This document summarizes research on synthesizing and testing a new cis-like symmetrical squaraine dye as a potential sensitizer for dye-sensitized solar cells. The synthesized squaraine molecule has absorption bands in the high-energy visible light region and reversible redox behavior that could improve photovoltaic performance. Testing of the dye's electrochemical and optical properties showed a red-shifted absorption and energy levels that may positively impact solar cell efficiency compared to other squaraine dyes. Future work will involve incorporating the dye into solar cells to evaluate its photovoltaic response.

1. Cis Vs. Trans: Squaraine Molecules as Potential Sensitizers for Dye Sensitized Solar Cells
NSF Science and Technology Center on Materials and Devices for Information Technology Research No. DMR 0120967
NSF Research Experiences for Undergraduates Program Hooked on Photonics No. CHE 0851730
www.hookedonphotonics.org
Daniel Morales Salazar, Iryna Davydenko, and Seth Marder
Conclusions/Future work
References
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Acknowledgments
Dr. Iryna Davydenko
Dr. Seth Marder
Dr. Denise Bale
Janos Simon (HPLC, and UV-Vis-NIR spectrometer training)
Georgia Tech, NSF (CHE-1156598), CMDITR (NSF DMR-
0120967)
Abstract
To investigate the relationship between structural
conformation and photovoltaic response of
symmetrical squaraine dyes, we have incorporated an
electron-withdrawing dicyanovinyl group on the
squaric acid core. The functionalized squaraine
molecule is locked in a cis-like geometry, and presents
absorption bands in the high-energy area of the visible-
light region, which could result in panchromatic
sensitization. Herein, we report the synthesis,
electrochemical, electronic and optical properties of a
squaraine sensitizer.
Georgia Institute of Technology, Department of Chemistry and Biochemistry, 901 Atlantic Drive, Atlanta, GA 30332, U.S.A.
danielsalazar@gatech.edu
Squaraine Dyes
 Large absorption
coefficients in red to
NIR region. Can be
used as NIR
cosensitizers unless
panchromatic response
is achieved.
Cis vs. Trans
 Can a cis-like
symmetrical squaraine
outperform the
efficiency of
asymmetrical
squaraines?
Synthetic Route of Sensitizer
Photophysical and Computational Studies
Dye λmax
(nm)
CHCl3
ε
(M-1 cm-1)
E0-0
(eV)
YR6 671 275,000 1.76
DMS-II-22 698 210,000 1.70
DMS-II-33 733 230,000 1.62
Electrochemical Properties
Dye E0-0
(eV)
Eox
(V)
Eox - E0-0
(V)
YR6 1.76 0.80 -0.96
DMS-II-22 1.70 0.87 -0.83
DMS-II-33 1.62 0.85 -0.77
 Measured in 0.1M nBu4NPF6 in DCM solution with
decamethylferrocene as an internal standard. Tabulated values
are reported versus NHE. First oxidation potential
corresponds to HOMO level of dye.
 DFT calculations of DMS-II-44 with the B3LYP functional and 6-31G** basis set using Spartan.
 The absorption and electrochemical
properties of the synthesized
intermediates and DMS-II-44 show a
red-shift of absorption maxima into
the NIR region, intense absorption
bands in the high-energy region, as
well as reversible redox behavior,
which may all positively influence the
photovoltaic response of a sensitizer in
a dye-sensitized solar cell .
MSQ, η=2.2%, λmax 642nm (CHCl3)
SQM1a, η=3.6%, λmax 705 nm (CHCl3)
YR6, η=6.74%, λmax 671nm (CHCl3)
HOMO LUMO
Eox
Introduction
Dye-Sensitized solar cells
 Low-cost, flexible, colorful, efficient (15%).
Basic Functioning
 Photon excites an
electron. Excited
electron is injected
in the TiO2 CB.
 Oxidized sensitizer
is regenerated by
an electrolyte.
Electrolyte is
reduced at the
cathode, closing the
circuit.