First-Principles Simulation of Electron Mean-Free-Path Spectra and Thermoelectric Properties in Silicon

TL;DR

This study uses first-principles calculations to analyze electron and phonon mean-free-paths in silicon, predicting enhanced thermoelectric performance in nanostructured silicon by optimizing grain boundary scattering.

Contribution

It provides the first detailed spectral distribution of electron MFPs in silicon and predicts thermoelectric improvements through nanostructuring based on these insights.

Findings

Silicon nanostructuring with 20 nm grains can increase thermoelectric figure of merit by over five times.

Electron and phonon MFP distributions differ significantly, affecting transport properties.

Nanostructuring primarily scatters phonons, enhancing thermoelectric efficiency.

Abstract

The mean-free-paths (MFPs) of energy carriers are of critical importance to the nano-engineering of better thermoelectric materials. Despite significant progress in the first-principles-based understanding of the spectral distribution of phonon MFPs in recent years, the spectral distribution of electron MFPs remains unclear. In this work, we compute the energy dependent electron scatterings and MFPs in silicon from first-principles. The electrical conductivity accumulation with respect to electron MFPs is compared to that of the phonon thermal conductivity accumulation to illustrate the quantitative impact of nanostructuring on electron and phonon transport. By combining all electron and phonon transport properties from first-principles, we predict the thermoelectric properties of the bulk and nanostructured silicon, and find that silicon with 20 nm nanograins can result in more than five times enhancement in their thermoelectric figure of merit as the grain boundaries scatter phonons more significantly than that of electrons due to their disparate MFP distributions.