Highly Efficient Narrow-Band Green-Emitting Na<sub>3</sub>K<sub>5</sub>(Li<sub>3</sub>SiO<sub>4</sub>)<sub>8</sub>:Eu<sup>2+</sup> Phosphor with Low Thermal Quenching
Yujia Wan, Peipei Dang, Dongjie� Liu, Qianqian Zhang, Yi Wei, Hongzhou Lian, Guogang Li, Jun Lin
Abstract
In the pursuit of high efficiency and wide color gamut in displays, there is still an urgent demand for high-performing narrow-band green-emitting phosphors. Inspired by a mineral UCr 4 C 4 -type structure with a highly condensed framework, a novel narrow-band green-emitting Na 3 K 5 (Li 3 SiO 4 ) 8:Eu 2+ (NKLSO:Eu 2+ ) phosphor is designed. This phosphor exhibits a green emission peaking at 525 nm with a full width at half-maximum (fwhm) of 43 nm. The narrow-band emission is associated with the highly symmetric sites for Eu 2+ . Benefiting from its high structural rigidity, this NKLSO:Eu 2+ phosphor shows a very low photoluminescence (PL) thermal quenching, maintaining 96%@150 °C integrated PL intensity of the original PL intensity. Moreover, by incorporating a small amount of Al 3+ into the lattice, the internal quantum efficiency (QE) and external QE of this phosphor is enhanced from 70 to ∼100% and 21 to 38%, respectively. The as-fabricated wLED-1 (InGaN chip@blue, NKLSO:1.25% Eu 2+ @green, KSiF 6:Mn 4+ @red) shows a wide color gamut (106% NTSC), demonstrating vivid photographs when used in a projector. The as-fabricated wLED-4 (BaMgAl 10 O 17:Eu 2+ @blue, NKLSO:1.25% Eu 2+ @green, CaAlSiN 3:Eu 2+ @red) presents a low correlated color temperature of 5390 K and a high color rendering index (Ra) of 86.9. These results show that narrow-band green-emitting NKLSO:Eu 2+ has potential applications in both backlight displays and solid-state lighting.