Hydrogen‐Bond‐Anchored Metal‐Free Cationic TADF Glassy Scintillators for High‐Resolution Dynamic X‐Ray Imaging

ABSTRACT Organic glassy scintillators offer a promising platform for scalable X‐ray imaging owing to their optical transparency and melt processability. However, their performance is often limited by inefficient triplet‐exciton utilization and poor condensed‐phase stability. Although flexible side chains or rotatable units facilitate glass formation, they also increase molecular relaxation and nonradiative energy dissipation. Herein, we develop three single‐component metal‐free ionic thermally activated delayed fluorescence (TADF) scintillators (C2‐HI, C2‐OHI, and C2‐OMeI) using a hydrogen‐bond‐assisted side‐chain anchoring strategy. Compared with the non‐hydrogen‐bonded analogues C2‐HI and C2‐OMeI, hydroxyl‐functionalized C2‐OHI forms directional O─H···I − interactions that rigidify the local molecular environment, suppress nonradiative relaxation, and stabilize the condensed phase without disturbing the emissive framework. Consequently, C2‐OHI achieves a photoluminescence quantum yield of 93.69%, a radioluminescence intensity of 522% relative to commercial BGO, and an estimated relative light yield of 6.24 × 10 4 photons MeV −1 . Its melt‐quenched glass retains efficient TADF scintillation with an estimated relative light yield of 2.00 × 10 4 photons MeV −1 , enabling X‐ray imaging at 22.7 lp mm −1 and real‐time imaging at 60 fps. This work establishes hydrogen‐bond‐assisted side‐chain anchoring as a molecular design strategy for simultaneously regulating excited‐state dynamics and condensed‐phase stability in metal‐free organic glass scintillators.