Charge transport in π-conjugated polymers from extraction current transients

The transport properties, namely mobility, conductivity, and charge carrier concentration of three model polymers, regioregular poly(3-hexylthiophene) (RRPHT), poly(p-phenylene vinylene) (PPV), and a polyazomethine (PAM) are investigated by charge extraction in a linearly increasing voltage. We have numerically modeled the charge cartier transients including a Gaussian distribution of localized states and the typical Poole-Frenkel-type field-dependent mobility observed in these materials, and good agreement with measured values is obtained. From our calculation we can determine the reason for the field-dependent mobility, and we found that the field-dependent release time from the localized states, τ_R is very important in RRPHT and PPV, while PAM is governed by stochastic transport.