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Keywords:

  • anchoring stability;
  • density functional calculations;
  • dyes/pigments;
  • dye-sensitized solar cells;
  • pyridine-N-oxides

Abstract

A D-π-A organic dye carrying a pyridine-N-oxide 2-carboxylic acid anchoring group (BC1) was synthesized together with two analogs lacking the N-oxide (BC2) or the carboxylic acid moiety (BC3). The distribution and energy of their molecular orbitals was determined, and modelling of their spectroscopic properties was performed through a TD-DFT computational study. The photo- and electrochemical properties of the dyes were assessed together with their desorption kinetics from nanocrystalline TiO2. In solution, the absorption spectra of dyes BC1 and BC3 were red-shifted compared with BC2, with the maximum absorption wavelength influenced by the dye protonation level. The 2-substituted carbonitrile dye BC3 was not adsorbed on the titania surface. On the other hand, the pseudo-first order desorption rate constants of BC1 and BC2 suggest that BC1 was removed from TiO2 more slowly than BC2 a reference cyanoacrylate dye, demonstrating that simultaneous use of the N-oxide and the carboxylic acid anchoring functions enhanced the stability of the dye/semiconductor assembly. When used as a photosensitizer for dye-sensitized solar cells, the photovoltaic performance of BC1 was better than BC2, which corresponds to approx. 66 % of that recorded with the reference dye.