Engineered Excited-State Coupling Enables Efficient Exciton Harvesting in Binuclear Copper Iodide Cluster...

Environmentally benign scintillators with broadband radioluminescence are highly desirable for low-cost, high-performance x-ray imaging. Recently, copper iodide (Cu-I) clusters have emerged as promising candidates, owing to strong spin-orbit coupling, favorable solution processability, excellent x-ray absorption efficiency, and efficient exciton harvesting enabled by aggregation-induced emission and thermally activated delayed fluorescence. However, the mechanism by which aggregation-state variation enhances the light yield by modulating intermolecular interactions remains poorly understood. Here, we establish a pair of isomeric Cu-I clusters with nearly identical x-ray attenuation coefficients as a model platform to isolate and elucidate the role of intermolecular coupling. In this context, we uncover a breakthrough mechanistic picture in which engineered excited-state coupling accelerates carrier relaxation and promotes efficient exciton harvesting and radiative recombination. Guided by this mechanism, water-resistant cluster scintillator glasses with excellent processing flexibility are fabricated, delivering a high light yield of 32,456 photons MeV^-1 and spatial resolution of 33.6 lp mm^-1. Furthermore, tandem integration with a high-Z scintillator enables selective density-discriminating x-ray imaging and micro-computed tomography. This work provides mechanistic guidance for ligand engineering in the design of efficient cluster scintillators and facilitates the high-throughput development of promising metal-cluster complexes for advanced optoelectronic applications.