Carbon nanotubes make solar photovoltaic cells cheaper

Researchers from Northwestern University have developed a carbon material that could revolutionize the way solar cells are made. The new solar cell material is a transparent conductor made of carbon nanotubes, which offers an alternative approach to solar cell production. Current solar cell technology relies on a relatively rare element.

Carbon nanotubes are an element that is abundant on Earth, and they are expected to promote the long-term development of solar energy by providing a more cost-effective way to make solar cells. In addition, the material has good flexibility, so that the solar cells made of it can be integrated into fabrics and clothing to provide portable power for personal electronics and military operations.

The research results were published in the October 2011 issue of Advanced Energy Materials magazine.

Solar cells are made up of a multi-layer structure, including a transparent conductor layer, through which sunlight enters the cell and electricity is transmitted, so this conductor must be both conductive and transparent. There are very few materials that have both properties.

Currently, indium tin oxide is the most widely used material for transparent conductors, but this material has two disadvantages: it is brittle and relies on the relatively rare element indium. Therefore, the growing demand for solar cells will greatly increase the price of indium.

As solar energy technology becomes more popular, the supply of indium may become insufficient, so people are hoping that an element that is abundant on Earth, such as carbon, can replace indium in solar energy technology.

The research team used single-walled carbon nanotubes to develop materials that can replace indium tin oxide, and further identified the most efficient types of carbon nanotubes: metallic carbon nanotubes and semiconducting carbon nanotubes.

The researchers found that when the two types of carbon nanotubes are used as transparent conductors in organic solar cells, the metallic carbon nanotubes are 50 times more efficient than the semiconducting carbon nanotubes.