Tiny nanotubes to generate big solar power



Carbon nanotube

A computer representation of a carbon nanotube.

Credit: Wikimedia

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Tiny carbon structures, called 'carbon nanotubes', may form the building blocks of new, highly efficient solar cells, according to recent research.

More light is converted into electricity in the new cells compared to conventional solar technology, with less energy wasted as heat. The research was published online last week in the journal Science.

"Nanotubes may lead to high efficiency solar cells that may surpass the limitations of many other materials," said lead researcher Nathaniel Garbor, a US PhD student from Cornell University in New York.

"In nanotubes, a significant fraction of excess energy is converted into extra electrons, rather than heat," he said.

Solar cells are traditionally made of silicon, which heats up when light shines on it. These cells work best at lower temperatures, and require constant cooling. A lot of potentially useful energy is discarded as unwanted heat.

Garbor's cells, however, are made of a 'rolled-up' sheet of carbon molecules, just one molecule thick. These tiny cells - about the size of a molecule of DNA - are then wired into an electrical circuit.

The circuit causes one end of the carbon nanotube to conduct positive charge, while the other end conducts negative charge. Light shined between these two regions causes a mixture of positive and negative charges to become excited. These charges then move into the appropriate area of the cell; like cars on a highway, charges flow through the carbon nanotube, generating electricity.

Significantly, excess energy is converted into more positive and negative charges, rather than heat.

"Each photon [(unit of light) in our device] is actually able to make several positive and several negative charges," Garbor told G Online.

"This is very different than standard materials in which only one negative and one positive charge are produced by incoming light. Ultimately, these charges are counted as electric current and can be used to produce electrical power," Garbor said.

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