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Optical and Electrical Measurements Reveal the Orientation Mechanism of Homoleptic Iridium-Carbene Complexes

Schmid, M.; Harms, K.; Degitz, Carl; Morgenstern, T.; Hofmann, A.; Friederich, Pascal; Johannes, H.-H.; Wenzel, Wolfgang; Kowalsky, W.; Brutting, W.

Understanding and controlling the driving forces for molecular alignment in optoelectronic thin-film devices is of crucial importance for improving their performance. In this context, the preferential orientation of organometallic iridium complexes is in the focus of research to benefit from their improved light-outcoupling efficiencies in organic light-emitting diodes (OLEDs). Although there has been great progress concerning the orientation behavior for heteroleptic Ir complexes, the mechanism behind the alignment of homoleptic complexes is still unclear yet. In this work, we present a sky-blue phosphorescent dye that shows variable alignment depending on systematic modifications of the ligands bound to the central iridium atom. From an optical study of the transition dipole moment orientation and the electrically accessible alignment of the permanent dipole moment, we conclude that the film morphology is related to both the aspect ratio of the dye and the local electrostatic interaction of the ligands with the film surface during growth. These results indicate a potential strategy to actively control the orientation of iridium-based emitters for the application in OLEDs.

Verlagsausgabe §
DOI: 10.5445/IR/1000127676
Veröffentlicht am 04.03.2021
DOI: 10.1021/acsami.0c14613
Zitationen: 3
Zitationen: 4
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Nanotechnologie (INT)
Institut für Theoretische Informatik (ITI)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 1944-8244, 1944-8252
KITopen-ID: 1000127676
HGF-Programm 43.21.04 (POF III, LK 01) Molecular Engineering
Erschienen in ACS applied materials & interfaces
Verlag American Chemical Society (ACS)
Band 12
Heft 46
Seiten 51709-51718
Schlagwörter organic light-emitting diode emitter orientation; orientation polarization; Ir complexes; meridional and facial isomers
Nachgewiesen in Scopus
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