Epitaxial Growth of High-Quality Perovskite Heterojunctions for Direct-Conversion X-ray Detectors

Three-dimensional metal halide perovskites (3D-MHPs) have emerged as potential semiconductors for direct-conversion X-ray detectors. However, excessive ion migration in 3D-MHPs compromises device stability, hindering practical deployment. While perovskite heterojunctions have been explored to suppress ion migration, their effectiveness are often limited by challenges in fabricating high-quality heterojunctions, resulting in suboptimal charge collection compared to individual perovskite crystals. In this work, a liquid-phase interfacial array-epitaxial growth method was developed to construct high-quality MAPbBr₃/MAPbI₃ heterojunctions for direct X-ray detectors. The heterojunction crystal exhibit a serrated, ultrathick transition region that enhances X-ray response by increasing the interfacial contact area between MAPbBr₃ and MAPbI₃. Consequently, the fabricated detectors demonstrate stable operational performance, a high sensitivity of 0.99 × 10⁶ μC Gy_air^–1 cm^–2, and an ultralow detection limit of 0.56 nGy_air s^–1. Furthermore, the built-in electric field enables self-powered X-ray detection at 0 V bias, achieving a sensitivity of 1.16 × 10³ μC Gy_air^–1 cm^–2.