Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 16: Organic Semiconductors

HL 16.1: Talk

Tuesday, March 18, 2025, 09:30–09:45, H14

Modeling charge transport in organic semiconductors: why and when the conventional Miller-Abrahams rate is inappropriate — •Magdalena Dörfler, Heinz Bässler, Andrey Kadashchuk, Harald Oberhofer, and Anna Köhler — Universität Bayreuth, 95447 Bayreuth

A widely applied expression to model charge transport in organic semiconductors is the Miller-Abrahams rate, which describes the probability for charge transfer from one site, e.g. a molecule, to a neighboring site. However, the expression that is conventionally referred to as Miller-Abrahams rate is an approximation of a more general term. This approximation is only valid when energy differences between neighboring sites are large compared to the thermal energy. Here, we show the differences that result when charge transport is modelled by kinetic Monte Carlo simulations (KMC) using either of the two expressions. The widely used, approximate, rate can lead to serious errors in the magnitude and, more importantly, in the trends obtained for the temperature and field dependence of charge transport. The implications for modelling work and the interpretation of experimental data are discussed.

Keywords: Kinetic Monte Carlo; Organic field-effect transistors; Hopping transport; Miller-Abrahams; Charge transport