Scattering Spheres Boost Afterglow: A Mie Glass Approach to Go Beyond the Limits Set by Persistent Phosphor Composition

Abstract

Persistent luminescence phosphor nanoparticles (PersLNPs) offer exciting opportunities for anticounterfeiting, data storage, imaging displays, or AC‐driven lighting applications owing to the possibility to process them as shapable thin coatings. However, despite unique delayed and long‐lasting luminescence, the relatively low storage capacity of persistent phosphor nanoparticles combined with the difficulty of harvesting photons from transparent thin layers drastically hinder the perceived afterglow. In order to enhance persistent luminescence (PersL) of thin coatings, herein a novel approach is proposed based on resonant optical nanostructures. In particular, it is demonstrated that the integration of TiO2 scattering spheres in films (with thickness comprised between 1 and 10 µm) made of ZnGa2O4:Cr3+ PersLNPs enables a significant increase in afterglow intensity due to the combination of effective charging and enhanced outcoupling. As a result, a ≈3.5‐fold enhancement of the PersL is observed in 2 µm‐thick films stuffed with scattering centers using low‐light illumination conditions. Furthermore, inclusion of scattering centers leads to an unprecedented acceleration of the PersL charging speed. These results constitute the first example of photonic engineering applied to enhance the properties of PersL materials coatings.

Strontium Aluminate Persistent Luminescent Single Crystals: Linear Scaling of Emission Intensity with Size Is Affected by Reabsorption

“…In the case of single crystals, a more efficient outcoupling can be achieved by faceting the crystal to reduce the probability of total internal reflection or moving toward a rougher surface, which similarly limits total internal reflection . For other transparent samples, such as glasses or films, this can also be achieved through the addition of scattering centers, such as TiO 2 spheres or pores …”