Persistent luminescence in rare earth doped oxynitrides

In 1996, SrAl2O4:Eu 2+ codoped with Dy ions was developed as an efficient persistent luminescent material with a very long afterglow [1]. This fact, combined with global efforts to reduce energy consumption of light sources, has led to a renewed interest in the class of long persistent luminescent materials. However, large scale application in safety illumination, emergency and road signage, ... is hampered by the limited number of different colors available, especially in the long wavelength part of the visible spectrum. Therefore, the quest for phosphors with better specifications and different emission spectra is still open.