Ultrafast
Self-Crystallization of High-External-Quantum-Efficient Fluoride Phosphors
for Warm White Light-Emitting Diodes
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Abstract
In
this study, we used HF (as good solvent) to dissolve K<sub>2</sub>GeF<sub>6</sub> and K<sub>2</sub>MnF<sub>6</sub> and added ethanol
(as poor solvent) to cause ultrafast self-crystallization of K<sub>2</sub>GeF<sub>6</sub>:Mn<sup>4+</sup> crystals, which had an unprecedentedly
high external quantum efficiency that reached 73%. By using the red
phosphor, we achieved a high-quality warm white light-emitting diode
with color-rendering index of <i>R</i><sub>a</sub> = 94, <i>R</i>9 = 95, luminous efficacy of 150 lm W<sup>–1</sup>, and correlated color temperature at 3652 K. Furthermore, the good–poor
solvent strategy can be used to fast synthesize other fluorides
