Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: Organic semiconductors

HL 50.7: Talk

Wednesday, March 13, 2013, 11:15–11:30, H13

Model-free mobility determination in thin films of organic semiconductors: potential mapping — •Johannes Widmer, Janine Fischer, Karl Leo, and Moritz Riede — Institut für Angewandte Photophysik, TU Dresden, Germany

Mobility is the key parameter for charge transport characterization. In disordered systems, it is generally not a constant, but a function of the electric field and/or the charge carrier density.

In our work, we characterize the charge transport in thin films of organic semiconductors perpendicular to the surface, i.e. in the direction relevant for common device applications. The effective mobility is determined as a function of the electric field and charge carrier density µ(E, n). This is achieved by a potential mapping approach, analyzing a series of current-voltage characteristics of single carrier devices with varying intrinsic layer thicknesses. The evaluation is validated with simulation data, demonstrating that field dependence and charge density dependence can be resolved separately.

The technique is applied to well-established and state-of-the-art material systems. For example, in a blend of zinc phthalocyanine (ZnPc) and Fullerene C60, a field activated hole mobility of 7.9 · 10⁻⁹ cm²/Vs · exp( 0.01 √E · cm/V ) is measured.

With this method, the charge carrier mobility can be studied systematically, and the field and charge density dependence upon variations of the chemical composition or the processing conditions can be quantified.