Size dependent thermoelectric properties of silicon nanowires

TL;DR

This study uses first-principles calculations to analyze how the thermoelectric properties of silicon nanowires vary with size, revealing that smaller diameters enhance thermoelectric efficiency and isotopic doping further improves performance.

Contribution

It provides a detailed size-dependent analysis of silicon nanowires' thermoelectric properties using first-principles methods, highlighting the benefits of small diameters and isotopic doping.

Findings

Electrical conductivity increases slowly with size

Seebeck coefficient decreases with size

Isotopic doping significantly increases ZT

Abstract

By using first-principles tight-binding electronic structure calculation and Boltzmann transport equation, we investigate the size dependence of thermoelectric properties of silicon nanowires (SiNWs). With cross section area increasing, the electrical conductivity increases slowly, while the Seebeck coefficient reduces remarkably. This leads to a quick reduction of cooling power factor with diameter. Moreover, the figure of merit also decreases with transverse size. Our results demonstrate that in thermoelectric application, NW with small diameter is preferred. We also predict that isotopic doping can increase the value of ZT significantly. With 50% 29Si doping (28Si0.529Si0.5 NW), the ZT can be increased by 31%.