Numerical approach to charge transport problems on organic molecular crystals

Abstract

Understanding the charge transport properties of molecular crystals, such as organic semiconductors, from the atomistic viewpoint is an important and serious issue in not only basic science but also in the design of various electron devices. First we introduce some problems in studying the charge transport of organic semiconductors. Then we present our theoretical study on charge transport using the time-dependent wave-packet diffusion (TD-WPD) method, taking polaron effects into account. As an example, we investigate the transport properties of pentacene crystals coupled with the inter- and intramolecular vibrations within the mixed Holstein-Peierls model, which describes both hopping and bandlike transport behaviors due to the formation of small and large polarons. Taking into account the static disorder, which inevitably exists in molecular crystals, we present the temperature dependence of charge-transport properties in competition among the thermal fluctuation of molecular motion, polaron formation, and static disorder.