Understanding Morphology-Mobility Dependence in PEDOT:Tos

We develop a multi-scale model to calculate a charge carrier mobility in conducting polymer PEDOT, as a function of the physico-chemical properties of the system. We start by calculating the morphology using molecular dynamics simulations. Based on the calculated morphology we perform quantum mechanical calculation of the transfer integrals between states in polymer chains and calculate corresponding hopping rates using the Miller-Abrahams formalism. We then construct a transport resistive network, calculate the mobility using the Master Equations and analyze the calculated mobility in terms of transfer integrals distributions and percolation thresholds. Our results provide theoretical support for the recent study (Noriega et al., Nature Mat., 2013) explaining why the mobility in polymers rapidly increases as the chain length is increased and then saturates for sufficiently long chains. Our study also provides the answer to the long-standing question whether the enhancement of the crystallinity is the key to designing high-mobility polymers. We demonstrate, that it is the effective π-π stacking, not the long-range order that is essential for the material design for the enhanced electrical performance.