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Korean research team develops white LEDs with high color rendering index

To meet the desire for green growth, eco-friendly LED lights that provide effective luminosity for a long time are being used more and more for indoor lighting. Research and development is being conducted worldwide on light-emitting diodes (LEDs) that simulate natural sunlight.

The Korea Advanced Institute of Science and Technology (KAIST) announced on December 26 that one of the research teams of the school, led by Professor Bae Byeong-su, has successfully developed white LEDs using new materials for fluorescent dyes that are 80% cheaper than the current white LEDs.

The current commercialized white LEDs produce white light by mixing blue light from LED chips and either yellow or red and green fluorescent substances from an encapsulant. The fluorescent substances use inorganic substances such as oxides or oxynitrides that are produced by a complicated process.

The price for the materials is high and the core technologies for the current fluorescent substances are dominated by advanced countries like Japan and the U.S. 

However, Bae and his research team chose fluorescent dyes instead of the inorganic fluorescent substances.

(The current commercialized white LEDs have a color rendering index of 70 (Photo: Yonhap News))
Fluorescent dyes create diverse colors and are used for various purposes such as dying textiles. These cheap materials also have a wide spectrum that absorbs and releases light to create white light approximating natural lighting if used as LED fluorescent substances. Their various attributes including color temperature are adjustable in many ways.

Bae’s team developed the nanohybrid-based white LEDs that have a high color rendering index and high thermal resistance by mixing fluorescent dyes with hybrid materials. By controlling the ratio and concentration of the green and red dyes in the nanohybrid fluorescent dyes, the white LEDs can emit various color temperatures.

The nanohybrid-based white LEDs have a very high color rendering index of 89 while the index of sunlight is 100. The current commercialized white LEDs have a color rendering index of 70.

The newly developed white LEDs are evaluated as a new technology that has a strong competitive edge since it can be made easily with cheap materials.

The results of their research were reported in the December edition of Advanced Materials, a famous scientific journal covering materials science, and a patent for the LEDs is in the process of being registered.

By Jessica Seoyoung Choi Staff Writer

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