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Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

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

HL 13.1: Talk

Monday, March 20, 2017, 11:00–11:15, ZEU 260

Two-color warm white hybrid OLEDs from thermally activated delayed fluorescence — •Ludwig Popp1, Paul Kleine1, Reinhard Scholz1, Ramunas Lygaitis1,2, Olaf Zeika1, Axel Fischer1, Simone Lenk1, and Sebastian Reineke11Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, TU Dresden, Germany — 2Kaunas University of Technology, Lithuania

Thermally activated delayed fluorescence (TADF) takes place in organic molecules where the energy splitting between the lowest excited singlet and triplet states (ST-splitting, Δ EST) remains sufficiently low. A newly designed sky-blue TADF emitter with an emission maximum at a wavelength of 500  nm reaches a photoluminescence quantum yield of 70 % and an external quantum efficiency (EQE) of up to 14.5 % in actual organic light-emitting devices (OLEDs).

In this work we use the sky-blue TADF molecule to build warm white hybrid OLEDs by combination with the red phosphorescent emitter Ir(MDQ)2(acac). Due to the very broad TADF emission, covering a majority of the high-energy visible spectrum, a dedicated deep blue emitter is becoming obsolete for reaching high color rendering indices (CRI > 80).

Furthermore, we demonstrate deeper insight into the energy transfer mechanisms in this hybrid TADF/phosphorescence approach. Time-correlated single photon counting enables to determine the actual exciton decay pathways and delivers a detailed understanding of the excitonic interplay between the particular excited states.

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