Charge carrier energy disorder in polar amorphous organic thin films

We report Monte Carlo calculations of the charge carrier energy level disorder in polar amorphous organic solids arising from electrostatic interactions between polarizable molecular charge distributions. In contrast with previous reports in which the discrete molecular polarizibilities are modeled as a dielectric continuum having dielectric constant epsilon, our calculations take account of the molecular-scale polarization inhomogeneity. We find that the previously reported 1/epsilon scaling rule underestimates the charge carrier energy level disorder by more than a factor of 2 for typical values of epsilon. Such an underestimation strongly impacts the analysis of charge carrier transport in polar amorphous organic thin films, due to the strong dependence of the charge carrier mobility on the energy disorder.