The roles of dopant concentration and defect states in the optical properties of Sr2MgSi2O7:Eu2+, Dy3

The blue-emitting Sr2MgSi2O7:Eu2+,Dy3+ was prepared by sol-gel method. The effects of dopant concentration on crystal structure, photoluminescence and afterglow properties were studied. Based on First-principles calculations, the formation difficulty and electronic structures of intrinsic defects and the external defects caused by doping Eu, Dy were predicted, and the defect-dominated persistent luminescence mechanism was proposed. The results showed that when the content of Eu2+ reached 0.03 mol%, Sr2MgSi2O7:Eu2+,Dy3+ had the best luminescence performance. After exceeding this content, the concentration quenching caused by electric dipole-dipole interaction would occur, leading to a decrease in luminescence intensity. The oxygen vacancy as an intrinsic defect was more easily formed in Sr2MgSi2O7. The impurity levels in the forbidden band, which were introduced by oxygen vacancies and Dy doping defects, can effectively capture and release Eu electrons. It is beneficial to prolong the afterglow duration of Eu 4f65d1→Eu 4f7. This work reveals the electron transition and capture paths in the luminescence of Sr2MgSi2O7:Eu2+,Dy3+, which has reference significance for designing defect structures and optimizing optical properties. •Concentration quenching of Eu2+ was ascribed to the dipole-dipole interaction.•The impurity levels introduced by VO1 and DySr could capture and release Eu 4 f electrons.•The persistent luminescence mechanism dominated by defects was proposed.