This is an excerpt from EERE Network News, a weekly electronic newsletter.

July 30, 2003

Research Advances Show Promise for Solid-State Lighting

Separate research advances at DOE's Sandia National Laboratories and at GE Global Research are encouraging for two different approaches to making solid-state lights. Lights made from solid-state materials, including light-emitting diodes (LEDs), could potentially operate at much higher efficiency than incandescent or fluorescent lights, providing a new way to save energy. Already, LED traffic lights are saving energy for cities throughout the United States, but the true "holy grail" for solid-state lighting is a bright white light that can be used to illuminate homes and businesses.

Researchers at Sandia National Laboratories are using an innovative approach to solid-state lighting, building their lights from "quantum dots"-nanometer-sized dots of light-emitting material. The microscopic phosphors emit light without scattering it, so they are an efficient light source, and can be "tuned" to emit the right frequencies of light by changing their size and their surface chemistry. The trick, though, is encapsulating the dots without letting them clump together. Sandia researchers solved that problem by chemically attaching the dots along the long-chain molecule that forms the encapsulating plastic. In the center of the plastic is an LED that emits near-ultraviolet light; the surrounding quantum dots absorb that light and emit white light. The lights produced by the Sandia team convert 60 percent the energy supplied to them into light. See the Sandia National Laboratories press release.

Researchers at General Electric's research organization, GE Global Research, are taking a totally different approach to solid-state lighting, building their lights from organic LEDs, or OLEDs. OLEDs can be produced from thin sheets of plastic material that could be manufactured using inexpensive roll-to-roll technology, much like the the process used to print newspapers. The result would be a revolutionary paper-thin light that could be applied to walls or ceilings like wallpaper. The problem tackled by GE researchers—using funding from DOE—was the tendency for one short circuit to cause an entire sheet to stop emitting light. To make a more "fault tolerant" OLED, the researchers found a way to break up the surface of the sheet into smaller sections, so that a failure in one part of the device would not cause the whole sheet to go black. See the GE press release.

Meanwhile, a number of companies continue to develop traditional LEDs for use as lighting sources. For instance, Toshiba America Electronic Components, Inc. (TAEC) has added bluish green and reddish purple LEDs to its line of high-luminosity LEDs. And Lumileds Lighting, another maker of high-luminosity LEDs, has seen its products used in everything from car headlights to stage lighting. The company plans to produce a "warm" white light, mimicking the color of an incandescent bulb, beginning in August. See the press releases from TAEC and Lumileds.