Nanoparticles Promise to Make LEDs Cheaper

A silicon-based nanoparticle aims at replacing the rare-earth-element phosphors used in LEDs

2 min read
Nanoparticles Promise to Make LEDs Cheaper

Light-emitting diode (LED) light sources have a lot going for them. They have longer life spans than their incandescent rivals and better luminous efficiency, and they’re environmentally friendlier. But those benefits come at a high cost—literally.

There are a number of points in the production of LEDs worthy of attack, such as the bases on which they're grown. Another involves scarce rare-earth metals, a problem endemic to high-tech manufacturing. Now researchers at the University of Washington (UW) have come up with a nanoparticle that could replace the rare-earth-element phosphors currently used in LEDs to soften the harsh blue light they emit.

Chang-Ching Tu, a post-doctoral researcher at UW, has launched a new company, LumiSands, to market the nanoparticles. The technique for producing them involves etching off the material from wafers of silicon. While silicon does not typically emit light, when it is in crystalline form at dimensions below five nanometers it can begin to glow.

The silicon-based nanoparticles emit a red light that, when combined with part of the harsh blue light of the LEDs, produces greens, yellows, and reds that resemble sunlight.

“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 in a UW press release. “The manufacturing process can be performed in a basic laboratory setting and is easy to scale up.”

The technology, though still evolving, is far enough along to launch a company, a prototype of the devices has been made, and Tu believes LumiSands could start manufacturing devices based on the technology within a year. He will continue to work on the red-light-emitting technology and then move on to other colors so that LEDs equipped with them will give off a white light with no rare-earth elements.

Image: Mary Levin, UW

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The Ultimate Transistor Timeline

The transistor’s amazing evolution from point contacts to quantum tunnels

1 min read
A chart showing the timeline of when a transistor was invented and when it was commercialized.
LightGreen

Even as the initial sales receipts for the first transistors to hit the market were being tallied up in 1948, the next generation of transistors had already been invented (see “The First Transistor and How it Worked.”) Since then, engineers have reinvented the transistor over and over again, raiding condensed-matter physics for anything that might offer even the possibility of turning a small signal into a larger one.

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