TY - JOUR
T1 - Coumarin 343-NiO films as nanostructured photocathodes in dye-sensitized solar cells
T2 - Ultrafast electron transfer, effect of the i3/I - redox couple and mechanism of photocurrent generation
AU - Morandeira, Ana
AU - Boschloo, Gerrit
AU - Hagfeldt, Anders
AU - Hammarström, Leif
PY - 2008/6/26
Y1 - 2008/6/26
N2 - 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".
AB - 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".
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U2 - 10.1021/jp800760q
DO - 10.1021/jp800760q
M3 - Article
AN - SCOPUS:47749112881
VL - 112
SP - 9530
EP - 9537
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 25
ER -