Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 17: SKM Dissertation Prize
MA 17.4: Hauptvortrag
Dienstag, 15. März 2011, 12:00–12:30, TRE Ma
Controlling Excitons: Concepts for Phosphorescent Organic LEDs at High Brightness — •Sebastian Reineke — TU Dresden, Institut für Angewandte Photophysik, Dresden, Germany
Organic light-emitting diodes (OLEDs) attract much attention being a promising, energy-efficient technology with high color quality for display and lighting applications. Phosphorescence emitting materials prove to be inevitable because they can convert electrons into photons with an efficiency of one. Owing their comparably long exciton lifetime, non-linearities at high excitation levels noticeably reduce the emission efficiency (efficiency roll-off).1 Thus, especially the understanding and optimization of OLEDs (monochrome and white) at high, application-relevant brightness – typically a few thousand candela per square meter – are of high interest.
This contribution starts with a discussion of triplet-triplet annihilation (TTA) – the process that dominates the roll-off – in an efficient phosphorescent system.2 The results reveal that the nano-composition of the mixed film, where emitter molecules form aggregates, strongly decreases the high brightness efficiency. Based on these results, concepts for phosphorescent OLEDs will be introduced that show improved performance. Approaches to reduce TTA by altering the emission layer design as well as concepts for improved light-outcoupling will be discussed both for monochrome and white OLEDs.2
1 M. A. Baldo et al., Phys. Rev. B 62, 10967 (2000).
2 S. Reineke et al., Appl. Phys. Lett. 91, 123508 (2007) and 94, 163305 (2009); Nature 459, 234 (2009); Adv. Mater. 22, 3189 (2010).