Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 38: [DS] Organic electronics and photovoltaics: electronic properties I (jointly with CPP, HL, O)

O 38.6: Talk

Wednesday, March 28, 2012, 10:45–11:00, H 2032

Agglomeration of MoO₃ doped into organic thin films studied by TEM-spectroscopy and Tomography — •Daniela Donhauser^{1, 2}, Katrin Schultheiss^{1, 2}, Levin Dieterle^{1, 2}, Martin Pfannmöller³, Rasmus R. Schröder³, Tobias Glaser^4,2, Bernd Lunkenheimer^5,2, Michael Kröger^{1, 2}, and Wolfgang Kowalsky^{1, 2} — ¹Institut für Hochfrequenztechnik, Technische Universität Braunschweig — ²InnovationLab GmbH, Heidelberg — ³CellNetworks, Universität Heidelberg — ⁴Kirchhoff-Institut für Physik, Universität Heidelberg — ⁵Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz

Electrochemical doping is essential to overcome limitations in organic devices imposed by low intrinsic conductivity and high injection barriers at the contacts. Materials with very deep lying HOMO-levels like CBP (4,4’-Bis(N-carbazolyl)-1,1’-biphenyl) can be doped with transition metal oxides, e.g. MoO₃. In such systems a very low doping efficiency has been found for which the physical origin is not understood. With TEM spectroscopy we could show that agglomeration of MoO₃ in the CBP-matrix is most likely the reason for the low doping efficiency. Using TEM tomography we observed that MoO₃ forms filament-like structures perpendicular to the substrate. Combining our results with FTIR-measurements, which indicate a charge carrier localization at single molecules, we can model the charge transport to occur at the interface of the MoO₃ filaments and the organic matrix.