UCLA Makes Thin-Film Polymer Solar Progress

Using solar cell made out of everyday plastics could promise to be a more affordable way to harness the sun's rays, say researchers at the University of California, Los Angeles (UCLA) Henry Samueli School of Engineering and Applied Science. Percentage efficiencies are still in the mid-single digits but recent gains continue to give researchers hope that these polymer cells could soon give silicon cells a run for their money.

In research published in Nature Materials magazine, UCLA engineering professor Yang Yang, postdoctoral researcher Gang Li and graduate student Vishal Shrotriya showcase their work on a new plastic (or polymer) solar cell they hope to produce at 10 to 20 percent of the current cost of traditional cells, thus making the technology more widely available.

Made of a single layer of plastic sandwiched between two conductive electrodes, UCLA's solar cell is easy to mass-produce and costs much less to make. The polymers used in its construction are commercially available in such large quantities that Yang hopes cost-conscious consumers worldwide will quickly adopt the technology.

Independent tests on the UCLA solar cell already have received high marks. The nation's only authoritative certification organization for solar technology, the National Renewable Energy Laboratory (NREL), has helped the UCLA team ensure the accuracy of its efficiency numbers.

According to Yang, the 4.4 percent efficiency achieved by UCLA is the highest number yet published for plastic solar cells (Ed. note: It should be mentioned that recent achievements above the 5 percent mark were announced this week from a team of researchers from New Mexico State University and Wake Forest University. These results, however, were not yet confirmed by NREL).

"As in any research, achieving precise efficiency benchmarks is a critical step," Yang said. "Particularly in this kind of research, where reported efficiency numbers can vary so widely, we're grateful to the NREL for assisting us in confirming the accuracy of our work."

Given the strides the team already has made with the technology, Yang calculates he will be able to double the efficiency percentage in a short period of time. The target for polymer solar cell performance is ultimately about 15 to 20 percent efficiency, with a 15- to 20-year lifespan. Large-sized silicon modules with the same lifespan typically have a 14 to 18 percent efficiency rating.

The plastic solar cell is still a few years away from being available to consumers, but the UCLA team is working diligently to get it to market.

"We hope that ultimately solar energy can be extensively used in the commercial sector as well as the private sector. Imagine solar cells installed in cars to absorb solar energy to replace the traditional use of diesel and gas. People will vie to park their cars on the top level of parking garages so their cars can be charged under sunlight. Using the same principle, cell phones can also be charged by solar energy," Yang said. "There are such a wide variety of applications."