Microstructure-dependent electrochemical properties of chemical-vapor deposited poly(3,4-ethylenedioxythiophene) (PEDOT) films (original) (raw)
Related papers
Polymer electronic materials: a review of charge transport
Polymer International, 2006
This article presents an overview of the charge transport phenomenon in semiconducting polymer materials. In these disordered systems both intrinsic and extrinsic parameters play significant roles. In general, π-electron delocalization, interchain interaction, band gap, carrier density, extent of disorder, morphology and processing of materials determine the electrical and optical properties. The chemical structure, especially the role of side groups, is quite important in both physical and processing properties. The nature of charge carriers and their role in charge transport depend on the structure and morphology of the system. Hence in several semiconducting polymer devices, the correlations among structure, morphology and transport are rather strong. The dependence of carrier mobility on temperature and electric field needs to be understood in the framework of competing models based on carrier hopping, trapping/detrapping and tunneling. Exactly what determines the dispersive/nondispersive, polaronic and correlative transport regimes is yet to be quantified. An understanding of the carrier mobility in semiconducting polymers is necessary to optimize the performance of polymeric electronic devices.
The Journal of Physical Chemistry C, 2010
Conducting polymers have widespread industrial applications owing to a unique combination of mechanical, optical, and electronic properties. Specifically, the family of poly(alkylenedioxythiophene) derivatives has received much attention due to its inherently high conductivity, environmental stability, and tunability. However, although the electron-donating characteristics of the alkoxy moieties are well-known, the source of the differences among these substitutions has been limited to speculative arguments based on bulk properties. To address these issues, a combined electrochemical and density functional theory (DFT) study was undertaken that reveals the significant electronic and geometric characteristics responsible for the comparative properties of these materials. It was found that the geometry of the alkylenedioxy backbone substitution modulates the π-donating character of the oxygen and that this directly influences the onset of p-doped conductivity. These studies also indicate that this framework equally applies to several other heterocyclic polymer systems. An improved theory for these materials is expected to provide the insight and knowledge base for new conducting polymers with enhanced stability and optoelectronic properties.
Tuning of Electronic Properties in Conducting Polymers
Collection of Czechoslovak Chemical Communications, 2001
Structural and electronic transitions in poly(thiophenyleneiminophenylene), usually referred to as poly(phenylenesulfidephenyleneamine) (PPSA) upon electrochemical doping with LiClO4 have been investigated. The unusual electrochemical behavior of PPSA indicates that the dopant anions are bound in two energetically different sites. In the so-called "binding site", the ClO4- anion is Coulombically attracted to the positively charged S or N sites on one chain and simultaneously hydrogen-bonded with the N-H group on a neighboring polymer chain. This strong interaction causes a re-organization of the polymer chains, resulting in the formation of a networked structure linked together by these ClO4- Coulombic/hydrogen bonding "bridges". However, in the "non-binding site", the ClO4- anion is very weakly bound, involves only the electrostatic interaction and can be reversibly exchanged when the doped polymer is reduced. In the repeated cycling, the continuous an...
Morphology and Charge Transport in Conjugated Polymers
Journal of Macromolecular Science, Part C: Polymer Reviews, 2006
Determining the relationship between charge transport and morphology is key to increasing the charge carrier mobility of conjugated polymers. This review details a fundamental study of the charge transport and morphology of regioregular poly(3-hexylthiophene) and sets out general principles for obtaining high charge carrier mobilities. The basis for this study was the finding that despite being more crystalline, low molecular weight films have a substantially lower mobility than high-MW films. An examination of this apparent contradiction is used to provide insight into how the charge carriers move through a conjugated polymer film and provide a model for charge transport.
Organic Electronics, 2007
The charge transport properties in a novel electroluminescent poly{[2-(4 0 ,5 0 -bis(3 00 -methylbutoxy)-2 0 -p-methoxy-phenyl)phenyl-1,4-phenylene vinylene]-co-(9,9-dioctyl-2,7-fluorenylene vinylene)} (BPPPV-PF) have been studied using a time-of-flight (TOF) photoconductivity technique. The TOF transients for holes were recorded over a range of temperatures (207-300 K) and electric fields (1.5 · 10 5 -6.1 · 10 5 V/cm). The hole transport in this polymer was weakly dispersive in nature with a mobility at 300 K of 5 · 10 À5 cm 2 /V s at 2.5 · 10 5 V/cm. This increased to 8.4 · 10 À5 cm 2 /V s at 6.1 · 10 5 V/ cm. The temperature and field dependence of charge mobility has been analyzed using the disorder formalisms (Bässler's Gaussian disorder model (GDM) and correlated disorder model (CDM)). The fit with Gaussian disorder (GDM) model yielded the mobility pre-factor l 1 = 1.2 · 10 À3 cm 2 /V s, energetic disorder parameter r = 82 meV and positional disorder parameter R = 1.73. The average inter-site separation (a = 7 Å ) and the charge localization length (L = 3.6 Å ) was estimated by assuming the CDM type charge transport. The microscopic charge transport parameters derived for this polymer are almost identical to the reported values for fully conjugated polymers with high chemical purity. The results presented indicate that the charge transport parameters can be controlled and optimized for organic optoelectronic applications.
n- and p-Doped Poly(3,4-ethylenedioxythiophene): Two Electronically Conducting States of the Polymer
Macromolecules, 2000
Neutral poly(3,4-ethylenedioxythiophene) (PEDOT) thin films can be switched to an electronically conducting form either by oxidation (p-doping) or reduction (n-doping) in anhydrous organic solvents. The maximum attainable n-conductivity is ca. 1% of the maximum p-conductivity. However, based on spectroelectrochemical and in-situ conductance measurements, the p-conductivity regime can be divided into two domains, in which either positive polarons or bipolarons and free carriers are the major charge carriers. In the n-conductivity regime, voltammetric, spectral, and conductance data suggest only the generation of negative polaron-type carriers. These results imply that the conductivity due to positive or negative polarons is of the same order of magnitude and that the higher maximum p-conductivity may be attributed to the generation of other charge carriers in the highly stable oxidized PEDOT films. The reduced form is not stable even in an extremely dry oxygen-free environment, which severely hampers the use of n-doped PEDOT in practical applications. The conductivity of pristine PEDOT films can be markedly enhanced by successive p-doping and undoping. In addition, the conductance slowly increased after an anodic potential step. The origin of these effects is not known.