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 × 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.