Thermoelectric power factor of nanocomposite materials from two-dimensional quantum transport simulations

Abstract

Nanocomposites are promising candidates for the next generation of thermoelectric materials since they exhibit extremely low thermal conductivities as a result of phonon scattering on the boundaries of the various material phases. The nanoinclusions, however, should not degrade the thermoelectric power factor, and ideally should increase it, so that benefits to the ZT figure of merit can be achieved. In this work we employ the Non-Equilibrium Greens Function (NEGF) quantum transport method to calculate the electronic and thermoelectric coefficients of materials embedded with nanoinclusions. For computational effectiveness we consider two-dimensional nanoribbon geometries, however, the method includes the details of geometry, electron-phonon interactions, quantisation, tunneling, and the ballistic to diffusive nature of transport, all combined in a unified approach. This makes it a convenient and accurate way to understand electronic and thermoelectric transport in nanomaterials, beyond semiclassical approximations, and beyond approximations that deal with the complexities of the geometry. We show that the presence of nanoinclusions within a matrix material offers opportunities for only weak energy filtering, significantly lower in comparison to superlattices, and thus only moderate power factor improvements. However, we describe how such nanocomposites can be optimised to limit degradation in the thermoelectric power factor and elaborate on the conditions that achieve the aforementioned mild improvements. Importantly, we show that under certain conditions, the power factor is independent of the density of nanoinclusions, meaning that materials with large nanoinclusion densities which provide very low thermal conductivities, can also retain large power factors and result in large ZT figures of merit.

arXiv comment33 pages, 10 figures

References in corpus (8)

• Theory of enhancement of thermoelectric properties of materials with nanoinclusions
• Influence of Dimensionality on Thermoelectric Device Performance
• Non-equilibrium Green's function treatment of phonon scattering in carbon nanotube transistors
• First-Principles Simulation of Electron Mean-Free-Path Spectra and Thermoelectric Properties in Silicon
• Atomistic simulations of low-field mobility in Si nanowires: Influence of confinement and orientation
• Beating the amorphous limit in thermal conductivity by superlattices design
• Optimizing Thermoelectric Power Factor by Means of a Potential Barrier
• The influence of non-idealities on the thermoelectric power factor of nanostructured superlattices

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• Hierarchically nanostructured thermoelectric materials: Challenges and opportunities for improved power factors
• Analysis of simple scattering models on the thermoelectric performance of analytical electron dispersions
• Hybrid-functional and quasi-particle calculations of band structures of Mg2Si, Mg2Ge, and Mg2Sn
• Enhanced Phonon Boundary Scattering at High Temperatures in Hierarchically Disordered Nanostructures
• Modelling thermoelectric performance in nanoporous nanocrystalline silicon
• Thermoelectric power factor in nanostructured materials with randomized nanoinclusions
• Asymmetric Electronic Band Alignment and Potentially Enhanced Thermoelectric Properties in Phase-Separated Mg2X (X=Si,Ge,Sn) Alloys