Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 16: Poster I

DS 16.4: Poster

Tuesday, March 24, 2009, 09:30–12:30, P5

Ambipolar charge carrier transport in evaporated layers of copper-phthalocyanine: Field-effect transistors and metal-insulator-semiconductor diodes — •Michael Kraus, Julia Wagner, Andreas Opitz, and Wolfgang Brütting — Institute of Physics, University of Augsburg, Germany

Copper-phthalocyanine (CuPc) is a common semiconductor used in organic electronics, e.g. as hole-transport layer in organic field-effect transistors or as light absorber in organic photovoltaic cells. As shown recently, CuPc can exhibit bipolar charge carrier transport [1].

We fabricated top-contact field-effect transistors (FETs) and metal-insulator-semiconductor (MIS) diodes with thermally evaporated CuPc on passivated Si/SiO₂ substrates. The field-effect mobility parallel to the semiconductor–substrate interface is determined with the help of I−V−characteristics (for FETs) and the bulk mobility perpendicular to the surface with impedance spectroscopy (for MIS diodes). By variation of the electrode material, we achieved unipolar hole, unipolar electron and ambipolar charge carrier transport in the FETs. In the case of the MIS structures, diodes showing accumulation of holes, electrons or both charge carrier types are realized. We investigated the charge carrier mobilities and their thermal activation processes in both devices. The difference between electron and hole mobility is less than one order of magnitude but the mobilities do not depend on the electrode material and can thus be considered to be intrinsic properties of CuPc.

[1] A. Opitz et al., New J. Phys. 10 (2008) 065006