β-Functionalized Push-Pull Opp-Dibenzoporphyrins as Sensitizers for Dye-Sensitized Solar Cells: The Push Group Effect

β-Functionalized push-pull zinc opp-dibenzoporphyrins were designed and synthesized as sensitizers for dye-sensitized solar cells. The utilization of arylamine to replace aliphatic amine as the donor groups has been proved to be an effective strategy to solve the solar cell instability reported previously. Three different arylamino groups including carbazole (YH8), diphenylamine (YH9) and phenothiazine (YH10) were investigated as the arylamine donor groups, and different electronic effects were observed for these donor groups. Diphenylamine carrying YH9 and phenothiazine carrying YH10 displayed strong push-pull characteristics including segregated HOMO/LUMO and red-shifted and broadened absorption bands. In sharp contrast, the incorporation of carbazole (YH8) cancels out the push-pull effect. YH9 and YH10 solar cells achieved high PCE of 6.9% and 7.5% respectively, which are comparable to that of the best ruthenium dye, N719 (η= 7.7%), under similar conditions. This work demonstrates the great potentials of π-extended porphyrins as sensitizers for dye-sensitized solar cells.