highly efficient, iodine-free dye-sensitized solar cells with solid-state synthesis of conducting...
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Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2011.
Supporting Information for Adv. Mater., DOI: 10.1002/adma. 201004715 Highly Effi cient, Iodine-Free Dye-Sensitized Solar Cells with Solid-State Synthesis of Conducting Polymers Jong Kwan Koh, Jeonghun Kim, Byeonggwan Kim, Jong Hak Kim,* and Eunkyoung Kim*
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DOI: 10.1002/adma.201004715
Supporting Information
Highly Efficient Iodine-Free Dye-Sensitized Solar Cells with Solid-State Synthesis of Conducting Polymers
By Jong Kwan Koh†, Jeonghun Kim†, Byeonggwan Kim, Jong Hak Kim* , Eunkyoung Kim* † Contributed equally to this work.
Department of Chemical and Biomolecular Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul 120-749, South Korea
Experimental.
Materials. The materials used were: N-bromosuccinimide (NBS), acetic acid, ethanol (EtOH),
acetonitrile(AN), lithium trifluoromethane sulfonate (LiCF3SO3, Aldrich Co.), 4-tert-
butylpyridine (TBP), lithium bistrifluoromethanesulfonimide (LiTFSI, Aldrich Co.), TiO2
paste (solaronix D20), and Dye (N719, Solaronix). MPII (1-methyl-3-propyl-imidazolium
iodide), chloroplatinic acid hexahydrate (H2PtCl6), 4-tert-butylpyridine (TBP), and titanium
vis(ethyl acetoacetate) were purchased from Aldrich Chemicals and used without further
purification. 3,4-ethlyenedioxythiphene (EDOT) was purchased from TCI.
Synthesis of 2,5-dibromo EDOT (DBEDOT). 3,4-ethylenedioxythiophene (EDOT) (24.00 g,
168.80 mmol) was dissolved in a solvent mixture of CHCl3 (600 mL) and acetic acid (250
mL). N-bromosuccinimide (NBS, 66.02 g, 371.36 mmol) was slowly added to the mixture at
0°C under an argon atmosphere. Then, the mixture was slowly heated to 25 °C for 30 min and
the mixture was stirred at 25 °C for 24 h. The mixture was washed with water (500 mL) and
the water layer was extracted with chloroform (CHCl3, 250 mL × 3). The organic layer was
neutralized with 5 % sodium bicarbonate solution (500 mL × 2). Then, the extracted organic
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layer was washed with distilled water (500 mL × 2) and dried with anhydrous magnesium
sulfate. Solvent remaining from the filtered mixture was evaporated until little solvent was
left. Then, the remaining solvent was fully evaporated using a vacuum pump. The light yellow
powder was recrystallized from ethanol to produce a white needle-like crystal, and
recrystallization was repeated to obtain highly purified material (38.48 g, 76.0 %) 1H-NMR
(300MHz, CDCl3, δ): 4.27(s, 4H). MS: m/z (%): 302 (55) [M+], 300 (100), 298 (55).
Characterization.The 1H-NMR and FT-IR spectra were obtained using the BRUKER ARX-
400 and TENSOR-37 (Bruker), respectively. MALDI-TOF MS was performed using an
AXIMA Performance (SHIMADZU). DSC measurements were performed on a NETZSCH /
DSC 200 F3 and the morphology was observed with HR-SEM (Carl Zeiss, model SUPRA
55VP). EF-TEM images were obtained using a Philips CM30 operating at 300 kV. The
conductivities of the samples were measured using an electrochemical analyzer (CH
Instruments Inc, CHI624B) and a four-point probe (ALS, Japan). The DBEDOT was
polymerized at 60 °C for 24 hr and pelletized with 3 mm thickness. The XRD measurements
were carried out on a Rigaku RINT2000 at 40 kV and 300 mA (λ = 0.154 nm).
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Figure S1. FT-IR spectra. TiO2-PEDOT composite and pristine TiO2 particle were raked
from FTO substrate after synthesis. FT-IR spectrum of DBEDOT was measured after
polymerization at 60 °C for 24 hr.
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Figure S2. HR-SEM images. a) TiO2 layer on FTO glass. b) Image of surface of TiO2 layer
after dye adsorption. c) Magnified image of surface of TiO2 layer after dye adsorption. d)
Magnified image of cross-section of TiO2 layer after dye adsorption. e) Image of surface of
TiO2 layer after penetration of DBEDOT and solid-state polymerization at 60 °C. f) Image of
cross-section of TiO2 layer after penetration of DBEDOT and solid-state polymerization at
60 °C. g) Image of surface of TiO2 layer after adding LiTFSI salt solution. h) Image of cross-
section of TiO2 layer after adding LiTFSI salt solution.
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Figure S3 . DSC and XRD characterizations for SSP of DBEDOT. Isothermal DSC curves of a) the DBEDOT monomer crystals and b) DBEDOT penetrated TiO2 layer at different temperatures (60 °C (green), 70 °C (red), 80 °C (blue), and 90 °C (magenta)). c) Arrhenius dependence of the SSP of DBEDOT monomer crystal (red line) and DBEDOT penetrated TiO2 layer (blue line) as determined by isothermal DSC. d) Powder XRD patterns of TiO2, DBEDOT, crystalline ssPEDOT, and TiO2 layer after DBEDOT penetration and polymerization.
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Figure S4. Cell performances of iodine-free ssDSSCs according to various additives. J-V
curves of iodine-free ssDSSCs with a) LiI and b) 1-ethyl-3-methylimidazolium chloride, 1-
ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium bis (trifluoromethyl
sulfonyl)imide as additives at 100 mW cm-2.
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Table S1. Peak assignments for FT-IR spectra of Figure S1.
Sample Peak (cm-1) and notes
TiO2 3340 cm−1 (H-O-H stretching), 1640 cm−1 (-OH)
850-600 cm−1 (stretching vibration of the Ti-O-Ti group)
DBEDOT 1357 cm−1 (C–C stretching in the thiophene ring)
1074 cm−1 (C–O stretching)
973 cm−1 (C–S stretching)
ssPEDOT 1540 - 1485 cm−1 (conjugated C=C asymmetric and symmetric stretching
vibration)
1357 cm−1 (C–C stretching in the thiophene ring)
1074 cm−1 (C–O stretching)
973 cm−1 (C–S stretching)
TiO2-ssPEDOT 3340 cm−1 (H-O-H stretching), 1640 cm−1 (-OH)
850-600 cm−1 (stretching vibration of the Ti-O-Ti group)
1540 - 1485 cm−1 (conjugated C=C asymmetric and symmetric stretching
vibration)
1357 cm−1 (C–C stretching in the thiophene ring)
1074 cm−1 (C–O stretching)
973 cm−1 (C–S stretching)
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Table S2. Performances of iodine-free ssDSSCs fabricated with ssPEDOT and various
additives at 100 mW cm-2.
Additive (with LiTFSI + TBP)
Voc (V) Jsc
(mA cm-2) FF
Efficiency (%)
1-Ethyl-3-methylimidazolium chloride 0.01 0.24 0.36 0.001
1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide
0.03 0.25 0.65 0.006
1-Ethyl-3-methylimidazolium bromide
0.24 0.10 0.095 0.002
LiI 0.53 16.6 0.52 4.661