Drift and diffusion in disordered organic semiconductors: The role of charge density and charge energy transport

Using Monte Carlo simulations, we revisited charge transport in degenerate disordered organic semiconductors that are characterized by hopping transport. We found that, when a non-negligible fraction of the molecules is ionized (i.e., high charge density), charge transfer (transport) involves transfer of energy as well. Although Monte Carlo simulations confirm that, at low electric fields, the generalized Einstein relation describes the relation between drift and diffusion well, the use of the energy flux model provides a more intelligible and transparent description of the phenomenon at hand, enabling its generalization under the same premise as the thermoelectric effect and establishing a basis for the monitoring of charge-carrier energy trajectories within the traversed media.