Towards a dynamical approach to the calculation of the figure of merit of thermoelectric nanoscale devices

D’Agosta, Roberto

doi:10.1039/c2cp42594g

Cited by 25 publications

(21 citation statements)

References 70 publications

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“…Based on the electron bands, we calculated the carrier transport coefficients via the Landauer theory in the linear response regime. Further details about these techniques can be found elsewhere [25][26][27]. The results we present in the following, based on these approximations, are in good agreement with experimental values (see below).…”

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confidence: 78%

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Optimal thermoelectric figure of merit of Si/Ge core-shell nanowires

et al. 2015

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We investigate the thermoelectric energy conversion efficiency of Si and Ge nanowires, and in particular, that of Si/Ge core-shell nanowires. We show how the presence of a thin Ge shell on a Si core nanowire increases the overall figure of merit. We find the optimal thickness of the Ge shell to provide the largest figure of merit for the devices. We also consider Ge core/Si shell nanowires, and show that an optimal thickness of the Si shell does not exist, since the figure of merit is a monotonically decreasing function of the radius of the nanowire. Finally, we verify the empirical law relating the electron energy gap to the optimal working temperature that maximizes the efficiency of the device.Thermoelectricity is the ability of a material to convert a thermal gradient into an electrical current [1][2][3][4][5]. A main advantage of this energy conversion mechanism is its lack of moving parts, so thermoelectric devices can have very long lifespans. Moreover, the method can find applications in extreme conditions where other methods are not suitable, e.g., in spacecraft where normal batteries are too heavy and will not provide energy for sufficient time, or for portable energy production. The efficiency of thermoelectric energy conversion is related to a device's so-called figure of merit, denoted as ZT. This number is defined in terms of the microscopic quantities characteristic of a device, i.e.,where S is the Seebeck coefficient, σ the electrical conductance,  ep the thermal conductance including both electronic and crystal contributions, and T the operating temperature. In the linear regime, i.e., when the applied gradient and currents are not very large, the figure of merit determines the efficiency of the device: η η

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confidence: 78%

“…This law is a phenomenological result, mostly valid for metal. The origin of this discrepancy can be understood via the Landauer theory of transport [25,26]. Indeed, in this theory,  e is formed by two different contributions arising from different Lorentz integrals [25,26].…”

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confidence: 98%

Optimal thermoelectric figure of merit of Si/Ge core-shell nanowires

et al. 2015

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“…In linear response theory, by using Onsager's relations and the Landauer theory of quantum transport, the electrical conductance σ , the Seebeck coefficient S, and the electron contributed thermal conductance κ e , can be written as [2,3,39] …”

Section: Methodsmentioning

confidence: 99%

Thermoelectric properties of atomically thin silicene and germanene nanostructures

et al. 2014

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The thermoelectric properties in one-and two-dimensional silicon and germanium structures have been investigated using first-principles density functional techniques and linear response for the thermal and electrical transport. We have considered here the two-dimensional silicene and germanene, together with nanoribbons of different widths. For the nano ribbons, we have also investigated the possibility of nano structuring these systems by mixing silicon and germanium. We found that the figure of merit at room temperature of these systems is remarkably high, up to 2.5.

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“…This was used to find the thermoelectric response and figure of merit of various molecules between metallic contacts, and thereby show how to engineer the transmission function; for example by adding side groups to the molecule which introduce Fano resonances at the right energy to generate a strong thermoelectric response [148,149]. Other works on using density function theory for thermoelectrics include [151,152]. Recently a powerful software package [153] has been developed based on the technique called LDA+U with spectral adjustments for coupled spin, charge and thermal transport.…”

Section: Transmission Functions For More Complicated Systemsmentioning

confidence: 99%

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

et al. 2017

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In recent years, the study of heat to work conversion has been re-invigorated by nanotechnology. Steady-state devices do this conversion without any macroscopic moving parts, through steady-state flows of microscopic particles such as electrons, photons, phonons, etc. This review aims to introduce some of the theories used to describe these steady-state flows in a variety of mesoscopic or nanoscale systems. These theories are introduced in the context of idealized machines which convert heat into electrical power (heat-engines) or convert electrical power into a heat flow (refrigerators). In this sense, the machines could be categorized as thermoelectrics, although this should be understood to include photovoltaics when the heat source is the sun. As quantum mechanics is important for most such machines, they fall into the field of quantum thermodynamics. In many cases, the machines we consider have few degrees of freedom, however the reservoirs of heat and work that they interact with are assumed to be macroscopic. This review discusses different theories which can take into account different aspects of mesoscopic and nanoscale physics, such as coherent quantum transport, magnetic-field induced effects (including topological ones such as the quantum Hall effect), and single electron charging effects. It discusses the efficiency of thermoelectric conversion, and the thermoelectric figure of merit. More specifically, the theories presented are (i) linear response theory with or without magnetic fields, (ii) Landauer scattering theory in the linear response regime and far from equilibrium, (iii) Green-Kubo formula for strongly interacting systems within the linear response regime, (iv) rate equation analysis for small quantum machines with or without interaction effects, (v) stochastic thermodynamic for fluctuating small systems. In all cases, we place particular emphasis on the fundamental questions about the bounds on ideal machines. Can magnetic-fields change the bounds on power or efficiency? What is the relationship between quantum theories of transport and the laws of thermodynamics? Does quantum mechanics place fundamental bounds on heat to work conversion which are absent in the thermodynamics of classical systems?

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Towards a dynamical approach to the calculation of the figure of merit of thermoelectric nanoscale devices

Cited by 25 publications

References 70 publications

Optimal thermoelectric figure of merit of Si/Ge core-shell nanowires

Optimal thermoelectric figure of merit of Si/Ge core-shell nanowires

Thermoelectric properties of atomically thin silicene and germanene nanostructures

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

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