Excitation Strategy of Infrared Persistent Phosphors via Upconversion Charging and Persistent Energy Transfer

Infrared persistent phosphors are a kind of attractive luminescent material featuring long-lasting afterglow emission and an invisible emission wavelength. Compared with the increasing attention paid to the emission performance, research on the excitation for charging the infrared persistent phosphors is relatively lacking. Here, we explore the charging approach of infrared persistent phosphors by using visible lasers and/or a high-power white flashlight as excitation sources. As a proof of concept, we focus our attention on Cr³⁺, Yb³⁺, and Ni²⁺-codoped LaMgGa₁₁O₁₉ phosphors. Upon illumination with the lasers or flashlight, the high-energy delocalized state of the Cr³⁺ ion is populated by absorbing two visible photons, followed by charging of the phosphor. Subsequently, via a persistent energy-transfer process from the Cr³⁺ to Yb³⁺ and Ni²⁺, infrared afterglow emission with a maximum at 1260 nm is achieved in the phosphor. The present results outline a fundamental principle to develop excitation technology based on upconversion charging (UCC) and persistent energy transfer, paving a way toward further developing infrared persistent phosphors.