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  • 1.
    Mahani, Mohammad Reza
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Mirsakiyeva, Amina
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University, Sweden.
    Breakdown of Polarons in Conducting Polymers at Device Field Strengths2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 19, p. 10317-10324Article in journal (Refereed)
    Abstract [en]

    Conducting polymers have become standard engineering materials used in many electronic devices. Despite this, there is a lack of understanding of the microscopic origin of the conducting properties, especially at realistic device field strengths. We present simulations of doped poly(p-phenylene) (PPP) using a Su-Schrieffer-Heeger (SSH) tight-binding model, with the electric field included in the Hamiltonian through a time-dependent vector potential via Peierls substitution of the phase factor. We find that polarons typically break down within less than a picosecond after the field has been switched on, already for electric fields as low as around 1.6 mV/angstrom. This is a field strength common in many flexible organic electronic devices. Our results challenge the relevance of the polaron as charge carrier in conducting polymers for a wide range of applications.

  • 2.
    Mahani, Mohammad Reza
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Mirsakiyeva, Amina
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Department of Physics and Astronomy, Materials Theory Division, Uppsala University,.
    Charge transport via polarons in doped poly(p-phenylene) with impurityManuscript (preprint) (Other academic)
    Abstract [en]

    Polaron charge transport in doped poly(p-phenylene), PPP, in the presence of magnetic and nonmagnetic impurities and an electric field, is studied using the Su-Schrieffer-Heeger (SSH) tight-binding model. In our approach, the electric field is included in the Hamiltonian through the time-dependent vector potential via Peierls substitution of the phase factor. We describe the dynamics of the polarons and identify three distinct regimes: transmission, reflection, and trapping of polarons at the impurity site. The strength of the electric field as well as the impurity potential determine the outcome ofthe scattering.

  • 3.
    Mirsakiyeva, Amina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Electronic and optical properties of conducting polymers from quantum mechanical computations2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

        Conductive polymers are also known as "organic metals" due to their semiconducting properties. They are found in a wide range of applications in the field of organic electronics. However, the growing number of experimental works is not widely supported with theoretical calculations. Hence, the field of conductive polymers is experiencing lack of understanding of mechanisms occurring in the polymers. In this PhD thesis, the aim is to increase understanding of conductive polymers by performing theoretical calculations.       

    The polymers poly(3,4-ethylenedioxythiophene) (PEDOT) together with its selenium (PEDOS) and tellurium (PEDOTe) derivatives, poly(p-phenylene) (PPP) and naphthobischalcogenadiazoles (NXz) were studied. Several computational methods were applied for analysis of mentioned structures, including density functional theory (DFT), tight-binding modelling (TB), and Car-Parrinello molecular dynamics (CPMD) calculations. The combination of CPMD and DFT calculations was applied to investigate the PEDOT, PEDOS and PEDOTe. The polymers were studied using four different functionals in order to investigate the full picture of structural changes, electronic and optical properties. Temperature effects were studied using molecular dynamics simulations. Wide statistics for structural and molecular orbitals analysis were collected.        

    The TB method was employed for PPP. The formation and motion of the excitations, polarons and bipolarons, along the polymer backbone was investigated in presence of electric and magnetic fields. The influence of non-magnetic and magnetic impurities was determined.       

    The extended π-conjugated structures of NXz were computed using B3LYP and ωB97XD functionals in combination with the 6-31+G(d) basis set. Here, the structural changes caused by polaron formation were analyzed. The combined analysis of densities of states and absorption spectra was used for understanding of the charge transition.

  • 4.
    Mirsakiyeva, Amina
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Quantum Mechanical Calculations of Thermoelectrical Polymers and Organic Molecules2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The subject of the present licentiate thesis is density functional theorybased electronic structure calculations of organic thermoelectric materials and novel organic molecules. We used the Car-Parrinello molecular dynamics method in order to investigate the electronic structure of “green energy” and “greenchemistry” compounds.

    First, we have investigated the electronic structure of the poly(3,4-ethylene-dioxythiophene) (PEDOT) and its derivatives - the best studied and successfully implemented by industry organic thermoelectric material. Its transparency, low toxicity and high stability in the oxidized state are combined withan ability to produce electrical current when applying a temperature gradient. This makes PEDOT a perfect “organic metal” and a first candidate for organic thermoelectrogenerators - devices that can produce “green energy” from a temperature difference. The average structures found in these quantum dynamical simulations agree well with earlier static electronic structure studies. The energy gap of two, four and six unit oligomers of PEDOT was calculated and was found to lie in the range of previous theoretical studies. We have also calculatedthe point-charge distributions along the polymer backbone in order to investigate the polaron formed by doping agents of PEDOT. Our analysis allowed us to predict possible localization of the charge in the center of the polymer chain. However, further calculations of the twelve unit PEDOT and its selenium and tellurium derivatives will provide more information. First-principles calculations for the tellurium derivative of PEDOT are here presented for the first time.

    The second part of our investigation concerns theoretical calculations of novel piperidine-containing acetylene glycols. These molecules were newly synthesized by our experimental collaborators and are expected to provideplant growth stimulation properties, the same as its diacetylene analogs. We performed quantum mechanical calculations of four compounds, presented ananalysis of the highest occupied and lowest unoccupied molecular orbitals and collected detailed information on point-charges for further parametrization of novel molecules for future computational studies. According to these results, the low production yield found in the experiments cannot be attributed to chemical instability in these novel compounds.

  • 5.
    Mirsakiyeva, Amina
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Botkina, D.
    Elgammal, Karim
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Ten, Assel
    Hugosson, Håkan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University.
    Yu, Valentina
    Experimental and ab initio studies of the novel piperidine-containing acetylene glycolsManuscript (preprint) (Other academic)
  • 6.
    Mirsakiyeva, Amina
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre. Kazakh-British Technical University, Kazakhstan.
    Botkina, Darya
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering. Institute of Chemical Sciences, Kazakhstan.
    Elgammal, Karim
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Ten, Assel
    Hugosson, Håkan W.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University, Sweden.
    Yu, Valentina
    Experimental and density functional theory studies of some novel piperidine-containing acetylene glycols2016In: ARKIVOC, ISSN 1551-7004, E-ISSN 1551-7012, p. 86-99Article in journal (Refereed)
    Abstract [en]

    Synthesis routes of novel piperidine-containing acetylenes are presented. The new molecules are expected to exhibit plant growth stimulation properties. In particular, the yield in a situation of drought is expected to increase. Our synthesis makes use of the Favorskii reaction between cyclohexanone/piperidone and triple-bond containing alcohols. The structures of the obtained molecules were determined using nuclear magnetic resonance (NMR). The electronic structure and geometries of the molecules were studied theoretically using first-principles calculations based on density functional theory. The calculated geometries agree very well with the experimentally determined ones, and also allow us to determine bond lengths, angles and charge distributions inside the molecules.

  • 7.
    Mirsakiyeva, Amina
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Hugosson, Håkan W.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Univ Gävle, Sweden.
    Crispin, Xavier
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala Univ, Sweden.
    Quantum Molecular Dynamical Calculations of PEDOT 12-Oligomer and its Selenium and Tellurium Derivatives2017In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 46, no 5, p. 3071-3075Article in journal (Refereed)
    Abstract [en]

    We present simulation results, computed with the Car-Parrinello molecular dynamics method, at zero and ambient temperature (300 K) for poly(3,4-ethylenedioxythiophene) [PEDOT] and its selenium and tellurium derivatives PEDOS and PEDOTe, represented as 12-oligomer chains. In particular, we focus on structural parameters such as the dihedral rotation angle distribution, as well as how the charge distribution is affected by temperature. We find that for PEDOT, the dihedral angle distribution shows two distinct local maxima whereas for PEDOS and PEDOTe, the distributions only have one clear maximum. The twisting stiffness at ambient temperature appears to be larger the lighter the heteroatom (S, Se, Te) is, in contrast to the case at 0 K. As regards point charge distributions, they suggest that aromaticity increases with temperature, and also that aromaticity becomes more pronounced the lighter the heteroatom is, both at 0 K and ambient temperature. Our results agree well with previous results, where available. The bond lengths are consistent with substantial aromatic character both at 0 K and at ambient temperature. Our calculations also reproduce the expected trend of diminishing gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital with increasing atomic number of the heteroatom.

  • 8.
    Mirsakiyeva, Amina
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Hugosson, Håkan W.
    Linares, Mathieu
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Applied Physics. 5)Department of Physics and Astronomy, Materials Theory Division, Uppsala University.
    Temperature dependence of band gaps and conformational disorder in PEDOT and its selenium and tellurium derivatives: density functional calculations2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690Article in journal (Refereed)
    Abstract [en]

    The conducting polymer poly(3,4-ethylenedioxythiophene), or PEDOT, is an attractive material for flexibleelectronics. We present combined molecular dynamics and quantum chemical calculations, based on den-sity functional theory, of EDOT oligomers and isoelectronic selenium and tellurium derivatives (EDOS andEDOTe) to address the effect of temperature on the geometrical and electronic properties of these systems.With finite size scaling, we also extrapolate our results to the infinite polymers, i.e. PEDOT, PEDOS and PEDOTe. Our computations indicate that the most favourable oligomer conformations at finite temperature are conformations around the flat trans-conformation and a non-flat conformation around 45 from the cis-conformation. Also, the dihedral stiffness increases with the atomic number of the heteroatom. We find excellent agreement with experimentally measured gaps for PEDOT and PEDOS. For PEDOT, the gap does not increase with temperature where as this is the case for its derivatives. The conformational disorder as well as the choice of basis set both significantly affect the calculated gaps.

  • 9.
    Mirsakiyeva, Amina
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Linares, Mathieu
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Department of Physics and Astronomy, Materials Theory Division, Uppsala University,.
    Optical properties of Naphthobischalcogenadiazoles from density functional perspectiveManuscript (preprint) (Other academic)
    Abstract [en]

    In the present work the density functional calculations of two naphthobischalcogenadiazole (NXz) oligomers are shown. The oxygen- and sulphur-containing NXz trimers were optimized in a form of a neutral oligomer and a radical cation in order to investigate structural changes resulting from the polaron formation. The influence of polaron on band gaps is determined and supported with densities of states analysis together with absorption spectra. This manuscript used B3LYP and ωB97XD functionals in combination with 6-31+G(d) basis set.

  • 10.
    Mirsakiyeva, Amina
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Linares, Mathieu
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Department of Physics and Astronomy, Materials Theory Division, Uppsala University,.
    Polaron formation and optical absorption in PEDOT and its selenium and tellurium derivatives: density functional calculationsManuscript (preprint) (Other academic)
    Abstract [en]

    We present a density functional theory (DFT) study on polaron formation and optical properties of PEDOT and its selenium and tellurium derivatives. Comparing a number of combinations of basis set and approximations to the exchange-correlation functional, we find that the ωB97XD functional is an overall good choice giving well-localized polarons and optical spectra in good agreement with experiment. This functional has the correct long-range  asymptotic behavior, and also includes some short-range Hartree-Fock exchange. Despite the  long-range Hartree-Fock exchange part present in this functional, the spin contamination remains relatively limited and it also stably produces results that are virtually independent of the basis set used.

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