Cesium‐Based Molecular Perovskites With Superior Stability for High‐Performance X‐Ray Detection

Metal-free molecular perovskites have shown great potential for X-ray detection due to their tunable chemical structures, low toxicity, and excellent photophysical properties. However, their limited X-ray absorption and environmental instability restrict their practical application. In this study, cesium-based molecular perovskites (MDABCO-CsX₃, X = Cl, Br, I) are developed by introducing Cs⁺ at the B-site to enhance X-ray absorption while retaining low toxicity. The effects of halide modulation on the physical properties and device performance are systematically investigated. Among the variants, MDABCO-CsBr₃ exhibited superior environmental stability, attributed to the optimal ionic radius and high chemical stability of Br^-. This stability is further enhanced by a higher tolerance factor, which promotes a stable 3D cubic structure and suppresses ion migration within the crystal. Consequently, MDABCO-CsBr₃-based X-ray detectors demonstrated reduced ionic migration, minimal dark current drift, and a stable current response under X-ray exposure, achieving a high sensitivity of 4124 µC Gy^-1 cm^-2 and a low detection limit of 0.45 µGy s^-1. Moreover, the devices exhibit excellent thermal stability, operating effectively at temperatures up to 130 °C. These results highlight MDABCO-CsBr₃ as a promising candidate for stable and efficient X-ray detection, expanding the applicability of molecular perovskites in advanced radiation detection technologies.