Photo-induced processes play key roles in photovoltaic and photo-catalytic applications of halide perovskites, requiring understanding of the material's dynamical response to the photo-excitation on atomic and nanometer scales. Our non-adiabatic molecular dynamics techniques,¹ implemented within time-dependent density functional theory,^2-4 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,⁵ we demonstrate that strong interaction at the perovskite/TiO₂ interface facilitates ultrafast charge separation,⁶ how dopants can be used to both decrease and increase charge recombination,^7-9 that grain boundaries constitute a major reason for charge losses,⁹ that moderate humidity increases charge lifetime, while high humidity accelerates losses,¹⁰ that hole trapping by iodine interstitial, surprisingly, extends carrier lifetime,¹¹ that collective nature of dipole motions inhibits nonradiative relaxation,¹² that organic cation orientation has a strong effect on inorganic ion diffusion and current-voltage hysteresis,¹³ that surface passivation with Lewis base molecules decelerates nonradiative charge recombination by an order of magnitude,¹⁴ that the experimentally observed dual (hot/cold) fluorescence originates from two types of perovskites substructures,¹⁵ that doping with larger cations increases lattice stiffness and slows down nonradiative charge recombination,¹⁶ why PbI₂ rich perovskites show better performance,¹⁷ that halide composition can be used to control charge relaxation,¹⁸ that oxidation states of halide defects strongly influence charge trapping and recombination,¹⁹ and why perovskites exhibit unusual temperature dependence of electron and hole lifetimes.²⁰

[1] Wang, L. J.; Akimov, A.; Prezhdo, O. V., Recent Progress in Surface Hopping: 2011-2015. J. Phys. Chem. Lett. 2016, 7, 2100-2112.

[2] Akimov, A. V.; Prezhdo, O. V., The Pyxaid Program for Non-Adiabatic Molecular Dynamics in Condensed Matter Systems. J. Chem. Theory Comput. 2013, 9, 4959-4972.

[3] Akimov, A. V.; Prezhdo, O. V., Advanced Capabilities of the Pyxaid Program: Integration Schemes, Decoherenc:E Effects, Multiexcitonic States, and Field-Matter Interaction. J. Chem. Theory Comput. 2014, 10, 789-804.

[4] Pal, S.; Trivedi, D. J.; Akimov, A. V.; Aradi, B.; Frauenheim, T.; Prezhdo, O. V., Nonadiabatic Molecular Dynamics for Thousand Atom Systems: A Tight-Binding Approach toward Pyxaid. J. Chem. Theory Comput. 2016, 12, 1436-1448.

[5] Jankowska, J.; Long, R.; Prezhdo, O. V., Quantum Dynamics of Photogenerated Charge Carriers in Hybrid Perovskites: Dopants, Grain Boundaries, Electric Order, and Other Realistic Aspects. ACS Energy Lett. 2017, 2, 1588-1597.

[6] Long, R.; Fang, W. H.; Prezhdo, O. V., Strong Interaction at the Perovskite/Tio2 Interface Facilitates Ultrafast Photoinduced Charge Separation: A Nonadiabatic Molecular Dynamics Study. J. Phys. Chem. C 2017, 121, 3797-3806.

[7] Liu, J.; Prezhdo, O. V., Chlorine Doping Reduces Electron-Hole Recombination in Lead Iodide Perovskites: Time-Domain Ab Initio Analysis. J. Phys. Chem. Lett. 2015, 6, 4463-4469.

[8] Long, R.; Prezhdo, O. V., Dopants Control Electron-Hole Recombination at Perovskite-Tio2 Interfaces: Ab Initio Time-Domain Study. ACS Nano 2015, 9, 11143-11155.

[9] Long, R.; Liu, J.; Prezhdo, O. V., Unravelling the Effects of Grain Boundary and Chemical Doping on Electron-Hole Recombination in Ch3nh3pbi3 Perovskite by Time-Domain Atomistic Simulation. J. Am. Chem. Soc. 2016, 138, 3884-3890.

[10] Long, R.; Fang, W. H.; Prezhdo, O. V., Moderate Humidity Delays Electron-Hole Recombination in Hybrid Organic-Inorganic Perovskites: Time-Domain Ab Initio Simulations Rationalize Experiments. J. Phys. Chem. Lett. 2016, 7, 3215-3222.

[11] Li, W.; Liu, J.; Bai, F. Q.; Zhang, H. X.; Prezhdo, O. V., Hole Trapping by Iodine Interstitial Defects Decreases Free Carrier Losses in Perovskite Solar Cells: A Time-Domain Ab Initio Study. ACS Energy Lett. 2017, 2, 1270-1278.

[12] Jankowska, J.; Prezhdo, O. V., Ferroelectric Alignment of Organic Cations Inhibits Nonradiative Electron-Hole Recombination in Hybrid Perovskites: Ab Initio Nonadiabatic Molecular Dynamics. J. Phys. Chem. Lett. 2017, 8, 812-818.

[13] Tong, C. J.; Geng, W.; Prezhdo, O. V.; Liu, L. M., Role of Methylammonium Orientation in Ion Diffusion and Current Voltage Hysteresis in the Ch3nh3pbi3 Perovskite. ACS Energy Lett. 2017, 2, 1997-2004.

[14] Liu, L. H.; Fang, W. H.; Long, R.; Prezhdo, O. V., Lewis Base Passivation of Hybrid Halide Perovskites Slows Electron-Hole Recombination: Time-Domain Ab Lnitio Analysis. J. Phys. Chem. Lett. 2018, 9, 1164-1171.

[15] Zhang, Z. S.; Long, R.; Tokina, M. V.; Prezhdo, O. V., Interplay between Localized and Free Charge Carriers Can Explain Hot Fluorescence in the Ch3nh3pbbr3 Perovskite: Time-Domain Ab Initio Analysis. J. Am. Chem. Soc. 2017, 139, 17327-17333.

[16] He, J. L.; Fang, W. H.; Long, R.; Prezhdo, O. V., Increased Lattice Stiffness Suppresses Nonradiative Charge Recombination in Mapbl(3) Doped with Larger Cations: Time Domain Ab Initio Analysis. ACS Energy Lett. 2018, 3, 2070-2076.

[17] Tong, C. J.; Li, L. Q.; Liu, L. M.; Prezhdo, O. V., Long Carrier Lifetimes in Pbi2-Rich Perovskites Rationalized by Ab Initio Nonadiabatic Molecular Dynamics. ACS Energy Lett. 2018, 3, 1868-1874.

[18] He, J. L.; Vasenko, A. S.; Long, R.; Prezhdo, O. V., Halide Composition Controls Electron-Hole Recombination in Cesium-Lead Halide Perovskite Quantum Dots: A Time Domain Ab Lnitio Study. J. Phys. Chem. Lett. 2018, 9, 1872-1879.

[19] Li, W.; Sun, Y. Y.; Li, L. Q.; Zhou, Z. H.; Tang, J. F.; V., P. O., Control of Charge Recombination in Perovskites by Oxidation State of Halide Vacancy. J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.8b08448.

[20] Li, W.; Tang, J. F.; Casanova, D.; Prezhdo, O. V., Time-Domain Ab Initio Analysis Rationalizes the Unusual Temperature Dependence of Charge Carrier Relaxation in Lead Halide Perovskite. ACS Energy Lett. 2018, 3, 2713–2720.

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.