At the heart of the device is a protein complex dubbed Photosystem I (PSI). Derived from spinach chloroplasts, PSI is 10 to 20 nanometers wide. Around 100,000 of them would fit on the head of a pin. "They are the smallest electronic circuits I know of," said researcher Marc A. Baldo, assistant professor of electronic engineering and computer science at MIT.

Baldo and other researchers from MIT, the University of Tennessee and the U.S. Naval Research Laboratory, including electrical and biomedical engineers, nanotechnology experts and biologists, collaborated on the world's first solid-state photosynthetic solar cell. The work was reported in NanoLetters, a publication of the American Chemical Society.

"We have crossed the first hurdle of successfully integrating a photosynthetic protein molecular complex with a solid-state electronic device," Baldo said.

Plants' ability to generate energy has been optimized by evolution, so a spinach plant is extremely efficient, churning out a lot of energy relative to its size and weight. But combining biological and non-biological materials in one device has stymied researchers in the past. Biological materials need water and salt to survive-both are deadly for electronics.

FROM WET TO DRY

A new twist in the current work is a membrane of peptide surfactants-similar to the main ingredient in soap-that helped the photosynthetic complexes self-assemble and stabilize while the circuit was fabricated.

So far, scientists and engineers' efforts to harness the photosynthetic properties of green plants have been most successful with naturally soft organic materials in liquid solutions. But if organic solar cells are to be practical for commercial device
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Contact: Denise Brehm
brehm@mit.edu
617-253-2704
Massachusetts Institute of Technology
20-Sep-2004