Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 38: Organic semiconductors

HL 38.5: Talk

Thursday, April 4, 2019, 10:30–10:45, H33

Electron paramagnetic resonance detected in a metal-free fluorescence-phosphorescence dual-emitter OLED — •Tobias Grünbaum, Wolfram Ratzke, Sebastian Milster, Sebastian Bange, and John M. Lupton — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany

Organic light-emitting diodes (OLEDs) constitute an ideal model system for investigating spin-dependent phenomena in condensed matter physics. A tool for direct access to the spin symmetry of charge carrier pairs in OLEDs is electron paramagnetic resonance (EPR) [1].

We performed EPR measurements on OLEDs comprising the dual emitting host-guest system CBP:DMDB-PZ [2]. This allows us to simultaneously detect the effect of both static as well as high frequency magnetic fields on the ratio of singlet and triplet charge-carrier pairs. We find the anticipated anti-correlation of singlet and triplet light emission in magneto-electroluminescence as well as under EPR. Due to the precise control of molecular design, spin-orbit as well as hyperfine interaction can be selectively tuned and investigated. We anticipate that the EPR technique can be applied to identify the region of the device where formation of charge-carrier pairs takes place, since differing distributions of the hyperfine fields are expected in different molecular scaffolds.

[1]: Baker, W. J. et al., Nat. Commun. 3, 898 (2012)

[2]: Ratzke, W. et al., Phys. Rev. Appl. 9, 054038 (2018)