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     

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     

Humido-sensitive conducting polymer films and applications to linear actuators

Free-standing films made of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) with various PSS contents were newly prepared by casting water dispersion of the PEDOT/PSS colloidal particles in the presence of an extra PSS. Electrical conductivity, morphology, water vapor sorption, and electro-active polymer actuating behavior of the resulting films were investigated by means of four-point method, atomic force microscope (AFM), sorption isotherm, and electromechanical analyses. The maximum contraction of the film by application of an electric field increased with increasing both PSS content and relative humidity (RH), where the value attained 7% at 70% RH for the film with 93% of PSS. Since the isothermal sorption curve of the film was less dependent on the PSS content, the significant increase of the film contraction was explained by two mechanisms: (i) the extra PSS prevented from hydrogen bonding between adjacent PEDOT/PSS particles that suppressed dimensional changes of the film; and (ii) the higher the RH, the larger the degree of water vapor sorption, which led to the large film contraction by desorption of water vapor via Joule heating. On the basis of this phenomenon linear actuators utilizing PEDOT/PSS films were successfully developed and applied to leverage actuator and Braille cell.     

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.     

Dip Coating of Water-Resistant PEDOT:PSS Films Based on Physical Crosslinking

Water-resistant poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films are valuable in biomedical applications; however, they typically require crosslinkers to stabilize the films, which can introduce undesired aggregation or phase separation reactions. Herein, a dipping-based process to prepare PEDOT:PSS films on nonplanar surfaces without crosslinker is developed. Sequential soaking of a dip-coated PEDOT:PSS film in ethanol and water imparts water resistance to the film. Microscopic and spectroscopic techniques are used to monitor the process and confirm that the ethanol soaking elutes the excess PSS from the film bulk, which stabilizes the film prior to the water-soaking process. The obtained films act as conductors and semiconductors on curved surfaces, including 3D-printed objects. A film deposited on a curved surface is successfully applied as the channel layer in a neuromorphic organic electrochemical transistor. This approach can enable integrated bioelectronic and neuromorphic applications that can be readily deployed for facile prototyping.     

Film formation, surface character, and relative density for electrochromic PEI/(PSS:PEDOT) multilayered thin films

Thin films of alternating layer composition were constructed from the polyelectrolyte complex PEDOT:PSS and the polycation PEI, using ionic self assembly (ISA). The PEI/PEDOT:PSS system displays a consistent trend in film growth, as evidenced by UV-visible spectroscopy and ellipsometry. We find that the overall density of PEDOT increases with increasing number of layers. The density of PSS during multilayer deposition differs from PEDOT, with a sharp drop in density between the 3rd and 6th bilayers. Combining film deposition estimates with contact angle measurement, we distinguish three regions of growth, separated by the 3rd and 6th layers. We ascertain that a constant level of interpenetration between PEI and PEDOT:PSS is reached by the 6th layer. Results from kinetics experiments and pH variation reveal a local increase in pH for the PEDOT species as it comes into contact with the PEI surface. Electrochemical characterization indicates that our films have an interpenetrated PEDOT network and a relatively hydrophilic surface. We demonstrate that ISA can be used to generate robust thin films, stable over a large pH range, whose coloration and conductivity may be manipulated on a large scale using applied voltage, and may be fine-tuned by changing the pH. The films exhibit electrochromic properties similar to other PEDOT derivatives, with a change in transmittance of 51% for 16 bilayers at 643 nm.     

Semiconductor–Metal Transition in Poly(3,4‐Ethylenedioxythiophene): Poly(Styrenesulfonate) and its Electrical Conductivity While Being Stretched

Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film was prepared from an aqueous dispersion of the polymer treated with 5 wt% dimethylsulfoxide (DMSO) on a glass substrate and was electronically characterized in order to study its electronic properties. The electrical resistance of the polymer film was measured over the temperature range (380–10 K) using four‐point probe technique. It was noticed that the electrical resistance followed three different trends each of which was indicative of a different charge carrier transport mechanism. Each mechanism was investigated in more detail. A semiconductor to metal transition was also observed at 292 K above which dR/dT had a positive slope. Furthermore, Hall effect, electrical conductivity and sheet resistance measurements were performed on the polymer film using van der Pauw technique. The metallic behavior of PEDOT:PSS at room temperature was further evidenced by the results of these measurements. Next, stretchable knitted fabric was coated with PEDOT:PSS prepared from the polymer dispersion treated with 5 wt% DMSO. The conductive fabric was then stretched axially to different amounts of strain and was electrically characterized in both relaxed and stretched states. Despite the constant decrease in its electrical conductivity, the fabric remained electrically conductive while being stretched under increasing applied strain. POLYM. ENG. SCI., 59:1051–1056, 2019. © 2019 Society of Plastics Engineers     

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.     

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.     

Effects of solvents on thermoelectric performance of PANi/PEDOT/PSS composite films

Organic thermoelectric materials based on conducting polymers, especially for polyaniline (PANi) and poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), have attracted great concern due to their tunable electron transport properties by controlling doping level. Here, the solvent effects of deionized H₂O and NH₃·H₂O were investigated on the electrical conductivity and Seebeck coefficient of PANi/PEDOT/PSS composite films. The introduction of PEDOT/PSS can not only effectively improve the quality of pure PANi film, but also enhance the electrical conductivity of PANi film. The different volumes of deionized H₂O as dilution have a great influence on the electrical conductivity of PANi/PEDOT/PSS composite thin film with a maximum electrical conductivity value of 63.5 S cm^?1, which is much higher than pure PANi and pristine PEDOT/PSS. The introduction of NH₃·H₂O shows a positive effect on Seebeck coefficient with a large decline on electrical conductivity of PANi/PEDOT/PSS. The Raman spectroscopy, scanning electron microscopy (SEM), and UV-vis spectroscopy were used to obtain the morphology and structure information of PANi/PEDOT/PSS.     

A PSS‐Free PEDOT Conductive Film Supported by a Hierarchical Nanoporous Layer Glass

The importance of transparent conductive film is increasing due to its use in applications such as touch‐panel devices. Although indium tin oxide is widely used because of its high conductivity and transparency, conductive polymers are being studied as alternative materials that avoid the use of rare metals and the brittleness associated with existing systems. Polyethylene dioxythiophene (PEDOT)/polyethylene sulfonic acid (PSS) is drawing a lot of attention due to its well‐balanced conductivity, transparency, film formability, and chemical stability. The nonconductive PSS reportedly covers the conductive PEDOT. The PSS shell provides carrier and film‐formability to PEDOT but is also a barrier that hinders electrical conductivity. Therefore, the PEDOT film formability is explored supported by a substrate without the addition of PSS. The “hierarchical nanoporous layer glass” holds the PSS‐free PEDOT with its nanopores to form a homogeneous, transparent film. The PSS‐free PEDOT film thus achieves transparency of over 85% and resistivity of below 500 Ω sq^?1.     

Morphological and electronic consequences of modifications to the polymer anode ‘PEDOT:PSS’

We present a microscopic and electronic investigation of the polymeric anode poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) used as an electrode in photovoltaic and single carrier diodes. PEDOT:PSS is processed from aqueous solution as a colloidal dispersion with excess PSS present. We modify the PEDOT:PSS solution by the addition of a high boiling point alcohol, glycerol, which is known to increase the conductivity of the spin-coated film. Atomic force microscopy indicates swelling and greater aggregation of the PEDOT-rich colloidal particles found in this system. Current-voltage characteristics of ‘hole-transporting’ diodes, formed with gold contacts, suggest less surface enrichment of PSS in the glycerol modified electrode. Through Kelvin probe microscopy, we find the surface potential of glycerol modified PEDOT:PSS decreases by approximately 0.12 eV, which we assign to a reduction in surface enrichment by PSS. Photovoltaic diodes, using a PFB:F8BT polymer blend as the photo-active layer, and glycerol modified PEDOT:PSS anodes are significantly improved as compared to those with unmodified PEDOT:PSS anodes. This is likely to be due to improved hole-injection from the active polymer film into the PEDOT:PSS anode. This emphasises the electronic consequences of the morphological reorientation of the PEDOT and PSS.     

Controlled wetting/dewetting through substrate vibration-assisted spray coating (SVASC)

We have recently developed a novel spray-coating method, called the “substrate vibration-assisted spray coating” (SVASC) (Zabihi and Eslamian in J Coat Technol Res 12:711–719, 2015), in which ultrasonic vibration is imposed on the substrate to improve the spray-on film and coating characteristics. In that work, the SVASC method was introduced, and its effectiveness on the uniformity and electrical conductivity of PEDOT:PSS films, used in emerging solar cells, was demonstrated. The present work reports unprecedented results on the effect of the ultrasonic vibration power on wetting/dewetting of PEDOT:PSS films. It is observed that, while the application of a low-power ultrasonic vibration (LPUV) improves the surface wetting and film coverage through improving droplet spreading and coalescence and repairing of the dewetted areas, a high-power ultrasonic vibration (HPUV) promotes dewetting, resulting in less coverage and the formation of a nonuniform film. The improved wetting due to the application of the LPUV has opened a window of opportunity for the fabrication of intact thin films and related thin film devices. On the other hand, the controlled dewetting process due to the application of the HPUV may have novel applications in template fabrication and self-assembly in nanotechnology. Here, we also study the effects of the application of multipass spraying compared with single-pass spraying strategy, and the application of using two co-solvents on PEDOT:PSS film characteristics. The results confirm that the utilization of isopropyl alcohol (IPA) as a co-solvent added to the PEDOT:PSS precursor solution improves the surface wettability and film coverage, compared to the films made using demethylformamide (DMF), as the co-solvent.     

Process-dependent conductivity and film homogeneity of slot-die-coated PEDOT:PSS–PVA composite films

In this study, we investigate the impact of process parameters on homogeneity and electrical conductivity of slot-die-coated PEDOT:PSS–PVA composite films that are doped with DMSO. Due to a strong correlation between conductivity and morphology of PEDOT:PSS films and the latter’s dependency on the processing step itself, we apply slot die coating for maximized process control and systematically evaluate the impact of coating gap, speed, and film thickness. Since the entire coating and drying process is run in batch mode, the setup is optimized regarding steady-state conditions and high homogeneity of the films. Overall, for the films manufactured in batch mode, we obtain a reproducibility film thickness of 99% and a low deviation from the set film thickness (below 8%). In order to analyze the impact of the coating parameters, stable operating points derived from the viscocapillary model are chosen and either the dimensionless gap or the capillary number is varied. Coating gap and film thickness emerged as dominating parameters, leading to an increase in conductivity of 40% and 70%, respectively, or, when changing both simultaneously, of 157%. Only a minor impact of shear forces (increase of 10%) was found.     

On the mechanism of conductivity enhancement in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film through solvent treatment

The conductivity of a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film is enhanced by more than 100-folds on adding some organic compounds into PEDOT:PSS aqueous solutions or by treating the PEDOT:PSS film with organic solvents, such as ethylene glycol (EG), 2-nitroethanol, methyl sulfoxide or 1-methyl-2-pyrrolidinone. The mechanism for this conductivity enhancement was studied through various chemical and physical characterizations. The PEDOT:PSS film which is soluble in water becomes insoluble after treatment with EG. This strongly suggests an increased interchain interaction among the PEDOT chains. Raman spectroscopy indicates that this increased interchain interaction results from conformational changes of the PEDOT chains, which change from a coil to linear or expanded-coil structure. The increased interchain interaction and conformation changes are further confirmed by the temperature dependence of conductivity and the electron spin resonance (ESR). It is found that EG treatment lowers the energy barrier for charge hopping among the PEDOT chains, lowers the polaron concentration in the PEDOT:PSS film by ∼50%, and increases the electrochemical activity of the PEDOT:PSS film in NaCl aqueous solution by ∼100%. Atomic force microscopy (AFM) and contact angle measurements show that the surface morphology of the PEDOT:PSS film changes as well after the EG treatment. Conductivity enhancement was also observed when other organic compounds were used, but it was strongly dependent on the chemical structure of the organic compounds, and observed only with organic compound with two or more polar groups. These experimental results support our proposal that the conductivity enhancement is due to the conformational change of the PEDOT chains and the driving force is the interaction between the dipoles of the organic compound and dipoles or charges on the PEDOT chains.     

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。     

Electrical properties of nitric acid and DMSO treated PEDOT:PSS/n-Si hybrid heterostructures for optoelectronic applications

Organic/inorganic heterostructures are an emerging and interesting field of research for optoelectronics. In this work, an efficient organic/inorganic hybrid heterojunction between PEDOT:PSS and n-type Silicon has been fabricated for optoelectronic applications. Samples with varying thickness of PEDOT:PSS were prepared by spin coating technique and the electrical conductivity of organic layers was modified using DMSO as additive. Post fabrication, the hybrid heterostructures were treated with HNO₃ vapor so as to enhance the conductivity of the organic layer. Surface treatment with HNO₃ was found to lower the roughness of the organic layer and enhance the transparency of the layer. I–V characteristics reveal optimized behavior of HNO₃ treated PEDOT:PSS layer with a low Ideality factor (n~3.2) and a barrier height (Φ_B) of 0.8 eV. The findings of the study provide a promising efficient method to enhance the electrical and device properties of PEDOT:PSS/n-Si heterostructures for optoelectronic applications. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48952.     

Selective Coating of SnS on the Bio‐Inspired Moth‐Eye Patterned PEDOT:PSS Polymer Films

A new strategy for the selective coating of tin sulfide (SnS) on the surface of moth‐eye patterned (MEP) conducting polymer film is studied by considering the optical properties of the antireflective moth‐eye pattern and flexibility of polymer films. The semiconductor SnS is selectively coated on the surface of MEP microdomes of poly(3,4‐ethylenedioxythiophene) poly(styrene‐sulfonate) (PEDOT:PSS) film. The SnS coated MEP film is obtained by using pore selectively SnS thin layer functionalized polystyrene honeycomb‐patterned porous (HCP) film as a template. Aqueous PEDOT:PSS solution is poured on the SnS functionalized HCP films and detached for the fabrication of SnS coated MEP films. The films show a satisfactory photo‐responsive property under solar stimulated light illumination due to the antireflective MEP structure of PEDOT film and homogenous SnS coating on the surface of the conducting polymer.     

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.