Junji Kido, a professor in the department of organic device engineering at Yamagata University, has been working on OLED developments for some 19 years and was the first to introduce a white OLED light in 1993. His research team has more recently demonstrated prototype OLED lighting that produced 5000 candelas per square meter with an efficiency of around 20 lumens per watt —four times better than a 100-watt incandescent bulb.
The prototype OLED lighting uses fluorescent-based material, which is less efficient than phosphorescent OLED compounds, allowing great room for improvement. “We are now introducing phosphorescent [materials] and can bring up the lumen efficiency to 40 or 50 lm/W very easily,” says Kido.
Such is their progress that Kido says the university is forming a joint venture “with four or five companies” and plans to launch OLED lighting products in 2008.
Elsewhere, in June 2006 Konica Minolta announced the development of a white OLED light panel with an industry-record power-efficiency of 64 lm/W at 1000 cd/m2—four times as efficient as incandescent bulbs. This was achieved following KM’s earlier development of a blue phosphorescent OLED material with a decent lifetime—the missing ingredient needed for combining with red and green OLED phosphors to create efficient white light suitable for commercialization.
“Until we developed this blue phosphorescent material, there was no such material with a good lifetime,” says Tawara Komamura, general manager of R&D display technology at the Konica Minolta Technology Center, the research arm of KM. Whereas red and green phosphor OLED materials have been available, notably from Universal Display Corp., based in Ewing, N.J., “blue phosphor was a challenge to develop, just as it was with LEDs,” says Komamura.
Since then, KM has pushed the lumen efficiency up to 70 and extended the lifetime of the material to beyond 10 000 hours. GE has also been making progress in the lab, and the two companies say that by combining their resources they can bring OLED lighting to the market by 2010.
However, competitor Kido, donning his professorial hat, says the KM–GE announcement raises a number of questions. “The luminance required for general lighting is between 3000 to 5000 cd/m2,” says Kido. “So improvement is still needed in Konica Minolta’s 1000 cd/m2 [system], though it may be good for displays.” Usually, he points out, the luminance efficiency decreases when the brightness goes up.
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