Dye-Sensitized Solar Cells with Biferrocenyl Antennae Having Quinoxaline Spacers

Four biferrocene-based dyes with quinoxaline spacers possessing functional groups [H (2), Cl (3), NO2 (4) and COOH (5)] were successfully synthesized and characterized by elemental analyses, IR spectroscopy, electronic absorption, H-1 NMR and C-13 NMR spectroscopy, and mass spectrometry. The synthesized dyes as well as the starting diketenone (1), from which quinoxalines 2-5 were synthesized, were exploited as photosensitizers in TiO2-based dye-sensitized solar cells. The spectral responses of dyes 2-5 were extended into the visible region up to = 550 nm. Amongst all the ferrocenyl dyes with a quinoxaline spacer, dyes having Cl (3), NO2 (4), and COOH (5) substituents showed photovoltaic performance that was superior to that of starting material 1 and that of quinoxaline derivative 2. The superior performances of 3, 4, and 5 are probably because of the abilities of these systems to accept high loadings of the dye on the TiO2 surface and the long lifetime of electrons in the TiO2 conduction band. Dye 5 showed better thermal stability than the state-of-art dye N719 and has a comparable lifetime of electrons in the conduction band.