Because of its stable chemical properties and wide band gap, CsPbCl3 perovskite has shown great application prospects in ultraviolet photodetectors (UPDs). However, the poor solubility of CsCl in organic solvents impedes the fabrication of high-quality CsPbCl3 films. Herein, we introduced an A-site substitute route for fabricating a high-quality CsPbCl3 microcrystalline (MC) film by spin-coating cesium acetate on a MAPbCl3 MC film followed by a high-temperature annealing process. To enhance the device performance of the FTO/SnO2/CsPbCl3 MCs/carbon structure UPD, a pressure-assisted annealing strategy was carried out, which reduced the void density and surface roughness of the microcrystal film. Finally, our optimized PDs showed high device performances with an on/off ratio of 6 × 104, a responsivity of 0.13 A W–1, a detectivity of as high as 1.07 × 1012 Jones, and a rise/fall time of 10/24 μs. Moreover, our unpacked PDs showed good storage and light stability. Our results lay a foundation for the application of all inorganic perovskite in the ultraviolet region.

Lead halide perovskite materials have shown great application potential in the field of optoelectronics, but solution‐phase processing of all‐inorganic wide‐bandgap perovskite materials, especially CsPbCl3, faces great challenges due to the low solubility of the raw materials. Here, a solution‐processing of CsPbClxBr3−x perovskite micro/nanostructures (PMNSs) via a two‐step ion‐exchange method is reported. The halide composition and the surface morphology of the CsPbClxBr3−x PMNS are regulated by tailoring the reaction time of halide exchange, and the photodetectors (PDs) based on the CsPbBr2.25Cl0.75 PMNS exhibit best device performance. The CsPbBr2.25Cl0.75 PMNS PDs show excellent self‐powered performance with an open‐circuit voltage of 1.1 V, an on‐off ratio of up to 106, a responsivity of 0.31 A W−1, a detectivity of 2.87 × 1012 Jones, and a linear dynamic range of 130 dB. These excellent performances are attributed to the unique device structure in which large‐sized micro‐nanocrystals in the bottom layer guarantee the generation of carriers, and the nanowires on top penetrate the carbon and benefit from excellent contact between the perovskite and the electrode, thus resulting in a good device performance.

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