Expectations Dim for OLED Lighting

High costs could keep white organic-light-emitting diodes off the shelf

Photo: Philips

Warm White: Analysts and the industry are putting out mixed signals on how hot the market for OLED lighting will be.

A new report suggests that organic light-emitting diodes, or OLEDs, won't come anywhere close to replacing conventional illuminators like incandescent and compact fluorescent lightbulbs in the foreseeable future. The analysis, conducted by Lux Research, a technology consultancy based in Boston, is marked by an extremely bleak projection of the worldwide OLED lighting market in 2020—a mere US $58 million in annual sales.

But experts from industry and academia and even other independent analysts aren't nearly so pessimistic, with one annual sales projection in the billions of dollars. Which future for OLED lighting comes to pass will depend on how much technology developed for OLED displays proves transferable to the lighting world.

Like conventional, inorganic LEDs, an OLED is an assembly of semiconductors sandwiched between two electrodes. Voltage at the positive electrode yanks resident electrons out of the inner semiconductor layers, leaving vacancies, or holes, while the negative electrode pushes new electrons in. When electrons meet holes, photons are emitted.

But OLEDs have carbon-based semiconductors, and when it comes to producing white light, the organic and inorganic varieties do it differently. Ordinary white LEDs are actually blue diodes shining through a yellow phosphor. OLEDs create white by combining red, green, and blue semiconductor films—either stacked on top of each other or laid down in thin, alternating stripes.

Proponents of OLEDs tout the quality of light they produce and the fact that they can be molded into any shape, two characteristics that also distinguish them from LEDs. OLEDs could also, in theory, save more than 90 percent of the energy that's currently used to power incandescents and consume less than half the electricity needed by compact fluorescents. Because of this potential, the U.S. Department of Energy has invested about $40 million in OLED lighting research.

But right now, because OLEDs are still a new technology, they're less efficient than compact fluorescent bulbs, and they're incredibly expensive: An OLED panel that produces slightly less light than a one-dollar 75-watt incandescent bulb costs $2560.

Jonathan Melnick, an analyst at Lux and the author of the damning report, claims that OLED lights will remain expensive and therefore obscure. "It's hard to see people adopting such an expensive lighting source without a compelling reason to do so," Melnick says. According to his report, the small future OLED market will be limited to designer applications—chic-looking lamps in swanky bars and upscale hotels—that take advantage of OLEDs' flexibility.

But others see a brighter future for the technology.

"The progress in OLED lighting has been spectacular in the recent past, and I don't see why it won't continue," says Stephen Forrest, a materials scientist at the University of Michigan who has made fundamental OLED developments. And a projection by NanoMarkets, a market research firm, pegs OLED lighting sales at more than $10 billion in 2018, over 100 times as much as the Lux estimate.

The difference in outlook arises from different perceptions about the relationship between OLEDs used for lighting and OLEDs used for displays—a fledgling technology that brought in over $700 million in sales in 2009. OLED displays can be made extremely thin and flexible and have better contrast than LCDs.

If the market for OLED displays really takes off, it will help drive down the cost of OLED lights, because the techniques used to fabricate displays and lights are "very similar," according to Janice Mahon, vice president of technology commercialization at Universal Display Corp., an OLED development company in Ewing, N.J. But Lux's Melnick says the similarities are limited: "The principles of technology are the same, but there isn't a huge materials overlap."

The truth lies somewhere in between, according to Lisa Pattison, an analyst at Solid State Lighting Services, which advises the Department of Energy. Because they require individually controllable pixels, "displays are more complicated to manufacture," she says.

When displays are fabricated—today on 1.3- by 1.5-meter sheets of glass, processed one at a time—pixels are created by stenciling red, green, and blue OLEDs onto a backplane of circuitry. OLED light panels don't require the backplane, and the color patterning—stacks or stripes—is much simpler.

But lights have more stringent performance requirements than displays. Lights spend more time powered on than the screens of televisions, computers, and mobile devices, so they'll have to deliver on their promise of high efficiency and have a longer life span. (Today, an OLED panel lasts about 8000 hours, compared to 1000 for cheap incandescents, 12 000 for compact fluorescents, and 25 000 to 50 000 for LEDs.)

In spite of these differences, Pattison agrees with Universal Display's Mahon. "There are enough similarities that advances in one can help the other," Pattison says. For one, developments in solution printing, where the semiconductors are printed onto the electrode with an inkjet printer, would benefit both. Printing could lower manufacturing costs by allowing lights to be produced cheaply on rolls of plastic or larger sheets of glass.

"There's a lot of potential for cost to go down and performance to go up," Pattison says. "OLEDs will be a part of the lighting future."

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