Multiple Interactions in Polar Lead-Free Perovskites toward Highly Stable X-Ray Detection

Lead-free halide perovskites have emerged as a promising class of high-performance "green" X-ray detecting semiconductors due to their nontoxicity and strong X-ray absorption. However, ion migration caused by high operating electric field remains a bottleneck limiting the long-term stability of perovskite X-ray detectors. Herein, by introducing multiple halogen interactions in lead-free perovskites, stable X-ray detection is successfully realized. Specifically, 0D polar bismuth halide perovskites (R/S-BPEA)₄Bi₂I₁₀ (1R/1S, R/S-BPEA = R/S-1-(4-bromophenyl)ethylammonium) are designed by introducing Br-substituted chiral organic cation BPEA, which exists with the molecular electrostatic forces between the Br atom and neighboring benzene ring and halogen interaction of Br···I. Notably, their introduction improves the activation energy of ion migration, which makes the dark current drift of the X-ray detector as low as 3.25 × 10^-8 nA cm^-1 s^-1 V^-1 at 2500 V cm^-1. Furthermore, the excellent operational stability under prolonged X-ray irradiation and unchanged device sensitivity after 90 days of exposure to air, further demonstrates the improved stability of perovskites. Meanwhile, the chiral-polar characteristic of the 1R/1S gives them potential for self-powered detection, with a low detection limit of 183 nGy s^-1 at zero bias for single-crystal devices. This study opens new avenues for the future development of "green", highly stable, self-powered radiation detectors.