Color variation of photo-stimulated luminescence in strontium ortho-silicate with the assistance of trap centers

A large enhancement of photo-stimulated luminescence by co-doping Tm3+/Dy3+ in α′-Sr2SiO4 was observed, upon the infrared (IR) stimulation at 980 nm after pre-exposure with Ultraviolet (UV) light. More interestingly, the color of PSL changes from green to yellow with substituting Dy3+ with Tm3+. The results indicate that co-doping of Tm3+ generates a large number of traps peaking at 400 K, which able to immobilized the carriers permanently at room temperature and is more sensitive to IR light than other traps. It induced the redistribution of trap centers, especially around the emission center Eu2 which located at another inequivalent site.