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Nanocrystals could light the way to using LEDs to replace the lightbulb

2007-09-27 22:34:00

Thomas Edison's lightbulb has ruled the world's lighting for more than a century, but numerous researchers are trying to replace the incandescent bulb with more energy-efficient solid-state lighting. One problem has been producing bright white light. To address the problem, D.D. Sarma, a materials scientist at the Indian Institute of Science [profile], in Bangalore, has made tiny crystals of semiconductor material that, when coated onto a light-emitting diode (LED), give off a white glow just the right color for illuminating a living room. So far, it's only a weak light, but Sarma hopes to make it much brighter.

Sarma says that his approach gives better control over the whiteness and is simpler than other research efforts that use nanocrystals to produce white-light LEDs. Sarma grows tiny crystals of cadmium sulfide. He then paints them onto an LED that emits ultraviolet wavelengths, and the crystals produce the mix of colors that we perceive as white light. It's the extremely small size of the nanocrystals--each crystal is only five nanometers in diameter--that gives them their remarkable properties, says Sarma.

Single-color LEDs have largely taken over for lightbulbs in uses such as traffic signals. There's a big push to replace incandescent and fluorescent bulbs for general illumination as well. Sandia National Laboratory [profile] estimates that if half of all lighting is based on LEDs by 2025, the world would use 120 gigawatts less electricity, saving $100 billion a year and cutting the carbon-dioxide emissions from power plants by 350 megatons annually.

http://www.nanotechnology.com/news/?id=11469