Evaluation of oxygen defect levels of afterglow phosphor Sr 2 MgSi 2 O 7 :Eu, Dy using first-principles calculations

Abstract To investigate the position of oxygen defect levels in the long afterglow phosphor Sr 2 MgSi 2 O 7 (SMS) and their effect on SMS optical properties, we evaluated the oxygen defect levels in SMS using first-principles calculations based on density functional theory. The calculated DOS results revealed that, contrary to the conventional view that oxygen defect levels appear on the conduction band side and function as electron traps, they actually appear on the valence band side. Furthermore, DOS analysis of SMS containing oxygen defects and doped with Eu and Dy suggests that oxygen defects form levels originating from the f orbitals of rare Earth elements within the band gap, which may influence the afterglow mechanism.