Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Focus: Triplet States in Organic Optoelectronics I
CPP 32.6: Hauptvortrag
Mittwoch, 9. März 2016, 11:15–11:45, H37
Effects of charge and exciton diffusion on triplet-polaron quenching and triplet-triplet annihilation in disordered organic semiconductors — •Reinder Coehoorn1, Harm van Eersel2, Le Zhang1, Peter Bobbert1, and Rene Janssen1 — 1Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513 — 2Simbeyond B.V., Den Dolech 2, 5612 AZ Eindhoven, The Netherlands
Triplet-polaron quenching (TPQ) and triplet-triplet annihilation (TTA) contribute to the efficiency roll-off in organic light-emitting diodes (OLEDs). In fluorescent OLEDs, TTA can also be beneficial, giving rise to partial triplet harvesting, which manifests itself as delayed fluorescence. Conventionally, TTA and TPQ are viewed as bimolecular processes with a rate coefficient which depends on the local density of all species involved, and on their diffusivity. Often, the rate coefficient is expressed in terms of an effective capture radius. We show from kinetic Monte Carlo simulations that in actual OLEDs strong deviations can occur from this picture. Firstly, the effective exciton or charge diffusion coefficient can be strongly time dependent. Secondly, the percolative nature of the charge or exciton diffusion gives rise to a highly non-trivial dye concentration dependence. For the case of TTA, results of an experimental study are presented which provide a test of a novel method [1] for quantifying the role of exciton diffusion. [1] H. van Eersel et al., J. Appl. Phys. 117, 115502 (2015).