Photovolatic devices could get a huge boost from a solar cell made entirely of carbon.

Stanford University researchers, led by Professor of Chemical Engineering Zhenan Bao, have developed an all-carbon solar cell. It could prove to be cheaper and more flexible than traditional silicon solar cells.

Traditional silicon solar cells are not only rigid, but they require costly tools and machines in order to be manufactured. Even in thin film solar cells used today have electrodes made of indium tin oxide, which are scarce and becoming increasingly expensive.

The Stanford team wanted to address these issues and create a solar cell that requires a less expensive manufacturing process, less rare materials and can be used flexibly. The answer was carbon.

"Carbon has the potential to deliver high performance at a low cost," said Bao. "To the best of our knowledge, this is the first demonstration of a working solar cell that has all of the components made of carbon. This study builds on previous work done in our lab."

The all-carbon solar cell has a photoactive layer for absorbing sunlight in between two electrodes. The photoactive layer is made of carbon nanotubes and Buckyballs (ball-shaped carbon molecules that are just one nanometer in diameter). The electrodes, instead of silver and indium tin oxide, are made of graphene (sheets of carbon) and single-walled carbon nanotubes. These carbon nanotubes, which are 10,000 times narrower than a single human hair, have strong light absorption and electrical conductivity properties.

As for manufacturing, the all-carbon solar cell can be made completely with easy coating methods that don't require expensive tools or a lot of steps.

The big downfall to the all-carbon solar cell is that it isn't nearly as efficient as traditional solar cells. It typically absorbs near-infrared wavelengths, offering an efficiency of less than 1 percent compared to commercial solar cells today.

To increase efficiency, the Stanford team is looking into a few different options. One possibility is making the layers smooth for efficient stacking of nanomaterials. Another possibility is using carbon nanomaterials that can absorb more than just one type of wavelength.