Gas-Phase Construction of Compact Capping Layers for High-Performance Halide Perovskite X-Ray Detectors

Halide perovskites have emerged as promising materials for X-ray detection with exceptional properties and reasonable costs. Among them, heterostructures between 3D perovskites and low-dimensional perovskites attract intensive studies of their advantages due to low-level ion migration and decent stability. However, there is still a lack of methods to precisely construct heterostructures and a fundamental understanding of their structure-dependent optoelectronic properties. Herein, a gas-phase method was developed to grow 2D perovskites directly on 3D perovskites with nanoscale accuracy. In addition, the larger steric hindrance of organic layers of 2D perovskites was proved to enable slower ion migration, which resulted in reduced trap states and better stability. Based on MAPbBr₃ single crystals with the (PA)₂PbBr₄ capping layer, the X-ray detector achieved a sensitivity of 22,245 μC Gy_air^-1 cm^-2, a response speed of 240 μs, and a dark current drift of 1.17 × 10^-4 nA cm^-1 s^-1 V^-1, which were among the highest reported for state-of-the-art perovskite-based X-ray detectors. This study presents a precise synthesis method to construct perovskite-based heterostructures. It also brings an in-depth understanding of the relationship between lattice structures and properties, which are beneficial for advancing high-performance and cost-effective X-ray detectors.