Regensburg 2007 – wissenschaftliches Programm

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 8: Poster Session SYOE

SYOE 8.22: Poster

Dienstag, 27. März 2007, 18:00–20:00, Poster B

Contact resistances in organic field effect transistors — •Nicolas Spethmann, Elizabeth von Hauff, and Jürgen Parisi — Department of Physics, Energy and Semiconductor Research Laboratory, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany

In this study organic Field-Effect-Transistors (oFETs) are used to investigate the transport properties of charge carriers in organic semiconductors. From the current-voltage characteristics material parameters such as the mobility µ_FET can be extracted. The extracted parameters have to be corrected for contact resistances, as these can dominate the overall behavior of an oFET. It is also important to get an improved understanding of the physical mechanisms at a metal/organic semiconductor contact for applications such as organic photovoltaics. In this study we use two different approaches to isolate the contact resistance of an oFET from the channel resistance. Firstly, the channel length of the oFET was varied for different devices; while the contact resistance remains constant, the channel resistance scales according to the channel length. Thus it is possible to extract the contact resistance. However, the deviations from device to device can complicate this analysis. Furthermore one cannot differentiate between the contact resistance at source and drain. These disadvantages can be overcome by the second approach: A gated four-probe structure was used to directly measure the voltage drop at the source and the drain in an operating transistor. The organic semiconductors used were poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM).