science

Plants and photosynthetic bacteria contain molecules that convert photons to energy very efficiently. The trick to harnessing these molecules for solar cells is marrying these relatively delicate molecules with electronics.

Researchers from MIT, the U.S. Naval Research Laboratory, and the University of Tennessee have mixed biology and electronics in solar cells that use photosynthetic spinach leaf molecules or photosynthetic bacteria to convert light to electricity.

When light shines on the spinach leaf molecules and photosynthetic bacteria they produce an electrical current that is captured by electrical contacts.

The internal quantum efficiency of the researchers' first-generation prototypes is 12 percent. The method has the potential to exceed a power conversion efficiency of 20 percent, making it as efficient as today's commercial solar cells, according to the researchers.

The method could be used to fabricated solar devices on plastic and other thin, flexible surfaces using inexpensive spray-on techniques. The method could eventually be used to make large-area photovoltaic cells and ultra-fast photodetectors, according to the researchers.

The researchers' prototype consists of a self-assembled layer of the photosynthetic molecules mixed with surfactant peptides, covered with an organic, semiconducting protective coating, and sandwiched between metal contacts. Surfactant peptides are soap-like molecules.

The researchers are working on improving the device's efficiency and lifetime.

Molecular photovoltaic devices could be used practically in five years, according to the researchers. The work appeared in the June 9, 2004 issue of Nano Letters.

http://www.technologyreview.com/articles/04/08/rnb_083104.asp?trk=nl