Highly Efficient Green-to-Yellowish-Orange Emitting Eu2+-Doped Pyrophosphate Phosphors with Superior Thermal Quenching Resistance for w-LEDs

Highly efficient green/yellowish-orange phosphors with low thermal quenching behavior are urgently required to improve the luminescence efficiency, color stability, and color rendering of phosphor-converted white light emitting diodes (w-LEDs). Herein, a novel green Cs2BaP2O7:0.01Eu(2+) phosphor with high luminescence efficiency (82.7%) and thermal quenching behavior (92.5% at 423 K) is reported. Besides, a further luminescence improvement in the quantum yield (98.9%) and thermal quenching resistance (120% at 448 K) is successfully achieved in green/yellowish-orange color-tunable Cs2MP2O7:0.01Eu(2+) (M = Ba, Sr, and Ca) phosphors. Surprisingly, these green/yellowish-orange Cs2MP2O7:0.01Eu(2+) (M = Ba, Sr, and Ca) phosphors even have a prior advantage over the commercial green beta-SiAlON:Eu2+ and yellow YAG:Ce3+ phosphors. The corresponding spectral adjustment and thermal stability mechanisms are revealed, related to the optimization of local lattice symmetry. The prototype w-LEDs exhibit warm white light with CIE color coordinate at (0.337, 0.322). The color rendering index, corrected color temperature, and luminescence efficiency can reach 92.6, 4044 K, and 152.56 lm W-1, respectively. In general, the as-reported green/yellowish-orange Eu2+-doped pyrophosphate phosphors are promising candidates in the future high-quality w-LEDs applications. The proposal of local lattice symmetry modulation can provide a new approach to exploit novel phosphors with excellent thermal quenching resistance.