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HL: Fachverband Halbleiterphysik

HL 28: Focus: Exploitation of Anisotropy in Organic Semiconductors I (joint session CPP/HL)

HL 28.2: Vortrag

Dienstag, 17. März 2020, 10:30–10:45, ZEU 222

Clarifying the orientation mechanism of homoleptic Iridium-carbene complexes — •Markus Schmid¹, Kristoffer Harms², Thomas Morgenstern¹, Alexander Hofmann¹, Hans-Hermann Johannes², Wolfgang Kowalsky², and Wolfgang Brütting¹ — ¹Institute of Physics, University of Augsburg, 86135 Augsburg, Germany — ²Institute for high frequency technology, TU Braunschweig, 38106 Braunschweig, Germany

Horizontal orientation of the emitting species is one of the most promising techniques to increase the efficiency of state of the art organic light emitting diodes. Especially metal-organic compounds have attracted great attention. While the alignment has been observed and explained for many heteroleptic Iridium complexes, there has been less progress for their homoleptic counterparts. Only few homoleptic compounds have been reported to show a beneficial morphology in guest-host systems. In this study, we investigated multiple derivatives and isomers of the sky-blue dye tris(N-dibenzofuranyl-N’-methylimidazole)iridium(III) (Ir(dbfmi)₃) doped in the hosts Bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO) and 3,6-bis(diphenylphosphoryl)-9-phenylcarbazole (PO9). By a combination of optical techniques to probe the transition dipole orientation and electrical measurements to access the permanent dipole moment, we revealed that this homoleptic complex is significantly aligned in both matrices. From our insights into the film morphology we postulate that an anisotropic interaction is responsible for the orientation and even identified the region of the molecule that causes this behavior.