A phenomenological theory about effective afterglow centers in persistent luminescence phosphors

Abstract

Afterglow energy storage materials, also known as photovoltaic cells, can continuously emit luminescence for a few minutes to hours, demonstrating enormous potential applications in many fields. However, due to the mysterious nature of their energy storage traps, the development of afterglow materials has largely remained in a state of trial and error. Here, encouraged by the rich intrinsic defects such as the anti-site defects of Li⁺ and Ga³⁺ and oxygen-related defects in LiGa₅O₈ (LGO)-based phosphors, LGO:Bi³⁺,Ln³⁺ (LnTb and Eu) and LGO:Cr³⁺,Ln³⁺ (LnCe, Pr, Tb, Nd and Dy) phosphors were developed to explore the criteria of doping ions as effective afterglow centers. A phenomenological theory on effective afterglow centers has been proposed based on the energy-resonance degree between the energy levels of luminescence center and defect states through the analysis of multi-color and multi-mode spectra, dynamic afterglow spectra, thermoluminescence curves, X-ray photoelectron spectroscopy, and band theory calculations. This study provides a theoretical basis for the rational design of efficient afterglow materials and offers new insights into unveiling the afterglow mechanism.