This research has been published online in the journal Nature Physics.
Graphene is a chemical substance that is composed of carbon atoms arranged in a regular hexagonal pattern. This arrangement is one atom thick. It is very light substance with a weight of only 0.77 milligrams for 1 square-meter.
Researchers showed that graphene has the ability to convert a single photon, which is absorbed by it, into multiple electrons that can drive electrical current.
According to researchers, this finding could potentially be used in light harvesting technologies, which are using usual semiconductors like silicon, for are using light to produce electricity.
“In most materials, one absorbed photon generates one electron, but in the case of graphene, we have seen that one absorbed photon is able to produce many excited electrons, and therefore a greater electrical current” Frank Koppens, group leader at ICFO, explained.
“We have seen that high energy photons (e.g. violet) are converted into a larger number of excited electrons than low energy photons (e.g. infrared). The linear scaling of the number of generated excited electrons with photon energy shows that graphene converts light into electricity with very high efficiency. Even though it was already speculated that graphene holds potential for solar cells, it now turns out that it is even more suitable than expected!” explains Tielrooij, one of the corresponding authors of the study.
“It was known that graphene is able to absorb a very large spectrum of light colors. However now we know that once the material has absorbed light, the energy conversion efficiency is very high. Our next challenge will be to find ways of extracting the electrical current and enhance the absorption of graphene. Then we will be able to design graphene devices that generate highly efficient solar power.” Koppens concluded.
K. J. Tielrooij, J. C. W. Song, S. A. Jensen, A. Centeno, A. Pesquera, A. Zurutuza Elorza, M. Bonn, L. S. Levitov, F. H. L. Koppens, (2013). Photoexcitation cascade and multiple hot-carrier generation in graphene. Nature Physics, doi: 10.1038/nphys2564