Energy Efficiency

Published on February 23rd, 2013 | by James Ayre


LEDs Without Heavy Metals, Silicon Nanocrystal Multicolor LEDs Created

February 23rd, 2013 by  

LEDs that are completely free of heavy metals have been successfully created by researchers at the Karlsruhe Institute of Technology and the University of Toronto. The highly efficient and heavy-metal-free LEDs were made by utilizing silicon nanocrystals that are only a few nanometers across. The silicon-based light-emitting diodes (SiLEDs) should eventually be able to take the place of any currently used LEDs, but without having the same environmental impact and at far cheaper costs.


It’s been common knowledge, for awhile now, that regular silicon is unsuitable for LEDs, but on the nanoscale this isn’t true. Tiny silicon nanocrystals are very capable of producing light, and have great potential thanks to their high efficiency. And now, researchers have successfully made use of some of that potential, manufacturing highly efficient LEDs from silicon nanocrystals consisting of only a few hundred to thousand atoms.

As of now, the manufacture of SiLEDs is “limited to the red visible spectral range and the near infrared,” the Karlsruhe Institute of Technology writes in a press release — the institute is already #1 in the world for the efficiency of silicon diodes emitting red light. “Controlled manufacture of diodes emitting multicolor light, however, is an absolutely novelty,” however, says Florian Maier-Flaig, scientist of the Light Technology Institute (LTI) of KIT and doctoral student of the Karlsruhe School of Optics and Photonics (KSOP). The color adjustments are made by separating the nanoparticles by size. “Moreover, our light-emitting diodes have a surprising long-term stability that has not been reached before.” The reason for the increased lifespan is because of the use of only one nanoparticle size per LED, which improves the stability.

“With the liquid-processed silicon LEDs that may potentially be produced on large areas as well as at low costs, the nanoparticle community enters new territory, the associated potentials of which can hardly be estimated today. But presumably, textbooks about semiconductor components have to be rewritten,” says Geoffrey A. Ozin, who is presently working as a KIT distinguished research fellow at KIT’s Center for Functional Nanostructures (CFN).

One of the most significant advantages of these new SiLEDs, though, is that they do not contain heavy metals, and rely only on cheap, highly abundant materials.

The new technology will be explained in detail in the journal Nano Letters.

Image Credit: F. Maier-Flaig, KIT/LTI

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

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