Regensburg 2010 – scientific programme
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DS: Fachverband Dünne Schichten
DS 15: [HL] Organic Semiconductors: Transistors and OLEDs (Joint Session DS/CPP/HL/O)
DS 15.5: Talk
Tuesday, March 23, 2010, 10:30–10:45, H15
Correlation between the effective contact resistance and the charge carrier transport in organic semiconductors of different mobility — R. Winter1, F. Wörner1, M.S. Hammer1, C. Deibel1, and •J. Pflaum1,2 — 1Experimental Physics VI, Julius-Maximilians-University, 97074 Würzburg — 2Bavarian Center For Applied Energy Research, 97074 Würzburg
In this presentation we address questions on the impact of the charge carrier mobility on the injection behavior in organic thin film transistors (OTFTs). Though many theoretical models treat the contact resistance, R, and the mobility, µ, independently, we demonstrate a significant correlation between these two quantities for P3HT and pentacene. Corresponding TFT measurements have been performed between 40 - 300K. To modify the effective contact resistance, monolayers of different oligoacenes were deposited between the Au bottom contacts and the active organic transport layer. Despite significant differences in the room temperature mobilities, 10−4cm2/Vs for P3HT and 10−2cm2/Vs for pentacene, the temperature dependent variations of the mobility as well as of the effective contact resistance prove to be similar. For both materials a change in the slope of the R(T) and µ(T)-slope can be detected. However, the cross-over temperature for pentacene amounts to 80K whereas that for P3HT is shifted to 185K. We will discuss this observation in the context of a balanced transport, i.e. that the injection at the metal contact interfaces is strongly related to the charge carrier transport in the semiconducting layer.
Financial support by BMBF (project GREKOS) is acknowledged.