Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 73: [DS] Organic Electronics and Photovoltaics III (jointly with CPP, HL, and O)
O 73.7: Talk
Thursday, March 17, 2011, 15:30–15:45, GER 38
Contact properties of organic PCBM field effect transistors analyzed by combined photoemission spectroscopy and electrical measurements — •M. Grobosch1, I. Hörselmann2, J. Bartsch2, 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 PCBM were characterized by combined X-ray and ultra violet photoemission spectroscopy (XPS, UPS) and electrical measurements of the OFET. Thereby the sample preparation for the different measuring principles has been realized in parallel, differing only in the layer thickness of the polymer. By means of UPS a reduced work function could be demonstrated for differently prepared, sputtered, and as-received Au and Al contacts in agreement with previous publications [1]. On top of the Al contacts a natural AlOx layer could be identified. For both the PCBM/Au and PCBM/Al systems from UPS a hole injection barrier of 1.8 eV has been determined. Considering the gap of 2.0 eV [2] the electron injection barrier would be the same of 0.2 eV. In contrast to these identical barriers as following from UPS, the OFET currents with Au and Al contacts differ by more than two orders of magnitude. A possible origin of this striking discrepancacy will be presented. [1] M. Grobosch et al., Adv. Mater. 19 (2007) 754. [2] Z.-L. Guan et al., Organic Electronics 11 (2010) 1779.