Polyhedron Transformation toward Stable Narrow-Band Green Phosphors for Wide-Color-Gamut Liquid Crystal Display

Liao, Hongxu; Zhao, Ming; Zhou, Yayun; Molokeev, Maxim S.; Liu, Quanlin; Zhang, Qinyuan; Xia, Zhiguo Source: ADVANCED FUNCTIONAL MATERIALS, 29 (30):10.1002/adfm.201901988 JUL 2019

A robust and stable narrow‐band green emitter is recognized as a key enabler for wide‐color‐gamut liquid crystal display (LCD) backlights. Herein, an emerging rare earth silicate phosphor, RbNa(Li3SiO4)2:Eu2+ (RN:Eu2+) with exceptional optical properties and excellent thermal stability, is reported. The resulting RN:Eu2+ phosphor presents a narrow green emission band centered at 523 nm with a full width at half maximum of 41 nm and excellent thermal stability (102%@425 K of the integrated emission intensity at 300 K). RN:Eu2+ also shows a high quantum efficiency, an improved chemical stability, and a reduced Stokes shift owing to the modified local environment, in which [NaO8] cubes replace [LiO4] squares in RbLi(Li3SiO4)2:Eu2+ via polyhedron transformation. White light‐emitting diode (wLED) devices with a wide color gamut (113% National Television System Committee (NTSC)) and high luminous efficacy (111.08 lm W−1) are obtained by combining RN:Eu2+ as the green emitter, K2SiF6:Mn4+ as the red emitter, and blue‐emitting InGaN chips. Using these wLEDs as backlights, a prototype 20.5 in. LCD screen is fabricated, demonstrating the bright future of stable RN:Eu2+ for wide‐color‐gamut LCD backlight application.