Graphene: Big promise for new solar technologies

A big step in improving the efficiency of photovoltaic cells in on the horizon. A paper published over the weekend in Nature Physics describes the ability of a substance called Graphene to convert a high percentage of the energy from sunlight into electricity. Graphene uses more of each photon's energy, and a wider range of photons of different energy levels (using a broad spectrum of the Sun's energy), compared to existing solar cells. From the abstract of the paper:

The conversion of light into free electron–hole pairs constitutes the key process in the fields of photodetection and photovoltaics. The efficiency of this process depends on the competition of different relaxation pathways and can be greatly enhanced when photoexcited carriers do not lose energy as heat, but instead transfer their excess energy into the production of additional electron–hole pairs through carrier–carrier scattering processes. Here we use optical pump–terahertz probe measurements to probe different pathways contributing to the ultrafast energy relaxation of photoexcited carriers. Our results indicate that carrier–carrier scattering is highly efficient, prevailing over optical-phonon emission in a wide range of photon wavelengths and leading to the production of secondary hot electrons originating from the conduction band. As hot electrons in graphene can drive currents, multiple hot-carrier generation makes graphene a promising material for highly efficient broadband extraction of light energy into electronic degrees of freedom, enabling high-efficiency optoelectronic applications.

Peter Sinclair has summarized the info on Graphene and has links to various sources here.

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. Photoexcitation cascade and multiple hot-carrier generation in graphene. Nature Physics (2013) doi:10.1038/nphys2564. Source

___________________

Photo of solar cells credit: bkusler via Compfight cc

More like this

Last week's Reader Request Thread produced a bunch of good suggestions, some of which I'll be responding to this week as I put the last touches on the book draft and send it off.
I'm on vacation this week, and taking this opportunity to clear out a large backlog of news items that I flagged as interesting, but never got around to commenting on.
There are fewer of them this time, so I'll keep them above the fold.
The 2010 Nobel Prize in Physics goes to Geim and Novoselov for their work on graphene, a material consisting of one-atom-thick sheets of carbon atoms in a hexagonal array.