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Charge Separation in Donor-C60 Complexes with Real-Time Green Functions : The Importance of Nonlocal Correlations

Boström, Emil Viñas LU ; Mikkelsen, Anders LU ; Verdozzi, Claudio LU ; Perfetto, Enrico and Stefanucci, Gianluca LU (2018) In Nano Letters 18(2). p.785-792
Abstract

We use the nonequilibrium Green function (NEGF) method to perform real-time simulations of the ultrafast electron dynamics of photoexcited donor-C60 complexes modeled by a Pariser-Parr-Pople Hamiltonian. The NEGF results are compared to mean-field Hartree-Fock (HF) calculations to disentangle the role of correlations. Initial benchmarking against numerically highly accurate time-dependent density matrix renormalization group calculations verifies the accuracy of NEGF. We then find that charge-transfer (CT) excitons partially decay into charge separated (CS) states if dynamical nonlocal correlation corrections are included. This CS process occurs in ∼10 fs after photoexcitation. In contrast, the probability of exciton... (More)

We use the nonequilibrium Green function (NEGF) method to perform real-time simulations of the ultrafast electron dynamics of photoexcited donor-C60 complexes modeled by a Pariser-Parr-Pople Hamiltonian. The NEGF results are compared to mean-field Hartree-Fock (HF) calculations to disentangle the role of correlations. Initial benchmarking against numerically highly accurate time-dependent density matrix renormalization group calculations verifies the accuracy of NEGF. We then find that charge-transfer (CT) excitons partially decay into charge separated (CS) states if dynamical nonlocal correlation corrections are included. This CS process occurs in ∼10 fs after photoexcitation. In contrast, the probability of exciton recombination is almost 100% in HF simulations. These results are largely unaffected by nuclear vibrations; the latter become however essential whenever level misalignment hinders the CT process. The robust nature of our findings indicates that ultrafast CS driven by correlation-induced decoherence may occur in many organic nanoscale systems, but it will only be correctly predicted by theoretical treatments that include time-nonlocal correlations.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Charge transfer, donor-acceptor complex, nonequilibrium Green functions, real-time simulations, ultrafast dynamics
in
Nano Letters
volume
18
issue
2
pages
8 pages
publisher
The American Chemical Society
external identifiers
  • scopus:85042127647
ISSN
1530-6984
DOI
10.1021/acs.nanolett.7b03995
language
English
LU publication?
yes
id
5fb100bf-c5b7-4c60-9dfd-540584deed9a
date added to LUP
2018-03-06 11:56:25
date last changed
2018-06-17 05:30:54
@article{5fb100bf-c5b7-4c60-9dfd-540584deed9a,
  abstract     = {<p>We use the nonequilibrium Green function (NEGF) method to perform real-time simulations of the ultrafast electron dynamics of photoexcited donor-C<sub>60</sub> complexes modeled by a Pariser-Parr-Pople Hamiltonian. The NEGF results are compared to mean-field Hartree-Fock (HF) calculations to disentangle the role of correlations. Initial benchmarking against numerically highly accurate time-dependent density matrix renormalization group calculations verifies the accuracy of NEGF. We then find that charge-transfer (CT) excitons partially decay into charge separated (CS) states if dynamical nonlocal correlation corrections are included. This CS process occurs in ∼10 fs after photoexcitation. In contrast, the probability of exciton recombination is almost 100% in HF simulations. These results are largely unaffected by nuclear vibrations; the latter become however essential whenever level misalignment hinders the CT process. The robust nature of our findings indicates that ultrafast CS driven by correlation-induced decoherence may occur in many organic nanoscale systems, but it will only be correctly predicted by theoretical treatments that include time-nonlocal correlations.</p>},
  author       = {Boström, Emil Viñas and Mikkelsen, Anders and Verdozzi, Claudio and Perfetto, Enrico and Stefanucci, Gianluca},
  issn         = {1530-6984},
  keyword      = {Charge transfer,donor-acceptor complex,nonequilibrium Green functions,real-time simulations,ultrafast dynamics},
  language     = {eng},
  month        = {02},
  number       = {2},
  pages        = {785--792},
  publisher    = {The American Chemical Society},
  series       = {Nano Letters},
  title        = {Charge Separation in Donor-C<sub>60</sub> Complexes with Real-Time Green Functions : The Importance of Nonlocal Correlations},
  url          = {http://dx.doi.org/10.1021/acs.nanolett.7b03995},
  volume       = {18},
  year         = {2018},
}