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New cavity design boosts light output for OLED devices


August 7, 2009

The COLED-polymer combination displaying green light. (Photo: SRI International, Menlo Park,

The COLED-polymer combination displaying green light. (Photo: SRI International, Menlo Park, Calif.)

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Scientists at SRI International have found an innovative design for organic light-emitting diodes (OLED) that makes use of cavities to enhance their luminosity and energy efficiency. The device, called a COLED (where the 'c' stands for 'cavity') was designed by Dr. Yijian Shi and employs a regular pattern of cavities, implementing a structure that generates as much as five times the light output of a standard OLED per watt consumed depending on the color being displayed.

OLED displays make use of a thin organic film deposited on its surface with a simple printing process, and present several advantages compared to traditional LCD displays: most notably, they don't require a backlight to function, which allows for much thinner and power-saving displays.

Thanks to a combination of light-emitting polymers provided by the Japan-based SDK and the innovative COLED design, researchers were able to obtain an output of 30 lumens per watt for blue light — the most challenging to produce effectively with OLED technology — which was higher than any other result obtained with similar technology.

As for green light (pictured above), which is technically less challenging to produce with OLED devices, the COLED-polymer combination achieved a stunning 80 lumens per watt, about three times more than a typical OLED. The combination also proved a feasible, economic solution for the production of white light, which requires a mixture of red, green and blue light.

Finally, this new COLED device is also very promising from an environmental point of view: according to SRI, this technology could be as much as two times more energy-efficient than compact fluorescent lights, which also contain mercury and therefore present a disposal problem.

The researchers estimate that this technology could be available to consumers as soon as next year.

About the Author
Dario Borghino Dario studied software engineering at the Polytechnic University of Turin. When he isn't writing for Gizmag he is usually traveling the world on a whim, working on an AI-guided automated trading system, or chasing his dream to become the next European thumbwrestling champion. All articles by Dario Borghino
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