Logo: University of Southern California

CEN Reviews Two Years of Energy Nanoscience at USC and Prepares for Three More

The agenda: Improving organic solar cells, using nanorods for solar power and LED illumination

October 12, 2011 —

More than 70 scientists from 18 teams researching new ways to turn light into energy and energy into light recently gathered at USC to discuss achievements and decide directions.

CEN Leadership (left to right): Stephen Forrest (U. Michigan, co-PI), P. Daniel Dapkus (USC Viterbi, director), Mark Thompson (USC Dornsife, co-PI), Chongwu Zhou (USC Viterbi, co-PI), Jim Coleman (U. Illinois Champagne-Urbana, co-PI), Joe Campbell (U. Virginia co-PI).
The participants are affiliated with the USC Center for Energy Nanoscience (CEN), one of the Energy Frontiers Research Centers established by the US Department of Energy. CEN’s director is Professor P. Daniel Dapkus of the USC Viterbi School of Engineering Ming Hsieh Department of Electrical Engineering. CEN teams include faculty and students from USC Viterbi, the USC Dornsife College, the University of Michigan, the University of Virginia and the University of Illinois at Urbana-Champaign who gathered at USC for a daylong retreat.

CEN is a five-year program, wrapping up its second year.

Participants first heard detailed reports about what colleagues were doing, and then gathered to, as Dapkus said, “count our accomplishments, reassess our directions and focus on the next three years of research.”

Center researchers are exploring the use of two technologies to capture and conserve energy from the sun: cells using organic materials as opposed to silicon, and cells using nanorods or submicroscopic cylinders of various assembled materials. Both technologies are also being explored as potential light-emitting diode illumination devices.

There have been achievements in all areas, Dapkus said.

“Our organic solar team, led by Mark Thompson, has already demonstrated improvements in the efficiencies of these devices," Dapkus said. "In addition, very fundamental studies of the physical mechanisms by which the conversion of light to electricity takes place in these materials are underway that promise to improve the efficiency of the devices even further. This is very exciting because this technology promises to be very inexpensive and might allow us to employ solar cells more widely than is possible today."

Thompson, who is one of the founders of the USC effort and USC co-PI, reported that the CEN organic solar cell group researchers had created a promising new design, delivering higher power than previous similar devices.

“As we develop more understanding of the devices the efficiency goes up,” Thompson said. He and colleagues are making organic devices that use light from a wider portion of the solar spectrum, and believe they are making rapid progress.

The other design area is also proceeding well, Dapkus said.

"Nanorod–based solar devices promise very high efficiency — possibly two to three times higher than existing solar cells – at costs that are competitive," Dapkus said. "Our team led by Chongwu Zhou is working very hard to realize this potential and to provide a sound scientific underpinning for our accomplishments. I should also say that we have other ideas based on new nanostructures that may provide even lower cost solutions. In the lighting arena our nanorod device concepts may yield less expensive and more efficient LEDs that solve some vexing problems in this technology. It is an exciting time to be involved in this work."

The vision being pursued is a tandem design, which couples a gallium arsenide nanorod cell with a traditional silicon solar cell to create a design that uses otherwise wasted energy.

"We have produced a family of new materials we believe will give us high efficiency and low cost,” Zhou said.

Additionally, Michelle Povinelli of the Hsieh Department is creating optimized nanorod array configurations that can produce more energy using fewer nanorods.

The CEN Annual meeting will take place in January, again at USC. That meeting will involve all CEN members and its international board of scientific advisors.

“We’re happy to have our colleagues from other universities come out to USC to plan a mid-course correction, preparing for the review of our activities that will be coming next year,” Dapkus said.

Other USC faculty associated with CEN include Richard Brutchey, Barry Thompson and Steve Bradforth of the USC Dornsife Department of Chemistry; John O'Brien of the USC Viterbi Ming Hsieh Department of Electrical Engineering (EE); Steve Cronin with appointments in Chemistry and EE; Jia Grace Lu with appointments in the USC Dornsife Department of Physics and Astronomy and EE; and Priya Vashishta, Rajiv Kalia and Aiichiro Nakano with appointments in Physics and Astronomy and in the USC Viterbi School Mork Family Department of Chemical Engineering and Materials Science and its Department of Computer Science.

All together: the CEN team.