Photocurrent in conjugated polymers

Non-linear 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 dominate the photocurrent I due to a novel electric-field-assisted tunnelling route for which ln I ∼ -E^-2/3. For near-degenerate polymers with an electric field E which exceeds the confinement parameter and frequencies near twice the soliton energy, soliton formation is favored. Photocurrent data can then be used to identify the remarkable soliton conduction.