First principles calculations of anisotropic charge carrier mobilities in organic semiconductor crystals

TL;DR

This paper uses first principles quantum chemical calculations combined with a master equation approach to analyze the anisotropic charge carrier mobilities in organic semiconductor crystals, highlighting limitations of traditional methods and comparing results with experimental data.

Contribution

It introduces a more efficient master equation method for calculating charge mobilities and critically evaluates the common diffusion-based approach in organic semiconductors.

Findings

Good qualitative agreement with experimental data for pentacene and rubrene

The diffusion constant approach is often inappropriate for mobility calculations

Charge transport properties of fluorinated perylene bisimides are characterized

Abstract

The orientational dependence of charge carrier mobilities in organic semiconductor crystals and the correlation with the crystal structure are investigated by means of quantum chemical first principles calculations combined with a model using hopping rates from Marcus theory. A master equation approach is presented which is numerically more efficient than the Monte Carlo method frequently applied in this context. Furthermore, it is shown that the widely used approach to calculate the mobility via the diffusion constant along with rate equations is not appropriate in many important cases. The calculations are compared with experimental data, showing good qualitative agreement for pentacene and rubrene. In addition, charge transport properties of core-fluorinated perylene bisimides are investigated.