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 Gyair−1 cm−2, about 29 times higher than the latest record of 1.22 × 105 μC Gyair−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. Smaller cations and anions are incorporated into FAPbI3 single crystal to release its lattice stress and enhance its stability. The formed inch‐sized triple‐cation mixed‐halide perovskite single crystals exhibit suppressed ion migration, long carrier diffusion length, large mobility, and excellent uniformity. These superior properties are utilized for the construction of a high‐performance X‐ray detector array, realizing high‐contrast X‐ray imaging.