2011/11/01 by Branislav K. Nikolic, Branislav K. Nikolić, Kamal Krishna Saha +3 · 1 citation
Engineering · Materials Science · Physics and Astronomy · #Advanced Thermoelectric Materials and Devices #Condensed matter physics #Electrode #Graphene #Graphene research and applications #Materials science #Molecular Junctions and Nanostructures #Molecule #Nanotechnology #Physics #Quantum #Quantum mechanics #Thermoelectric effect #cond-mat.mes-hall
paper · pdf · doi:10.1007/s10825-012-0386-y
published as J. Comp. Electronics 11, 78 (2012) · 20 pages, 6 figures; mini-review article prepared for the special issue of the Journal of Computational Electronics on "Simulation of Thermal, Thermoelectric, and Electrothermal Phenomena in Nanostructures", edited by I. Knezevic and Z. Aksamija
arxiv created 2011/11/01 · openalex publication_date 2012/01/30 · arxiv updated 2012/04/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We overview nonequilibrium Green function combined with density functional theory (NEGF-DFT) modeling of independent electron and phonon transport in nanojunctions with applications focused on a new class of thermoelectric devices where a single molecule is attached to two metallic zigzag graphene nanoribbons (ZGNRs) via highly transparent contacts. Such contacts make possible injection of evanescent wavefunctions from ZGNRs, so that their overlap within the molecular region generates a peak in the electronic transmission. Additionally, the spatial symmetry properties of the transverse propagating states in the ZGNR electrodes suppress hole-like contributions to the thermopower. Thus optimized thermopower, together with diminished phonon conductance through a ZGNR/molecule/ZGNR inhomogeneous structure, yields the thermoelectric figure of merit ZT~0.5 at room temperature and 0.5<ZT<2.5 below liquid nitrogen temperature. The reliance on evanescent mode transport and symmetry of propagating states in the electrodes makes the electronic-transport-determined power factor in this class of devices largely insensitive to the type of sufficiently short conjugated organic molecule, which we demonstrate by showing that both 18-annulene and C10 molecule sandwiched by the two ZGNR electrodes yield similar thermopower. Thus, one can search for molecules that will further reduce the phonon thermal conductance (in the denominator of ZT) while keeping the electronic power factor (in the nominator of ZT) optimized. We also show how often employed Brenner empirical interatomic potential for hydrocarbon systems fails to describe phonon transport in our single-molecule nanojunctions when contrasted with first-principles results obtained via NEGF-DFT methodology.