Inhomogeneous Dopant Distribution in Organic Semiconductors: Causes and Consequences for Charge Transport

While the effect of the incorporation of dopant molecules on the microstructure of the host material has been intensely investigated, translating these results to electronic properties has received less attention. Here, we will show two case studies of inhomogeneous dopant distribution in organic semiconductors, for which we do a quantitative comparison between experimental data of dopant distributions and conductivity and numerical simulations thereof. For the latter we developed two intuitive tools to produce simplified yet realistic morphologies of doped organic polymers, accounting for the effects of (a) aggregation and phase separation in the semiconducting host material and of (b) diffusion and preferential incorporation in specific phases of the dopant. The created morphologies are then used as starting point for kinetic Monte Carlo simulations of charge transport. Importantly, the case studies can be generalized to design rules to achieve high conductivity at low dopant concentrations.