Copper Complexes as Electron Mediators in DSSCs

The fossil fuels depletion puts the challenge to humanity to replace such energy sources with renewable and more ethic ones. The Sun could be considered a practically inexhaustible energy source on Earth whose light could be converted into electric energy exploiting the photovoltaic effect. In this context dye-sensitized solar cells (DSSCs) could be an actual opportunity. This work is focused on copper complexes with 1,10-phenanthroline ligands as possible alternative mediators to the common I3-/I- redox couple which however suffers of some drawbacks. A rational study on the modulation of the electrochemical behavior of these copper complexes was performed in order to obtain useful information for their clever design; different substituents (varying their electronic and steric properties) placed in different positions on the phenanthroline scaffold were considered. Electrolytes containing the copper complexes were tested in dye-sensitized solar cells combining photoelectrochemical studies with fast pulsed laser experiments. The effect of iron polypyridine co-mediators was also considered. As an example we cite the significant performances obtained with the bulky asymmetric substituted bis-(2-mesitil-1,10-phenanthroline) copper hexafluorophosphate complex (see Figure) respect to the “benchmark” bis-neocuproine one.