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Optoelectronics/Displays??

Silicon-based nanoparticles to produce greener, cheaper LEDs

Posted: 17 Jun 2013 ?? ?Print Version ?Bookmark and Share

Keywords:LEDs? silicon nanoparticles? LumiSands? LED manufacturing? rare-earth elements?

That's where LumiSands comes in. The company uses silicon, derived from sand, instead of rare-earth elements to convert part of the blue light emitted by LEDs into greens, yellows and reds. The resulting light looks more like sunlight.

The Tu and Hoo plan to sell directly to LED-bulb manufacturers that are looking to transition away from increasingly more expensive materials to make the lights.

"Hopefully, manufacturers could substitute traditional rare-earth elements with our material with minimal additional steps," said Hoo, a UW doctoral student in electrical engineering and co-founder of LumiSands. "It will be cheaper, better-quality lighting for users."

Incandescent bulbs give off light that's most similar to sunlightand easiest on our eyesbut the bulbs are inefficient and produce a lot of heat. Fluorescent bulbs, seen most commonly as long tubes in overhead office light fixtures, are more efficient than incandescent lights, but they contain mercury, posing health and environmental concerns.

LumiSands etches off nano-sized particles from wafers of silicon. The element, which usually doesn't emit light, can start to glow when its crystalline particle size is smaller than 5nm. The surface is reinforced through a wet-chemistry process. When the red-emitting silicon nanoparticles are added to LED bulbs, the light becomes softer and warmer in hue.

Silicon nanoparticles

The researchers use a black light to show the photo-luminescence of their silicon nanoparticles.

"The beauty of our technology is to create a highly efficient fluorescent material by using silicon rather than rare-earth elements or other types of heavy-metal compound semiconductors," Tu said. "The manufacturing process can be performed in a basic laboratory setting and is easy to scale up."

LumiSands plans to tweak the red technology before moving on to other colours such as yellow and green, which will enable LEDs to cast a white light with no rare-earth elements.

The company has received funding from the National Science Foundation, the Washington Research Foundation and the W Fund. It received an honourable mention in the 2012 Foster School of Business Environmental Innovation Challenge and a top award in the 2012 Jones Milestones/Foster Accelerator mentorship program.

Now, LumiSands is finishing a prototype of the technology and sending samples to lighting industry partners for evaluation. It will apply for competitive phase two NSF funding, which could launch the company toward manufacturing its technology within a year.


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