(773c) Semiflexible Polymer Model for Charge Mobility in Liquid Crystalline Organic Semiconductors

Semiconducting polymers play an important role in a wide range of optical and electronic material applications. It is widely accepted that molecular ordering and mesoscale morphology impact charge transport in such devices. However, connecting molecular order to device performance is difficult due to a critical need for a comprehensive theory of charge transport in semiconducting polymers. We have developed a molecular model of charge transport that captures the complex trajectory of a charge undergoing intrachain and interchain hopping through an amorphous conjugated-polymer environment. Charge transport in amorphous semiconducting polymers is often enhanced by liquid crystalline phases in a film. We extend our model of charge hopping to address the impact of nematic ordering on charge transport. These effects are modeled using a molecular-level physical description of nematic ordering rather than a phenomenological description; thus, our predictive approach is amenable to direct materials design. The nematic field acts to elongate the polymer chains, and our model is used to study the conformational elongation and the resulting effect on overall mobility through the film at different time scales. We further extend the model to a two-polymer, one-solvent system with a low molecular weight polymer acting as a nematogen for high molecular weight polymers that bridge liquid crystalline phases. We study the phase transitions of such a system and examine the effect of concentration ratio and degree of elongation on the charge mobility.