Molecular Design of Layered Hybrid Silver Bismuth Bromine Single Crystal for Ultra‐Stable X‐Ray Detection With Record Sensitivity

Abstract Nowadays, weak interlayer coupling and unclear mechanism in layered hybrid silver bismuth bromine (LH‐AgBiBr) are the main reasons for limiting its further enhanced X‐ray detection sensitivity and stability. Herein, the design rules for LH‐AgBiBr and its influence on X‐ray detection performance are reported for the first time. Although shortening amine size can enhance interlayer coupling, its detection performance is severely hampered by its easier defect formation caused by enlarged micro strain. In contrast, an appropriate divalent amine design endows the material with improved interlayer coupling and released micro strain, which benefits crystal stability and mechanical hardness. Another contribution is to increase material density and dielectric constant; thus, enhancing X‐ray absorption and carrier transport. Consequently, the optimized parallel device based on BDA₂AgBiBr₈ achieves a record sensitivity of 2638 µC Gy_air⁻¹ cm⁻² and an ultra‐low detection limit of 7.4 nGy_air s⁻¹, outperforming other reported LH‐AgBiBr X‐ray detectors. Moreover, the unencapsulated device displays remarkable anti‐moisture, anti‐thermal (>150 °C), and anti‐radiation (>1000 Gy_air) endurance. Eventually, high‐resolution hard X‐ray imaging is demonstrated by linear detector arrays under a benign dose rate (1.63 µGy_air s⁻¹) and low external bias (5 V). Hence, these findings provide guidelines for future materials design and device optimization.