Nanometre-sized light-emitting devices can be printed on thin sheets of material and applied to any surface
Charles Mandel
Sun
American researchers have seen the light — and it is good.
Working with organic light-emitting devices (OLEDs), scientists from California and Michigan have developed a white light that potentially can be incorporated into virtually any surface, is bright, and could last as long as two years.
OLEDs are nanometre-sized semiconductors that are printed on layers of organic materials — frequently carbon. They emit light through a process known as electrophosphoresence, which involves injecting electrons into the organic material and exciting the molecules into creating luminescence.
Because OLEDS are printed on thin layers of plastic, glass and metal hundreds of times thinner than a human hair, they have the potential to be used in large panels applied to any flat or curved surface, including walls, ceilings and tables.
But Stephen Forrest, vice-president of research for the University of Michigan, said at least initially people may prefer to see them in the shape of an old-fashioned light bulb.
“People like what they have, so why not just have a piece of plastic that you screw in, looks exactly like a light bulb, and you turn it on,” Forrest said in an interview Thursday.
Forrest and Mark Thompson, a professor of chemistry at the California-based USC College of Letters, Arts and Sciences, report on their invention this week in the journal Nature.
One of the biggest challenges with OLEDs to date has been the creation of a pure, strong, energy-efficient white light.
White light is formed from the correct ratio of phosphorescent red, green and blue. According to Ted Sargent, a University of Toronto professor who holds the Canada Research Chair in Nanotechnology, it’s easier to produce one of the colours than all of them. Scientists have previously tried to produce white light by first creating the blue light and then mixing it with the other colours. While that technique works, it is not efficient because creating the blue light adds an extra step to the process, and the blue light lacks longevity.
Instead, Forrest and Thompson manipulated a blue fluorescent dye to work in conjunction with red and green phosphorescent materials.
© The Vancouver Sun 2006