β−Functionalized Push-Pull Opp-Dibenzoporphyrins as Sensitizers for Dye-Sensitized Solar Cells

A novel class of β-functionalized push-pull zinc opp-dibenzoporphyrins were designed, synthesized and utilized as sensitizers for dye-sensitized solar cells. Spectral, electrochemical and computational studies were systematically performed to evaluate their spectral coverage, redox behavior and electronic structures. These porphyrins displayed much broader spectral coverage and more facile oxidation upon extension of π−conjugation. Free-energy calculations and femtosecond transient absorption studies (charge injection rate in the range of 1011 s-1) suggest efficient charge injection from the excited singlet state of porphyrin to the conduction band of the TiO2. The PCE of YH3 bearing acrylic acid linkers (η = 5.9%) is close to that of the best ruthenium dye N719 (η = 7.4%) under similar conditions. The superior photovoltaic performance of YH3 is attributed to its higher light harvesting ability and its more favorable electron injection and collection as supported by electrochemical impedance spectral studies. This work demonstrates the exceptional potentials of benzoporphyrins as sensitizers for dye-sensitized solar cells.