Spin‐ and Voltage‐Dependent Emission from Intra‐ and Intermolecular TADF OLEDs

Please always quote using this URN: urn:nbn:de:bvb:20-opus-224434
  • Organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) utilize molecular systems with a small energy splitting between singlet and triplet states. This can either be realized in intramolecular charge transfer states of molecules with near‐orthogonal donor and acceptor moieties or in intermolecular exciplex states formed between a suitable combination of individual donor and acceptor materials. Here, 4,4′‐(9H,9′H‐[3,3′‐bicarbazole]‐9,9′‐diyl)bis(3‐(trifluoromethyl) benzonitrile) (pCNBCzoCF\(_{3}\)) isOrganic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) utilize molecular systems with a small energy splitting between singlet and triplet states. This can either be realized in intramolecular charge transfer states of molecules with near‐orthogonal donor and acceptor moieties or in intermolecular exciplex states formed between a suitable combination of individual donor and acceptor materials. Here, 4,4′‐(9H,9′H‐[3,3′‐bicarbazole]‐9,9′‐diyl)bis(3‐(trifluoromethyl) benzonitrile) (pCNBCzoCF\(_{3}\)) is investigated, which shows intramolecular TADF but can also form exciplex states in combination with 4,4′,4′′‐tris[phenyl(m‐tolyl)amino]triphenylamine (m‐MTDATA). Orange emitting exciplex‐based OLEDs additionally generate a sky‐blue emission from the intramolecular emitter with an intensity that can be voltage‐controlled. Electroluminescence detected magnetic resonance (ELDMR) is applied to study the thermally activated spin‐dependent triplet to singlet up‐conversion in operating devices. Thereby, intermediate excited states involved in OLED operation can be investigated and the corresponding activation energy for both, intra‐ and intermolecular based TADF can be derived. Furthermore, a lower estimate is given for the extent of the triplet wavefunction to be ≥ 1.2 nm. Photoluminescence detected magnetic resonance (PLDMR) reveals the population of molecular triplets in optically excited thin films. Overall, the findings allow to draw a comprehensive picture of the spin‐dependent emission from intra‐ and intermolecular TADF OLEDs.show moreshow less

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Author: Nikolai Bunzmann, Benjamin Krugmann, Sebastian Weissenseel, Liudmila Kudriashova, Khrystyna Ivaniuk, Pavlo Stakhira, Vladyslav Cherpak, Marian Chapran, Gintare Grybauskaite‐Kaminskiene, Juozas Vidas Grazulevicius, Vladimir Dyakonov, Andreas Sperlich
URN:urn:nbn:de:bvb:20-opus-224434
Document Type:Journal article
Faculties:Fakultät für Physik und Astronomie / Physikalisches Institut
Language:English
Parent Title (English):Advanced Electronic Materials
Year of Completion:2021
Volume:7
Issue:3
Article Number:2000702
Source:Advanced Electronic Materials 2021, 7(3):2000702. DOI: 10.1002/aelm.202000702
DOI:https://doi.org/10.1002/aelm.202000702
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Tag:color tuning; exciplexes; organic light emitting diodes; spin; triplets
Release Date:2021/11/17
Licence (German):License LogoCC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International