Recent Advances in Long-Persistent Luminescence in Rare-Earth-Doped Compounds

The extremely long-persistent photoluminescence of Eu(II)-doped (and co-doped with Dy(III) ions) strontium aluminum oxide (SrAl2O4: Eu2+, Dy3+) was firstly reported on 1996 by Matsuzawa and coworkers. The long-persistent photoluminescence of SrAl2O4: Eu2+, Dy3+ was more than 10 folds brighter than the formerly reported copper and cobalt co-doped zinc sulfide. Thus, more efforts toward efficient long-lasting phosphors have been growing. However, the number of long-lasting phosphors is still relatively low. Moreover, the mechanisms on long-lasting luminescence are still shrouded in mystery. In this review, we introduce a comprehensive study on the significant classes of Eu(II)-doped long-persistent luminescence materials. We focus on the synthesis methods, Eu(II)-emission, and proposed mechanisms to give explanation for the afterglow.