High performance of broad excitation and narrow emission green phosphor NaAl11O17:Eu2+, Mn2+ for backlight displays

Abstract

Long-term exposure to strong blue LED display radiations from sources such as computers and cell phones can seriously compromise sleep quality, and the development of “human-centric” trichromatic phosphors excited by UV LED chips can effectively solve this problem. Therefore, achieving narrow emission and broad excitation characteristics is one of the problems that need to be solved urgently in some phosphors for backlight displays. In this work, a highly efficient green-emitting narrow-band phosphor, NaAl₁₁O₁₇:Eu²⁺, Mn²⁺, with the emission band located at 511 nm originating from Mn²⁺, a full width at half maximum value of 27 nm, and a strong excitation in the range of 250–450 nm was realized by the sensitization of Eu²⁺. The introduction of Eu²⁺ achieved an energy transfer efficiency of 93% to Mn²⁺, resulting in an increase in the luminescence efficiency of NaAl₁₁O₁₇:0.20Eu²⁺, 0.40Mn²⁺ to 87%. In addition, the NaAl₁₁O₁₇:0.20Eu²⁺, 0.40Mn²⁺ phosphor has an extremely weak thermal quenching behavior, and the emission intensity at 423 K still reaches 79.32% at room temperature. Finally, the WLED device fabricated using a 365 nm near-ultraviolet LED chip coated with NaAl₁₁O₁₇:Eu²⁺, Mn²⁺, BaMgAl₁₀O₁₇:Eu²⁺ and K₂SiF₆:Mn⁴⁺ phosphors exhibits a wide color gamut value of 110% of the National Television System Committee (NTSC) standard. The results indicated that exploring the Eu–Mn energy transfer efficiency in a suitable inorganic matrix is an effective strategy to develop a new highly efficient narrow green-emitting phosphor with broadband excitation for wide color gamut backlight displays.