Near-unity quantum yield in zero-dimensional lead-free manganese-based halides for flexible X-ray imaging with high spatial resolution

Low-dimensional luminescent lead-free metal halides have received substantial attention due to their unique optoelectronic properties. Among them, zero-dimensional (0D) manganese (II)-based metal halides with negligible self-absorption have emerged as potential candidates in X-ray scintillators. Herein, we for the first time report a novel lead-free (TBA)2MnBr4 single crystal synthesized via a facile solvent evaporation method. In this crystal, [MnBr4]2− units are isolated by large TBA+ organic cations, resulting in a unique 0D structure. The prepared manganese-based crystals exhibit a bright-green emission centered at 512 ​nm with a high photoluminescence quantum yield (PLQY) of 93.76% at room temperature, originating from the 4T1–6A1 transition of Mn2+. Apart from their outstanding optical performance, the crystals also show excellent stability and can maintain 94.4% of the initial PLQY even after being stored in air for 90 days. Flexible (TBA)2MnBr4 films prepared as X-ray imaging scintillators exhibit a low detection limit of 63.3 nGyair/s, a high light yield of 68000 ​ph/MeV, and a high spatial resolution of 15.4 ​lp/mm. Thus, this work not only enriches the family of lead-free metal halides but also expands the application of manganese (II)-based halides in flexible X-ray scintillators.