FIP Seminar Co-hosted with Department of Chemistry: Modern Alchemy-Making Copper Look Like Iridium and Platinum

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Wed, 11/13/2019 - 12:00 to 13:00

Mark Thompson

Presenter

Dr. Mark Thompson, Professor, Ray R. Irani Chair of Chemistry, Departments of Chemistry, Chemical Engineering and Materials Science, University of Southern California

There has been a great deal of effort targeted at finding alternatives to iridium-based emitters in organic LEDs (OLEDs), with Cu(I) complexes attracting a great deal of attention. In my talk I will discuss the synthesis, structural characterization and photophysical properties of several, two coordinate copper, silver and gold carbene complexes. Here we will focus on a number of different N-heterocyclic carbenes (NHCs). Using different carbene and X ligands, the emission color can be shifted from violet to deep red. These complexes show good phosphorescence quantum yield (PL = 0.3 – 1.0), with radiative lifetimes in 0.4-3 microsecond regime in fluid solution and in thin film form. We have carried out cryogenic photophysical measurements and show that these compounds emit via E-type delayed fluorescence (also called thermally assisted delayed fluorescence, TADF), with a singlet-triplet gap as low as 200 cm-1 (25 meV) for the Ag-based materials and zero filed splitting values as high as 85, 75 and 225 cm-1, for Cu-, Ag- and Au-based compounds, respectively. Both of these values are exceptional for phosphorescent emitters and copper-based compounds. I will discuss our modelling studies to determine the origin of these exceptional properties, discuss the photophysical properties and our understanding of them through the theoretical modelling and photophysical studies of these complexes. 

We have prepared organic LEDs with these dopants and achieved > 20% EQE for green emissive OLEDs and > 12% for blue emissive OLEDs, both at comparatively low drive voltages. 

Mark Thompson received his B.S. degree in Chemistry in 1980 (U.C. Berkeley) and his Ph.D. in chemistry in 1985 (California Institute of Technology). He spent 2 years as a postdoctoral fellow at Oxford University before taking a position in the chemistry department at Princeton University in 1987, as an assistant professor. In 1995, he moved his research team to the University of Southern California where he holds the Ray R. Irani Chair of Chemistry. His research involves the study of materials and devices for electroluminescence, photovoltaics and solar cells, chemical/biological sensing and catalysis. Prof. Thompson is the author of approximately 400 papers in refereed professional journals and holds more than 250 patents primarily in the areas of optoelectronic applications, such as light emitting devices (LEDs) and solar cells. He is a fellow of the AAAS and National Academy of Inventors. He has received multiple awards for his work in organic LEDs, including the MRS Medal (2006), the Jan Rajchman Medal from the Society for Information Display (2006), ACS Richard C. Tolman Award (2011) and the ACS Chemistry of Materials Award (2015) and most recently he was awarded the IEEE Photonics award in 2016 and the Nishizawa Medal in 2017.