Programm Photovoltaik Ausgabe 2009 ... - Bundesamt für Energie BFE

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small and big particles that composes the DSL 18NR-AO paste as a main result of an increase in the
fill factor. From an optical point of view, we have demonstrated that the use of DSL 30NRD-T + DSL
18NR-AO allows preventing light loss within the photo-anode as a consequence from tangent light
scattering [6].
Efficiency (%)
11
10.5
10
9.5
9
0.5 sun
1sun
0.1 sun
10.19
10.00
9.81
10.57
10.43
10.32
10.49
10.35
10.01
10.79
10.74
10.61
10.63
10.44
10.30
9.93
9.68
9.50
EPFL/CCIC EPFL/AO 18NR-T/AO 30NRD/AO Trans/AO AO
Figure 1: Evolution of the conversion efficiency under different incident light intensity as a function of
the different paste studied. (note that spot electrodes of ca. 0.283cm² were herein used and masked
with an aperture of 0.159cm²).
2) Optimization of the photo-voltaic characteristic of C101 dye
The optimization of the photo-anode configuration obtained in accordance with the photo-physical
properties of the C101 dye, we investigated a way to improve the monolayer characteristics. Pressure
and temperature of sensitization are two parameters that govern the adsorption equilibria constant as
well as the kinetic of adsorption. In the term of this first year project, we evaluated the influence of the
temperature of sensitization of the C101 dye at three different temperatures: 60°C, 20°C and 4°C.
Figure 2 shows the evolution of the photo-voltage, photo-current density, fill factor and photon-toelectron
conversion efficiency as a function of the temperature which the cell has been sensitized.
The temperature drastically influences the dye photovoltaic performance. Interestingly, the Voc of the
cell can be tuned linearly from 714 mV, 752 mV to 768 mV in respect to a gradual temperature decrease
from 60°C, 20°C to 4°C, respectively. This comes in turn with a remarkable improvement of
the fill factor from 0.708 to 0.725 while the short circuit current density of the cells slightly increases
from 19.9 mA/cm² to 20.5 mA/cm². A similar tendency was also experienced at lower incident light
intensity, although the gap between the values becomes narrower. As a result from the increase of
the three cell characteristics, the low temperature sensitization approach affords a noteworthy enhancement
in the photon-to-electron conversion efficiency from 10.1 %, 10.9 % to 11.5 %.
Photo-voltage (mV)
770
760
750
740
730
720
710
0 10 20 30 40 50 60
Grafting temperature (°C)
21
20.5
20
19.5
19
Photo-current Photo-current density (mA/cm²)
Fill Factor
0.73
0.725
0.72
0.715
0.71
0.705
0 10 20 30 40 50 60
Grafting temperature (°C)
Fig. 2: Evolution of the cell characteristics (Voc, Jsc, F.F. and �) as a function of the grafting temperature
at 1 sun equivalent light intensity (A.M. 1.5G). The values indicated correspond to an average
value obtained by repetition of the cells. Square cells dimension were 0.152 cm² and masked with an
aperture 1mm larger than the photo-anode.
Robust DSC, M. Graetzel, EPFL
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12
11.5
11
10.5
10
9.5
Conversion efficiency (%)