Spectrally resolved hyperfine interactions between polaron and nuclear spins in organic light emitting diodes: Magneto-electroluminescence studies

S. A. Crooker, F. Liu, M. R. Kelley, N. J.D. Martinez, W. Nie, A. Mohite, I. H. Nayyar, S. Tretiak, D. L. Smith, P. P. Ruden

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Abstract

We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I∼11%) than at the low-energy red end (∼4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.

Original languageEnglish (US)
Article number153304
JournalApplied Physics Letters
Volume105
Issue number15
DOIs
StatePublished - Oct 13 2014

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