Hopping transport in molecularly doped polymers

Investigations have shown that charge transport in molecularly doped polymers depends on the permanent dipole moments of the dopants and the host repeat units. Transport is inhibited as a result of energetic disorder arsing from charge-dipole interactions. Energetic disorder of this nature is spatially correlated, so that the length scale over which substantial fluctuations occur is much larger than the average dopant separation, and it has been recently shown that the specific correlations arising from the algebraic falloff of the charge-dipole interaction give rise to field-dependent mobilities which obey the Poole-Frenkel law. In view of these results, the standard picture that charges in molecularly doped polymers are hopping amongst an array of dopants of vastly different energies must be modified to describe diffusive transport in a smoothly varying energetic landscape. This new paradigm is examined in the context of a recent experiment.