Efficient Rare‐Earth‐Based Hybrid Metal Halide Single‐Crystal Scintillators Enabled by Antimony‐Assisted Triplet Exciton‐Harvesting

ABSTRACT Rare Earth‐based hybrid metal halide scintillators have attracted considerable attention, owing to their lead‐free nature, strong x‐ray absorption, solution processability, and tunable optoelectronic properties. Nevertheless, their development has been hindered by insufficient exciton utilization, which leads to limited light yield. Herein, we report efficient single‐crystal scintillators with the composition RE(DMSO) 8 [Bi 1‐ x Sb x Cl 6 ], achieved through the antimony‐assisted triplet exciton‐harvesting strategy. In addition to direct x‐ray excitation of RE 3+ ions, the generated triplet excitons further sensitize RE 3+ emitters through energy transfer, establishing a dual‐channel excitation pathway that markedly enhances the overall radioluminescence (RL) of RE 3+ . By optimizing Sb concentration, we achieved a 2.06‐fold increase in RL intensity for Tb‐based systems and a 1.33‐fold enhancement for Eu‐based systems. The resulting scintillators exhibit a high light yield of 19022 photons/MeV, ultralow detection limits of 124 nGy/s, and robust radiation resistance. Centimeter‐scale single crystals grown for x‐ray imaging demonstrated a high spatial resolution of 15.7 lp/mm. Moreover, color‐tunable radioluminescence realized by adjusting the Tb/Eu ratio highlights their potential for color‐visualized radiation detection.