Narrow-Band SrMgAl₁₀O₁₇:Eu²⁺, Mn²⁺ Green Phosphors for Wide-Color-Gamut Backlight for LCD Displays

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 (Sr_0.6Eu_0.4)(Mg_0.4Mn_0.6)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.