Quantum transport simulations for the thermoelectric power factor in two dimensional nanocomposites

TL;DR

This paper uses quantum mechanical simulations to study how nanoinclusions and voids affect the thermoelectric power factor in two-dimensional nanocomposites, revealing conditions under which they enhance or degrade thermoelectric performance.

Contribution

It provides a comprehensive quantum mechanical analysis of the impact of nanoinclusions and voids on thermoelectric properties, incorporating geometry, interactions, and transport regimes.

Findings

Nanoinclusions with low barrier height can boost the Seebeck coefficient.

Power factor remains stable with nanoinclusion density in ballistic transport.

Voids degrade the power factor, especially with increased density under phonon scattering.

Abstract

Some of the most promising candidates for next generation thermoelectrics are nanocomposites due to their low thermal conductivities that result from phonon scattering on the boundaries of the various material phases. However, in order to maximize the figure of merit ZT, it is important to understand the impact of such features on the thermoelectric power factor. In this work we consider the effect that nanoinclusions and voids have on the electronic and thermoelectric coefficients of two dimensional geometries using the fully quantum mechanical Non Equilibrium Greens Function method. This method combines in a unified approach the details of geometry, electron phonon interactions, quantisation, tunnelling, and the ballistic to diffusive nature of transport. We show that as long as the barrier height is low nanoinclusions can have a positive impact on the Seebeck coefficient and the power factor is not severely impacted by a reduction in conductance. The power factor is also shown to be approximately independent of nanoinclusion and void density in the ballistic case. On the other hand, in the presence of phonon scattering voids degrade the power factor and their influence increases with density.