First true “all-carbon” solar cell developed

Stanford University Researchers have developed a solar cell, made entirely of carbon. It is an alternative to the traditional expensive solar cells. It is made of carbon and it is so flexible that it can be coated onto buildings and car windows. The prototype of the cell has made.

Stanford graduate student Michael Vosgueritchian, who is co-lead author of the study, says that while other groups have previously claimed to have developed all-carbon solar cells, the “all-carbon” component of these other cells was limited to the middle active layer. In comparison, the entirety of the Stanford solar cell, including the electrodes, is made from carbon materials.

The Stanford research scholars have used graphene and single-walled carbon nanotubes instead of expensive materials, silver and indium tin oxide, which are used in an ordinary solar cell.  The research team was led by Professor Zhanan Bao and according to the Professor, these materials which are used in the 'all-carbon' solar cell, boast electrical conductivity and light absorption properties.

The active layer of the Stanford team’s solar cell is made from a material containing carbon nanotubes and “buckyballs,” which are soccer ball-shaped molecules with carbon atoms at each vertex.

MIT’s proof of concept devices achieved an efficiency of only 0.1 percent and Stanford’s prototype can only claim a laboratory efficiency of less than one percent, which is far short of the efficiencies seen in conventional silicon solar cells. However, Bao says, “with better materials and better processing techniques, we expect that the efficiency will go up quite dramatically."

The main problem is that both the MIT and Stanford carbon-based prototype solar cells primarily absorb light in the near-infrared part of the spectrum. To improve efficiency, the Stanford team is experimenting with carbon nanomaterials that can absorb more light in a broader range of wavelengths, including the visible spectrum.

They are also looking at ways to enhance the smoothness of the solar cell as, “roughness can short-circuit the device and make it hard to collect the current,” says Bao. "We have to figure out how to make each layer very smooth by stacking the nanomaterials really well."

Despite the inefficiencies compared to traditional solar cells, there are some conditions in which carbon solar cells can outperform conventional devices. Since materials made from carbon remain stable in air temperatures of almost 1,100° F (593° C), they can perform in extreme conditions.

"We believe that all-carbon solar cells could be used in extreme environments, such as at high temperatures or at high physical stress," says Vosgueritchian. "But obviously we want the highest efficiency possible and are working on ways to improve our device."