Observation of the transition from adiabatic to nonadiabatic small polaron hopping in a molecularly doped polymer

The transition from adiabatic to nonadiabatic small polaron hopping has unique characteristics among hopping theories; an activation energy in the mobility that changes from being monotonically increasing with the mean distance between hopping sites, {ρ}, to being independent of {ρ}, and, simultaneously, an Arrhenius prefactor that changes from being independent of {ρ} to exponentially decreasing with {ρ}. We have observed such a transition for the first time in the hole mobilities of the molecularly doped polymer, tri-p-tolylamine:polycarbonate.