Organic solar cell efficiency breakthrough

South Korean scientists, working in conjunction with American researchers, say they have reached a new level of efficiency in an organic solar cell by using a tandem design.

Scientists at South Korea's Gwangju Institute of Science and Technology worked together with Nobel laureate Alan Heeger, professor of physics at U.C. Santa Barbara, to create the new tandem cells under a South Korean-led project started in May, 2006.

Tandem solar cells, in which two solar cells with different absorption characteristics are linked, can convert a wider range of the solar spectrum.

The result of the new architecture was a power conversion efficiency of 6 per cent.

"This is the highest number reached by any plastic-based organic photovoltaic solar cell that some scientists argued could not surpass the five per cent mark," said Lee said Professor Lee Kwang-Hee, who led the Gwangju Institute's research team.

Organic photovoltaics promise substantially lower costs than conventional silicon cells.

"It takes 2 U.S. dollars to generate one watt of electric power if you use silicon solar cells," explained Professor Lee, "Only ten U.S. cents [would be required] to generate 1 watt if you use this tandem polymer solar cell," said Lee.

The use of inexpensive plastics is a key to cut down the cost for its fabrication.

"This plastic solar cell bends and folds, making it possible to be wearable to the body or to be printed into devices," said Lee Hee-Joo, a member of the team at the Gwangju Institute.

Some criticize the use of petroleum-based plastics in solar cells, arguing that renewable energy should not further support fossil fuel industries.

Professor Lee expects the technology to take between three to five years to reach the market.

The team's findings were published in the latest issue of Science magazine.

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