New solar cells to be powered by spinach

• An electronic device that uses spinach to convert light into electrical charge has been developed by US researchers.
• Shuguang Zhang at Massachusetts Institute of Technology, US, and research collaborators integrated a protein complex derived from spinach chloroplasts with organic semiconductors to make a solar cell that could be combined with solid state electronics.
• Chloroplasts are structures in plants cells, packed with chlorophyll - the substance that gives leaves their green colour and allows them to photosynthesise.
• "This is the first time we've been able to harness it."
• The resulting cells are much thinner and lighter than existing solar panels and could eventually be used to make much more efficient panels, says Zhang.
• Previous efforts to integrate the energy harnessing capability of chlorophyll with conventional electronics have failed because it normally requires a watery environment in which to work.
• Zhang's team managed to artificially stabilise the protein complex at the heart of their system - comprised of 14 protein subunits and hundreds of chlorophyll molecules - using synthetic peptides to bind small amounts of water to it, within a sealed unit.
• Light particles, or photons, excite coupled pairs of electrons within chlorophyll, causing an electron to transfer to a nearby receptor molecule.
• Plants use this transfer to power photosynthesis - a chemical reaction that stores energy by converting carbon dioxide to sugar using light - and generates oxygen as a by product.
• The peptides used only keep the protein complex stable for about three weeks and the cells convert only 12% of light to electrical charge.
• But Zhang says efficiency could be boosted dramatically by layering numerous cells on top of one another, as they will still let some light through.
• "This is an interesting piece of basic scientific research," says Devens Gust, at Arizona State University.
• Gust says keeping the system stable and improving the efficiency of photon conversion will be crucial to future success.