Field effect on polaron dynamics and charge transport in conducting polymers

We investigate the formation and motion dynamics of polarons in one-dimensional conjugated polymers within the extended Su-Schrieffer-Heeger model combined with an adiabatic dynamics method. In the presence of external electric fields, the initial location of the polaron is stressed and concerned with the charge transport property of organic semiconductors. Three regimes for the electric fields are categorized in terms of the forming place of the polaron. In the low field strength regime, the polaron is formed around the center of the chain and thus the charge undergoes a long-time travel before being extracted into the electrode because of the strong electron and phonon (e-p) interaction. In the intermediate strength regime, the polaron is formed near the chain end. Due to the chain-end scattering, the electron mobility increases in linear relation with the field strength. In the high strength regime, the polaron is formed at the chain end. This results in a nonlinear enhancement in the electronic mobility, in agreement with the experimental observations on the field dependent transient photocurrent in poly(phenylene vinylene). The electron-electron correlation, as well as the field mode effect on polaron dynamics, is also discussed.