Triplet Excitons Harvesting in Host–Guest Doped Organic Glassy Scintillators for High‐Resolution X‐Ray Imaging

Abstract Organic fluorescent glassy scintillators hold great promise for security screening and medical imaging due to their excellent optical transparency and good processability. However, their limited exciton utilization, particularly the inefficient harvesting of 75% triplet excitons, restricts radioluminescence (RL) efficiency and imaging resolution. Herein, a general host–guest doping strategy is proposed to enhance triplet exciton harvesting and scintillation performance in organic fluorescent glass. Specifically, using 1,3‐Bis(9H‐carbazol‐9‐yl)benzene (mCP) as a glass‐forming host and doping it with three types of high triplet‐utilization emitters (HMB, IrPA, and HXF), the obtained HMB@mCPG, IrPA@mCPG, and HXF@mCPG glasses exhibit thermally activated delayed fluorescence, phosphorescence and delayed fluorescence from inverted singlet‐triplet gap, respectively. Compared to pristine mCP glass, these doped glasses exhibit RL intensity enhancements of 3.4‐fold (HMB@mCPG), 6.2‐fold (IrPA@mCPG), and 3.4‐fold (HXF@mCPG), respectively. The improvements are attributed to efficient host–guest energy transfer, which enables effective harvesting of triplet excitons and suppression of aggregation‐induced quenching in glassy materials. Furthermore, all samples enable X‐ray imaging with spatial resolutions exceeding 20 lp mm −1 , with HXF@mCPG even achieving over 30 lp mm −1 . This work highlights a versatile and effective triplet‐harvesting strategy for advancing the performance of organic glassy scintillators, paving the way toward high‐resolution X‐ray imaging applications.