Room-temperature coupling between electrical current and nuclear spins in OLEDs

Science  19 Sep 2014:
Vol. 345, Issue 6203, pp. 1487-1490
DOI: 10.1126/science.1255624

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Organic semiconductors go out for a spin

Magnetism is a commonly observed phenomenon in the macroscopic world, but its origins lie in the quirky quantum-mechanical property of electrons and certain nuclei known as spin. Recent research has sought to leverage and expand the role of spin in the operation of electronic devices. Malissa et al. used a highly sensitive spectroscopic technique to probe, and ultimately manipulate, the subtle effects of spin interactions on the current that flows through organic light-emitting diodes (OLEDs) (see the Perspective by Bobbert). They pinpointed coupling between the spins of the current carriers and the hydrogen nuclei in the hydrocarbon-based material making up the device.

Science, this issue p. 1487; see also p. 1450


The effects of external magnetic fields on the electrical conductivity of organic semiconductors have been attributed to hyperfine coupling of the spins of the charge carriers and hydrogen nuclei. We studied this coupling directly by implementation of pulsed electrically detected nuclear magnetic resonance spectroscopy in organic light-emitting diodes (OLEDs). The data revealed a fingerprint of the isotope (protium or deuterium) involved in the coherent spin precession observed in spin-echo envelope modulation. Furthermore, resonant control of the electric current by nuclear spin orientation was achieved with radiofrequency pulses in a double-resonance scheme, implying current control on energy scales one-millionth the magnitude of the thermal energy.

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