability is achieved by a strategy for the structural reconstruction of CsPbI2Br perovskite by means of In3+ and Cl− codoping, which gives rise to a significant improvement in the overall spatial symmetry with a closely packed atom arrangement due to the crystal structure transformation from orthorhombic (Pnma) to cubic (Pm‐3m). In addition, a novel thermal radiation heating method that further improves the uniformity of the perovskite thin films is presented. This approach enables the construction of all‐inorganic InCl3:CsPbI2Br PSCs with a champion power conversion efficiency of 13.74% for a small‐area device (0.09 cm2) and 11.4% for a large‐area device (1.00 cm2).

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Cs x FA1–x PbI3 single crystals are expected to provide more excitement in optoelectronic applications, including photodetector, laser, light-emitting diode, etc. Herein, we aim to gain an in-depth understanding of the growth mechanisms of perovskite single crystal with various morphologies in view of microscopic dynamics by the combination of component, structure, and solvent engineering. A sequence of Cs x FA1–x PbI3 (0 ≤ x ≤ 0.14) perovskite single crystals with a dodecahedron morphology and tunable aspect ratio can be obtained by means of a solution-processed uniform-cooling approach. The optimized Cs0.1FA0.9PbI3 single crystals prepared in γ-butyrolactone mixed with dimethyl sulfoxide are theoretically and experimentally demonstrated to have superior performances, e.g., extremely higher long-term stability, lower trap density, and higher mobility. The broadband absorption, i.e., 300–910 nm, enables its application in near-infrared detection (880 nm), and the corresponding detector demonstrates higher responsivity at different light intensities and a fast photocurrent response (τ1 = 11 μs, τ2 = 10 μs). Equally important, we also explore the application of optimized Cs0.1FA0.9PbI3 single crystals with a tunable aspect ratio in an X-ray detector and the extremely high sensitivity (2772.1 μC Gyair –1 cm–2 under a bias of 150 V) demonstrates their good potential for radiation detection.

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