Dresden 2009 – wissenschaftliches Programm

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SYOP: Symposium Organic Photovoltaics: From Single Molecules to Devices

SYOP 4: Organic Photovoltaics: from Single Molecules to Devices

SYOP 4.65: Poster

Donnerstag, 26. März 2009, 16:30–19:00, P1A

Investigations of film thickness dependence in polythiophene organic field effect measurements on device performance and charge carrier mobility using a gated four probe technique — •Ali Tunc, Fabian Johnen, Elizabeth von Hauff, and Jürgen Parisi — University of Oldenburg, Department of Physics, Energy and Semiconductor Research Laboratory, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany

In this study polythiophene (P3HT) based organic field effect transistors (OFET) with different semiconductor film thickness were investigated using a gated four probe geometry. A series of P3HT OFETs with different P3HT film thicknesses (from 39 to 240nm) were fabricated by varying P3HT concentration in chloroform and varying the spin coating parameters for depositing the semiconducting layer. The OFETs were bottom contact devices with Au contacts with a thin layer of Cr for adhesion to the SiO2. The source and drain contacts as well as two thin additional electrodes protruding roughly 1/4 of the way into the channel were patterned with photolithography. The four point geometry allowed for the investigation of the effects of contact resistances on the field effect measurements. The source-drain current and the field effect mobility determined in the saturation region of the OFET current-voltage characteristics were found to increase with P3HT film thickness. The field effect mobility determined from the linear region of the IV characteristics showed less dependence on the film thickness and seemed to be influenced by inhomogeneities in the semiconducting channel at low currents.