Giving Plastic Solar Cells an Energy Boost  

Technology Review has an article on research into improving the efficiency of plastic solar cells - Giving Plastic Solar Cells an Energy Boost.

If the efficiency of polymer solar cells--which are cheaper and lighter than silicon cells--can be boosted significantly, they could be ideal for plastering on rooftops or laminating on windows.

Solarmer Energy, based in El Monte, CA, is on target to reach 10 percent efficiency by the end of this year, says Yue Wu, the company's managing director and director of research and development. Organic cells will likely need at least that efficiency to compete on the photovoltaic market.

In collaboration with Luping Yu, a professor at the University of Chicago, the startup has previously engineered polymers that absorb a broad range of wavelengths and has made cells that convert sunlight to electricity with a record efficiency of nearly 8 percent.

Polymer solar cells with even higher efficiencies are in the works. Solarmer is collaborating with Yang Yang, a materials science and engineering professor at the University of California, Los Angeles. Yang is working on a stack of multiple cells that absorb different bands of light. He expects to achieve 12 to 15 percent efficiencies using this approach along with new polymers and better device design. So far, he has made laboratory prototypes that are better than 6 percent efficient.

Polymer solar cells should be cheaper to make than thin-film cadmium-telluride or copper indium gallium selenide (CIGS) ones because they use low-cost materials that are easy to print, says Michael McGehee, a materials science and engineering professor at Stanford University. But McGehee believes polymer cells will need to be more than 15 percent efficient to have a major impact on the solar power market. "We still don't understand the physics well enough to know what the theoretical limit is," McGehee says. "I think cells with 15 to 20 percent could be possible."

GE has confirmed long-standing speculation that it plans to make thin-film solar panels that use a cadmium- and tellurium-based semiconductor to capture light and convert it into electricity. The GE move could put pressure on the only major cadmium-telluride solar-panel maker, Tempe, AZ-based First Solar, which could drive down prices for solar panels.

Last year, GE seemed to be getting out of the solar industry as it sold off crystalline-silicon solar-panel factories it had acquired in 2004. The company found that the market for such solar panels--which account for most of the solar panels sold worldwide--was too competitive for a relative newcomer, says Danielle Merfeld, GE's solar technology platform leader.

She says cadmium-telluride solar is attractive to GE in part because, compared to silicon, there's still a lot to learn about the physics of cadmium telluride, which suggests it could be made more efficient, which in turn can lower the cost per watt of solar power. It's also potentially cheaper to make cadmium-telluride solar panels than it is to make silicon solar cells, making it easier to compete with established solar-panel makers. Merfeld says GE was encouraged by the example of First Solar, which has consistently undercut the prices of silicon solar panels--and because of this has quickly grown from producing almost no solar panels just a few years ago to being one of the world's largest solar manufacturers today.