Improved Efficiency of over 10% in Dye-Sensitized Solar Cells with a Ruthenium Complex and an Organic Dye Heterogeneously Positioning on a Single TiO2 Electrode

A ruthenium complex (JK-142) with an ancillary bipyridyl ligand substituted by a 3 carbazole-2-thiophenyl moiety was synthesized and explored as a sensitizer in cosensitized solar cells in combination with an organic dye (JK-62). The extended pi-conjugation in the ancillary ligand enables the JK-142 dye to have a red-shift light-absorption band; however, the ineffective penetration of JK-142 molecules into the inner surface of TiO2 film results in low photovoltaic performance for the single dye sensitized solar cell due to its large molecular size of JK-142. Interestingly, when the deficient JK-142 electrode was employed to assemble a cosensitized solar cell by additionally adsorbing JK-62 dye, a considerably improved efficiency of up to 10.2% was achieved, which is favorably superior to that (ca. 8.68%) of N719 in the same device configurations. The results shown here not only provide new vision on how to produce highly efficient solar cells using dyes with extended molecular structure but also open up a new way to position different dyes on a single TiO2 film for cosensitization through controlling the molecule size.