Giant Scintillation Yield Enhancement in Zero-Dimensional Halides by Exciton Confinement Manipulation

Low-dimensional halides (LDHs) with self-trapped exciton (STE) emission are promising materials for scintillation applications. Nonetheless, for almost all LDHs, the measured scintillation yield is still far below theoretical value due to severe exciton–exciton/exciton–defect interaction under ionizing radiation, despite high photoluminescence quantum yield (PLQY). Here, we reported a substantial enhancement of scintillation yield in zero-dimensional (0D) Cs₃YCl₆ by structural modulation. By copper(I) alloying in Cs₃YCl₆, the delocalized excitons in [YCl₆]³⁻ octahedra convert to strongly localized excitons within [Cu₂(YCl₆)₃]⁷⁻ clusters in (Cs₈Cu)Y₃Cl₁₈, as confirmed by first-principles calculations. Temperature-dependent photoluminescence spectroscopy and kinetic results reveal a higher energy barrier for STE quenching in (Cs₈Cu)Y₃Cl₁₈ than in Cs₃YCl₆. Benefiting from the enhanced exciton confinement effect, (Cs₈Cu)Y₃Cl₁₈ exhibits a 460% enhancement in the STE-related scintillation yield. This work opens up a new strategy to enhance scintillation yield in LDHs under ionizing radiation excitation.