Oligophenylenevinylene-Functionalized Ru(II)-bipyridine Sensitizers for Efficient Dye-Sensitized Nanocrystalline TiO₂ Solar Cells

New 4- and 4,4‘-oligophenylenevinylene-functionalized Ru(II)-bipyridine sensitizers were synthesized and used in dye-sensitized TiO 2 solar cells (DSSCs) to study their sensitizing properties relative to those of the usual N3 dye. Among those studied, two sensitizers, denoted as D5 and D6, have rendered considerably higher photocurrents and efficiencies for their cells, compared to those of a cell using the conventional N3 dye. The short-circuit photocurrent densities for N3, D5, and D6 are 9.8, 10.8, and 11.7 mA/cm 2, and the efficiencies are 4.1, 4.6, and 4.8%, respectively. The enhanced photocurrents are correlated with the increased molar absorption coefficients of the D5 and D6 dyes over the entire visible spectra region, relative to those of the N3 dye. Corresponding enhancements in IPCE values are attributed to the oligophenylenevinylene groups of D5 and D6 that consist of conjugated double bonds. Analysis of the absorption spectra of the sensitizer-coated TiO 2 films and the desorbed dyes in an aqueous KOH solution indicates that D5 and D6 adhere more strongly to TiO 2 particles than the N3 dye, which is beneficial from the viewpoint of the long-term stability of the DSSCs.