Center for Functional Nanomaterials Seminar

Semiconducting polymers are versatile materials used in a variety of electronic applications due to their affordability, ease of device manufacturing, and synthetic and opto(electronic) tunability. Unfortunately, they are also intrinsically poor conductors, which can result in low device efficiencies and shorter carrier lifetimes. The conductivity can be improved using a variety of methods, including controlling the morphology to improve carrier transport or introducing charge carriers using chemical dopants. In this talk, we describe experiments that use a combination of X-ray and neutron scattering techniques to understand how we can use morphology in semiconducting polymers to improve their charge transport properties. We will first aim to control and improve the electron transfer process in full organic photovoltaic devices. We show that using sequential processing, where the polymer and fullerene are deposited in two separate steps, we can control the device level mixing of polymer and fullerene. We then discuss a collection of studies focused on the morphological effects of molecular doping of semiconducting polymers. The goal is to understand the interplay between how polymer chain ordering and the location of the dopant counterion in the lattice control polymer conductivity. We end this talk looking to design an amphiphilic conjugated polyelectrolyte model system to control aggregation of polymer chains in solution, with the goal of straightening chains to reduce carrier trap sites caused by kinks that disrupt the π-conjugation. Overall, these results emphasize the importance of understanding and controlling the morphology of semiconducting polymers on multiple length-scales.