Cheap Dye-Sensitized Solar Cell Moves toward Commercialization

C (on a rooftop, for instance) can expand and rupture the panel's seal. The dye cells' iodine-based electrolyte is also corrosive enough to eat through even rust-resistant metals such as aluminum and stainless steel.

Northwestern University chemist Mercouri Kanatzidis, materials scientist Robert Chang, and two graduate students replaced the dye cells' liquid electrolyte with a solid iodine-based semiconductor. While prior solid-state designs have reduced the power output of dye cells, the Northwestern design actually boosts performance, the researchers say, because the cesium-tin-iodine semiconductor that replaces the liquid electrolyte also absorbs light. "Our material actually absorbs more light than the dye itself," says Kanatzidis.

In a report in Nature last week, the Northwestern team claims its cell converts 10.2 percent of incoming light to electricity—far higher than the 7 percent efficiency of the best existing solid-state dye cells. Sean Shaheen, an expert in organic photovoltaics at Denver University, says that the Northwestern cell's efficiency would be closer to 8 percent under standard measurement conditions. But Shaheen says it is still an important development for dye cells.

Kanatzidis says it could be possible to commercialize the design if the efficiency of the cells can be pushed above 11 percent. That is lower than the 12 to 16 percent efficiency of commercial thin-film solar panels and far below the efficiency of silicon panels. But the cost of manufacturing dye-based cells should also be lower.

Australian solar developer Dyesol is seeking to exploit low-cost processing to commercialize conventional dye-solar technology—liquid electrolyte included. Its strategy is to integrate dye-based solar into building materials such as glass high-rise panels and steel roofing sheets. This March, Dyesol's South Korean joint venture partner, Timo Technology, installed glass panels on a building in Seoul. And Dyesol is partnering with India's Tata Steel to develop dye-solar-coated steel roofing.

Damion Milliken, Dyesol's research and development manager, insists that liquid electrolytes can be contained. "Dyesol and others have produced devices with excellent long-term stability which have been subjected to accelerated testing equivalent to 25 years' life and beyond," Milliken says. "The technology is commercially viable."

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