Pure PEDOT Research Articles

Electrochemical synthesis and characterization of nanocomposites based on poly(3,4-ethylenedioxythiophene) and functionalized carbon nanotubes

This work is focused on new composite materials consisting of poly(3,4-ethylenedioxythiophene) (pEDOT) and functionalized multi-walled carbon nanotubes synthesized electrochemically. Three types of composites were synthesized: the first one containing carbon nanotubes with carboxyl groups (covalent functionalization), the second one containing oxidized carbon nanotubes ox-MWCNTs (with different oxygen-rich polar groups) (covalent functionalization) and the third one containing carbon nanotubes dispersed using surfactant (non-covalent functionalization). The presence of oxygen moieties attached to carbon nanotubes decreases their hydrophobicity and helps to suspend them more uniformly in a solution used for electrosynthesis than the surfactant addition. Homogenous dispersion of carbon nanotubes and their amount in the synthesis solution is crucial for reproducibility and electrochemical properties of the composite layers. Thin nanocomposite films were tested electrochemically for supercapacitor application. Detailed surface investigation of the electrode layers by X-ray photoelectron spectroscopy shows differences in the chemical composition between the composites and the pure polymer. Moreover, electrochemical results show that the presence of carbon nanotubes with carboxyl groups in the polymer matrix may double the capacitance values compared to pure pEDOT.

Enhanced thermoelectric performance of PEDOT:PSS films by solvent thermal treatment

Flexible free-standing PEDOT:PSS films were thermally treated by various of high polar organic solvents such as N-methyl-2-pyrrolidone (NMP), ethylene glycol (EG), dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and a comparative thermoelectric (TE) study was conducted in the present work. Due to the synergistic effect of high polar solvent and thermal treatment, the maximum electrical conductivity of PEDOT:PSS films was up to 520 S cm−1 by EG post-treatment at its boiling point (197 °C), resulting in a power factor of 14.9 μW m−1 K−2, which was four orders of magnitude higher than pure PEDOT:PSS film (~0.005 μW m−1 K−2). The improvement of TE performance is primarily caused by the increased electrical conductivity and the steady Seebeck coefficient. As observed from atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) characterization, the enhancement of electrical conductivity is attributed to the removal of excess insulating PSS from the PEDOT:PSS film surface and the separation of the rest PSS chains in the polymer matrix from the PEDOT phase.

Enhanced Electromagnetic Wave Absorption Properties of Poly(3,4-ethylenedioxythiophene) Nanofiber-Decorated Graphene Sheets by Non-covalent Interactions.

Graphene sheets (GNs) have high conductivity, but they exhibit weak electromagnetic (EM) wave absorption performance. Here, poly (3,4-ethylenedioxythiophene) (PEDOT) nanofibers were decorated on the surface of GNs in which the residual defects and groups act as the active sites and therefore are beneficial for the deposition of PEDOT nanofibers. The SEM images display that PEDOT nanofibers are successfully decorated on the surface of GNs through in situ polymerization. The diameter of the PEDOT nanofibers were ranged from 15 to 50 nm with hundreds of nanometers in length. The EM wave absorption properties of graphene, PEDOT, and GNs-PEDOT were also investigated. Compared to pure graphene and PEDOT, the EM wave absorption properties of GNs-PEDOT improved significantly. The maximum value of R L was up to −48.1 dB at 10.5 GHz with a thickness of only 2 mm. Meanwhile, the absorption bandwidth of R L values below −10 dB was 9.4 GHz (5.8–12.3, 12.9–15.8 GHz) in the thickness of 1.5–3 mm. The enhancement is attributed to the modification of PEDOT and the unique structure of nanofibers. On one hand, the deposition of PEDOT nanofibers on the surface of GNs decreases the conductivity of graphene, and makes impedance match better. On the other hand, the unique structure of PEDOT nanofibers results in relatively large specific surfaces areas, providing more active sites for reflection and scattering of EM waves. Therefore, our findings demonstrate that the deposition of conducting polymers on GNs by non-covalent bond is an efficient way to fabricate strong EM wave absorbers.

Preparation of Supercapacitors on Flexible Substrates with Electrodeposited PEDOT/Graphene Composites.

Composite films consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) were electrochemically polymerized by electrooxidation of EDOT in ionic liquid (BMIMBF4) onto flexible electrode substrates. Two polymerization approaches were compared, and the cyclic voltammetry (CV) method was found to be superior to potentiostatic polymerization for the growth of PEDOT/GO films. After deposition, incorporated GO was reduced to rGO by a rapid electrochemical method of repetitive cathodic potential cycling, without using any reducing reagents. The films were characterized in 3-electrode configuration in BMIMBF4. Symmetric supercapacitors with aqueous electrolyte were assembled from the composite films and characterized through cyclic voltammetry and galvanostatic discharge tests. It was shown that PEDOT/rGO composites have better capacitive properties than pure PEDOT or the unreduced composite film. The cycling stability of the supercapacitors was also tested, and the results indicate that the specific capacitance still retains well over 90% of the initial value after 2000 consecutive charging/discharging cycles. The supercapacitors were demonstrated as energy storages in a room light energy harvester with a printed organic solar cell and printed electrochromic display. The results are promising for the development of energy-autonomous, low-power, and disposable electronics.

Functionalization of Graphene Oxide and its Composite with Poly(3,4-ethylenedioxythiophene) as Electrode Material for Supercapacitors.

In this study, poly(3,4-ethylenedioxythiophene)/thiophene-grafted graphene oxide (PEDOT/Th-GO) composites from covalently linking of Th-GO with PEDOT chains were prepared via in situ chemical polymerization with different weight percentage of Th-GO ranging between 40 and 70 % in reaction medium. The resulting composite materials were characterized using a various analytical techniques. The structural analysis showed that the composites displayed a higher degree of conjugation and thermal stability than pure PEDOT, and the weight percentage of Th-GO could affect the doping level, amount of undesired conjugated segments, and porous structure of composites. Electrochemical analysis suggested that the highest specific capacitance of 320 F g−1 at a current density of 1 A g−1 with good cycling stability (capacitance retention of 80 % at 1 A g−1 after 1000 cycles) was achieved for the composite prepared from 50 wt% Th-GO content in reaction medium.

Low Work-function Poly(3,4-ethylenedioxylenethiophene): Poly(styrene sulfonate) as Electron-transport Layer for High-efficient and Stable Polymer Solar Cells.

Low-work-function poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified with polyethylenimine (PEIE) was used as an electron transport layer (ETL) for polymer solar cells (PSCs). A thin layer of PEIE film was spin-coated onto the surface on the PEDOT:PSS films, thus substantially changing their charge selectivity from supporting hole transport to supporting electron transport. It was also found that the PEDOT:PSS/PEIE ETL exhibited higher interfacial contact, a more favorable active morphology, and improved charge mobility. By virtue of these beneficial properties, inverted PSCs based on low-bandgap semiconducting photoactive layers achieved a notably improved power conversion efficiency (PCE) of 7.94%, superior even to the corresponding performance of devices with only a ZnO layer. Surpassing our expectations, compared with the extreme degradation of device stability observed when pure PEDOT:PSS is used, PEIE-modified PEDOT:PSS can considerably suppress device degradation because of the hydrophobic and alkaline nature of PEIE, which not only reduces the hygroscopicity of the PEDOT:PSS but also neutralizes the acidic PEDOT:PSS and thus prevents the corrosion of the ITO cathode. These results demonstrate the potential of PEIE-modified PEDOT:PSS for use as an efficient ETL in commercial printed electronic devices.

PEDOT:PSS/graphene/PEDOT ternary film for high performance electrochemical electrode

For effective use of graphene and conducting polymer, a new ternary hybrid film composed of poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), graphene, and poly (3,4-ethylenedioxythiophene) (PEDOT) has been designed and fabricated. The ternary PEDOT:PSS/graphene/PEDOT film is prepared via a two-step process: PEDOT:PSS/graphene hybrid film was spin-coated on the substrate in the first step and followed by the vapor phase polymerization (VPP) of PEDOT film on the PEDOT:PSS/graphene film in the second step. Each component in the hybrid film provides unique and crucial function to achieve optimized electrochemical properties. Volumetric capacity of ternary film (155.71 F/cm3) is much higher than that of pure VPP PEDOT film (93.66 F/cm3). The ternary film also exhibits excellent charge/discharge rate and good cycling stability, retaining 92 % of its initial charge after 5500 cycles. The enhanced electrochemical performances of such ternary composite indicate a promising future as electrode material for electrochemical energy storage devices.

Improved efficiency of indium-tin-oxide-free organic light-emitting devices using PEDOT:PSS/graphene oxide composite anode

We have demonstrated an indium-tin-oxide free organic light-emitting device (OLED) with improved efficiency by doping poly (3,4-ethylene dioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) with graphene oxide (GO) as a composite anode. In comparison with a pure PEDOT:PSS anode, 55% enhancement in efficiency has been obtained for the OLEDs based on the PEDOT:PSS/GO composite anode at an optimal condition. The PEDOT:PSS/GO composite anode shows a lower hole-injection barrier, which contributes to the improved device efficiency. Moreover, both high transmittance and good surface morphology similar to that of the pure PEDOT:PSS film also contribute to the enhanced efficiency. It is obvious that composite anode will generally be applicable in organic optoelectronic devices which require smooth and transparent anode.

Morphology and electrical properties of poly(3,4-ethylenedioxythiophene)/titanium dioxide nanocomposites

Poly(3,4-ehtylenedioxythiophene) (PEDOT) nanocomposites including nano-sized titanium dioxide were prepared by in situ polymerization technique and were characterized by Fourier transform infrared (FTIR) and UV-visible spectroscopy. Morphological studies of the nanocomposites were performed using scanning electron microscopy and transmission electron microscopy to support the formation of PEDOT-TiO2 nanocomposites. Results suggested that the TiO2 nanoparticles were well-dispersed in the PEDOT polymer matrix. The electric properties of the nanocomposites were obtained by measuring the temperature-dependent direct current (DC) conductivity between 300 and 500 K and low frequency alternate current conductivity between 0 and 10 kHz. The PEDOT-TiO2 nanocomposites exhibited remarkable improvement in the temperature-dependent DC conductivity with decreased dielectric constants and dielectric losses, compared to pure PEDOT polymer, which indicates their higher ability to store electric potential energy under the influence of an alternating electric field.

Fabrication of nanostructured PEDOT clusters using β-cyclodextrin as substrate and applied for simultaneous determination of hyperoside and shikonin

Nanostructured poly(3,4-ethylenedioxythiophene)/β-cyclodextrin (PEDOT/β-CD) was prepared by the oxidation of EDOT with FeCl3 using β-CD as substrate. The as-synthesized nanocomposites were characterized by scanning electronic microscopy (SEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). It was found PEDOT/β-CD clusters were uniformly distributed, and hold an enhanced surface-to-volume ratio. The electrocatalytic performance of the nanostructured PEDOT/β-CD toward hyperoside and shikonin was investigated, which revealed that PEDOT/β-CD performed a better electrocatalytic activity than pure PEDOT. Thus, PEDOT/β-CD clusters were proposed as electrochemical sensing platform to detect hyperoside and shikonin. This simple PEDOT/β-CD complex demonstrated very sensitive and selective hyperoside and shikonin detection capability, as well as high reproducibility and stability.

An effective approach to enhanced thermoelectric properties of PEDOT:PSS films by a DES post-treatment

As conventional organic solvents present inherent toxicity, deep eutectic solvents (DES) have been considered as excellent candidates due to their green characteristics. In this work, thermoelectric properties enhancement of PEDOT:PSS films is achieved by introducing DES as an additive and post-treatment reagent. Direct addition and post-treatment approaches lead to a maximum Seebeck coefficient of 29.1 μV K−1 and electrical conductivity of 620.6 S cm−1, respectively. In addition, an optimal power factor is obtained by DES post-treatment, reaching up to 24.08 μW m−1 K−2, which is approximately four orders of magnitude higher than the pure PEDOT:PSS. Assuming a thermal conductivity of 0.17 W m−1 K−1, the maximum ZT value is estimated to be 0.042 at 300 K. Further, atomic force microscopy and X-ray photoelectron spectroscopy are performed and suggest that the remarkably enhanced electrical conductivity originates from the removal of the excess insulating PSS and the phase separation between the PEDOT and PSS chains. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 885–892

Electrochromic Properties of Acid Dye Doped Poly(3,4-ethylenedioxythiophene) by Electropolymerization.

The electrochromic properties of an electrochemical polymerized composite consisted of poly(3,4-ethylenedioxythiophene) doped with acid red G (PEDOT-ARG) are reported. The structures of PEDOT-ARG were characterized via cycle voltammograms, spectroelectrochemistry and colorimetric analysis. Film of the PEDOT-ARG composites switches from aubergine in the reduction state to light blue in the oxidized state, which is different from the pure PEDOT of dark blue (-0.8 V) and light blue (1.0 V). Because of the big molecule of acid red G as the dopant, the response time reaching 90% of the full optical contrast of PEDOT-ARG was 5.7 s for the oxidation process and 5.4 s for the reverse reduction process, which is a little slower than the pure PEDOT. Additionally, the colorimetric analysis results show that components of red in PEDOT-ARG films become stronger than the pure PEDOT films at the whole electrochromic process. It is shown that acid dye doping is an effective method to broaden the color change range of the electrochromic materials.

Preparation of PEDOT/GO, PEDOT/MnO2, and PEDOT/GO/MnO2 nanocomposites and their application in catalytic degradation of methylene blue

The nanocomposite materials of poly(3,4-ethylenedioxythiophene)/graphene oxide (PEDOT/GO), poly(3,4-ethylenedioxythiophene)/MnO2 (PEDOT/MnO2), and poly(3, 4-ethylenedioxythiophene)/graphene oxide/MnO2 (PEDOT/GO/MnO2) were successfully prepared by facile and template-free solution method. The structure and morphology of nanonanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible absorption spectra (UV–vis), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), respectively. The catalytic activities of nanocomposites were investigated through the degradation processes of methylene blue (MB) solution under dark, UV light, and nature sunlight irradiation, respectively. The results displayed that nanocomposites were successfully synthesized, and PEDOT/GO had higher conjugation length and doped degree than pure PEDOT. However, the introduction of MnO2 could lead to the reduction of conjugation length and doped degree in PEDOT/MnO2 and PEDOT/GO/MnO2 nanocomposites. The field emission scanning electron microscope (FESEM) analysis also showed that both MnO2 and GO had some effect on the morphology of nanocomposites. The catalytic activities of pure PEDOT and nanocomposites were in the order of PEDOT/GO/MnO2 > PEDOT/MnO2 > PEDOT/GO > pure PEDOT. Besides, the catalytic results also showed that the highest degradation efficiency of MB after 7 h occurred in the PEDOT/GO/MnO2 composite in three irradiation.

Fabrication of silicon nanowire/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-graphene oxide hybrid solar cells

Silicon nanowire (SiNW)/Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) Schottky junctions have shown great promise as high efficiency, cost effective solar cells. Here, hybrid SiNWs/PEDOT:PSS blended graphene oxide (GO) solar cells are prepared and investigated. The SiNWs/PEDOT:PSS blended GO cells show enhanced light trapping and a large junction area when compared to pure PEDOT:PSS structures. SiNWs combined with GO solar cells show energy conversion efficiencies of up to 9.57% under the AM 1.5G condition, opening the possibility of using semiconductor/graphene oxide in photovoltaic applications.

Enhanced thermoelectric performance of highly conductive poly(3,4-ethylenedioxythiophene)/carbon black nanocomposites for energy harvesting

The thermoelectric performance of para-methylbenzenesulfonate (p-MeBzs) doped highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) can be improved by the use of carbon black fillers. Thermoelectric nanocomposites were prepared via chemical polymerization. Dodecylbenzenesulfonic acid (DBSA) was introduced before polymerization to act simultaneously as a surfactant for formation of micelles of carbon black and as a doping agent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the morphology of PEDOT coated carbon black and PEDOT. Electrical conductivity of the composites improved with increase in weight percentage of carbon black from 0% to 30%. Extended chain conformations and increase in electron delocalization reduces the carrier hopping barriers. These contribute to the enhancement of charge carrier mobility. Although electrical conductivity is directly proportional to the increase in the filler content, Seebeck coefficient is more or less constant. Relatively small changes of thermal conductivity can be attributed to the phonon scattering effect in both the carbon black and the thermally insulating PEDOT layers. This study reports that the power factor of the composite was estimated to be 0.993μW/mK2 for 10wt% filler content and was more than 1.7 times higher than that for pure PEDOT, and the maximum figure of merit (ZT) value was 0.0012 at room temperature.

Improvement of electrical conductivity of PEDOT:PSS films by 2-Methylimidazole post treatment

The electrical conductivity of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films was significantly improved without losing the optical transparency by treating the films with solution of 2-Methylimidazole in ethanol. The maximum electrical conductivity of such a thin film reached 930Scm−1, more than 1150 order of magnitude higher than that of pure PEDOT:PSS film. The mechanism of conductivity enhancement of treated thin PEDOT:PSS films was explored by atomic force microscopy (AFM) and UV/VIS spectrophotometer. The AFM scans show that the surface of the 2-Methylimidazole treated PEDOT:PSS layer is smoother than that of the pristine PEDOT:PSS thin film. Improvement in the morphology, electrical and optical properties of PEDOT:PSS films makes them highly suitable for numerous applications in optoelectronic devices.

Poly(3,4-ethylenedioxythiophene) nanorods grown on graphene oxide sheets as electrochemical sensing platform for rutin

Hierarchical nanocomposites of poly(3,4-ethylenedioxythiophene) nanorods array on graphene oxide nanosheets (PEDOT/GO) were synthesized via a liquid–liquid interfacial polymerization method. The synthesized composites were characterized by using Fourier transform infrared (FTIR) and Raman spectroscopic studies, and their morphology was analyzed by transmission electron microscopy (TEM). Characterization and surface morphology results indicated that PEDOT with a nanorods-like structure successfully anchored on the surface of GO sheets, which could enhance the electro-active sites of the nanocomposites. Then the obtained PEDOT/GO nanocomposites were utilized to modify glassy carbon electrode and designed for the trace level sensing of rutin. Electrochemical results revealed that the PEDOT/GO nanocomposites modified electrode exhibited larger oxidation peak currents of rutin than pure PEDOT and GO owing to the synergistic effect of GO and PEDOT nanorods. Under optimized conditions, the anodic peak current was linear to the concentration of rutin in the range from 0.004 to 60μM with the detection limit of 0.00125μM. To further validate its possible application, the proposed method was successfully used for the determination of rutin in pharmaceutical formulations with satisfactory results.

Significant conductivity enhancement of PEDOT:PSS films treated with lithium salt solutions

An effective method to significantly enhance the electrical conductivity of PEDOT:PSS films through a treatment with various aqueous solutions of lithium salts such as LiClO4, Li2SO4 and LiNO3 etc., is presented in this paper. The maximum electrical conductivity of PEDOT:PSS film treated with LiClO4 could be up to 522 S cm−1, which was enhanced by a factor of 2,610 compared to that of pure PEDOT:PSS film (0.2 S cm−1). The FTIR spectra characterization was performed and suggested that the chemical structure of PEDOT:PSS didn’t change after the treatment. Remarkable improvement in carrier mobility was a key reason for the increase in the electrical conductivity. The highest carrier mobility of the PEDOT:PSS film by LiClO4 treatment could reach 3.8 cm2/Vs, approximately 15 times higher than that of pure PEDOT:PSS film with a value of 0.25 cm2/Vs.

Controllable synthesis of multi-walled carbon nanotubes/poly(3,4-ethylenedioxythiophene) core-shell nanofibers with enhanced electrocatalytic activity

Core-shell structured poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotubes (PEDOT/MWCNTs) nanofibers were synthesized through an interfacial polymerization technique. The interfacial polymerization at a liquid-liquid interface allowed PEDOT to grow uniformly on the surface of MWCNTs due to the presence of π-π interactions between PEDOT and MWCNTs walls. The morphology, structure and composition of the as-prepared PEDOT/MWCNTs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). In addition, the electrocatalytic properties of PEDOT/MWCNTs toward redox reactions of magnolol, a widely used traditional Chinese medicine, were systematically investigated. The results showed that the PEDOT/MWCNTs nanofibers exhibited a distinctly higher activity for the detection of magnolol compared with those of pure MWCNTs and PEDOT. The remarkably enhanced activity for the nanofibers can be attributed to the unique configuration and synergistic contribution between PEDOT and MWCNTs. The presented method is a general, facile and green approach for the synthesis of polymer/CNTs nanofibers, which is significant for the development of high performance electrocatalysts for biosensing and fuel cell applications.

The Electropolymerization and Characterizations of Fluorescent Dye Doped Poly(3,4-ethylenedioxythiophene)

The electrochromic properties of an electrochemical polymerized composite consisted of poly (3,4-ethylenedioxythiophene) doped with fluorescent yellow dye (PEDOT-FY) are reported. The structures of PEDOT-FY were characterized via cycle voltammograms, spectroelectrochemistry and colorimetric analysis. Film of the PEDOT-FY composites with different FY concentrations appears multi-color changes, such as blue violet↔brillant blue, aubergine↔blue grey, magenta↔ aquamarine blue, orange-yellow↔grass-green, claybank↔moss green in the neutral state and the oxidized state respectively, which are different from the pure PEDOT of dark blue (-0.8V) and light blue (1.0V). The response time reaching 90% of the full optical contrast of PEDOT-FY was 3.4s for the oxidation process and 2.6s for the reverse reduction process when the [EDOT]/[FY] is 1:2, however, when the FY concentration decreased to [EDOT]/[FY] =1:0.01, the response time reduced to 1.9s and 1.7s for the oxidation and reduction process respectively, which is equal to that of the pure PEDOT. Additionally, the colorimetric analysis results show that components of yellow and red in PEDOT-FY films become stronger than pure PEDOT film at the whole electrochromic process. It is shown that acid dye doping is an effective method to broaden the color change range of the electrochromic mateials.