Basic Research from Natural Photosynthesis to Synthetic Solar Fuel and Solar Electricity Conversion Systems

Fundamental processes in solar energy conversion involve photon-matter interactions through light harvesting, excited state formation and subsequent conversion to electricity, heat and fuels. Natural photosynthetic systems have demonstrated principles and key factors in light to electricity/fuel conversion, but extensive research needs to be carried out in search of optimal structural, energetic and dynamic parameters for efficient synthetic systems for solar energy conversion. Intense X-ray pulses from DOE supported synchrotrons and X-ray free electrons lasers coupled with ultrafast lasers open up new opportunities to reveal transient structural information as photochemical processes take place in photocatalysts, photosensitizers, and photovoltaic materials. In particular, element dependent electronic configurations (e.g., molecular orbital vacancies), transient oxidation states of metal centers in catalysts can be unambiguously identified with accompanying nuclear geometric transformations. Such studies combined with materials design with chemically modified structural factors can provide feedback for generating efficient, cost-saving, and durable materials. The lecture will provide an overview of current solar fuel and solar electricity research highlighted by the work using intense X-ray pulses to take molecular snapshots/movies. These results have a tremendous impact on our understanding of the coupling between the electron transfer and structural control parameters of participating partners in solar fuel and solar electricity generation. The lecture will also describe new direction in organic photovoltaics, in which the conventional models are challenged due to intrinsic molecular charge transfer characters. The results imply that charge-transfer polymers, which are already achieving record-breaking efficiencies, can be predictably altered to enhance corresponding device efficiency by optimizing the electron-withdrawing or -pushing interaction of neighboring backbone building blocks to facilitate exciton dissociation.

Lin X. Chen is a Senior Chemist in Argonne National Laboratory and a Professor of Chemistry at Department of Chemistry, Northwestern University. Her research is currently focused on ultrafast transient molecular structural studies in solar energy conversion processes and structures-dynamics-efficiency correlations in organic photovoltaic materials using ultrafast laser and X-ray spectroscopies and X-ray structural characterization. She received her B.Sc. from Peking University and Ph.D. from the University of Chicago. After her postdoctoral research at the University of California at Berkeley, she joined Argonne National Laboratory as a staff scientist. She is an AAAS Fellow and has won distinguished performance award at Argonne.

Her group website is at http://chemgroups.northwestern.edu/chen_group/.