It’s a sunny day on the campus of the University of California, Santa Barbara, but little light penetrates the labs and offices of Shuji Nakamura. Shades sheathe the windows in part because, Nakamura says, “I worry about unknown people around here-that they will include a spy.”That sounds farfetched until you consider that Nakamura, who played a lead role in the development of blue light-emitting materials, is now back for a second act. In the 1990s Nakamura gained fame by cooking up the first semiconductor materials to emit bright blue light-a boon for displays and data storage-and sparked a global race to perfect the materials. He made those trailblazing lasers and their glowing cousins, light-emitting diodes (LEDs), at Tokushima, Japan-based Nichia-and became a sort of national folk hero in the process. (When Nakamura is in Tokyo, subway riders accost him for his autograph.)
Now, having moved to an academic post in the United States, he is at it again-caught up in an intense worldwide competition. That’s because the bright blue emitting devices that are the progeny of his original inventions provide a key stepping stone in a high-stakes effort to produce white-light LEDs that are sufficiently cheap, pleasing, and efficient to crush Edison’s almighty light bulb-and radically transform the
$40 billion general-illumination industry.
Briskly crossing a courtyard, Nakamura enters a semiconductor test room, and grad student John Kaeding hands him a plastic container bearing a translucent Oreo-size disc. Nakamura sits on a stool and touches a test electrode to a spot near the disc’s center. The disc is made of sapphire and coated with at least 30 invisibly thin layers of materials whose fundamental workings are not fully understood but whose properties astonish. Instantly, a bluish-green glow emanates. Nakamura lifts the electrode and touches a spot closer to the disc’s edge; it shines a grassy green. A third spot is dimly aquamarine; a fourth, violet; a fifth, bright blue-the color needed to create a solid-state device that produces white light.
Nakamura appears pleased, yet bright as this blue is, he knows immediately that it’s not bright enough. That’s why his grad students spend balmy California nights slaving over the 1,000 C ovens in which these materials are grown, tweaking chemistries and temperatures, changing substrates, altering flow rates of gases. “We try, try, try,” Nakamura says. A breakthrough, he adds, “could come in three years; could come today or tomorrow.” But let there be no mistaking his goal: “I want to replace all the conventional lighting.”
He’s not the only one. Dozens of companies and academic groups like Nakamura’s Solid State Lighting and Displays Center are feverishly seeking to produce a new kind of lighting by developing bright white LEDs (see “Lighting the Way,” table, last page). Indeed, just as transistors replaced vacuum tubes, LEDs promise to replace today’s glass-encased incandescent and fluorescent light bulbs: LED lights use far less electricity than an average light bulb, and they shine for a far longer time before burning out.
Most researchers are, like Nakamura, pursuing LEDs made of such semiconducting materials as gallium nitride; a few other groups are developing more exotic organic light-emitting diodes (OLEDs), which are like plastic sheeting and herald the day when softly glowing patches of material replace ceiling fixtures and luminescent curtains brighten living rooms. Entrants in these races include lighting giants such as General Electric and Osram Opto Semiconductors, along with electronics companies such as Philips and Agilent Technologies, whose joint venture, Lumileds Lighting in San Jose, CA, makes one of the world’s highest-power white LEDs.
The first results are already visible. Early white LEDs are widely sold in flashlights and head-mounted hiking lamps. Visitors to the Jefferson Memorial in Washington, DC, see a rotunda bathed in white LED light. As costs fall, efficiency rises, and the quality of the light improves, white LEDs should bust out of these niche applications and displace billions of conventional light fixtures in factories, offices, and homes. “It’s not going to just change the light bulb; it will change the lighting paradigm,” says Arpad Bergh, president of the Optoelectronics Industry Development Association, a Washington, DC-based industry group.
The new lighting technology would also dramatically cut electricity demand. According to a study commissioned by the U.S. Department of Energy, widespread adoption of next-generation white LEDs for lighting could, by 2025, slash electricity consumption by 10 percent worldwide, cutting $100 billion per year from electric bills and saving $50 billion in averted power-plant construction costs. “Lighting is a major contributor to the use of electricity. Collectively we could save half the energy we use on lighting,” says George Craford, chief technology officer at Lumileds. “Make lighting more efficient and the question of building new power plants starts to go away.”