Hole hopping in dimers of N,N' di(1-naphthyl)-N,N'-diphenyl-4,4'-diamine (α-NPD): a theoretical study.

Hole-hopping parameters for Marcus-like charge transport, Marcus hole hopping rates, and hole mobilities are calculated for a series of model dimers of a typical hole-transporting material α-NPD using multireference quantum chemistry. The parameters are extracted from the two-state energy profiles built for charge hopping between two states with a hole localized on each of the monomers. The dependence of the hopping integral on the intermolecular arrangement in the dimer is studied. It is shown that at short intermolecular distances strong orbital interactions between molecules cause a drastic increase in the hopping integral and, therefore, in the hopping rate.