Berlin 2018 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 71: Organic Electronics and Photovoltaics - OLEDs and Molecular Excitations
CPP 71.2: Vortrag
Donnerstag, 15. März 2018, 15:15–15:30, C 243
The interplay of TADF and phosphorescence in warm-white hybrid OLEDs — •Ludwig Popp1, Paul Kleine1, Ramunas Lygaitis2, Reinhard Scholz1, Simone Lenk1, and Sebastian Reineke1 — 1Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, TU Dresden, Germany — 2Kaunas University of Technology, Lithuania
White emission in OLEDs is usually a combination of two or more different emitters with individual colors. Therefore, it is necessary that all included systems are efficient. It has been shown that the concept of thermally activated delayed fluorescence (TADF) allows to synthesize very efficient light-emitting molecules with various emission colors.
In our work, we use the sky-blue TADF emitter 5CzCF3Ph with an emission maximum at a wavelength of 495 nm, reaching a photoluminescence quantum yield of 70 % and up to 18 % external quantum efficiency (EQE) in OLEDs. By combination with the common phosphorescent red emitter Ir(MDQ)2(acac) within one emission layer it is possible to build warm white OLEDs with a high color rendering index of over 80 and correlated color temperatures about 2800 K.
Due to the variety of local and charge-transfer excited states in the emitter system, there are several probable scenarios for the energy transfer between 5CzCF3Ph and Ir(MDQ)2(acac) since excitons are formed mostly on the TADF emitter. Utilizing time-correlated single photon counting (TCSPC) with a wavelength-sensitive detection, we deliver a thorough investigation of the exciton transfer and exchange mechanisms in the emitter system of our warm-white hybrid OLEDs.