Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 16: Organic Semiconductors

HL 16.7: Talk

Tuesday, March 18, 2025, 11:15–11:30, H14

Electrical and Optical Processes in Blue TADF OLEDs Studied by Temperature-Dependent Spectroscopy — •Ahmed Mohamed, Felix Kübert, Klara-Maria Bögle, Tolga Durmus, Vladimir Dyakonov, and Andreas Sperlich — Experimental Physics 6, University of Würzburg, 97074 Würzburg, German

This study explores the electrical and photophysical processes in Thermally-Activated Delayed Fluorescence (TADF) Organic Light- Emitting Diodes (OLEDs) using temperature-dependent spectroscopic techniques. Key aspects such as charge carrier transport, current loss mechanisms and recombination dynamics are examined to pro- vide a comprehensive understanding of device performance. We analyze current density-voltage-luminance (JVL) with respect to leak- age current, efficiency roll-off, and current density at 90% external quantum efficiency *90. Electroluminescence (EL)/photoluminescence (PL) microscopy is employed to analyze the photophysical processes in OLEDs. EL spectra of blue OLEDs with the multi-resonance emitter *-DABNA exhibit remarkable spectral stability at temperatures be- tween 200-300 K. Analysis of transient EL with rate equations yields activation energy and the rates of triplet-singlet transitions in OLEDs, including reverse intersystem crossing (rISC), triplet-triplet annihilation (TTA), and triplet-polaron annihilation (TPA). Understanding the mechanisms of current loss and (non-)radiative transitions is the prerequisite for enhancing the efficiency and stability of blue OLEDs.

Keywords: OLED; TADF; Temperature-Dependent EL; current loss