Realizing thermal and moisture stability in the K2Ge1-Ti F6:Mn4+ red phosphors with high efficiency for WLEDs

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 K2Ge1-xTixF6:Mn4+ phosphors with high luminescence performances are obtained. Benefiting from the Ti4+-doping in K2GeF6, 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 K2Ge0.6Ti0·4F6:Mn4+. The moisture resistance property of K2Ge0.6Ti0·4F6:Mn4+ 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 K2Ge0.6Ti0·4F6:Mn4+ with commercial yellow phosphor on blue chips. This work proves the prospects of K2Ge1-xTixF6:Mn4+ as promising red phosphors for potentially viable application in warm white light-emitting diodes.