Efficient thermoelectric energy conversion on quasi-localized electron states in diameter modulated nanowires

Xanthippi Zianni

doi:10.1186/1556-276x-6-286

Abstract

It is known that the thermoelectric efficiency of nanowires increases when their diameter decreases. Recently, we proposed that increase of the thermoelectric efficiency could be achieved by modulating the diameter of the nanowires. We showed that the electron thermoelectric properties depend strongly on the geometry of the diameter modulation. Moreover, it has been shown by another group that the phonon conductivity decreases in nanowires when they are modulated by dots. Here, the thermoelectric efficiency of diameter modulated nanowires is estimated, in the ballistic regime, by taking into account the electron and phonon transmission properties. It is demonstrated that quasi-localized states can be formed that are prosperous for efficient thermoelectric energy conversion.

Highlights

A measure of the thermoelectric efficiency of a material is the dimensionless figure of merit ZT ≡ S2sT/, where s is the conductivity, S is the thermopower, is the thermal conductivity and T is the absolute temperature
It has been theoretically shown that nanodots can have very high thermoelectric efficiencies due to their discrete energy spectrum [2,3,4]
If we consider a wire with diameter modulation by units that assume discrete energy spectra, e.g. quantum dots (Figure 1), the transmission coefficient will have transmission resonances, transmission bands and transmission gaps

Summary

Introduction

A measure of the thermoelectric efficiency of a material is the dimensionless figure of merit ZT ≡ S2sT/, where s is the conductivity, S is the thermopower, is the thermal conductivity and T is the absolute temperature. In this Letter, we focus on the electron propagation states that we reported to have high values of thermoelectric figure of merit when phonon conduction was neglected. The thermoelectric efficiency of these states is estimated, here, by taking into account the electron and phonon transmission properties.

Results

Conclusion