Graphene, a one-atom-thick sheet of carbon that is extremely strong and conducts electricity well, is the thinnest material ever made. Researchers believe that it could be used as a transparent electrode in photovoltaic cells, replacing a layer of indium tin oxide (ITO) that is brittle and becoming increasingly expensive.
Wee Shing Koh of the A*STAR Institute of High Performance Computing in Singapore and co-workers have compared these two materials. They found that graphene outperforms ITO when used with solar cells that absorb a broad spectrum of light.
The wavelengths of light from the Sun have a range of intensities and deliver varying amounts of power. To maximize a photovoltaic device’s performance, its transparent electrode should have a low electrical resistance, while also transmitting light of the right wavelengths for the cells to absorb.