Regensburg 2016 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Focus: Triplet States in Organic Optoelectronics I
CPP 32.7: Talk
Wednesday, March 9, 2016, 11:45–12:00, H37
Electron-hole-pair magnetoresistance and magnetoelectroluminescence in OLEDs — •Hermann Kraus1, Sebastian Bange1, Ullrich Scherf2, and John M. Lupton1 — 1Universiät Regensburg, 93053 Regensburg, Germany — 2Bergische Universität Wuppertal, 42119 Wuppertal, Germany
Large magnetoresistance effects which arise, for example, due to spin-dependent recombination rates are well-known for OLEDs, although models are still under debate given that they remain hard to verify from a measurement of integrated current and luminance. Spin resonance of paramagnetic species enables direct manipulation of charge carrier and excitonic precursor spins, providing a wealth of new insight into dynamic spin properties.
Previous work on electrical or optical detection of spin manipulation misses out on the opportunity to directly observe the presence of triplet exciton species that are at the heart of spin-dependent recombination models. Fortunately, a few organic materials are now known to exhibit reasonable triplet emission without modification of the polaron pair and exciton dynamics by strong spin-orbit interaction. They are ideal candidates to directly track spin singlet and triplet excitonic species in OLEDs under conditions of magnetic resonance, by comparing the fluorescence (singlet) to phosphorescence (triplet) intensity. Phosphorescence increases under resonance while fluorescence is quenched. Additionally, the magnetoelectroluminescence of the OLED can be measured at the same time by sweeping the magnetic field to directly correlate resonant and static magnetic field effects.