Studying the lifetime of charge and heat carriers due to intrinsic scattering mechanisms in FeVSb half-Heusler thermoelectric

TL;DR

This paper investigates the intrinsic scattering mechanisms affecting carrier lifetimes in FeVSb half-Heusler thermoelectric, emphasizing the roles of electron-electron, electron-phonon, and phonon-phonon interactions through advanced computational methods.

Contribution

It provides a comprehensive analysis of carrier and phonon lifetimes considering multiple scattering mechanisms, highlighting the importance of including EEI and EPI in thermoelectric transport calculations.

Findings

Carrier lifetimes at 300K are approximately 1.91 x10^{-14}s (VBM) and 2.05 x10^{-14}s (CBM).

EPI dominates phonon scattering above 500K, significantly affecting thermal conductivity.

Acoustic phonons have longer lifetimes than optical phonons, contributing more to lattice thermal conductivity.

Abstract

This work, presents a study of lifetime of carriers due to intrinsic scattering mechanisms $viz.$ electron-electron (EEI), electron-phonon (EPI) and phonon-phonon interactions (PPI) in a promising half-Heusler thermoelectric FeVSb. Using the full-$GW$ method, the effect of EEI and temperature on the valence and conduction band extrema and band gap are studied. The lifetime of carriers with temperature are estimated at these band extrema. At 300 K, estimated value of lifetime at VBM (CBM) is $\sim$1.91 x10$^{-14}s$ ($\sim$2.05 x10$^{-14}s$). The estimated ground state band gap considering EEI is $\sim$378 meV. Next, the effect of EPI on the lifetime of electrons and phonons with temperature are discussed. The comparison of two electron lifetimes suggests that EEI should be considered in transport calculations along with EPI. The average acoustic, optical and overall phonon lifetimes due to EPI are studied with temperature. Further, the effect of PPI is studied by computing average phonon lifetime for acoustic and optical phonon branches. The lifetime of the acoustic phonons are higher compared to optical phonons which indicates acoustic phonons contribute more to lattice thermal conductivity ($\kappa_{ph}$). The comparison of phonon lifetime due to EPI and PPI suggests that, above 500 K EPI is the dominant phonon scattering mechanism and cannot be ignored in $\kappa_{ph}$ calculations. Lastly, a prediction of the power factor and figure of merit of n-type and p-type FeVSb is made by considering the temperature dependent carrier lifetime for the electronic transport terms. This study shows the importance of considering EEI in electronic transport calculations and EPI in phonon transport calculations. Our study is expected to provide results to further explore the thermoelectric transport in this material.