Materials Scientists' Solar Cell Has a Virus—and That's a Good Thing

By Patrick Morgan | April 26, 2011 7:23 pm

What’s the News: In traditional solar cells, sunlight is absorbed by the cell (made from silicon or titanium dioxide), freeing electrons, which travel across the cell to an electron collector, or electrode. A problem with solar cells is that many electrons don’t find their way to the electrode; carbon nanotubes can be used as bridges between the loosened electrons and the electrode, but nanotubes tend to bunch up, decreasing the efficiency and causing short circuits. Researchers have now created genetically engineered viruses can be used to keep the nanotubes in place, increasing energy conversion by nearly one-third. “A little biology goes a long way,” research group leader Angela Belcher told MIT News, noting that the entire virus-nanotube bridging layer represents only 0.1% of the finished cell’s weight.

How the Heck:

  • The virus (called M13) holds nanotubes in place with its peptides, a protein building block that binds to the carbon nanotubes. A single virus “can hold five to 10 nanotubes, each of which is held firmly in place by about 300 of the virus’s peptide molecules,” reports Technology Review.
  • In addition to keeping the nanotubes from clumping, the viruses are also helpful because they’re engineered to produce titanium dioxide, which is helpful for solar cells made of the same material, according to chemistry professor Prashant Kamat, who was not involved in the study:  “It is likely that the virus template assembly has enabled the researchers to establish a better contact between the TiO2 nanoparticles and carbon nanotubes. Such close contact with TiO2 nanoparticles is essential to drive away the photo-generated electrons quickly and transport it efficiently to the collecting electrode surface.”

What’s the Context:

  • Although most solar cells are composed of silicon, these researchers used a titanium dioxide solar cell. They say their virus-nanotube technique can be applied to other solar cells, such as organic and quantum-dot solar cells.
  • Connecting the nanotubes with viruses makes the virus-nanotube layer soluble in water, so and can easily be produced at room temperature using a water-based technique.
  • These same researchers have gotten viruses to do other creative tasks for them, including building a lithium-ion battery.

Not So Fast: Kamat says that “the industry is likely to adopt such processes,” but this is an early-stage study, so don’t expect to pick up virus-enhanced solar cells from Home Depot anytime soon.

Reference: Xiangnan Dang et al. “Virus-templated self-assembled single-walled carbon nanotubes for highly efficient electron collection in photovoltaic devices.” Nature Nanotechnology. doi:10.1038/nnano.2011.50

Image: flickr / Mulad

  • Anatomy Student

    So cool! … but if the layer is soluble in water, won’t it wash off if it rains?

  • Torbjörn Larsson, OM

    The press release and this post is a little confusing on the point of the virus use, more’s the pity since it should be the main points.

    The viruses, which have little to no enzymatic functions outside a host cell (at least in the wild state, AFAIK), likely isn’t producing the TiO2 nanoparticles as much as _enabling_ production. Organics binds well to TiO2 and can be crystalline seeds as well as adhesive layer.

    @ Anatomy Student:

    It is very economical compared to, say, vacuum processes if you can produce electronic (or other) films by water soluble materials. Substrates can be spun, i.e. poured on and spun out to required thickness set by rotation speed among other factors, having the excess leave the substrate.

    Or otherwise used to produce a thin coat rapidly, dipping is certainly fast if not so reproducible. Later processes are used to fixate the film.

    Here I would presume what I wrote above, the virus-tube layer is used as TiO2 seed (preferably in some subsequent liquid chemical growth process if possible). At some or several stages resulting layers are likely fixated somehow, though the protein/Tio2 bond certainly helps anyway. Heated/sintered maybe, at the end probably glass covered or perhaps coated with a thin layer of transparent MnO2 depending on the application.

    One reason alone to supply an over-layer is that you can increase optical efficiency, say by successively adapt refraction index between the air/film interface to couple more light into the device. This may at a guess be an economical tipping point for solar cell applications that aren’t all that efficient at the basics. Glass usually goes the wrong way though (high refraction index).

  • Aleta Hirn

    goodpoints there. I did my own search on

  • airheat pumps

    This is really cool. They already have solar panel technology in place where your windows can become solar panels . I think the most important thing is that solar panels come down in price – whilst these technologies are really cool, it’d be best for the environment for households to start adopting them on a much larger scale


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