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HL: Fachverband Halbleiterphysik

HL 13: Organic Electronics and Photovoltaics I: Light-Emitting Devices

HL 13.3: Vortrag

Montag, 20. März 2017, 11:30–11:45, ZEU 260

Investigation of organic light emitting diodes based on thermally activated delayed fluorescence via magnetic resonance methods — •Nikolai Bunzmann¹, Sebastian Weissenseel¹, Benjamin Krugmann¹, Jeannine Grüne¹, Stefan Väth¹, Andreas Sperlich¹, and Vladimir Dyakonov^1,2 — ¹Experimental Physics VI, Julius Maximilian University of Würzburg, 97074 Würzburg — ²Bavarian Center for Applied Energy Research (ZAE Bayern), 97074 Würzburg

Organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) exhibit a high upconversion rate from non-emissive triplet to emissive singlet states due to a small energy splitting Δ E_ST between the respective states. Consequently, the internal quantum efficiency (IQE) of such devices is strongly enhanced. However, the underlying mechanism of reverse intersystem crossing (RISC) is naturally spin forbidden, wherefore spin sensitive measurement methods are desirable in order to elucidate the TADF process. Therefore, we use electrically and electroluminescence detected magnetic resonance (EDMR, ELDMR) techniques. Hereby, transitions between triplet substates, which are split in an external magnetic field, are driven by microwaves, applied via a non-resonant stripline. We evaluate the dependence of multi-frequency ELDMR and EDMR spectra on changes in experimental conditions in order to obtain detailed information about the investigated spin system. Thereby we contribute to a better understanding of the TADF mechnism, which is crucial in order to further improve the performance of OLED based light sources.