Stable 2D Perovskite Crystal Achieved by Large Lattice Distortion for Self‐Powered X‐Ray Detection

Abstract 2D Dion‐Jacobson (DJ) ferroelectric perovskites show outstanding potential for self‐powered X‐ray detection due to their high bulk resistivity and robust bulk photovoltaic effect (BPVE). Existing literature generally considered distortion of inorganic octahedral cages as detrimental to their photoelectric properties. Herein, this study demonstrates that larger distortion may be designed to attain more stable structures by promoting stronger hydrogen bonding between the inorganic cage and the organic chains, thus effectively suppressing ion migration. Furthermore, lattice distortion triggers the formation of electric dipoles, inducing spontaneous polarity and thereby augmenting the collection efficiency of photo generated charges. Leveraging the out‐of‐plane ferroelectric polarity of 4AMPPbI 4 , a self‐powered X‐ray detection is pioneered with the vertical structure, offering superior integration and assembly for practical applications compared to lateral‐structures. The resulting X‐ray detector exhibits exceptional performance, featuring a low noise current of 7.53 pA and an impressive self‐powered sensitivity of 234.74 µC Gy air −1 cm −2 at zero bias, surpassing all 2D self‐powered detectors in detection limits (6.6 nGy air s −1 ). Moreover, the device demonstrates commendable storage stability, retaining 95.9% initial sensitivity over 60 days under a 50V bias and 94.7% over 30 days in self‐powered mode.