Excited State Dynamics of Photoexcited Charge Carriers in Halide Perovskites: Time-Domain Ab Initio Studies
Prof. Oleg Prezhdo
University of Southern California, USA

Photo-induced processes play key roles in photovoltaic and photo-catalytic applications of halide perovskites. They require understanding of the material’s dynamical response to the photo-excitation on atomic and nanometer scales. Our non-adiabatic molecular dynamics techniques, implemented within time-dependent density functional theory, allow us to model such non-equilibrium response in the time domain and at the atomistic level. The talk will focus on photo-initiated energy and charge transfer, relaxation and recombination in hybrid organic-inorganic perovskites. Considering realistic aspects of perovskite structure, we demonstrate that strong interaction at the perovskite/TiO2 interface facilitates ultrafast charge separation, how dopants can be used to both decrease and increase charge recombination, that grain boundaries constitute a major reason for charge losses, that moderate humidity increases charge lifetime, while high humidity accelerates losses, that hole trapping by iodine interstitial, surprisingly, extends carrier lifetime, that collective nature of dipole motions inhibits nonradiative relaxation, that organic cation orientation has a strong effect on inorganic ion diffusion and current-voltage hysteresis, that surface passivation with Lewis base molecules decelerates nonradiative charge recombination by an order of magnitude, and that the experimentally observed dual (hot/cold) fluorescence originates from two types of perovskites substructures. Our simulations provide a unifying description of quantum dynamics on the nanoscale, characterize the rates and branching ratios of competing processes, resolve debated issues, and generate theoretical guidelines for development of novel systems for solar energy utilization.

About the Speaker

Oleg V. Prezhdo obtained a Diploma in Theoretical Chemistry in 1991 from Kharkiv National University, Ukraine, under Anatoly Luzanov. He completed his Ph.D. with Peter Rossky at the University of Texas, Austin. After a postdoctoral fellowship with John Tully at Yale University, he joined the chemistry department at the University of Washington in 1998, achieving Associate and Full Professor in 2002 and 2005. In 2008, he was elected Fellow of the American Physical Society. In 2010, he was offered a Senior Professorship at the University of Rochester, and in 2014 at the University of Southern California. Since 2008, he has served as editor for the Journal of Physical Chemistry, since 2011 for the Journal of Physical Chemistry Letters, and since 2012 for Progress in Surface Science. Recipient of multiple national and international awards, he held invited professorships in France, Germany, and Japan. His current research interests range from fundamental aspects of semiclassical physics, to excitation dynamics in nano-scale and biological systems.

2018-04-23 10:00 AM
Room: A403 Meeting Room
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