Intermolecular Aggregation-Induced Delayed Fluorescence Scintillators for Ultrahigh-Resolution X-Ray Imaging

Organic X-ray scintillators (OXSTs) with excellent optoelectronic properties and facile processability are highly attractive for next-generation radiation detection and medical imaging. However, achieving efficient solid-state emission with high exciton utilization efficiency remains a formidable challenge because aggregation-caused quenching fundamentally suppresses radiative processes. Here, we introduce an intermolecular aggregation-induced delayed fluorescence (AIDF) strategy that combines aggregation-induced emission and thermally activated DF features. The tailored emitter exhibits efficient AIDF with sub-microsecond delayed lifetimes via through-space charge transfer, enabling effective harvesting of singlet and triplet excitons. When blended into a polysulfone host, the composite films deliver bright and stable radioluminescence across a wide concentration range, showing exceptional resistance to concentration quenching under X-ray excitation. Benefiting from large Stokes shifts, rapid reverse intersystem crossing, and efficient radiative emission, the resulting scintillator achieves an ultralow detection limit of 0.255 µGy s^-1 and a high spatial resolution of 20.0 lp mm^-1, outperforming most organic counterparts and even some inorganic ones. The flexible, uniform, and transparent scintillation screens also exhibit excellent photostability for high-quality X-ray imaging. This work establishes a practical molecular design paradigm to circumvent aggregation-caused quenching and highlights the unique advantages of intermolecular AIDF in enabling efficient exciton utilization, paving the way for high-resolution thin-film scintillators.