Mechanochemical Synthesis of High‐Entropy Perovskite toward Highly Sensitive and Stable X‐ray Flat‐Panel Detectors

Abstract Perovskites are attracting attention for optoelectronic devices. Despite their promise, the large‐scale synthesis of perovskite materials with exact stoichiometry, especially high‐entropy perovskites, has been a major challenge. Moreover, the difficulty in stoichiometry control also hinders the development of perovskite X‐ray flat‐panel detectors. Previous reports all employed simple MAPbI₃ as the active layer, while the performance still falls short of optimized single‐crystal‐based single‐pixel detectors. Herein, a scalable and universal strategy of a mechanochemical method is adopted to synthesize stoichiometric high‐entropy perovskite powders with high quality and high quantity (>1 kg per batch). By utilizing these stoichiometric perovskites, the first FA_0.9MA_0.05Cs_0.05Pb(I_0.9Br_0.1)₃‐based X‐ray flat‐panel detector with low trap density and large mobility–lifetime product (7.5 × 10⁻³ cm² V⁻¹) is reported. The assembled panel detector exhibits close‐to‐single‐crystal performance (high sensitivity of 2.1 × 10⁴ µC Gy_air⁻¹ cm⁻² and ultralow detection limit of 1.25 nGy_air s⁻¹), high spatial resolution of 0.46 lp/pixel, as well as excellent thermal robustness under industrial standards. The high performance in the high‐entropy perovskite‐based X‐ray FPDs has the potential to facilitate the development of new‐generation X‐ray‐detection systems.