Thermally Activated Delayed Fluorescent Ag(I) Complexes for Highly Efficient Scintillation and High‐Resolution X‐Ray Imaging

Organic thermally activated delayed fluorescent (TADF) scintillators hold promising potential for applications in medical radiography and security detection, but the poor X‐ray absorption ability and inferior radioluminescence (RL) hampered their progression. Herein, the study has pioneered the development of high‐performance TADF Ag(I)‐based scintillators from M2X2(dppb)2 (M = Ag, Cu; X = Cl, Br, I) complexes with 1,2‐Bis(diphenylphosphino)benzene (dppb) ligand. In comparison with Cu(I) complexes, the Ag(I) series generally exhibited superior scintillation performance. Notably, Ag2Cl2(dppb)2 (Ag1) stands out with exceptionally high RL intensity (≈125% higher than that of CsI:Tl) and a low detection limit of 59.8 nGy s−1. The outstanding scintillation performance of Ag1 is primarily attributed to the synergistic effect of the high exciton utilization efficiency origin from a small singlet‐triplet energy gap, enhanced X‐ray absorption capacity by heavy atoms, and the high photoluminescence quantum yield (76.47% in ambient atmosphere). By fabricating a flexible film constructed with Ag1 submicron crystalline powders, a high spatial resolution of 25.0 lp mm−1 for X‐ray imaging is obtained. It offers new opportunities for utilizing TADF metal–organic complexes for highly efficient X‐ray scintillation and imaging. Scintillators with good radioluminescence performance are prepared by combining the TADF mechanism to optimize the utilization of triplet excitons, coupled with increased X‐ray absorption through heavy atoms, verifying the advantages of Ag(I)‐halide complexes on radioluminescence. Besides, the influence of halogens on photoluminescence and radioluminescence are investigated. As a practical application, Ag2Cl2(dppb)2 is applied to fabricate flexible scintillator films, achieving high‐resolution imaging of 25 lp mm−1.