Study on Fabricating PEDOT Electrodes by Liquid Phase Depositional

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Study on Fabricating PEDOT Electrodes by Liquid Phase Depositional Polymerization of EDOT and Direct Patterning with 172 nm VUV Radiation Jianxiong Li, and Yaxiao Ma ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.7b00031 • Publication Date (Web): 07 Dec 2017 Downloaded from http://pubs.acs.org on December 12, 2017

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ACS Applied Energy Materials

Study on Fabricating PEDOT Electrodes by Liquid Phase Depositional Polymerization of EDOT and Direct Patterning with 172 nm VUV Radiation Jian-Xiong Li*and Ya-Xiao Ma School of Materials Science and Engineering, South China University of Technology Wushan, Tianhe, Guangzhou, 510640, P. R. China Abstract: Transparent electrode made of conventional flexible transparent conductive film (FTCF) exhibits poor fatigue lifetime due to its brittle indium-tin oxide (ITO) coating. To develop ITO-free flexible transparent electrode, poly(ethylene phthalate) (PET) film with ferric p-toluene-sulfonate (Fe(OTs)3) coating was immersed in 3,4-ethylenedioxythiophene (EDOT) solution for in situ synthesizing poly(3,4-ethylenedioxythiophene) (PEDOT) coating and irradiated with 172 nm VUV through mask for creating conductive patterns. The sheet resistance and transmittance of the films were measured with four-point probe and spectrophotometer. The conjugative structure and doping level of the synthesized PEDOT coatings were analyzed with UV-vis spectroscopes and X-ray photoelectron spectroscope. The effects of processing conditions on the microscopic structures and optoelectronic properties of the coatings were studied. Conductive PEDOT coating formed as PET film with Fe(OTs)3 coating was suspended in EDOT solution at temperature from 30–70 oC. The continuous conjunctive length and doping degree of the synthesized PEDOT coatings increased with polymerization temperature; so did the conductivity and transmittance. But the coating thickness and sheet resistance got extremum at 60 oC because some EDOT oligomers diffused into solution phase at temperature above 60 oC and did not contribute to the coating. Imidazole retardant not only depressed the conjunctive defects but also reduced the doping level. The conductivity and sheet resistance of the coating got extremum as imidazole content increased. Post oxidation in Fe(OTs)3 solution eliminated EDOT oligomers on the coating and improved the continuous conjugative length and doping degree, thereby, enhanced the conductivity and transmittance greatly. PEDOT/PET film with transmittance 85 % and sheet resistance 140 Ω/ has been synthesized. As conductive PEDOT coating was exposed to 172 nm VUV under mask in air, the irradiated portions turned to nonconductive while the shadowed portions remained conductive still. Keywords: FTCF, PEDOT, ITO-free, in–situ synthesis, VUV * Corresponding author: E-mail: [email protected];

Phone: 86-20-87114926. 1

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1. Introduction Flexible transparent conductive film (FTCF) is a raw material for transparent electrodes of flexible optoelectronic devices, such as bendable organic photovoltaic cells, stretchable/wearable electrochromic supercapacitors, rollable organic light-emitting diode displays, electronic papers and touch screens. Currently, most FTCFs commercially available are polymeric film with indium tin oxide (ITO) coating. But such FTCF cannot meet the requirements to flexible optoelectronics due to the brittleness and scarcity of ITO.1 Many researchers have been devoting themselves to developing novel FTCF free of ITO. The investigated transparent conductors include oxide semiconductors,2 nano-metals,3 conducting polymers,4 graphene and carbon nano-tube.5 Of them, sliver nanowire (Ag NW) network3 and poly(3,4-ethylenedioxythiophene) (PEDOT)4,6 film seem to have advantages over others. But Ag NW network possesses poor uniformity in conductivity7 and PEDOT film is confronted with difficulty in film formation. As a suspension of Ag NWs is spread on transparent polymeric films, the Ag NWs lie on the film randomly and construct a Ag NW network on the film, which makes the film two-dimensional conductive.3 The sheet resistance of the film with Ag NWs network may be in the magnitude of ten ohm and the transmittance above 80 %. Alternatively, laying Ag grids on transparent polymeric films may form FTCF also.8 However, the Ag wire FTCFs are highly uneven. Although they are electrical conductive in the direction parallel to the film, the transfer of charge carriers within the “eyes” of the Ag-wire network relies on percolating and the conductance of the film in submicron scale varies several orders of magnitude.7 This will affect the injection or extraction of charge carriers in the active layer of optoelectronic devices. To solve the problem in uniformity, many researchers filled conducting materials into Ag wire network.7,8 Chen and his colleagues spin-coated aqueous dispersion of PEDOT/poly(styrene-sulfonate) (PSS) complex on Ag-grid FTCF and buried the Ag grids with 150 nm thick PEDOT/PSS coating.9 Adopting the coated FTCF for front electrodes, they prepared organic photovoltaic cells. Kim and his colleagues mixed two dispersions of PEDOT/PSS and Ag NWs together and coated the mixture on poly(ethylene phthalate) (PET) film.10 After drying, the Ag NWs were interconnected with PEDOT chains and hybrid transparent conductive film was obtained. The hybrid FTCFs have better optoelectronic properties than that with Ag NW network or PEDOT/PSS coating alone. The power conversion efficiency of the photovoltaic cells deposited on this hybrid FTCF was similar to that deposited on conventional ITO FTCF. Cai and Chen filled the Ag grids of FTCF with PEDOT 2


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synthesized in situ.11 They spin-coated ferric p-toluene-sulfonate (Fe(OTs)3) solution on Ag-grid FTCF and exposed the film with Fe(OTs)3 coating to EDOT vapor at 55 oC. After chemical oxidative polymerization, a 50 nm thick PEDOT coating was synthesized on the Ag grids. They built organic photovoltaic cells on the hybrid PEDOT/Ag-grid FTCF and compared the stability with that deposited on PEDOT/PSS coated Ag-grid FTCF. They found that the cells built on the hybrid PEDOT/Ag-grid electrodes exhibited better stability. PEDOT is an intrinsically conducting polymer and is believed a good alternative to ITO for novel FTCF.4,6,12 But the electrical conductivity and processing ability of a polymer are mutually exclusive because electrical conduction requires π-conjugated molecular chains with rigid planar conformation, whereas the processing ability is associated with flexible coil chains with twisted configuration.13 Though PEDOT can be synthesized conveniently by chemical oxidative polymerization with ferric salts, bulk PEDOT is neither fusible nor soluble. It is difficult to convert virgin PEDOT into thin films. Baytron P, an aqueous dispersion of PEDOT/(PSS) complexes, is the first commercialized conducting polymer developed by Bayer A G. This dispersion can be converted to conductive films conveniently by coating14 and provides a solution to the problem of PEDOT film formation. However, the film contain nonconductive PSS component; the planar PEDOT molecules may be distorted during drying. The obtained PEDOT/PSS coatings exhibit low electrical conductivity, though the conductivity can be improved by adding polar solvents to the dispersion and annealing the coating at elevated temperature.14 Additionally, the PSS component absorbs moisture strongly and causes corrosion in device assemblies, bringing about reliability problem.7,15 Though PEDOT/PSS dispersion has demonstrated the applications of PEDOT film as electrode material in various optoelectronic devices, it has rarely been used in commercial products. Recently, Lee et al removed excessive PSS from PEDOT/PSS coating with sulfuric acid and recrystallized the PEDOT component at elevated temperature, they enhanced the conductivity more than two orders of magnitude to around 4000 S/cm,16 which is comparable to that of ITO coating on polymeric films. In order to avoid the processing problem of PEDOT film, many researchers attempt to convert EDOT monomers to PEDOT films on substrates directly. The explored methods include direct polymerization,13,17 adsorption in polymerizing solution,18,19 chemical vapor deposition (CVD),20,21 vapor phase polymerization (VPP)22,23 and liquid phase depositional polymerization (LPDP).24, 25 Of them, CVD and VPP have attracted much attention because they give PEDOT films with high conductivity and transmittance. 3



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Gleason et al mounted silicon wafers in a closed chamber and delivered EDOT and Br2 vapors into the chamber.20 At substrate temperature 100 oC, PEDOT coating with conductivity 350 S/cm was synthesized. With vaporized FeCl3 as gaseous oxidant, they got similar results also. 21 But when ferric p-toluene-sulfonate Fe(OTs)3 was used as the source of gaseous oxidant, the experiment failed because Fe(OTs)3 decomposed before vaporized. With MoCl5 as the source of gaseous oxidant and substrate temperature 150 oC, Parsons et al prepared PEDOT coating with conductivity above 3000 S/cm.26 In CVD, however, polymeric substrates may be damaged due to high operation temperature. Kim et al adopted VPP to prepare PEDOT coating.22 They exposed PET film with FeCl3 coating to EDOT vapor at 40 oC and got transparent PEDOT/PET films with conductivity above 100 S/cm. Madl et al spin-coated Fe(OTs)3 solution with pyridine retardant on poly(ethylene naphthalate) (PEN) film and exposed the film to EDOT vapor at 50 oC. They obtained PEDOT/PEN films with conductivity about 600 S/cm and transmittance above 94 %.18 Winther-Jensen investigated the effect of basic retardants on the conductivity of PEDOT synthesized by VPP.27 At 1:2 mole ratio of pyridine to Fe(OTs)3, they prepared transparent PEDOT/PET films with conductivity over 1000 S/cm. Fabretto et al investigated VPP comprehensively.28-32 After optimized the formula of oxidants, the humidity in polymerization chamber and the parameters for polymerization, they synthesized PEDOT coating with conductivity above 3400 S/cm.32 In VPP, gaseous EDOT monomers settle on substrate continually and join one after another to construct PEDOT molecules through coupling of EDOT cationic radicals.23,

32

The monomer

radicals are liable to adjust their positions to meet the orientation of rigid planar oligomers. Thereby, VPP gives PEDOT with longer conjugation and less distortion than direct polymerization, consequently, higher electrical conductivity and optical transmittance.32 However, VPP has three inherent drawbacks. Firstly, operation under vacuum is not feasible for mass production. It is a challenging task to maintain the homogeneity of EDOT vapor in large vacuum chamber.13,

31

Secondly, VPP is very sensitive to humidity. Moisture does benefit the deprotonation of cationic EDOT dimers and the formation of conjugative PEDOT molecules.28,31 However, moisture will promote the hydration and crystallization of ferric salt oxidants. This may lead to pinholes on PEDOT coating. Last, solid ferric oxidants are acidic enough to catalyze addition polymerization of EDOT, which results in non-conjugated chain elements in PEDOT.23 In VPP, only chamber humidity, oxidant formula and reaction conditions are controlled tightly, high quality PEDOT coating could be synthesized. 4


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To overcome the drawbacks of VPP, liquid phase depositional polymerization (LPDP) has been investigated in this laboratory.24,

25

PI film with FeCl3 coating was suspended in EDOT

trichloromethane solution to synthesize PEDOT coating. It is believed that wet chemistry is suitable for wide film and roll to roll process. Also, EDOT solvent could prevent ferric oxidants from hydration and crystallization. Furthermore, EDOT solvent would dilute ferric oxidants and alleviate the acidic driven addition polymerization of EDOT. Actually, once substrate with ferric oxidant coating is inserted in EDOT solution, the ferric oxidant diffuse into the stagnant layer over the substrate and initiate chemical oxidative polymerization of EDOT. As the polymerization propagates, EDOT oligomers become insoluble and adhere to the substrate; meanwhile, the monomers in solution phase diffuse into the stagnant layer continually and join with the oligomer one after another, thus, build up long conjugative PEDOT chains on the substrate. But in trichloromethane solution, some Fe+3 might diffuse into EDOT solution as the content of preformed FeCl3 was high and initiated the chemical oxidative polymerization in solution phase. The sheet resistance of prepared PEDOT/PI films were in the magnitude of 103 Ω/□ only.24 To alleviate the escape of preformed oxidants, peroxyacid groups were introduced to PI surface by H2O2 oxidation.25 The peroxyacid converted ferrous ions to ferric ions continually, thereby, enhanced the efficiency of preformed FeCl3. PEDOT/PI films with sheet resistance about 400 Ω/□ have been synthesized. Here, LPDP has been used to fabricate FTCF. PET film was adopted for transparent substrate and Fe(OTs)3 was selected as oxidant. To prevent the preformed oxidant from escaping, non-polar petroleum ether was selected as EDOT solvent. The effects of reaction conditions on microscopic structures and optoelectronic properties of synthesized PEDOT coatings were investigated. Also, the feasibility to create conductive patterns on PEDOT coating by direct VUV irradiation was evaluated.

2．．Experimental 2.1 Raw materials and chemicals Transparent substrate is PET film (Kolon KP 185 PET). Oxidant was 55 % ferric p-toluene-sulfonate (Fe(OTs)3) n-butanol solution (Shenzhen Capchem Technology, OX-DO55). Monomer 3, 4-ethylenedioxythiophene (EDOT, 99 %) was purchased from Zhengzhou Alfachem. n-Butanol was AR grade product of Jiangsu Enox Chemistry. Petroleum ether (boiling 90-120 oC) 5



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and absolute ethanol were AR grade products of Tianjin Fuyu Chemistry. All other chemicals were AR grade and used as received without further purification. 2.2 Process outline PET film was irradiated with 172 nm VUV for surface modification and dipped in Fe(OTs)3 n-butyl alcohol solution to coat Fe(OTs)3 oxidant. After dried, the PET film with Fe(OTs)3 coating was suspended in EDOT petroleum ether solution to synthesize PEDOT coating in situ. After post treatment, the PEDOT coating was irradiated with 172 nm VUV through photo mask to create conductive patterns. Figure 1 show the schema of experiment procedures. VUV Irradiation

PET

Drying

Post treatment

Fe(OTs)3 solution

EDOT solution

VUV Mask

PEDOT/PET Patterned PET

Figure 1. Schema for fabricating PEDOT transparent electrodes on PET film. 2.3 VUV Irradiation Osram DBD-20 Xe excimer (172 nm) lamp was used as the source of VUV radiation. The lamp house has a 68×135 mm irradiating window with output (VUV radiance) about 8 mW/cm2 referring to the lamp specifications. Before powered on, the lamp house was purged with nitrogen gas. Specimens were laid 2 mm away from the irradiating window. For surface modification, 30×35 mm PET sheets were irradiated with the excimer lamp in air for 4 minutes. For patterning, PEDOT coatings were covered with photo mask (aluminium foil with opens) and irradiated with the excimer lamp at ambient condition for different time periods. 2.4 Formation of Fe(OTs)3 oxidant coating VUV modified PET were inserted in 80 mmol/L Fe(OTs)3 n-butanol solution. After immersed for 10 minutes, the PET sheet were taken out and dried in oven at temperature 40 oC for 3 minutes. A uniform Fe(OTs)3 coating formed on the PET surface and the Fe(OTs)3 content was about 1.66 mmol/m2 as determined by iodometry method. 33 2.5 Synthesis of PEDOT coating PET films with preformed Fe(OTs)3 coating were suspended in 80 mmol/L of EDOT petroleum ether solution at set temperature. After immersed for a set time period, the PET films were taken out and washed with DI water and absolute ethanol to remove un-reacted monomers and 6


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oxidant residues. Finally, the PEDOT/PET sheets were dried in oven at 60 oC. For post-oxidation, once PEDOT/PET sheets were taken out from EDOT solution after LPDP, they were inserted in 20 mmol/L of Fe(OTs)3 n-butanol solution at 60 oC for 15 min, then washed and dried. 2.6 Characterization of PEDOT coating The surface compositions of PET films after suspended in EDOT solution were analyzed with BRUKER VECTOR 33 FTIR spectroscope in reflective mode. The thicknesses of the PEDOT coatings were determined with Acer View 34T α-step 500 Profiler. The XPS spectra were acquired on Thermo Fisher X-ray Photoelectron Spectroscope (XPS) with Al Kα radiation below 4.0×10-9 torr. The energy scale was referred with C1s peak of phenyl at 284.6 eV. The doping degree of PEDOT coating were determined based on the fitting components of S2p bind energy.34, 35 The UV-vis spectra of PEDOT/PET films were examined on Yoke UV756 CRT10008 Uv-vis spectroscope with PET film as control. The value at wavelength 550 nm on transmission spectrum was taken as the transmittance of the sample. The sheet resistances were measured with Four Probe Tech RTS-8 four-point probes resistivity measurement system. The instrument was equipped with spring probe and the needles are spaced 1.0 mm apart. For each sample, five locations were measured and the average was reported.

3. Results and discussions 3.1 Synthesis of PEDOT coating in-situ Virgin PET film possesses poor wetting ability. After dipping coating, uneven Fe(OTs)3 spots appeared on the PET film.33 To improve the wetting ability, PET sheet was irradiated with Xe excimer lamp before Fe(OTs)3 coating. After irradiated in air for a couple of minutes, the PET sheet became hydrophilic; the water contact angle dropped from 80 to 30 degree, while the haze and transmittance of the PET sheet remained intact. Actually, the emissions of Xe excimer lamp focus around 172 nm and possess photonic energy about 7.2 eV.36, 37 The energetic radiation can cause photolysis and photo-oxidation of organic materials efficiently and introduce hydroxide and carboxylic groups onto surfaces rapidly, thereby, enhance the surface energy and wetting ability of polymeric films without impairing the optic property.33 After PET sheets were exposed to the 172 nm radiation and dipped in Fe(OTs)3 n-butanol solution, the sheet looked light brown uniformly. SEM revealed that Fe(OTs)3 oxidant had covered the PET surface evenly. Iodomtry analysis indicated that the content of coated Fe(OTs)3 was 1.66 mmol/m2. 33, 38 7



As PET sheet with Fe(OTs)3 coating was suspended in EDOT petroleum ether solution, the colour of the sheet turned blue gradually. In contrary, the EDOT solution remained colourless and transparent. The experiment could run smoothly and repeatedly from 30 to 70 oC though the colour changed faster at higher temperature. After the PET sheet were taken out from EDOT solution, washed with ethanol and dried, they looked pale blue and became conductive. The sheet resistance were below 103Ω/ and the transmittance in visible range were above 70 %, as shown in Figure 2. On the ATR-FTIR spectra of the films (ref Fig. S1 in Support Information), absorbance band around 970 cm-1 from C-S-C vibration of PEDOT could be identified; 38, 39 also, the absorbance band around 1537 cm-1 and 1335 cm-1 from vibration of conjugative C=C and C-C in PEDOT chains could be seen clearly. The above results indicate that PEDOT coating can be synthesized by suspending PET film with Fe(OTs)3 coating in EDOT petroleum ether solution. The ferric ions from adsorbed Fe(OTs)3 will not enter the solution phase and oxidize EDOT in solution phase. 100

1 2

90 80 70

transmittance(%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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60 50 40 30 20 10 0 400

500

600

700

800

900

wavelength(nm)

Figure 2. Transmission spectra and appearance of PEDOT/PET films synthesized by liquid phase depositional polymerization of EDOT. 3. 2 Effect of polymerization temperature PET sheets with Fe(OTs)3 coating were suspended in EDOT petroleum ether solution at set temperature for different time periods. The sheet resistances of the synthesized PEDOT/PET films were measured with four-point probe. As immersing time prolonged at a set temperature, the sheet resistance decreased continuously at beginning but levelled off after a certain time period. The higher the polymerization temperature was, the shorter the time period to level off was, as listed in Table 1. The effect of polymerization temperature on the optoelectronic properties and thickness of synthesized PEDOT coatings were plotted in Figure 3. As polymerization temperature increased from 30 to 70 oC, the transmittance of the coating increased from 82 % to 86 % 8


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Table 1. Properties of PEDOT coating synthesized by liquid phase depositional polymerization of EDOT at different temperature o

Polymerization temperature

C

30

50

60

70

Adsorbed Fe(OTs)3

mmol/m2

1.66

1.66

1.66

1.66

Polymerizing time Sheet resistance

min Ω/

360 890

60 600

30 330

12 380

Coating thickness Electrical conductivity Optical transmittance

nm S/cm %

48 230 82

53 310 84

110 290 84

67 400 86

Coating adhesion Doping degree

grade %

2B 14

2B 28

2B 31

2B 32

monotonously, as seen in Figure 3a. In contrary, the electrical properties did not change monotonously. The sheet resistance descended from 900Ω/

to 330Ω/

as the temperature

increased from 30 to 60 oC; however, as the temperature increased further to 70 oC, the sheet resistance did not decrease but increased a little. The sheet resistance got extremum at polymerization temperature 60 oC.

a

85 80

800 600

75 70

transmittance sheet resistance

65

400

60 30

40

50

60

70

Reaction temperature (℃)

500

160

b

thickness conductivity

conductivity (s/cm)

1000

90

thickness (nm)

1200

transmittance (%)

sheet resistance (ohm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


400

120

300 200

80

100

40

0

30

40

50

60

70

Reaction temperature (℃)

Figure 3. Effect of polymerization temperature on PEDOT/PET film in LPDP; a): transmittance and sheet resistance and b): coating thickness and electrical conductivity. The thickness of PEDOT coatings were measured with α-step Profiler and the electrical conductivity were calculated.18 Figure 3b shows the variation of coating thickness and electrical conductivity with polymerization temperature. As seen in Figure 3b, the coating thickness increased with temperature from 30 to 60 oC. As the temperature increased to 70 oC further, however, it did not increase further but decreased from 100 nm to 65 nm. Anyway, the electrical conductivity of the coating increased with polymerization temperature in the range from 30 to 70 o

C. 9



PEDOT coatings synthesized at different temperatures were analyzed with XPS and Figure 4 shows the obtained spectra of S2p binding energy. As seen from Figure 4, the binding energy could be deconvoluted in four components，peaking at 163.5, 165.0, 167.0 and 168.5 eV. The fitting components at 163.5 and 165.0 eV were attributed to S2p3/2 and S2p1/2 of PEDOT respectively,40,41 while the components at higher binding energy were attributed to sulfonic groups: the component at 167.0 eV was ascribed to toluene-sulfonic anions that associated with thiophene cations of oxidized PEDOT (PEDOT+-OTs-), and that at 168.5 eV was ascribed to residual Fe(OTs)3 and free toluene-sulfonic acid. Because the associated toluene-sulfonic anions match the charged thiophene rings of oxidized PEDOT, the doping degree of PEDOT can be estimated according to the signal of PEDOT+-OTs- around 167.0 eV.41 From the area ratio of 167.0 eV component to the sum of 163.5 and 165.0 eV components, the doping degree were calculated and the values for the samples were listed in Table 1. As seen from Table 1, the doping degree increased from 14 % to 32 % as polymerization temperature increased from 30 to 70 oC. 3000

3000

PEDOT-S2p3/2 PEDOT-S2p1/2

2000 1500

PEDOT-OTs

1000

PEDOT-S2p3/2

2500

intensity(cps)

intensity(cps)

S2p-50℃

S2p-30℃

2500

-

OTs

PEDOT-S2p1/2 2000

PEDOT-OTs

1500

-

1000

OTs

500

500

0 155

0 155

160

165

170

175

160

165

170

175

binding energy(eV)

binding energy(eV)

(a)

(b) 3000

3000

S2p-60℃

2500

PEDOT-S2p3/2

S2p-70℃

PEDOT-S2p3/2 PEDOT-S2p1/2

2500

intensity(cps)

PEDOT-S2p1/2

intensity(cps)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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2000

PEDOT-OTs

1500

-

OTs

1000

2000

PEDOT-OTs

1500 1000

-

OTs

500

500 0 155

160

165

170

175

0 155

160

binding energy(eV)

(c)

165

170

175

binding energy(eV)

(d)

Figure 4. XPS spectra and fitting components of S2p binding energy for PEDOT coating synthesized by LPDP of EDOT at temperature, a): 30 oC; b): 50 oC; c): 60 oC and d): 70 oC. It is well known that the photon absorption of EDOT for π→π* jump is around 290 nm. 39,42,44 After polymerization, the π→π* absorption of thiophene rings should move towards long wavelength because the conjugation range extends and energy band gap decreases.39 For modelled EDOT oilgomers, the π→π* transition occurred from near UV to blue region, depending on the 10


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continuous conjugative length;42 as continuous conjugative length increased, the absorption red-shifted. For PEDOT synthesized by VPP, the absorbance of neutral conjugative chains normally peaked around 570 nm.39,41 After oxidization doping, the absorption extended to near infrared region as the band gap decreased further. The photon absorption of PEDOT coatings synthesized at different temperatures were examined with spectroscope and Figure 5 shows the obtained UV-vis-NIR spectra. As seen in Figure 5, for all the samples, the absorbance below 450 nm was low and it ascended after 480 nm. The increment became smaller after 780 nm and appeared levelling off after 900 nm. The strong absorption in near infrared region in Fig 5 demonstrated that some thiophene rings of PEDOT had been oxidized and charged for all the samples. Additionally, one may have noticed that the absorbance below 450 nm varied with polymerization temperature. Though the coating thickness increased with increasing polymerization temperature (ref Table 1), the absorbance below 450 nm decreased with the increase of temperature. Since the absorption below blue comes from the π→π* transition of short conjugative chains,42 the UV-vis-NIR spectra in Figure 5 indicated that the PEDOT coating synthesized at higher temperature possessed fewer short conjugation. In liquid phase depositional polymerization of EDOT, increasing polymerization temperature will depress the short conjugative chains or conjugative defects and enhance the doping degree. a

0.4

b c d

0.3

abs

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.2

0.1

400

500

600

700

800

900

1000

wavelength (nm)

Figure 5. UV-vis-NIR spectra of PEDOT coatings synthesized by liquid phase depositional polymerization of EDOT at temperature, a): 30 oC; b): 50 oC; c): 60 oC and d): 70 oC. Gleason et al investigated the effect of substrate temperature on PEDOT coating synthesized by CVD.20,21 They found that the conjugative length, doping degree, transmittance and conductivity increased with substrate temperature. They believed that higher temperature would benefit oxidation reaction of EDOT and ordering package of PEDOT chains. Here, the obtained results in LPDP are consistent with those obtained in CVD. In LPDP, actually, as polymerization 11



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temperature increases, the disassociation of Fe(OTs)3 should increase, resulting in a content ascension of toluene-sulfonic anions (OTs-1) in the stagnant layer. The OTs-1 anions can not only neutralize the charge of oxidized thiophene rings but also coordinate with EDOT oligomers and improve the solvation. These will benefit the chemical oxidation polymerization of EDOT. Therefore, as polymerization temperature increased, the amount of short conjugative chains or conjugative defects decreased, whereas the oxidation state or doping level increased. On the other hand, however, the molecular kinetic energy and Brownian motion increase with the increase of temperature; also, solvation prevents EDOT oligomers from sinking. Above a certain reaction temperature, some EDOT oligomers may escape from the stagnant layer and enter the solution phase. The escaped oligomers hardly attach to PET surface and contribute to the PEDOT coating. In LPDP, polymerization temperature affects not only reaction rate but also solvation, diffusion and deposition. For LPDP in petroleum ether solution, though the conductivity of obtained PEDOT ascended with polymerization temperature till 70 oC, the sheet resistance of obtained PEDOT coating got minimum at 60 oC because the coating thickness got maximum at this reaction temperature. 3.3 Effect of imidazole content The C=C double bond of EDOT is able to participate in an acidity driven addition polymerization, which results in non-conjugated chain elements in PEDOT.13, 18 To depress the acidity driven side reaction in chemical oxidative polymerization of EDOT, organic bases are normally incorporated to ferric oxidant solution.18, 27 In the present work, some imidazole was added to Fe(OTs)3 solution; PET sheets were dipped in this solution to adsorb Fe(OTs)3 with imidazole together and then suspended in EDOT solution at 60 oC for liquid phase depositional polymerization. The effect of imidazole concentration in Fe(OTs)3 solution on the structures and properties of obtained PEDOT coatings were investigated. The added imidazole not only retarded the polymerization of EDOT, but also affected the optoelectronic properties of resultant PEDOT, as shown in Figure 6. The transmittance increased with imidazole concentration, as seen from Figure 6a. At 30 mmol/L of imidazole, the transmittance approached 90 %. Compared to that without imidazole, the transmittance was 7 % higher. The electrical properties of resultant PEDOT varied with imidazole concentration also. Without imidazole retardant, the sheet resistance of PEDOT coating was 330Ω/ . The sheet resistance descended with increasing imidazole content at beginning and it reached 230Ω/ at 10 12


500

thickness (nm)

90 80

400

70

300 200 0

10

20

transmittance 60 sheet resistance 50 30 40

conductivity thickness

b

250

conductivity (s/cm)

transmittance (%)

a

400

300

100

600

300

200

200

150

100

100 50 0

10

20

30

40

Imidazole content (mmol/L)

Imidazole content (mmol/L)

Figure 6. Effect of imidazole concentration in Fe(OTs)3 solution on synthesized PEDOT/PET in LPDP at 60 oC; a): transmittance and sheet resistance and b): coating thickness and electrical conductivity. mmol/L, as seen from Fig 6a. However, the sheet resistance did not decrease continually but increased as more imidazole was added. Similarly, the electrical conductivity increased with imidazole concentration at beginning but it decreased as the concentration was above 10 mmol/L, as seen from Figure 6b. The conductivity got maximum 350 S/cm at 10 mmol/L. Compared to that without imidazole, the sheet resistance decreased 100Ω/ (30 %) and the conductivity increased 50 S/cm (20 %)；also, the transmittance increased 5 %. Figure 7 shows the UV-vis-NIR spectra of synthesized PEDOT coatings at different imidazole concentrations. As shown in Figure 7, at imidazole concentration below 30 mmol/L, the absorbance of PEDOT below 450 nm decreased with increasing imidazole concentration though the coating thickness increased (ref. Fig 6b); also, the whole spectrum seemed to shift towards long wavelength. Since the absorption below 450 nm comes from the π→π* transition of short conjugative segments 0.42

b

a

0.35

d

0.28

abs

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


sheet resistance (ohm)

Page 13 of 21

c 0.21

e 0.14 0.07 0.00 400

500

600

700

800

900

1000

wavelength(nm)

Figure 7. UV-vis-NIR spectra of PEDOT coatings synthesized in liquid phase depositional polymerization; a): without imidazole and with imidazole b): 5 mmol/L; c): 10 mmol/L; d): 30 mmol/L and e): 40 mmol/L. 13



Page 14 of 21

of PEDOT,21, 42 The UV-vis-NIR spectra in Figure 7 demonstrated that the added imidazole could depress the generation of conjugative defects or short conjugative chains and improve the continuous conjugative length in liquid phase depositional polymerization of EDOT. XPS analysis revealed that the fitting component of S2p binding energy at 167.0 eV became much smaller after 10 mmol/L of imidazole was added (ref Fig. S2 in Supporting Information). The calculated doping degree decreased from 31 % to 21 %. The added imidazole reduced the oxidation state of PEDOT coating greatly. In an experiment on adsorption behaviour of PEDOT film, Fabaretto and Evans et al also found that amines could reduce the oxidation state of PEDOT film.43 The reduction reaction was attributed to the transfer of active hydrogen N-H from amines to charged thiophene ring of oxidized PEDOT molecules. In LPDP, though imidazole depressed the formation of conjugative defects and improved the continuous conjugative length of resultant PEDOT, it reduced the doping degree, the amount of charge carriers. Therefore, the sheet resistance and electrical conductivity of PEDOT coatings got extremum as imidazole concentration increased. Only at proper imidazole concentration, the optoelectronic properties of synthesized PEDOT coating can be improved greatly. 3.4 Effect of post oxidation After suspended in EDOT petroleum ether/acetonitrile solution at 60 oC for 20 mintes, the synthesized PEDOT/PET films were taken out from EDOT solution and immediately inserted in 20 mmol/L of Fe(OTs)3 n-butanol solution at 60 oC for post oxidation. The effects of post oxidation on the microscopic structure and optoelectronic properties of the PEDOT coating were investigated. Post oxidation improved the optoelectronic properties of PEDOT coating strikingly, as seen in Table 2. Before post oxidation, the transmittance, sheet resistance and electrical conductivity are Table 2. Property of PEDOT/PET synthesized by LPDP with and without post oxidation *Post oxidation Optical transmittance Sheet resistance Coating thickness Electrical conductivity Doping degree Coating adhesion

% Ω/ nm S/cm % Grade

no

yes

81 240

84 140

110 400 18 4B

80 770 28 4B

*Post oxidation in 20 mmol/L Fe(OTs)3 butanol solution at 60 oC for 15 minutes. 14


Page 15 of 21

81 %, 240Ω/ and 400 S/cm, respectively; after post oxidation, they changed to 84 %, 140Ω/ and 770 S/cm, improved 3 %, 40 % and 93 %, respectively. The achieved transmittance and sheet resistance are comparable to those of commercial ITO FTCF. Figure 8 shows the UV-vis-NIR spectra of PEDOT coatings before and after post oxidation. As shown in Figure 8, after post oxidation, the absorbance below 450 nm decreased from 0.13 to 0.09; meanwhile, the absorption spectrum shifted about 50 nm towards long wavelength. The reduction of absorbance below 450 nm and red-shift of spectrum indicated that short conjugative chains decreased and long conjugative chains increased after post oxidation. Post oxidation removed short conjugative chains and increased the continuous conjugative length of PEDOT 0.5

0.4

Abs

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


b

0.3

0.2

a

0.1 400

500

600

700

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900

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wavelength (nm)

Figure 8. UV-vis-NIR spectra of PEDOT coating synthesized by LPDP and a): before and b): after post oxidation in 20 mmol/L Fe(OTs)3 butanol solution at 60 oC for 15 minutes. coating. XPS analysis revealed that the fitting component at 167.0 eV increased obviously after post oxidation (ref. Fig. S3 in Supporting Information). This indicated the amount of toluene-sulfonic anions associated with PEDOT cations (PEDOT+-OTs-) increased, i.e. a raise of oxidation state in PEDOT coating. According to the area ratio of the fitting components, the doping degree was calculated to be 28 %, increasing 10 % compared to that without post oxidation. In chemical oxidative polymerization of EDOT, PEDOT molecule is constructed by repeating the sequential reactions: oxidation of the thiophene rings, coupling of cationic radicals and deprotonation of cationic dimmers.13,18,23 As EDOT multimer molecules grow, the oxidation potential of the thiophene ring decreases because the π-conjugation become wider. In solution polymerization, it is relative easy to achieve long PEDOT molecules provided that there are sufficient oxidants in the solution because EDOT oligomers tend to join each other. In LPDP, however, the distribution of ferric ions is not even; the concentration of ferric ions decreases away from the substrate. The top layer of PEDOT coatings may consist of PEDOT molecules formed 15



under insufficient oxidants that have low molecular weight or low oxidized state. As these EDOT oligomers and low oxidized macromolecules are not washed off completely, they will deteriorate the optoelectronic properties of the coatings. As PEDOT coating was immersed in Fe(OTs)3 solution just after liquid phase depositional polymerization, the EDOT oligomers and low oxidized macromolecules would react with ferric ions continually; consequently, the amount of EDOT oligomers decreased and the oxidized state of PEDOT coating increased, thereby, the optoelectronic properties of the coating increased strikingly. 3.5 Effect of VUV irradiation on conductivity Synthesized PEDOT coatings were covered with an aluminium foil with opens and irradiated with Xe excimer lamp in air for different time periods. The sheet resistances of the irradiated portions and the shadowed portions were measured. Figure 9 shows the variation of the sheet resistance of irradiated portions with irradiating time. The sheet resistance of the virgin PEDOT coating was about 200Ω/ . The sheet resistance ascended as irradiating time increased, as seen in Figure 9. At irradiating time 6 minutes, the sheet resistance ascended above 2000Ω/ . After irradiated for 10 minutes, the sheet resistance reached 104Ω/ . Thereafter, the sheet resistance jumped as irradiating time prolonged, and the irradiated portions could become nonconductive. In contrary, the sheet resistance of the portions shadowed by aluminium foils did not change significantly. sheet resistance (kilo ohm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 21

100 80 60 40 20 0 0

300

600

900

1200

1500

Irradiating time (s)

Figure 9. Variation of sheet resistance of PEDOT/PET films with VUV irradiating time in ambient environment. The photonic energy of radiations from xenon xcimer lamp is about 7.2 eV. It is much higher than the bond energy of C-C bond (3.7 eV), C-F bond (5.0 eV) and oxygen O2 molecule (5.1 eV). 36, 37, 45

As PEDOT coating is irradiated with xenon excimer lamp in air, the energetic VUV radiation

will cleave the covalent bonds of PEDOT and destroy the conjugative structure of PEDOT. 16


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Therefore, the sheet resistance of the PEDOT coating increased with the increase of irradiating time. During VUV photolysis of polymers, macromolecular free radicals would be generated. Meanwhile, the energetic 172 nm VUV radiation is able to split O2 molecules and brings about excited oxygen atoms O (1D). The aggressive atomic oxygen would oxidize the macromolecular free radicals. Thereby, the 172 nm VUV radiation converted the polymeric fragments to evaporable pieces, just as occurs in surface cleaning with VUV.36,45 Combining photolysis and photo oxidation, 172 nm VUV radiation created conductive patterns on PEDOT coating with the aid of the photo mask. By liquid phase depositional polymerization of EDOT and irradiation with xenon excimer lamp though photo mask, transparent conductive patterns can be fabricated on PET film conveniently.

4. Conclusions 1) Transparent PEDOT coating can be synthesized in situ on PET film conveniently by suspending PET film with Fe(OTs)3 coating in EDOT petroleum ether solution at temperature from ambient to 70 oC. 2) As polymerization temperature increases, the conjugative defects of synthesized PEDOT decrease whereas the continuous conjugative length and doping degree increase; the optical transmittance and electrical conductivity become higher. But at temperature above 60 oC, some EDOT oligomers may diffuse into EDOT solution and do not contribute to PEDOT coating. The coating thickness and sheet resistance get extreme at temperature about 60 oC. 3) Imidazole retardant not only depresses the conjugative defects but also reduce the doping degree of synthesized PEDOT. The electrical conductivity and sheet resistance of PEDOT coating get extremes as imidazole content increases. 4) Post oxidation in Fe(OTs)3 solution eliminates EDOT oligomers on PEDOT coating and enhances the continuous conjugative length and doping degree, thereby, improves the transmittance and conductivity of PEDOT coating greatly. PEDOT/PET film with transmittance 85 % and sheet resistance 140Ω/ can be synthesized by LPDP. 5) 172 nm VUV radiation can turns PEDOT coating from conductive to nonconductive. Transparent conductive pattern can be created on PEDOT coating by direct VUV irradiation through mask without using resist.

17



Page 18 of 21

Supporting Information . Acknowledgment This project was financially supported by GDSTC on Research Grant 2013B010401004 and the authors would like to express their thanks. References [1] Alkhazaili, A.; Hamasha, M. M.; Choi, G. H.; Lu, S. S.; Westgate, C. R. Reliability of thin Films: Experimental Study on Mechanical and Thermal Behavior of Indium Tin Oxide and Poly(3,4-ethylenedioxythiophene), Microelectron. Reliab. 2015, 55, 538–546. [2] Sibinski, M.; Znajdek, K.; Sawczak, M.; Gòrski, M. AZO Layers Deposited by PLD Method as Flexible Transparent Emitter Electrodes for Solar Cells, Microelectronic Engineering 2014, 127, 57-60. [3] Guo, C. F.; Ren, Z. F.; Flexible Transparent Conductors Based on Metal Nanowire Networks, Mater. Today, 2015, 18, 143-154. [4] Angmo, D.; Krebs, F. C. Flexible ITO-Free Polymer Solar Cell, J. Appl. Polym. Sci. 2013, 129, 1-4. [5] Lee, S. M.; Kim, J. H.; Ahn, J. H.; Graphene as a Flexible Electronic Material: Mechanical Limitations by Defect Formation and Efforts to Overcome, Mater. Today, 2015, 18, 336-344. [6] Kim Y. S.; Oh S. B.; Park H. J.; Cho M. S.; Lee Y. K. Highly Conductive PEDOT/Silicate Hybrid Anode for ITO-Free Polymer Solar Cells, Sol. Energ. Mater. Sol. Cells. 2010, 94, 471-477. [7] Jonathon B. D.; Amanda V. E.; Poly(3,4-ethylenedioxythiophene):Polystyrene Sulfonate-Free Silver Nanowire/Single Walled Carbon Nanotube Transparent Electrodes Using Graphene Oxide, Thin Solid Films, 2016, 616, 515–520. [8] Cai, G. F.; Lee, P. S. Highly Stable Transparent Conductive Silver Grid/PEDOT:PSS Electrodes for Integrated Bifunctional Flexible Electrochromic Supercapacitors, Adv. Energ. Mater. 2016, 6 (4), 1501882 , DOI: 10.1002/aenm.201501882. [9] Li, Y. W.; Cui, Z.; Chen, L. W. ITO-Free Photovoltaic Cell Utilizing a High-Resolution Silver Grid Current Collecting Layer, Sol. Energ. Mater. Sol. Cells, 2013,113, 85–89. [10] Kim, Y. S.; Chang, M. H.; Lee, E. J.; Ihm, D. W.; Kim, J. Y. Improved electrical conductivity of PEDOT-based electrode films hybridized with silver nanowires, Synth. Met. 2014, 195, 69-74. [11] Li, Y.; Cai, J. H.; Chen, L. W. Ambient Stable Large-Area Flexible Organic Solar Cells Using Silver Grid Hybrid with Vapor Phase Polymerized Poly(3,4-ethylenedioxythiophene) Cathode, Sol. Energ. Mater. Sol. Cells, 2015, 143, 354–359. [12] Lee, S.; Gleason, K. K. Enhanced Optical Property with Tunable Band Gap of Cross-Linked PEDOT Copolymers via Oxidative Chemical Vapor Deposition, Adv. Funct. Mater. 2015, 25, 85-93. [13] MeFarlane, S. L.; Deore, B. A.; Svenda. N. A One-Step Organic-Solvent Processable Synthesis of PEDOT Thin Films via in-situ Metastable Chemical Polymerization, Macromolecules, 2010, 43, 10241-10245. [14] Palumbiny, C. M.; Heller, C.; Schaffer, C. J.; Korstgens, V.; Santoro, G.; Roth, S. V.; Muller-Buschbaum, Molecular Reorientation and Structural Changes in Cosolvent-Treated Highly Conductive PEDOT:PSS Electrodes for Flexible Indium Tin Oxide-Free Organic Electronics, J. Phys. Chem. 2014, C118, 13598-13606. 18


Page 19 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


[15] Crispin, X.; Jakobsson, F. L. E.; Grispin, A.; Grim, P.C.M.; Andersson, P.; Volodin, A.; VanHaesendonck, C.; Salaneck, W. R.; Berggren, M. The Origin of the High Conductivity of Poly(3,4-ethylenedioxythiophene)−Poly(styrenesulfonate) (PEDOT−PSS) Plastic Electrodes, Chem. Mater. 2006, 18, 4354-4360. [16] Kim, N.; Kee, S.; Lee, S. H.; Lee, B. H.; Kahang, Y. H.; Jo, Y. R.; Kim, B. J.; Lee, K. K. Highly Conductive PEDOT:PSS Nanofibrils Induced by Solution-Processed Crystallization, Adv. Mater. 2014, 26, 2268-2272. [17] Pettersson, L. A. A.; Carlsson, F,; Inganas, O.; Arwin, H, Spectroscopic Ellipsometry Studies of the Optical Properties of Doped Poly(3,4-ethylenedioxythiophene): An Anisotropic Metal, Thin Solid Films, 1998, 313, 356-361. [18] Madl, C. M.; Peter, N. K.; Jessica, G. Piper, L. J. J.; Jones Jr. W. E. Vapor Phase Polymerization of Poly(3,4-ethylenedioxythiophene) on Flexible Substrates for Enhanced Transparent Electrodes, Synth. Met. 2011, 161, 1159-1165. [19] Liang, J.; Ma, Y. H.; Wang F.; Yang, W. T. Flexcible, Highly Transparent, and Conductive Poly(3,4-ethylenedioxythiophene) Composite Films of Nanofibrilar Morphology, Chem. Mater., 2010, 22, 4254-4262. [20] Chelawat, H.; Vaddiraju, S.; Gleason, K. Conformal, Conducting Poly (3, 4-ethylenedioxythiophene) Thin Films Deposited Using Bromine as the Oxidant in Completely Dry Oxidative Chemical Vapor Deposition Process. Chem. Mater., 2010, 22, 2864-2868. [21]

Im, S. G.; Gleason, K. Systematic Control of the Electrical Conductivity of Poly(3,4-ethylenedioxythiophene) via Oxidative Chemical Vapor Deposition Macromolecules, 2007, 40, 6552-6556.

[22] Kim, J.; Kim, E.; Won, Y. S.; Lee, H.; Suh, K. The Preparation and Characteristics of Conductive Poly(3, 4-ethylenedioxythiophene) Thin Film by Vapor Phase Polymerization, Synth. Met. 2003, 139, 485-489. [23] Winther-Jensen, B.; West, K. Vapor-Phase Polymerization of 3, 4-ethylenedioxythiophene: a Route to Highly Conducting Polymers Surface Layers, Macromolecules, 2004, 37, 4538-4543. [24] Zhang, M. J.; Li, J. X.; Liu, A. H.; Guo, B, C,; Preparation of PEDOT Film by Liquid Phase Depositional Polymerization, Polym. Mater. Sci. Eng. 2013, 29(4), 129-132. [25] Li, J. X.; Zhang, M. J.; Liu, J.; Ma, Y. X. Effect of Attached Peroxyacid on Liquid Phase Depositional Polymerization of EDOT over PI Film with Adsorbed Ferric Chloride, Synth. Met. 2014, 198, 161-166. [26] Atanasov, S. E.; Losego, M. D.; Gong, B.; Sachet, E.; Maria, J. P.; Williams, P. S.; Parsons, G. N. Highly Conductive and Conformal Poly(3,4-ethylenedioxythiophene) (PEDOT) Thin Films via Oxidative Molecular Layer Deposition, Chem. Mater. 2014, 26, 3471−3478. [27] Winther-Jensen, B.; Breiby, D. W.; West, K. Base Inhibited Oxidative Polymerization of 3,4-ethylenedioxythiophene with Iron(III) Tosylate, Synth. Met. 2005, 152, 1-4. [28] Fabretto, M.; Zuber, K.; Hall, C.; Murphy, P.; Griesser, H. J. The Role of Water in the Synthesis and Performance of Vapor Phase Polymerized PEDOT Electrochromic Devices, J. Mater. Chem. 2009, 19, 7871–7878. [29] Fabretto, M.; Mueller, M.; Hall, C.; Murphy, P. In-situ QCM-D Analysis Reveals Four Distinct Stages during Vapour Phase Polymerisation of PEDOT Thin Films, Polymer, 2010, 51, 1737-1743. [30] Fabretto M., Autere Jussi-Petteri; Hoglinger D.; Field S.; Murphy P. Vacuum Vapour Phase Polymerised Poly(3,4-ethyelendioxythiophene) Thin Films for Use in Large-Scale Electrochromic Devices, Thin Solid Films, 2011, 519, 2544-2549. [31] Mueller, M.; Fabretto, M.; Evans, D.; Hojati-Talemi, P.; Gruber. C.; Murphy, P. Vacuum Vapour Phase Polymerization of High Conductivity PEDOT: Role of PEG-PPG-PEG, the Origin of Water, and Choice of Oxidant, Polymer, 2012, 53, 2146-2151. 19



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[32] Fabretto, M. V.; Evans, D. R.; Mueller, M.; Zuber, K.; Hojati-Talemi, P.; Short, R. D.; Wallace G. G.; Murphy, P. J. Polymeric Material with Metal-Like Conductivity for Next Generation Organic Electronic Devices, Chem Mater. 2012, 24, 3998-4003. [33] Ma, Y. X.; Li, J. X.; Effect of VUV Irradiating PET on Liquid Phase Deposition Polymerization of EDOT and Preparation of Transparent Conductive PEDOT/PET Films, Polym. Mater. Sci. Eng. 2015, 31(7), 34-38. [34] Zotti, G.; Zecchin, S.; Schiavon, G.; Louwet, F.; Groenendaal, L.; Crispin, X.; Osikowicz, W.; Salaneck, W.; Fahlman, M. Electrochemical and XPS Studies toward the Role of Monomeric and Polymeric Sulfonate Counterions in the Synthesis, Composition, and Properties of Poly(3,4-ethylenedioxythiophene), Macromolecules, 2003, 36, 3337-3344. [35] Spanninga, S. A.; Martin, D.; Chen, Z. X-ray Photoelectron Spectroscopy Study of Counterion Incorporation in Poly(3,4-ethylenedioxythiophene) (PEDOT) 2: Polyanion Effect, Toluenesulfonate, and Small Anions, J. Phys. Chem. 2010 ,114, 14992-14997. [36] Kogelschatz, U.; Esrom, H.; Zhang, J. Y.; Boyd, I. W. High-Intensity Sources of Incoherent UV and VUV Excimer Radiation for Low-Temperature Materials Processing, Appl. Surf. Sci. 2000, 168, 29-38. [37] Sosnin, E. A.; Oppenlander, T.; Tarasenko, V. F.; Application of Capactive and Barrier Discharge Excilamps in Photoscience, J. Photoch. Photobio. 2006, 7, 145-156. [38] Li, J. X.; Ma, Y. X. In-situ Synthesis of Transparent Conductive PEDOT Coating on PET Foil by Liquid Phase Depositional Polymerization of EDOT，Synth. Met. 2016, 217, 185-188. [39] Martin, D. C.; Wu, J. H.; Shaw, C. M.; King, Z.; Spanninga, S. A.; Richardson-Burns, S.; Hendricks, J.; Yang, J. Y. Morphology of Poly(3,4-ethylenedioxythiophene), Polym Rev. 2010, 50, 340-384. [40] T. Y. Kim, C. M. Park, J. E. Kim, K. S. Suh, Electronic, Chemical and Structural Change Induced by Organic Solvents in Tosylate-Doped Poly(3,4-ethylenedioxythiophene) (PEDOT-OTs), Synth. Met. 2005, 149, 169-174. [41] Kim, T. Y.; Kim, J. E.; Suh, K. S. Effects of Alcoholic Solvents on the Conductivity of Tosylate-Doped Poly(3,4-ethylenedioxythiophene) (PEDOT-OTs), Polym. Int. 2006, 55, 80-86. [42] Wasserberg, D.; Meskers, S. C. J.; Janssen, R. A. J.; Mena-Osteriz, E.; Bauerle, P. High-Resolution Electronic Spectra of Ethylenedioxythiophene Oligomers, J. Am. Chem. Soc. 2006, 128,17007-17017. [43] Hojati-Talemi, P. Evans, D. Fabaretto, M. Extending the Utility of Conducting Polymers through Chemisorption of Nucleophiles, Chem. Mater. 2013, 25, 1837-1841. [44] Lv, S. Y.; Li, J. X.; Ma, Y. X. Effect of Acetonitrile Content on Molecular Structures and Optoelectronic Properties of PEDOT Coatings Synthesized in Acetonitrile/Cyclohexane Solutions by Liquid Phase Depositional Polymerization, Polym. Mater. Sci. Eng. 2017, 33(4), 40-46. [45] Li, J. X.; Liu, A. H. Reduction of Copper Oxide Induced by Vacuum Ultraviolet Radiation at Ambient Temperature, J. Electron. Mater. 2011, 40, 2105-2110.

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For Table of Content Study on fabricating PEDOT electrode on PET film by liquid phase depositional polymerization of EDOT and direct patterning with 172 nm VUV radiation Jian-Xiong Li*and Ya-Xiao Ma

VUV Irradiation

PET

Drying

Post treatment

Fe(OTs)3 solution

EDOT solution

VUV Mask

PEDOT/PET Patterned PET

21


Study on Fabricating PEDOT Electrodes by Liquid Phase Depositional

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