Near-UV Light-Excitable Narrow Band Green Na-β"-Al2O3: Eu2+, Mn2+ Phosphor for Wide Color-Gamut WLED Backlight Displays

Abstract

The narrow-band emission of Mn²⁺ is attractive for ultra-wide color gamut backlit displays. However, its weak blue light absorption, low quantum efficiency, and poor thermal stability limit its application. Here, a near-ultraviolet (n-UV) light-excitable narrow-band green phosphor is developed by co-doping Eu²⁺ and Mn²⁺ in Na-β"-Al₂O₃. Through the energy transfer from Eu²⁺ to Mn²⁺, Na-β"-Al₂O₃: Eu²⁺, Mn²⁺ can be efficiently excited by a commercial n-UV chip, emitting green light at 509 nm with a full width at half maximum (FWHM) of 14 nm and a color purity as high as 92%. The internal quantum efficiency (IQE) is significantly increased from 11.7% to 46.3%. Moreover, Na-β"-Al₂O₃: Eu²⁺, Mn²⁺ exhibits a near-zero-thermal quenching behavior, and the luminescence intensity at 478 K remains at 96.6% of that at room temperature. Finally, a white light-emitting diode (WLED) is fabricated by combining Na-β"-Al₂O₃: 0.15Eu²⁺, 0.1Mn²⁺ with commercial BaMgAl₁₀O₁₇: Eu²⁺ and Y₂O₃: Eu³⁺ phosphors, using a 365 nm n-UV LED chip. The fabricated device exhibits a wide color gamut of 104% of the National Television Systems Committee (NTSC) standard, indicating that the Na-β"-Al₂O₃: Eu²⁺, Mn²⁺ is promising for WLED backlight displays.