Application of Poly(3,4-ethylenedioxythiophene):Polystyrenesulfonate

Article pubs.acs.org/JPCC

Application of Poly(3,4ethylenedioxythiophene):Polystyrenesulfonate/Polypyrrole Counter Electrode for Dye-Sensitized Solar Cells Gentian Yue, Jihuai Wu,* Yaoming Xiao, Jianming Lin, Miaoliang Huang, and Zhang Lan Engineering Research Center of Environment-Friendly Functional Materials, Ministry of Education, Institute of Material Physical Chemistry, Huaqiao University, Quanzhou 362021, China ABSTRACT: A low-cost poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and polypyrrole (PPy) composite film was fabricated on a rigid fluorine-doped tin oxide (FTO) substrate used as the counter electrode in a dye-sensitized solar cell (DSSC) by a facile electrochemical polymerization method. The cyclic voltammetry and electrochemical impedance spectroscopy measurements show that the PEDOT:PSS/PPy film has a low surface resistance, high conductivity, and good catalytic performance for the I−/I3− electrolyte. The power conversion efficiency of the DSSC based on the PEDOT:PSS/PPy counter electrode reaches 7.60% under a simulated solar light illumination of 100 mW·cm−2; the efficiency is comparable to that of the DSSCs based on a sputtered Pt electrode.

1. INTRODUCTION The development of sustainable energies that do not rely on fossil fuels is a key objective of modern research. Since the report by O’Regan and Grätzel in 1991,1 dye-sensitized solar cells (DSSCs) have attracted considerable attention as an alternative to conventional silicon solar cells because of their low cost, low energy consumption, simple fabrication process, and high power conversion efficiency.2,3 Typically, platinum (Pt) is employed as the counter electrode (CE) of DSSCs by being sputtered or thermally deposited on conducting glasses to catalyze the iodine/iodide redox couple and complete the electric circuit in the DSSCs. However, the large-scale manufacturing of DSSCs may be impeded since Pt is one of the most expensive metals and a corrosive material in the presence of water in the electrolyte.4,5 Therefore, it is necessary to develop new Pt-free CEs with a simple fabrication procedure while maintaining their high performances. Many attempts have been made on Pt substitution, cheap carbonaceous materials,6−10 and conducting polymers,11−13 and CoS and NiS214−16 counter electrodes have been employed in DSSCs. Among them, conducting polymers are a promising candidate as counter electrode materials for DSSCs, because of their advantages: low-cost availability, high conductivity, large electrochemical surface area, and good electrocatalytic activity for I3− reduction.17,18 Previously, we have paid much attention to the PEDOT:PSSbased counter electrodes and obtained a promising result.19 Polypyrrole (PPy), as a typical conductive polymer and counter electrode material, has been studied by our group and obtained good performance in DSSCs.20 In our present work, the PEDOT:PSS/PPy film that served as the counter electrode in DSSCs was prepared by using an electrochemical polymer© 2012 American Chemical Society

ization method. Electrochemical and impedance spectra measurements reveal that the PEDOT:PSS/PPy electrode is a potential candidate for a Pt-free counter electrode in DSSCs, and the result reveals fundamental information about DSSCs and will broaden the application of conductive polymers in the field.

2. EXPERIMENTAL SECTION 2.1. Materials. The lithium perchlorate (LiClO4), oxalic acid (C2H2O4), acetic acid (HAc), poly(styrenesulfonate) (PSS), 3,4-ethylenedioxythiophene (EDOT), pyrrole, and titanium tetrachloride (TiCl4) were purchased from Shanghai Chemical Agent Ltd., China. The organometallic compound sensitized dye N-719 [RuL2 (NCS)2, L = 4,4′-dicarboxylate2,2′-bipyridine] was obtained from Solaronix SA. Pyrrole monomer was distilled prior to use. All reagents were of analytical reagent grade. A conductive glass plate (FTO glass, with a fluorine-doped tin oxide overlayer having a sheet resistance of 8 Ω·cm−2, purchased from Hartford Glass Co.) was used as the substrate for precipitation of the TiO2 porous film and was cut into 1 × 2 cm2 sheets. 2.2. Preparation of PEDOT:PSS/PPy Electrode. A typical synthesis of PEDOT:PSS proceeded as follows. A 6.95 g portion of PSS (18 wt %) aqueous solution was mixed with 75 mL of deionized water at room temperature and treated with nitrogen bubbling for 0.5 h. A 0.5 g portion of EDOT and Received: April 24, 2012 Revised: July 21, 2012 Published: August 2, 2012 18057

dx.doi.org/10.1021/jp303958r | J. Phys. Chem. C 2012, 116, 18057−18063

The Journal of Physical Chemistry C

Article

Figure 1. Synthesis route and structural sketch diagram of PEDOT:PSS and polypyrrole.

Figure 2. SEM images of (a) polypyrrole film and (b) PEDOT:PSS/PPy film.

0.0077 g of Fe2(SO4)3·9H2O were then added to initiate the polymerization. The mixture was stirred at room temperature for 2 h, and then 0.1673 g of Na2S2O8 was added. After additional reaction time for 12 h, the blue powder of PEDOT:PSS was collected by filtration, washed, and then dried overnight in a vacuum oven at 80 °C. (The synthesis route and structural schematic diagram is shown in Figure 1.) The polymerization of PEDOT:PSS/PPy was carried out in 50 mL of an aqueous solution containing 0.1 M pyrrole, 0.1 M LiClO4, 0.1 M oxalic acid, and the blue powder of PEDOT:PSS. A three-electrode electrochemical cell was used for polymerizations. The working electrode was a polished FTO substrate with a surface area of 0.5 × 0.5 cm2. The platinized sheet of 1 × 2 cm2 was used as the counter electrode and a Ag/AgCl electrode as the reference electrode. All polymerizations were performed at room temperature (about 25 °C). 2.3. Fabrication of Dye-Sensitized Solar Cell. A TiO2 nanoporous film was prepared as described previously.21,22 A thin TiO2 blocking layer was deposited on the FTO substrate by immersing the FTO in 0.15 M TiCl4 isopropanol solution for 12 h, followed by sintering at 450 °C for 30 min in air. Subsequently, a TiO2 layer with a particle size of 10−20 nm was coated on the blocking layer by using a “doctor blade method”, then sintering at 450 °C for 30 min in air. A dye was loaded by immersing the TiO2 film in a 0.3 mM dye N719 ethanol solution for 12 h. Thus, a dye-sensitized TiO2 anode with a thickness of 10 μm was obtained. A dye-sensitized solar cell was fabricated by injecting a liquid electrolyte (0.05 M I2,

0.1 M LiI, 0.6 M tetrabutylammonium iodide, and 0.5 M TBP in acetonitrile) in the aperture between the dye-sensitized TiO2 electrode and the PEDOT:PSS/PPy counter electrode. The two electrodes were clipped together, and a cyanoacrylate adhesive was used as a sealant. The details for the assembly of the DSSCs was described by us elsewhere.22−24 2.4. Characterization and Measurements. The micromorphology of the PEDOT:PSS/PPy electrode was observed by using a JSM-6700F field emission scanning electron microscope (FESEM). The conductivity of the PEDOT:PSS/ PPy composite film was tested by using an RTS-9 model, fourpoint probe resistivity measurement system. Cyclic voltammetry (CV) measurements of the samples were taken in a threeelectrode one-compartment cell with a PEDOT:PSS/PPy coating on an FTO working electrode, a Pt foil counter electrode, and a Ag/AgCl reference electrode dipped in an acetonitrile solution of 10 mM LiI, 1 mM I2, and 0.1 M LiClO4. CV was performed using the electrochemical workstation (CHI660D, Shanghai Chenhua Device Company). The electrochemical impedance spectroscopy (EIS) was carried out using a CHI660D electrochemical workstation at a constant temperature of 20 °C with an ac signal amplitude of 20 mV in the frequency range from 0.1 to 105 Hz at 0 V dc bias in the dark. The photovoltaic testing of the DSSCs was carried out by measuring photocurrent−photovoltage (J−V) characteristic curves under white light irradiation of 100 mW·cm−2 from a solar simulator (XQ-500W, Shanghai Photoelectricity Device 18058



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surface roughness compared with the pure polypyrrole film. The uniform PEDOT:PSS/PPy film is well adhered on the FTO. The image indicates that the small PEDOT:PSS particles have homogeneously dispersed in the pyrrole monomer and formed a uniform and porous film. Therefore, it could be inferred from the surface morphology that the PEDOT:PSS/ PPy film is expected to possess a high effective electrochemical surface area and large rough surface, which is crucial for high electrocatalytic activity of the counter electrodes.25,26 3.2. FTIR Spectra. Figure 3 shows the FTIR spectra of the EDOT, PSS, pyrrole, polypyrrole, PEDOT:PSS, and PEDOT:PSS/PPy films. Curve a in Figure 3 is for the EDOT sample; the main vibrations are in the region of 1600−500 cm−1. The 891 cm−1 is due to the C−H bending vibration of the thiophene ring, while it disappears after electrochemical polymerization, indicating the polymerization of EDOT by α−α′;27 the vibrations at around 1356 and 1513 cm−1 are due to the C−C or CC stretching of the quinoidal structure and the ring stretching of the thiophene ring, respectively.28 Curve b in Figure 3 is for the PSS sample. The bands at 1581 and 1366 cm−1 are due to bending vibration of the thiophene ring, and 1142 and 1034 cm−1 are assigned to SO3 of the PSS.29 The peak at 1008 cm−1 is attributed to a bending mode of C− H on aromatic rings of the PSS.29 The above characteristic peaks all have some shift or disappear after polymerization. Curve c in Figure 3 is for the pyrrole sample; a strong and broad band between 3430 and 3200 cm−1, a series of narrow bands at 3138, 3106, 3058, 2945, 2850, 1532, 1473, 1420, and 1380 cm−1 are characteristic of the in-plane vibration of the pyrrole ring, indicating that the ring structure is not affected by polymerization.30 The strong peak between 700 and 800 cm−1, characteristic of a five-membered aromatic ring, is present for both the pyrrole monomer and the extracted polypyrrole.31 Curve d in Figure 3 is for the PEDOT:PSS sample; the bands at 1303, 1187, 1085, 978, and 834 cm−1 are derived from the PEDOT.32 The bands at 1142 and 1034 cm−1 are assigned to SO3, and the peak at 1008 cm−1 is attributed to a bending mode of C−H on aromatic rings of the PSS.29 Curve e in Figure 3 is for the polypyrrole sample; the main characteristic peak at 1556 cm−1 may be assigned to typical polypyrrole ring vibrations.33,34 The band at 1036 cm−1 corresponds to the N−H in-plane deformation. The peaks at 1210 and 914 cm−1 may be assigned to the N−C stretching band and C−H band. Curve f in Figure 3 is for the PEDOT:PSS/PPy sample; the above characteristic peaks of polypyrrole and PEDOT:PSS are all reflected in the spectrum of the PEDOT:PSS/PPy. However, they all have some shift or disappear, indicating that the backbone structure of polypyrrole and PEDOT:PSS is not damaged by the electrochemical polymerization. There are interactions (probably π−π noncovalent bonds) between polypyrrole and PEDOT:PSS, and these interactions can make electron transport between polypyrrole and PEDOT:PSS occur easily. 3.3. Electrochemical Impedance Analysis. Electrochemical impedance spectroscopy (EIS) is a powerful steadystate technique that has been widely used to investigate internal resistances and charge-transfer processes in electrochemical systems. Figure 4 shows the EIS of polypyrrole, PEDOT:PSS, PEDOT:PSS/PPy, and Pt electrodes on FTO glass substrates and their equivalent circuit of impedance spectra at the highfrequency region for the CEs; the results are summarized in Table 2. The high-frequency feature is attributed to an

Company, China) in an ambient atmosphere and using a computer-controlled voltage current source meter of the CHI660D electrochemical measurement system. The active cell area was 0.25 cm2. The fill factor (FF) and the power conversion efficiency (η) of the solar cell were calculated according to the following equations2 η (%) =

Vmax × Jmax Pin

× 100 %=

VOC × JSC ×FF Pin

× 100% (1)

FF=

Vmax × Jmax VOC × JSC

(2)

where JSC is the short-circuit current density (mA·cm−2), VOC is the open-circuit voltage (V), Pin is the incident light power, and Jmax (mA·cm−2) and Vmax (V) are the current density and voltage at the point of maximum power output in the J−V curves, respectively.

3. RESULTS AND DISCUSSION 3.1. Morphology of PEDOT:PSS/PPy Electrode. Figure 2 shows the SEM image of polypyrrole film before and after

Figure 3. FTIR spectra of (a) EDOT, (b) PSS, (c) pyrrole, (d) PEDOT:PSS, (e) polypyrrole, and (f) PEDOT:PSS/PPy.

Figure 4. EIS measurements of the dummy cell fabricated with two identical CEs and equivalent circuit models for the I−/I3− reaction: Rs, Ohmic serial resistance; Rct, charge-transfer resistance of a single electrode; CPE, double-layer capacitance; W, diffusion impedance.

doping the PEDOT:PSS. Figure 2a shows the polypyrrole film by electrochemical polymerization aggregated on the FTO glass; the PEDOT:PSS/PPy film (Figure 2b) has a lower 18059



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Figure 5. Cyclic voltammograms for (a) Pt, polypyrrole, PEDOT:PSS, and PEDOT:PSS/PPy electrodes and (b) the PEDOT:PSS/PPy electrodes with different electrochemical cycles; scan rate = 50 mV·s−1.

Figure 6. (a) CV for the PEDOT:PSS/PPy electrode using acetonitrile solution containing 0.1 M LiClO4, 10 mM LiI, and 1 mM I2 as supporting electrolyte; scan rate = 50 mV·s−1, cycle time = 10. (b) The relationship between the cycles and the maximum redox peak currents for the PEDOT:PSS/PPy electrode; scan rate = 50 mV·s−1. (c) 100 cycles CV of the PEDOT:PSS/PPy electrode at the scan rate of 50 mV·s−1.

interfacial charge-transfer resistance (Rct) at the CE.35,36 The Rct is much smaller on the PEDOT:PSS/PPy electrode (4.3 ± 0.02 Ω·cm−2) than that of the PPy (29.32 ± 0.02 Ω·cm−2) and PEDOT:PSS (22.32 ± 0.02 Ω·cm−2) CEs, which is comparable to that of the Pt electrode (2.1 ± 0.02 Ω·cm−2) under the same conditions. This phenomenon indicates that a lower interfacial charge-transfer resistance occurred at the interface between the PEDOT:PSS/PPy CE and the electrolyte, due to the high electrical conductivity and superior electrocatalytic activity of the PEDOT:PSS/PPy film. Furthermore, the lower Rct may contribute to the higher JSC and FF for the DSSCs based on PEDOT:PSS/PPy CEs (listed in Table 2). 3.4. Electrochemical Properties of PEDOT:PSS/PPy Electrode. To further confirm the results from SEM and EIS

analyses, cyclic voltammetric tests were measured. It is well known that, in DSSCs, electrons are injected into photooxidized dye from I− ions in the electrolyte (eq 3), and the produced I3− ions are reduced on the counter electrode (eq 4).3 3I− − 2 e= I3−

(anodic)

(3)

I3− + 2 e= 3I−

(cathodic)

(4)

Consequently, only the cathodic reaction is considered in the CV test, and −0.4 to 0.4 V was selected as the scan range, according to a previous report.37 In this case, the anodic peak in an anodic sweep and the cathodic peak in a cathodic sweep are due to the reactions 3 and 4, respectively. Figure 5a shows the CV curves of the Pt, polypyrrole, PEDOT:PSS, and 18060



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Figure 7. (a) CV for the PEDOT:PSS/PPy film with different scan rates (from inner to outer: 10, 30, 50···150 mV·s−1). (b) The redox peak current versus square root of scan rate.

Table 1. Influence of Temperature on the Conductivity and Resistance of the PEDOT:PSS/PPy Electrode

40 °C

80 °C

100 °C

V23+ (mV)

V23− (mV)

V24+ (mV)

V24− (mV)

resistance (Ω·cm)

resistance average (Ω·cm)

conductivity (S·cm−1)

conductivity average (S·cm−1)

1.5 1.51 1.52 1.38 1.33 1.3 1.56 1.52 1.51

1.53 1.5 1.53 1.38 1.33 1.4 1.54 1.48 1.5

1.17 1.16 1.16 1.15 1.09 1.09 1.31 1.21 1.24

1.2 1.15 1.16 1.14 1.09 1.1 1.31 1.27 1.25

0.77 0.79 0.76 0.64 0.63 0.65 0.7 0.7 0.7

0.773

1.299 1.266 1.263 1.563 1.587 1.538 1.429 1.429 1.429

1.276

0.64

0.7

1.563

1.429

CE. This indicates that the overpotential for reduction of I3− to I− of the sputtered-Pt CE is much smaller than that of the PEDOT:PSS CE. However, the cathodic current density of the PEDOT:PSS/PPy CE is significantly higher than that of other CEs, indicating a much faster I3−/I− reaction rate. The PEDOT:PSS/PPy CE with superior electrochemical activity may largely be due to the superior electrocatalytic activity and high conductivity surface of the PEDOT:PSS and polypyrrole, which is in agreement with the SEM and EIS results. Figure 5b shows CV curves of the PEDOT:PSS/PPy electrode with different electrochemical polymerization cycles. It can be observed that the electrode with three cycles of electrochemical polymerization has the higher current density than that of other electrodes, demonstrating that the thickness of the films has a great impact on the electrocatalytic activity. Figure 6 shows the consecutive 10 cycles of the I3−/I− system for the PEDOT:PSS/PPy electrode from +0.4/−0.4 V at the scan rate of 50 mV·s−1. The CV curves do not change, and both redox peak currents show a good linear relationship with the cycle times, exhibiting a stable cathodic peak current density. This indicates that the PEDOT:PSS/PPy film not only possesses excellent electrochemical stability but also is attached firmly and uniformly on the FTO glass.11

Figure 8. Photocurrent−voltage characteristics of DSSCs with PEDOT:PSS, PPy, PEDOT:PSS/PPy, and Pt counter electrodes under the illumination of AM 1.5G (100 mW·cm−2).

PEDOT:PSS/PPy electrodes at a scan rate of 50 mV·s−1. It can be seen that one pair of redox peaks are observed in the CV curves and are almost identical, and their cathodic peak potentials are much more positive than that of the PEDOT:PSS

Table 2. Influences of CEs on the Photovoltaic Properties of DSSCsa

a

electrodes

VOC (V)

JSC (mA·cm−2)

FF

η (%)

PEDOT:PSS PPy Pt PEDOT:PSS/PPy

0.73 0.72 0.76 0.75

12.53 11.15 14.75 14.27

0.69 0.65 0.69 0.71

6.31 5.23 7.73 7.60

Rct (Ω·cm−2) 22.32 29.32 2.1 4.3

± ± ± ±

0.02 0.02 0.02 0.02

Conditions: liquid electrolyte contains 0.1 M KI, 0.01 M I2, 0.6 M tetrabutylammonium iodide, and acetonitrile. 18061



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Figure 7a shows the CV of the I−/I3− system on the PEDOT:PSS/PPy CE with different scan rates. The absolute values of the cathodic and anodic peak current densities gradually and regularly shift to the negative and positive directions with increasing scan rate, respectively. Meanwhile, the good linear relationship between the square root of the scan rate and the peak current density is shown in Figure 7b, revealing the diffusion limitation of the redox reaction on PEDOT:PSS/PPy CE and no specific interaction between the I−/I3− redox couple and the PEDOT:PSS/PPy CE.11 3.5. Influence of Temperature on the Conductivity of PEDOT:PSS/PPy Electrode. Table 1 shows the conductivity and resistance of the PEDOT:PSS/PPy electrode with different temperature heating. It is observed that the conductivity and resistance regularly shift with the temperature increase, and the optimal values are obtained at 80 °C, which are about 1.563 S·cm−1 and 0.64 Ω·cm, respectively. This phenomenon is mainly caused by the transmission mechanism of PEDOT:PSS.38,39 The heating could change the particle size and the conductance between PEDOT:PSS particles. This indicates that annealing could improve the conductivity of the PEDOT:PSS/PPy CE and enhance the performance of DSSCs. 3.6. Photovoltaic Performance of DSSCs with PEDOT:PSS/PPy Electrode. The four devices based on PEDOT:PSS, PPy, PEDOT:PSS/PPy, and Pt counter electrodes were prepared, respectively. Figure 8 represents the J−V curves of four devices using the PEDOT:PSS, PPy, PEDOT:PSS/PPy, and Pt CEs under a simulated solar light illumination of 100 mW·cm−2. The power conversion efficiency of the devices was determined by JSC, VOC, and FF, and the photovoltaic parameters for the four DSSCs are summarized in Table 2. When the PEDOT:PSS/PPy film was used as the counter electrode, the DSSC exhibits a JSC of 14.27 mA·cm−2, VOC of 0.75 V, FF of 0.71, and power conversion efficiency of 7.60%, which is comparable to that of the Pt counter electrode (7.73%), whereas the DSSCs based on PEDOT:PSS and PPy electrodes show a smaller JSC, which is due to their high Rct. It is noteworthy that the device using the PEDOT:PSS/PPy counter electrode showed a higher FF for the excellent VOC, JSC, and Rct. This implies that the enhancement of power conversion efficiency can be achieved by simply applying the conducting polymer electrode.

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AUTHOR INFORMATION

Corresponding Author

*Tel: +86 595 22693899. Fax: +86 595 22692229. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS

■

REFERENCES

The authors are thankful for the joint support by the National High Technology Research and Development Program of China (No. 2009AA03Z217) and the National Natural Science Foundation of China (Nos. 90922028, 50842027).

(1) O’Regan, B.; Grätzel, M. Nature 1991, 353, 737−740. (2) Grätzel, M. Nature 2001, 414, 338−344. (3) Grätzel, M. Acc. Chem. Res. 2009, 42, 1788−1798. (4) Papageorgiou, N.; Maier, W. F.; Grätzel, M. J. Electrochem. Soc. 1997, 144, 876−884. (5) Kay, A.; Grätzel, M. Sol. Energy Mater. Sol. Cells 1996, 44, 99− 117. (6) Imoto, K.; Takahashi, K.; Yamaguchi, T.; Komura, T.; Nakamura, J.; Murata, K. Sol. Energy Mater. Sol. Cells 2003, 79, 459−469. (7) Han, J.; Kim, H.; Kim, D. Y.; Jo, S. M.; Jang, S. Y. ACS Nano 2010, 4, 3503−3509. (8) Roy-Mayhew, J. D.; Bozym, D. J.; Punckt, C.; Aksay, I. A. ACS Nano 2010, 4, 6203−6211. (9) Wu, M. X.; Lin, X.; Hagfeldt, A.; Ma, T. L. Angew. Chem., Int. Ed. 2011, 50, 3520−3524. (10) Wu, M. X.; Lin, X.; Wang, T. H.; Qiu, J. H.; Ma, T. L. Energy Environ. Sci. 2011, 4, 2308−2315. (11) Li, Q. H.; Wu, J. H.; Tang, Q. W.; Lan, Z.; Li, P. J.; Lin, J. M. Electrochem. Commun. 2008, 10, 1299−1302. (12) Sun, H.; Luo, Y.; Zhang, Y.; Li, D.; Yu, Z.; Li, K.; Meng, Q. B. J. Phys. Chem. C 2010, 114, 11673−11679. (13) Jeon, S. S.; Kim, C.; Ko, J.; Im, S. S. J. Mater. Chem. 2010, 21, 8146−8151. (14) Wang, M. K.; Anghel, A. M.; Marsan, B.; Ha, N. C.; Pootrakulchote, N.; Zakeeruddin, S. M.; Grätzel, M. J. Am. Chem. Soc. 2009, 131, 15976−15977. (15) Lin, J. Y.; Liao, J. H.; Chou, S. W. Electrochim. Acta 2011, 56, 8818−8826. (16) Sun, H. C.; Qin, D.; Huang, S. Q.; Guo, X. Z.; Li, D. M.; Luo, Y. H.; Meng, Q. B. Energy Environ. Sci. 2011, 4, 2630−2737. (17) Ahmad, S.; Yum, J. H.; Xianxi, Z.; Grätzel, M.; Butt, H. J.; Nazeeruddin, M. K. J. Mater. Chem. 2010, 20, 1654−1658. (18) Ahmad, S.; Yum, J. H.; Butt, H. J.; Nazeeruddin, M. K.; Grätzel, M. ChemPhysChem 2010, 11, 2814−2819. (19) Yue, G. T.; Wu, J. H.; Xiao, Y. M.; Lin, J. M.; Huang, M. L. Electrochim. Acta 2012, 67, 113−118. (20) Wu, J. H.; Li, Q. H.; Fan, L. Q.; Lan, Z.; Li, P. J.; Lin, J. M.; Hao, S. C. J. Power Sources 2008, 181, 172−176. (21) Grätzel, M. Inorg. Chem. 2005, 44, 6841−6851. (22) Wu, J. H.; Lan, Z.; Lin, J. M.; Huang, M. L.; Hao, S. C.; Sato, T.; Yin, S. Adv. Mater. 2007, 19, 4006−4011. (23) Wu, J. H.; Hao, S. C.; Lan, Z.; Lin, J. M.; Huang, M. L.; Huang, Y. F.; Li, P. J.; Yin, S.; Sato, T. J. Am. Chem. Soc. 2008, 130, 11568− 11569. (24) Wu, J. H.; Yue, G. T.; Xiao, Y. M.; Ye, H. F.; Lin, J. M.; Huang, M. L. Electrochim. Acta 2010, 55, 5798−5802. (25) Yen, M. Y.; Hsieh, C. K.; Teng, C. C.; Hsiao, M. C.; Liu, P. I.; Ma, C. C. M.; Tsai, M. C.; Tsai, C. H.; Lin, Y. R.; Chou, T. Y. RSC Adv. 2012, 2, 2725−2728. (26) Peng, S. J.; Liang, J.; Mhaisalkar, S. G.; Ramakrishna, S. J. Mater. Chem. 2012, 22, 5308−5311. (27) Li, C.; Imae, T. Macromolecules 2004, 37, 2411−2416.

4. CONCLUSION In conclusion, conductive polymers, PEDOT:PSS/PPy film with a low surface resistance and high conductivity, were synthesized by an electrochemical polymerization method. The obtained PEDOT:PSS/PPy film was used as the counter electrode in dye-sensitized solar cells, and it shows good catalytic behavior for the I−/I3− redox reaction and high JSC, VOC, and FF for DSSCs, indicating that PEDOT:PSS/PPy is a promising electrode material in DSSCs. Though the interfacial charge-transfer resistance for PEDOT:PSS/PPy is moderately higher than that for the Pt electrode, the largest power conversion efficiency of 7.60% (under a simulated solar light illumination of 100 mW·cm−2) for the DSSC based on PEDOT:PSS/PPy is comparable to that of the DSSC based on the Pt electrode. The investigation will broaden the application of conductive polymers with low cost and high efficiency in DSSCs. 18062



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(28) Mathiyarasu, J.; Senthilkumar, S.; hani, K. L. N. P.; Yegnaraman, V.; Nanosci, J. Nanotechnology 2007, 7, 2206−2210. (29) Wang, Z. S.; Sasaki, T.; Muramatsu, M.; Ebina, Y.; Tanaka, T.; Wang, L. Z.; Watanabe, M. Chem. Mater. 2003, 15, 807−812. (30) Zhang, J.; Wu, M. Z.; Pu, T. S.; Zhang, Z. Y.; Jin, R. P.; Tong, Z. S.; Zhu, D. Z.; Cao, D. X.; Zhu, F. Y.; Cao, J. Q. Thin Solid Films 1997, 307, 14−20. (31) John, R. K.; Kumar, D. S. J. Appl. Polym. Sci. 2002, 83, 1856− 1859. (32) Kvarnstrom, C.; Neugebauer, H.; Blomquist, S.; Ahonen, H. J.; Kankare, J.; Ivaska, A.; Sariciftci, N. S. Synth. Met. 1999, 101, 66−66. (33) Guo, H. F.; Zhu, H.; Lin, H. Y.; Zhang, J. Q. Polym. Sci. 2008, 286, 587−591. (34) Ham, H.; Choi, Y.; Jeong, N.; Chung, I. Polymer 2005, 46, 6308−6315. (35) Fabregat-Santiago, F.; Bisquert, J.; Palomares, E.; Otero, L.; Kuang, D.; Grätzel, M. J. Phys. Chem. C 2007, 111, 6550−6560. (36) Gagliardi, S.; Giorgi, L.; Giorgi, R.; Lisi, N.; Makris, T. D.; Salernitano, E.; Rufoloni, A. Superlattices Microstruct. 2009, 46, 205− 208. (37) Wei, T. C.; Wan, C. C.; Wang, Y. Y.; Chen, C. C.; Shiu, H. S. J. Phys. Chem. C 2007, 111, 4847−4853. (38) Huang, J.; Millerb, P. F.; de Mellob, J. C.; de Mellob, A. J.; Bradley, D. D. C. Synth. Met. 2003, 139, 569−572. (39) Aasmundtveit, K. E.; Samuelsen, E. J.; Pettersson, L. A. A.; Inganäs, O.; Johansson, T.; Feidenhans, R. Synth. Met. 1999, 101, 561−564.

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Application of Poly(3,4-ethylenedioxythiophene):Polystyrenesulfonate

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