Nature and Science News are reporting on research at the Laboratory of Organic Optics and Electronics at MIT using photosynthetic proteins derived from spinach to produce electricity. While the light->electricity conversion efficiency is only 12%, the researchers are confident that they'll be able to boost it to at least 20% in relatively short order. Even if they can't get it up past commercial silicon-based solar cells, protein-based cells would have some interesting advantages:
For example, many solar cell materials degrade over time, but a protein-based solar cell could be self-repairing, says [lead researcher Marc] Baldo. Just as living plants replenish their photosynthetic proteins by swapping out the old copies for new ones, it might become possible to flush a solution of fresh proteins through a solar cell to replace the photosynthetic molecules as they degrade...
While recent research has replicated some of the functions of photosynthesis, this would directly use plant proteins -- a more difficult scientific challenge, but potentially of much greater ultimate value.
Actually, I think the most important thing about this breakthrough is that the manufacturing process sounds like it would be quite benign: grow some spinach, use some peptide surfactants & whatnot other stabilizers, and conductive clear polymer sandwich. Compare that to silicon chip fabbing, or the gallium arsenide ones, and it'll make a world of difference--both for CO2 payback time (currently 6 years for most solar cells) and for toxin production.