Ion‐Pair Confinement Enables Through‐Space Charge Transfer for Negative Thermal Quenching Blue‐Emitting Scintillators in High‐Resolution X‐Ray Imaging

ABSTRACT Achieving high‐performance blue‐emitting scintillators with high stability and spatial resolution for x‐ray imaging remains challenge. Here, a sterically engineered ion‐pair confinement strategy in Cu(I) halide soft‐salt microcrystals was reported to achieve conjugation–disruption and high‐efficient through‐space charge transfer (TSCT) between Cu 2 I 3 − anionic clusters and ligands coordinated to Cu + centers. Strong electrostatic confinement and conformational locking suppress ligand π‐conjugation and metal–ligand orbital coupling, thereby localizing electronic delocalization, and stabilizing high‐energy blue emission. Substituent engineering (methyl or fluorine) modulates steric environments and supramolecular packing, enhancing lattice rigidity and suppressing dynamic disorder by inhibiting solvent inclusion during crystal growth and promoting radiative recombination. Notably, Cu 2 I 3 P(o‐tol) 3 (6‐Me‐dppy) exhibits negative thermal quenching (NTQ) behavior due to thermally activated population transfer within a confined excited‐state manifold. This synergistic integration of conjugation blocking, ionic confinement, and steric regulation effectively suppresses non‐radiative decay, yielding a light yield of 3.67 times that of BGO and excellent environmental and radiation stability. The resulting flexible microcrystal‐based scintillator films further enable high‐resolution (>20 lp mm −1 ) x‐ray imaging, while maintaining stable performance in underwater environments. Furthermore, the films support multi‐angle imaging acquisition and high‐fidelity three‐dimensional computed tomography reconstruction. This work establishes a general design paradigm for advanced blue‐emitting scintillators in next‐generation x‐ray imaging.