Refractive Index and Strain Modulation Tailor the Afterglow of Nanocomposite Films

Tailoring the unique delayed and long-lasting luminescence of persistent phosphors is crucial for their application in anticounterfeiting, data storage, imaging displays, and AC-driven lighting. We introduce a novel strategy to achieve this by modifying the refractive index of persistent phosphor transparent coatings. Specifically, we developed ZnGa₂O₄:Cr³⁺/SiO₂ nanocomposite films with tunable refractive indices from 1.45 to 1.7. This tunability allowed us to precisely control the Cr³⁺ radiative decay rate, resulting in a substantial 1.7-fold increase in both luminescence and afterglow brightness. Furthermore, our approach uniquely influences the intrinsic charging rate of the phosphor, a mechanism attributed to the strain induced on the ZnGa₂O₄:Cr³⁺ nanocrystals by the presence of SiO₂. This work demonstrates an unprecedent ability to manipulate the afterglow kinetics without altering the material composition, opening new avenues for designing and optimizing persistent luminescence materials.