Posted on 04/19/2006 10:57:35 AM PDT by Neville72
High efficiency flat light source could be the end for the light bulb
April 19, 2006 The end of the lightbulb is nigh! Scientists studying organic light-emitting devices (OLEDs) have made a critical leap from single-color displays to a highly efficient and long-lived natural light source. The invention is the latest fruit of a 13-year OLED research program led by Mark Thompson, professor of chemistry at USC and Stephen Forrest of the University of Michigan. If the device can be mass-manufactured cheaply - a realistic expectation, according to Thompson - interior lighting could look vastly different in the future. Almost any surface in a home, whether flat or curved, could become a light source: walls, curtains, ceilings, cabinets or tables. Since OLEDs are transparent when turned off, the devices could even be installed as windows or skylights to mimic the feel of natural light after dark - or to serve as the ultimate inconspicuous flat-panel television.
"This process will enable us to get 100 percent efficiency out of a single, broad spectrum light source," Thompson said.
Thompson and Forrest previously invented efficient single- color displays now ready to enter the market in next-generation cell phones. But subsequent attempts by several groups to create white-light OLEDs fell short. The biggest issue was the fast burnout time of the blue component, since blue is one of the primary colors needed to make white.
The Nature paper presents a quantum mechanical trick that solves this problem. First, the researchers followed their standard recipe for making an OLED: placing four ultra-thin organic layers on glass or transparent plastic. Three of the layers serve as highways for charges to reach a central "emissive" layer.
When the oppositely charged molecules meet in the emissive layer, electrons jump from the negatively charged molecules to the positive ones, and ultimately relax to their starting energy. In the process, light is emitted, which can be tuned to cover a broad range of wavelengths.
Previous OLEDs used phosphorescent blue, green and red dyes to generate light with greater energy efficiency than all-fluorescence based devices (phosphorescence and fluorescence, both expressions of energy that is released as excited electrons fall back into their regular orbit, differ mainly in the speed of their response).
Thompson and Forrest found that they could substitute a fluorescent dye for blue without sacrificing the superior properties of OLEDs.
In fact, the researchers reported, the fluorescent dye should prolong the lifetime of the blue component and also uses 20 percent less energy. "We're hoping this will lead to significantly longer device lifetimes in addition to higher efficiency," Thompson said.
According to Forrest, the device eventually could achieve three times the efficiency of standard incandescent light bulbs.
"With a future emphasis on manufacturing technology, this structure may provide an important, low-cost and efficient means that will replace incandescent lighting in many different applications," Forrest wrote.
The tallest remaining hurdle to production of these devices may have nothing to do with the OLED itself, Thompson said, but with the plastic layer to be used as a backing in economical large-area devices. All mass-produced plastics allow some humidity to pass through to the OLED, eventually degrading it.
"There's no plastic that's hermetic enough to make devices that will last a long period," Thompson said, while predicting that this problem can be solved. Already, Universal Display Corp. has developed the group's research into a commercially feasible process for making cell phone screens.
Funding for the research came from the Department of Energy and Universal Display Corp., which holds exclusive licensing rights to the group's OLED inventions.
WOW!!!!!!
> 100 percent efficiency
Errrrrr.....
Oooo, all the way up to match fluorescent.
I blame Bush...
Uh huh...
[...]
According to Forrest, the device eventually could achieve three times the efficiency of standard incandescent light bulbs.
There's a pretty big gap between those two statements. Further, they aren't even talking about a broad spectrum source, but rather a multi-frequency source that matches up to our optical pigments (though assuming no hidden side-effects, that's better for common usage).
yeah yeah...
Picky picky picky...
It might be better than fluorescent if it's flat instead of curved or bulbous or whatever. A not-insignificant portion of the light coming out of the standard bulb is going back into the fixture. In fluorescents, you undoubtedly lose some of that light that comes out of one side of the curly-cue and goes across the middle to the other side. I wonder if that's already part of their calculations -- "loss due to geometrically-related absorption and diffusion" or somesuch.
ping
The only real problem is the massive amount of neutrinos generated as the entire light fixture turns into pure radiant energy, but they plan to fix that too, as soon as they scrape the outlines of the R&D researchers off the wall of the test lab...
There has always been cool new stuff. This might be more of it.
If they can make this work, THINK of the cool nerd applications! Fridges with controls like the Enterprise! My mind boggles at the cool possibilities!!!!
100% efficient... the problem is that if there is a flaw in the factory and you get even a 101% efficient one....
it will get brighter and brighter and you wont be able to turn it off...AND THE WHOLE WORLD WILL BE LIT UP FOREVER!!!
I imagine that in context this means that all the energy supplied to the LED is emitted as visible light, lacking the large IR component of incadescent and ultraviolet bulbs.
Caught my eye, too.... Perhaps he didn't mean that in the fully technical sense of the term, but rather a more "squeeze as many photons out of the thing as we can" sort of way?
I expect that statement is probably a misquote by the journo- the engineer probably said something along the lines of "close to 100%", which is feasible with electical devices.
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