Triple-Cation and Mixed-Halide Perovskite Single Crystal for High-Performance X-ray Imaging

Low ionic migration is required for a semiconductor material to realize stable high-performance X-ray detection. In this work, successful controlled incorporation of not only methylammonium (MA⁺ ) and cesium (Cs⁺ ) cations, but also bromine (Br^- ) anions into the FAPbI₃ lattice to grow inch-sized stable perovskite single crystal (FAMACs SC) is reported. The smaller cations and anions, comparing to the original FA⁺ and I^- help release lattice stress so that the FAMACs SC shows lower ion migration, enhanced hardness, lower trap density, longer carrier lifetime and diffusion length, higher charge mobility and thermal stability, and better uniformity. Therefore, X-ray detectors made of the superior FAMACs SCs show the highest sensitivity of (3.5 ± 0.2) × 10⁶ μC Gy_air ^-1 cm^-2 , about 29 times higher than the latest record of 1.22 × 10⁵ μC Gy_air ^-1 cm^-2 for polycrystalline MAPbI₃ wafer under the same 40 keV X-ray radiation. Furthermore, the FAMACs SC X-ray detector shows a low detection limit of 42 nGy s^-1 , stable dark current, and photocurrent response. Finally, it is demonstrated that high contrast X-ray imaging is realized using the FAMACs SC detector. The effective triple-cation mixed halide strategy and the high crystalline quality make the present FAMACs SCs promising for next-generation X-ray imaging systems.