China has made progress in the research of green phosphors for LED
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In recent years, many promising phosphors have been developed, in which nitrides have received extensive attention due to their high chemical stability and thermal stability. When the white LED is operated, the chip temperature is about 150 Â° C. At this temperature, the luminous efficiency of the nitride phosphor is usually maintained at 80-90% of the efficiency at room temperature, showing good thermal stability. However, the synthesis conditions of nitrides are harsh, and high nitrogen or ammonia pressure (100 MPa), high temperature (1400-2000 Â° C) and long reaction time are required in the preparation process. These factors lead to the cost of nitride phosphors. Very high. Therefore, the development of new phosphors with higher efficiency and better thermal stability is still the goal pursued by people.
Researchers Liu Yongfu, Jiang Jun and Jiang Haochuan from the Institute of Materials Technology and Engineering, Chinese Academy of Sciences, use solid-phase reaction at relatively low reaction temperatures (1200-1400 Â° C) and short reaction times (2-4 h). An orthosilicate green phosphor was prepared. The best excitation peak of the phosphor is at 400 nm, matching the emission wavelength of the ultraviolet (UV) chip. Under the excitation of 400nm light source, the green phosphor has an emission peak at 490nm, a full width at half maximum of 120nm, and a room temperature fluorescence quantum efficiency of 82%, reaching the level of most nitrides (the quantum efficiency of nitride fluorescent materials is usually 70-90%). ). At 160 Â° C, the fluorescence quantum efficiency can be maintained at 94% of room temperature, indicating that the thermal stability of the green phosphor is better than most of the nitride phosphor, which is mainly due to the formation of LuO6 octahedron and SiO4 tetrahedron. The common apex of SiO4-LuO6-SiO4 is rigidly connected. At the same time, the raw material for preparing the green phosphor is easy to obtain and the synthesis process is simple, which greatly reduces the product cost, which provides a competitive material selection for the application of the white LED lighting device based on the UV-LED chip.
Relevant basic research results were published in the international journal Advanced Optical Materials (2015, DOI: 10.1002/adom.201500078).
The work was supported by the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, the Ningbo Natural Science Foundation, and the Ningbo Science and Technology Innovation Team (2014B82004).
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