Electrical conduction mechanism in conjugated polymers studied using Flicker noise spectroscopy

Abstract

We have performed detailed analysis of the fluctuations of the electrical current in electrochemically deposited conductive polymers (CP) using as example polyaniline and poly(3methylthiophene). These heterogeneous and disordered materials cannot be analyzed in terms of classical conduction mechanisms (like Schottky or Poole-Frenkel emission). Instead, the electrical transport in CPs is to be considered as a stochastic process with large component of noise. We have been able to distinguish several modes of the conduction process in CPs by applying Flicker Noise Spectroscopy. Thus, we have established that the transport of charge carriers in highly doped CPs is much less correlated than in non-doped ones at the same electric field strength. While applied electric field increases, correlations become lower in a sequence of elementary events contributing to the conductivity of CP. Apparently, the change in the correlation length corresponds to changing mechanism of the electrical conduction. The lower correlation in highly doped sample can be attributed to various factors including change in CP conformation, enhancement in interchain charge transfer and generation of polaron lattice.

Polarons, Compressed Polarons, and Bipolarons in Conjugated Polymers

“…Once each “even-numbered” polaron is paired, K d for dissociation of counterions from the “odd” polarons would be decades larger, approaching K d for isolated polarons. A number of polarons in a chain have been considered to form a “polaron lattice”. − If so it is plausible that counterions form a superlattice upon such a polaron lattice.…”

Review on Conductive Polymer Composites for Supercapacitor Applications

“…A continuous array of "p" orbitals that can align to provide a bonding overlap over the entire system is needed for a conjugated system. The condition arises when two systems are "linked together", such as double bonds, and improves the extension of the chemical reactivity that results in an increase in the conductivity of the electrons [12]. Thirdly, the introduction of dopants or charge carriers (either charge carrier's holes or charge carrier electrons) is of great importance.…”