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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
; ; ; and
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 (ACS)
external identifiers
  • scopus:85042127647
  • pmid:29266952
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
2025-10-14 11:14:44
@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}},
  keywords     = {{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 (ACS)}},
  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}},
  doi          = {{10.1021/acs.nanolett.7b03995}},
  volume       = {{18}},
  year         = {{2018}},
}