Solar energy conversion by chloroplast photoelectrochemical cells

Solar energy can be captured by photochemical or photoelectric processes in which a gradient of chemical potential can be generated using photochemical redox reactions. Photosynthesis is the most efficient system for quantum conversion and storage of solar energy 1 . Various biomimetic systems have been constructed as models for the conversion of light to electrical energy 2–11 . These biological photoelectrochemical cells have utilized macrocrystalline chlorophyll a (Chl a ) 2 , chlorophyll liquid crystals deposited on the electrodes 3–5 or incorporated into filters 6 , bilayer lipid membranes 7 , chloroplast membranes 8 , chloroplasts 9 and bacterial reaction centres 10,11 . The power conversion efficiencies are mostly very low (≈0.002%). We describe here a chloroplast photoelectrochemical cell which generates large photovoltage and photocurrent, and has a power conversion efficiency close to 1%.