Ion-exchange-induced slow crystallization of 2D-3D perovskite thick junctions for X-ray detection and imaging

Metal-halide perovskites have recently emerged as promising candidates for next-generation X-ray detectors, mainly benefiting from their low-temperature solution processability, chemical versatility, low cost, and excellent and tunable optoelectronic properties. However, the fabrication of perovskite thick junctions is very challenging, particularly for solution-processed thick photodiodes. Here, we report an ion-exchange strategy to prepare two-dimensional (2D)-3D perovskite thick films for directly detecting X-rays. This approach provides a facile and generic fabrication of high-quality perovskite films with various perovskite precursors, achieving uniform morphology, tunable thickness, and vertically monolithic crystal phase. The dynamic processes of the ion exchange were fully characterized and studied with multiple in situ and ex situ techniques, e.g., photoluminescence spectroscopy and X-ray diffraction. After optimization, record-high X-ray sensitivity of 1.36 × 104 μC Gyair-1 cm-2 and ultra-low detection limit of 4.2 nGyair s-1 were achieved based on the optimized (BA2PbBr4)0.5FAPbI3 detectors, demonstrated along with 32 × 32 pixel prototypical photodetector arrays.