Thermoelectric enhancement in PbTe with K, Na co-doping from tuning the interaction of the light and heavy hole valence bands

TL;DR

This study investigates how K and Na co-doping in PbTe influences valence band interactions, leading to improved thermoelectric performance without forming resonance states, through detailed experimental analysis.

Contribution

It demonstrates that K-Na co-doping controls valence band energy differences, enhancing thermoelectric efficiency without creating resonance states, which is a novel insight.

Findings

K-Na co-doping does not form resonance states.

Co-doping controls valence band energy differences.

Enhanced thermoelectric figure of merit observed.

Abstract

The effect of K and K-Na substitution for Pb atoms in the rock salt lattice of PbTe was investigated to test a hypothesis for development of resonant states in the valence band that may enhance the thermoelectric power. We combined high temperature Hall-effect, electrical conductivity and thermal conductivity measurements to show that K-Na co-doping do not form resonance states but2 can control the energy difference of the maxima of the two primary valence sub-bands in PbTe. This leads to an enhanced interband interaction with rising temperature and a significant rise in the thermoelectric figure of merit of p-type PbTe. The experimental data can be explained by a combination of a single and two-band model for the valence band of PbTe depending on hole density that varies in the range of 1-15 x 10^19 cm^-3.