So what’s a one-atom thick layer of carbon atoms got to do with solar? Maybe a lot. New research at the Michigan Technological University discovered that the unconventional material, graphene, was able to boost the efficiency of organic photovoltaics by 50 percent with the wonder material.
The electrical conductivity of graphene, explained MTU Professor Yun Hang Hu, Ph.D., allows it to act as a bridge accelerating electron transfer from the titanium dioxide to the photoelectrode. “The power conversion efficient can be increased from 1.79 percent without graphene to 2.78 percent by mixing graphene. This indicates that graphene can remarkably increase the efficiency of DSSCs,” he said.
Graphene is a unique two-dimensional material that’s electrically conductive. The idea of graphene had been around since 1947. But it took the “Scotch Tape” method—whereby tape is used to peel graphene from graphite—developed by Andre Geim and Kostya Novoselov in 2004 at Manchester University to finally create it. They won the Nobel Prize in Physics in 2010 for the discovery.
Now the team led by Hu is researching the use of graphene as applied to dye-sensitized solar cells (DSSCs) otherwise known as organic photovoltaics. Hu and co-authors Hui Wang, Samantha Leonard presented their research at the US-Egypt Joint Workshop on Solar Energy Systems and submitted “Promoting Effect of Graphene on Dye-Sensitized Solar Cells” to peer-reviewed Industry and Engineering Chemistry Research.
Dye-sensitized PV promises some of the lowest-cost solar power available in the near future, because it can be produced cheaply and easily at room temperatures and uses commonplace materials, like titanium dioxide (think sunscreen). To make the mix at MTU researchers made a paste of graphite oxide powder mixed with titanium dioxide. They spread it on a substrate like and baked it. “The semiconductor film needs to be calcined at 450C. This temperature can be reach by a conventional oven,” Hu said.
Still, it’s not a PV panacea yet. “The power conversion of our DSSCs with graphene is still relatively low. The next step for our research is to optimize the fabrication conditions for a higher power conversion efficient,” Hu said. Boosting those two factors will likely take years.
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