10:10 - 10:50 a.m.
"Molecular Doping – A Key Technology for Highly Efficient Organic Devices"
The efficiency of organic optoelectronic devices has been increasing steeply during the last years. White organic light emitting diodes (OLEDs) with fluorescent tube efficiency and organic solar-cells with efficiencies beyond 10% were reported, which triggered substantial commercial interest in the technology.
Organic doping became a key technology in the optimization of these organic devices. However, despite its success in the past, the details of the doping process are still a matter of intensive scientific debate. In particular, a closed model that can quantitatively describe the doping process is highly needed in order to advance the field further.
In this contribution, I will discuss our recent advances in the understanding of molecular doping. A simple but powerful model will be presented that can describe the shift of the Fermi-Level with doping concentration precisely. The model predicts that doping is limited by trap states in the organic host materials. The presence of these traps and concentration is verified by impedance spectroscopy and thermally stimulated currents, which gives further confidence in the model.
Driven by the improved understanding of the doping process, we were able show that doping allows for the design of novel organic transistors. In particular, the first realization of organic inversion transistors is described. Potential applications of this technology for flexible electronics are discussed.
Björn Lüssem studied electrical engineering at the RWTH Aachen (Germany) and the University of Bath and obtained his degree as Diplom-Ingenieur in 2003.He prepared his PhD thesis at the Research Center in Jülich, Germany in the field of molecular electronics. His thesis concentrates on Scanning-Tunnelling Microscopy of pure and mixed self-assembled monolayers and has been awarded the VDE-Promotionspreis and the Günther-Leibfried-Preis. After staying at the Materials Science Laboratory of Sony in Stuttgart from 2006-2008, he joined Prof. Leo's group at the TU Dresden, where he headed the OLED and the New Devices group. In 2014 he started as Assistant Professor at the Physics Department of Kent State University.