On the luminescence centers in SrAl2O4:Eu,Dy and their role in the persistent luminescence process

Persistent luminescent materials are ubiquitous in our daily life, from watch dials, toys and gadgets to pictograms for emergency exit signs [1]. However the mechanism behind this persistent luminescence is not yet fully understood. Strontium aluminates doped with europium and dysprosium (SrAl2O4:Eu,Dy) is one of the most widely used persistent luminescent phosphor. It features a broad green emission band and bright long-lasting afterglow at room temperature [2]. Besides the green emission band a second, blue emission band becomes visible at low temperatures (< 220 K).