Novel Mn⁴⁺-Activated K₂Nb_1-MoF₇ (0 ≤ x ≤ 0.15) Solid Solution Red Phosphors with Superior Moisture Resistance and...

Nowadays, Mn⁴⁺-activated fluoride red phosphors with excellent luminescence properties have triggered tremendous attentions for enhancing the performance of white light-emitting diodes (WLEDs). Nonetheless, the poor moisture resistance of these phosphors impedes their commercialization. Herein, we proposed the dual strategies of "solid solution design" and "charge compensation" to design K₂Nb_1-MoF₇ novel fluoride solid solution system, and synthesized the Mn⁴⁺-activated K₂Nb_1-MoF₇ (0 ≤ x ≤ 0.15, x represents the mol % of Mo⁶⁺ in the initial solution) red phosphors via co-precipitation method. The doping of Mo⁶⁺ not only significantly improve the moisture resistance of the K₂NbF₇: Mn⁴⁺ phosphor without any passivation and surface coating, but also effectively enhance the luminescence properties and thermal stability. In particular, the obtained K₂Nb_1-MoF₇: Mn⁴⁺ (x = 0.05) phosphor possesses the quantum yield of 47.22% and retains 69.95% of its initial emission intensity at 353 K. Notably, the normalized intensity of the red emission peak (627 nm) for the K₂Nb_1-MoF₇: Mn⁴⁺ (x = 0.05) phosphor is 86.37% of its initial intensity after immersion for 1440 min, prominently higher than that of the K₂NbF₇: Mn⁴⁺ phosphor. Moreover, a high-performance WLED with high CRI of 88 and low CCT of 3979 K is fabricated by combining blue chip (InGaN), yellow phosphor (Y₃Al₅O₁₂: Ce³⁺) and the K₂Nb_1-MoF₇: Mn⁴⁺ (x = 0.05) red phosphor. Our findings convincingly demonstrate that the K₂Nb_1-MoF₇: Mn⁴⁺ phosphors have a good practical application in WLEDs.