Cooperation between the two sides of the Taiwan Straits research and development of white LED red phosphor

White LED because of the characteristics of energy-saving, environmental protection and long life has become the next generation of lighting, the current commercial white LED mainly uses the blue chip excited YAG:Ce3+ yellow fluorescent powder, and the blue light from the wafer phosphors emit yellow light mixed into white light. But the red emission spectra of YAG:Ce3+ phosphor composition deficiency, caused by using single YAG:Ce3+ fluorescent powder can not get low temperature (CCT <4500 K), high color index (CRI >80) warm white, thus limiting its application in indoor lighting in general.

In order to solve this problem, a suitable red phosphor is added to the component to supplement the red light component, so a warm white LED with low color temperature and high color rendering index can be prepared. At present, the better performance of the commercial red phosphor for rare earth doped nitrogen (oxygen) material, but this kind of phosphor emission bandwidth is too wide, the preparation needs high luminous efficiency low due to its limitations, and the price is expensive. Therefore the development of blue chip can be effectively excited with low cost, narrow emission red phosphor especially alternative rare earth luminescent materials has become the focus of attention, this is the key to improve the luminous efficiency of the warm white LED.

K2TiF4:Mn4+ red phosphor synthesized by wet chemical method and high efficient white light emitting diode

The Chinese Academy of Sciences Professor Chen Xueyuan of Fujian has been with the Department of chemistry of National Taiwan University professor Liu Ruxi and Dr. Lin Qunzhe led the research team, for the first time by high performance ion exchange method, successfully prepared Mn4+ doped K2TiF6, K2SiF6, NaYF4 and NaGdF4 red phosphor, the phosphor in the ~460 NM has a strong absorption band (bandwidth ~50 nm), is very suitable for excitation the blue chip, and the emission of ~630 nm sharp line red emission, compared with nitrogen (oxygen) of red phosphors with high luminous efficiency.

K2TiF6:Mn4+ phosphor luminescence at room temperature the absolute quantum efficiency of 98%, better than most of the existing red phosphor, the phosphor fluorescent has good thermal stability, the 150 degree of the luminous intensity at room temperature 98%. Using the red phosphor and YAG:Ce3+ yellow phosphor combined with a warm white LED, at 60 mA driving current, color temperature 3556 K and color rendering index (Ra) 81, the lumen efficiency is up to 116 lm/W. The ion exchange preparation method developed by the research team is simple and can be prepared at room temperature and atmospheric pressure, and the raw material is cheap, so it has a good market prospect.

In addition, the research team also conducted in-depth research on the spectral properties of Mn4+ ions in fluoride matrix, by low temperature high resolution laser spectroscopy reveals the electronic structures, explain the anomalous temperature dependence of luminescence intensity, these for further research and development of such non rare earth red luminescent materials provided theory on the basis of reliable. The above findings are published in the full text of the July 2014 8 issue of the journal Nature communication (Nature. Commun. 2014, DOI:, 10.1038/ncomms5312).

In recent years, the research team led by Professor Liu Ruxi of inorganic luminescent materials in both basic and practical application, except in important international journals such as Angew. Chem., It. Edit. J. Am. Chem. Soc., Chem. Mater. Published many important works (including 4 papers published by ESI for the highly cited papers). It has been more than 60 pieces of patent.

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