Improved Dye Regeneration through Addition of a Triphenylamine Electron Donor in Iodide-Based Electrolytes for Dye-Sensitized Solar Cells

The addition of a small organic electron donor, tris(p-anisyl)amine (TPAA), to an iodide/triiodide electrolyte for dye-sensitized solar cells was found to give pronounced effects on charge transfer reactions. When using the organic dye LEG4 as a sensitizer, an improved solar cell performance was found, which could be attributed to the extremely rapid dye regeneration reaction when TPAA is added. In contrast, for the ruthenium dye N719, no significant solar cell improvement was found, despite rapid dye regeneration. Using transient absorption measurements, it was found that reduction of the intermediate TPAA+ by iodide is sluggish. This allows for significant recombination of electrons in TiO2 to TPAA+ when the adsorbed dye layer does not have sufficient electron-blocking properties.