Design of Eu2+-activated broadband orange-emitting phosphors with excellent luminescent performance for warm WLEDs

We report orange-emitting Sr8La0.5Na0.5Mg1.5(PO4)(7):Eu2+ (SLNMPO-0.5:Eu2+) and Sr7LaNaMg1.5(PO4)(7):Eu2+ (SLNMPO-1:Eu2+) phosphors with broad emission bands covering from 450 to 800 nm. The phosphors can be excited by n-ultraviolet and blue light efficiently. Their crystal structure, diffuse reflection spectra, photoluminescence (PL) spectra, fluorescence decay curves and thermal stability were investigated systematically. Under the excitation of 365 and 400 nm, SLNMPO-0.5:Eu2+ and SLNMPO-1:Eu2+ both exhibit better PL properties and contain more red emissions than SMPO:Eu2+. CIE coordinates of SLNMPO-0.5:Eu2+ and SLNMPO-1:Eu2+ under 365 nm excitation are (0.460, 0.497) and (0.457, 0.494), respectively. Furthermore, high-quality warm white light can be generated by fabricating warm white light-emitting diode (WLED) devices with 370 nm LED chips, BaMgAl10O17:Eu2+ commercial blue phosphor and orange-emitting SLNMPO-0.5:Eu2+ (or SLNMPO-1:Eu2+) phosphor. The correlated color temperature, R-a and color coordinates are 3880 K, 94.05, (0.3895, 0.3922) and 3736 K, 91.73, (0.4005, 0.4078) for the fabricated WLED devices with SLNMPO-0.5:Eu2+ and SLNMPO-1:Eu2+, respectively. The excellent performances indicate that SLNMPO-0.5:Eu2+ and SLNMPO-1:Eu2+ have great potential to be attractive candidates in the application of warm WLEDs.