Mobility reduction and apparent activation energies produced by hopping transport in the presence of Coulombic defects

A Monte Carlo simulation is proposed to study the mobility reduction due to Coulombic defects for hopping transport in a one-dimensional regular lattice. Hops between energetically equivalent sites and within an exponential distribution of energy levels are considered. In the absence of Coulombic wells, the calculations reproduce the well known features of Gaussian and highly dispersive transport respectively. When the field due to Coulombic potential wells is superimposed on the applied one, the macroscopic conduction features change dramatically. The computed apparent mobilities or transit times exhibit a Poole-Frenkel character and a modified Arrhenius temperature dependence. Their activation energy differs from the mean energy characterizing hops at the microscopic scale and it is found to depend on parameters such as the defect charge. This has important practical consequences for data interpretation.