permaculture

["Lawrence F. London, Jr." <lfl@intrex.net>]

<http://news.bbc.co.uk/1/hi/sci/tech/4906188.stm>
Last Updated: Thursday, 13 April 2006, 11:04 GMT 12:04 UK
E-mail this to a friend         Printable version
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

Light bulbs: Not a bright idea?
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.