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.
Perovskite polycrystalline thick films are promising for x-ray detection and imaging, yet the simultaneous realization of high sensitivity and a low detection limit remain difficult due to the trade-off between transport and ion migration. Herein, we report the preparation of FAPb 0.5 Sn 0.5 I 3 (FA = CH(NH 2 ) 2 ) perovskite polycrystalline thick films with negligible Sn 2+ oxidation at room temperature by solvent engineering. The as-prepared films deliver exceptional carrier transport properties, as evidenced by an ultralong carrier diffusion length ( L D ) of 58 µm. Moreover, the high ion migration activation energy ( E a ) of 0.67 eV endows the detectors with suppressed dark current and a minimal drift of 2.09 × 10 −5 nA cm −1 s −1 V −1 . Collectively, these merits result in self-powered x-ray detectors with both high sensitivity of 3.88 × 10 3 µC Gy air −1 cm −2 and an ultralow detection limit of 0.93 nGy air s −1 . Our work may promote the development of stable and low-dose-rate perovskite x-ray imaging.
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