Insights of phosphor charging upon exposure to intense illumination

Storage phosphors, known for their delayed emission after charging, have shown great potential for applications in radiation detection, bio-imaging, and medical diagnosis. Despite their promise, the underlying mechanisms governing their charging behavior have not been sufficiently investigated. In this Letter, we elucidate the response of storage phosphors, focusing on the Y₃Sc₂Ga₃O₁₂:Pr³⁺ composition, when subjected to intense illumination. Our findings reveal that upon exposure to 266 nm ultraviolet or 450 nm blue lasers, the phosphor efficiently captures excitation energy through direct photoionization or upconversion charging (UCC), leading to subsequent trap filling. Thermoluminescence measurements, incorporating variations in irradiation power and dose, confirm that UCC enables an impressive fast charging time of 0.01 s. The unique two-step ionization and nonlinear charging characteristics of UCC are visually demonstrated using a portable laser engraver. Furthermore, we illustrate the versatility of UCC across different phosphor systems, highlighting its potential for advanced information storage applications. This research significantly advances the understanding of phosphor charging dynamics, paving the way for future innovations in luminescent materials.