PLEASE POST AND FORWARD TO YOUR GROUP Center for Excitonics Seminar Series Thursday, October 11, 2012 RLE Conference Room - 36-428 3:00 - 4:00pm Exciton Dynamics and Structural Investigations of Singlet Fission in Molecular Solids Michael Wasielewski -Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University Abstract: abstract: We are examining new dye molecules, which undergo singlet fission (SF), using guidance from electronic structure calculations to assure the requisite relationships between molecular singlet and triplet energy levels. We are preparing hierarchical assemblies from these chromophores, starting from covalent dimers and trimers, then developing supramolecular assemblies, and engineered crystalline materials to investigate SF in bulk, ordered materials. We are using femtosecond transient spectroscopy as well as time-resolved electron paramagnetic resonance spectroscopy to characterize the SF mechanism and the factors that determine its efficiency at time scales down to 100 fs. We are also using X-ray diffraction to investigate the single crystal structures of these materials and X-ray scattering on their thin polycrystalline solid films to determine how their structures correlate with their ability to carry out SF. Our results suggest that a p-p slip-stacked geometry is important for maximizing SF efficiency.io bio Professor Wasielewski received his Bachelor of Science (1971) and Ph.D. (1975) degrees from the University of Chicago. Following his graduate work, he was a postdoctoral fellow at Columbia University. He then joined the scientific staff of Argonne National Laboratory, where he rose through the ranks to become Group Leader of the Molecular Photonics Group. In 1994, he joined the faculty of Northwestern University, where he is currently the Clare Hamilton Hall Professor of Chemistry. He served as Chair of the Chemistry Department at Northwestern from 2001-2004. He is currently the Director of the Argonne-Northwestern Solar Energy Research (ANSER) Center, which is a DOE Energy Frontier Research Center, headquartered at Northwestern. Professor Wasielewski's research focuses on light-driven charge generation and transport in molecules and supramolecular materials, artificial photosynthesis, molecular systems for solar fuels and electricity, molecular electronics, spin dynamics, spintronics, and time-resolved optical and EPR spectroscopy. His research has resulted in over 410 publications. Professor Wasielewski was elected a Fellow of the American Association for the Advancement of Science in 1995, and has held numerous distinguished lectureships and fellowships. Among Professor Wasielewski's recent awards are the 2012 Arthur C. Cope Scholar Award of the American Chemical Society, the 2008 Porter Medal for Photochemistry, the 2006 James Flack Norris Award in Physical Organic Chemistry of the American Chemical Society, and the 2004 Photochemistry Research Award of the Inter-American Photochemical Society.