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Old Posted Apr 27, 2011, 3:13 AM
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MIT Researchers Use Army of Subjugated Viruses to Build Solar Cells

Jason Mick (Blog) - April 26, 2011 10:35 AM

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All solar cells at a fundamental level rely on some sort of energy harvesting layer. For most cells today this layer is either a thin film or layers of elements deposited on a silicon substrate.

Outside of solar cells, in the realm of nanomedicine and materials engineering, carbon nanotubes are a hot item. These nanoscopic tubes, composed of hexagonal units of bonded carbon, are super strong -- and in some cases -- highly conductive.

Many researchers have considered tossing the tubes in solar cells, but early results were not promising.

Undeterred the MIT team set out to find why. What they determined was that past efforts had failed as they deposited a mix of certain types of tubes that acted as conductors and certain types of tubes that acted as semiconductors. Worse, the tubes clumped together, further impairing the efficiency.

In order to create the desired target -- a conductive nanotube layer -- the MIT team opted for a novel approach, enlisting the help of viral henchmen. Graduate students Xiangnan Dang and Hyunjung Yi, along with Energy Professor Angela Belcher [profile], found that a specific genetically engineered virus -- known as M13 -- improved the tube conductivity by reducing clumping and the number of semiconducting tubes.

Since they were already going the unconventional route, the team decided to test the newly created material layer on a special type of cell, based on titanium dioxide. These TiO2 cells don't use a silicon substrate and are known commercially as "dye-sensitized" solar cells. Their advantages include that they can be less expensive to produce and are lighter than silicon substrate designs.

Adding the nanotube layer improved the efficiency from 8 percent to 10.6 percent -- an increase of about a third. And that huge boost comes despite the fact that the virus/nanotube mix only takes up 0.1 percent of the finished cell's weight. Professor Belcher summarizes, "A little biology goes a long way."

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