Topological Semimetal Enhancement Enables Ultra‐Sensitive Flat‐Panel X‐Ray Imaging in Hydrogen‐Bonded MAPbI ₃ /(TaSe ₄ ) ₂ I Wafers

Although three‐dimensional metal halide perovskites are promising for highly sensitive X‐ray detection, ion migration severely compromises their stability and sensitivity. Conventional heterojunction designs often suppress ion migration at the cost of impeding carrier transport. Here, we report a novel strategy to construct a hydrogen bond‐mediated heterojunction between MAPbI 3 perovskite and the topological Weyl semimetal (TaSe 4 ) 2 I. Interfacial N─H⋯I hydrogen bonds effectively anchor mobile ions, significantly suppressing ion migration, while the topological surface states of (TaSe 4 ) 2 I enable ultrahigh carrier mobility. The gradient pressing method enables scalable fabrication of large‐area, high‐quality heterojunction wafers. This heterojunction exhibits a remarkable 136% increase in ion migration activation energy (0.604 eV) and an ultra‐low dark current drift (1.83 × 10 −4 nA cm −1 s −1 V −1 ). Critically, the topology‐enhanced photoconductive gain mechanism yields an outstanding steady‐state sensitivity of (1.03 ± 0.21)× 10 6 µC Gy −1 cm −2 and a low detection limit of 76.5 nGy s −1 . Finally, the resulting X‐ray imager based on a TFT backplane achieves a spatial resolution of 2.1 lp mm −1 (0.42 lp/pixel). Our work provides an effective strategy for the further development of novel scalable and ultra‐sensitive flat‐panel X‐ray detectors.