Low-Temperature Grown FAPb0.5Sn0.5I3 Single Crystals for Sensitive X-Ray Detectors with Low Dark Current and Detection Limit

Ion migration is a universal and pending issue that hinders performance and stability of metal halide perovskite (MHP) X-ray detectors. Lead-tin (Pb-Sn) perovskite single crystals hold potential for suppressing ion migration, but they face unideal Sn 2 ⁺ oxidation during crystal growth. Herein, a low-temperature crystal growth strategy using 2-methoxyethanol (2ME) as solvent is developed to mitigate oxidation of Sn 2 ⁺ and suppress formation of vacancy traps. The as-grown FAPb 0.5 Sn 0.5 I 3 (FA = CH(NH 2 ) 2 + ) single crystals exhibit a high ion migration activation energy ( E a ) of 0.95 eV, which is distinctly larger than those of lead-based perovskite crystals. As a result, the detectors exhibit a low dark current density of 0.75 nA cm −2 and small drift 4.2 × 10 −7 nA cm −1 s −1 V −1 as well as low detection limit of 0.81 nGy air s −1 , outperforming those of lead perovskite detectors. Besides, the FAPb 0.5 Sn 0.5 I 3 crystals possess high carrier mobility-lifetime ( µτ ) product of 2.7 × 10 −3 cm 2 V −1 , resulting in self-powered X-ray detectors with high sensitivity of 8.1 × 10 3 µC Gy air −1 cm −2 under 0 V bias. This work reports X-ray detectors based on Pb-Sn single crystals for the first time and shows their potential for inhibiting ion migration and dark current without sacrificing device sensitivity, which may promote stable and low-dose X-ray detection.