Dynamics of charge separation at an organic donor-acceptor interface

Sun, Zhen; Stafström, Sven

doi:10.1103/physrevb.90.115420

Cited by 26 publications

(30 citation statements)

References 23 publications

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“…To resolve question (ii), many experimental 7,8,13,14 and theoretical [15][16][17][18][19] studies have challenged the implicit assumption that the lowest CT state is involved in the process. These studies emphasized the critical role of electronically hot (energetically higher) CT states as intermediate states before the transition to CS states.…”

Section: Introductionmentioning

confidence: 99%

Origin of space-separated charges in photoexcited organic heterojunctions on ultrafast time scales

Janković

Vukmirović

2017

Phys. Rev. B

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We present a detailed investigation of ultrafast (subpicosecond) exciton dynamics in the lattice model of a donor/acceptor heterojunction. Exciton generation by means of a photoexcitation, exciton dissociation, and further charge separation are treated on equal footing. The experimentally observed presence of space-separated charges at 100 fs after the photoexcitation is usually attributed to ultrafast transitions from excitons in the donor to charge transfer and charge separated states. Here, we show, however, that the space-separated charges appearing on 100-fs time scales are predominantly directly optically generated. Our theoretical insights into the ultrafast pump-probe spectroscopy challenge usual interpretations of pump-probe spectra in terms of ultrafast population transfer from donor excitons to space-separated charges.

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Section: Introductionmentioning

confidence: 99%

Origin of space-separated charges in photoexcited organic heterojunctions on ultrafast time scales

Janković

Vukmirović

2017

Phys. Rev. B

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“…Permittivity of a dielectric medium is close to the reported experimental value 29,30 and τ is an intermediate value encountered in computational studies. 7,14,15,23,27,31,32 Charge is initially localized on the second nearest site to the interface (|ψ(t=0) = |2 ), which corresponds to the electron-hole separation of 2.6 nm.…”

Section: Purely Electronic Dynamicsmentioning

confidence: 99%

“…[13][14][15][16][17][18][19][20][21][22] For example, Tamura and Burghardt 13 attributed fast CS to the two main factors, (i) electron delocalization within the fullerene condensate and (ii) the role of vibronically hot CT states, by carrying out a combined approach of electronic structure calculations and quantum dynamical analysis. Sun To obtain a complete description of charge dynamics it is therefore important to model the charge dynamics of both processes, "low-energy CT to CS states" and "CS to low-energy CT states", which would occur on two different timescales.…”

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confidence: 99%

Charge Dynamics in Organic Photovoltaic Materials: Interplay between Quantum Diffusion and Quantum Relaxation

2015

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Original citation:Lee, Myeong H., Aragó, Juan and Troisi, Alessandro. (2015) Charge dynamics in organic photovoltaic materials : interplay between quantum diffusion and quantum relaxation. The Journal of Physical Chemistry Part C, 119 (27). pp. 14989-14998. Permanent WRAP url:http://wrap.warwick.ac.uk/73402 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry Part C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work, see http://dx.doi.org/10.1021/acs.jpcc.5b03989 A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. For more information, please contact the WRAP This paper discusses the mechanism of generation of free charges in organic photovoltaic cells (OPV) from electrostatically bound electron-hole pairs. The efficiency of this process is explained when interfacial charge-transfer (CT) states are generated by direct optical excitation. We used semiclassical quantum dynamics at short timescale (∼100 fs) and Redfield theory at relatively long timescale (∼10-100 ps) to cover both the process of dissociation and the relaxation to the lowest energy state. Our calculations suggest that a CT state with an intermediate electron-hole separation can evolve into a charge-separated (CS) state on ultrafast timescales (∼100 fs) as a result of quantum diffusion. On long timescales, however, the CS states ultimately relax to the low-energy CT states due to the interaction with the thermal bath, indicating that the yield of free charge carrier generation is determined by the interplay between ultrafast charge separation, due to quantum diffusion, and the much slower quantum relaxation process.

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“…[19] to solve the coupled differential Eqs. (5) and (6), i.e., the MCTDHF method which together with the Runge-Kutta method of order eight with step-size control, has been shown to be an effective approach for investigating the dynamics of conjugated polymers [24][25][26]. The parameters used in this paper are taken to be those for cis-polyacetylene, i.e., t 0 ¼ 2:1 eV; t e ¼ 0:05 eV, a ¼ 3:2 eV/Å, K ¼ 21:0 eV/Å 2 , These parameters reproduce well the band gap diagram of the polyacetylene.…”

Section: Model and Methodsmentioning

confidence: 99%