A Lead‐Free Transparent Hybrid Manganese(II) Metal Halide Flexible Scintillator for Large‐Area and High‐Resolution X‐Ray Imaging

Abstract Hybrid manganese metal halides have emerged as promising candidates for next‐generation X‐ray scintillators due to their intense radioluminescence and environmental friendliness. However, challenges in cation engineering and scalable fabrication hinder the development of high‐resolution, large‐area, and flexible scintillator screens. Herein, a novel zero‐dimensional organic‐inorganic manganese (II) halide, denoted as (C 25 H 30 P) 2 MnBr 4 , is designed featuring sterically bulky triphenylphosphonium cations that synergistically enhance the photoluminescence quantum yield (PLQY = 99.2%) and radioluminescence efficiency. The (C 25 H 30 P) 2 MnBr 4 single crystal exhibits outstanding scintillation properties, exhibiting a record‐high light yield of 85 000 photons MeV −1 , an excellent linear response to X‐ray dose rate (5.52 µGy air s −1 to 1.13 mGy air s −1 ), and an ultra‐low detection limit of 25 nGy air s −1 . Furthermore, a flexible free‐standing (C 25 H 30 P) 2 MnBr 4 ‐thermoplastic polyurethane (TPU) composite film is demonstrated, fabricated via a room‐temperature in situ strategy. This film achieves an ultra‐large active area (>9000 mm 2 ), uniform transparency, and exceptional mechanical flexibility. The (C 25 H 30 P) 2 MnBr 4 ‐TPU yielded a high spatial resolution of 13.4 lp mm −1 while achieving high‐quality imaging of complex 3D objects under low‐dose X‐ray irradiation. This work establishes a generalizable framework for designing large‐area and high‐resolution scintillators through cation engineering and polymer matrix integration, opening new avenues for next‐generation flexible X‐ray imaging technologies.