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 Reineke1 — 1Dresden 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.