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Abstract
Three new ruthenium complexes (CYC-P1, CYC-P2, and CYC-B1)
with the general chemical formula of [Ru(dcbpy)(L)(NCS)2] where dcbpy
is 4,4’-dicarboxylic acid-2,2’-bipyridine and L is 3,8-bis-(4-octyl-thiophen-
2-yl)-1,10-phenanthroline, 3,8-bis(4-octyl-5-(4-octyl-thiophen-2-
yl)- thiophen-2-yl)-1,10-phenanthroline, or 4,4’-bis- (4’-octyl-bithiophen-
2-yl)-2,2’-bipyridine were prepared and well characterized. The
performance of these dye-sensitized solar cells was also explored. These
complexes were synthesized via the typical one-pot synthesis and
identified with NMR, IR and Mass spectroscopy. In addition, the
localizations of HOMOs and LUMOs of these Ru-complexes were
calculated with the semi-empirical computation (ZINDO/1) in order to
understand the effects of the frontier orbitals on the light harvesting
capability of the photosensitizers. It was found that the difference in light
harvesting ability between CYC-P1, CYC-P2 and CYC-B1 is associated
mainly with the location of the frontier orbitals, especially the HOMO.
Increasing the conjugation length of the ancillary ligand decreases the
energy of the MLCT (metal-to-ligand charge transfer) transition but at the
same time reduces the molar absorption coefficient, due to the HOMO
located partially on the ancillary ligand, of the ruthenium complex. The
molar absorption coefficient of lower-energy MLCT band of CYC-B1 is
very high: higher than all of the reported Ru complexes used in DSSCs.
Therefore, the highest short-circuit current density (23.92 mA/cm2) for
CYC-B1-sensitized solar cell was achieved. Under the illumination of
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AM1.5 stimulated light, the photon-to-current conversion efficiency of
CYC-P1, CYC-P2 and CYC-B1 sensitized cells was 6.01 %, 3.42 % ,
and 8.54 % respectively. Under the same device fabrication and
measuring procedures, the short-circuit current density and conversion
efficiency of N3-sensitized cell were 21.32 mA/cm2 and 7.7 %
respectively. | en_US |