Journal
JOURNAL OF MATERIALS CHEMISTRY C
Volume 7, Issue 26, Pages 7906-7914Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9tc02445j
Keywords
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Funding
- Strategic Priority Research Program of the CAS [XDB20000000]
- NSFC [U1805252, 21771185]
- CAS/SAFEA International Partnership Program for Creative Research Teams
- Natural Science Foundation of Fujian Province [2017I0018]
- Youth Innovation Promotion Association of CAS [2015241]
- Chunmiao Project of Haixi Institutes of the CAS [CMZX-2015-002]
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Mn4+-Doped fluoride red phosphors with excellent moisture-resistant properties and high emission efficiency are highly desired for warm white LEDs and wide gamut liquid crystal displays. Herein, we synthesized a K2NaGaF6:Mn4+ red phosphor through a co-precipitation method at room temperature. The crystallographic structure of the K2NaGaF6 host was determined based on single crystal X-ray diffraction data for the first time. A high internal photoluminescence quantum yield of 82% was achieved for the 1.81 at% K2NaGaF6:Mn4+ sample. Through low-temperature and high-resolution spectroscopic analysis, we revealed that Mn4+ ions occupy at least four distinct sites in the K2NaGaF6 crystal. One of them is assigned to the Ga3+ site with high O-h site symmetry and the other three ones possess low non-centrosymmetric site symmetries. By employing 5.51 at% K2NaGaF6:Mn4+ as a red phosphor, a warm white LED with a low correlated color temperature of 3760 K, a high color rendering index of 92 (R-a) and a luminous efficacy of 156 lm W-1 was packaged. Aging tests at 85 degrees C and 85% relative humidity on the fabricated LEDs demonstrated that K2NaGaF6:Mn4+ has a better moisture-resistant property than that of the popular K2SiF6:Mn4+ phosphor. These findings demonstrate the great potential of K2NaGaF6:Mn4+ as a highly efficient red phosphor with excellent moisture-resistant performance.
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