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Title: Interference enhanced thermoelectricity in quinoid type structures

Quantum interference (QI) effects in molecular junctions may be used to obtain large thermoelectric responses. We study the electrical conductance G and the thermoelectric response of a series of molecules featuring a quinoid core using density functional theory, as well as a semi-empirical interacting model Hamiltonian describing the π-system of the molecule which we treat in the GW approximation. Molecules with a quinoid type structure are shown to have two distinct destructive QI features close to the frontier orbital energies. These manifest themselves as two dips in the transmission, that remain separated, even when either electron donating or withdrawing side groups are added. We find that the position of the dips in the transmission and the frontier molecular levels can be chemically controlled by varying the electron donating or withdrawing character of the side groups as well as the conjugation length inside the molecule. This feature results in a very high thermoelectric power factor S{sup 2}G and figure of merit ZT, where S is the Seebeck coefficient, making quinoid type molecules potential candidates for efficient thermoelectric devices.
Authors:
;  [1] ; ; ;  [2]
  1. Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø (Denmark)
  2. Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft (Netherlands)
Publication Date:
OSTI Identifier:
22416190
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; DENSITY FUNCTIONAL METHOD; ELECTRIC CONDUCTIVITY; ELECTRIC CONTACTS; ELECTRONS; HAMILTONIANS; INTERFERENCE; MOLECULES; QUINONES; SEMICONDUCTOR JUNCTIONS; THERMOELECTRICITY