ELECTRON-TRANSPORT IN ACCEPTOR-DOPED POLYMERS - THE ROLE OF GROUP DIPOLE-MOMENTS

Electron mobilities have been measured in poly(styrene) doped with an isomer mixture of two diphenoquinone (DPQ) compounds over a range of fields, temperatures, and DPQ concentrations. The results are interpreted within the framework of a formalism based on disorder, due to Bassler and coworkers. The formalism is based on the assumption that charge transport occurs by hopping through a manifold of localized states with superimposed energetic and positional disorder. The key parameter of the formalism is the energy width of the hopping site manifold. For DPQ doped poly(styrene), the energy width is 0.118 eV and independent of the intersite distance or DPQ concentration. The width can be described by a model based on dipolar disorder, if it is assumed that the fluctuations of hopping site energies are due to group dipole moments associated with the carbonyl groups of the DPQ molecules. The interpretation of the experimental results leads to the further conclusion that polaronic effects need not be invoked to explain transport phenomena in this class of doped polymers. (C) 1995 John Wiley & Sons, Inc.