Abstract
Conductive polymers have fundamental relevance as well as novel technological applications in the organic optoelectronics field. Their photophysical and transport properties strongly depend on the molecular arrangement, and nanoscale characterization is needed to fully understand the optoelectronic processes taking place in organic devices. In this work, we study the electrostatic properties of poly-3-octylthiophene isolated structures: disordered low-packed polymer chains and crystalline layered lamellar assemblies. We characterize the electronic ground state using Kelvin probe microscopy. This allows us to resolve a rich variety of surface potential regions that emerge over the different polymer structures. These SP regions are correlated with different molecular aggregates.
Highlights
Semiconducting conjugated polymers (SCPs) are widely used in electronic devices such as solar cells, organic field effect transistors and light-emitting devices [1,2,3]
Taking into account the dimensions of the P3OT polymer chains, these thin structures should correspond to polymer chains oriented with the tiophene rings facing the highly oriented pyrolytic graphite (HOPG) substrate and the alkyl side chains parallel to it—that is, to molecules adsorbing “flat” onto the substrate
In the KPFM image (Figure 3c), this thin random structure shows no contrast with respect to the HOPG
Summary
Semiconducting conjugated polymers (SCPs) are widely used in electronic devices such as solar cells, organic field effect transistors and light-emitting devices [1,2,3]. Among the SCPs, the poly-3-alkylthiophenes (P3ATs) and, in particular, poly-3-hexylthiophene (P3HT) have attracted particular attention due to their good solubility in organic solvents and strong tendency to self-assemble in π-stacked quasi-crystalline lamellae [14]. This confers upon them interesting photophysical and charge transport properties, with many potential applications in optoelectronic devices [14,15]. It is known that efficient charge transport occurs in the c-b plane, along either the backbone direction (c-axis) or the π − π stacking direction (b-axis), whereas alkyl side chains act as charge barriers along the a-axis [20,21]
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