A Vision of Superefficient Displays

Organic light-emitting diodes invented by Eastman Kodak's Ching Tang are already transforming screen technology. Coming soon: Lightpaper?

For years before he made his great discovery, Ching Tang worked in the dark. After graduating from Cornell University in 1975 with a PhD in physical chemistry, Tang joined Eastman Kodak (EK ) as a researcher. He spent his days huddled in the darkroom, trying to concoct an organic material that would convert light into electricity -- basic research the company hoped would lead to a product. It was the start of a career at Kodak that has lasted 28 years, during which Tang has helped jump-start the organic solar-cell industry and also create a new type of energy-efficient display technology -- called organic light-emitting diode (OLED) -- that's now used in cell phones and digital cameras, and that could even end up in TVs one day.

By the 1980s, materials researchers around the world had tried and failed for decades to create a single-layer organic material that would conduct electricity -- and thus make it possible to use sunlight as an alternative energy source. In an effort to find a breakthrough, Tang decided to combine two organic compounds like layers in a cake. One day in 1985, he passed a charge of several volts through his latest sample and was about to leave the darkroom, when he noticed that the material glowed green -- even though it was no longer being charged. Within days, Tang could also make it glow blue, a hue not previously seen in organic compounds. "When you see the [blue] light, it almost feels like the genesis," Tang says, referring to the moment of creation.

The discovery sent Tang on a search through the archives of materials science, where he discovered that in the 1960s researchers had made organic crystals luminescent by hitting them with hundreds of thousands of volts. By contrast, Tang's ultrathin film glowed when charged with only a few volts. The key to making that happen was the film's thinness and the type of the material he used.


  "They didn't give me a promotion right away," he jokes of his bosses at Kodak, which holds the basic patents on the technology. But the execs allowed Tang to spend the next seven years figuring out how to make his samples glow different colors and last for hours, instead of minutes, before decomposing. Tang's discoveries were the basis for the first OLED display, which in 1999 showed up in car radios built by Japan's Pioneer Electronics.

Just four years later, improved versions of OLED technology are poised to claim a share of the nearly $60 billion market for CRT (cathode-ray tube) and LCD (liquid-crystal display) screens. Unlike their predecessors, OLED screens glow on their own when a small current is passed through them, so they don't need a back or side light. As a result, the latest OLED prototypes that display text require as little as 30% of the power needed to light an LCD screen -- a major plus with handheld devices that use batteries.

OLEDs also are sturdier than LCDs. And within two to five years, when manufactured in high volumes, they should be cheaper to make, says Kim Allen, director of technology and strategic research at display consultancy iSuppli/Stanford Resources, based in San Jose, Calif.


  This technology is already used in cell phones, digital cameras, and holiday lights. Since 1999, Pioneer has shipped more than 7 million OLED screens for radios and cell phones made by the likes of No. 2 mobile phone maker Motorola (MOT ).

And that's just the beginning. The worldwide market for OLED displays, valued at $91 million in 2002, could rise to $1.2 billion by 2006 as new materials come to market, according to the latest iSuppli/Standford Resources forecast. All this "great technical innovation and unlimited potential of OLED was introduced in the world thanks to Dr. Tang," says Teruo Tohma, director for OLEDs at Tohoku Pioneer, a subsidiary of Pioneer Electronics.

OLEDs have also changed Tang's life since he emigrated in the 1960s from his family's rice and chicken farm in a poor village on Hong Kong's outskirts. He studied chemistry at Canada's University of British Columbia, where he did well enough to earn a subsequent scholarship from Cornell. At 55, Tang now directs a 100-member Kodak staff that continues to research OLEDs. "When I started, I didn't believe this would get to this point," says Tang, who now bears the title Distinguished Inventor at Kodak.


  Indeed, the potential uses for OLEDs may be far more numerous than Tang imagined. General Electric (GE ) is investigating the possibility of using them for energy-efficient lighting. In fact, the technology is one of GE's six flagship research projects, says Anil Duggal, advanced technology leader at the company.

GE figures that if OLEDs could replace incandescent and fluorescent lamps, that could save 10% of the energy that will be used in the U.S. by 2020, cutting electricity costs by then by $20 billion annually. Duggal envisions OLEDs that could eventually be as thin and pliable as wallpaper -- and be applied directly to walls or ceilings to light buildings.

Indeed, Princeton University researchers have developed prototypes of flexible OLED displays that can be rolled up and stored in a tube. They're now working on ways to manufacture displays using a process similar to printing, says Stephen Forrest, a professor of electrical engineering at Princeton. The new manufacturing process could be adapted commercially in as little as two years, cutting the cost of making OLEDs to a fraction of what it is now. "It pleases me that so much work is going on relating to a simple discovery 20 years ago," says Tang.


  His focus now is on improving OLED materials to make the technology more reliable -- and thus useful for devices such as TVs. Today, an OLED screen has a lifespan of about 10,000 hours, or about 3.4 years of daily, eight-hour use. Tang is trying to develop substances that would increase that to 50,000 hours, or about 16 years of eight-hours-a-day use. He's up to as many as six layers of materials, vs. his original two, in a sandwich that is less than 0.1 micron thick. An untrained human eye can't see particles of less than 40 microns.

Within 10 years, Tang predicts, more-advanced OLEDs could become one of the dominant display technologies in handheld devices and TVs. Analysts say he could be right, though such widespread use might have its drawbacks for Tang himself. He carries a cell phone with an OLED screen, and every time he looks at it, "I see the molecules inside," he says. But he also perceives the bright side: "It's fun to be able to carry something that you know so much about." Soon, Tang might see molecules everywhere.

By Olga Kharif in Portland, Ore.

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