High‐Sensitivity and Stable X‐Ray Detection with Low Detection Limit Enabled by a Short‐Interlayer‐Spaced 2D Bilayer Dion‐Jacobson Perovskite

Abstract 2D hybrid organic–inorganic perovskites (HOIPs) show great promise for direct X‐ray detection by effectively suppressing ion migration. However, achieving high sensitivity, low detection limit, and high working stability simultaneously remains challenging for practical application. Here, this challenge is addressed by exploiting a 2D bilayer Dion‐Jacobson (DJ) HOIP, (AMP)MAPb 2 I 7 (AMP = (4‐aminomethyl)piperidine, MA = methylamine), featuring a short interlayer distance (4.125 Å). The short interlayer spacing combined with thick inorganic bilayer facilitates efficient charge carrier transport, while strong interlayer interactions inherent to DJ motif block ion migration and enhance structural rigidity, synergistically enabling sensitive, low‐dose X‐ray detection with xceptional stability. Consequently, X‐ray detectors based on high‐quality (AMP)MAPb 2 I 7 single crystals achieve a high sensitivity of 7505 µ C Gy air −1 cm −2 and an ultralow detection limit of 39 nGy air s −1 at 100 V bias, outperforming most reported 2D HOIP detectors. Strikingly, the device exhibits a minimal baseline drift of 5.47 × 10 −6 nA cm −1 s −1 V −1 as well as excellent long‐term working stability under high‐flux X‐ray irradiation and large bias voltage. This work not only presents a promising X‐ray detection material but also provides insights into future fabrication of high‐performance HOIP X‐ray detectors.