Chemically treated graphene has upped the material's solar power conversion efficiency from 2.9 percent to a record-breaking 8.6 percent. Researchers at the University of Florida have taken graphene, a single-atom-thick lattice of carbon atoms, and doped it with trifluoromethanesulfonyl-amide (TFSA). The result was a near quadrupling of efficiency. Unlike previously tried doping agents, TFSA is a stable compound, so its effects are longer lasting. The dopant also improves the electrical properties of the graphene, allowing it to be better at converting sunlight into electricity. When a graphene film is applied to a silicon wafer, it creates a Schottky junction, which occurs when a metal interfaces with a semiconductor material. The UF researchers discovered last year that graphene (a semi-metal) is a good substitute for standard metals. When light is shone onto the junction, electrons are forced to move one way, creating a zone that converts solar power to electricity. “Graphene, unlike conventional metals, is transparent and flexible, so it has great potential to be an important component in the kind of solar cells we hope to see incorporated into building exteriors and other materials in the future,” said Arthur Hebard, professor of physics at UF. “Showing that its power-converting capabilities can be enhanced by such a simple, inexpensive treatment bodes well for its future.” Although some gallium-arsenide semiconductor solar cells have reached efficiencies of 43 percent, the researchers believe that if their cheaper, easier-to-produce graphene solar cells could reach an efficiency of 10 percent, they would be a commercial contender. The results have been published in the current online edition of Nano Letters. For more information, visit: www.ufl.edu
Photosensitizers