CGSO Sponsored Seminar
About the Seminar:
Heavy metal containing phosphors, especially iridium-based emitters, have become the standard in high performance mobile displays and televisions. The high spin orbit coupling in these compounds facilitates the efficient harvesting of both singlet and triplet excitons generated in the electroluminescent process. An alternative to Ir-based emitters are solely-organic emitters based on Thermally Assisted Delayed Fluorescence (TADF). Heavy-metal and TADF emitters give similar OLED performance, which stems from the fact that they give very similar radiative lifetimes. We have found that the key to achieving higher performance for TADF emitters is to put the metal ions back into the TADF emitters. My talk will focus on the photophysical and electroluminescent properties of two coordinate copper, silver and gold carbene complexes, i.e. (carbene)MI(donor), where the donor is an amide or aryl group. These complexes show high phosphorescence quantum yield (PLQY = 0.7 – 1.0), with radiative lifetimes in 0.4-3 microsecond regime. Cryogenic photophysical measurements show these TADF emitters have singlet-triplet gaps as low as 150 cm-1 (20 meV). 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.
About the Speaker:
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.