Biological photovoltaics

Biological photovoltaics, also called biophotovoltaics[1] or BPV, is an energy-generating technology which uses oxygenic photoautotrophic organisms, or fractions thereof, to harvest light energy and produce electrical power.

[4] A relatively high-potential reaction takes place at the cathode, and the resulting potential difference drives current through an external circuit to do useful work.

These organisms are able to use light energy to drive the oxidation of water, and a fraction of the electrons produced by this reaction are transferred to the extracellular environment, where they can be used to reduce an anode.

If water is regenerated there is a closed loop in terms of electron flow (similar to a conventional photovoltaic system), i.e. light energy is the only net input required for production of electrical power.

This improves the efficiency of light-to-electricity conversion by minimising the number of reactions separating the capture of light energy and reduction of the anode.

[7] A soluble redox mediator (a small molecule capable of accepting and donating electrons) may be required to improve the electrical communication between photosystem and anode.

[11] Cyanobacteria are typically used in these systems because their relatively simple arrangement of intracellular membranes compared to eukaryotic algae facilitates electron export.

Isolated photosystems and sub-cellular photosynthetic fractions may be able to directly reduce the anode if the biological redox components are close enough to the electrode for electron transfer to occur.

Quinones, phenazines, and viologens have all been successfully employed to increase current output from photosynthetic organisms in biological photovoltaic devices.