Lead-Free Bismuth-Based Perovskite X-ray Detector with High Sensitivity and Low Detection Limit

Bismuth-based halide perovskites have shown great potential for direct X-ray detection, attributable to their nontoxicity and advantages in detection sensitivity and spatial resolution. However, the practical application of such materials still faces the critical challenge of combining both high sensitivity and low detection limits. Here, we report a new type of zero-dimensional (0D) perovskite (HIS)BiI₅ (1, where HIS²⁺ = histamine) with high sensitivity and a low detection limit. Structurally, the strong N-H···I hydrogen bonds between HIS²⁺ cations and inorganic frameworks enhance the rigidity of the structure and diminish the intermolecular distance between adjacent inorganic [Bi₂I₁₀]^4- dimers. By virtue of such structural merits, single crystal 1 exhibits excellent physical properties perpendicular to both the (001) and (010) faces. Perpendicular to the (010) face, 1 exhibited a high electrical resistivity (2.31 × 10¹¹ Ω cm) and a large carrier mobility-lifetime product (μτ) (2.81 × 10^-4 cm² V^-1) under X-ray illumination. Benefiting from these superior physical properties, it demonstrates an excellent X-ray detection capability with a sensitivity of approximately 10³ μC Gy_air^-1 cm^-2 and a detection limit of 36 nGy_air s^-1 in both directions perpendicular to the (001) and (010) crystal faces. These results provide a promising candidate material for the development of new, lead-free, high-performance X-ray detectors.