Chlorophyll-a photovoltaic cells

ALTHOUGH the properties of an organic photovoltaic cell in which the photoactive material is microcrystalline chlorophyll-a (Chl-a). In a sandwich configuration having chromium and mercury as the electrodes, the Chl-a cell, (Cr|Chl-a|Hg), achieves a power conversion efficiency of the order of 10 ^-2%, which is among the highest ever reported for organic photovoltaic cells^1,2. In contrast to the usual methods for preparing thin films (such as vapour deposition), a thin microcrystalline Chl-a film is prepared on a Cr electrode surface by the simple method of electrodeposition³. Such a film is fairly uniform and is uniquely efficient in the photocharge generation. The microcrystalline form of Chl-a differs from the aggregated form of monomer Chl-a in that it has an ordered structure and has a strong absorption band in the far red, peaking at 740-745 nm. A water-Chl-a adduct structure has been proposed for this type of Chl-a (ref. 4).