Enhancement of Thermoelectric Efficiency in PbTe by Distortion of the Electronic Density of States

TLDR

Thermoelectric energy conversion efficiency is limited by the figure of merit (zT), and recent nanostructure advances that reduce phonon heat conduction are approaching the amorphous limit beyond which thermal conductivity cannot be lowered. The study aims to enhance the Seebeck coefficient by distorting the electronic density of states using thallium impurity levels in PbTe, and to evaluate the potential of combining this approach with nanostructuring to further increase zT and broaden thermoelectric applications. The authors implemented this by introducing thallium impurity levels into PbTe to distort its electronic density of states and thereby increase the Seebeck coefficient. Band‑structure engineering with thallium in PbTe doubled zT in p‑type material to over 1.5 at 773 K.

Abstract

The efficiency of thermoelectric energy converters is limited by the material thermoelectric figure of merit (zT). The recent advances in zT based on nanostructures limiting the phonon heat conduction is nearing a fundamental limit: The thermal conductivity cannot be reduced below the amorphous limit. We explored enhancing the Seebeck coefficient through a distortion of the electronic density of states and report a successful implementation through the use of the thallium impurity levels in lead telluride (PbTe). Such band structure engineering results in a doubling of zT in p-type PbTe to above 1.5 at 773 kelvin. Use of this new physical principle in conjunction with nanostructuring to lower the thermal conductivity could further enhance zT and enable more widespread use of thermoelectric systems.