Effects of Diiodo-Alkane Additives to P3HT Thin Films for High Performance Electronic Applications

Abstract

Polymeric conjugated materials are very promising for developing future soft material-based semiconductors, conductors, electronic and optoelectronic devices due to their inherent advantages such as lightweight, flexible shape, low-cost, ease of processability, ease of scalability, etc. There are a number of ways to tune material properties via post-processing treatments such as annealing, solvent additives, or doping. One challenge of solution processed organic thin film electronics is the repeatable and well-defined morphological control of the resulting films after deposition. In this study, we observed how the addition of diiodo-alkanes to poly-3-hexyl-thiophene (P3HT) solutions effect the formation of resulting thin films. These additives have various boiling points that will affect the drying properties of cast thin films. We also sought to observe if any halogen bonding interaction between iodine and sulfur occurs and if this interaction can be used to promote polymer morphological selfassembly. Techniques such as UV/Vis spectroscopy, X-ray diffraction, and Atomic Force Microscopy were used to probe the evolution of the film morphology as the additives were added to the solutions. 1,8-diiodooctane doped films showed the best overall device performance. This could be due to its favorable interaction with the side chain of P3HT as seen in it morphological properties. This study may result in a new technique that can be used to enhance the solid-state morphology of thin films for high performance electronic applications.