Crystal Symmetry and Static Electron Correlation Greatly Accelerate Nonradiative Dynamics in Lead Halide Perovskites

Abstract

Using a recently developed many-body nonadiabatic molecular dynamics (NA-MD) framework for large condensed matter systems, we study the phonon-driven nonradiative relaxation of excess electronic excitation energy in cubic and tetragonal phases of the lead halide perovskite CsPbI 3 . We find that the many-body treatment of the electronic excited states significantly changes the structure of the excited states' coupling, promotes a stronger nonadiabatic coupling of states, and ultimately accelerates the relaxation dynamics relative to the single-particle description of excited states. The acceleration of the nonadiabatic dynamics correlates with the degree of configurational mixing, which is controlled by the crystal symmetry. The higher-symmetry cubic phase of CsPbI 3 exhibits stronger configuration mixing than does the tetragonal phase and subsequently yields faster nonradiative dynamics. Overall, using a many-body treatment of excited states and accounting for decoherence dynamics are important for closing the gap between the computationally derived and experimentally measured nonradiative excitation energy relaxation rates.

Ab initio nonadiabatic molecular dynamics of charge carriers in metal halide perovskites

“…287,288 Wang et al 51,289 introduced the GFSH method to allow NA transitions involving multiple particles. The physics of Auger processes resides in carrier-carrier interactions, and therefore, such interactions should be included explicitly into NA-MD simulations, as done efficiently by Zhou et al 290 Recently, excitonic effects were introduced into NA-MD simulation, with NAC calculated using both single particle and many-body bases, as achieved in the Libra platform interfaced with CP2K, developed by Akimov and coworkers, 31,238 and by the Zhao group in the Hefei-NAMD code. 291 Time-domain ab initio simulations of Auger processes involve huge numbers of states, significantly increasing computation demands.…”

Nonadiabatic Molecular Dynamics with Extended Density Functional Tight-Binding: Application to Nanocrystals and Periodic Solids

“…Nonadiabatic molecular dynamics (NA-MD) is a powerful computational technique that can model NA processes and describe the excited-state dynamics in various materials. NA-MD simulations have been successfully utilized in predicting the photochemistry and photophysics of molecular systems − and nanoscale materials. − These simulations have been widely used to gain insights into NA processes in solar cells, − light-emitting diodes, and chemical reactions. − However, due to the highly demanding computational costs, the NA-MD simulations of solid-state and nanoscale systems are often limited to a few hundred atoms. Simulation of realistic nanostructures, comparable to those studied experimentally is still computationally expensive, primarily due to the demanding costs of the underlying electronic structure calculations and their unfavorable scalability with the system size.…”

Role of defects in ultrafast charge recombination in monolayer MoS$_2$

“…Another explanation to the fact that we obtain longer times than the observed in experiments are excitons. It is known that excitonic effects can accelerate the recombination dynamics [38,39], and MoS 2 has the well known A and B excitons. However, we would need to go beyond the one-particle picture we have used in this study to be able to capture those in a quantitative way, and it would be computationally prohibitive.…”