Low Dimensional, Metal-Free, Hydrazinium Halide Perovskite-Related Single Crystals and Their Use as X-Ray Detectors

Metal-free halide perovskites (MFHaPs) have garnered significant attention in recent years due to their desirable properties, such as low toxicity, light weight, chemical versatility, and potential for optoelectronics. MFHaPs with the formula A²⁺ B⁺ X^-3 (where A is a large organic divalent cation, B⁺ is typically NH₄ ⁺ , and X is a halide) have been studied extensively, but few studies have examined alternative cations at the B position. This paper reports the synthesis of three MFHaP-related single crystals, DABCO-N₂ H₅ -X₃ (DABCO = N-N-diazabicyclo[2.2.2]octonium, X = Br and I) and (DABCO)₃ -N₂ H₅ (NH₄ )₂ Cl₉ , which feature hydrazinium (N₂ H₅ ) at the B position. The crystals have a perovskite-like, one-dimensional, edge-connected structure and exhibit optical and band structure properties. The crystals were then tested as X-ray detectors, where they showed excellent photoresponsivity, stability, and low background noise, owing to the large semi-gap that dictates long lifetimes. The detectors exhibited sensitivity as high as 1143 ± 10 µC Gy_air ^-1 cm^-2 and a low detection limit of 2.68 µGy s^-1 at 10 V. The researchers suggest that the stronger hydrogen bonding in N₂ H₅ ⁺ compounds compared to NH₄ ⁺ MFHaPs may contribute to the detectors' enhanced stability.