Room‐Temperature‐Grown FAPb 0.5 Sn 0.5 I 3 Polycrystalline Thick Films for Self‐Powered X‐Ray Detectors With High Sensitivity and Low Detection Limit

ABSTRACT Perovskite polycrystalline thick films are promising for x‐ray detection and imaging, yet the simultaneous realization of high sensitivity and a low detection limit remain difficult due to the trade‐off between transport and ion migration. Herein, we report the preparation of FAPb 0.5 Sn 0.5 I 3 (FA = CH(NH 2 ) 2 ) perovskite polycrystalline thick films with negligible Sn 2+ oxidation at room temperature by solvent engineering. The as‐prepared films deliver exceptional carrier transport properties, as evidenced by an ultralong carrier diffusion length ( L D ) of 58 µm. Moreover, the high ion migration activation energy ( E a ) of 0.67 eV endows the detectors with suppressed dark current and a minimal drift of 2.09 × 10 −5 nA cm −1 s −1 V −1 . Collectively, these merits result in self‐powered x‐ray detectors with both high sensitivity of 3.88 × 10 3 µC Gy air −1 cm −2 and an ultralow detection limit of 0.93 nGy air s −1 . Our work may promote the development of stable and low‐dose‐rate perovskite x‐ray imaging.