Matrix‐Emission‐Assisted Photochromism Enables Dual‐Field Color‐Changing Modulations

Abstract Trap‐related inorganic photochromic materials coupled with regulated luminescence have attracted extensive interest due to their great potential in optoelectronic devices, optical memory, and multiple anti‐counterfeiting applications. Combining photochromism with luminescence modulations enables the light‐driven reversible manipulation of optical information in both dark and bright fields. However, photochromism induced luminescence modulation is still restricted to monochromatic visualization with only emission intensity variations. To this end, the limitation of the common single‐wavelength modulation is overcome by integrating the matrix (Sr 2 YGaO 5 ) and dopant (Sm 3+ ) emissions mutually together to achieve wavelength variations. Color‐changing emission is identified with a large Commission Internationale de L'Eclairage chromatic coordinate difference. The compatible coexistence of matrix/rare‐earth emission centers together with abundant photo‐active traps contributes to the superior optical integration and matrix‐emission‐assisted photochromism enables a distinct color variation in dual fields. This work provides a good example of designing one single material with color changeable characteristics in both bright and dark fields.