Team improves solar-cell efficiency

Sep 19, 2014  Original post:  http://phys.org/news/2014-09-team-solar-cell-efficiency.html

This polymer solar cell consists of a new polymer, called PID2, which was developed in the laboratory of Luping Yu, professor in chemistry at the University of Chicago. The new polymer improves the efficiency of electrical power generation by …more

New light has been shed on solar power generation using devices made with polymers, thanks to a collaboration between scientists in the University of Chicago's chemistry department, the Institute for Molecular Engineering, and Argonne National Laboratory.

Researchers identified a new polymer—a type of large molecule that forms plastics and other familiar materials—which improved the efficiency of solar cells. The group also determined the method by which the polymer improved the cells' efficiency. The polymer allowed electrical charges to move more easily throughout the cell, boosting the production of electricity—a mechanism never before demonstrated in such devices.

"Polymer solar cells have great potential to provide low-cost, lightweight and flexible electronic devices to harvest solar energy," said Luyao Lu, graduate student in chemistry and lead author of a paper describing the result, published online last month in the journal Nature Photonics.

Solar cells made from polymers are a popular topic of research due to their appealing properties. But researchers are still struggling to efficiently generate electrical power with these materials.

"The field is rather immature—it's in the infancy stage," said Luping Yu, professor in chemistry, fellow in the Institute for Molecular Engineering, who led the UChicago group carrying out the research.

The active regions of such solar cells are composed of a mixture of polymers that give and receive electrons to generate electrical current when exposed to light. The new polymer developed by Yu's group, called PID2, improves the efficiency of electrical power generation by 15 percent when added to a standard polymer-fullerene mixture.

"Fullerene, a small carbon molecule, is one of the standard materials used in polymer solar cells," Lu said. "Basically, in polymer solar cells we have a polymer as electron donor and fullerene as electron acceptor to allow charge separation." In their work, the UChicago-Argonne researchers added another polymer into the device, resulting in solar cells with two polymers and one fullerene.

Luyao Lu, a graduate student in chemistry, works in the solar cell characterization facility of the University of Chicago's Gordon Center for Integrative Science. Lu is the lead author of a Nature Photonics article describing the development of a new type of polymer solar cell that displays enhanced power conversion efficiency. Credit: Andrew Nelles

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