Graphene Applications in Photovoltaics Expand

Almost from the moment graphene was first produced, there has been a hunt for the weak link among technologies that don’t perform as well as the market demands. One of these weak links has been indium tin oxide (ITO), which is used in displays and photovoltaics.

ITO has great electrical conductivity and optical transparency, which are both qualities that graphene possesses. But ITO has a weakness too; the indium used to make it is scarce and getting costlier because of that supply pinch.

As a result, graphene has been proposed and researched as a potential replacement for ITO in transparent conductor applications in both displays and photovoltaics. In fact, ITO replacement has been one of the few avenues pursued for applying graphene to photovoltaics. But that has been changing the last couple of years.

Last year, researchers at the Barcelona, Spain-based Institute of Photonic Science (ICFO), in collaboration with the Massachusetts Institute of Technology, Max Planck Institute for Polymer Research in Germany and Graphenea S.L. Donostia-in San Sebastian, Spain used graphene in the conversion and the conduction layers of a solar cell.

Following that application focus for graphene, researchers at the University of Cincinnati are finding that adding a small amount of graphene flakes to polymer-blend bulk-heterojunction (BHJ) solar cells increases energy conversion efficiency of the cells significantly. 

While the researchers have not disclosed what those higher conversion efficiency numbers are, we do know that one of the highest reported conversion efficiencies for a polymer solar cell was as high as 10.6 percent for cells with more than one p-n junction.  And those with a single junction have reached nearly 9 percent, with the expectation that they could exceed 10 percent in commercial products.

Whether the higher conversion efficiencies achieved by the Cincinnati researcher is enough to over come the fact that polymer solar cells can’t survive outside as long as the silicon variety remains to be seen.