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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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Figure S5. The chemical capacitance (Cµ) as a function of bias voltage.

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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