New materials take the heat

From Boston, at a meeting of the Materials Research Society

Silicon is the workhorse material for solar cells, but some researchers have been developing inorganic nanoparticles combined with dye molecules as a potentially cheaper alternative. However, high temperatures and prolonged exposure to light can wreck these materials, making them impractical for outdoor applications such as solar panels. A research group led by Michael Grätzel at the Swiss Federal Institute of Technology in Lausanne claims it has found a way to stabilize these dye-sensitized materials.

In the new scheme, the solar cell consists of a pair of electrodes sandwiching a thin film of titanium oxide nanoparticles bound to dye molecules, all surrounded by a polymer gel. When light shines on the solar cell, the dye molecules absorb the light and transfer electrons to the titanium particles. The particles carry the electrons to one of the electrodes, generating a current. Ions in the polymer gel replenish the dye molecules with electrons.

To prevent the dye molecules from detaching from the titanium particles–a major cause of instability–the researchers chemically modified the dyes to make them more hydrophobic. This reduced the dye molecules’ solubility in the polymer gel, preventing them from removing themselves from the metal particles.

In stability tests, the new solar cell proved just as hardy as standard silicon solar cells. Grätzel says that this development could foster the widespread deployment of lower-cost solar cells.


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