Enhanced narrow green emission via efficient energy transfer from Eu2+ to Mn2+ in KAl4Ga7O17 for backlit LCD displays

Abstract

Wide color gamut displays are considered a new generation of display technology owing to their excellent color saturation and color rendition. However, a significant challenge in their development is obtaining narrow-band green-emitting phosphors with high quantum efficiency and low thermal quenching. Herein, we address this challenge by constructing efficient Eu²⁺ → Mn²⁺ energy transfer in the KAl₄Ga₇O₁₇ matrix. This approach allows us to obtain a high quantum efficiency narrow-band green-emitting phosphor that can be excited by a UV LED chip. By achieving a 95.6% energy transfer efficiency of Eu²⁺ → Mn²⁺, the KAl₄Ga₇O₁₇ : 0.1Eu²⁺,0.12Mn²⁺ (KAGO:0.1Eu²⁺,0.12Mn²⁺) phosphor exhibits nearly single-band emission peak at 509 nm with a full-width at half maximum (FWHM) of only 25 nm. Moreover, the internal quantum efficiency reaches 99% under 330 nm excitation. Compared with the undoped Ga sample, this phosphor demonstrates a 2.2 times increase in luminescence intensity. This improvement can be attributed to the introduction of Ga³⁺, enhancing the absorption of phosphors. Finally, as an application demonstration, we used KAl₄Ga₇O₁₇:0.1Eu²⁺,0.12Mn²⁺ green phosphor, BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor, and K₂SiF₆:Mn⁴⁺ red phosphor in combination with a 365 nm UV LED chip to encapsulate a white LED device, which gave a color gamut area of 122% NTSC and 91% Rec.2020 with a luminous efficacy of 27.09 lm W⁻¹. Further, we fabricated a light bar and assembled it into an LCD screen. The fabricated LCD screen exhibited superior color rendition compared to ordinary commercial screens.