Chemistry of Materials
Article
2H), 6.86 (t, J = 2.0 Hz, 2H), 3.96 (t, J = 6.8 Hz, 2H), 3.88 (t, J = 6.8
Hz, 2H), 1.77−1.84 (m, 4H), 1.41−1.46 (m, 4H), 1.25−1.39 (m,
12H), 0.85−0.89 (m, 6H). 13C NMR (400 MHz, CDCl3): δ (ppm)
190.01, 158.72, 150.54, 141.88, 131.88, 130.94, 130.16, 130.07, 128.38,
127.55, 127.50, 125.66, 124.00, 123.56, 116.06, 115.94, 114.64, 68.10,
48.07, 36.09, 31.74, 31.63, 29.28, 29.18, 26.85, 26.75, 25.77, 23.99,
22.64, 14.13, 14.09. HRMS (MALDI-TOF, m/z): [M+] calcd for
(C33H41NO2S) 515.2989; found, 515.2977.
130.50, 127.50, 125.71, 125.54, 123.92, 123.37, 116.18, 116.06, 115.16,
114.88, 97.14, 48.21, 31.94, 31.62, 29.63, 29.57, 29.54, 29.37, 29.27,
29.16, 26.83, 26.74, 26.66, 26.56, 25.76, 22.72, 22.64, 14.16, 14.08.
HRMS (MALDI-TOF, m/z): [M+] calcd for (C40H50N2O3S)
638.3536; found, 638.3552.
Characterizations. 1H and 13C NMR spectra were recorded with a
Bruker Ultrashield 400 Plus NMR spectrometer. The UV−visible
absorption spectra of these dyes were measured in CH2Cl2 solution
with a Varian Cary 100 UV−vis spectrophotometer. Emission spectra
were performed using a Photon Technology International (PTI)
Alphascan spectrofluorimeter. High-resolution matrix-assisted laser
desorption/ionization time-of-flight (MALDI-TOF) mass spectra were
obtained with a Bruker Autoflex MALDI-TOF mass spectrometer. The
cyclic voltammograms (CV) were measured with Versastat II
electrochemical workstation using a normal three-electrode cell with
a Pt working electrode, a Pt wire counter electrode, and a Ag/Ag+
reference electrode. The supporting electrolyte was 0.1 M tetra-n-
butylammonium hexafluorophosphate in CH2Cl2 solution. The
potential of the reference electrode was calibrated by ferrocene after
each set of measurements, and all potentials mentioned in the work
were against the normal hydrogen electrode.
4d. 124 mg, 68% yield. 1H NMR (400 MHz, CDCl3): δ (ppm) 9.78
(s, 1H), 7.62−7.64 (m, 1H), 7.58 (d, J = 4.0 Hz, 1H), 7.44 (d, J = 4.0
Hz, 1H), 7.42 (d, J = 4.0 Hz, 1H), 7.31−7.34 (m, 1H), 7.28 (d, J = 4.0
Hz, 1H), 6.92 (t, J = 4.0 Hz, 2H), 6.88 (t, J = 4.0 Hz, 2H), 3.98 (t, J =
6.8 Hz, 2H), 3.89 (t, J = 6.8 Hz, 2H), 1.79−1.87 (m, 4H), 1.45−1.59
(m, 4H), 1.37−1.42 (m, 4H), 1.29−1.35 (m, 16H), 0.85−0.89 (m,
6H). 13C NMR (400 MHz, CDCl3): δ (ppm) 189.99, 158.72, 150.56,
141.89, 136.47, 131.88, 130.94, 130.16, 128.41, 127.50, 125.65, 125.45,
124.56, 124.01, 123.56, 116.06, 114.83, 68.12, 48.08, 31.94, 31.78,
31.65, 31.05, 29.65, 29.54, 29.37, 29.28, 29.22, 26.85, 26.74, 25.77,
22.72, 22.65, 14.17, 14.09. HRMS (MALDI-TOF, m/z): [M+] calcd
for (C37H49NO2S) 571.3588; found, 571.3587.
General Synthetic Procedure for Dyes PT-Cn (n = 2, 6, 8, 12). A
mixture of precursor 4a−4d (0.23 mmol) and cyanoacetic acid (89
mg, 1.10 mmol) in acetic acid (20 mL) was refluxed in the presence of
ammonium acetate (200 mg) overnight under a N2 atmosphere. Then,
water was added and extracted with CH2Cl2. Next, the solvent was
removed under vacuum and the crude compound was purified by
column chromatography on silica gel eluting with CH2Cl2/MeOH
(20:1, v/v) to give PT-Cn as a dark red solid.
Fabrication and Characterization of Cells. To make a
reasonable comparison, all the anode films for the DSSCs were
made under the same standard manner, which are composed of a 12
μm thick of transparent layer (TiO2 with diameter of 20 nm) and 6
μm thick of scattering layer (TiO2 nanoparticles with a diameter of
200 nm). Specifically, a doctor-blade technique was utilized to prepare
photoanode (TiO2) films. First, a layer of ∼6 μm TiO2 paste (20 nm)
was doctor-bladed onto the FTO conducting glass and then relaxed at
room temperature for 3 min before heating at 150 °C for 6 min; this
procedure was repeated once to achieve a film thickness of ∼12 μm
and the resulting surface was finally coated by a scattering layer (∼6
μm) of TiO2 paste (200 nm). The electrodes were gradually heated
under an air flow at 275 °C for 5 min, 325 °C for 5 min, 375 °C for 5
min, and 470 °C for 30 min to remove polymers and generate a three-
dimensional TiO2 nanoparticle network. After that, the sintered films
were soaked with 0.02 M TiF4 aqueous solution for 45 min at 70 °C,
washed with deionized water, and further annealed at 450 °C for 30
min. After cooling down to ∼80 °C, the electrodes were immersed
into a 5 × 10−4 M dye bath in CH2Cl2 solution for the PT-Cn dye
series or in acetonitrile/tert-butyl alcohol (volume ratio, 1:1) for N719
dye and maintained in the dark for 16 h. Afterward, the electrodes
were rinsed with ethanol to remove the nonadsorbed dyes and dried in
the air. Pt counter electrodes were prepared by sputtering method at
15 mA for 90 s at a power of 150 W. Two holes (0.75 mm in
diameter) were predrilled in the FTO glass for introducing the
electrolyte. The dye-adsorbed TiO2 electrode and Pt-counter electrode
were assembled into a sandwich type cell and sealed with a hot-melt
parafilm at about 100 °C. The liquid electrolyte consisting of 0.6 M
1,2-dimethyl-3-propylimidazolium iodide (DMPII), 0.1 M LiI, 0.05 M
I2 in a mixture of acetonitrile and 4-tert-butylpyridine (volume ratio,
1:1) was introduced into the cell through the drilled holes at the back
of the counter electrode. At last, the holes were sealed by parafilm and
covering glass (0.1 mm thickness) at elevated temperature. The
effective areas of all the TiO2 electrodes were 0.24 cm2. The current−
voltage (J−V) characteristics of the assembled DSSCs were measured
by a semiconductor characterization system (Keithley 236) at room
temperature in air under the spectral output from solar simulator
(Newport) using an AM 1.5G filter with a light power of 100 mW/
cm2. IPCEs of DSSCs were recorded in the Solar Cell QE/IPCE
Measurement System (Zolix Solar Cell Scan 100) using dc mode. CHI
660D electrochemical workstation was used to characterize the
electrochemical properties of the DSSCs. Electrochemical impedance
spectroscopy (EIS) was recorded under dark conditions over a
frequency range of 0.1−105 Hz with an ac amplitude of 10 mV, and
the parameters were calculated from Z-View software (v2.1b, Scribner
AssociatNe, Inc.). For the open-circuit voltage decay measurements,
the cell was first illuminated for 20 s to a steady voltage, then the
illumination was turned off for 80 s and the open-circuit voltage decay
curve was recorded.
1
PT-C2. 74 mg, 61.5% yield. H NMR (400 MHz, DMSO-d6): δ
(ppm) 8.17 (s, 1H), 7.91−7.94 (m, 1H), 7.82 (d, J = 2.0 Hz, 1H), 7.57
(s, 2H), 7.55 (s, 2H), 7.15 (d, J = 8.8 Hz, 1H), 7.10 (d, J = 8.8 Hz,
1H), 6.96−7.00 (t, J = 8.8 Hz, 2H), 4.02 (t, J = 6.8 Hz, 2H), 3.97 (t, J
= 6.8 Hz, 2H), 1.70−1.73 (m, 2H), 1.36−1.42 (m, 2H), 1.31−1.34 (m,
7H), 0.88 (t, J = 6.8 Hz, 3H). 13C NMR (400 MHz, DMSO-d6): δ
(ppm) 163.79, 158.23, 152.47, 147.99, 140.59, 135.22, 131.77, 130.68,
128.86, 127.14, 125.48, 125.34, 124.38, 121.90, 121.73, 116.82, 116.20,
114.99, 114.80, 99.25, 41.76, 30.99, 30.68, 28.63, 25.18, 22.07, 13.91,
12.26. HRMS (MALDI-TOF, m/z): [M+] calcd for (C30H30N2O3S)
498.1971; found, 498.2017.
1
PT-C6. 55 mg, 66% yield. H NMR (400 MHz, CDCl3): δ (ppm)
8.07 (s, 1H), 7.88−7.91 (m, 1H), 7.66 (d, J = 2.0 Hz, 1H), 7.42−7.44
(m, 2H), 7.30−7.32 (m, 1H), 7.25 (t, J = 2.0 Hz, 1H), 6.94 (d, J = 2.0
Hz, 1H), 6.93 (d, J = 2.0 Hz, 1H), 6.83−6.89 (m, 2H), 4.00 (t, J = 6.8
Hz, 2H), 3.88 (t, J = 6.8 Hz, 2H), 1.75−1.86 (m, 4H), 1.45−1.47 (m,
4H), 1.32−1.37 (m, 8H), 0.92 (t, J = 6.8 Hz, 6H). 13C NMR (400
MHz, CDCl3): δ (ppm) 168.18, 158.84, 154.63, 150.04, 141.15,
136.39, 132.01, 131.73, 130.50, 127.49, 125.70, 125.40, 125.21, 124.25,
123.45, 116.04, 115.87, 114.92, 114.78, 97.28, 68.18, 48.22, 34.50,
31.60, 31.39, 29.26, 26.68, 26.52, 25.74, 22.61, 14.02, 13.96. HRMS
(MALDI-TOF, m/z): [M+] calcd for (C34H38N2O3S) 554.2598;
found, 554.2580.
1
PT-C8. 59 mg, 74% yield. H NMR (400 MHz, CDCl3): δ (ppm)
8.04 (s, 1H), 7.86 (d, J = 8.4 Hz, 1H), 7.62 (d, J = 8.4 Hz, 1H), 7.41
(d, J = 8.4 Hz, 2H), 7.28−7.31 (m, 1H), 7.21 (d, J = 8.4 Hz, 1H), 6.92
(d, J = 8.4 Hz, 2H), 6.79−6.86 (m, 2H), 3.97 (t, J = 6.4 Hz, 2H), 3.83
(t, J = 6.4 Hz, 2H), 1.75−1.82 (m, 4H), 1.42−1.56 (m, 4H), 1.33−
1.35 (m, 4H), 1.26−1.32 (m, 8H), 0.85−0.90 (m, 6H). 13C NMR
(400 MHz, CDCl3): δ (ppm) 168.76, 158.80, 154.74, 150.24, 142.67,
141.00, 136.68, 132.16, 131.64, 130.40, 127.47, 125.67, 125.29, 124.01,
123.26, 116.02, 115.91, 114.89, 114.71, 97.71, 48.23, 48.15, 31.75,
31.63, 29.28, 29.25, 29.19, 26.85, 26.67, 26.62, 25.77, 22.65, 14.14,
14.10. HRMS (MALDI-TOF, m/z): [M+] calcd for (C36H42N2O3S)
583.2988; found, 583.2987.
PT-C12. 62 mg, 77% yield. 1H NMR (400 MHz, CDCl3): δ (ppm)
8.07 (s, 1H), 7.89 (s, 1H), 7.66 (d, J = 8.8 Hz, 1H), 7.42 (d, J = 8.8
Hz, 2H), 7.25 (d, J = 8.8 Hz, 1H), 7.24 (d, J = 8.8 Hz, 1H), 6.89 (t, J =
8.8 Hz, 2H), 6.83−6.87 (m, 2H), 3.98 (t, J = 6.6 Hz, 2H), 3.87 (t, J =
6.4 Hz, 2H), 1.77−1.83 (m, 4H), 1.43−1.47 (m, 4H), 1.24−1.37 (m,
20H), 0.85−0.92 (m, 6H). 13C NMR (400 MHz, CDCl3): δ (ppm)
168.53, 158.81, 154.72, 150.06, 142.73, 141.98, 141.09, 136.77, 132.11,
C
dx.doi.org/10.1021/cm400800h | Chem. Mater. XXXX, XXX, XXX−XXX