My research group interrogates dynamic nanoscale processes in energy-related materials, especially those involved in solar light harvesting, as is for example the case in photosynthesis. The most prevalent materials that we consider are intended for next-generation photovoltaics and are all formed through deposition from the solution-phase or using solution-phase self-assembly. Although this approach to material formation is facile and energy efficient, it often results in heterogeneous, kinetically trapped structures far from equilibrium. One of our main goals is therefore to elucidate how these materials' physical structure, including the nature of their heterogeneities and defects, determines their emergent optoelectronic properties. Ultimately, establishing such structure-function relationships will enable us to suggest specific solution-phase approaches to material formation that generate optimally performing functional materials.
Achieving a nanoscale understanding of dynamic processes in heterogeneous energy-related materials is challenging because it requires achieving unprecedented combinations of spatial and temporal measurement resolution. From a practical standpoint, we have therefore had to conceive of and develop multiple new forms of dynamic optical microscopies with sub-diffraction resolution, each tailored to a particular class of materials and their associated femtosecond-to-minutes dynamics. For resolving the dynamics of excitation energy flow we primarily employ ultrafast optical microscopies; to resolve dynamic material structures we primarily extend the applicability cathodoluminescence microscopy—the mapping of light emitted from a sample in a scanning electron microscopy—to soft materials otherwise too delicate to withstand electron beam irradiation. I will describe a recent example from each category, taking you first on a journey to discover the nature of energy landscapes in disordered, electronically-coupled molecular aggregates, and second, to elucidate the manner by which light can lead to steady-state charge carrier traps by inducing local changes in structure and composition in solid solutions of halides in hybrid perovskite photovoltaics.
Naomi S. Ginsberg is an Associate Professor of Chemistry and Physics at University of California, Berkeley and a Faculty Scientist in the Materials Sciences and Molecular Biophysics and Integrated Imaging Divisions at Lawrence Berkeley National Laboratory, where she has been since 2010. She currently focuses on elucidating the electronic and molecular dynamics in a wide variety of soft electronic and biological materials by devising new electron and optical imaging modalities that enable characterization of fast and ultrafast processes at the nanoscale and as a function of their heterogeneities. Naomi received a B.A.Sc. degree in Engineering Science from the University of Toronto in 2000 and a Ph.D. in Physics from Harvard University in 2007, after which she held a Glenn T. Seaborg Postdoctoral Fellowship at Lawrence Berkeley National Lab. Her background in chemistry, physics, and engineering has previously led her to observe initiating events of photosynthesis that take place in a millionth billionth of a second and to slow, stop, and store light pulses in some of the coldest atom clouds on Earth. She is the Berkeley lead of STROBE, a multi-university NSF Science and Technology Center devoted to imaging science, a member of the Kavli Energy Nanoscience Institute at Berkeley, and the recipient of a David and Lucile Packard Fellowship in Science and Engineering (2011), a DARPA Young Faculty Award (2012), an Alfred P. Sloan Foundation Fellowship (2015), and a Camille Dreyfus Teacher-Scholar Award (2016) in addition to a series of teaching awards in the physical sciences. This academic year she is also a Miller Professor for Basic Science at UC Berkeley.