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 the π conjugation. Free-energy calculations and femtosecond transient absorption studies (charge injection rate in the range of 1011  s-1 ) suggested efficient charge injection from the excited singlet state of the porphyrin to the conduction band of TiO2 . The power conversion efficiency (η) of YH3 bearing acrylic acid linkers (η=5.9 %) was close to that of the best ruthenium dye N719 (η=7.4 %) under similar conditions. The superior photovoltaic performance of YH3 was attributed to its higher light-harvesting ability and more favorable electron injection and collection, as supported by electrochemical impedance spectral studies. This work demonstrates the exceptional potential of benzoporphyrins as sensitizers for dye-sensitized solar cells.