Optical probes of chain packing structure and exciton dynamics in polythiophene films, composites, and nanostructures

This mini-review on the photophysics of poly-alkyl thiophenes (e.g., P3HT) and its blends with electron-acceptor moeties such as fullerenes (e.g., PCBM) and carbon nanotubes focuses on highlights of recent literature on spectroscopic probes of exciton formation, diffusion, charge-separation, and transport in these materials. The literature in this area is vast: more than 3000 papers have been published in on P3HT (and related materials) and applications to organic solar energy harvesting devices over the last 20 years. Thus, no single review can capture the breadth and depth of this research. Here, we attempt to highlight some of the exciting new research efforts aimed at understanding photophysical processes in organic photovoltaic materials. This mini-review is organized as follows: First, a summary of the theoretical framework commonly used to describe fundamental physical processes of charge generation in organic (polymeric) semiconductor materials is presented. We then discuss recent exciting results on ultrafast spectroscopic probes of exciton dynamics in these materials. Finally, we present highlights of new research on polymer nanostructures (nanoparticles and nanofibers) and their exciting applications to organic photovoltaics. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012