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The holy grail of solid-state lighting, however, is a true white LED. Wetzel said the white LEDs commonly used in novelty lighting applications, such as key chains, auto headlights, and grocery freezers, are actually blue LEDs coated with yellow phosphorus — which adds a step to the manufacturing process and also results in a faux-white illumination with a noticeable bluish tint.

The key to true white LEDs, Wetzel said, is all about green.

“We have high-performance red LEDs, we have high-performance blue LEDs, and if we paired them with a high-performance green LED we would be able to produce every color visible to the human eye — ncluding true white,” he said. “Every computer monitor and television produces its picture by using red, blue, and green. That means developing a high-performance green LED would likely lead to a new generation of high-performance, energy-efficient display devices. The problem, however, is that green LEDs are much more difficult to create than I, or anyone else, imagined.”

Simple preliminary attempts to create green LEDs, by merely adding more indium (In) to the gallium nitride (GaN) materials that composed blue LEDs, were unsuccessful. The resulting green LEDs just weren’t strong or bright enough to stand toe-to-toe with red or blue. Wetzel and his research group have been working to tweak precisely how to add more indium, and how to grow the structure more carefully into a device, with the goal of boosting the strength and light output of green LEDs. They’re endeavoring, he said, to “close the green gap.”

Once they overcome the challenge of developing efficient green LEDs, he envisions LED technology will quickly evolve from its current applications in signs and small displays and grow into a universally adopted, globally used replacement for traditional light bulbs and compact fluorescence tubes. Wetzel said lights for general lighting applications, as well as the lighting of televisions, computer screens, and other electronics devices, will be cheaper, more energy efficient, and more reliable if we used LEDs.

“This is a new and exciting technology that holds immense promise, but the technological landscape is constantly in flux and we still have a ways to go before we are able to fully realize the energy and cost savings of LEDs,” Wetzel said. “But I know that people are interested in lighting their homes and powering their devices with LEDs because they’re always asking me, ‘so when can I buy one?’”

Wetzel has been working on this problem for several years, and in recent months received an additional $1.8 million in funding from the U.S. Department of Energy. He has also partnered with several companies, large and small, to join efforts and finally close the “green gap” once and for all.

For general information on Wetzel’s research, visit his bio.

Contact
Michael Mullaney
Rensselaer Polytechnic Institute
Troy, NY
518-276-6161 (office)
518-698-6336 (mobile)
mullam@rpi.edu

“Greenlighting A Greener World” Page 1 | 2 <
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