Coumarin 343-NiO films as nanostructured photocathodes in dye-sensitized solar cells: Ultrafast electron transfer, effect of the i3/I - redox couple and mechanism of photocurrent generation

Ana Morandeira, Gerrit Boschloo, Anders Hagfeldt, Leif Hammarström

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Nanoporous, p-type NiO films were sensitized with coumarin 343 (C343), and the photoinduced electron transfer dynamics was studied in the presence of different concentrations of electrolyte (I3-/I- in propylene carbonate). Electron transfer from the valence band of NiO to the excited C343 is very fast, occurring on time scales from hundreds of femtoseconds to a few picoseconds, but also the subsequent recombination is quite rapid, on the time scale of tens of picoseconds. Nevertheless, formation of an intermediate, attributed to I2 -I NiO(+), was observed on the picosecond time scale. Simultaneously the reduced dye was converted back to the C343 ground state, indicating that recombination could be intercepted by I3 - reduction. Consistent with that interpretation, we observed oxidized NiO and depletion of I3 - persisting on the millisecond time scale. Complete dye-sensitized solar cells (DSSCs) with these films as photocathode gave up to 10-11% incident photon to current conversion efficiency at the C343 visible absorption maximum, which is the highest value reported for a p-type DSSC. Our results elucidate the main mechanism for photocurrent generation in this p-type DSSC, which is important for the understanding and development of these rarely studied counterpart of conventional n-type "Grätzel cells".

Original languageEnglish
Pages (from-to)9530-9537
Number of pages8
JournalJournal of Physical Chemistry C
Issue number25
Publication statusPublished - Jun 26 2008


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

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