High efficient cyanine dyes used for nanocrystalline TiO₂ electrode sensitization

With the development made by Grätzel et al on solar cell, the studies on dye-sensitized nanocrystalline TiO₂ solar cell have been widely investigated. Here we synthesized four cyanine dyes containing carboxyl group. The absorption spectra and fluorescent spectra of the dyes in solution and in adsorbed state on the surface semiconductor were measured. These dyes have high absorption coefficient (∼10 ⁵M^-1 cm^-1), which is a major factor that affects the conversion efficiency of the solar cell. These cyanine dyes were used to sensitize nanocrystalline TiO₂, and the photoelectrochemical properties of the electrodes sensitized by these cyanine dyes were measured. From the absorption spectra of the electrode it can be seen that these dyes have been efficiently adsorbed on nanocrystalline TiO₂. The maximum IPCE values of dye CY-1, CY-2, CY-3 and CY-4 were 42%, 51.8%, 75.9% and 22.2% respectively. The results show that cyanine dye derivatives are promising sensitizers for nanocrystalline solar cell.