Advance brings low-cost, bright LED lighting closer ...( WEST LAFAYETTE Ind. - Researchers at...)

WEST LAFAYETTE, Ind. - Researchers at Purdue University have overcome a major obstacle in reducing the cost of "solid state lighting," a technology that could cut electricity consumption by 10 percent if widely adopted.

The technology, called light-emitting diodes, or LEDs, is about four times more efficient than conventional incandescent lights and more environmentally friendly than compact fluorescent bulbs. The LEDs also are expected to be far longer lasting than conventional lighting, lasting perhaps as long as 15 years before burning out.

"The LED technology has the potential of replacing all incandescent and compact fluorescent bulbs, which would have dramatic energy and environmental ramifications," said Timothy D. Sands, the Basil S. Turner Professor of Materials Engineering and Electrical and Computer Engineering.

The LED lights are about as efficient as compact fluorescent lights, which contain harmful mercury.

But LED lights now on the market are prohibitively expensive, in part because they are created on a substrate, or first layer, of sapphire. The Purdue researchers have solved this problem by developing a technique to create LEDs on low-cost, metal-coated silicon wafers, said Mark H. Oliver, a graduate student in materials engineering who is working with Sands.

Findings are detailed in a research paper appearing this month in the journal Applied Physics Letters, published by the American Institute of Physics.

LEDs designed to emit white light are central to solid-state lighting, semiconducting devices made of layers of materials that emit light when electricity is applied. Conventional lighting generates light with hot metal filaments or glowing gasses inside glass tubes.

The LEDs have historically been limited primarily to applications such as indicator lamps in electronics and toys, but recent advances have made them as bright as incandescent bulbs.

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