Dresden 2017 – wissenschaftliches Programm
CPP 7: Organic Electronics and Photovoltaics I: Light-Emitting Devices (joint session CPP/DS/HL, organized by CPP)
CPP 7.3: 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 Dyakonov1,2 — 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 EST 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.