Perdeuteration of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (d-MEHPPV): control of microscopic charge-carrier spin-spin coupling and of magnetic-field effects in optoelectronic devices

Control of the effective local hyperfine fields in a conjugated polymer, poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV), by isotopic engineering is reported. These fields, evident as a frequency-independent line broadening mechanism in electrically detected magnetic resonan...

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Published in:arXiv.org 2019-09
Main Authors: Stoltzfus, Dani M, Joshi, Gajadhar, Popli, Henna, Jamali, Shirin, Kavand, Marzieh, Milster, Sebastian, Grünbaum, Tobias, Bange, Sebastian, Nahlawi, Adnan, Teferi, Mandefro Y, Atwood, Sabastian I, Leung, Anna E, Darwish, Tamim A, Malissa, Hans, Burn, Paul L, Lupton, John M, Boehme, Christoph
Format: Article
Language:English
Subjects:
Current carriers
Deuteration
Diodes
Electron spin
Hall effect
Hydrogen isotopes
Hyperfine structure
Line broadening
Magnetic resonance spectroscopy
Magnetoresistance
Magnetoresistivity
Optoelectronic devices
Organic light emitting diodes
Polymers
Resonance lines
Spectrum analysis
Spin-orbit interactions
Spin-spin coupling
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Summary:Control of the effective local hyperfine fields in a conjugated polymer, poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV), by isotopic engineering is reported. These fields, evident as a frequency-independent line broadening mechanism in electrically detected magnetic resonance spectroscopy (EDMR), originate from the unresolved hyperfine coupling between the electronic spin of charge carrier pairs and the nuclear spins of surrounding hydrogen isotopes. The room temperature study of effects caused by complete deuteration of this polymer through magnetoresistance, magnetoelectroluminescence, coherent pulsed and multi-frequency EDMR, as well as inverse spin-Hall effect measurements, confirm the weak hyperfine broadening of charge carrier magnetic resonance lines. As a consequence, we can resolve coherent charge-carrier spin-beating, allowing for direct measurements of the magnitude of electronic spin-spin interactions. In addition, the weak hyperfine coupling allows us to resolve substantial spin-orbit coupling effects in EDMR spectra, even at low magnetic field strengths. These results illustrate the dramatic influence of hyperfine fields on the spin physics of organic light-emitting diode (OLED) materials at room temperature, and point to routes to reaching exotic ultra-strong resonant-drive regimes needed for the study of light-matter interactions.
ISSN:2331-8422
DOI:10.48550/arxiv.1909.12213