Investigation of the long afterglow mechanism in SrAl2O4:Eu2+/Dy3+ by optically stimulated luminescence and thermoluminescence

After the discovery of new-generation persistent luminescence materials based on Eu2+, there are many debates on their long-lasting mechanism. In this work, SrAl2O4:Eu2+/Dy3+ codoped and single doped samples were analyzed by optically stimulated luminescence and thermoluminescence to clarify the long afterglow mechanism involved. The phenomenon that persistent luminescence can be realized by the excitation of 475 nm laser in SrAl2O4:Eu2+, Dy3+ evidenced that the energy of Dy3+ can transfer to Eu2+ eventually in SrAl2O4:Eu2+, Dy3+. And the optically stimulated luminescence under the excitation of 980 nm both in SrAl2O4:Eu2+, Dy3+ and SrAl2O4:Eu2+ indicated that the electron traps caused by oxygen vacancies were significant for the long-lasting luminescence. The distribution of trap depth was precisely discussed as well by analyzing a series of thermoluminescence results with varying excitation temperature, and it showed the dysprosium doping introduced a shallow trap type with depth less than 0.65 eV. This work presents a clear view of the mechanism of the persistent luminescence in SrAl2O4:Eu2+, Dy3+, and could be generalized to the other analogous long afterglow materials based on Eu2+.