Long persistent light emitting diode

Light emitting diodes (LEDs) coated with Sr2MgSi2O7:Eu2+,Nd3+ (blue), SrAl2O4:Eu2+,Dy3+ (green), SrS:Eu2+,Y3+,Ce3+ (orange), and CaS:Eu2+,Tm3+,Ce3+ (red) long persistent phosphors were prepared. LEDs which have a 450 nm blue emission were used as an excitation source for the coated phosphors. Blue (475 nm), green (520 nm), orange (606 nm), and red (650 nm) emissions of the phosphors were found for each coated LED. Long persistent afterglow emissions from the phosphors excited by using LEDs were obtained. The persistence time of the phosphors' afterglow emissions coated on LEDs is found in the same order of magnitude as the phosphorescence persistence time of the long persistent phosphors. (c) 2006 American Institute of Physics.