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•PEDOT:PSS is promising to be the next-generation transparent electrode.•This article reviews the “secondary doping” methods for conductivity enhancement of PEDOT:PSS.•The ...conductivity of PEDOT:PSS can be comparable to ITO.•Highly conductive PEDOT:PSS films were used for polymer light-emitting diodes and polymer solar cells.
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful conducting polymer in terms of the practical application. It can be dispersed in water and some polar organic solvents, and high-quality PEDOT:PSS films can be readily prepared through solution processing. In addition, PEDOT:PSS is highly transparent in the visible range and has excellent thermal stability. Nevertheless, PEDOT:PSS has a problem of low conductivity. The as-prepared PEDOT:PSS films from its aqueous solution have a conductivity of lower than 1Scm−1, which severely impedes the application of PEDOT:PSS in various aspects. It has been discovered that the conductivity of as-prepared PEDOT:PSS from its aqueous solution can be significantly enhanced by adding organic compounds like high-boiling point polar organic solvents, ionic liquids and surfactants or through a post-treatment of PEDOT:PSS films with organic compounds, including high-boiling point polar solvents, salts, zwitterions, cosolvents, organic and inorganic acids. Conductivity of more than 3000Scm−1 was recently observed on PEDOT:PSS films after treated with sulfuric acid. This conductivity is comparable to that of indium tin oxide (ITO), the conventional transparent electrode material of optoelectronic devices. In addition, PEDOT:PSS has high mechanical flexibility while ITO is a brittle material. Thus, PEDOT:PSS is very promising to be the next-generation transparent electrode material. This article reviews the methods to enhance the conductivity of PEDOT:PSS, the mechanisms for the conductivity enhancements and the application of the highly conductive PEDOT:PSS films in polymer light-emitting diodes and polymer solar cells.
Intrinsically conducting polymers (ICPs), such as polyacetylene, polyaniline, polypyrrole, polythiophene, and poly(3,4‐ethylenedioxythiophene) (PEDOT), can have important application in flexible ...electronics owing to their unique merits including high conductivity, high mechanical flexibility, low cost, and good biocompatibility. The requirements for their application in flexible electronics include high conductivity and appropriate mechanical properties. The conductivity of some ICPs can be enhanced through a postpolymerization treatment, the so‐called “secondary doping.” A conducting polymer film with high conductivity can be used as flexible electrode and even as flexible transparent electrode of optoelectronic devices. The application of ICPs as stretchable electrode requires high mechanical stretchability. The mechanical stretchability of ICPs can be improved through blending with a soft polymer or plasticization. Because of their good biocompatibility, ICPs can be modified as dry electrode for biopotential monitoring and neural interface. In addition, ICPs can be used as the active material of strain sensors for healthcare monitoring, and they can be adopted to monitor food processing, such as the fermentation, steaming, storage, and refreshing of starch‐based food because of the resistance variation caused by the food volume change. All these applications of ICPs are covered in this review article.
Because they combine the merits of metals and plastics, intrinsically conducting polymers can have important application in flexible electronic devices and systems, such as flexible electrode particularly the transparent electrode of optoelectronic devices, stretchable electrode, dry biopotential electrode, neural interface, and strain sensors for healthcare monitoring and food processing monitoring.
A green method is reported to effectively and rapidly reduce graphene oxide to graphene with zinc powder at room temperature. The reduction is carried out by mixing graphene oxide and zinc powder in ...solution under ultrasonication. The reduction is complete within 1
min. The weight of the Zn powder should be at least as twice as that of graphene oxide to complete the reduction. The reduction of graphene oxide is confirmed by FTIR, UV–Vis absorption spectroscopy and Raman spectroscopy. The carbon/oxygen atomic ratio has increased from 2.58 to 33.5 after the reduction as determined by X-ray photoelectron spectroscopy. The reduced graphene oxide can have a conductivity of 15,000
S/m. It also has good thermal stability with the weight loss at 590
°C in air. The reduced graphene oxide can be readily re-dispersed into solutions of various surfactants.
Carbon nanotubes (CNTs) and graphene have attracted great attention since decades ago because of their interesting structure and properties and important application in many areas. They can have high ...conductivity, high specific surface area, high transparency in the visible range and high mechanical flexibility. They have important application in energy conversion systems including solar cells and fuel cells. They have been extensively studied as the transparent electrode and interfacial materials of organic solar cells (OSCs) and perovskite solar cells (PSCs). They are also used as the catalytic counter electrode of dye-sensitized solar cells (DSSCs). In addition, graphene oxide (GO) is exploited as an auxiliary binder of TiO2 paste for the mesoporous TiO2 layer of DSSCs, and GO and functionalized CNTs are adopted as gelators of gel electrolyte for quasi-solid state DSSCs. CNTs and graphene also have important application in fuel cells. They can be used as catalyst support for the oxidation of fuels or oxygen reduction reaction (ORR). CNTs and graphene, particularly when doped with nitrogen, can be directly used metal-free catalysts. This article provides a brief review on the application of CNTs and graphene in OSCs, PSCs, DSSCs and fuel cells. Keywords: Carbon nanotube, graphene, organic solar cell, perovskite solar cell, dye-sensitized solar cell, electrocatalysis
The conductivity of PEDOT:PSS films was significantly enhanced from 0.3 S cm−1 to 3065 S cm−1 through a treatment with dilute sulfuric acids. PEDOT:PSS films with a sheet resistance of 39 Ω sq−1 and ...transparency of around 80% at 550 nm are obtained. These PEDOT:PSS films with conductivity and transparency comparable to ITO can replace ITO as the transparent electrode of optoelectronic devices.
Stretchable and conductive materials can have important application in many areas, such as wearable electronics and healthcare devices. Conducting polymers have very limited elasticity because of ...their rigid conjugated backbone. In this work, highly stretchable and conductive polymer films are prepared by coating or casting aqueous solution of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and a soft polymer, including poly(ethylene glycol), poly(ethylene oxide), or poly(vinyl alcohol). The soft polymers can greatly improve the stretchability and the conductivity of PEDOT:PSS. The elongation at break can be increased from 2% up to 55%. The soft polymers can also enhance the conductivity of PEDOT:PSS from 0.2 up to 75 S cm–1. The conductivity is further enhanced by adding dimethyl sulfoxide (DMSO) or ethylene glycol (EG) into the aqueous solutions of the polymer blends. Polymer blends with an elongation at break of close to 50% and a conductivity of 172 S cm–1 are attained.
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is promising to be the next-generation transparent electrode of optoelectronic devices. This paper reports the differences between ...two commercially available grades of PEDOT:PSS: Clevios P and Clevios PH1000. The as-prepared PEDOT:PSS films from Clevios P and Clevios PH1000 solutions have close conductivities of 0.2–0.35 S cm–1. Their conductivities can be enhanced to 171 and 1164 S cm–1, respectively, through a treatment with hydrofluoroacetone trihydrate (HFA). The differences between Clevios P and Clevios PH1000 were studied by various characterizations on PEDOT:PSS aqueous solutions and PEDOT:PSS films. The gel particles are larger in Clevios PH1000 solution than in Clevios P solution as revealed by dynamic light scattering and fluorescence spectroscopy of pyrene in these solutions. These results suggest that PEDOT of Clevios PH1000 has a higher average molecular weight than that of Clevios P. The difference in the molecular weight of PEDOT for the two grades of PEDOT:PSS is confirmed by the characterizations on their polymer films, including atomic force microscopy and temperature dependences of the resistances of as-prepared and HFA-treated PEDOT:PSS films. The different molecular weights of PEDOT also gives rise to significant differences in the electrochemical behaviors of the two grades of PEDOT:PSS, as revealed by the cyclic voltammetry, in situ UV–vis–NIR absorption spectroscopy and potentiostatic transient measurements.
This article presents a facile one-pot synthetic method to prepare ternary NiAuPt nanoparticles on reduced graphene oxide (rGO) nanosheets (NiAuPt-NGs) through the simultaneous chemical reduction of ...metal precursors and GO in solution and an investigation of NiAuPt-NGs as electrocatalysts toward ethanol oxidation reaction (EOR). The NiAuPt nanoparticles grow on the rGO sheets after the chemical reduction of their precursors. They consist of tightly coupled nanostructures of Ni, Au, and Pt, which have neither an alloy nor a core–shell structure, as revealed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. As indicated by the Raman spectra, GO is reduced to rGO more completely in the presence of the metal precursors than in the absence of the metal precursors. The electrocatalysis of NiAuPt-NGs toward EOR in alkaline medium was investigated by cyclic voltammetry, chronoamperometry, and impedance spectroscopy. NiAuPt-NGs can effectively catalyze EOR. The ternary NiAuPt-NGs give rise to a high peak current density for EOR, which is more than 8 times higher than that on the monometallic Pt-NGs, 4 times higher than that on the bimetallic NiPt-NGs, and almost 2 times higher than that on the bimetallic AuPt-NGs. In addition, NiAuPt-NGs substantially lower the onset potential for EOR. It is −803 mV vs SHE, which suggests the excellent tolerance of NiAuPt-NGs against the residues of EOR. The high electrocatalytic activity of NiAuPt-NGs is attributed to the synergetic effect of the three nanostructured metals for EOR.
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•Resistive switches are observed on devices with Au nanoparticles capped with 2-naphthalenethiol.•The resistive switches are sensitive to the electrodes.•The resistive switches are ...sensitive to the capping ligand of the Au nanoparticles.•The resistive switches are insensitive to the polymer matrix.•These results confirm the charge-transfer model for the resistive switches.
Electronic devices with an polystyrene (PS) layer blended with Au nanoparticles capped with conjugated 2-naphthalenethiol (Au–2NT NPs) sandwiched between Au and Al electrodes exhibit bipolar resistive switches sensitive to the electrodes. This paper reports the effects of materials, including electrode materials, capping ligands of Au nanoparticles and matrix polymers, on the electrical behavior of the polymer:nanoparticle memory devices. Although the devices using Cu to replace Au as the top electrode exhibit resistive switches similar to those with Au, the threshold voltage for the resistive switch is higher, and the current density for the devices in the low conductivity state is lower. However, the threshold voltage and the current density are almost the same as those with Au as the top electrode, when a semiconductor, MoO3, is used to replace Au as the top electrode of the devices. The effects of these electrodes are attributed to the charge transfer at the contacts between Au–2NT NPs and the electrodes. The resistive switches are also sensitive to the capping organic ligand of the Au nanoparticles. The threshold voltage decreases and the current density increases, when conjugated benzenethiol is used to replace 2-naphthalenethiol. However, the current density dramatically decreases and the threshold voltage increases, when 2-benzeneethanethiol, a partially conjugated molecule, is adopted as the capping ligand of the Au nanoparticles. The effect of the capping ligands is ascribed to their effect on the charge tunneling across the Au–2NT NPs in the active layer and the contacts between Au–2NT NPs and electrodes. The devices with poly(methyl methacrylate) (PMMA) replacing PS as the polymer matrix exhibit resistive switches almost the same as those with PS, which indicates that the Au–2NT NPs rather than the polymer is the active material responsible for the resistive switches.
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