Luminescence Improvement of Hybrid Zinc‐Based Halides via Sb³⁺‐Doping for Flexible X‐Ray Imaging

Recently, zinc‐based metal halides have attracted numerous attention due to their excellent stability, low toxicity, and wide bandgaps. However, [ZnX 4 ] 2− tetrahedra in zinc‐based halides are found to be non‐optically active, which leads to poor photoluminescence quantum yields (PLQYs). Herein, Sb 3+ ions are doped into hybrid zinc‐based halides of (C 8 H 26 N 4 )ZnCl 6 single crystals (SCs) via an evaporative crystallization method. Compared with undoped (C 8 H 26 N 4 )ZnCl 6 SCs with weak blue emission, Sb 3+ ‐doped (C 8 H 26 N 4 )ZnCl 6 SCs exhibit a strong broadband emission centered at 694 nm with a high PLQY of 67%, which is confirmed to be derived from self‐trapped excitons (STEs) of Sb 3+ luminescent centers. Subsequently, Sb 3+ ‐doped (C 8 H 26 N 4 )ZnCl 6 is employed in flexible scintillation films, which demonstrates remarkable X‐ray imaging of complex objects with a spatial resolution of 3.6 lp mm −1 and a detection limit of 123.8 µGy air s −1 , proving its promising potential in flexible X‐ray imaging applications.