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and anchored dyes. Among binding modes, the bidentate mode
achieves high quantum yields of electron injection into a
1
6
semiconductor, as a result, LJ203 exhibited a more efficient
electron injection into TiO compared to LJ201.
2
In summary, we have reported two silicon–porphyrin sensi-
tizers, LJ201 and LJ203, based on axial ligands. The absorption
of LJ203 is red-shifted compared to the classic porphyrin
sensitizer LJ201 while maintaining the energy levels necessary
for efficient electron injection and dye regeneration. In addi-
tion, axial ligands and bulky triphenylamine units in LJ203
suppress the electron recombination at the TiO /dye/electrolyte
2
interface. LJ203-based DSSCs without CDCA as a co-absorbent
exhibited good performance, showing potential application as a
panchromatic sensitizer in solar-electrical conversion devices.
Using axial ligands as anchoring groups to prevent dye aggre-
gation is an effective strategy to prepare efficient porphyrin
sensitizers for DSSC application in the future.
We gratefully acknowledge the financial support of this work
from the China Natural Science Foundation (Grant 21076039,
Grant 21276044, Grant 21120102036 and 20923006), the National
Basic Research Program of China (Grant No. 2009CB220009), the
Swedish Energy Agency, K&A Wallenberg Foundation, and the
State Key Laboratory of Fine Chemicals (KF0805), the Program
for Innovative Research Team of Liaoning Province (Grant
No. LS2010042).
Fig. 3 (a) J–V curves of DSSCs sensitized with LJ201 and LJ203 measured under
the illumination of sunlight AM 1.5 G; (b) IPCE spectra of DSSCs sensitized with
LJ201 and LJ202.
Notes and references
1
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Fig. 4 Nyquist plots of DSSCs sensitized with LJ201 and LJ203 measured at
À0.5 V bias voltage in the dark.
6
7
at the TiO /dye/electrolyte interface can be efficiently suppressed,
2
leading to a higher Voc for DSSCs sensitized with LJ203. From the
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By using the FTIR technique, the study of the interfacial
1
0 B. Lim, G. Y. Margulis, J. Yum, E. L. Unger, B. E. Hardin, M. Gr ¨a tzel,
binding mode of the dyes onto the TiO
determine how the dyes attach to the TiO
LJ203 sodium salts, the frequency difference values (Dnas–s
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2
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(
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À
À1
modes of the COO group were 227 and 235 cm , respectively.
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When the dyes were anchored onto the TiO
2
surface, different
À1
À1
Dnas–s values were obtained, 249 cm for LJ201 and 224 cm
for LJ203 (Fig. S5 and Table S1 in the ESI†). On the basis of the
1
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1
5
Deacon and Philips rule, the unidentate mode for the binding
1
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This journal is c The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 11785--11787 11787