Compositional engineering of doped zero-dimensional zinc halide blue emitters for efficient X-ray scintillation

Abstract

Recently, doped ternary zinc halides with high photoluminescence quantum yields (PLQYs) have demonstrated great potential in light emitting applications. However, the composition-dependent photophysical properties of ternary zinc halides have not been investigated, and their X-ray scintillation performances remain unexplored. Here, a compositional engineering strategy for highly efficient Cu⁺-doped zero-dimensional A₂ZnX₄ (A = Rb, Cs; X = Cl, Br) blue emitters is presented. It is found that the A-site cations show a negligible influence on the emission spectra of both pure A₂ZnX₄ and Cu⁺-doped A₂ZnX₄, while the change of the halide anion slightly shifts the emission peak of doped A₂ZnX₄. The detailed photoluminescence (PL) studies indicate that the emission of Cu⁺-doped A₂ZnX₄ may come from two self-trapped exciton (STE) emission centers, namely Zn-related and Cu-related STEs. An energy transfer process from the Zn-related STE to the Cu-related STE is proposed. Based on the composition dependent photophysical and scintillation property study, Cu⁺-doped Cs₂ZnBr₄ is found to show the best scintillation performance among these zinc halides. Cu⁺-doped Cs₂ZnBr₄ shows a relatively high light yield of ∼10 000 photons MeV⁻¹, a low detection limit of 57 nGy_air s⁻¹, and good radiation stability. The X-ray imaging results based on a doped Cs₂ZnBr₄ scintillation screen show a high spatial resolution of up to 9 line pairs per millimeter. These results demonstrate that the doped Cs₂ZnBr₄ scintillator could be a potential candidate for sensitive X-ray detection and imaging.