Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 41: Organic semiconductors

HL 41.6: Talk

Thursday, February 28, 2008, 16:30–16:45, ER 270

Electron and hole transport in evaporated layers of copper-phthalocyanine — •Michael Kraus, Andreas Opitz, and Wolfgang Brütting — Institute of Physics, University of Augsburg, Germany

The realisation of electron and hole transport in the same material will extend the probabilities of organic electronic circuits. An example is the field of complimentary logics where separated p- and n- type field-effect transistors are necessary. In this study copper(II)-phthalocyanine (CuPc) is investigated which is commonly used in organic field-effect transistors (OFETs) due to its stability in ambient air or in organic photovoltaic cells as a light absorber.

We fabricated bottom-gate top-contact OFETs with evaporated CuPc layers as active layer. The Si/SiO₂ substrates were treated with a thin layer of PMMA to achieve a trap free interface. It is possible to control the type of carrier transport by using various electrode materials differing in their work function. So both types of unipolar transport and also ambipolar transport are realised. The transfer-length-method is applied to calculate mobility and contact resistance separately. The field-effect mobility was found as an intrinsic property of the material which depends on the carrier type but not on the electrode material. Our results show an asymmetry between electron and hole transport since the hole mobility is one order of magnitude higher than the electron mobility.