Organic Phosphonium Side‐Chain Engineering in Metal Halide Glassy Scintillators for Enhanced X‐Ray Dynamic Imaging

X-ray imaging utilizing organic-inorganic hybrid metal halide (OIHMH) glassy scintillators has garnered significant attention. But their inferior radioluminescence makes achieving rapid image acquisition difficult, posing a persistent challenge for dynamic imaging. Herein, organic phosphonium halide side-chain engineering is proposed, introducing bulky aromatic rings at the alkyl chain ends, to improve the radioluminescence of OIHMHs. For Mn(II)-based OIHMHs, the (BUP)₂MnCl₄ (BUP = butyltriphenylphosphonium) powder has a low relative light yield (5400 photons MeV^-1). After introducing a benzyl group, this value of (BnO-MTP)₂MnCl₄ (BnO-MTP = (benzyloxy)methyl) triphenylphonium) powder boosts to 60 000 photons MeV^-1. The introduction of benzyl group can restrict molecular non-radiative vibrations, increase exciton binding energy, enhance electron-phonon coupling, and reduce self-absorption, thus significantly improving exciton utilization and scintillation performance of (BnO-MTP)₂MnCl₄. Besides, the transparent (BnO-MTP)₂MnCl₄ glass has a low melting point (167 °C) and high relative light yield (26 000 photons MeV^-1). When applied to X-ray imaging, it can achieve static imaging with a spatial-resolution of up to 24.6 lp mm^-1 and clear dynamic imaging under X-ray irradiation. Furthermore, this strategy also applies to Sb(III)-based OIHMHs with self-trapped exciton emissions, where (BnO-MTP)₂SbCl₅ exhibits superior scintillation performance compared to (BUP)₂SbCl₅, demonstrating its broad applicability in constructing high-performance OIHMH glassy scintillators.