Anti‐Counterfeiting and Encryption Application of Rare Earth Luminescent Material NaLa(MoO ₄ ) ₂ :Er ³⁺ ,Yb ³⁺ Phosphor

Abstract Optical anti‐counterfeiting has become a research hotspot in recent years because of its excellent convenience and concealment. A novel Er 3+ /Yb 3+ Co‐doped Nala (MoO 4 ) 2 phosphor was synthesized, which has double excitation response luminescence characteristics. The material shows intense emission under both 365 nm ultraviolet and 980 nm near‐infrared excitation, with distinct spectral modulation observed between the two excitation modes. Under 365 nm excitation, the phosphor displays stable green down‐shifting at 529/550 nm (CIE 0.31, 0.53), whereas 980 nm near‐infrared excitation enables color‐tunable up‐conversion from green to orange‐yellow as the Yb 3 ⁺ content is varied from 0.01 to 0.07 mol%, with a 2.3‐fold intensity enhancement at the optimal 0.05 mol% Yb 3 ⁺. Under 365 nm UV activation produces characteristic 4 I 13/2 → 4 I 15/2 transitions are observed. Using this phosphor–PAA ink, we fabricated time‐resolved anti‐counterfeiting labels that decrypt under NIR irradiation after a 50 ms delay, effectively suppressing ambient‐light interference and enabling multilevel security through orthogonally excitation‐responsive persistent luminescence. This work offers a new strategy for high‐security optical encryption.