Highly Luminescent Phase-Stable Hybrid Manganese Halides for Efficient X-ray Imaging

Mn(II)-based organic-inorganic hybrid metal halides have garnered considerable attention for their potential use in X-ray imaging due to their cost-effective solution processability and remarkable radioluminescence efficiency. However, achieving a photoluminescence quantum yield (PLQY) close to 100% across all compositions containing Cl^-, Br^-, and I^- has been a challenge. Here, we introduce an efficient spacer cation, BDPA⁺ (C₁₅H₁₈N⁺), which enables all halide compounds to achieve high PLQYs of 95-98%. The high fluorescence efficiency is attributed to the passivation effect provided by π-conjugated aromatic groups and the long distance between emissive centers afforded by the periodic bulk structures of BDPA⁺. This effectively reduces energy transfer between Mn²⁺ ions, resulting in enhanced luminescence. Additionally, the strong hydrophobic nature of the organic component ensures that the resulting crystals maintain their stability for over 2 months in ambient air, making them suitable for a wide range of applications. A representative scintillator prepared from (BDPA)₂MnBr₄ exhibits impressive X-ray imaging performance with a high light yield of 44,000 ph/MeV and a low detection limit of 0.32 μGy/s, comparable to those of commercial LuAG:Ce scintillator crystals (25,000 ph/MeV, 2.32 μGy/s). These findings hold great promise for the future development of this class of materials, particularly for stable high-energy radiation detection.