Interaction of tris(4-anisyl)amine mediator in dye-sensitized solar cells

Abstract

The intermolecular interactions of the tris(4-anisyl)amine molecule (TAA) and its cation radical (TAA+) with a donor–π-linkage–acceptor organic dye (LEG4), Ru-polypyridyl dyes (K77, RuC, and RuP), and a Co-polypyridyl mediator ([Co(bpy)3]2+/3+) were investigated by means of density functional theory. Although the interaction sites of TAA with the oxidized dyes vary widely among the four dyes, the atomic charge and spin are transferred completely. This verified that the regeneration of the dyes by the TAA/TAA+ mediator occurs via a one-electron transfer process. The interaction with [Co(bpy)3]2+ revealed that TAA+ can be regenerated by [Co(bpy)3]2+via a single-electron transfer process using the [Co(bpy)3]2+/3+ electrolyte. The TAA+ species at the anchoring groups of the Ru-polypyridyl dyes provide more stable interactions and are closer to the TiO2 surface than those at the donor and ancillary ligands, suggesting the significant recombination of injected electrons in the TiO2 with TAA+ electron acceptors and thus poor dye-sensitized solar cell performance.