Unlocking The Inherent Luminescence of Eu2+/Eu3+ by Light‐Induced Oxidation for Invisible Optical Storage

Abstract Color‐tunable luminescent materials are increasingly recognized for their potential applications in high‐security anticounterfeiting and optical storage technologies. However, luminescent materials with high‐contrast photoswitching behavior that change their luminescence properties in response to external stimuli are extremely scarce. In this study, a time‐dependent color‐tunable luminescent material, Na 2 BaSiO 4 :Eu 2+ (NBSO:Eu), is introduced. This material leverages the inherent luminescence of Eu 2+ /Eu 3+ through a light stimulus. Under 365 nm irradiation, the blue luminescence of Eu 2+ gradually degraded over time, reaching a luminescence contrast of up to 88%. This degradation is accompanied by a color change of the emitted light from blue to red (Eu 3+ ). These color changes can be reversibly tuned by alternating light or thermal stimuli. Experimental investigations revealed that the photogenerated Eu 3+ ions and defects, acting as killer centers, induced multicolor luminescent switching behavior. Owing to their unique optical properties, NBSO:Eu offers exciting opportunities for designing advanced dynamic anticounterfeiting and invisible optical storage.