Moisture-resistant and highly efficient narrow-band red-emitting fluoride phosphor K2NaGaF6:Mn4+ for warm white LED application. Issue 26 (12th June 2019)

• Record Type: Journal Article
• Authors: Gao, Jun; Zhu, Haomiao; Li, Renfu; Huang, Decai; Luo, Benlong; You, Wenwu; Ke, Jianxi; Yi, Xiaodong; Shang, Xiaoying; Xu, Jin; Deng, Zhonghua; Xu, Li; Guo, Wang; Chen, Xueyuan
• Is Part Of: Journal of materials chemistry. Volume 7:Issue 26(2019)
• Page Start: 7906
• Page End: 7914
• Publication Date: 2019-06-12
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc02445j
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : The site occupation/evolution of Mn 4+ ions in K2 NaGaF6 crystals and their excellent moisture-resistant performance. Abstract : Mn 4+ -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 K2 NaGaF6 :Mn 4+ red phosphor through a co-precipitation method at room temperature. The crystallographic structure of the K2 NaGaF6 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% K2 NaGaF6 :Mn 4+ sample. Through low-temperature and high-resolution spectroscopic analysis, we revealed that Mn 4+ ions occupy at least four distinct sites in the K2 NaGaF6 crystal. One of them is assigned to the Ga 3+ site with high O h site symmetry and the other three ones possess low non-centrosymmetric site symmetries. By employing 5.51 at% K2 NaGaF6 :Mn 4+ 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 °C and 85% relative humidity on the fabricated LEDs demonstrated that K2 NaGaF6 :Mn 4+ has a better moisture-resistant property than that of the popular K2 SiF6 :Mn 4+ phosphor. These findings demonstrate the great potential of K2 NaGaF6 :Mn 4+ as a highly efficient red phosphor with excellent moisture-resistant performance.