April 26, 2011

M13 Virus Improves Solar Cells, MIT

The performance of any solar cell can be improved if the electrons generated can be carried away more efficiently. Single-walled carbon nanotubes have very high electron mobility, so if a nanocomposite material could be built which is a mashup of a photovoltaic (PV) material and carbon nanotubes, you can get a much better solar cell. Developers at MIT have used M13 Virus to improve solar cells using this exact mechanism.

Building carbon nanotubes into a PV material is difficult as the nanotubes tend to clump together and will short out. When the M13 virus was used as a template in the material, it kept the nanotubes apart and improved the solar cell efficiency from 8% to 10.6%.

The viruses actually perform two different functions in this process. First, they possess short proteins called peptides that can bind tightly to the carbon nanotubes, holding them in place and keeping them separated from each other. Each virus can hold five to 10 nanotubes, each of which is held firmly in place by about 300 of the virus's peptide molecules. In addition, the virus was engineered to produce a coating of titanium dioxide (TiO2), a key ingredient for dye-sensitized solar cells, over each of the nanotubes, putting the titanium dioxide in close proximity to the wire-like nanotubes that carry the electrons.

While dye-sensitized solar cells were used in this case (where the active layer is based on Titanium di oxide rather than Silicon), the same steps can also be carried out for other types of solar cells.

Just like the highly efficient liquid repellent bacterial biofilm, natural nanostructures (such as viruses and bacterias) can be very useful.