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

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- _xSb_xCl₆], achieved through the antimony-assisted triplet exciton-harvesting strategy. In addition to direct x-ray excitation of RE³⁺ ions, the generated triplet excitons further sensitize RE³⁺ emitters through energy transfer, establishing a dual-channel excitation pathway that markedly enhances the overall radioluminescence (RL) of RE³⁺. 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.