Treatment with Na 2 SO 3 alkaline reductant to restore luminescence intensity and improve the moisture resistance of deteriorated Mn 4+ -doped fluoride phosphors

Enhancing the moisture resistance of Mn 4+ -doped fluoride phosphors is crucial for solid-state lighting (SSL) and liquid crystal display (LCD). Herein, the deteriorated K 2 AF 6 :Mn 4+ (A = Ti, Si) phosphors were restored with Na 2 SO 3 alkaline reductant, and optimal treatment conditions were systematically determined. The kinetic process for luminescence degradation and restoration, as well as the corresponding reparation mechanism were investigated in detail. These results showed that SO 3 2− anion can reduce Mn 4+ to Mn 2+ , rapidly remove the dark-brown layer of the degradation product, and restore the luminescence intensity of K 2 AF 6 :Mn 4+ to more than 95%. Therefore, the restored K 2 TiF 6 : Mn 4+ and K 2 SiF 6 : Mn 4+ samples exhibit excellent moisture resistance, maintaining to be 66 and 76% of the initial intensity after immersing in deionized water for 300 min. Furthermore, fabricated white light-emitting device using the restored K 2 TiF 6 : Mn 4+ phosphor also possess color rendering index of 94.2 and correlated color temperature of 3270 K. Our results provide a feasible strategy to significantly improve the moisture resistance of fluoride phosphors, demonstrating a great promise in phosphor-converted white-LED toward lighting and display field.