A survey by the Institute of Photonic Sciences (ICFO) in Barcelona has discovered a new property of graphene: its high efficiency in converting light energy into electrons and therefore into power. This represents a revolution in the photovoltaic energy field. This finding will mean such a revolution in the technology and solar energy field in this century comparable to what the manufacture of plastic meant in the twentieth century.
ICFO, in collaboration with the U.S. Massachusetts Institute of Technology, the Max Planck Institute for Polymer Research of Germany and Graphenea SL of Donostia-San Sebastián, show in the magazine Nature Physics that graphene is able to convert a photon absorbed into multiple electrons that can conduct electrical current. The promising discovery makes graphene, a substance made up of pure carbon, an important alternative to solar energy technology, currently based on conventional semiconductors such as silicon.
Thanks to this discovery, a paradigm shift will be probably experienced with graphene in the coming decades, similar to that happened with the plastic last century. Phones that fold, transparent and flexible solar panels, lightweight computers … may be developeded with graphene. Industries and authorities are convinced of its great potential to revolutionize the global economy. So much so that the European Union has just injected 1,000 million euros for its development.
According to Frank Koppens, leader of the research group at ICFO, in most materials, “an absorbed photon generates a single electron, but in the case of graphene we have seen that an absorbed photon can produce many excited electrons and therefore a greater electrical signal. “This feature makes graphene the ideal material for the construction of any device requiring to convert light into electricity. Specifically, it enables the production of potential solar cells and light detectors that absorb the energy from the sun with much smaller losses.
The experiment has consisted in sending a known number of photons to different energies on a thin layer of graphene. “We have seen that the high-energy photons (eg purple) induce a greater number of excited electrons than the low-energy photons (eg, infrared),” said another researcher. “In both cases the number of photons sent was always equal or higher. This relationship shows that graphene converts light into a highly efficient electricity. Up to now the speculation was that graphene had great potential to convert light into electricity, but now we have seen that it is even better than expected. ”
“Our next challenge is to find ways to extract the electric current and improve graphene absorption. Then we will be able to design graphene devices that detect light more efficiently, leading to more efficient solar cells,” concluded Koppens.