Organic photosensitizers with catechol groups for dye-sensitized photovoltaics

We have carried out a study on a number of organic dyes to identify photosensitizers for dye-sensitized photovoltaic applications with well matched redox potentials and good absorption characteristics. Triphenylmethyne, anthraquinone and xanthene dyes with catechol groups were chosen as the most promising dyes for fabrication of nanocrystalline TiO2 based dye-sensitized photovoltaic (DSPV) cells using a liquid electrolyte. From our study, a xanthene dye, 9-phenyl-2,3,7-trihydroxy-6-fluorone is found to be efficient photosensitizer in DSPV cells compared to other dyes when a liquid electrolyte is used. Redox potentials, absorption and photovoltaic properties of these dyes are presented. Two possible ways of electron transfer, namely direct charge transfer via formation of strong charge transfer complexes and the conventional excited state electron injection through the HOMO–LUMO energy level matching are discussed.