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Last Updated: Thursday, 13 April 2006, 11:04 GMT 12:04 UK
Natural light 'to reinvent bulbs'
Light bulb in front of a clock
The clock is ticking for light bulbs
A light source that could put the traditional light bulb in the shade has been invented by US scientists.

The organic light-emitting diode (OLED) emits a brilliant white light when attached to an electricity supply.

The material, described in the journal Nature, can be printed in wafer thin sheets that could transform walls, ceilings or even furniture into lights.

The OLEDs do not heat up like today's light bulbs and so are far more energy efficient and should last longer.

They also produce a light that is more akin to natural daylight than traditional bulbs.

"We're hoping that this will lead to significantly longer device lifetimes in addition to higher efficiency," said Professor Mark Thompson of the University of Southern California, one of the authors of the paper.

Old fashioned

Traditional light bulbs were invented more than 130 years ago. Since then the basic principle of creating light remains the same, although the design has been tweaked.

An electric current passing through a tungsten wire causes it to heat up and glow white hot.

Today, more than 20% of electricity used in US buildings is eaten up by lights and nearly half that amount is used by traditional, incandescent light bulbs.

It has been a long-term goal of scientists to come up with something that would reduce this mammoth energy demand.

The new work exploits the properties of carbon-based polymers to produce the white light. These are already found in some mobile phone displays and MP3 players.

Light bulb

Until now, they have been unable to generate sufficient light to illuminate a room.

To create the new material, the scientists build up ultra-thin layers of plastics coated with green, red and blue dyes.

When an electric current passes through them, they combine to produce white light.

Previous attempts to make OLEDs like this have largely failed to make an impact because traditional phosphorescent blue dyes are very short lived.

The new polymer uses a fluorescent blue material instead which lasts much longer and uses less energy.

The researchers believe that eventually this material could be 100% efficient, meaning it could be capable of converting all of the electricity to light, without the heat loss associated with traditional bulbs.

The new material can also be printed onto glass or plastic and so in theory could create large areas of lighting, relatively cheaply.

Before this becomes a reality, the scientists need to work out a way to seal the OLEDs from moisture which can contaminate the sensitive material, causing it to no longer work.

If that barrier can be overcome, the new polymer could eventually become the material of choice for stylish, environmentally friendly lighting.

The research team incorporated members from Princeton University, the University of Southern California and the University of Michigan.

Chemists work on plastic promise
20 Mar 06 |  Science/Nature

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