title: Thieno[3,4-b]pyrazine as an Electron Deficient π-Bridge in D-A-π-A DSCs.
abstract: Thieno[3,4-b]pyrazine (TPz) is examined as an electron deficient π-bridge enabling near-infrared (NIR) spectral access in dye-sensitized solar cells (DSCs). Seven dissymmetric dyes for DSCs were synthesized (NL2-NL8) with TPz as the π-bridge utilizing palladium catalyzed C-H activation methodology. C-H bond cross-coupling was uniquely effective among the cross-couplings and electrophilic aromatic substitution reactions analyzed in monofunctionalizing the TPz building block. The TPz-based NL2-NL8 dyes examine the effects of various donors, π-spacers, and acceptors within the donor-π bridge-acceptor (D-π-A) dye design. Proaromatic TPz stabilizes the excited-state oxidation potential (E(s+/s*)) of the dyes by maintaining aromaticity upon excitation of the dye molecule. This leads to concise conjugated systems capable of accessing the NIR region. Through judicious structural modifications, dye band gaps were reduced to 1.48 eV, and power conversion efficiencies (PCEs) reached 7.1% in this first generation TPz-dye series.
authors: Department of Chemistry and Biochemistry, University of Mississippi , University, Mississippi 38677, United States.
authors: Nalaka P
authors: NP
authors: Liyanage
authors: Laboratory of Photonics and Interfaces, Institution of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology , CH-1015, Lausanne, Switzerland.|Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Bombay , Powai, Mumbai 400-076, India.
authors: Aswani
authors: A
authors: Yella
authors: Laboratory of Photonics and Interfaces, Institution of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology , CH-1015, Lausanne, Switzerland.
authors: Mohammad
authors: M
authors: Nazeeruddin
authors: Laboratory of Photonics and Interfaces, Institution of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology , CH-1015, Lausanne, Switzerland.
authors: Michael
authors: M
authors: Grätzel
authors: Department of Chemistry and Biochemistry, University of Mississippi , University, Mississippi 38677, United States.
authors: Jared H
authors: JH
authors: Delcamp
keywords: C—H activation; NIR dyes; dye-sensitized solar cells; panchromatic absorption; proaromaticity; thienopyrazine