Electrical conductivity of polymer blends of poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate): N-methyl-2-pyrrolidinone and polyvinyl alcohol

The goal of this study is to determine the electrically conductivity of the polymers poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate): N-methyl-2-pyrrolidinone (PEDOT: PSS: NMP) and PEDOT: PSS when blended with polyvinyl alcohol (PVA). While the conducting polymers have high conductivity when not blended with PVA, they are brittle and difficult to spin-coat. Thus, the motivation for this study is to develop blends of these two conducting polymers with PVA to produce a material with optimized mechanical properties and that can also be spin-coated. The blends are produced using aqueous preparations of these materials. Mixtures of various weight percentages (wt %) of PEDOT: PSS: NMP and PEDOT: PSS are prepared and spin-coated on glass slides to form thin films. In the blends, the film conductivity increases with increasing content of either PEDOT: PSS: NMP or PEDOT: PSS. For example, 100 wt % of PEDOT: PSS: NMP and 60 wt % of PEDOT: PSS: NMP blended with PVA exhibit conductivities of, respectively, 10 and 4.02 S/cm. In contrast, conductivities of only 0.0525 and 0.000506 S/cm are observed, respectively, for 100 wt % of PEDOT: PSS and 60 wt % of PEDOT: PSS content in the PEDOT: PSS/PVA blends (No NMP). The addition of the NMP enhances the electrical conductivity by two to five orders of magnitude (depending on the amount of PVA in the blend) due to conformational change of PEDOT chains. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonic Acid) (PEDOT:PSS) Conductivity Enhancement through Addition of Imidazolium-Ionic Liquid Derivatives

Here, insignificant conductivity enhancement of PEDOT:PSS through adding different amounts of 2-methylimidazolium ionic liquids into PEDOT:PSS aqueous solutions is reported. Maximum conductivity was reached through 2-methylimidazolium hydrogen sulfate (5 wt.%) addition. It seems that observed conductivity enhancement mainly results from the impact of ionic liquids on the electrical properties and conformational change of PEDOT chains, and through weakening of the electrostatic interactions between PEDOT and PSS. Also, better conductivity was achieved through weak interactions between PEDOT and the PSS chain, which changes the PEDOT conformation and further delocalizes the polarons, as well as changes the electron transport properties.     

Electroconductive paper prepared by coating with blends of poly(3,4‐ethylenedioxythiophene)/poly(4‐styrenesulfonate) and organic solvents

Electroconductive papers were produced by coating commercial base papers with blends of poly(3,4‐ethylenedioxythiophene)/poly(4‐styrenesulfonate) (PEDOT:PSS) and organic solvents. The bulk conductivities of the coated papers were measured using a four‐probe technique. One‐sided and two‐sided coating gave comparable conductivity levels. The presence of sorbitol and isopropanol in the PEDOT:PSS blends did not enhance the bulk conductivity of the coated paper, and with increasing concentrations of these solvents, the conductivity decreased due to dilution of the conducting component. Samples coated with PEDOT:PSS blends containing N‐methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) exhibited a higher conductivity than those coated with pure PEDOT:PSS because of their plasticizing effect and conformational changes of PEDOT molecules indicated by the red shift and disappearance of the shoulder peak at about 1442 cm^?1 in the Raman spectra of the coated samples. EDS imaging showed that PEDOT:PSS is distributed throughout the thickness direction of the paper. Contact angle measurements were made to monitor the hydrophilicity of the paper surface and total sulfur analysis was used to determine the amount of PEDOT:PSS deposited onto the paper. The tensile strength of all the paper samples increased slightly after treatment. Thus, it is demonstrated that enhanced bulk conductivity in the order of 10^?3 S/cm can be achieved by using organic conductive materials and surface treatment techniques. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chemical cross-linking of conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using poly(ethylene oxide) (PEO)

Hybrid films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were prepared with different molecular weights of poly(ethylene oxide) (PEO). The cross-linking reaction between PEO and PEDOT:PSS was performed at high temperature and confirmed by using differential scanning calorimeter (DSC), contact angle measurement, and solid-state ¹H NMR. The effect of chemical reaction on the conductivity and morphology of these hybrid films was studied by using 4-point probe and atomic force microscope (AFM), respectively. As-spun PEO/PEDOT:PSS films have lower electric conductivity due to the addition of nonconductive PEO, and exhibits no molecular weight dependence on conductivity. After chemical cross-linking reaction at high temperature, only PEDOT:PSS films with lowest molecular weight PEO additives show enhanced conductivity with increasing reaction time. AFM result indicates that the heat-treated PEO/PEDOT:PSS hybrid films show grain-like morphology compared to ethylene glycol treated PEDOT:PSS films which shows continuous PEDOT domain. In the present work we demonstrate that the cross-linking reaction can be used to improve the wet stability of PEDOT:PSS nanofiber, showing good water resistance and excellent dimensional stability.     

Ultrafast-laser-treated poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) electrodes with enhanced conductivity and transparency for semitransparent perovskite solar cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is an important organic electrode for solution-processed low-cost electronic devices. However, it requires doping and post-solvent treatment to improve its conductivity, and the chemicals used for such treatments may affect the device fabrication process. In this study, we developed a novel route for exploiting ultrafast lasers (femtosecond and picosecond laser) to simultaneously enhance the conductivity and transparency of PEDOT:PSS films and fabricate patterned solution-processed electrodes for electronic devices. The conductivity of the PEDOT:PSS film was improved by three orders of magnitude (from 3.1 to 1024 S·cm^–1), and high transparency of up to 88.5% (average visible transmittance, AVT) was achieved. Raman and depth-profiling X-ray photoelectron spectroscopy revealed that the oxidation level of PEDOT was enhanced, thereby increasing the carrier concentration. The surface PSS content also decreased, which is beneficial to the carrier mobility, resulting in significantly enhanced electrical conductivity. Further, we fabricated semitransparent perovskite solar cells using the as-made PEDOT:PSS as the transparent top electrodes, and a power conversion efficiency of 7.39% was achieved with 22.63% AVT. Thus, the proposed route for synthesizing conductive and transparent electrodes is promising for vacuum and doping-free electronics.     

以低分子量聚乙烯基苯磺酸钠为模板的聚3,4-二氧乙烯噻吩水分散体的制备及性能

通过RAFT聚合,制备了低分子量的聚乙烯基苯磺酸钠（PSS）;其次以低分子量的聚乙烯基苯磺酸钠为模板制备了聚3,4-二氧乙烯噻吩（PEDOT）：聚乙烯基苯磺酸钠（PSS）水分散体,研究了作为模板的聚乙烯基苯磺酸钠的不同分子量对PEDOT：PSS水分散体结构和性能的影响。结果显示：通过核磁氢谱（¹H NMR）表征,证明成功制备了分子量为3900,4900,9600和18300的聚乙烯基苯磺酸钠。用荧光探针法发现低分子量PSS在水中能形成胶束,临界胶束浓度在10^-6g·ml^-1左右。用四探针表面电阻测试发现,低分子量PSS为模板可明显提高PEDOT薄膜的导电性,最大提高了近3倍。用紫外可见分光光度计（UV）研究发现,以低分子量PSS为模板使PEDOT的透明性有一定的下降,这主要是由于RAFT试剂部分和PEDOT：PSS的相分离造成的。热稳定性的测试表明,低分子量PSS为模板对PEDOT的热稳定性没有明显的影响。     

Cooperative doping in polyaniline-poly(ethylene-3,4-dioxythiophene): poly(styrenesulfonic acid) composite system

Interaction of emeraldine base of polyaniline (PANI) and poly(ethylene-3,4-dioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) in a complex solution is shown to lead to a new polymer complex whose components act to each other to favor an increase in intramolecular conductivity in both PANI and PEDOT backbones. Asymmetric changes in intramolecular conductivity of the polymer mixture have been demonstrated upon addition of PANI to PEDOT:PSS dispersion and vise versa. Complex films cast from the solution revealed a specific spherulite-like morphology and increased conductivity up to one order of magnitude as compared to films of the net PEDOT:PSS, which allowed us to conclude on formation of a qualitatively new system rather than a simple blend of the polymers and the effect of cooperative doping of the components by each other, respectively. The doping efficiency was shown to be strongly dependent on the solvent environment and concentration of the polymers in solutions. It is discussed that the increase in conductivity of the composite system is controlled not only by the direct doping of PANI with PSS, but also by weakening of interaction of PSS with the PEDOT backbone itself as a result of the above doping process.     

Effect of solvent on electrical conductivity and gas sensitivity of PEDOT: PSS polymer composite films

Poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) was blended with polyethylene oxide (PEO) and polyvinyl alcohol (PVA) and composite film was cast. Additional solvents of dimethyl sulfoxide (DMSO) and ethylene glycol (EG) were mixed and their effects on electrical conductivity and structural changes were investigated. The electrical conductivity increased in response to the additional solvent, leading to an increase in the PEDOT ratio relative to the control. PEDOT:PSS/PEO composite film had a much higher electrical conductivity than PEDOT:PSS/PVA. When blended with PEO, the quinoid structure revealed by Raman spectroscopy increased relative to the PVA‐blended case, indicating higher electrical conductivity. The current–voltage response and gas sensitivity showed much better performance in PEDOT:PSS/PEO/DMSO composite film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42628.     

Effects of solvents on the morphology and conductivity of poly(3,4‐ethylenedioxythiophene):Poly(styrenesulfonate) nanofibers

In this study, the effect of solvents on the morphology and conductivity of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) nanofibers is investigated. Conductive PEDOT:PSS nanofibers are electrospun by dissolving a fiber‐forming polymer, polyvinyl alcohol, in an aqueous dispersion of PEDOT:PSS. The conductivity of PEDOT:PSS nanofibers is enhanced 15‐fold by addition of DMSO and almost 30‐fold by addition of ethylene glycol to the spinning dopes. This improvement is attributed to the change in the conformation of the PEDOT chains from the coiled benzoid to the extended coil quinoid structure as confirmed by Raman spectroscopy, X‐ray diffraction, and differential scanning calorimetry. Scanning electron microscopy images show that less beady and more uniform fiber morphology could be obtained by incorporation of ethylene glycol in the spinning dopes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40305.     

Conductivities enhancement of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) transparent electrodes with diol additives

High conductivity, good stability, and high transmittance in the visible region are the three essential requirements for the polymer electrodes used in the optoelectronic devices. It was found that with addition of diols, such as ethylene glycol, diethylene glycol, or poly(ethylene glycol) (PEG), to the poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) emulsion before spin-coating could increase dramatically the conductivities of the resultant PEDOT:PSS thin films from 1 to 90 S cm^?1 while maintain the optical transparency of the modified thin films. With up to ?2.4 V potential applied, the PEDOT:PSS with PEG 200 additive does not show obvious color change, indicating its good electrochemical stability as polymer electrode. Detailed studies on the structures and morphologies of these modified PEDOT:PSS thin films, in comparison to that of PEDOT:PSS without additives were carried out using AFM, Raman, and FTIR to investigate the underlying mechanisms.     

On the mechanism of conductivity enhancement in PEDOT/PSS film doped with multi-walled carbon nanotubes

The results of conductivity investigation of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) thin films doped with different multi-walled carbon nanotubes (MWCNTs) concentrations were studied. The role of MWCNTs as a conductive filler on the mechanism of conductivity enhancement in the composite film was further investigated by X-ray diffraction (XRD), Fourier transform Roman spectroscopy (FT-RM), X-ray photoelectron spectroscopy (XPS) and Atomic force microscopy (AFM). The increase of the conductivity is likely to be due to two effects, the “π-π interaction” effect and the “channel” effect. The former is π-π interaction between the thiophene rings of PEDOT backbone and MWCNTs, and the electronic density transfer occurs from PEDOT to MWCNTs in M-PEDOT/PSS, so that the charge becomes more delocalized on the PEDOT chains. The latter stems from the formation of some conductive MWCNTs channels in the PEDOT/PSS matrix. These two effects can help charge transport and enhance the conductivity of composite films.     

Enhanced thermoelectric performance of poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) with long‐term humidity stability via sequential treatment with trifluoroacetic acid

This paper reports a range of effective sequential chemical processes to enhance the thermoelectric performance of conducting poly(3,4‐ethylenedioxythiophene) films doped with poly(styrene sulfonate) anions (PEDOT:PSS). The electrical conductivity of the PEDOT:PSS films was significantly increased from 0.33 to 3748 S cm^?1 after a series of sequential treatments with trifluoroacetic acid (TFA) while the Seebeck coefficient and thermal conductivity were slightly reduced from 17.5 ± 1.2 to 16.0 ± 1.1 μV K^?1 and 0.537 to 0.415 W m^–1 K^?1 for the pristine film and treated film, respectively, leading to a significant improvement in power factor up to 97.1 ± 5.4 μW m^–1 K^?2. More importantly, around 80% of the electrical conductivity and Seebeck coefficient was retained after 20 days for these TFA‐treated PEDOT:PSS films, revealing the potential for real thermoelectric applications. © 2019 Society of Chemical Industry     

A focus on polystyrene tacticity in synthesized conductive PEDOT:PSS thin films

Poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) is a transparent conductive material and a good candidate for being employed as substitute for indium tin oxide (ITO) in reducing the production costs of organic solar cells. To enhance the performance of organic devices, an improving in the conductivity of PEDOT:PSS is crucial and using the solvent additive rises the electrical conductivity by the optimization of the film morphology. The studies have only focused on the relationship between the electrical conductivity of thin films and the crystallinity of PEDOT, and it is also found that the high conductivity is observed in the highly crystalline samples. This study focused on the effect of tacticity of PS on the conductivity of PEDOT:PSS films. First, atactic and isotactic polystyrenes were sulfonated and the complexes of PEDOT:PSS were synthesized. The N-methylpyrrolidone (NMP), as a secondary dopant, was then added to the complexes and conductivity enhancement was investigated in various annealing times. The obtained films were characterized by atomic force microscopy, X-ray diffraction, four point probe resistivity measurement system, UV–visible spectroscopy, FT-IR, and cyclic voltammetry. The electrical conductivity of PEDOT:iPSS films synthesized by the isotactic polystyrene was ~ 0.68 S/cm and by adding 5 wt% NMP into PEDOT:PSS solution, the conductivity of the annealed thin layers increased more than 10-folds (~ 7.73 S/cm) at an appropriate temperature.     

Enhanced thermoelectric properties of poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate)/copper phthalocyanine disulfonic acid composite films

A series of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)/copper phthalocyanine disulfonic acid (PEDOT: PSS/CuPc-[SO₃H]₂) composite films were prepared by using CuPc-(SO₃H)₂ as the dopant. EG treatment was applied to further improve the thermoelectric properties of PEDOT: PSS/CuPc-(SO₃H)₂ composites. Structural analyses indicated the strong π − π interactions existed between PEDOT: PSS and CuPc-(SO₃H)₂, and led to more ordered regions in the composite films, and benefit the conductivity. CuPc-(SO₃H)₂ can greatly improve the thermoelectric properties of PEDOT: PSS/CuPc-(SO₃H)₂ composite films, which have a Seebeck coefficient of 13.2 μV K⁻¹ and a conductivity of 2.8 × 10⁵ S/m with 20 wt% CuPc-(SO₃H)₂ at room temperature, and the corresponding power factor is 48.8 μW m⁻¹ K⁻², which is almost 6.83 times higher than the PEDOT: PSS films without CuPc-(SO₃H)₂.     

Generating Power Enhancement of Flexible PVDF Generator by Incorporation of CNTs and Surface Treatment of PEDOT:PSS Electrodes

Two approaches are proposed for enhancing the generating power of polyvinylidene fluoride (PVDF) flexible generator by incorporating carbon nanotubes (CNTs) and ethylene glycol (EG) treatment of the poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes. By incorporating CNTs into the PVDF polymer, higher portion of β‐phase PVDF can be obtained, which shows higher piezoelectricity resulting in higher electric charge generating performance. Higher conductivity is also obtained by surface treatment of the PEDOT:PSS electrodes using EG solvent due to the removal of excess PSS in the electrodes. Highly conductive electrode makes effective mobility of charges generated from the CNT/PVDF film, resulting in higher generating performance. Consequently, higher generating performance can be achieved by collaborating the above two approaches.     

Enhanced Thermoelectric Performance of PEDOT:PSS Films by Sequential Post‐Treatment with Formamide

This paper reports a series of sequential post‐treatments using a polar solvent formamide to enhance the thermoelectric performance of poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) anions (PEDOT:PSS). The electrical conductivity of PEDOT:PSS films significantly increases from 0.33 S cm^?1 for the pristine film to ≈2929 S cm^?1 for the treated film and meanwhile the Seebeck coefficient maintains as high as 17.4 µV K^?1, resulting in a power factor of 88.7 µW m^?1 K^?2. Formamide is a polar solvent with a high boiling point of 210 °C and high dielectric constant of 109, and PSS has a good solubility in it. Post‐treatment with formamide causes not only the phase segregation of PEDOT and PSS but also the removal of insulating PSS, therefore leading to the reorientation of PEDOT chains and enhancement in mobility without altering the doping level considerably. The cross‐plane thermal conductivity also reduces from 0.54 to 0.19 W m^?1 K^?1 after the post‐treatment, leading to a figure of merit (ZT) value of 0.04 at room temperature.     

Synthesis of PEDOT:PSS (poly(3,4‐ethylenedioxythiophene))/poly(4‐styrene sulfonate))/ ngps (nanographitic platelets) nanocomposites as chemiresistive sensors for detection of nitroaromatics

Polymer nanocomposites (NCs) are a special class of materials having unique properties and wide application potential in electronics and other diverse areas. In this study, NCs consisting of poly(3,4‐ethylenedioxythiophene)/poly(4‐styrene sulfonate) (PEDOT:PSS) matrix reinforced with graphite nanosheets were fabricated by solution method. The graphite used was functionalized before fabrication of NCs. The functionalized graphite was characterized by transmission electron microscopy (TEM) and Fourier transform Infrared spectroscopy (FTIR) technique. The NCs prepared were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and FTIR technique. The conductivity studies of the prepared NCs were carried out. The prepared NCs films were investigated for the detection of nitrobenzene vapors. The detection mechanism is based on measuring resistivity changes that occur in a NC due to the absorption of nitrobenzene vapors by PEDOT:PSS film. These sensors exhibited excellent response at room temperature when exposed to vapors of nitrobenzene. Sensitivity as high as 18.5% was observed for PEDOT:PSS/NGPs composite. The chemresistor exhibits a fast response (～1.14 min) and good recovery time (～1–2 min). The response of NC to the nitrobenzene vapors is reproducible. POLYM. ENG. SCI., 53:2045–2052, 2013. © 2013 Society of Plastics Engineers     

Electrical conductivity enhancement of spin‐coated PEDOT:PSS thin film via dipping method in low concentration aqueous DMSO

The electrical conductivity of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was enhanced by dipping the thin films prepared by spin coating technique in an aqueous DMSO solution. The low concentration range of DMSO in water between 0–5 vol % was studied in comparison with pure water and pure DMSO. It was found that the electrical conductivity dramatically increased as increasing the concentration of DMSO and reached the constant value of 350 S cm^?1 at 2 vol % of aqueous DMSO solution. This could be explained by the conformational change of PEDOT chains from the coil structure to the linear or expanded coil structure as confirmed by Raman spectra. Further, white patches were obviously noticed on the surface of the films dipped in pure DMSO, indicating the phase separation of conductive PEDOT grains and associated PSS. The sulfur element of the dipped film surface was investigated by XPS. The XPS S2p core‐level spectra displayed that the unassociated PSS was considerably removed from the surface of PEDOT:PSS films dipped in pure water and 2 vol % of aqueous DMSO solution, indicating that the presence of water in the solvents is important to prominently promote the washing effect. Finally, UV–Vis spectra revealed the improved transparency of the films probably owing to the decreased film thickness. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42108.     

Modification of Conductive Polymer for Polymeric Anodes of Flexible Organic Light-Emitting Diodes

A conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), was modified with dimethyl sulfoxide (DMSO) in solution state, together with sub-sequential thermal treatment of its spin-coated film. The electrical conductivity increased by more than three orders of magnitude improvement was achieved. The mechanism for the conductivity improvement was studied at nanoscale by particle size analysis, field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Smaller particle size was observed, resulting in larger contact area and better electrical conductive connections. Connection of conductive PEDOT increased on the surface of the PEDOT:PSS particles, which promoted high conductivity. Flexible anodes based on the modified PEDOT:PSS were fabricated. Flexible organic light-emitting diodes (FOLED) based the polymeric anodes have a comparable performance to those on indium–tin–oxide (ITO) anodes.     

Versatile poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) films on polydimethylsiloxane substrates having random micro ridges: Study of resistive behaviors of a polymer–polymer laminate

Conductive polymers such as poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) or PEDOT:PSS has become increasingly important in present day organic electronics. PEDOT:PSS being a polymer is more durable than metals used in electronics and thus offers greater mechanical flexibility during operation. This article presents results regarding resistive behaviors of blade coated PEDOT:PSS films on polydimethylsiloxane (PDMS) substrate having random micro ridges as a function of axial strain and different temperatures. The average resistance of the blade coated PEDOT:PSS films were found to increase by 1.4 times between 35 and 45% axial strain. The resistances of the films were found to change within the temperature range of 25–230°C without any thermal morphological degradations and the polymer–polymer laminate also showed linear thermal actuation behavior. These results suggest that the blade coated PEDOT:PSS films on PDMS substrates with random micro ridges can be potentially useful in versatile applications like stretchable conductors, thermal actuators, thermoelectric generators, and as heating surfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41235.