Chemists at Vanderbilt University in the US claim to have used quantum dots to create an LED that emits a warm white light, an improvement from the colder blue-white LEDS in production today.
The accidental discovery could have a big impact on the use of white LEDs, making them more suitable for home lighting, potentially replacing incandescent bulbs and fluorescent lamps.
Quantum dots made from nanoscale sized crystals can be made to produce different coloured light depending on their size. At Vanderbilt, the chemists found just the right size dot to produce broad spectrum white light.
Graduate student Michael Bowers made crystals containing cadmium and selenium, each with just 33 or 34 pairs of atoms. Illuminating the dots with a laser, he found they gave off a warm white light.
"I was surprised when a white glow covered the table," said Bowers. "I expected the quantum dots to emit blue light, but instead they gave off a beautiful white glow."
Other groups are researching or developing quantum dot LEDs. UK firm Nanoco has already started mass production of quantum dots with a range of excitation frequencies.
US firm Evident is working on mixing a number of dots, each with a different emission to make white light.
And in 2003, researchers at Sandia Labs made white and blue devices using quantum dots. Like Evident, each dot has a specific emission frequency.
However, the Vanderbilt dots seem to emit across a broad spectrum, without mixing different sized dots. The team also said they can make the dots quickly - in under an hour, which is much faster than other methods.
A report on the white LED appears online in the Journal of the American Chemical Society.
See also: Electronics Weekly's roundup of content related to LEDs, both white LEDs and coloured LEDs.