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Lecture Benjamin Bröker


09 February 2009 FWN-Building 5113.0202, Nijenborgh 4, 9747 AG, Groningen
Speaker: Benjamin Bröker
Affiliation: Humboldt-Universität, Department of Physics, Berlin
Title: Charge injection barrier lowering at electrode/organic interfaces employing organic electron acceptor and donor materials
Date: Mon Feb 9, 2009
Start: 14.00
Location: FWN-Building 5113.0202
Host: Petra Rudolf
Telephone: +31 50 363 4736


In the past decade considerable research and developement efforts have been focused on the field of organic electronics resulting in the arrival of first products on the commercial market. Basically the field can be divided into three main areas: (i) organic light emitting diodes, (ii) organic photovoltaic cells, and (iii) organic field effect transistors, with all having in common the contacts between electrodes and electroactive organic materials. The electronic properties of these interfaces are important for the performance of the devices as they control charge injection and transport. One method of optimizing the electronic structure at the anode/organic interface is pre-covering the electrode with a (sub-)monolayer of molecular acceptors, thereby reducing the hole injection barrier [1]. Similarly it was shown for the cathode side that the exposure of indium-tin-oxide electrodes to the vapor of tetrakis(dimethylamino)ethylene can yield electron injection barriers similar to those achieved with Al [2]. Here we present an ultraviolet photoelectron spectroscopy (UPS) study of electron accepting and donating molecules on metal single crystal surfaces that readily undergo charge transfer type reactions with the substrate materials. It is shown that the hole and electron injection barriers between these electrodes and prototypical electron and hole transport materials can be decreased by the insertion of thin layers of acceptor/donor molecules. This gives new opportunities not only for improvement of the device performance, but also for the substitution of rare and expensive electrode materials.

 This work is financially supported by European Community project "IControl"

 [1] N. Koch, ChemPhysChem 8, 1438 (2007).

 [2] W. Osikowicz, X. Crispin, C. Tenstedt, L. Lindell, T. Kugler and W. R. Salaneck,

 Appl. Phys. Lett. 85, 1616 (2004).




Last modified:22 October 2012 2.30 p.m.