A New Heteroleptic Ruthenium Sensitizer for Transparent Dye-Sensitized Solar Cells

A new heteroleptic ruthenium complex, coded CYC-B19, incorporating an ancillary ligand endowed with hexylthio-bithiophene segments and a conjugated anchoring ligand with vinyl groups was prepared. This new sensitizer exhibits a lower energy MLCT band centred at 562 nm with a remarkably high molar absorption coefficient of 2.97 x 104 M-1 cm-1. DFT-TDDFT theoretical calculation revealed that insertion a vinyl group in the anchoring ligand pushes the LUMO electron locating more on the anchoring ligand. This will benefit the electron transfer from dye to TiO2 when the dye molecules were excited by light. Physicochemical measurements and the optimization of electrolyte were done to investigate the potential of CYC-B19 in TiO2 scattering-layer free dye-sensitized solar cells. Not only is a good photovoltaic efficiency of 8.4% reached, but the transparent device sensitized by CYC-B19 also presents a superior spectral response to its predecessor CYC-B11.