Making a Soft Cell

New solar technologies are finding their way into prototypes.

Plastic solar cells can't yet compete with conventional silicon photovoltaics for efficiently producing large-scale power. But they've become good enough that at least one company, Lowell, MA-based Konarka, has moved past the proof-of-concept phase and is putting them into products.

The Army, Air Force, and Textronics, a company based in Wilmington, DE, are now incorporating Konarka's cells into the structures of tents for powering computers and the fabric of handbags for charging cell-phone and laptop batteries.

Konarka's solar cells are printed or coated on rolls of plastic -- much like photographic film. Tiny particles embedded in the film then absorb light and spit out electrons, which are transported by an electrolyte and harvested by electrodes.

So far, the company has demonstrated that its cells can charge cell-phone batteries, extending talking time, or even eliminating the need to plug into an outlet -- assuming one lives somewhere like Phoenix and isn't addicted to the device.

Konarka has also shown that the materials in its solar cells can be tuned to absorb and reflect different wavelengths of light; and, unlike traditional photovoltaic materials, the plastic substrate can conform to irregular shapes. According to one of Konarka's partners, Textronics, the end-product can even be made to feel like ordinary cloth.

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In anticipation of growing demand, Konarka has also partnered with a German printing company, Kurz, to manufacture its plastic-film solar cells on a large scale. Such a ramping up, however, will depend on when and if third parties are satisfied that the cells can be smoothly integrated into their own products.

Konarka's efforts reflect a growing push toward cheap solar (see "Solar-Cell Rollout," Technology Review, July 2004). The ultimate goal is to make solar power, which now costs 4 to 5 times as much as grid electricity, competitive with fossil fuels. It's a challenge that could become easier if fuel prices continue to rise.