The strength of the photoluminescence excitation (PLE) spectrum of SrMgAl10O17:Eu2+, Mn2+ (SAM:Eu2+, Mn2+) phosphor increased at deep blue (∼430 nm) and red-shifted from violet to deep blue with increasing concentrations of both Eu2+ ions Mn2+ ions. Eu2+-Mn2+ energy transfer between Eu2+ ions in Sr-O layer and Mn2+ ions at Al-O tetrahedral sites was maximized, and the photoluminescence (PL) intensity of the narrow-band Mn2+ emission was improved by optimizing the concentrations of Eu2+ and Mn2+ ions. The PL emission spectrum of the (Sr0.6Eu0.4)(Mg0.4Mn0.6)Al10O17 (SAM:Eu2+, Mn2+) phosphor peaks was optimized at 518 nm at a full width at half-maximum (FWHM) of 26 nm under light-emitting diode (LED) excitation at 432 nm LED. The color gamut area of a color-filtered RGB triangle of down-converted white LEDs (DC-WLEDs) incorporated with optimum SAM:Eu2+, Mn2+ green and K2SiF6:Mn4+ (KSF:Mn4+) red phosphors is enlarged by 114% relative to that of the NTSC standard system in the CIE 1931 color space. The luminous efficacy of our DC-WLED was measured and found to be ∼92 lm/W at 20 mA. Increased energy transfers between dual activators and red-shifted band-edge and enhanced intensity of PLE spectrum indicate the possibility of developing dual-activated narrow-band green phosphors for wide-color gamut in an LCD backlighting system.
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