skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Higher-Energy Charge Transfer States Facilitate Charge Separation in Donor$-$Acceptor Molecular Dyads

Abstract

We simulate subpicosecond charge separation in two donor-acceptor molecular dyads. Charge separation dynamics is described using a quantum master equation, with parameters of the dyad Hamiltonian obtained from density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations and the rate of energy dissipation estimated from Ehrenfest-TDDFT molecular dynamics simulations. We find that higher-energy charge transfer states must be included in the dyad Hamiltonian in order to obtain agreement of charge separation rates with the experimental values. Our results show that efficient and irreversible charge separation involves both coherent electron transfer from the donor excited state to higher-energy unoccupied states on the acceptor and incoherent energy dissipation that relaxes the dyad to the lowest energy charge transfer state. The role of coherence depends on the initial excited state, with electron delocalization within Hamiltonian eigenstates found to be more important than coherence between eigenstates. We conclude that ultrafast charge separation is most likely to occur in donor-acceptor dyads possessing dense manifolds of charge transfer states at energies close to those of Frenkel excitons on the donor, with strong couplings to these states enabling partial delocalization of eigenstates over acceptor and donor.

Authors:
ORCiD logo; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1365424
Alternate Identifier(s):
OSTI ID: 1575228
Grant/Contract Number:  
AC05-06OR23100; AC02-05CH11231
Resource Type:
Published Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Name: Journal of Physical Chemistry. C Journal Volume: 121 Journal Issue: 24; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Lee, Donghyun, Forsuelo, Michael A., Kocherzhenko, Aleksey A., and Whaley, K. Birgitta. Higher-Energy Charge Transfer States Facilitate Charge Separation in Donor$-$Acceptor Molecular Dyads. United States: N. p., 2017. Web. doi:10.1021/acs.jpcc.7b03197.
Lee, Donghyun, Forsuelo, Michael A., Kocherzhenko, Aleksey A., & Whaley, K. Birgitta. Higher-Energy Charge Transfer States Facilitate Charge Separation in Donor$-$Acceptor Molecular Dyads. United States. doi:10.1021/acs.jpcc.7b03197.
Lee, Donghyun, Forsuelo, Michael A., Kocherzhenko, Aleksey A., and Whaley, K. Birgitta. Tue . "Higher-Energy Charge Transfer States Facilitate Charge Separation in Donor$-$Acceptor Molecular Dyads". United States. doi:10.1021/acs.jpcc.7b03197.
@article{osti_1365424,
title = {Higher-Energy Charge Transfer States Facilitate Charge Separation in Donor$-$Acceptor Molecular Dyads},
author = {Lee, Donghyun and Forsuelo, Michael A. and Kocherzhenko, Aleksey A. and Whaley, K. Birgitta},
abstractNote = {We simulate subpicosecond charge separation in two donor-acceptor molecular dyads. Charge separation dynamics is described using a quantum master equation, with parameters of the dyad Hamiltonian obtained from density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations and the rate of energy dissipation estimated from Ehrenfest-TDDFT molecular dynamics simulations. We find that higher-energy charge transfer states must be included in the dyad Hamiltonian in order to obtain agreement of charge separation rates with the experimental values. Our results show that efficient and irreversible charge separation involves both coherent electron transfer from the donor excited state to higher-energy unoccupied states on the acceptor and incoherent energy dissipation that relaxes the dyad to the lowest energy charge transfer state. The role of coherence depends on the initial excited state, with electron delocalization within Hamiltonian eigenstates found to be more important than coherence between eigenstates. We conclude that ultrafast charge separation is most likely to occur in donor-acceptor dyads possessing dense manifolds of charge transfer states at energies close to those of Frenkel excitons on the donor, with strong couplings to these states enabling partial delocalization of eigenstates over acceptor and donor.},
doi = {10.1021/acs.jpcc.7b03197},
journal = {Journal of Physical Chemistry. C},
number = 24,
volume = 121,
place = {United States},
year = {2017},
month = {5}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1021/acs.jpcc.7b03197

Citation Metrics:
Cited by: 3 works
Citation information provided by
Web of Science

Save / Share: