Melt-Processing Enabled Flexible Metal Halide-Nylon Luminescent Films with Enhanced Optical Transmission for Curved X-Ray Imaging

Abstract

Organic–inorganic hybrid metal halides are emerging as a class of functional materials that combine attractive photophysical properties with great processability. Their modular chemical structures allow for melt processing through crystal-melt transitions. Herein, the study reports the synthesis of (Bzmim)₂MnX₄ (Bzmim = 1-benzyl-3-methylimidazolium, X = Cl, Br, I) single crystals with low melting temperatures ranging from 130 to 160 °C. Among them, (Bzmim)₂MnBr₄ exhibits superior luminescence performance with a photoluminescence quantum yield of 78.6% and a light yield of 34 900 photons MeV⁻¹, making it act as a promising scintillator. Interestingly, leveraging the melt fluidity and the porous structure of nylon film, a transparent crystalline (Bzmim)₂MnBr₄-Nylon composite film is fabricated by the melt-infiltration process. Compared to the nylon film, the composite film has an increased light transmittance from ≈20% to >60%. It can be attributed to uniform melt crystallization in the pores of nylon film, which suppresses severe light crosstalk caused by the large refractive index difference at the nylon-air interface. The melt-processable transparent composite film exhibits a spatial resolution of 16 line pairs per millimeter in practical X-ray imaging, as well as promising applications in curved X-ray imaging due to its great flexibility.