Time-Domain Modeling of Excited State Dynamics in Halide Perovskites
Oleg Prezhdo a
a Chemistry, University of Southern California, 3620 McClintock Ave, LA, CA, United States
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Invited Speaker, Oleg Prezhdo, presentation 014
DOI: https://doi.org/10.29363/nanoge.hopv.2019.014
Publication date: 11th February 2019

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

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