Predictions of Hole Mobility in Molecular Organic Crystals: Incorporating Thermal Effects

A reliable, cost-efficient method to compute hole mobility, mu, in organic molecular solids would contribute to the development of organic electronic devices by offering a method to rapidly screen a wide variety of materials for desirable transport properties. An existing protocol due to Deng and Goddard(1) [J. Phys. Chem. B 2004, 108, 8614-8621] utilizes Marcus-Hush theory to calculate hole mobility. We have extended the method to account for thermal effects in a way that allows for anisotropy in the interaction, potential between molecular monomers. This is accomplished by applying Boltzmann statistics to a discrete representation of the interaction potential to approximate the monomer distribution function. We further show how to improve efficiency by employing a hybrid of DFT and AM1 electronic structure data. DFT is used to obtain information about the molecular monomer and AM1 methodology is used for calculations of dimer-based properties. The hybrid method is very efficient and the calculated values of hole mobility fall within the observed range of experimental values.