Scharff, Tobias and Ratzke, Wolfram and Zipfel, Jonas and Klemm, Philippe and Bange, Sebastian and Lupton, John M. (2021) Complete polarization of electronic spins in OLEDs. NATURE COMMUNICATIONS, 12 (1): 2071. ISSN 2041-1723,
Full text not available from this repository. (Request a copy)Abstract
At low temperatures and high magnetic fields, electron and hole spins in an organic light-emitting diode become polarized so that recombination preferentially forms molecular triplet excited-state species. For low device currents, magnetoelectroluminescence perfectly follows Boltzmann activation, implying a virtually complete polarization outcome. As the current increases, the magnetoelectroluminescence effect is reduced because spin polarization is suppressed by the reduction in carrier residence time within the device. Under these conditions, an additional field-dependent process affecting the spin-dependent recombination emerges, possibly related to the build-up of triplet excitons and their interaction with free charge carriers. Suppression of the EL alone does not prove electronic spin polarization. We therefore probe changes in the spin statistics of recombination directly in a dual singlet-triplet emitting material, which shows a concomitant rise in phosphorescence intensity as fluorescence is suppressed. Finite spin-orbit coupling in these materials gives rise to a microscopic distribution in effective g-factors of electrons and holes, Delta g, i.e., a distribution in Larmor frequencies. This Delta g effect in the pair, which mixes singlet and triplet, further suppresses singlet-exciton formation at high fields in addition to thermal spin polarization of the individual carriers. Though literature reports magnetoelectroluminescence (MEL) affects in organic light-emitting diodes (OLEDs), probing the organic layer's effective spin polarization remains a challenge. Here, the authors utilize dual singlet-triplet emitting OLEDs to reveal the spin polarization in the materials.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | LIGHT-EMITTING-DIODES; DELTA-G MECHANISM; TRANSIENT ELECTROLUMINESCENCE; DEPENDENT RECOMBINATION; TRIPLET EMITTERS; ULTRAHIGH FIELDS; OVERSHOOT; INJECTION; TRANSPORT; MAGNETORESISTANCE; |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Experimental and Applied Physics > Chair Professor Lupton > Group John Lupton |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 12 Jul 2022 06:29 |
| Last Modified: | 12 Jul 2022 06:29 |
| URI: | https://pred.uni-regensburg.de/id/eprint/45711 |
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