Inorganic Chemistry Seminar: Professor Mark Thompson, USC (Host: Dan Stack)
"Organic LEDs Utilizing Heavy and Not So Heavy Metal-Complex Emitters"
About the Seminar
Organic Light Emitting Diodes (OLEDs) have increasingly been used in display and lighting applications do to their high efficiencies and color tuning ability. Commercial products utilize organometallic iridium complexes for generating green and red light in mobile displays. The goal of achieving efficient and long lived blue emission from Ir complexes has been a challenge. I will discuss our results to date with the goal of producing efficient Ir-based blue emitters for OLEDs. A parallel goal has been to replace Ir with less expensive metal complexes, such as copper based complexes. The switch to copper opens up the door to a number of problems in achieving highly efficient phosphorescence and a high radiative rate. We have come a long way toward achieving high efficiency and high radiative rate for blue, green and yellow emitting copper complexes. I will discuss our results in this area as well.
In parallel to our photophysical studies of phosphorescent emitters, the orientation of phosphorescent emitters in the OLED has been studied as a pathway to further increase the external quantum efficiency of these devices. This approach has the potential to nearly double the amount of light that comes out of the OLED. To achieve this high OLED efficiency, the emitting molecules must spontaneously align in an isotropic matrix. This has been reported by our group and others, but until now there have been no conclusive studies defining how to design complexes to control or enhance this alignment. We will discuss both OLED and optical studies that bear on the degree of emitter alignment in doped films for Ir(C^N)3, and (C^N)2Ir(ancillary) complexes. We have also examined (C^N)Pt(ancillary) complexes and found that doped films of these planar dopants also spontaneously align in amorphous host materials. We will also discuss our approach to determining and “tuning” the orientation of the phosphorescence transition dipole moment with respect to molecular frame, which is critical for achieving productive dopant alignment in doped films. The mechanism of dopant alignment will be discussed.
About the Speaker
Prof. Mark E. Thompson is Professor of Chemistry, Materials Science and Chemical Engineering at the University of Southern California. Prof. 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 Materials Research Society Medal (2006), the Jan Rajchman Medal from the Society for Information Display (2006), Richard C. Tolman Award (2011) and the Chemistry of Materials Award (2015) both from the American Chemical society, Alexander von Humboldt Research Award (2015) and most recently he was awarded the IEEE Photonics award in 2016 and the Nishizawa Medal in 2017. In 2011 he was ranked 12th of the top 100 chemists worldwide for their citation impact scores for chemistry papers published since January 2000, by Thomson Reuters Web of Science.