Cooperative R & D of red light phosphor for white LED

The white light LED has become the next generation of lighting because of its energy saving, environmental protection and long life. At present, the commercialized white light LED mainly uses blue light chip to stimulate the YAG:Ce3+ yellow phosphor, and the blue light from the wafer is mixed with the yellow light emitted by the phosphor to form white light. However, the emission spectrum of YAG:Ce3+ phosphors is insufficient, which leads to the use of a single YAG:Ce3+ phosphor that can not obtain a low correlation color temperature (CCT <4500 K) and a high color index (CRI >80) warm white light, thus limiting its application to indoor general lighting.

In order to solve this problem, a suitable red light phosphor is added to the component to supplement the red light components, so as to prepare a warm white LED with low color temperature and high color index. At present, the commercialized red luminescent powders with good performance are mainly rare earth doped nitrogen (oxygen) materials, but this kind of phosphor has the limitations of wide emission bandwidth and high pressure preparation, which leads to low efficiency and high price. Therefore, the development of low cost, narrow band emitting red phosphor, especially the replacement of rare earth luminescent materials, is the focus of attention, which is also the key to improve the efficiency of the white light LED lumen.

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

Professor Chen Xueyuan, the Fujian Institute of science and science of the Chinese Academy of Sciences, and the research team led by Professor Liu Ruxi of the National Taiwan University Department of chemistry and the post doctoral Lin Qunzhe, successfully prepared Mn4+ doped K2TiF6, K2SiF6, NaYF4 and NaGdF4 red phosphor with high efficiency ion exchange method. The phosphor has strong absorption band in ~460 nm. 50 nm), it is very suitable for the excitation of blue light chip, and its emission is red light emission from the sharp line of ~630 nm, which has higher lumen efficiency compared with the nitrogen (oxygen) red phosphor.

The absolute quantum efficiency of luminescence of K2TiF6:Mn4+ phosphors at room temperature is 98%, which is superior to most of the existing red phosphors. At the same time, the phosphor has good fluorescence thermal stability and the luminescence strength at 150 degrees reaches 98% at room temperature. Under the conditions of 60 mA driving current, 3556 K of color temperature and 81 of color index (Ra), the efficiency of the warm white light is 116 lm/W with the combination of the red light phosphor and the YAG:Ce3+ yellow phosphor. The method of ion exchange preparation 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 studied the spectral properties of Mn4+ ions in the fluoride matrix. By means of low temperature high resolution laser spectroscopy, the electronic energy level structure was revealed and its anomalous luminescence intensity temperature dependence was explained. These are the further research and development of such non rare earth red light luminescent materials. The material provides a reliable theoretical basis. The above research results were published on the 8 day line of July 2014 in "nature - Communication" (Nature. Commun. 2014, DOI: 10.1038/ncomms5312).

In recent years, the research team led by Professor Liu Ruxi has given consideration to both basic and practical applications in the research of inorganic luminescent materials, in addition to publishing important publications in important international journals such as Angew. Chem. It. Edit., J. Am. Chem. Soc., Chem. Mater, etc. (of which 4 papers are published by ESI as high cited papers) More than 60 patents have been obtained.

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