Regensburg 2016 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Focus: Triplet States in Organic Optoelectronics I
CPP 32.1: Invited Talk
Wednesday, March 9, 2016, 09:30–10:00, H37
Towards 100% efficient OLEDs using thermally activated delayed fluorescence; how does the spin conversion work — •Andrew Monkman1, Marc Etherington1, Paul Klein1,2, David Graves1, Przemyslaw Data1, Paloma dos Santos Lays1, Roberto Nobuyasu1, Youhei Tacked3, and Fernando Dias1 — 1Durham University, Durham, England — 2Technical University, Dresden, Germany — 3Osaka University, Osaka, Japan
Detailed photophysical measurements of intramolecular charge transfer (ICT) states have been made both in solution and solid state. Temperature dependent time resolved emission, delayed emission and photoinduced absorption are used to map the energy levels involved in molecule decay, and through detailed kinetic modelling of the thermally activated processes observed, true electron exchange energies and other energy barriers of the systems determined with the real states involved in the reversed intersystem crossing mechanism elucidated.
For specific donor acceptor molecules, the CT singlet and local triplet states (of donor or acceptor) are found to be the lowest lying excited states of the molecule with very small energy barrier between them. In these cases the decay kinetics of the molecules become significantly different to normal molecules, and the effect of rapid recycling between CT singlet and local triplet states is observed which gives rise to the true triplet harvesting mechanism in TADF. Using a series of different TADF emitters we will show how the energy level ordering effects or does not effect TADF and how ultimate OLED performance is dictated by energy level ordering, from 5% to 22% EQE