Roughened carbon nanotube films may help improve solar cells at lower cost

June 17th, 2008 - 12:46 pm ICT by ANI  

Washington, June 17 (ANI): Scientists from three institutions have revealed how nanotechnology may help improve the performance of solar cells at a lower cost.

Jessika Trancik of the Santa Fe Institute, Scott Calabrese Barton of Michigan State University, and James Hone of Columbia University say that a film of carbon nanotubes may be able to replace two of the layers normally used in a solar cell.

The existing solar cells, known as dye-sensitized solar cells, have a transparent film made of an oxide that is applied to glass and conducts electricity. A separate film made of platinum acts as a catalyst to speed the chemical reactions involved.

However, the oxide films perform better on a rigid and heat resistant substrate like glass, which increases cost and limits the kinds of products that can be made. Making platinum films also involves expensive equipment.

The researchers have now found out a way to use carbon nanotubes to create a single layer that can perform the functions of both the oxide and platinum layers.

They say that the carbon nanotubes needed to have three properties for the purpose, viz. transparency, conductivity, and catalytic activity.

According to them, ordinary carbon nanotubes films are so-so in each of such properties, and any of them could be improved by sacrificing one of the others.

The researchers paid attention to a previous theory suggesting that materials might function better as catalysts when they had tiny defects, which would act as sites for chemicals to attach.

Accordingly, the researchers exposed the carbon nanotubes to ozone so as to roughen them a bit.

They found that very thin films became dramatically better catalysts, with more than ten-fold improvement.

The researchers say that the performance of the films got close to that of platinum films.

“That’s remarkable because platinum is considered pretty much the best catalyst there is,” Trancik says.

To address the trade-off between transparency and conductivity, the researchers tried another trick on a bottom layer of tubes and created carbon nanotubes that were longer.

The researchers say that it allowed them to improve both conductivity and transparency.

They believe that the carbon nanotube films might be used in fuel cells and batteries as well.

“This study is an example of using nanostructuring of materials changing things like defect density and tube length at very small scales to shift trade-offs between materials properties and get more performance out of a given material. Making inexpensive materials behave in advanced ways is critical for achieving low-carbon emissions and low cost energy technologies,” Trancik says. (ANI)

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