Engineered Excited‐State Coupling Enables Efficient Exciton Harvesting in Binuclear Copper Iodide Cluster Scintillators

ABSTRACT

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.