Wide range yellow emission Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ phosphors for near ultraviolet white LEDs

Abstract

A series of single phased phosphors Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ were synthesized by solid state reaction methods for applications of white light emitting diodes(w-LEDs). The broad absorption band at the near ultraviolet (NUV) region of 250–450 nm was obtained, which is ascribed to the 4f7→ 4f65d1 electronic transition of the Eu2+ ions. Under NUV excitation, the broad yellow emission was obtained from tri-activated Sr8MgLa(PO4)7 phosphors via combining three emission bands centered at 500, 550, and 600 nm contributed by Eu2+, Tb3+ and Mn2+, respectively. The optimized concentrations of Mn2+ and Tb3+ were 6 mol%, respectively, which enhanced the total PL intensity up to 30% comparing to only Eu2+ doped phosphor. Moreover, the quantum efficiency of Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ phosphor had achieved up to 52%. The combination of a NUV chip with compound of Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ and BaMgAl10O17:Eu2+ achieved tunable w-LEDs with high CRI. The results suggest that this single phased Sr8MgLa(PO4)7: Eu2+, Mn2+, Tb3+ phosphor can be a key for the phosphor converted w-LEDs for warm white light emission.