New discovery may open the door for energy-efficient lighting

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London, July 16 : Scientists at the University of Michigan and Princeton University have devised a way to deliver significantly more bright light from a watt than incandescent bulbs.

"Our demonstration here shows that OLEDs are a very exciting technology for use in interior illumination," Nature Photonics quoted Stephen Forrest, U-M professor of electrical engineering and physics and vice president for research, as saying.

"We hope that white emitting OLEDs will play a major role in the world of energy conservation," he added.

Forrest and co-author Yuri Sun, visiting U-M from Princeton University, say that the new generation of lighting called white organic light-emitting devices (WOLED) show promise of providing a light that's much easier to manipulate, while being long lasting and able to provide in different shapes, from panels to bulbs and more.

WOLEDs generate white light by using electricity to send an electron into nanometer thick layers of organic materials that serve as semiconductors.

The carbon-based materials are dyes, the ones used in photographic prints and car paint, so they are very inexpensive, and can be put on plastic sheets or metal foils, further reducing costs.

The excited electron in such layers casts bright white light.

Forrest pointed out that the bad news had been that nearly 60 per cent of it would be trapped inside the layers, much the way light under water reflects back into the pool, making the water surface seem like a mirror when viewed from underneath.

In their research paper, the researchers describe a tandem system of organic grids and micro lenses that guide the light out of the thin layers and into the air.

They say that the grids refract the trapped light, bouncing it into a layer of dome-shaped lenses that then pull the light out.

According to the researchers, this process can emit about 70 lumens from a single watt of power.

"If you can change the light efficiency by just a few percentage points, there's a few less coal plants you'll need," Forrest said.

Gary Was, the director of U-M's Michigan Memorial Phoenix Energy Institute, said that the WOLED work is one example of how science can open new doors in conservation, said Gary Was, institute director.

"That energy efficient lighting can be made from the same materials as car paint and that they can be made in such thin, formable sheets boggles the mind. This is one of many exciting creations that research is giving us in the pursuit of energy efficiency. This is also the kind of innovation that is required in the drive for energy sustainability," Was said.

Forrest said that WOLEDs could be framed in different forms.

"Plugging into a wall at low voltage, putting it on a flexible metal foil, or on plastic that won't break when you drop it. This is what makes it so fun because it's such a unique lighting source," Forrest said.

He said that the next challenge was to reduce the cost to be commercially competitive.

"You have to be able to do this dirt cheap. People don't spend much for their light bulbs," Forrest said.

ANI

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