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Posted on August 2, 2007 by  & 

OLED Displays to Recycle Energy

The possibility of laptops and mobile phones collecting solar energy to recharge their batteries may be possible with research from National Taiwan University.
Organic light-emitting diodes (OLEDs) offer an alternative to conventional electronic displays (such as LCDs) and have advantages generally including wide viewing angles, rapid response and thin shapes. One area that scientists would like to improve is achieving better contrast, especially under strong lighting environments. A low-power, high-contrast OLED could provide higher quality displays for mobile electronics, and also result in longer battery lifetimes.
Scientists at National Taiwan University have found a way to improve the contrast by placing a solar cell in the back of an OLED. This can provide a contrast superior to that achieved with polarizers and generate useful electrical power. The energy that is usually wasted via photovoltaic action can be recycled. Although the scientists only achieved a power recycling efficiency of 0.26% during trials they hope to make improvements by using more efficient OLEDS and solar cells.
This feature is particularly attractive for mobile electronics, which are typically limited by power usage. With such energy recycling, the devices themselves would add a self-powering function as well as achieve higher system-level efficiency. Both attributes could contribute to longer battery lifetimes for mobile electronics.
Scientist Chung-Chih Wu explained to "I believe this is the first time a solar cell is used as part of a display device, although previously you may find some consumer electronic products carrying solar cell panels."
"Careful design of the optical structures and integration of solar cells allow us to construct OLEDs for high-performance display applications. These are high-contrast high-aperture-ratio energy-recycling self-powering devices that are compatible with active-matrix backplanes," stated Wu.
Last year Cornell University researchers developed a new type of organic semiconductor device that shows electroluminescence and acts as a photovoltaic cell. The device uses, what is called, an 'ionic junction,' which the scientists say could lead to improvements in LEDs - as organic semiconductors can be made in thin, flexible sheets, they could potentially create displays on cloth or paper - A beach umbrella that collects solar energy to run a portable TV may not be too far away.
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Also read Printed Electronics in East Asia which profiles and compares 140 organisations including National Taiwan University in this unique report.

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Business Development Director, Research

Posted on: August 2, 2007

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