The mobility of charge carriers in amorphous organic materials like conjugated (CPs) and molecularly doped polymers (MDPs) is typically several orders of magnitude lower than in crystals. The particular interpretation of experiments differs from case to case, but usually assumes an incoherent, activated motion between "sites" representing an abstraction for an atom, a molecule or an oligomer unit. Charging and discharging these polarizable entities induces local distortions "dressing" the particle's effective mass and energy. Electron transfer implies moving the confined topological defect. Transport models differ in the relative importance of both contributions.
CPs primarily conduct along their hydrocarbon-chain's Peierl's-distorted and therefore semiconducting segments. The distribution of their lengths is caused by disrupting kinks and cross-links, increasing disorder and hence trap-liability as compared to the corresponding oligomers. Contrarily, the polymer matrix in MDPs mainly serves as an inert spacer separating the strongly localized dopant molecules. Nevertheless, conduction in CPs and MDPs is similar in some important respects, like the impact of energetic and positional disorder on the mobility's field-dependence: high fields may occasionally decrease the mobility in both polymer types in spite of their barrier-lowering effect. Baessler's Gaussian disorder model (GDM) predicts this anomaly in terms of a biased random walk and provides a simple interpretation applicable to CPs as well as to MDPs: high fields can force electrons to avoid the fast channels and move along retarding paths and dead ends characterized by a poor orbital overlap.
A Monte Carlo simulator designed for simultaneous excitation, recombination and diffusion within the conjugated pi-orbitals of CP- and MDP-samples has been implemented. Objects and procedures for all relevant sets of molecular structures have been programmed. Energetic patterns were modeled according to the GDM. While Pauli's principle and Hubbard's repulsion have been included for electron-electron interactions, excitonic binding energies will govern the forces between electrons and vacancies. Injection and ejection of electrons at the contacts as well as polymer-polymer interfaces are representable. Neglecting multiphonon-processes involving the participation of numerous intermediate states, the simulator's prototype will approximate the system's phase-space traversal by Abraham-Miller's thermally assisted tunneling mechanism, driving the system ergodically towards its states of lowest free energy.