Influence of the supramolecular arrangement in the electrical conductivity of poly(thiophene) thin films

Thin films of regioregular polythiophene derivatives have had their optical, structural and morphological properties characterized, but there is still a lack of comparative studies to determine the effect from deposition techniques, especially on the electrical properties. In this study, we produced Langmuir-Schaefer and spin-coated films of regioregular alkyl-substituted polythiophene derivatives (P3AT) to investigate how distinct supramolecular arrangements can affect their properties. The Langmuir-Schaefer films deposited on indium-tin oxide substrates were observed to grow linearly with the number of layers, according to UV-visible absorption spectroscopy. Atomic force microscopy and Brewster angle microscopy were carried out for morphological characterization. From electrical transport measurements, the DC electrical conductivity of Langmuir-Schaefer films of P3AT was higher than the corresponding spin-coated films, which can be related to the dissimilar roughness and molecular-level organization provided by the Langmuir-Schaefer technique.