title: A Computational and Experimental Study of Thieno[3,4-b]thiophene as a Proaromatic π-Bridge in Dye-Sensitized Solar Cells.
abstract: Four D-π-A dyes (D=donor, A=accpetor) based on a 3,4-thienothiophene π-bridge were synthesized for use in dye-sensitized solar cells (DSCs). The proaromatic building block 3,4-thienothiophene is incorporated to stabilize dye excited-state oxidation potentials. This lowering of the excited-state energy levels allows for deeper absorption into the NIR region with relatively low molecular weight dyes. The influence of proaromatic functionality is probed through a computational analysis of optimized bond lengths and nucleus independent chemical shifts (NICS) for both the ground- and excited- states. To avoid a necessary lowering of the TiO2 semiconductor conduction band (CB) to promote efficient dye-TiO2 electron injection, strong donor functionalities based on triaryl- and diarylamines are employed in the dye designs to raise both the ground- and excited-state oxidation potentials of the dyes. Solubility, aggregation, and TiO2 surface protection are addressed by examining an ethylhexyl alkyl chain in comparison to a simple ethyl chain on the 3,4-thienothiophene bridge. Power conversion efficiencies of up to 7.8 % are observed.
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677 (USA).
authors.forename: Phillip
authors.initials: P
authors.lastname: Brogdon
authors.affiliation: Laboratory for Photonics and Interfaces, Swiss Federal Institute of Technology, 1015 Lausanne (Switzerland).
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Giordano
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677 (USA).
authors.forename: George A
authors.initials: GA
authors.lastname: Puneky
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677 (USA).
authors.forename: Amala
authors.initials: A
authors.lastname: Dass
authors.affiliation: Laboratory for Photonics and Interfaces, Swiss Federal Institute of Technology, 1015 Lausanne (Switzerland).
authors.forename: Shaik M
authors.initials: SM
authors.lastname: Zakeeruddin
authors.affiliation: Laboratory for Photonics and Interfaces, Swiss Federal Institute of Technology, 1015 Lausanne (Switzerland).
authors.forename: Mohammad Khaja
authors.initials: MK
authors.lastname: Nazeeruddin
authors.affiliation: Laboratory for Photonics and Interfaces, Swiss Federal Institute of Technology, 1015 Lausanne (Switzerland).
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677 (USA).
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Tschumper
authors.affiliation: Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677 (USA). delcamp@olemiss.edu.
authors.forename: Jared H
authors.initials: JH
authors.lastname: Delcamp
keywords: NICS; dye-sensitized solar cells; proaromaticity; solvatochromism; thienothiophene