TY  - JOUR
A1  - Weissenseel, Sebastian
A1  - Gottscholl, Andreas
A1  - Bönnighausen, Rebecca
A1  - Dyakonov, Vladimir
A1  - Sperlich, Andreas
T1  - Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes
JF  - Science Advances
N2  - Spin-spin interactions in organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) are pivotal because radiative recombination is largely determined by triplet-to-singlet conversion, also called reverse intersystem crossing (RISC). To explore the underlying process, we apply a spin-resonance spectral hole-burning technique to probe electroluminescence. We find that the triplet exciplex states in OLEDs are highly spin-polarized and show that these states can be decoupled from the heterogeneous nuclear environment as a source of spin dephasing and can even be coherently manipulated on a spin-spin relaxation time scale T-2* of 30 ns. Crucially, we obtain the characteristic triplet exciplex spin-lattice relaxation time T-1 in the range of 50 mu s, which far exceeds the RISC time. We conclude that slow spin relaxation rather than RISC is an efficiency-limiting step for intermolecular donor:acceptor systems. Finding TADF emitters with faster spin relaxation will benefit this type of TADF OLEDs.
KW  - detected magnetic-resonance
KW  - population oscillations
KW  - polaron delocalization
KW  - charge separation
KW  - hole
KW  - phosphorescence
KW  - singlet
KW  - absorption
KW  - tryptophan
KW  - emission
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265508
VL  - 7
IS  - 47
ER  -