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The electrical conductivity and morphological characteristics of two conjugated polymers, P3HT and PCPDTBT, p-doped with the strong electron acceptor tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) are studied as a function of dopant concentration. By combining scanning and transmission electron microscopy, SEM and TEM, with electrical characterization, we observe a correlation between the saturation in electrical conductivity and the formation of dopant rich clusters. We demonstrate that SEM is a useful technique to observe imaging contrast for locating doped regions in thin polymer films, while in parallel monitoring the surface morphology. The results are relevant for the understanding of structure property relationships in doped conjugated polymers. [ABSTRACT FROM AUTHOR]

Abstract: Substantial potential steps ∼0.5eV are frequently observed in organic multilayers of donor and acceptor molecules. Often such potential steps depend on the order in which the individual layers are deposited, or on which substrate they are deposited. In this paper we outline a model for these potential steps, based upon integer charge transfer between donors and acceptors, charge equilibration across the multilayer, and simple electrostatics. Each donor, acceptor, or substrate material is characterized by a pinning level, and the potential profile can be deduced from the sequential order of the layers, and the differences between their pinning levels. For particular orderings we predict that intrinsic potential differences lead to electric fields across individual layers, which may falsely be interpreted as band bending. [Copyright &y& Elsevier]