Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 38: Organic semiconductors

HL 38.6: Talk

Thursday, April 4, 2019, 10:45–11:00, H33

Photoemission Spectroscopy Studies of Charge Transfer Interfaces — •Robert Kuhrt, Martin Hantusch, Martin Knupfer, and Bernd Büchner — IFW Dresden, Helmholtzstraße 20, 01069 Dresden

Charge transfer plays an important role in the field of organic molecular materials. Prominent examples are so-called two dimensional metals and superconductors as well as the doping of organic semiconductors that are used in devices like solar cells, OLEDs and organic transistors. Charge transfer at the interface of two organic semiconductors can lead to electronic properties that differ significantly from those of the individual materials which makes a deeper understanding of this process a matter of scientific interest. In principle, charge transfer is expected at interfaces where the ionization potential of one material is located in the same region as the electron affinity of the other material.

In this contribution we present a photoemission spectroscopy (PES) study of interfaces between the acceptor molecule hexafluorotetracyanonaphthoquinodimethane (F₆TCNNQ) and the donor molecules pentacene and di-benzo-pentacene. The electronic states in the valence band region are probed with ultraviolet photoemission spectroscopy (UPS) and an x-ray source (XPS) is used to measure the core levels. It is revealed that the highest occupied molecular orbitals of the donor molecules are shifted when they are in contact with the F₆TCNNQ-molecules. Also, the identification of additional nitrogen and carbon species indicate the presence of reduced F₆TCNNQ molecules and therefore a full localized charge transfer at the interface.