Berlin 2005 – scientific programme

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SYOO: Organic Optoelectronics and Photonics

SYOO 1: Organic Field-Effect Transistors

SYOO 1.5: Talk

Monday, March 7, 2005, 10:45–11:00, TU C130

Comparison between the charge carrier mobilities in OFET structures obtained from electrical characterization, four-point measurements and potentiometry — •R. Scholz, L. Mancera, F. Müller, A.-D. Müller, M. Hietschold, B.A. Paez, I. Thurzo, and D.R.T. Zahn — Institut für Physik, Technische Universität Chemnitz, Chemnitz, Germany

In a combination of experimental techniques including charge transient spectroscopy (CTS), optical spectroscopies (IR, visible/UV, Raman), and electrical probes, we develop concepts how to quantify the density of states of deep traps and their influence on the performance of OFET devices. With the so-defined densities of traps and the corresponding distribution over trapping and de-trapping rates, we deduce microscopic models for the influence of traps on the charge carrier mobility in the channel. Four-point measurements and potentiometry are used to investigate the contact resistances, so that the injection of the charges at the source contact and their extraction at the drain contact can be distinguished from the influence of trap states on the charge transport through the accumulation channel. For OFET structures based on pentacene thin films with Au bottom contacts, the mobility in the channel region as obtained from potentiometry and four-point measurements is about one order of magnitude higher than the average mobility fitted to the output characteristics.