Highly Stable Lead‐Free Perovskite Single Crystals With Abundant Intermolecular Interactions for Efficient X‐Ray Detection

ABSTRACT Low‐dimensional bismuth‐based perovskites (LBHPs) are considered promising alternatives to lead‐based perovskites owing to the similar electronic structure of bismuth and lead. However, due to the large spacing and weak electronic coupling between adjacent octahedra, the charge transport in LBHPs is impeded. Herein, using 0D perovskite (BZA) 3 BiI 6 ( 1 , BZA = benzylamine) as the parent compound, a novel 1D perovskite (2‐FBA) 2 BiI 5 ( 2 , 2‐FBA = 2‐fluorobenzylamine) with abundant intermolecular interactions is reported through halogen modification of the cation, successfully achieving ultra‐high sensitivity and stable X‐ray detection. Specifically, the introduction of F results in abundant interactions including π – π (3.479 Å and 3.729 Å) and F···I (3.545 Å), which effectively suppress ion migration and shorten the distance between adjacent octahedra from 4.206 Å ( 1 ) to 4.010 Å ( 2 ). The X‐ray detector based on 2 exhibits a high sensitivity of 6392.1 µC Gy −1 cm −2 and a low detection limit of 62.1 nGy s −1 . Impressively, even after 45 days of storage in air, the device still maintained approximately 96% of the initial sensitivity value (6107.3 µC Gy −1 cm −2 ). This work develops a novel “green” material through a halogen modification strategy, offering a safe and stable alternative for X‐ray detection.