Synthesis of β,β′-edge fused, π-extended porphyrins and their applications in the dye-sensitized solar cells

Four π-extended, β,β′ aromatic ring fused porphyrins including mono- and opp-dibenzoporphyrins bearing two carboxyl groups at only one fused benzo group were synthesized. The optical results by UV-vis spectroscopy indicate that when compared with the absorption spectra of monobenzoporphyrins, greater light-harvesting capabilities can be realized for opp-dibenzoporphyrins with two benzo group at the opposite β,β′ positions of the porphyrin. The photovoltaic properties of these π-extended porphyrins were examined for the first time and the highest conversion efficiency of 1.62% was realized for opp-dibenzoporphyrin 8a-sensitized solar cell, which is ∼60% higher than that of monobenzoporphyrin 4a based solar cell indicating the effect of an extra aromatic π conjugation on the light-harvesting capabilities of π-extended porphyrins. Subsequent DFT calculation results supported our results obtained in the optical and photovoltaic studies.