Summary: | Nowadays, Mn<sup>4+</sup>-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 K<sub>2</sub>Nb<sub>1−<i>x</i></sub>Mo<sub><i>x</i></sub>F<sub>7</sub> novel fluoride solid solution system, and synthesized the Mn<sup>4+</sup>-activated K<sub>2</sub>Nb<sub>1−<i>x</i></sub>Mo<sub><i>x</i></sub>F<sub>7</sub> (0 ≤ <i>x</i> ≤ 0.15, <i>x</i> represents the mol % of Mo<sup>6+</sup> in the initial solution) red phosphors via co-precipitation method. The doping of Mo<sup>6+</sup> not only significantly improve the moisture resistance of the K<sub>2</sub>NbF<sub>7</sub>: Mn<sup>4+</sup> phosphor without any passivation and surface coating, but also effectively enhance the luminescence properties and thermal stability. In particular, the obtained K<sub>2</sub>Nb<sub>1−<i>x</i></sub>Mo<i><sub>x</sub></i>F<sub>7</sub>: Mn<sup>4+</sup> (<i>x</i> = 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 K<sub>2</sub>Nb<sub>1−<i>x</i></sub>Mo<sub><i>x</i></sub>F<sub>7</sub>: Mn<sup>4+</sup> (<i>x</i> = 0.05) phosphor is 86.37% of its initial intensity after immersion for 1440 min, prominently higher than that of the K<sub>2</sub>NbF<sub>7</sub>: Mn<sup>4+</sup> 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 (Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>: Ce<sup>3+</sup>) and the K<sub>2</sub>Nb<sub>1−<i>x</i></sub>Mo<sub><i>x</i></sub>F<sub>7</sub>: Mn<sup>4+</sup> (<i>x</i> = 0.05) red phosphor. Our findings convincingly demonstrate that the K<sub>2</sub>Nb<sub>1−<i>x</i></sub>Mo<sub><i>x</i></sub>F<sub>7</sub>: Mn<sup>4+</sup> phosphors have a good practical application in WLEDs.
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