Dye-sensitized solar cells could offer a cheap alternative to conventional silicon devices, but are often hamstrung by the price of ruthenium, a component in their dye, and problems with the electron carriers used to complete the electrical circuit.

Michael Grätzel at the Swiss Federal Institute of Technology Lausanne (EPFL) and his colleagues report improvements in both these areas. They used a zinc-porphyrin dye called YD2-o-C8 to avoid the need for ruthenium. And, to overcome the voltage limit inherent in traditional electron carriers, they paired this dye with a cobalt polypyridyl electrolyte. The authors' system can generate about 1 volt and has an impressive efficiency of 12.3%.

Science 334, 629–634 (2011)