Zhenan Bao, Stanford University, CA, USA, and colleagues developed the first all-carbon solar cell. They replaced the silver and indium tin oxide (ITO) used in conventional electrodes of solar cells with graphene and single-walled carbon nanotubes. The photoactive layer is made of carbon nanotubes and C₆₀. This is sandwiched between the two electrodes. The research team recently filed a patent for the entire device.

The entire device can be built using simple coating methods. It does not require expensive tools and machines.

One drawback of the all-carbon prototype is that it primarily absorbs near-infrared wavelengths, contributing to a laboratory efficiency of less than 1 %. The team is looking at a variety of ways to improve efficiency.
The ability of carbon solar cells to out-perform conventional devices under extreme conditions make them attractive for next-generation electronic devices and solar cells.

• Evaluation of Solution-Processable Carbon-Based Electrodes for All-Carbon Solar Cells,
  Marc P. Ramuz, Michael Vosgueritchian, Peng Wei, Chenggong Wang, Yongli Gao, Yingpeng Wu, Yongsheng Chen, Zhenan Bao,
  ACS Nano 2012.
  DOI: 10.1021/nn304410w