Molecular Geometry Fluctuation Model for the Mobility of Conjugated Polymers

We present a model to describe electrical transport in dense films of conjugated polymers. The essential physical features of the model are as follows: (i) thermal fluctuations in the molecular geometry of the polymer modify the energy levels of localized electronic states in the material, and (ii) the primary restoring force for these fluctuations is steric, which leads to spatial correlation in the energies of the localized electronic states. The model describes the electric field dependence of the mobility and explains the carrier density dependences of mobility observed in polymer diodes and field effect transistors.