Hot‐Press Welding Enables High‐Quality 2D/3D/2D Perovskite Heterojunction Wafers for Sensitive and Stable X‐Ray Detectors

Abstract Metal halide perovskites (MHPs) demonstrate bright prospects as next‐generation X‐ray detectors owing to their strong X‐ray absorption capability and large mobility‐lifetime products. However, their performance is compromised by large dark currents and ion migration, which constitute the primary challenges hindering practical applications. Here, a hot‐press welding strategy is proposed to simultaneously suppress dark current and mitigate ion migration through the construction of 2D/3D/2D MHP heterojunctions. The developed 2D/3D/2D MHP heterojunction wafers exhibit high purity, a pinhole‐free morphology, mirror‐like surfaces, and robust interfacial bonding. This methodology is further demonstrated to be generalizable across diverse MHP heterojunction wafer systems. Notably, the high‐quality 2D/3D/2D MHP heterojunction wafers achieve exceptional X‐ray detection performance, delivering a sensitivity of 4286.9 µC Gy air −1 cm −2 and a low detection limit of 44.38 nGy air s −1 . Specifically, the heterojunction wafers exhibit a fourfold enhancement in sensitivity compared to pure PEA 2 PbBr 4 wafers. Furthermore, ion migration‐induced dark current drift is effectively suppressed to 4.84 × 10 −15 A cm −1 s −1 V −1 even under high electric fields of 40 V. This research establishes a hot‐press welding strategy enabling wafer‐scale fabrication of high‐quality MHP heterojunctions with mirror‐like surfaces and robust bonding interface for X‐ray detection, thus advancing the practical deployment of MHP‐based X‐ray detectors.