Elucidating the Role of Stacking Faults in TlGaSe$_{2}$ on its Thermoelectric Properties

TL;DR

This study investigates how stacking faults in TlGaSe$_{2}$ influence its thermoelectric properties, revealing that these faults enhance power factors and can be optimized through doping for improved heat energy harvesting.

Contribution

The paper uncovers the role of stacking faults in TlGaSe$_{2}$'s thermoelectric performance using microscopy and first-principles calculations, highlighting their beneficial impact.

Findings

Stacking faults are prevalent throughout TlGaSe$_{2}$.

Presence of stacking faults enhances thermoelectric power factors.

Doping can further improve thermoelectric properties.

Abstract

Thermoelectric materials are of great interest for heat energy harvesting applications. One such promising material is TlGaSe$_{2}$, a p-type semiconducting ternary chalcogenide. Recent reports show it can be processed as a thin film, opening the door for large-scale commercialization. However, TlGaSe$_{2}$ is prone to stacking faults along the [001] stacking direction and their role in its thermoelectric properties has not been understood to date. Herein, TlGaSe$_{2}$ is investigated via (scanning) transmission electron microscopy and first-principles calculations. Stacking faults are found to be present throughout the material, as density functional theory calculations reveal a lack of preferential stacking order. Electron transport calculations show an enhancement of thermoelectric power factors when stacking faults are present. This implies the presence of stacking faults is key to the material's excellent thermoelectric properties along the [001] stacking direction, which can be further enhanced by doping the material to hole carrier concentrations to approx. 10$^{19}$ cm$^{-3}$.