Dimensional Engineering in 4AMPBiX ₅ Metal Halides: From 0D to 1D for Enhanced X‐Ray Detection Performance

ABSTRACT Bi‐based metal halides (MHs) have emerged as promising candidates for X‐ray detection, attribute to its strong X‐ray absorption and superior environmental stability. Unfortunately, their practical applications are often impeded by inefficient charge transport and ion migration. To address these limitations, we employed organic cation 4‐(aminomethyl)pyridine (4AMP 2+ ) as the A‐site cation and adopted halogen‐site modulation strategy to tune the Bi─X bond distances within lattice structure to prepared 4AMPBiX 5 (X = Cl, Br, I) MHs. This design allows for the precise regulation of structural dimensions from 0D to 1D, thereby effectively optimizing charge transport and suppressing ion migration. Specifically, the smaller Cl − (1.81 Å) tends to form isolated [BiCl 6 ] 3− octahedra, resulting in a 0D structure. In contrast, the larger Br − (1.96 Å) and I − (2.20 Å) ions promote the formation of 1D structures via edge‐ or corner‐sharing connectivity. The synergistic effects of structural dimensionality and halide composition on the crystal structure, electrical properties, and stability of the materials. Benefiting from above aspects, the novel 1D 4AMPBiBr 5 SC detector achieved excellent performance with a high sensitivity of 7,812 µC Gy air −1 cm −2 , a low limit of detection (LoD) of 1.58 nGy air s −1 , and a negligible dark current drift of 1.788 × 10 −8 nA cm −1 V −1 s −1 . This work highlights the potential of dimensional engineering for advancing X‐ray detection technologies.