Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 45: HL Posters III

HL 45.36: Poster

Thursday, April 4, 2019, 18:30–21:00, Poster E

Multifrequency Spin-Resonance Experiments on organic LEDs based on Triplet-Singlet Conversion — •Rebecca Bönnighausen, Sebastian Weissenseel, Sebastian Lulei, Vladimir Dyakonov, and Andreas Sperlich — Experimental Physics VI, Julius Maximilian University of Würzburg

In organic light emitting diodes (OLEDs), which are based on thermally activated delayed fluorescence (TADF), the small energy splitting Δ E_ST between singlet and triplet states is utilized to achieve an increased light output. The so called exciplexes (weakly bound e-h pairs) in the triplet state can upconvert from the triplet state to the singlet state via reverse intersystem crossing (RISC). This process can be investigated by spin sensitive techniques such as electroluminescence detected magnetic resonance (ELDMR). The triplet states split in an external magnetic field and transitions between those states can be induced by resonant microwaves, which results in a detectable change in the luminescence. We investigate the change to this ELDMR spectrum if an additional microwave frequency is applied to the sample. It saturates the spin transition, which is seen as a spectral hole burning. We discuss the mechanism responsible for such "hole burning" and its practical use to enhance the sensitivity of ELDMR due to the inhomogeneous linewidth to probe the interspin coupling in OLEDs for TADF and the involved mechanisms of RISC and interspin coupling.