Regensburg 2022 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Organic Electronics and Photovoltaics 2

CPP 26.4: Vortrag

Mittwoch, 7. September 2022, 12:15–12:30, H38

In Situ and In Operando KPFM Studies on OFET Based on Hexadecafluoro-Copper-Phthalocyanine (F₁₆PcCu) to Access Energy Level Alignment and Electrical Contact Resistance — •Pascal Schweitzer, Clemens Geis, and Derck Schlettwein — Justus-Liebig-Universität Gießen, Institut für Angewandte Physik

Contact resistances are considered a show-stopper for organic field effect transistors (OFET). Perfluorinated copper-phthalocyanine (F₁₆PcCu) is a promising chemically stable n-conductor to build complementary logical circuits with established p-conductors. A reasonably high charge carrier mobility µ_ext ≈ 2×10⁻³ cm²/Vs was estimated from device performance affected, however, by neglected contact resistances. In this work, we used in operando Kelvin probe force microscopy under high vacuum to study the influence of contact resistances at the source and drain electrodes on the OFET performance. Non-contact potentiometry at different applied external voltages revealed relevant voltage drops at the electrode interface and in the adjacent contact region. Based on these voltage drops and measured device currents significant contact resistances were calculated. Correcting for such parasitic voltage drops, contact-free µ_ch was obtained, substantially higher than µ_ext. The growth mode of F₁₆PcCu on application-relevant polycrystalline gold substrates and shifts of the energy levels were studied by in situ KPFM and an injection barrier was confirmed. From these results, we conclude that the model of thermionic emission, often used for contact resistances, is not completely sufficient to describe the present case.