Last year, researchers from the Massachusetts Institute of Technology (MIT) announced that they had successfully used carbon nanotubes for "funneling" and concentrating electrons in photovoltaic cells – this meant that smaller solar cells created using the nanotubes could produce as much or more electricity than larger conventional cells. Now, the efficiency of these nanotube solar cells is being boosted further ... with the help of a virus.
One of the reported problems with the nanotubes has been their tendency to clump together and short each other out. To address that problem, a team of MIT scientists called upon a genetically-engineered version of a virus known as M13. When introduced to the nanotube "forest," the virus' peptides (polymers made from amino acids) bonded tightly with the nanotubes, both holding them in place AND apart from one another. One virus is capable of holding five to ten nanotubes, allotting about 300 peptide molecules to each tube.
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Once the virus had performed that service, the scientists then changed the acidity of its environment, causing it to produce titanium dioxide (TiO2) and coat each nanotube with the substance. As the solar cells being tested were of the dye-sensitized variety, utilizing TiO2 as their active layer, this also helped the devices to better covert solar energy to electricity.
Between the superior alignment and the production of TiO2, the virus-assisted nanotubes increased the solar cells' power conversion efficiency by about a third, from 8 percent to 10.6. While the technology was tested on dye-sensitized solar cells, the scientists say that it should also improve the performance of other types of solar cells, such as quantum-dot and organic.
Additionally, the virus makes the nanotubes water-soluble, which allows for them to be introduced to cells via a water-based, room temperature process. The scientists believe that it would be relatively easy to add such a procedure to the solar cell production process.
The MIT research is published online this week in the journal Nature Nanotechnology.