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 T2* of 30 ns. Crucially, we obtain the characteristic triplet exciplex spin-lattice relaxation time T1 in the range of 50 μs, 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.
Description
Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes
%0 Journal Article
%1 Weissenseel_2021
%A Weissenseel, Sebastian
%A Gottscholl, Andreas
%A Bönnighausen, Rebecca
%A Dyakonov, Vladimir
%A Sperlich, Andreas
%D 2021
%I American Association for the Advancement of Science (AAAS)
%J Sci. Adv.
%K c
%N 47
%P eabj9961
%R 10.1126/sciadv.abj9961
%T Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes
%U https://doi.org/10.1126%2Fsciadv.abj9961
%V 7
%X 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 T2* of 30 ns. Crucially, we obtain the characteristic triplet exciplex spin-lattice relaxation time T1 in the range of 50 μs, 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.
@article{Weissenseel_2021,
abstract = {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 T2* of 30 ns. Crucially, we obtain the characteristic triplet exciplex spin-lattice relaxation time T1 in the range of 50 μs, 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.},
added-at = {2022-02-09T12:18:15.000+0100},
author = {Weissenseel, Sebastian and Gottscholl, Andreas and Bönnighausen, Rebecca and Dyakonov, Vladimir and Sperlich, Andreas},
biburl = {https://www.bibsonomy.org/bibtex/2a2b51057df602e3cdbf001f9c949d910/ctqmat},
day = 17,
description = {Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes},
doi = {10.1126/sciadv.abj9961},
interhash = {c67af6672652153a3fdad22e5b78458f},
intrahash = {a2b51057df602e3cdbf001f9c949d910},
journal = {Sci. Adv.},
keywords = {c},
month = {11},
number = 47,
pages = { eabj9961},
publisher = {American Association for the Advancement of Science ({AAAS})},
timestamp = {2023-10-17T12:27:32.000+0200},
title = {Long-lived spin-polarized intermolecular exciplex states in thermally activated delayed fluorescence-based organic light-emitting diodes},
url = {https://doi.org/10.1126%2Fsciadv.abj9961},
volume = 7,
year = 2021
}