Physical Chemistry Seminar

Chemistry Seminar Program

Physical Chemistry Seminar
Tuesday, February 16th 
Professor Michael Wasielewski, Northwestern University
"Photo-driven Processes in Self-ordering Organic Semiconductors"

4:30pm Braun Lecture Hall
S.G. Mudd Building
Stanford University

About the Seminar: 
Self-assembly of small electron donor-acceptor (D-A) molecules into discrete and monodisperse nanostructures can result in architectures with unique inter-chromophore relationships that are otherwise difficult to realize by conventional covalent synthesis. In particular, p-stacked covalent D-A molecules can afford ordered and segregated D/A domains through which photo-generated holes and electrons can be rapidly transported. The design of these systems must ensure that charge hopping of the separated holes and electrons between the non-covalent donors and acceptors within their respective segregated conduits must be significantly faster than charge recombination (Figure 1). We will discuss several strategies to achieve this behavior that have implications in the design of photovoltaics and photocatalysts.
We are also developing new organic semiconductors that undergo singlet fission (SF), the spontaneous down-conversion of a singlet exciton into two triplet excitons (Figure 2), using guidance from electronic structure calculations. We are investigating hierarchical assemblies of these chromophores ranging from dimers to engineered crystalline materials using ultrafast optical spectroscopy to characterize the SF mechanism and the factors that determine its efficiency. We will present new results on the role of the electronic states implicated in enabling SF in organic semiconductors.

About the Speaker: 
Michael R. Wasielewski is the Clare Hamilton Hall Professor of Chemistry, Northwestern University, Executive Director of the Institute for Sustainability and Energy at Northwestern, Director of the Argonne-Northwestern Solar Energy Research Center, a US-DOE Energy Frontier Research Center, and Executive Director of the Solar Fuels Institute, a global consortium of energy research centers.  He received his Ph.D. from the University of Chicago and was a postdoctoral fellow at Columbia University. He began his career at Argonne National Laboratory, where he advanced to Senior Scientist and Group Leader.  In 1994, he joined the faculty of Northwestern University.  His research has resulted in over 500 publications and focuses on light-driven processes in molecules and materials, artificial photosynthesis, molecular electronics, and molecular spintronics. Among his recent awards are the 2016 American Institute of Chemists, Chemical Pioneer Award; the 2015 Honda-Fujishima Award of the Japanese Photochemistry Association; the 2013 Royal Society of Chemistry Environment Prize; a 2013 Humboldt Research Award; a 2012 Arthur C. Cope Scholar Award of the American Chemical Society; the 2008 Porter Medal for Photochemistry; and the 2006 James Flack Norris Award in Physical Organic Chemistry of the American Chemical Society.
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