(C₇H₁₁N₂)₂MBr₄ (M=Cu, Zn): X‐Ray Sensitive 0D Hybrid Metal Halides with Tunable Broadband Emission

Herein, a new family of hybrid metal halides, (DMAP) 2 MBr 4 (M = Cu, Zn), featuring zero‐dimensional (0D), pseudo‐layered crystal structures containing isolated molecular 4‐dimethylaminopyridinium (DMAP, C 7 H 11 N 2 + ) cations and MBr 4 2− tetrahedral anions are reported. (DMAP) 2 MBr 4 show remarkable long‐term stability, with no signs of degradation after one year of ambient air exposure. The reported solution synthesis affords large crystals measuring up to 1 cm, which showed significant response to soft 8 keV X‐ray photons when implemented into X‐ray detectors. Furthermore, (DMAP) 2 ZnBr 4 demonstrates tunable color light emission properties, which is attributed to the organic molecular units based on our combined experimental and computational results. The measured photoluminescence quantum yield (PLQY) for (DMAP) 2 ZnBr 4 is 7.35 %, a remarkable enhancement of emission efficiency as compared to a weak emission from the organic precursor. The inexpensive and earth‐abundant chemical compositions and ease of preparation of the new hybrid metal halides make them promising candidates for optical and electronic applications.