Influence of Donor Moiety in Ruthenium Sensitizers on the Properties of Dye-Sensitized Solar Cells
Nguyen et al.
effectively the probability of injected electron capture by
electron acceptor (I3−) in the electrolyte.
4. CONCLUSION
In conclusion, two high molar extinction coefficient
Ruthenium (II) complexes (Rut-A and Rut-B) carrying
diphenylamine and carbazole moieties were synthesized
and characterized. The introduction of carbazole moi-
ety leads to red-shift of MLCT band and lower HOMO
level of Rut-B dye compared to Rut-A. Incorporation of
a substituted carbazole moiety in bipyridine ligand was
demonstrated to be beneficial for retarding the electron
transfer from TiO2 to the oxidized dye or electrolyte and
to enhance the charge transfer efficiency in the excited
state, resulting in improved power conversion efficiency.
Our future work is focused on the introduction of a new
ancillary ligand containing one more substituted carbazole
moiety to bathochromic shift the absorption and to control
the energy levels of ruthenium complex.
Scheme 2. Energy level diagram for Rut-A and Rut-B dyes.
Acknowledgment: This work was supported by the
Korea Science and Engineering Foundation (KOSEF),
Grant No. R11-2007-050-01003-0.
Delivered by Ingenta to: Purdue University Libraries
References and Notes
IP: 91.216.3.191 On: Thu, 09 Jun 2016 10:05:55
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Fig. 4. Electrochemical impedance spectra (Nyquist plot) of DSSCs
based on Rut-A and Rut-B dyes measured under open circuit conditions
and AM 1.5 simulated sunlight illumination (100 mWcm−2ꢆ.
charge transfer resistance is related to the charge recom-
bination rate. The RCT2 value for Rut-B was estimated to
be 76 ohm that is larger than that for Rut-A (49 ohm),
respectively, corresponding reduction in the radius of the
semicircle. This impedance from the Rut-A dye-sensitized
solar cell is evidence that the recombination process is
faster than the Rut-B sensitizer, leading to the lower pho-
tovoltage of Rut-A dye cell. This indicates that incorpora-
tion of the substituted carbazole moiety in Rut-B decreases
Received: 31 October 2008. Accepted: 30 June 2009.
6814
J. Nanosci. Nanotechnol. 10, 6811–6814, 2010