Spin- and voltage-dependent emission from intra- and intermolecular TADF OLEDs /

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

doi:10.1002/aelm.202000702

Title	Spin- and voltage-dependent emission from intra- and intermolecular TADF OLEDs /
Authors	Bunzmann, Nikolai ; Krugmann, Benjamin ; Weissenseel, Sebastian ; Kudriashova, Liudmila ; Ivaniuk, Khrystyna ; Stakhira, Pavlo ; Cherpak, Vladyslav ; Chapran, Marian ; Grybauskaite-Kaminskiene, Gintare ; Grazulevicius, Juozas Vidas ; Dyakonov, Vladimir ; Sperlich, Andreas
DOI	10.1002/aelm.202000702
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Is Part of	Advanced electronic materials.. Weinheim : Wiley-VCH. 2021, vol. 7, iss. 3, art. no. 2000702, p. 1-9.. ISSN 2199-160X
Keywords [eng]	color tuning ; exciplexes ; organic light emitting diodes ; spin ; triplets
Abstract [eng]	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) (pCNBCzoCF3) 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.
Published	Weinheim : Wiley-VCH
Type	Journal article
Language	English
Publication date	2021
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„Spin- and voltage-dependent emission from intra- and intermolecular TADF OLEDs /“