Hamburg 2001 – wissenschaftliches Programm
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SYOF: Organische Festkörper
SYOF 5: Poster Session
SYOF 5.12: Poster
Dienstag, 27. März 2001, 17:00–19:00, Aula S3
Controlled alkali metal doping of the organic molecular semiconductor perylenetetracarboxylicdianhydride (PTCDA) — •Thomas Ertl1 and Christiane Ziegler2 — 1Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen — 2Department of Physics, University of Kaiserslautern, 67663 Kaiserslautern
Organic semiconductors are interesting materials for the application in electronic devices. In the case of Organic Light Emitting Diodes (OLEDs) Kido et al. [1] showed that the device efficiency can be improved by alkali metal doping of the electron injection layer. Furthermore n-doping is interesting for organic FET devices. To achieve best device performances a precise control of the doping-level is necessary.
Here we report on the controlled doping of PTCDA with the alkali metals Na and Cs. The doping-mechanism is studied by XPS and UPS. Our results show a charge-transfer doping in the course of which the alkali metal transfers its valence electron onto the organic molecule. The evolution of the electronic structure can be explained in terms of polaron formation and is independent of the counterion. For both dopants there exists a saturation doping level of approximately 1 metal atom / PTCDA. At least in the case of Na this n-doping is completely reversible. Theoretical calculations on the alkali/PTCDA-system are compared to these experimental results. Finally conductivity measurements show that the conductivity at room temperature can be increased up to 6 orders of magnitude upon alkali metal doping.
[1] J. Kido, T. Matsumoto, Appl. Phys. Lett., 73, (1998), 2866.