Charge transport in semiconducting polymers at the nanoscale

In crystalline small molecule organic semiconductors, the interplay between the charge transport mechanism and the crystal and molecular structure is nowadays comparably well understood due to the clearly defined morphology. Charge transport in polymeric semiconductors on the other hand is rather complex, for example, due to the substantial amount of conformational freedom of the polymer chains. In macroscopic devices, charge transport is characterized by alternating ordered and disordered phases with varying interconnections and structural defects, which implies that the influence of molecular weight and side-chains, polymer fiber alignment, and backbone rigidity has to be considered, since different transport mechanisms at various length scales from single chains to the macroscale can overlap. To fully understand transport in these systems, ideally, each length scale would be addressed individually before different processes can be joined in a macroscopic picture. In this Perspective, we focus on charge transport properties of polymeric semiconductors at the shortest possible length scales and discuss approaches that aim to make the short length scales still accessible for charge transport experiments.