Comparison of the performance of dye sensitized solar cells fabricated with ruthenium based dye sensitizers: Di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II) (N719) and tris(bipyridine)ruthenium(II) chloride (Ru-BPY)

Abstract

Two ruthenium-based dyes were used as sensitizers for dye sensitized solar cells: one with anchoring groups – Di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)Ruthenium(II), (N719) – and the other without any anchoring group, Tris(bipyridine)Ruthenium(II) chloride (Ru-BPY) were studied to assess the effect of anchoring groups on the performance of dye sensitized solar cells. N719 dye has carboxyl groups that bind to the surface of mesoporous TiO2 whereas Ru-BPY contains no such anchoring groups capable of binding to the surface of TiO2 nanoparticles. The dyes were characterized using absorption spectroscopy, emission measurements and lifetime measurements. The wavelength of maximum absorption for the N719 was 525 nm but this was blue shifted to 516 nm upon attachment to the titanium dioxide substrate. The wavelength of maximum absorption for the Ru-BPY was 450 nm before and after application of the dye to titanium dioxide indicating that the interaction of the anchoring groups with the TiO2 nanoparticles had an effect on the absorption band of the N719. The N719 dye sensitized solar cell yielded a solar-to-electrical energy conversion efficiency of 1.35%, which was much higher than that of Ru-BPY (0.09%), thus indicating that anchoring groups on dye sensitizers greatly increase the efficiency of dye sensitized solar cell.