Dresden 2006 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 19: SYMPOSIUM Functional Organic Thin Films I

CPP 19.4: Talk

Thursday, March 30, 2006, 10:30–10:45, ZEU Lich

Self consistent theory of charge carrier injection at the metal-organic interface — •Frederik Neumann, Yuri Genenko, Christian Melzer, and Heinz von Seggern — Institute of Materials Science, Darmstadt University of Technology, Petersenstraße 23, D-64287 Darmstadt, Germany

The effect of the injection barrier on charge transport plays an important role in understanding and development of organic electronic devices. In previous studies this effect was considered in the special cases of low and high injection barriers.

The focus of the present study is on the development of an injection model which incorporates space charge effects. The challenge of this task is the problem of self-consistency. The amount of injected charge carriers injected per unit time strongly depends on the barrier height, while at the same time the electrostatic potential generated by the injected charge modifies the height of the injection barrier itself.

Here a self-consistent model of the injection process on metal/organic interfaces is presented. This model requires a proper description of both, the organic and the metal side of the interface.

To describe the metal a DOS of quasi-free electrons is chosen. The description for the organic semiconductor is based on a gaussian DOS. Since charge transport in organic semiconductors occurs by hopping of charge carriers between localized states, we introduced the concept of a mobility edge and a field dependent mobility. The resulting differential equations are solved in a self-consistent manner by introducing continuity of the electrochemical potential and electric displacement.