We present a model to describe electrical transport in dense films of conju
gated polymers. The essen tial physical features of the model are as follow
s: (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 expla
ins the carrier density dependences of mobility observed in polymer diodes
and field effect transistors.