Events

Concepts for Phosphorescent Organic LEDs at High Brightness

May 24, 2010 at 3pm/36-428

Sebastian Reineke
Institut für Angewandte Photophysik, Dresden

abstract:
Organic light-emitting diodes (OLEDs) are next generation light sources which are especially attractive because they promise very high conversion efficiencies. The introduction of phosphorescent emitter materials was the key to enable internal quantum efficiencies approaching unity. However, due to the much longer excited state lifetime of triplet states even of state-of-the-art phosphors, bimolecular quenching limits the efficiency of such devices at high brightness – the latter is needed for future applications based on OLEDs.

In this talk, I will first discuss triplet-triplet annihilation (TTA) in an archetype host-guest system for green phosphorescence. Here, different models describing TTA are applied leading to the conclusion that emitter aggregation strongly enhances diffusion of excited states and, consequently, reduces the device efficiency. Based on these findings, I will discuss two concepts that improve the high brightness performance of phosphorescent OLEDs.

In the second part of the talk, I will focus on a novel concept for highly efficient white OLEDs. It makes use of a blue sub-emission layer, where host and guest triplet levels are in resonance, and thin intrinsic interlayers for the exciton management. This enables lower driving voltages and by that higher power efficiencies. In addition, I will present concepts for improved light outcoupling.

bio:
Sebastian Reineke is currently working as a Ph.D. candidate under the supervision of Prof. Karl Leo at the Institut für Angewandte Photophysik, Dresden. His main research interests are exciton dynamics and related phenomena in organic semiconductors with respect to their applications in optoelectronic devices. Since 3 years, he is tightly involved in the development of highly efficient white OLEDs. He was born in 1979 and studied physics in Heidelberg and Dresden. In 2005, he obtained the Diplomphysiker degree from the Technische Universität (TU) Dresden under the supervision of Prof. Karl Leo.  In 2006, acknowledging his diploma work in the field of organic LEDs, he was awarded with the Professor-Schwabe-Preis of the department of chemistry of the TU Dresden.