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  • 1.
    Jakobsson, Mattias
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Monte Carlo Studies of Charge Transport Below the Mobility Edge2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Charge transport below the mobility edge, where the charge carriers are hopping between localized electronic states, is the dominant charge transport mechanism in a wide range of disordered materials. This type of incoherent charge transport is fundamentally different from the coherent charge transport in ordered crystalline materials. With the advent of organic electronics, where small organic molecules or polymers replace traditional inorganic semiconductors, the interest for this type of hopping charge transport has increased greatly. The work documented in this thesis has been dedicated to the understanding of this charge transport below the mobility edge.

    While analytical solutions exist for the transport coefficients in several simplified models of hopping charge transport, no analytical solutions yet exist that can describe these coefficients in most real systems. Due to this, Monte Carlo simulations, sometimes described as ideal experiments performed by computers, have been extensively used in this work.

    A particularly interesting organic system is deoxyribonucleic acid (DNA). Besides its overwhelming biological importance, DNA’s recognition and self-assembly properties have made it an interesting candidate as a molecular wire in the field of molecular electronics. In this work, it is shown that incoherent hopping and the Nobel prize-awarded Marcus theory can be used to describe the results of experimental studies on DNA. Furthermore, using this experimentally verified model, predictions of the bottlenecks in DNA conduction are made.

    The second part of this work concerns charge transport in conjugated polymers, the flagship of organic materials with respect to processability. It is shown that polaronic effects, accounted for by Marcus theory but not by the more commonly used Miller-Abrahams theory, can be very important for the charge transport process. A significant step is also taken in the modeling of the off-diagonal disorder in organic systems. By taking the geometry of the system from large-scale molecular dynamics simulations and calculating the electronic transfer integrals using Mulliken theory, the off-diagonal disorder is for the first time modeled directly from theory without the need for an assumed parametric random distribution.

    Delarbeten
    1. A Monte Carlo study of charge transfer in DNA
    Öppna denna publikation i ny flik eller fönster >>A Monte Carlo study of charge transfer in DNA
    2008 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 129, nr 12, s. 125102-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A model describing charge (hole) transport in DNA has been developed. The individual charge transfer steps in the transport process are described by Marcus theory modified to account for electron delocalization over adjacent identical nucleobases. Such a modification, as well as introducing a distance dependence in the reorganization energy, is necessary in order to reach an agreement with the observed transfer rates in well defined model systems to DNA. Using previously published results as a reference for the reorganization energy and with the delocalization described within the Hückel model we obtain an excellent agreement with experimental data.

    Nyckelord
    biology computing, charge exchange, DNA, hole mobility, molecular biophysics, Monte Carlo methods
    Nationell ämneskategori
    Fysik
    Identifikatorer
    urn:nbn:se:liu:diva-15177 (URN)10.1063/1.2981803 (DOI)
    Anmärkning
    Original publication: Mattias Jakobsson and Sven Stafström, A Monte Carlo study of charge transfer in DNA, 2008, Journal of Chemical Physics, (129), 125102.http://dx.doi.org/10.1063/1.2981803. Copyright: American Institute of Physics, http://www.aip.org/ Tillgänglig från: 2008-10-22 Skapad: 2008-10-22 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    2. Hole mobility and transport mechanisms in lambda-DNA
    Öppna denna publikation i ny flik eller fönster >>Hole mobility and transport mechanisms in lambda-DNA
    2009 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, nr 15, s. 155102-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We have performed a study of charge transport in lambda-DNA using a recently developed model based on Marcus theory and dynamic Monte Carlo simulations. The model accounts for charge delocalization over multiple adjacent identical nucleobases. Such delocalized states are found to act as traps for charge transport and therefore have a negative impact on the charge carrier (hole) mobility. Both the electric field and temperature dependence of the mobility in lambda-DNA is reported in this paper. Furthermore, the detailed information produced by the simulation allow us to plot the progress of a hole propagating through the DNA sequence and this is used to identify the bottlenecks that limits the charge transport process.

    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-51773 (URN)10.1063/1.3244677 (DOI)
    Tillgänglig från: 2009-11-18 Skapad: 2009-11-17 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
    3. Polaron effects and electric field dependence of the charge carrier mobility in conjugated polymers
    Öppna denna publikation i ny flik eller fönster >>Polaron effects and electric field dependence of the charge carrier mobility in conjugated polymers
    2011 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, nr 13, s. 134902-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Charge transport in conjugated polymers has been investigated using Monte Carlo simulations implemented on top of the Marcus theory for donor-acceptor transition rates. In particular, polaron effects and the dependency of the mobility on the temperature and the applied electric field have been studied. The conclusions are that while the qualitative temperature dependence is similar to that predicted by Miller-Abrahams theory in the Gaussian disorder model (GDM), the electric field dependence is characterized by a crossover into the Marcus inverted region, not present in the GDM. Furthermore, available analytical approximations to describe the electric field dependence of the mobility in Marcus theory fail to fit the simulation data and hence cannot be used to directly draw conclusions about the importance of polaron effects for charge transport in conjugated polymers.

    Ort, förlag, år, upplaga, sidor
    American Institute of Physics (AIP), 2011
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-71638 (URN)10.1063/1.3644931 (DOI)000295625400067 ()
    Anmärkning
    Funding Agencies|Swedish Research Council (VR)||MATTER Network||Tillgänglig från: 2011-10-27 Skapad: 2011-10-27 Senast uppdaterad: 2017-12-08
    4. Monte Carlo simulations of charge transport in organic systems with true off-diagonal disorder
    Öppna denna publikation i ny flik eller fönster >>Monte Carlo simulations of charge transport in organic systems with true off-diagonal disorder
    2012 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, nr 11Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this work, a novel method to model off-diagonal disorder in organic materials has been developed. The off-diagonal disorder is taken directly from the geometry of the system, which includes both a distance and an orientational dependence on the constituent molecules, and does not rely on a parametric random distribution. To study this method, a system is generated by running molecular dynamics simulations on phenylene-vinylene oligomers packed into boxes. The impact of the model is then investigated by means of Monte Carlo simulations of the charge transport in these boxes and a comparison is made to the commonly used model of off-diagonal disorder, where only the distance dependence is properly accounted for. It is shown that this new model has a significant impact on the charge transport, while still being compliant with previously published and confirmed results.

    Ort, förlag, år, upplaga, sidor
    American Institute of Physics (AIP), 2012
    Nyckelord
    Monte Carlo simulation, molecular dynamics, charge transport, organic materials, conjugated polymers, PPV, off-diagonal disorder
    Nationell ämneskategori
    Annan fysik
    Identifikatorer
    urn:nbn:se:liu:diva-74319 (URN)10.1063/1.4748796 (DOI)000309100600043 ()
    Anmärkning

    funding agencies|Swedish Research Council (VR)||MATTER Network||SERC||

    Tillgänglig från: 2012-01-24 Skapad: 2012-01-24 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
  • 2.
    Jakobsson, Mattias
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    A Monte Carlo study of charge transfer in DNA2008Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 129, nr 12, s. 125102-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A model describing charge (hole) transport in DNA has been developed. The individual charge transfer steps in the transport process are described by Marcus theory modified to account for electron delocalization over adjacent identical nucleobases. Such a modification, as well as introducing a distance dependence in the reorganization energy, is necessary in order to reach an agreement with the observed transfer rates in well defined model systems to DNA. Using previously published results as a reference for the reorganization energy and with the delocalization described within the Hückel model we obtain an excellent agreement with experimental data.

  • 3.
    Jakobsson, Mattias
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Linares, Mathieu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Monte Carlo simulations of charge transport in organic systems with true off-diagonal disorder2012Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, nr 11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a novel method to model off-diagonal disorder in organic materials has been developed. The off-diagonal disorder is taken directly from the geometry of the system, which includes both a distance and an orientational dependence on the constituent molecules, and does not rely on a parametric random distribution. To study this method, a system is generated by running molecular dynamics simulations on phenylene-vinylene oligomers packed into boxes. The impact of the model is then investigated by means of Monte Carlo simulations of the charge transport in these boxes and a comparison is made to the commonly used model of off-diagonal disorder, where only the distance dependence is properly accounted for. It is shown that this new model has a significant impact on the charge transport, while still being compliant with previously published and confirmed results.

  • 4.
    Jakobsson, Mattias
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Hole mobility and transport mechanisms in lambda-DNA2009Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, nr 15, s. 155102-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have performed a study of charge transport in lambda-DNA using a recently developed model based on Marcus theory and dynamic Monte Carlo simulations. The model accounts for charge delocalization over multiple adjacent identical nucleobases. Such delocalized states are found to act as traps for charge transport and therefore have a negative impact on the charge carrier (hole) mobility. Both the electric field and temperature dependence of the mobility in lambda-DNA is reported in this paper. Furthermore, the detailed information produced by the simulation allow us to plot the progress of a hole propagating through the DNA sequence and this is used to identify the bottlenecks that limits the charge transport process.

  • 5.
    Jakobsson, Mattias
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Polaron effects and electric field dependence of the charge carrier mobility in conjugated polymers2011Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, nr 13, s. 134902-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Charge transport in conjugated polymers has been investigated using Monte Carlo simulations implemented on top of the Marcus theory for donor-acceptor transition rates. In particular, polaron effects and the dependency of the mobility on the temperature and the applied electric field have been studied. The conclusions are that while the qualitative temperature dependence is similar to that predicted by Miller-Abrahams theory in the Gaussian disorder model (GDM), the electric field dependence is characterized by a crossover into the Marcus inverted region, not present in the GDM. Furthermore, available analytical approximations to describe the electric field dependence of the mobility in Marcus theory fail to fit the simulation data and hence cannot be used to directly draw conclusions about the importance of polaron effects for charge transport in conjugated polymers.

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