A photovoltaic cell incorporating a dye-sensitized ZnS/ZnO composite thin film and a hole-injecting PEDOT layer

A photovoltaic cell containing a dye-sensitized ZnS/ZnO composite thin film was studied. ZnS was thermally evaporated or electrodeposited onto conducting fluorine-doped tin oxide glass; then a particulate ZnO layer was pasted and sintered to form a ZnS/ZnO composite layer. A visible light source was utilized to excite the Ru-dye, which was adsorbed onto the surface of the ZnO. The ZnS layer is believed to provide an alternative pathway for electrons to move across ZnO barriers. This alternative pathway with the composite layer structure provides higher power efficiency than does a single layer of ZnO or ZnS. A hole-injecting, p-type poly(3,4-ethylenedioxythiophene) (PEDOT) thin film was also introduced to substitute for the Pt catalytic layer which helps with the rejuvenation of I⁻ ions. Although the p-type semiconductor behavior increased the open circuit voltage (V_oc), the power efficiency decreased because the I⁻ rejuvenation rate was much slower on PEDOT than on Pt.     

Electrochemical supercapacitor electrode material based on poly(3,4-ethylenedioxythiophene)/polypyrrole composite

Poly (3,4-ethylenedioxythiophene)/polypyrrole composite electrodes were prepared by electropolymerization of 3,4-ethylenedioxythiophene (EDOT) on the surface of polypyrrole (PPy) modified tantalum electrodes. The morphology observation of PPy and poly(3,4-ethylenedioxythiophene)/polypyrrole composite (PEDOT/PPy) was performed on Field Emission Scanning Electron Microscope (SEM). The electrochemical capacitance properties of the composite were investigated with cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS) techniques in the two- or three-electrode cell system. The results show that the PEDOT/h-PPy (PPy with horn-like structure) composite films were characterized with highly porous structure, which leads to their specific capacitance as 230 Fg⁻¹ in 1 M LiClO₄ aqueous solutions and even 290 Fg⁻¹ in 1 M KCl aqueous solutions. Moreover, the composite exhibits a rectangle-like shape of voltammetry characteristics even at scanning rate 100 mV s⁻¹, a linear variation of the voltage with respect to time without a clear ohm-drop phenomenon in galvanostatic charge–discharge process and almost ideal capacitance behavior in low-frequency in 1 M KCl solutions. Furthermore, specific power of the composite would reach 13 kW kg⁻¹ and it had good cycle stability. All of the above imply that the PEDOT/h-PPy composites were an ideal electrode material of supercapacitor.     

The effects of hyperbranched poly(siloxysilane)s on conductive polymer aluminum solid electrolytic capacitors

An aluminum solid electrolytic capacitor, using poly-(3,4-ethylenedioxythiophene) (PEDOT) as a counter electrode, was prepared with hyperbranched poly(siloxysilane)s (HBPSi) that has a large number of vinyl groups to improve the interfacial properties between aluminum oxide and PEDOT. Capacitance and equivalent series resistance (Rs) were significantly improved compared to untreated oxide film and vinyl terminated polydimethylsiloxane coated interfaces. From electrochemical measurement of the withstand voltage, damage to the oxide film from chemical polymerization of PEDOT was less with the HBPSi treatment. Frequency characteristics and electrical conductivity measurements of the polymer indicated that the resistance inside the etched porous layer was greatly reduced. These results show that the HBPSi pre-coating layer inhibited degradation of the oxide film by chemical polymerization of PEDOT and the conductivity of PEDOT in the etched porous oxide layer, and also enlarges the contact area by improving interfacial adhesion.     

Electrochemical fabrication of long-term stable Pt-loaded PEDOT/graphene composites for ethanol electrooxidation

Layered electrochemically reduced graphene oxide (ER-GO) sheets incorporated with poly(3,4-ethylenedioxythiophene) (PEDOT) have been fabricated as an efficient support for Pt nanoparticles on a glassy carbon (GC) electrode. The as-prepared Pt-loaded PEDOT/ER-GO composite electrode exhibits not only the high mass peak current density (390 A g⁻¹) but also the good long-term catalytic stability toward the ethanol electrooxidation. The Pt/PEDOT/ER-GO also shows stronger tolerance to poisoning species compared with the commercial JM 20% Pt/C electrode. The high electrocatalytic activity of Pt/PEDOT/ER-GO is mainly described to the good electrochemical activity of PEDOT/ER-GO composites and the well-dispersed Pt nanoparticles resulting in the large electrochemical active surface area of Pt (47.1 m² g⁻¹).     

Improvement of the electrochemical properties via poly(3,4-ethylenedioxythiophene) oriented micro/nanorods

Arrays of oriented poly(3,4-ethylenedioxythiophene) (PEDOT) micro/nanorods are synthesized by electrochemical galvanostatic method at the current density of 1 mA cm⁻² in the cetyltrimethylammonium bromide (CTAB) aqueous solution whose pH value is 1. The CTAB is used both as the surfactant and the supporting salt in the electrolyte solution. The electrochemical properties of PEDOT films are characterized by cyclic voltammetry and galvanostatic charge/discharge techniques, which indicate that the arrays of oriented PEDOT micro/nanorods can be applied as the electrode materials of supercapacitors. In addition, the cycling performance of PEDOT micro/nanorods is much better than that of traditional PEDOT particles. The effects of the concentration of CTAB, the current density, and pH value of electrolyte solutions on the morphologies and electrochemical properties of PEDOT films are investigated. The mechanism of different morphologies formation is discussed in this study as well.     

Porous NiO/poly(3,4-ethylenedioxythiophene) films as anode materials for lithium ion batteries

NiO/poly(3,4-ethylenedioxythiophene) (PEDOT) films are prepared by chemical bath deposition and electrodeposition techniques using nickel foam as the substrate. These composite films are porous, and constructed by many interconnected nanoflakes. As anode materials for lithium ion batteries, the NiO/PEDOT films exhibit weaker polarization and better cycling performance as compared to the bare NiO film. Among these composite films, the NiO/PEDOT film deposited after 2 CV cycles has the best cycling performance, and its specific capacity after 50 cycles at the current density of 2 C is 520 mAh g⁻¹. The improvements of these electrochemical properties are attributed to the PEDOT, a highly conductive polymer, which covers on the surfaces of the NiO nanoflakes, forming a conductive network and thus enhances the electrical conduction of the electrode.     

Photoelectrochemical studies of the junction between poly[3-(4-octylphenyl)thiophene] and a redox polymer electrolyte

The photoelectrochemical properties of all-solid-state photoelectrochemical cell constructed from a conjugated polymer poly[3-(4-octylphenyl)thiophene] and an amorphous poly(ethylene oxide) complexed with iodide/triiodide redox couple were studied. In order to develop flexible photoelectrochemical cells, we have used a transparent polymeric metal, doped poly(3,4-ethylenedioxythiophene), as a counter electrode. It was shown that poly(3,4-ethylenedioxythiophene) improved the charge transfer between indium tin-oxide and iodide/triiodide redox couple. The spectral response, photocurrent time, and open-circuit voltage and short-circuit current dependence on light intensity have been studied. The photon to electron conversion efficiency obtained was low. The photocurrent and photovoltage dependence studies on light intensity indicate exciton recombination and/or traps as limiting factors.     

Chemical modification of Nafion membrane with 3,4-ethylenedioxythiophene for direct methanol fuel cell application

Nafion 117 membranes were modified by in situ chemical polymerization of 3,4-ethylenedioxythiophene using H₂O₂ as oxidant for direct methanol fuel cell application. Methanol permeability and proton conductivity of the poly(3,4-ethylenedioxythiophene)-modified Nafion membranes as a function of temperature were investigated. An Arrhenius-type dependency of methanol permeability and proton conductivity on temperature exists for all the modified membranes. Compared with Nafion 117 membrane at 60 °C, the methanol permeability of these modified membranes is reduced from 30% to 72%, while the proton conductivity is decreased from 4% to 58%, respectively. Because of low methanol permeability and adequate proton conductivity, the DMFC performances of these modified membranes were better than that of Nafion 117 membrane. A maximum power density of 48.4 mW cm⁻² was obtained for the modified membrane, while under same condition Nafion 117 membrane got 37 mW cm⁻².     

Pulse electrodeposited PtSn electrocatalyst on a PEDOT/graphene-based electrode for ethanol oxidation in an acidic medium

Pulse electrodeposition of Pt and Sn using 10 mM H₂PtCl₆?6H₂O in 0.10 M H₂SO₄ and 10 mM SnCl₂?2H₂O in 0.10 M HCl was conducted on a support matrix consisting of electropolymerized poly (3,4-ethylenedioxythiophene) (PEDOT) and electrochemically exfoliated graphene oxide (EGO). The Field Emission – Scanning Electron Microscopy (FE-SEM) studies of PtSn/PEDOT/EGO (i.e., PEDOT on EGO) showed a homogeneous globular composite, while PtSn/EGO/PEDOT (i.e., EGO on PEDOT) revealed a heterogeneous composite with wrinkled and globular surface morphologies. An Energy Dispersive X-ray (EDX) analysis (as a percentage of Pt and Sn) of PtSn/PEDOT/EGO is in agreement with the X-ray Photoelectron Spectroscopy (XPS) analysis, indicative of a homogeneous surface for the dispersion of metallic particles. However, the EDX and XPS analyses of PtSn/EGO/PEDOT showed variations in the amount of Pt and Sn, indicative of possible mixing of the EGO and PEDOT support matrices. Cyclic voltammetry (CV) and chronoamperometry using 1.0 M ethanol in 0.1 M H₂SO₄ demonstrated higher electrocatalytic activity (83.7 mA/cm²) and electrochemical stability (29.0% current retention) in PtSn/PEDOT/EGO than PtSn/EGO/PEDOT.     

Paper-based, printed zinc–air battery

A flexible battery is printed on paper by screen-printing a zinc/carbon/polymer composite anode on one side of the sheet, polymerising a poly(3,4-ethylenedioxythiophene) (PEDOT) cathode on the other side of the sheet, and applying a lithium chloride electrolyte between the two electrodes. The PEDOT cathode is prepared by inkjet printing a pattern of iron(III)p-toluenesulfonate as a solution in butan-1-ol onto paper, followed by vapour phase polymerisation of the monomer. The electrolyte is prepared as a solution of lithium chloride and lithium hydroxide and also applied by inkjet printing on to paper, where it is absorbed into the sheet cross-section. Measurements on a zinc/carbon-PEDOT/air battery in a similar configuration on a polyethylene naphthalate substrate shows a discharge capacity of up to 1.4 mAh cm⁻² for an initial load of 2.5 mg zinc, equivalent to almost 70% of the zinc content of the anode, which generates 0.8 V at a discharge current of 500 μA. By comparison, the performance of the paper-based battery is lower, with an open-circuit voltage of about 1.2 V and a discharge capacity of 0.5 mAh cm². It appears that the paper/electrolyte combination has a limited ability to take up anode oxidation products before suffering a reduction in ionic mobility. The effects of different zinc/carbon/binder combinations, differences in application method for the zinc/carbon composite and various electrolyte compositions are discussed.     

Poly[dithio-2,5-(1,3,4-thiadiazole)] (PDMcT)–poly(3,4-ethylenedioxythiophene) (PEDOT) composite cathode for high-energy lithium/lithium-ion rechargeable batteries

We present a characterization of the redox behavior of organosulfur-based composite cathodes composed of poly[dithio-2,5-(1,3,4-thiadiazole)] (PDMcT), which is a polymer derived from 2,5-dimercapto-1,3,4-thiadiazole (DMcT), and poly(3,4-ethylenedioxythiophene) (PEDOT) in a carbonate-based mixed solvent containing 1.0 M LiBF₄. We have previously shown that PEDOT films, electrochemically generated at glassy carbon electrode surfaces, gave rise to a dramatic enhancement of the interfacial charge transfer kinetics of DMcT in solution. In a similar fashion, chemically prepared PEDOT films exhibited dramatic electrocatalytic activity towards the redox reactions of PDMcT in the composite cathodes. While the composite cathode exhibited a very high capacity of 205 mAh g⁻¹ (based on the electroactive mass) at the first discharge, in subsequent charge/discharge tests, the capacity of the PDMcT–PEDOT composite cathode (1:1 mole ratio) decreased significantly because of dissolution of the reduction products of PDMcT into the electrolyte solution. We also found that an ionic polymer, consisting of a mixture of PEDOT and polystyrene sulfonate (PEDOT–PSS) could electrostatically, but not physically, prevent, at least in part, leaching of the DMcT species into the electrolyte solution, thus improving the coulomb efficiency for the redox reactions of DMcT in a PDMcT–PEDOT composite film during charge/discharge cycles.     

Electropolymerization of high stable poly(3,4-ethylenedioxythiophene) in ionic liquids and its potential applications in electrochemical capacitor

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been successfully electropolymerized using a purified 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) as both the growth medium and the supporting electrolyte. The electrochemical performance of the PEDOT thin film was investigated in 1 mol L⁻¹ H₂SO₄ solution. It possesses nearly ideal capacitive property, and its specific capacitance is about 130 F g⁻¹. Compared with other conducting polymers, enhanced cycling lifetime (up to 70,000 cycles), which is close to that of active carbon materials, was observed on repetitive redox cycling.     

Electrodeposition of manganese dioxide in three-dimensional poly(3,4-ethylenedioxythiophene)–poly(styrene sulfonic acid)–polyaniline for supercapacitor

The preparation of composites of precise metal oxides/conducting polymers is important in studies of supercapacitors. In this work, a three-dimensional matrix of poly(3,4-ethylenedioxythiophene)–poly(styrene sulfonic acid)–polyaniline (PEDOT–PSS–PANI) was prepared by interfacial polymerization of ANI into PEDOT–PSS. Conductivity was enhanced by incorporating of PANI into PEDOT–PSS because of the decrease in the distance for electron shuttling along the conjugated polymeric chain. Composite electrodes were prepared by the electrodeposition of manganese dioxide (MnO₂) in a PEDOT–PSS–PANI three-dimensional matrix. The electrodes were characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry techniques. The results show a significant improvement in the specific capacitance of the composite electrode. For PEDOT–PSS the specific capacitance was of 0.23 F g⁻¹, while PEDOT–PSS–PANI and PEDOT–PSS–PANI–MnO₂ displayed values of 6.7 and 61.5 F g⁻¹, respectively. When only considering the MnO₂ mass, the composite had the specific capacitance of 372 F g⁻¹. The composite also had an excellent cyclic performance.     

Fabricating red-blue-switching dual polymer electrochromic devices using room temperature ionic liquid

In this work, room temperature ionic liquid (RTIL)—1-butyl-3-methyl-imidazolium hexafluorophosphate ([BMIM]PF₆)—was employed to fabricate dual polymer electrochromic devices (DPECDs). [BMIM]PF₆ was used as the electrolyte both in the electrochemical synthesis of conducting polymers (CPs) and in the fabrication of DPECDs. The electrochemically deposited poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3-methylthiophene) (PMeT) were employed to serve as two complementary coloring electrochromic thin films. Through combining these two electrochromic layers, the assembled DPECDs were found to switch between deep red and deep blue, which are two primary colors for a display. By employing RTIL as electrolyte, the devices retained 65% of their optical contrast and electroactivity after 5×10³ deep double potential steps, showing enhanced stability and durability. The DPECDs also exhibited stable electrochromic performance, with a maximum optical contrast of 26% at 665 nm, and achieved a high coloring efficiency of 460 cm² C^-1.     

Significant effects of poly(3,4-ethylenedioxythiophene) additive on redox responses of poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) cathode for rechargeable Li batteries

Redox behaviors of the poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM)-coated electrodes composited with carbon black (CB) or poly(3,4-ethylenedioxy-thiophene) (PEDOT) are presented. Effects of PEDOT additive on the redox activity of PDBM were investigated to apply their composite materials as candidates of cathodes for rechargeable lithium batteries. The film having a PEDOT/PDBM with weight ratio of 1/1 shows a gravimetric capacity of 129 mAh g⁻¹ (corresponding to 188 mAh g⁻¹ for PDBM and 70 mAh g⁻¹ for PEDOT). The highest energy density observed was 140 mAh g⁻¹ (406 mWh g⁻¹) for the composite cathode. Good cycle-ability over 100 cycles was attained with a PEDOT/PDBM composite cathode.     

Proton diffusion in polyethylene oxide: Relevance to electrochromic device design

Polyethylene oxide is a frequently used component in polymer electrolytes developed for applications in electrochromic devices. The transmittance variation may occur as a result of either proton or lithium ion intercalation into the electrochromic films. Impedance spectroscopy data in the low-frequency space-charge relaxation regime can be used to obtain estimates of ion concentrations and ion diffusion coefficients in ion-conducting materials. We apply this method to literature data for pure polyethylene oxide where the residual conductivity is believed to be due to protons. The obtained diffusion coefficient is found to be in the order of, or higher than, reported lithium ion diffusion coefficients in low molecular weight polyethylene oxide. Hence it is likely that proton intercalation will be of importance for electrochromic devices, provided there is a significant amount of protons present.