Thermoelectric properties of electrically gated bismuth telluride nanowires

TL;DR

This study theoretically demonstrates that applying a perpendicular electric field to bismuth telluride nanowires significantly enhances their thermoelectric properties, especially the Seebeck coefficient and figure of merit ZT, across a broad temperature range.

Contribution

The paper introduces a self-consistent quantum-mechanical model to analyze electric field effects on thermoelectric properties of bismuth telluride nanowires, revealing substantial performance improvements.

Findings

Electric field nearly doubles the Seebeck coefficient.

ZT can reach up to 3.4 at room temperature.

External electric field enhances thermoelectric efficiency significantly.

Abstract

We theoretically studied the effect of the perpendicular electric field on the thermoelectric properties of the intrinsic, n-type and p-type bismuth telluride nanowires with the growth direction [110]. The electronic structure and the wave functions were calculated by solving self-consistently the system of the Schrodinger and Poisson equations using the spectral method. The Poisson equation was solved in terms of the Newton - Raphson method within the predictor-corrector approach. The electron - electron exchange - correlation interactions were taken into account in our analysis. In the temperature range from 77 to 500 K, the dependences of the Seebeck coefficient, thermal conductivity, electron (hole) concentration, and thermoelectric figure of merit on the nanowire thickness, gate voltage, and excess hole (electron) concentration were investigated in the constant relaxation-time approximation. The results of our calculations indicate that the external perpendicular electric field can increase the Seebeck coefficient of the bismuth telluride nanowires with thicknesses of 7 - 15 nm by nearly a factor of 2 and enhance ZT by an order of magnitude. At room temperature, ZT can reach a value as high as 3.4 under the action of the external perpendicular electric field for realistic widths of the nanowires. The obtain results may open up a completely new way for a drastic enhancement of the thermoelectric figure of merit in a wide temperature range.