Centimeter‐Sized Molecular Perovskite Crystal for Efficient X‐Ray Detection

Molecular perovskites have demonstrated great potential for ferroelectrics and nonlinear optics; however, their charge transport properties for optoelectronics have rarely been explored. Here, understanding of charge transport behavior of molecular perovskite under X‐ray excitation based on centimeter‐scale TMCM‐CdCl3 (TMCM+, trimethylchloromethyl ammonium) single crystal is demonstrated. The crystal is fabricated from an aqueous solution and exhibits a large bandgap of 5.51 eV, with the valence band maximum mainly dominated by the Cl‐p/Cd‐d states and the conduction band minimum primarily by Cd‐s/Cl‐p states. Charge mobility exceeding 40 cm2 V−1 s−1 and mobility–lifetime (µτ) product on the order of 10−4 cm2 V−1 for the crystal are observed. These excellent optoelectronic properties translate to an efficient photoresponse under X‐ray excitation, with the sensitivity reaching 128.9 ± 4.64 µC Gyair−1 cm−2 [fivefold higher than that of the commercialized amorphous selenium (α‐Se)] and a low detection limit of 1.06 μC Gyair−1 s−1 (10 V bias). This work pioneers a superior metal‐based molecular perovskite single‐crystal based paradigm for optoelectronic investigation, which may lead to the discovery of a new generation of X‐ray detection and imaging materials.