Scintillation Performance of Mn(II)-Doped Cs₂NaBiCl₆ Double Perovskite Nanocrystals for X-Ray Imaging Applications

Lead-free halide perovskite-based X-ray scintillators with high light yield (LY) and low detection limit (LOD) have become a growing subject of research interest due to their promising application in a wide range of areas, from security to healthcare. Herein, a modified hot injection method is employed to synthesize Mn(II)-doped Cs2NaBiCl6 double perovskite nanocrystals (DPNCs) and to examine their scintillating properties for application in X-ray imaging and detection. The Mn(II)-doped Cs2NaBiCl6 DPNCs exhibit a broad orange photoluminescence (PL) band at 586 nm with a PL quantum yield of 10.6%, attributed to the T-4(2g)(4G) -> (6)A(1g)(6S) transition of Mn2+. Temperature-dependent PL and time-resolved PL spectra of 4.04% Mn(II)-doped Cs2NaBiCl6 demonstrate that the orange emission intensity initially reaches a maximum and subsequently decreases, while the decay lifetimes monotonically decrease with increasing temperature. This inconsistency can be due to the effect of the [MnCl6](4-) octahedra and electron-phonon coupling at elevated temperatures. Further, 0.05 mm thick Cs2NaBiCl6:4.04%Mn@poly(methyl methacrylate) scintillator film is synthesized with an LY of 28,350 photons MeV-1 and a LOD of 45.2 nGy(air) s(-1). Additionally, this film demonstrates good X-ray imaging performance with a spatial resolution of 14.76 line pairs (lp) mm(-1) and shows exceptional stability under prolonged X-ray exposure.