Suppression of Ion Migration With a Composite Polymer Film in Perovskite Single‐crystal Photodetectors for Sensitive and Stable X‐Ray Imaging

ABSTRACT Organic‐inorganic halide perovskite materials have demonstrated exceptional potential for X‐ray detection due to their high X‐ray attenuation coefficient and large mobility‐lifetime product. However, severe ion migration leads to signal current baseline drift and increased noise, limiting the imaging performance. In this work, we report a new mechanism by introducing a lattice‐matched MABr–PMMA composite polymer film, fabricated through a solution‐processed epitaxial growth method. The formation of a PN heterojunction, enabled by electron donation from the MABr component, not only provides efficient surface passivation but also effectively suppresses ion migration in MAPbBr 3 perovskite single crystals (SCs). Consequently, the X‐ray detector exhibits an ultralow baseline drift of 2.4 × 10 −6 nA cm −1 s −1 V −1 under a high electric field of 1000 V cm −1 , comparable to that of 2D perovskite SCs. It also achieves a high sensitivity of 1.46 × 10 5 µC Gyair −1 cm −2 and a low detection limit of 51.2 nGyair s −1 . Moreover, the device also demonstrates excellent stability and reliability under various demanding operational conditions, including high‐dose irradiation, high‐temperature, long‐term high biasing, and long‐term air exposure storage. In addition, the detector delivers high‐resolution and real‐time X‐ray imaging, highlighting its potential for high‐resolution integrated X‐ray imaging array applications.