A facile self-passivation strategy for improving moisture-resistance of fluoride red phosphors without surface modification

Abstract Mn4+-activated fluorides rank among the most significant red phosphors for white light emitting diodes (LEDs) with enhanced color rendition, while their poor moisture resistance hinders further application. Surface coating with a protective layer is general approach to improving moisture resistance. However, these methods usually suffer from complex post-processing and poor shell stability. Herein, the introduction of passivation ions (Nb5+) may suppress the hydrolysis of [MnF6]2–, which provides a facile approach to obtaining moisture-resistant fluoride phosphors. Compared to K2TiF6:5.0%Mn4+, the moisture resistance and luminescence intensity of K2Ti0.949Nb0.051F6.051:5.0%Mn4+ improved significantly following the addition of Nb5+. In addition, the combination of as-prepared K2Ti0.949Nb0.051F6.051:5.0%Mn4+ red phosphor, YAG:Ce yellow phosphor and blue-chip enables the production of warm white LEDs with excellent color rendition (Ra = 90.2), low correlated color temperature (CCT = 3816 K), and high luminous efficacy (132.2 lm/W).