n- and p-Doped Poly(3,4-ethylenedioxythiophene):  Two Electronically Conducting States of the Polymer

Abstract

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.

The electronic structure of n- and p-doped phenyl-capped 3,4-ethylenedioxythiophene trimer

“…It can be concluded that well controlled n-type doping of the EDOT trimer is difficult to achieve, and the electrical properties of n-doped material are expected to be poor. This is in agreement with the results of previous studies of n-doped PEDOT, 25 which proved to have a much lower electrical conductivity than its p-doped counterpart, and was extremely unstable in air.…”

“…25 Nevertheless, n-doped PEDOT proved to be unstable even in a dry oxygen-free environment, and its maximum conductivity was about 1% of that of p-doped PEDOT. It is therefore interesting to study the electronic structure of both p-and n-doped EDOT trimer.…”

Biomimetic Sensing – Actuators Based on Conducting Polymers

“…Some CP such as PEDOT (Ahonen et al 2000;Skompska et al 2005), polythiophene (Arbizzani et al 1995) or polyfluorenes (Ranger & Leclerc 1998) have an electronic affinity high enough to allow transitions from the neutral state to a reduced state, enabling them to store negative charges (by electron injection) on the chains at high cathodic potentials. In this case very stable solvents and salts are required, as electrolytes, to perform this reaction (3).…”

Electrochemical and Photovoltaic Properties of Electropolymerized Poly(thienylsilole)s

“…A good example is poly(ethylene dioxythiophene) (PEDOT), a very well-known conducting polymer which, however, features very limited n-dopability. 29 One possible explanation of such behaviour is that silole-containing polymers fail to form extended electronic states, such as bipolarons, upon their reduction. Such behaviour was noted for PEDOT and is considered to be responsible for its low dopability and electronic conductivity in the cathodic potential range.…”

“…Such behaviour was noted for PEDOT and is considered to be responsible for its low dopability and electronic conductivity in the cathodic potential range. 29 Electrochemical and chemiluminescence studies of a number of silole-containing molecules 14,30 suggest that reduction of the silole moiety may result in the formation of highly localized excited species with the negative charge centered on the silole. These excited states are also quite unreactive, as suggested by their long lifetimes.…”