Significantly enhanced the humidity resistance of a novel red phosphor CsNaGe0.5Sn0.5F6:Mn4+ through surface modification

Abstract Red phosphors based on Mn4+ doped fluorides emitting narrow red light under the excitation of blue GaN chips, which can help to improve the luminescence efficiency and color rendering index (CRI) of white light-emitting diodes (WLEDs). In this paper, we carried out a room-temperature synthesis method to obtain a new phosphor of CsNaGexSn1-xF6:Mn4+ (CNGSFM) which contains double-central ions Ge4+ and Sn4+. By controlling the different ratios of the central ions Ge4+/Sn4+, the contraction and expansion of the matrix lattice CNGSF can be freely changed, which provides a new direction for exploring the trimming method of the lattice effect on the luminescence performance of phosphors. Mn4+ in CNGSFM shows weak stability and its luminescence quenches fastly in humid environments, so that we explored a facile strategy to improve its humidity resistance. Furthermore, the quenched luminescence of the CNGSFM can be restored through surface modification. Therefore, our results not only establish the tunable mechanism between luminescence performance and microstructure, but also provide a feasible strategy to improve the humidity resistance of Mn4+ doped double-composite fluoride phosphors.