Realizing thermal and moisture stability in the K2Ge1-Ti F6:Mn4+ red phosphors with high efficiency for WLEDs
Lei Feng, Shuangyan Pi, Jun Zheng, Wenfei Liang, Juntao Li, Ting Zhou, Mengjiao Liu, Yan Zhao, Xin Lai, Jian Bi, Daojiang Gao
Abstract
Developing red light-emitting phosphors with high performances is an imperative issue for achieving high-quality warm white light-emitting diodes. Here, red light-emitting K 2 Ge 1- x Ti x F 6 :Mn 4+ phosphors with high luminescence performances are obtained. Benefiting from the Ti 4+ -doping in K 2 GeF 6 , a high internal quantum yield of 96% can be obtained. The emission intensity at 423 K keeps 83% of the initial value at 298 K in K 2 Ge 0.6 Ti 0·4 F 6 :Mn 4+ . The moisture resistance property of K 2 Ge 0.6 Ti 0·4 F 6 :Mn 4+ is significantly enhanced and can keep 71% of the original luminescence intensity after immersing in deionized water for 180 min. A warm white light-emitting diode with high color rendering index of 92.4, low correlated color temperatures of 3113 K, and high luminous efficiency of 123.1 l m/W is simultaneously obtained by encapsulating K 2 Ge 0.6 Ti 0·4 F 6 :Mn 4+ with commercial yellow phosphor on blue chips. This work proves the prospects of K 2 Ge 1- x Ti x F 6 :Mn 4+ as promising red phosphors for potentially viable application in warm white light-emitting diodes.