Sandia joins revolution in solid-state lighting

Sandia researchers are working on a project that will establish the fundamental science and technology base to replace incandescent bulbs and fluorescent tubes with semiconductor light-emitting diodes.

Sandia National Laboratories researchers are working on a project that will establish the fundamental science and technology base to replace America’s primary lighting source – incandescent bulbs and fluorescent tubes – with semiconductor light-emitting diodes (LEDs).

‘Just as for electronics, glass bulbs and vacuum tubes are giving way to semiconductors,’ said Sandia Senior Scientist James Gee, who heads up the project with Jerry Simmons and Bob Biefeld. ‘And as in the microelectronics revolution, many of the possible applications for solid-state lighting will occur in ways that have not yet been envisioned.’

LEDs are already found in devices that require durability, compactness, and cool operation. In some applications they also enable significant cost savings due to their lower consumption of energy: LED-based red traffic lights, for example, consume one-tenth the energy of their incandescent counterparts.

Lighting is presently responsible for roughly 20 percent of electricity consumption. Researchers believe that the development and adoption of solid state lighting technology could reduce America’s electrical consumption by 10 percent.

General Electric first demonstrated LEDs in 1962 and the first products were introduced in 1968. However, LEDs were reportedly limited to small-signal applications until 1985 when LED power was increased, resulting in new applications. In 1993 researchers at several universities in the US and Japan developed a fairly efficient blue light LED based on gallium nitride. Efficiency improvements followed quickly.

Today, energy-efficient LEDs are available from red to green to blue light, making it possible to generate white light for illumination.

However, Gee said, LED-based light sources are expensive – more than two orders of magnitude more expensive than commercial incandescent light bulbs – and will not be practical until their costs are reduced and efficiency is further increased.

As part of the LEDs project, some 25 Sandia researchers are exploring ways to make LEDs more efficient and less costly.

Challenges to Sandia researchers include developing an improved understanding of the physics of the gallium nitride-based materials that are the base materials of the LEDs and improving optoelectronic devices and materials for abundant photon generation and high light extraction efficiency.

Another challenge is to improve wavelength conversion and colour mixing technologies for generation of white light and improve packaging technologies for high-power LEDs.

‘This new white light source could change the way we live, and the way we consume energy,’ said Simmons, who manages the project. ‘LEDs could be 10 times more efficient than incandescent bulbs and two times more efficient than fluorescents. Clearly, LEDs’ replacement of conventional light sources would significantly reduce worldwide energy consumption.’