Researchers in Germany have created the first LED from organic materials that is more efficient than traditional lighting. A team from the University of Dresden report a power efficiency of 90 lm/W, with a potential maximum of 124 lm/W.
Standard LEDs made from inorganic materials have already found widespread application in screens and commercial lighting because of their high efficiency. In recent years, researchers have also started to develop a new wave of LEDs using organic materials such as polymers. As well as being eco-friendly to dispose of, these LEDs also have the advantage of generating photons across a range of colors resulting in white light. Now, a team of physicists has redesigned the internal structure of organic LEDs to produce significantly brighter white light.
One promising way of creating white light is to coat an LED with phosphor, which converts monochromatic light into red, green and blue light. The drawback until now has been a lack of efficiency; 80% of the photons generated remain trapped in the LED emission substrate and the surrounding phosphor. The research team overcame this problem by optimizing the coupling between these phosphor and polymer layers. By integrating blue, green and red phosphor into the heart of the emission layer, they have created a system that allows significantly more photons to escape.
Standard fluorescent tubes generate light with a power efficiency of 60–70 lm/W, but until now most organic LEDs had an efficiency of just 44 lm/W. The new device exhibits an efficiency of 90 lm/W.
View article on the Optics.org website.
Original paper: White organic light-emitting diodes with fluorescent tube efficiency, Nature 459, 234-238 (14 May 2009) | doi: 0.1038/nature08003
Dr. Gopal Rao
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Materials Research Society (MRS)