Enhancement of waterproofness and luminescence thermostability of K2SiF6:Mn4+,Li+ by coating with GQDs and surface passivation

Mn4+- doped fluoride red luminescence phosphor can effectively improve the white light quality of white light emitting devices (WLEDs), but its poor waterproofness and luminescence thermostability hinder its application. In this work, a strategy for synthesizing KSF-MLG-P red luminescence phosphor (KSF-MLG = K2SiF6:0.05 Mn4+, 0.04Li+@GQDs (6 mg/ mol), P = passivation, GQDs = graphene quantum dots.) is proposed with an incorporation of hydrogen peroxide solution-free hydrothermal synthesis, hydrothermal coating and surface passivation methods. The characterization results indicate that it has strong luminescence, luminescence thermostability and waterproofness. The enhancement mechanism of luminescence performances is also discussed. A prototype WLED was assembled by a mixture of phosphors of KSF-MLG-P and YAG:Ce3+ with an InGaN chip. It produces warm white light with favourable performances (CCT = 3828 K, Ra = 91.1 +/- 2.0, luminescent efficiency = 101.8 +/- 2.1 lm W-1). So, it could be a vital candidate for WLED uses.