NSF award aids UNL engineer's efforts to build better solar cell
Released on 12/19/2012, at 2:00 AM
Office of University Communications
University of Nebraska–Lincoln
The sun provides all the energy humans could ever need. But capturing that power remains expensive and inefficient, which leaves fossil fuels as dominant energy sources.
Jinsong Huang, an assistant professor of mechanical and materials engineering at the University of Nebraska-Lincoln, envisions a future when solar energy devices will become so inexpensive and pliable that nearly any surface, including windows and clothing, will harness the sun. He recently earned a five-year, $400,000 Faculty Early Career Development Program, or CAREER Award, from the National Science Foundation to continue his research into solar cell development. This prestigious award helps outstanding pre-tenure faculty develop as teacher-scholars and researchers.
"Solar is one of the most renewable and convenient energies," Huang said. "People really want to convert solar energy into electricity, but it's too expensive now compared to fossil or nuclear energy. So we want to make solar competitive with other types of energy."
Today's solar cells use a semiconductor, almost exclusively silicon, sandwiched between two metal electrodes that create an electric field. One electrode is transparent to allow light to pass. The photons in sunlight knock loose the semiconductor's negatively charged electrons, which migrate within the system's electric field to form a current. That current is harnessed as electricity. Although silicon-based solar cells are efficient, they are expensive to produce and limited in their applications, Huang said.
To overcome silicon's limitations, scientists are working to replace it with organic polymers, or plastics, which are cheaper and more flexible, but also less energy efficient.
Huang and his colleagues are working to improve organic polymers' efficiency as a semiconductor. They discovered that placing a layer of ultrathin ferroelectric polymer between each electrode and the organic polymer increases the device's energy efficiency.
Ferroelectric polymers are inexpensive materials that hold large permanent electrical polarizations on each side. This increases a solar cell's internal electric field and, in turn, generates more electrical current.
One of the biggest challenges for polymer solar cells is to make them as efficient as silicon solar cells.
"In order to make the plastic solar cell commercially available to compete with silicon solar cells, we need to get the energy conversion efficiency up to 15 or 20 percent," Huang said. "We are almost halfway to that." With the CAREER Award, Huang will continue perfecting organic polymer solar cells using ferroelectric material to increase efficiency.
Organic polymer solar cells are much less expensive to produce than silicon-based cells because of cheaper material and fabrication costs. Used in spray paints and inkjets, organic polymers may allow solar cells to be made as quickly and easily as printing off the daily newspaper, Huang said.
The material's pliability also promises to lead to many new applications. Instead of large, expensive solar panels atop buildings and poles, future solar cells may be easily and inconspicuously incorporated into clothing, laptop bags and tents or even added to existing buildings by simply pasting them onto windows.
This award also supports Huang's outreach activities. He is preparing an educational workshop to teach Nebraska's high school students about solar engineering and to encourage them to consider engineering careers. He is also helping produce demonstrations about solar energy and engineering at the University of Nebraska State Museum.
Writer: Gillian Klucas