New ruthenium sensitizers featuring bulky ancillary ligands combined with a dual functioned coadsorbent for high efficiency dye-sensitized solar cells.

Two ruthenium complexes featuring bulky ancillary ligands, XS48 and XS49, were synthesized and studied as dyes in dye-sensitized solar cells (DSCs). Both dyes exhibit higher solar-to-electrical energy conversion efficiency when compared to a commonly used N3 sensitizer under the same conditions. To examine the influence of the bulky ancillary ligands and alleviate the electron recombination in cells, we have developed a dual functioned truxene-based coadsorbent (MXD1) as an alternative candidate to chenodeoxycholic acid (CDCA). This coadsorbent not only effectively shields the back electron transfer from the TiO(2) to I(3)(-) ions but also enhances the light harvesting ability in the short wavelength regions. The photovoltaic performance of XS48-sensitized DSC was independent of the coadsorbents, while XS49 with large bulky ancillary ligand presented better performance when coadsorbent was employed. Interestingly, the simultaneous adsorption-to-sequential adsorption of XS48/49 and MXD1 has caused a notably improved photovoltage, which can be primarily ascribed to the enhanced dye adsorption and retardation of charge recombination. These results not only provide a new vision on how ancillary ligands affect the performance of ruthenium complexes but also open up a new way to achieve further efficiency enhancement of ruthenium complexes.