Quantum Dynamics of Exciton Transport and Dissociation in Multichromophoric Systems

Abstract

Due to the subtle interplay of site-to-site electronic couplings, exciton delocalization, nonadiabatic effects, and vibronic couplings, quantum dynamical studies are needed to elucidate the details of ultrafast photoinduced energy and charge transfer events in organic multichromophoric systems. In this vein, we review an approach that combines first-principles parameterized lattice Hamiltonians with accurate quantum dynamical simulations using advanced multiconfigurational methods. Focusing on the elementary transfer steps in organic molecular materials, we address coherent exciton migration and creation of charge transfer excitons in homopolymers, notably polythiophene-type materials representative of the poly(3-hexylthiophene) polymer, as well as exciton dissociation at polymer:fullerene heterojunctions. We emphasize the role of coherent transfer, trapping effects due to high-frequency phonon modes, and thermal activation due to low-frequency soft modes that drive a diffusive dynamics. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Quantum Dynamics of Electron–Hole Separation in Stacked Perylene Diimide-Based Self-Assembled Nanostructures

“…Notwithstanding, free carrier formation can be highly efficient. 10,21 From the above vantage point, the transition between the bound and dissociative e−h states is driven by vibronic coupling (i.e., dynamic disorder). That is, phonon modes are expected to induce multiple nonadiabatic crossing events which couple bound and dissociative e−h states.…”

“…However, in most relevant systems, excess energy does not seem to have a predominant effect, and relaxed interfacial e−h species emerge from the initial exciton dissociation. 11,21 In the present study, we carry out a full quantum dynamical analysis 22 of charge separation in mesomorphic self-assembled nanostructures composed of conjugated donor−acceptor block co-oligomers. Conjugated block copolymer photovoltaics have emerged as a route toward highly controlled heterojunction architectures.…”

Multi-layer Gaussian-based multi-configuration time-dependent Hartree (ML-GMCTDH) simulations of ultrafast charge separation in a donor–acceptor complex

“…The model in the present form is a building block for more general aggregate Hamiltonians describing the P3HT:PCBM material. [44][45][46] The model Hamiltonian as specified below is constructed from supermolecular LR-TDDFT calculations using a suitable diabatization procedure as reported in Ref. [42].…”

“…The vibronic model Hamiltonian employed in the present study is a basic example of firstprinciples parametrized lattice Hamiltonians that can be expanded to much larger system sizes [44][45][46] in order to permit a full quantum treatment of photoinduced dynamics in molecular materials. Excited-state dynamics in these systems are characterized by electronic delocalization and strong electron-phonon (vibronic) coupling, both of which require accurate quantum dynamical approaches.…”

Singlet Fission Dynamics Modulated by Molecular Configuration in Covalently Linked Pyrene Dimers, Anti- and Syn-1,2-di(Pyrenyl)Benzene

“…7,8,9,10,11 In this regard, many multi-chromophore systems have been widely used for developing highly efficient photoelectric or electrochemical devices using chromophore-chromophore interaction. 7,12,13,14,15,16 Among multi-chromophore systems, covalently linked dimers (CLDs) have attracted much attention as potential materials to provide high energy conversion efficiencies in photovoltaic devices because their excited-state relaxation dynamics, such as the excimer formation, intramolecular charge transfer (ICT), and singlet fission (SF), can be modulated by the strategic molecular design. 9,17,18,19,20 Especially the dynamics of SF, which is a conversion process from one singlet exciton into two triplet excitons, have been actively investigated with various time-resolved spectroscopies, to overcome the limit of Shockley-Queisser power conversion efficiency.…”