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Perdeuterated Conjugated Polymers for Ultralow‐Frequency Magnetic Resonance of OLEDs
Author(s) -
Milster Sebastian,
Grünbaum Tobias,
Bange Sebastian,
Kurrmann Simon,
Kraus Hermann,
Stoltzfus Dani M.,
Leung Anna E.,
Darwish Tamim A.,
Burn Paul L.,
Boehme Christoph,
Lupton John M.
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202002477
Subject(s) - zeeman effect , larmor precession , hyperfine structure , magnetic field , electron paramagnetic resonance , resonance (particle physics) , magnetostatics , pulsed epr , condensed matter physics , spin (aerodynamics) , paramagnetism , atomic physics , materials science , chemistry , physics , nuclear magnetic resonance , spin echo , magnetic resonance imaging , medicine , quantum mechanics , radiology , thermodynamics
The formation of excitons in OLEDs is spin dependent and can be controlled by electron‐paramagnetic resonance, affecting device resistance and electroluminescence yield. We explore electrically detected magnetic resonance in the regime of very low magnetic fields (<1 mT). A pronounced feature emerges at zero field in addition to the conventional spin‐ 1 / 2 Zeeman resonance for which the Larmor frequency matches that of the incident radiation. By comparing a conventional π‐conjugated polymer as the active material to a perdeuterated analogue, we demonstrate the interplay between the zero‐field feature and local hyperfine fields. The zero‐field peak results from a quasistatic magnetic‐field effect of the RF radiation for periods comparable to the carrier‐pair lifetime. Zeeman resonances are resolved down to 3.2 MHz, approximately twice the Larmor frequency of an electron in Earth's field. However, since reducing hyperfine fields sharpens the Zeeman peak at the cost of an increased zero‐field peak, we suggest that this result may constitute a fundamental low‐field limit of magnetic resonance in carrier‐pair‐based systems. OLEDs offer an alternative solid‐state platform to investigate the radical‐pair mechanism of magnetic‐field effects in photochemical reactions, allowing models of biological magnetoreception to be tested by measuring spin decoherence directly in the time domain by pulsed experiments.