U.S Scientists have Developed Warm White LED Light New Materials

Warm white LED lights have been developed

As we all know, LED (light emitting diode) lights are energy efficient and have longer life expectancy, but the current LED lights are mainly light blue luminescent lights, which hindered its popularity in the field of indoor wholesale lighting. Today, warm white LED lights have been developed by scientists at the University of Georgia, USA, which are said to be the world's first to use single phosphor and single light-emitting unit. The paper details about this material are published in the latest issue of Optical Science and Applications journal of Nature Publishing Group.

Two indicators to measure the quality of artificial light

The paper's lead author, Pan Zhengwei, associate professor at the University of Georgia said: "At present, the white LED lamp is used on flash and auto headlights, the light blue luminescent they emit is less likable, especially in indoor lighting field. Our materials have achieved warm color temperature, while at the same time achieved a realistic color reproduction. The LED lights earlier improved using single phosphor failed to achieve this effect. "Pan Zhengwei said, there are two indicators to measure the quality of artificial light. Correlated color temperature is used to measure the well-being of the light. For indoor lighting, color temperature lower than the temperature of 4000K (Kelvin) is ideal and correlated color temperature higher than 5000K, the light will emit light blue luminescent like white LED t5 light fixture. Another important indicator is the color reproduction that is the ability of the light source to simulate natural light. Reduction degree reach more than 80 is ideal for indoor lighting, below this value the color will be very distortion.

The material developed by Pan Zhengwei and his colleagues meet these two conditions, correlated color temperature is controlled below 4000K and color reproduction reaches 85. Pan Zhengwei said coat the outer layer of blue LED chip with different colors phosphor is able to issue warm white light, which would then make phosphor-based white LED lights. However, these raw materials are laborious and cost money in accordance with the precise ratio, and eventually the light color will be different, because each raw material has not the same reaction to temperature change. One of the authors of the paper, Doctor Li Xufan, Engineering of the University of Georgia in Reading said: "Using single phosphor can solve the problem of instability in the light color, because single material does not change as the temperature rises."

The new material still needs to solve some problems before being applied in lighting

In order to develop new phosphors, Pan Zhengwei and his team selected europium oxide, aluminum oxide, barium oxide and graphite, each of which are taken to a small amount and mingled together. Then they put these powdery materials into a tube furnace and heat to 1450 degrees Celsius. The vacuum state in the furnace makes the vaporized material onto the chassis, and deposited as yellow light-emitting compound, and then put inside the bulb. Though research results are promising, Pan Zhengwei stressed that they need to resolve a few problems to apply this material in the lighting for homes, businesses and schools. The luminous efficiency of the new material is much lower than the light blue white LED lights. In addition, large-scale production will face challenges.

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