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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 32: Focus: Triplet States in Organic Optoelectronics I

CPP 32.2: Vortrag

Mittwoch, 9. März 2016, 10:00–10:15, H37

Thermally activated delayed fluorescence – A new route to more efficient OLEDs? — •Reinhard Scholz¹, Ramunas Lygaitis^1,2, 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 Δ_ST=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 S_n 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.