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  • Organic Light Makes the Call

Photonics Spectra
Aug 2001
Brent D. Johnson, Senior News Editor

Organic light-emitting technologies have been proposed for applications ranging from semiconductors to photovoltaics, but what's really driving the development of these technologies is their benefit to the flat panel display industry.

The Motorola Timeport P8767 uses organic electroluminescent display technology to achieve high brightness across a wide viewing angle.

Motorola Inc. has been using organic electroluminescent technology in cellular telephone displays made by Pioneer Corp. since the middle of last year. The first were the StarTac series of cellular phones, which are available with both liquid crystal and organic electroluminescent displays.

Steve Lalla, senior director at Motorola PCS, said the company wanted to introduce new colors on its Timeport P8767 phone's display. Pioneer easily did this by adding dopants to the electroluminescent material, producing red, green and blue.

He said the biggest enhancement provided by organic display technology is its readability. At 100 cd, the organic display yields 10 times the brightness of an equivalent liquid crystal display (LCD). "It is a very brilliant and dynamic display," Lalla said. "It's a very different experience from LCDs."

The clarity is also significantly better. The contrast ratio is 100:1 because the colors are superimposed on a black background. By comparison, the black lettering of LCDs against a background of gray/green produces only a 5:1 ratio. In addition, the viewing angle maintains visibility of the organic displays at 170°, whereas the much greater reflectance of LCDs causes lettering on the screen to disappear beyond 100°.

The only drawback to organic electroluminescent displays is that they draw slightly more power than LCDs do. However, Motorola has resolved this issue by integrating the new display in its "clam" form factor, otherwise known as a flip phone. This design opens and closes like a clam; the display shuts off when the phone is closed, conserving more power than devices that have external displays.

The company also is studying the use of the organic display in "candy bar" form factors that would require it to remain illuminated while the phone is on. Lalla said that the battery consumption needs to be managed but that one possible solution is to have the display dim when the phone is not in use.

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