Excitation-Dependent Emission in Sb3+-Doped All-Inorganic Rare-Earth Double Perovskites for Anticounterfeiting Applications

Achieving high-efficiency tunable emission in a single phosphor remains a significant challenge. Herein, we report a series of Sb³⁺-doped all-inorganic double perovskites, Sb³⁺:Cs₂NaScCl₆, with efficient excitation-dependent emission. In 0.5%Sb³⁺:Cs₂NaScCl₆, strong blue emission with a high photoluminescence quantum yield (PLQY) of 85% is obtained under 265 nm light irradiation, which turns into bright neutral white light with a PLQY of 56% when excited at 303 nm. Spectroscopic and computational investigations were performed to reveal the mechanism of this excitation-dependent emission. Sb³⁺ doping induces two different excitation channels: the internal transition of Sb³⁺: 5s² → 5s5p and the electron transfer transition of Sb³⁺: 5s → Sc³⁺ 3d. The former one generates excited Sb³⁺ ions, which can undergo efficient energy transfer to populate the host self-trapped exciton (STE) state, yielding enhanced blue emission. The latter one leads to the formation of a new STE state with the hole localized on Sb³⁺ and the electron delocalized on the nearest Sc³⁺, which accounts for the newly exhibited low-energy emission. The difference in the excitation pathways of the two emitting STE states results in the highly efficient excitation-dependent emission, making the doped systems promising anticounterfeiting materials.