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Ab Initio Study of Switching Properties of Photochromic Dithienylethene Molecules
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.ORCID iD: 0000-0001-7788-6127
2006 (English)In: Materials Research Society Symposium Proceedings, ISSN 0272-9172, Vol. 965, 296-300 p.Article in journal (Refereed) Published
Abstract [en]

We report an ab initio study of a photochromic dithienylethene derivative. The mechanisms for switching between open and closed conformations are investigated based on total energy calculations for the ground and first excited state. An explanation for the central ring closure based on relaxation of the excited state is presented.

Place, publisher, year, edition, pages
2006. Vol. 965, 296-300 p.
Keyword [en]
Derivatives, Excited states, Molecular structure, Dithienylethene molecules, Switching properties
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-8604Scopus ID: 2-s2.0-40949126958OAI: oai:DiVA.org:kth-8604DiVA: diva2:13971
Note
QC 20101119Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2010-11-19Bibliographically approved
In thesis
1. Quantum transport in photoswitching molecules: An investigation based on ab initio calculations and Non Equilibrium Green Function theory
Open this publication in new window or tab >>Quantum transport in photoswitching molecules: An investigation based on ab initio calculations and Non Equilibrium Green Function theory
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Molecular electronics is envisioned as a possible next step in device miniaturization. It is usually taken to mean the design and manufacturing of electronic devices and applications where organic molecules work as the fundamental functioning unit. It involves the easurement and manipulation of electronic response and transport in molecules attached to conducting leads. Organic molecules have the advantages over conventional solid state electronics of inherent small sizes, endless chemical diversity and ambient temperature low cost manufacturing.

In this thesis we investigate the switching and conducting properties of photochromic dithienylethene derivatives. Such molecules change their conformation in solution when acted upon by light. Photochromic molecules are attractive candidates for use in molecular electronics because of the switching between different states with different conducting properties. The possibility of optically controlling the conductance of the molecule attached to leads may lead to new device implementations.

The switching reaction is investigated with potential energy calculations for different values of the reaction coordinate between the closed and the open isomer. The electronic and atomic structure calculations are performed with density functional theory (DFT). It is concluded that there is a large potential energy barrier separating the open and closed isomer and that switching between open and closed forms must involve excited states.

The conducting properties of the molecule inserted between gold leads is calculated within the Non Equilibrium Green Function theory. The transmission function is calculated for the two isomers with different basis sizes for the gold contacts, as well as the electrostatic potential, for finite applied bias voltages. We conclude that a Au 6s basis give qualitatively the same result as a Au spd basis close to the Fermi level. The transmission coefficient at the Fermi energy is around 10 times larger in the closed molecule compared to the open. This will result in a large difference in conductivity. It is also found that the large difference in conductivity will remain for small applied bias voltages. The results are consistent with earlier work.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. v, 35 p.
Keyword
molecular electronics, electron transport, electron structure, density functional theory, non equilibrium green function theory
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-4790 (URN)978-91-7415-020-9 (ISBN)
Presentation
2008-06-13, K408, Materialvetenskap, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101119Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2010-11-19Bibliographically approved

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