The mobility in disordered molecular systems with energies given by a charge-induced dipoles interaction.

We investigate the field dependence of the mobility in a model for a disordered molecular system containing spatial and energetic disorders. In this model we assign an isotropic polarizability to each site and take the site energies to be the site polarization energies, the interaction energy of a charge in the given site with the induced dipoles in the neighboring sites. This model was shown, in a previous publication, to contain short-ranged energetic correlations and we show in this work that this correlation produces a charge mobility proportional to the exponential of the square root of the applied field, the Poole-Frenkel dependence observed in various disordered organic materials, over a significant range of fields.

Density of states and energetic correlation in disordered molecular systems due to induced dipoles.

We have considered two models for a system of disordered organic molecules: one based on a regular lattice with Gaussian site displacements and another based on a hard sphere distribution. The site energies were given by a charge-induced dipole interaction (the polarization energy). We obtained the density of states of both models and observed that it changes from a Gaussian to the density of states of a uniform site distribution, whose form was obtained analytically, depending on the degree of disorder in one model or the packing fraction in the other model.

The role of short-ranged energetic correlations in the mobility field dependence of disordered organic materials.

We studied the mobility of charge carriers in a model for disordered organic solids where the energies of the localized states are Gaussianly distributed with short-ranged correlations. We obtained an expression for the mobility as a function of electric field, temperature, energetic variance, and correlation radius. The temperature dependence obtained with short-ranged energetic correlations is different from that obtained with power-law decaying energetic correlations and suggests a possible way to distinguish the two types of correlations from the measured mobility.