A new form of light-emitting diodes (LEDs) is in the works that will still be more energy-efficient and last longer than incandescent bulbs, but will be cheaper to make. The founders of LumiSands, a spin-off from University of Washington’s (UW) Center for Commercialization (C4C), have discovered a way to use readily-available silicon, which comes from sand, instead of rare earth elements (REE) for their phosphors.
LumiSands etches nanoparticles from silicon wafers and embeds them in a super-thin membrane. The nanoparticles glow red when exposed to an LED light source. By combining the red light with the blue from the LEDs, a sun-like light is produced. LumiSands’ silicon nano particles do not emit light, but glow red when its particles are smaller than five nanometers. A wet-chemistry process reinforces the surface. When added to the LED bulbs, the hue of the light is warmer and softer.
Traditional incandescent bulbs create lighting that is most like sunlight and easiest on human eyes, but in an inefficient manner producing a lot of heat. Fluorescent bulbs are more efficient but contain mercury, a health and environmental hazard. LEDs are still the most efficient and environmentally friendly light bulbs.
Despite “rare” being part of the name, REEs are relatively abundant. However, they are difficult to mine and the process is bad for the environment. Plus, China controls 97 percent of the REE supply and has reduced export quotas resulting in rising prices. They are not found in dense deposits, so a lot of land must be excavated to get to them and this expels radioactive material into the air. Thus the ongoing search for REE phosphor alternatives and why using abundant silicon is more green.
The co-founders of LumiSands are Chang-Ching Tu, the CEO who received his doctorate in electrical engineering at the UW and completed postdoctoral research in materials science and engineering. and Ji Hao Hoo , a doctoral student in electrical engineering at University of Washington. Tu was looking for a resource to continue his research when he first contacted C4C. In May 2013, he entered into an agreement for negotiating a license for the technology with LumiSands for product development and marketing.
According to a UW article by Debbie Woo, Hoo said, “We are in the proof-of-concept stage. We are standardizing the silicon nanoparticles so that customers can swap their rare earth-based products with our silicon products.” Tu says the process can be performed in a laboratory and can be scaled up for commercial production easily enough. They continue to search from nanoparticles that will fluoresce as yellow and green for future use in LEDs with neutral white light.
LumiSands is looking for industrial partners with hopes of starting production within a year on their patent-pending silicon quantum dot phosphor (SiQD-phosphor) technology that is “a cost-effective, non-toxic, and eco-friendly option for REE-phosphors.” Tu says the technology has many other applications. Contact Tu and Hoo at firstname.lastname@example.org or 206-604-4394.