When electrons are excited by sunlight, they move. But inside a solar cell, their journey isn't easy. Solar cells are made of layers of different materials, each with a specific purpose. To become part of the electric current that a cell produces, the excited electrons must cross from one layer to the next. Many of the electrons zip across the interface, where the two materials meet, but some stumble. That misstep takes a toll on the efficiency of solar cells and other devices. Efforts to ease crossings were stymied by researchers' inability to track the ultrafast electrons.
Enter William Tisdale.
He began working with laser spectroscopy techniques, but the information he was looking for was buried beneath a mountain of noise he didn't want to see. These techniques probe everything, but he only wanted to see the surface. He began devising new ways to image the interface.
"I read a lot of papers from the biological imaging community and realized that some of their technical advances could be applied to energy issues," says Tisdale. His innovative laser microscopy technique focuses just on the interface, where two materials, such as the layers of a solar cell, meet.
The technique examines electrons' motions by probing the electric fields that form when the charges zip across the surface. Tisdale is using the data to design easy-to-produce materials. "We want to make discoveries that'll lower the cost of solar cells and high-efficiency lighting," he says, "either through reduced manufacturing costs or dramatically increased efficiency."
One day, his work may lead to movies of electrons crossing interfaces.
His work has earned him the Presidential Early Career Award for Scientists and Engineers. This award is the highest honor given by the U.S. government to researchers early in their careers. He was nominated for the award by the Office of Basic Energy Sciences at DOE's Office of Science.
Tisdale earned a Bachelor's of Chemical Engineering from the University of Delaware and a Ph.D. in the same field from the University of Minnesota. He accepted a postdoctoral position at the Massachusetts Institute of Technology (MIT) and then a faculty position. Now an associate professor, he describes MIT as having incredibly talented students and a collaborative environment. His honors to date include the Alfred P. Sloan Fellowship and a DOE Office of Science Early Career Research Award.
Tisdale received the PECASE award in a DOE ceremony on May 4.
The Office of Science is the single largest supporter of basic energy research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information please visit http://science.energy.gov.
Kristin Manke is a Communications Specialist at Pacific Northwest National Laboratory on detail to the U.S. Department of Energy's Office of Science, firstname.lastname@example.org.