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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Focus: Triplet States in Organic Optoelectronics I
CPP 32.2: Talk
Wednesday, March 9, 2016, 10:00–10:15, H37
Thermally activated delayed fluorescence – A new route to more efficient OLEDs? — •Reinhard Scholz1, Ramunas Lygaitis1,2, Paul Kleine1, Ludwig Popp1, Florian Wüst1, Simone Lenk1, and Sebastian Reineke1 — 1Institut für Angewandte Photophysik, Technische Universität Dresden, Germany — 2Department of Organic Technology, Kaunas University of Technology, Lithuania
In molecules with small splitting between the lowest excited singlet and triplet states, reverse intersystem crossing (RISC) from the triplet to the singlet requires only a small activation energy, resulting in thermally activated delayed fluorescence (TADF). Donor-acceptor compounds with large dihedral angle between these subgroups allow for rather low singlet-triplet splitting ΔST=E(S1→ S0)−E(T1→ S0) between the observed fluorescence and phosphorescence transitions, at the price of a reduced transition dipole and slow radiative recombination rate. The present contribution investigates radiative recombination from thermal distributions in the excited potential surfaces Sn of TADF emitters with time-dependent density functional theory. On this basis, we suggest possible synthesis strategies for blue TADF emitters and report on selected compounds compromising between different desirable properties. The resulting OLEDs show external quantum efficiencies (EQE) between typical fluorescent and phosphorescent emitters, paving the way towards applications of white OLEDs to more efficient lighting.