Burt, Ethan
Fridblom, Travis
Synthesis and Properties of Organic Dye-Sensitizer FNE29
Ethan Burt and Travis Fridblom
Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65201
Email: eebm7f@mail.missouri.edu; tlfxtd@mail.missouri.edu
1
Burt, Ethan
Fridblom, Travis
Introduction
Currently, the most common way to convert solar power into a useable form of energy is
through the use of solar cells. In general, theses solar cells traditionally come as one or a
combination of several different varieties. These can include but are not limited to
semiconducting solar cells, organic polymer solar cells, and dye-sensitized solar cells (DSSCs).
Among the different types of solar cells currently being explored for energy production,
DSSCs utilizing an organic dye sensitizing material have been of particular interest. These
nanocrystalline dye-sensitized solar cells are promising synthetic nanomachines whose function
is based on principles similar to the processes in natural photosynthesis. Both use an organic dye
to absorb the incoming light and produce excited electrons.
Discussed here is the development and evaluation of the metal-free organic dye-sensitizer
2-Cyano-3-[5”-(4-(diphenylamino)phenyl-3’,3”,4-tri-n-hexyl-[2,2’,5’,2”]terthiophene]acrylic
acid (FNE29). Several characteristics of FNE29 make it a desirable material for use in DSSCs. It
is relatively easy to synthesize in moderate to high yields from cheaply available starting
materials. It also avoids the health hazards associated with the toxic heavy metals used in many
inorganic dyes. The structures of FNE29, as well as those of two comparison dyes SD2 and D11,
are shown below (Scheme 1).
Scheme 1. Structures of Organic Dye-Sensitizers. A: FNE29; B: SD2; C: D11
2
Burt, Ethan
Fridblom, Travis
In this paper, we measure and compare several of the performance characteristics of FNE29 to
the other organic dye-sensitizers SD2 and D11.
Materials and Methods
The synthetic approach to sensitizer FNE29 starts from the alkyl-functionalized
terthiophene (Scheme 1). The monoaldehyde-substituted derivative was obtained by refluxing in
the presence of a Vilsmeier reagent and the electron donor, triarylamine, was attached via C-H
bond activation. In the last step, FNE29 is obtained via Knoevenagel condensation with
cyanoacetic acid through refluxing acetonitrile with piperidine. A more detailed description of
the synthesis as well as spectroscopic characterization can be found in the supporting
information.1
Scheme 1. Synthetic Outline of Organic Dye-Sensitizer FNE29.
The DSSC was designed containing an electrolyte with 0.6 M 1,2-dimethyl-3propylimidazolium (DMPImI), 0.1 M LiI, 0.05M I2, and 0.5M 4-ter-butylPyridine (TPB) in
acetonitrile. The DSSC was constructed from 14Ω Nippon Fluorine doped SnO2 glass (FTO),
3
Burt, Ethan
Fridblom, Travis
TiO2 films (thickness: 12μm Size: 0.25cm2), and a platinum counter electrode. All of the
components were assembled into a sealed sandwich cell with a thermoplastic frame.
The overall effectiveness of FNE29 and other dye sensitizers can be evaluated based on a
variety of pertinent performance characteristics. FF determines the maximum power output from
a solar cell and high efficiency solar cells often demonstrate FF values of 0.7 or higher. The
molar extinction coefficient is a measurement of how strongly a chemical species absorbs light at
a given wavelength and it’s denoted by the letter ε. Short circuit current density Jsc is the current
through the solar cell when the voltage across the cell is zero. The open circuit voltage Voc is the
maximum voltage available from a solar cell when the current is zero. The incident photon is
labeled Pin and is measured in (mW/cm2). These are all considered especially useful in
determining the overall usefulness of a material in DSSCs. The values for these parameters and
others can be found in the table below (Table 1). The power conversion efficiency is a measure
of the device’s ability to absorb sunlight and convert it into usable energy. This is often
considered the most important aspect of a solar cell’s performance and is solved from a simple
equation relating four of the variables described above.
Jsc(mA cm-2) x Voc(V) x FF
Overall Conversion Efficiency η(%) = ------------------------------------Pin(mW cm-2)
Table 1. Photophysical and Electrochemical Properties of Selected Dye Sensitizers1
Dye
FNE29
SD2
D11
λMax
ε
JSC
VOC
2
FF
HOMO
LUMO
η
(V)
(V)
(%)
(nm)
(M-1cm-1)
(mA/cm )
(mV)
456
3.4x104
14.93
754
0.72
1.07
-0.99
8.12
465
9.1x10
4
14.51
700
0.72
0.42
-0.5
7.26
3.8x10
4
13.5
744
0.7
1.29
-0.98
7.03
458
4
Burt, Ethan
Fridblom, Travis
The current density voltage characterization measurements for the solar cell were taken
with three devices. The first was a Keithly 2400 source meter under illumination from a AM1.5G
simulated light with 1000W Xe lamp. The second device measured the open circuit densities
using the charge extraction technique on a Zahner XPOT (Germany).The last was an Oriel 74125
system with a Si detector Oriel 71640 to measure the Incident photon conversion efficiency
(IPCE) of the cell under different monochromatic light. The relationship is shown in figure 1.
Figure 1. %IPCE vs. Wavelength for FNE29 and Others
Results and Discussion
Conclusions
Supplemental Material Available: A detailed description of the synthesis for the organic dyesensitizer FNE29, as well as the spectroscopic characterization can be found in the appendix.
References
(1) Feng, Q.;Zhou, G.; Wang, Z. Varied Alkyl Chain Functionalized Organic Dyes for Efficient
Dye-Sensitized Solar Cells: Influence of Alkyl Substituent Type on Photovoltaic Properties. J.
Power Sources 2013.
5
Burt, Ethan
Fridblom, Travis
Supporting Information
Synthesis and Properties of Organic Dye-Sensitizer FNE29
Ethan Burt and Travis Fridblom
Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65201
Email: eebm7f@mail.missouri.edu; tlfxtd@mail.missouri.edu
S1
Burt, Ethan
Fridblom, Travis
Table of Contents
Synthesis of FNE29……………………………………………………………………….……S3
1
H NMR Spectra of FNE29………………………………………………………………….…S4
13
C NMR Spectra of FNE29…………………………………………………………………....S5
UV-Vis Spectrum of FNE29…………………………………………………....………………S6
Bibliography……………………………………………………………………………….…….S7
S2
Burt, Ethan
Fridblom, Travis
Synthesis of FNE29
All of the chemicals and reagents used were purchased from commercial sources and all
reactions were done under inert atmosphere using Schlenk techniques. Compound 1a
(1.00g/2.00mmol) and DMF (0.186mL/2.40mmol) were dissolved in 30mL of chloroform. After
dissolved Phosphorous Oxychloride (0.297mL) was added slowly. The mixture was stirred for
20min at room temperature followed by heating to 90°C for 8hrs. After cooling to room
temperature, 30mL saturated sodium acetate solution was added to the dark reaction solution
with stirring for 20min. The mixture was poured into ice water (50mL) and then it was
neutralized through the addition of sodium hydroxide solution. The product was extracted with
DCM three times. The combined organic solution was washed with sodium bicarbonate and
sodium chloride solutions and then dried over anhydrous sodium sulfate. After removal of the
solvent the residue was purified by flash column chromatography through silica SiO2
(solvent;DCM:PE/1:2). Orange oil 2a was obtained with a yield of 46% 486mg. Next, a reaction
vessel filled with K2CO3 (0.69mmol/95mg), Pd(OAc)2 (0.009mmol, 2.0mg),
PCy3∙HBF4(0.018mmol, 7.0mg), pivalic acid (0.138mmol, 14mg), 4-bromo-N,Ndiphenylaniline (298mg, 0.919mmol), and 2a (243mg, 0.459mmol). Then we add dry toluene
(2mL). The reaction mixture was then vigorously stirred at 105°C for 16hr. The solution was
then cooled to room temperature, diluted with CH2Cl2 and H2O. The aqueous phase was
extracted with CH2Cl2. The organics were combined and dried over MgSO4, filtered, and
evaporated under reduced pressure. The crude product was purified by silica gel column
chromatography to yield a red-orange oil 3a in 59% yield (208mg). Finally, to a mixture of 3a
(856mg,1.1mmol), cyanoacetic acid(239mg,2.81mmol), 35mL chloroform and 35mL acetonitrile
0.2mL of piperdine was added. The mixture was refluxed at 120°C for 6hr and allowed to cool to
room temperature. The resulting mixture was washed with DI and brine then dried via MgSO4
and filtered. The solvent was removed by rotary evaporation, and the residue was purified by
column chromatography (DCM:MeOH/10:1) to give a dark brown solid(522mg, 56%).
S3
Burt, Ethan
Fridblom, Travis
1H
NMR Spectra of FNE29
Figure S1. Predicted 1H MNR Spectra of FNE29
S4
Burt, Ethan
Fridblom, Travis
13C
NMR Spectra of FNE29
Figure 2S. Predicted 13C NMR Spectra of FNE29.
S5
Burt, Ethan
Fridblom, Travis
UV-Vis Spectrum of FNE29
Figure 3S. UV-Visible Spectrum of FNE29 and Others.
S6
Burt, Ethan
Fridblom, Travis
Bibliography
Feng, Q.;Zhou, G.; Wang, Z. Varied Alkyl Chain Functionalized Organic Dyes for Efficient
Dye-Sensitized Solar Cells: Influence of Alkyl Substituent Type on Photovoltaic Properties. J.
Power Sources 2013.
Hagberg, D. P.; Yum, J.; Lee, H.; De Angelis, F.; Marinado, T.; Karlsson, K.; Humphry-Baker,
R.; Sun,L.; Hagfeldt, A.; Gratzel, M.; and Nazeeruddin, M. Molecular Engineering of Organic
Sensitizers for Dye-Sensitized Solar Cell Applications. J. Am. Chem. Soc. 2008, 130, 6259-6266.
Shen, P.; Liu, Y.; Huang, X.; Zhao, B.; Xiang, N.; Fei, J.; Liu, L.; Wang, X.; Huang, H.; Tan, S.
Efficient triphenylamines dyes for Solar Cells: Effects of Alkyl Substituents and Pi Conjugated
Thiophene Units. Dyes Pigm. 2009, 83, 187-197.
S7