Activation energies of charge transport in doubly-doped polymers: polarons and disorder

We have measured the thermal activation energies of charge carrier mobilities in polycarbonate doped with two similar hydrazone transport molecules. The results are consistent with polaron formation contributing a major fraction of the activation energy. The observations cannot be reconciled with the simple application of a model based on site energy disorder, although some type of disorder is necessary to account for the observed dispersive behavior and the anomalous broadening of the transients. © 1992.