LEDs brighten television

Two researchers want to make sure future generations of TV watchers will be able to see the brightest, most beautiful colour possible and for a lot less money.

The key to making this possible is in the LEDs that illuminate some TV screens. Making these LEDs more efficient, cheaper and of higher quality is what occupies the daily thoughts of materials science and engineering professor Yang Yang and his graduate researcher Jinsong Huang from the UCLA Henry Samueli School of Engineering and Applied Science.

Yang and Huang have recently achieved what they claim is the highest lumens per watt ever recorded for a red phosphorescent LED using a combination of plastic, or polymer, infused liquid and they did it at half the current cost.

"That means your next LED flat panel TV could be less expensive and the picture will be brighter and clearer than ever before," Yang said.

Current red LEDs generally score around 12 lumens per watt. Yang and Huang's device is 18 lumens per watt.

"That's a significant difference," Huang said.

"Visually, it means you get a higher quality display, and the product is also lighter and thinner. And with our improvements, you also need less energy, but you get an all-round better product."

Conventional organic LEDs are made from a variety of organic semiconductor materials and have a complicated multiple-layer structure formed by expensive thermal evaporation techniques constructed to control charge flow in the device. LCD televisions require polarisation, colour filters and other components to make the resulting picture clear and bright. The more you build into a product, Yang said, the more energy it takes to run it, and the bigger it is.

In Yang and Huang's polymer light-emitting diodes (PLED), the devices have a very simple single-layer structure, generated by a much cheaper process that uses a polymer powder and liquid mixture added to a previously top-secret material developed by Canon to create a paint-like product. This is used to coat a layer of glass and a charge is added. The end result is a slim single layer of glass with two electrodes.

"It's a much simpler, lighter, thinner and more elegant answer to creating a better LED product," Yang said.

Yang began his high-performance PLED research at UCLA Engineering in early 2003.

"The current results represent an ongoing quest to create better, slimmer, less expensive high-performance PLEDs," Yang said.

"Using our simple solution method, we already have achieved several world records in device efficiency, including 20 lumens/watt white emission fluorescent PLEDs, 30 lumens/watt green emission fluorescent PLEDs and 18 lumens/watt red emission phosphorescent PLEDs. So our latest red emission PLED is just one of our multiple records. It's a very exciting development."

The new technology, which already has been licensed by Canon, should be available to consumers in about three years.