Triarylamine-functionalized ruthenium dyes for efficient dye-sensitized solar cells

Triarylamine-functionalized ruthenium dyes, J5, J6, J7, and J9, were designed and synthesized as a dye-sensitizer for novel efficient dye-sensitized solar cells. DFT/TDDFT calculations performed on the four dyes gave useful information of their structural, electronic, and optical properties. These results indicated that the triarylamine ligand acts as an electron donor in a manner similar to thiocyanato ligands and Ru metal, and the TDDFT calculations predicted that the absorption in the visible region originates from electron transfer from the electron donor groups to the anchoring ligand dcbpy, through which excited electrons are directly transferred to TiO₂. Under standard global AM 1.5 solar conditions, the J5, J6, J7, and J9-sensitized solar cells demonstrated overall conversion efficiencies of 5.8, 7.9, 7.8, and 7.1%, respectively. The higher efficiencies of the J6, J7, and J9 dyes compared to that of J5 are mainly explained in terms of the substituted methoxy groups providing directionality in the excited state.