Making Light from a Grain of Sand

Anne L. Fischer

LED manufacturers have been working for years to replace the incandescent light. Among their many challenges is that LEDs dissipate a lot of heat, making them inappropriate for some applications. They also have found it difficult to produce white LEDs that are bright enough at a cost low enough to become a consumer product.

InnovaLight, a start-up in St. Paul, Minn., is using silicon quantum dots in its quest to replace the incandescent bulb with lighting that will last 100 years. The advantages to this nanotech approach, the company’s researchers say, include efficiency, stability, color range and low cost. There are no heat issues, and the white light generated is softer than that from LEDs, making it more appropriate for the warm illumination needed in interior environments.

The process of developing solid-state lighting based on luminescent silicon nanocrystals began in 2000 at the University of Texas at Austin. The light was created when bits of silicon were pressurized in a titanium chamber, exposed to solvents and heated to 932 °F. When the process resulted in a steady glow of light, venture capitalists climbed aboard to form InnovaLight.

Silicon nanocrystals in polymer hold promise for use in very bright sources of light. They should be able to avoid common problems such as reabsorption and scattering, and their small size allows for billions of molecular emitters per square inch. Courtesy of InnovaLight.

Silicon nanocrystals smaller than 4 nm emit light across the visible spectrum, but because the size of the nanocrystal determines the hue, it is possible to make light sources that produce any desired color by employing nanocrystals of the appropriate size.

The company concentrates on producing specific sizes of the silicon crystals and has a unique passivation process that stabilizes the particles so that they do not oxidize or react with other molecules. This is key to the work, said Conrad Burke, vice president of marketing and business development, because it ensures that the nanocrystals remain pure.

InnovaLight is developing flat-sheet light panels to be used in commercial light tiles, backlights for displays and keypads, and interior lighting for automobiles. Device samples are expected to be made available early next year.