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Breakdown of Polarons in Conducting Polymers at Device Field Strengths
KTH, School of Engineering Sciences (SCI), Applied Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University, Sweden.
2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 19, 10317-10324 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017. Vol. 121, no 19, 10317-10324 p.
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-209310DOI: 10.1021/acs.jpcc.7b02368ISI: 000402024200008Scopus ID: 2-s2.0-85020647285OAI: oai:DiVA.org:kth-209310DiVA: diva2:1111519
Funder
Swedish Research CouncilThe Royal Swedish Academy of SciencesKnut and Alice Wallenberg FoundationCarl Tryggers foundation Swedish Energy AgencySwedish Foundation for Strategic Research
Note

QC 20170619

Available from: 2017-06-19 Created: 2017-06-19 Last updated: 2017-09-28Bibliographically approved
In thesis
1. Electronic and optical properties of conducting polymers from quantum mechanical computations
Open this publication in new window or tab >>Electronic and optical properties of conducting polymers from quantum mechanical computations
2017 (English)Doctoral 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.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 54 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2017:59
Keyword
density functional theory, DFT, Car-Parrinello molecular dynamics, CPMD, tigh-binding, poly(3, 4-ethylenedioxythiophene), PEDOT, selenium, PEDOS, tellurium, PEDOTe, poly(p-phenylene), poly(para-phenylene), poly(1, 4-phenylene), naphthobischalcogenadiazoles
National Category
Condensed Matter Physics Polymer Chemistry
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-214979 (URN)978-91-7729-529-7 (ISBN)
Public defence
2017-10-27, Sal C, Kistagången 16, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20170928

Available from: 2017-09-28 Created: 2017-09-27 Last updated: 2017-09-28Bibliographically approved

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