Prof. Norbert Koch

Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany
Norbert Koch studied technical physics at the Technische Universität Graz, Austria. At the same university he received a doctorate in solid state physics in 2000. He spent the following two years as postdoc at Princeton University and worked on organic/metal interfaces and covalently surface-bound self-assembled monolayers. After moving to Berlin in 2003, he started building his own group at Humboldt-Universität zu Berlin. In 2009 he was appointed as professor in the Department of Physics of Humboldt-Universität, and in 2010 his group at Helmholtz-Zentrum Berlin für Materialien und Energie was established.

Talk title: Energy level alignment and fundamental processes at interfaces between monolayer transition metal dichalcogenides and organic semiconductors
The combination of two different semiconductors enables enhanced functionality of electronic and optoelectronic devices. This correspondingly holds for 2-dimensional transition metal dichalcogenide (TMDC) monolayers (MLs) and their amalgamation with organic semiconductors (OS), which are also excitonic materials that feature strong light-matter coupling. Depending on the electronic energy level alignment at ML-TMDC/OS interfaces, useful phenomena can arise, such as energy transfer and ground or excited state charge transfer, as well as hybrid excitations. For knowledge-based ML-TMDC/OS structure formation, the energy level alignment at the interfaces must be unraveled. That is a challenging task, because of the many degrees of freedom of such systems and their dependence on many environmental parameters. Employing photoemission spectroscopy, the primary method to study electronic properties, for ML-TMDC/OS structures is, however, non-trivial. Here, it will be shown how photoemission spectroscopy can be used to determined the energy level alignment at interfaces between ML-MoS₂ or ML-WS₂ and a range of different OSs. In turn, this then allows identifying key processes at these interfaces, including resonance energy transfer, excited state charge transfer, as well as doping.