Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 9: Poster 1
HL 9.90: Poster
Montag, 23. März 2009, 14:30–17:00, P2
Modification of the injection properties in small molecule thin film transistors — •Florian Wörner1, Peter Nill2, and Jens Pflaum1,3 — 1Experimental Physics VI, Julius-Maximilians University Würzburg, 97074 Würzburg — 2Inst.for Appl. Physics, University Tübingen, 72076 Tübingen — 3Bavarian Center for Applied Energy Research e.V. (ZAE Bayern)
Over the past, the electronic characteristics of thin film transistors based on small molecules have continuously improved making their implementation in all-organic devices close to the market. Still, one of the bottlenecks is the injection of charge carriers into the conduction channel, hampered by charge transfer and the formation of dipoles at the metal-organic interface. In our contribution we discuss a possible strategy to overcome this limitation by use of metal contacts coated with monolayers of small molecules, namely oxides of the organic semiconductor pentacene. We demonstrate that this functionalization leads to a significant improvement of the transistor performance in terms of the contact resistance and the threshold voltage. Temperature dependent transport studies enable us to analyze the underlying microscopic mechanisms determining the injection behavior and to discriminate between a tunneling and a thermally assisted injection process. Finally, we discuss the applicability of our approach to molecular materials preferentially showing an n-type semiconducting behavior.