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N-Aryl stilbazolium dyes as sensitizers for solar cells

By Octavia A. Blackburn, Benjamin J. Coe, Valentine Hahn, Madeleine Helliwell, James Raftery, Yien T. Ta, Laurence M. Peter, Hongxia Wang, Juan A. Anta and Elena Guillén

Abstract

Eight new N-arylstilbazolium chromophores with electron donating –NR2 (R = Me or Ph) substituents have been synthesized via Knoevenagel condensations and isolated as their PF6− salts. These compounds have been characterized by using various techniques including 1H NMR and IR spectroscopies and electrospray mass spectrometry. UV–vis absorption spectra recorded in acetonitrile are dominated by intense, low energy π → π* intramolecular charge-transfer (ICT) bands, and replacing Me with Ph increases the ICT energies. Cyclic voltammetric studies show irreversible reduction processes, together with oxidation waves that are irreversible for R = Me, but reversible for R = Ph. Single crystal X-ray structures have been determined for three of the methyl ester-substituted stilbazolium salts and for the Cl− salts of their picolinium precursors. Time-dependent density functional theory calculations afford reasonable predictions of ICT energies, but greater rigour is necessary for –NPh2 derivatives. The four new acid-functionalized dyes give moderate sensitization efficiencies (ca. 0.2%) when using TiO2-based photoanodes, with relatively higher values for R = Ph vs Me, while larger efficiencies (up to 0.8%) are achieved with ZnO substrates

Topics: Stilbazolium salts; Dye sensitizers; Solar cells; UV-visible absorption spectroscopy; Electrochemistry; Density functional theory
Publisher: Elsevier
Year: 2012
DOI identifier: 10.1016/j.dyepig.2011.06.017
OAI identifier: oai:eprints.qut.edu.au:46442

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