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Electronic structure calculations of the phenalenyl-based neutral radical conductor bis(9-cyclohexylimino-1-phenalenyl) boron
Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics.
2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 15Article in journal (Refereed) Published
Abstract [en]

The solid state of free radicals of bis(9-cyclohexylimino-1-oxyphenalenyl) boron is one of few neutral molecular systems which exhibit high conductivity at room temperature. The system is crystalline but highly anistotropic. We have performed band structure calculations based on the density functional theory on this system. It is evident from these studies that the system is quasi-one-dimensional with strong intermolecular interactions along one crystal direction. The bandwidth is 0.424 eV along this direction as compared to 0.055 eV perpendicular to it. Despite the quasi-one-dimensional character of the system, no signature of a Peierls distortion towards a dimerized state is observed. We argue that this is due to the fact that the Fermi energy lies slightly below the middle of the conduction band. In this case the electronic driving force for the distortion to occur is weakened and overcome by the restoring force of the lattice. Also the optical properties of the system have been investigated and the origin of the low lying excitations in the system has been clarified.

Place, publisher, year, edition, pages
2006. Vol. 74, no 15
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-50104DOI: 10.1103/PhysRevB.74.155111OAI: oai:DiVA.org:liu-50104DiVA: diva2:271000
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
In thesis
1. Molecular electronics : a theoretical study of electronic structure in molecular crystals and surfaces
Open this publication in new window or tab >>Molecular electronics : a theoretical study of electronic structure in molecular crystals and surfaces
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

  

This thesis deals with theoretical studies of the electronic structures of molecules in organic crystal and molecules adsorbed on metal surfaces. Both studies with first principle calculations and classical mechanics were performed. The materials include pentacene and bis(9-cyclohexylimino-l-oxyphenalenyl)boron and the

Tetrakis( dimethylamino )ethylene (TDAE) molecule chemisorbed on a gold surface. Molecular crystals of pentacene are reported to have the highest field-effect mobility values for organic thin film field effect transistors, and are therefore suitable to be the active material in such devices. The increase in conductivity obtained experimentally by doping with alkali metals showed great promise, and we therefore performed calculations on pentacene crystals doped with potassium. Phase transitions occured upon doping, and the herringbone arrangement of the pristine pentacene molecules relaxes towards a 1r stacked structure. Charge transfer between the crystal and the potassium occurs, which shifts the Fermi level into the lowest unoccupied molecular orbitals bands and turns the crystal metallic. The study of bis(9-cyclohexylimino-l-oxyphenalenyl)boron, a biphenalenyl based neutral radical, was performed in order to investigate the electronic properties since experimental studies had shown simultaneous electrical, optical and magnetical bistability. The system is quasi one-dimensional, as shown from band structure calculations.. The injection of charge carriers from metals to organic semiconductors is one of the most central processes when it comes to the performance of organic devices. The interface between the metal and the semiconductor is one of the device parameters that will significantly influence the device performance. The addition of a molecular layer on the interface can, by the introduction of a dipole, reduce the energy barrier for charge injection. ·we found that a molecular layer of TDAE deposited on a gold surface results in a charge transfer from the molecule to the surface which reduced the charge injection barrier by as much as 2.4 eV.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2007. 34 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1315
Series
LIU-TEK-LIC, 24
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-38440 (URN)44368 (Local ID)978-91-85831-76-0 (ISBN)44368 (Archive number)44368 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-11-14

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Böhlin, JohanHansson, AndersStafström, Sven

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