Interchain interactions have a profound effect on the optical as well as charge transport properties of conjugated polymer thin films. In contrast to oligomeric model systems in solution-deposited polymer thin films the study of such effects is complicated by the complex microstructure. We present here a detailed study of interchain interaction effects on both charged polarons as well as neutral excitons in highly crystalline, high-mobility poly-3-hexylthiophene (P3HT) as a function of molecular weight. We find experimental evidence for reduced exciton bandwidth and increased polaron delocalization with increasing conjugation length and crystalline quality. From comparative studies of field-effect transistor characteristics, film morphology, and optical properties our study provides a microscopic understanding of the factors which limit the charge transport in P3HT to field-effect mobilities around 0.1 cm(2)/V s, and which will need to be addressed to improve mobility further.
Chang, J. F., Clark, J., Zhao, N., Sirringhaus, H., Breiby, D. W., Andreasen, J. W., Nielsen, M. M., Giles, M., Heeney, M., & McCulloch, I. (2006). Molecular-weight dependence of interchain polaron delocalization and exciton bandwidth in high-mobility conjugated polymers. Physical Review B Condensed Matter, 74(11), 115318. https://doi.org/10.1103/PhysRevB.74.115318