Enhanced quantum efficiency and moisture-resistant red-emitting K3AlF6:Mn4+ phosphor for high color rendering index WLED

Coating hydrophobic material on surface of Mn4+ doped fluoride to improve their moisture resistance often decreases the luminescent intensity of the materials. To dress this issue, K3AlF6:Mn4+ (KAFM) phosphor was synthesized in a special approach to enhance its optical properties and moisture resistance. Specifically, KAFM phosphor was synthesized with the addition of KF (KKAFM). The luminescent intensity and thermal stability of the KKAFM phosphor may be higher 2.4 times and 1.9 times (at 413 K) than the KAFM phosphor, respectively. In addition, the internal quantum efficiency (IQE) of the KKAFM phosphor reached 89.5%, which is 1.33 times higher than the KAFM phosphor. The KKAFM phosphor retained 82 % of the original emission value after 31 days of immersion in water, and 98% after exposure to high temperature and humidity for 105 days. Meanwhile the KAFM phosphor maintains only 1.4% and 65%, respectively. Furthermore, white light-emitting diode (WLED) using KKAFM phosphor retained 74.4% of its original efficacy even after aging for 105 days. This is comparable to the 86.3% retention rate achieved using only YAG:Ce3+ phosphor. In brief, these findings help to illustrate the effect of luminescence on fluoride and provide a novel pathway for water-resistant fluoroaluminates and fluorogalliumates phosphors.