Invited Paper NS1+PV-TuA7
Torsional Defects in Conjugated Polymers: Modeling and Nanostructured Photovoltaic Materials

Tuesday, November 10, 2009, 4:00 pm, Room A8

Conjugated polymers represent a promising class of organic semiconductors with potential applications in a variety of molecular devices. Poly(3-alkylthiophene)s, in particular, are garnering interest due to their large charge carrier mobility and band gap in the visible region of the spectrum. Defects play a pivotal role in determining the performance of polymer electronics, and yet the function of specific types of defects is still largely unknown. Density functional theory calculations of alkyl-substituted oligothiophenes are used to isolate the effect of static inter-ring torsion defects on key parameters such as electronic coupling between rings and band gap. These polymers are often modeled with very short backbones and without their side chains. These results demonstrate the shortcomings of this approach for modeling torsional disorder and identify a minimal acceptable model.¹ Two experimental systems, one based on block copolymers and the other on a hybrid oxide nanotube-polymer system, with nanoscale morphology rationally designed to minimize torsional disorder will also be discussed. Results have potential implications both for the fundamental understanding of intramolecular charge transport and for improving processing in organic optoelectronic devices.

¹ Use of the Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract #DE-AC02-06CH11357.