Fluorinated Propyltriphenylphosphonium‐Engineered Moisture‐Stable Manganese Halide Scintillators for High‐Performance X‐Ray Imaging

ABSTRACT Zero‐dimensional (0D) manganese‐based organic–inorganic halides are promising lead‐free scintillators because of their high luminescence efficiency, large Stokes shifts, and structural tunability, but their practical use is hindered by poor moisture stability. Herein, we develop a fluorination strategy based on phosphonium‐cation engineering to simultaneously improve the scintillation performance and moisture stability of 0D manganese halides. By introducing fluorine atoms into the phenyl rings and alkyl chain of propyltriphenylphosphonium, three manganese‐based halide scintillators, (C 3 TPP) 2 MnBr 4 , (C 3 TPP‐F) 2 MnBr 4 , and (C 3 FTPP‐F) 2 MnBr 4 , were successfully designed and synthesized. All three compounds exhibit green emission under UV and X‐ray excitation. Among them, (C 3 FTPP‐F) 2 MnBr 4 shows the best overall performance, with a photoluminescence quantum yield of 79.4%, an estimated light yield of 49 000 photons MeV −1 , and a low detection limit of 109.2 nGy s −1 . More importantly, fluorination markedly enhances the moisture stability of the materials. After exposure to 100% relative humidity for 15 days, (C 3 FTPP‐F) 2 MnBr 4 retains about 50% of its initial radioluminescence intensity, whereas the non‐fluorinated analog undergoes rapid degradation and complete luminescence quenching within 3 days. Benefiting from a melting point lower than its decomposition temperature, (C 3 FTPP‐F) 2 MnBr 4 can be further processed into a transparent scintillator glass by melt‐quenching, enabling high‐resolution X‐ray imaging with a spatial resolution of 31.8 lp mm −1 .