Regensburg 2010 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 3: Organic Electronics and Photovoltaics I (Joint Session DS/CPP/HL/O)
DS 3.6: Vortrag
Montag, 22. März 2010, 11:30–11:45, H8
Investigation of contact properties of organic field effect transistors — •M. Grobosch1, I. Hörselmann2, S. Scheinert2, M. Knupfer1, and G. Paasch1 — 1IFW Dresden, D-01069 Dresden, Germany — 2Technical University Ilmenau, D-98684 Ilmenau, Germany
Source/drain contacts in OFETs based on a solution prepared modified P3HT were characterized by combined X-ray and ultra violet photoemission spectroscopy (XPS, UPS) and electrical measurements of the OFET whereas the sample preparation for the different measuring principles has been realized in parallel differing in the layer thickness of the polymer. By means of UPS a reduced work function could be demonstrated for different prepared, sputtered, and as-received Au contacts in agreement with previous publications. Furthermore the chemistry and the electronic structure of the interfaces between Au metal deposited onto thin films of solution prepared modified P3HT on sputtered Au contacts have been studied. From the observed well defined molecular orbitals we have found an interface dipole of +1.5 eV and a hole injection barrier of about 0.6 eV. However, one cannot expect such a high barrier from the measured characteristics of the OFET because the currents are not contact limited. Clarifying the reason for such a discrepancy we have carried out two-dimensional simulations. These results confirm clearly for a barrier of 0.6 eV strongly reduced drain currents would be measured. The difference in the layer thickness can be the reason for the measured difference but further investigations are necessary to explain more in detail this phenomenon.