Carbon nanotubes for use in solar panels have increased efficiencies from 4.4% in 2007 to 8% today. What has held back further results is the tendencies for nanotube to clump together, short circuiting areas in the cell, which reduce their overall outputs.
Professor Angela Belcher and graduate students Xiangnan Dang and Hyunjung Yi, of MIT, have produced a biological fix to the clumping issue during manufacturing. They modified a bacteria infecting virus, called M13, that will attach to the nanotube and prevent them from clumping. The virus contains peptides that bind to the nanotubes which keeps them separate. One virus can control 10 nanotubes by 300 of its peptides. The team also modified the virus further to produce a coating of titanium dioxide (TiO2) onto the nanotubes. This is a major component of the dye-sensitized titanium dioxide solar cell. This allows for more of the electrons to move from the cell material, when hit by sunlight, into the conducting nanotubes to the collecting electrode. Additionally, the virus could also let the nanotube be used in a water based system that works at lower room temperatures.
The power conversion efficiency jumps from 8% to 10.6% with the virus process added. A 32.5% boost (to the original efficiency) over the many acres of solar farms could have a significant impact on future alternative energy usage. The hope is that the licensing of the virus will not immediately deter use.
pic via Matt Klug, Biomolecular Materials Group, MIT. MIT quote"In this diagram, the M13 virus consists of a strand of DNA (the figure-8 coil on the right) attached to a bundle of proteins called peptides — the virus coat proteins (the corkscrew shapes in the center) which attach to the carbon nanotubes (gray cylinders) and hold them in place. A coating of titanium dioxide (yellow spheres) attached to dye molecules (pink spheres) surrounds the bundle. More of the viruses with their coatings are scattered across the background.