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Infrared-Harvesting Solar Cells Made Entirely from Carbon Invented at MIT

An atomic-force microscope image of a layer of single-walled carbon nanotubes deposited on a silicon surface, as the first step in manufacturing the new type of solar cell developed by an MIT team. Individual nanotubes can be seen in the image.
Photo: Rishabh Jain et al

MIT researcher Michael Strano, previously involved in projects like thermopower waves, carbon nanotube energy storage and others related to carbon nanotubes, discovered a new type of all-carbon solar cell made from buckyballs (aka C60). Strano’s new cells are sensitive to the near-infrared spectrum of light, which makes up to 40% of the solar energy hitting our planet.

In his approach, Strano and his team used high-purity carbon nanotubes and buckyballs (carbon molecules resembling soccer balls). “It has only been within the last few years or so that it has been possible to hand someone a vial of just one type of carbon nanotube,” he says.

So far, the conversion efficiency of these infrared solar cells has been very low, only 0.1 percent. However, postdoc and co-author Kevin Tvrdy already identified two key inefficiency sources: the use of heterogenous nanotube mixtures and materials that contain a mix of single-walled and multiwalled nanotubes.

Strano’s nanotube solar cells are transparent to the invisible light, thus the technology could be used to equip already-made solar cells, without much of an effort. Furthermore, carbon nanotubes have high porosity, allowing them to capture very large amounts of light on a small surface. The new solar cells are also the first cells to be made entirely from carbon, with no polymers attached to them, like older carbon cells had.

As I said earlier, 40 percent of Earth’s solar power share is lost as heat when it hits solar panels. The need for cheap photovoltaics is higher with each year, and the infrared spectrum has to be harnessed in order for solar cells to become competitive with coal or gas on a large scale.

[via cleantechnica/MIT news]

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