Dresden 2009 – wissenschaftliches Programm

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SYOP: Symposium Organic Photovoltaics: From Single Molecules to Devices

SYOP 4: Organic Photovoltaics: from Single Molecules to Devices

SYOP 4.18: Poster

Donnerstag, 26. März 2009, 16:30–19:00, P1A

Investigation of the effects of doping concentration in a p-doped organic semiconductor — •Selina Olthof, Björn Lüssem, and Karl Leo — Institut für Angewandte Photophysik, TU Dresden, George-Bähr-Straße 1, 01069 Dresden

Thin films of organic materials are widely investigated for the use in electronic and optoelectronic devices for instance solar cells and light emitting diodes. Like in the field of inorganic semiconductors, the technique of doping can greatly increase the performance of such devices.

However, so far little is understood of the underlying mechanisms of doping organic layers with molecules and whether they are comparable to the doping in inorganic semiconductors. Using UV- photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS), we study the properties of a p-doped organic thin film using as a model system MeO-TPD doped by the strong electron acceptor F4-TCNQ.

We investigate how the doped layer aligns with different contact materials by performing interface resolved measurements. By varying the doping concentration, changes in the position of the Fermi energy in the band gap and the influence of the free carrier concentration on the width of the depletion layer can be studied.

As expected from inorganic semiconductors, we find that for higher doping ratio the Fermi level moves closer to the HOMO and furthermore this distance is independent on the contact material used.