Solvent‐Kinetics‐Regulated Anti‐Solvent Crystallization Enables Tunable‐Bandgap CsPbBr x Cl ₃ −x Perovskite Microcrystal Films for High‐Performance Photodetectors

All‐inorganic perovskite microcrystal films (MCFs) have emerged as promising candidates for next‐generation optoelectronic devices due to their excellent stability and outstanding photoelectronic performance. This work presents a solvent‐dynamics modulation strategy in which continuous antisolvent injection is employed to maintain a highly supersaturated precursor environment, thereby inhibiting Ostwald ripening. This approach not only prevents the dissolution of nucleation seeds and microcrystals but also enables precise control over dynamic nucleation and the directional growth of crystals. Consequently, it enables the scalable fabrication of high‑purity, highly crystalline CsPbBr x Cl 3 − x microcrystalline films with tunable thickness and composition. The resulting CsPbCl 3 microcrystal films exhibit thicknesses ranging from 12 to 47 µm and trap‐state densities as low as 3.514 × 10 9 cm − 3 , approaching bulk single‐crystal quality. Photoconductive detectors based on these films demonstrate excellent performance under 405 nm illumination, with a responsivity of 120 A/W, a detectivity of 1.87 × 10 1 3 Jones, and a linear dynamic range of up to 159 dB, outperforming most reported CsPbCl 3 devices. Moreover, this strategy is applicable to the synthesis of bandgap‐tunable (2.20–2.90 eV) CsPbBr x Cl 3 − x microcrystal films, which exhibit an ultralow bowing parameter (b = 0.064 eV) indicative of near‐ideal alloy‐mixing behavior. This work provides a universal and scalable solution for solution‐processed high‐quality, bandgap‐tunable perovskite microcrystal films, paving the way for their applications in broadband and weak‐light‐detection optoelectronics.