Photocurrent in conjugated polymers

TL;DR

This paper investigates the mechanisms of photocurrent generation in conjugated polymers, highlighting the dominance of polarons at low energies and the conditions favoring soliton tunnelling, which can be used to identify soliton conduction.

Contribution

It introduces a novel electric field assisted tunnelling model for photocurrent in conjugated polymers and distinguishes conditions favoring polaron versus soliton conduction.

Findings

Polarons dominate photocurrent at low photon energies.

Soliton tunnelling occurs when electric field exceeds confinement potential.

Photocurrent data can identify soliton conduction phenomena.

Abstract

Nonlinear photocurrent carriers in conjugated polymers, such as polarons, bipolarons and solitons, are considered at low photon energies where a tunnelling process is necessary. We show that polarons usually dominate the photocurrent I due to a novel electric field assisted tunnelling for which ln(I) ~ -E^{-2/3}. For near degenerate polymers an electric field E which exceeds the confinement potential and frequencies above twice the soliton energy, soliton tunnelling is favored. Photocurrent data can then be used to identify the remarkable phenomenon of soliton conduction.