An EngSci alum’s random walk to tracking energy’s random walks in light-harvesting materials

A countdown begins when sunlight hits a solar cell or a leaf. The absorbed energy typically has less than nanoseconds to reach a specific location — an electrode, or a site where it can be converted into a chemical bond — before it is lost as heat or re-emitted as light. Whether or not it succeeds depends on how the energy interacts with the local material in which it finds itself over a few tens of nanometres: how it is deflected by material vibrations, detained by defects, or rerouted by other forms of disorder. Bulk measurements average these effects out, such that new materials rarely perform as well as anticipated.

To improve a material’s potential for energy conversion, I advocate that we must watch the energy move in space and time on these important material scales. In this talk I will describe the physical principles and applications of stroboSCAT, an ultrafast imaging technique that we developed to record movies of energy moving through materials with sub-picosecond time resolution and few-nanometre sensitivity that can tell apart electronic, vibrational, thermal, and ionic energy carriers. I will next step through progressively more complex energy conversion systems: solution-processed solar cell materials, transition metal oxide photoelectrodes for artificial photosynthesis, and finally, the most direct measurements to date of energy transport inside natural photosynthetic systems. Time permitting, I will also share how these materials assemble in the first place, and how deliberately pushing that assembly out of equilibrium could enable us to build better ones.

Speaker bio:

Naomi S. Ginsberg is a Professor of Chemistry and Physics at UC Berkeley and a Faculty Scientist at Lawrence Berkeley National Laboratory (since 2010). Her research focuses on elucidating electronic and molecular dynamics in diverse optoelectronic, complex, and biological materials by developing new electron, X-ray, and optical imaging modalities to characterize dynamic processes at the nanoscale and over a wide range of time scales. She holds a B.A.Sc. in Engineering Science from the University of Toronto (2000) and a Ph.D. in Physics from Harvard (2007), followed by a Glenn T. Seaborg Postdoctoral Fellowship at LBNL. Her interdisciplinary background in engineering, physics, and chemistry 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. Dr. Ginsberg is the Berkeley lead of the STROBE NSF Science and Technology Center devoted to imaging science, a member of the Kavli Energy Nanoscience Institute, and the recipient of numerous honors, including a Packard Fellowship (2011), a DARPA Young Faculty Award (2012), an Alfred P. Sloan Foundation Fellowship (2015), a Camille Dreyfus Teacher-Scholar Award (2016), the Carol D. Soc Distinguished Graduate Student Mentoring Award (2022), the ACS Early-Career Award in Experimental Physical Chemistry (2020), APS Fellowship (2021), a Brown Investigator Award (2026), and multiple named lectureships and teaching awards.