Treatment with Na2SO3 alkaline reductant to restore luminescence intensity and improve the moisture resistance of deteriorated Mn4+-doped fluoride phosphors.

Enhancing the moisture resistance of Mn⁴⁺-doped fluoride phosphors is crucial for solid-state lighting (SSL) and liquid crystal display (LCD). Herein, the deteriorated K₂AF₆:Mn⁴⁺ (A = Ti, Si) phosphors were restored with Na₂SO₃ 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 SO₃²⁻ anion can reduce Mn⁴⁺ to Mn²⁺, rapidly remove the dark-brown layer of the degradation product, and restore the luminescence intensity of K₂AF₆:Mn⁴⁺ to more than 95%. Therefore, the restored K₂TiF₆: Mn⁴⁺ and K₂SiF₆: Mn⁴⁺ 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 K₂TiF₆: Mn⁴⁺ 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. [ABSTRACT FROM AUTHOR]