Xiang Sun
Theoretical Approaches To Photoinduced Charge Transfer in The Condensed Phase
Taylor Auditorium, Frick Chemistry Lab B02
Host: Joseph Subotnik
Photoinduced charge and energy transfer in condensed-phase systems plays a crucial role in solar energy conversion, particularly in organic photovoltaic (OPV) materials. This talk will introduce newly developed computational frameworks that integrate three levels of description: rate constants, time-dependent rates, and nonadiabatic dynamics. At the core of these approaches is the linearized semiclassical (LSC) method, which enables the study of electronic transitions in complex many-body systems at an all-atom resolution. For example, we compute time-dependent charge transfer rates using nonequilibrium Fermi’s golden rule and LSC-based hierarchical approximations, culminating in the Instantaneous Marcus Theory (IMT). IMT effectively captures transient rates driven by structural relaxation and has been applied to a model OPV system: a carotenoid-porphyrin-fullerene triad dissolved in tetrahydrofuran solvent. Here, we observed a significant enhancement in transient rates caused by nonequilibrium solvent relaxation. Additionally, we introduce the multi-state harmonic (MSH) model, a method for constructing effective Hamiltonians for multi-state systems directly from all-atom data. The MSH model accounts for the heterogeneous environment’s influence on multiple electronic states by consistently treating reorganization energies across state pairs. Its nonadiabatic dynamics closely align with those obtained from full all-atom Hamiltonians, validated using various semiclassical methods. Together, these multiscale quantum dynamics methods, combining all-atom and effective Hamiltonian approaches, provide a robust and versatile framework for studying charge and energy transfer processes in complex condensed-phase systems.