What controls the orientation of TADF emitters?

  • Thermally-activated delayed fluorescence (TADF) emitters—just like phosphorescent ones—can in principle allow for 100% internal quantum efficiency of organic light-emitting diodes (OLEDs), because the initially formed electron-hole pairs in the non-emissive triplet state can be efficiently converted into emissive singlets by reverse intersystem crossing. However, as compared to phosphorescent emitter complexes with their bulky—often close to spherical—molecular structures, TADF emitters offer the advantage to align them such that their optical transition dipole moments (TDMs) lie preferentially in the film plane. In this report, we address the question which factors control the orientation of TADF emitters. Specifically, we discuss how guest-host interactions may be used to influence this parameter and propose an interplay of different factors being responsible. We infer that emitter orientation is mainly governed by the molecular shape of the TADF molecule itself and by the physicalThermally-activated delayed fluorescence (TADF) emitters—just like phosphorescent ones—can in principle allow for 100% internal quantum efficiency of organic light-emitting diodes (OLEDs), because the initially formed electron-hole pairs in the non-emissive triplet state can be efficiently converted into emissive singlets by reverse intersystem crossing. However, as compared to phosphorescent emitter complexes with their bulky—often close to spherical—molecular structures, TADF emitters offer the advantage to align them such that their optical transition dipole moments (TDMs) lie preferentially in the film plane. In this report, we address the question which factors control the orientation of TADF emitters. Specifically, we discuss how guest-host interactions may be used to influence this parameter and propose an interplay of different factors being responsible. We infer that emitter orientation is mainly governed by the molecular shape of the TADF molecule itself and by the physical properties of the host—foremost, its glass transition temperature Tg and its tendency for alignment being expressed, e.g., as birefringence or the formation of a giant surface potential of the host. Electrostatic dipole-dipole interactions between host and emitter are not found to play an important role.show moreshow less

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Metadaten
Author:Bilal A. Naqvi, Markus Schmid, Ettore Crovini, Prakhar Sahay, Tassilo Naujoks, Francesco Rodella, Zhen Zhang, Peter Strohriegl, Stefan Bräse, Eli Zysman-Colman, Wolfgang BrüttingORCiDGND
URN:urn:nbn:de:bvb:384-opus4-794713
Frontdoor URLhttps://opus.bibliothek.uni-augsburg.de/opus4/79471
ISSN:2296-2646OPAC
Parent Title (English):Frontiers in Chemistry
Publisher:Frontiers Media S.A.
Type:Article
Language:English
Date of first Publication:2020/09/04
Publishing Institution:Universität Augsburg
Release Date:2020/09/07
Tag:OLEDs; TADF; emitter orientation; molecular orientation; emitter-host interaction
Volume:8
First Page:750
DOI:https://doi.org/10.3389/fchem.2020.00750
Institutes:Mathematisch-Naturwissenschaftlich-Technische Fakultät
Mathematisch-Naturwissenschaftlich-Technische Fakultät / Institut für Physik
Mathematisch-Naturwissenschaftlich-Technische Fakultät / Institut für Physik / Lehrstuhl für Experimentalphysik IV
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Licence (German):CC-BY 4.0: Creative Commons: Namensnennung (mit Print on Demand)