June 5, 2009 -- The next time your lamp needs a new light bulb, you might change the lamp shade instead of the light bulb. New research out of Germany and published in a recent issue of the journal Nature shows that cheap and thin organic light-emitting diodes (OLEDs) can create white light as bright as any compact fluorescent bulb for nearly half the electricity as many compact fluorescent light bulbs. "This uses cheap, well-known, and well-established materials," said Sebastian Reineke, a coauthor on the paper from the Institut fur Angewandte Photophysik. "First, we optimized the light that the white OLED emits, and then did some optical tricks to ensure that more of the light was emitted," instead of getting stuck inside the materials themselves. Related Content:
Reineke's 150-nanometer-thick OLED has five different layers. The two outermost layers, which are attached to an indium tin oxide anode and a highly reflective silver or aluminum cathode, transport electricity. The next two inner layers act as blocking layers, surrounding innermost white light-producing layer. White light isn't just a single color however. A beam of sunlight hitting a prism spreads out in all the colors of the rainbow, but it only takes three colors to create white light: blue, red and green. The innermost layer is subdivided into three different layers, one for red, one for blue, and one for green. When one watt of electricity is fed into these three layers it can produce up to 90 lumens of white light. So far this is the most efficient number reported, according to Reineke. Low-end compact fluorescent light bulbs (CFLs) can produce 50 lumens per watt. Typical incandescent light bulbs get 15 lumens per watt. Reineke's white OLEDs will keep electric bills down even more than CFLs. Once the technology has matured they should also cost substantially less than CFLs. "It's a cheap process," said Reineke. "Basically it's like producing newspapers, using large rolls of plastic." It will be three to five years before any color of OLED are available for commercial purchase, says Reineke. There are still major technical challenges to overcome. One of the biggest is that a 90 lumen per watt white OLED only lasts about two hours before the blue-emitting layer decays enough that it only produce half of its original brightness. Get More NewsMouse Cloned From Long-Frozen CellResearchers create a mouse from a long-frozen cell. Will the mammoth be next?'Bubble' Could Protect AstronautsScientists say a "bubble" around a Mars-bound spaceship could protect astronauts.Big Reduction of Snowmobiles in Yellowstone ProposedA new plan would cut snowmobile use by 40 percent in Yellowstone.Microbes: Fuel of the Future?A reddish South American microbe is literally breathing fuel, say scientists.DNA Links Remains to Steve FossetDNA tests on two bones found in California confirm they are those of Steve Fossett.Women Carry More Bacteria Than MenSome bacteria prefer women, suggests a new study. But why?Ancient 'Water Monster' Facing ExtinctionA foot-long salamander that was a key part of Aztec legend is threatened by extinction.Grand Canyon's Youth ConfirmedThe Grand Canyon is millions of years younger than previously thought, argue geologists.My Take: E-Voting Not User FriendlyOpinion: Electronic voting machines don't always capture the intent of voters.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.At 40, Brain and Body SlowThe part of the brain in charge of motion starts a gradual slide in middle age.Spiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates. |
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