New material could lead to cheaper, more eco-friendly LEDs
By Ben Coxworth
June 14, 2013
LED light bulbs may be more energy-efficient and longer-lived than their incandescent equivalents, but they’re also considerably more expensive to purchase. This is largely because rare earth elements (REEs) are used in their phosphors. There are hazards involved in the mining and processing of REEs, plus China is responsible for almost the entire world’s supply, so they’re becoming increasingly pricey. Now, however, scientists have come up with a plentiful alternative material that they say is much more environmentally friendly, and that should drive down the price of LEDs.
In regular LED bulbs, the REE-based phosphors are used to soften the LED’s existing blue-ish light. University of Washington spinoff company LumiSands has developed a material that reportedly does the same thing, but that also converts the light to a color temperature closer to that of natural sunlight. What's more, the material is made from cheap, abundant silicon.
The company produces the material by etching nanoparticles from a silicon wafer, then embedding them in an ultra-thin membrane. When subsequently exposed to an LED light source, the nanoparticles glow red. The combination of the LED’s own blue light and the red from the silicon results in a soft, warm sun-like light.
According to LumiSands co-founder and CEO Chang-Ching Tu, the whole process can be performed in a laboratory, and should be easy to scale up for commercial production.
The company is now looking into methods of getting the nanoparticles to fluoresce in additional colors such as yellow and green, for use in LEDs that emit a neutral white light. It is also in the process of seeking industrial partners, and hopes to begin production in no more than a year.
Source: University of Washington