Potential thermoelectric material $\mathrm{Cs_2[PdCl_4]I_2}$: a first-principles study

TL;DR

This study uses first-principles calculations to evaluate the thermoelectric properties of Cs2[PdCl4]I2, revealing its potential as a thermoelectric material with a maximum ZT of about 0.70 under certain conditions.

Contribution

It provides a detailed first-principles analysis of the electronic and thermal transport properties of Cs2[PdCl4]I2, highlighting the effects of spin-orbit coupling and estimating its thermoelectric efficiency.

Findings

Spin-orbit coupling affects valence bands and p-type power factor.

Ultralow lattice thermal conductivity of 0.31 W/m·K at room temperature.

Maximum ZT of about 0.70 with specific scattering times.

Abstract

The electronic structures and thermoelectric properties of $\mathrm{Cs_2[PdCl_4]I_2}$ are investigated by the first-principles calculations and semiclassical Boltzmann transport theory. Both electron and phonon transport are considered to attain the figure of merit $ZT$. A modified Becke and Johnson (mBJ) exchange potential, including spin-orbit coupling (SOC), is employed to investigate electronic part of $\mathrm{Cs_2[PdCl_4]I_2}$. It is found that SOC has obvious effect on valence bands, producing huge spin-orbital splitting, which leads to remarkable detrimental effect on p-type power factor. However, SOC has a negligible influence on conduction bands, so the n-type power factor hardly change. The temperature dependence of lattice thermal conductivity by assuming an inverse temperature dependence is attained from reported ultralow lattice thermal conductivity of 0.31 $\mathrm{W m^{-1} K^{-1}}$ at room temperature. Calculating scattering time $\tau$ is challenging, but a hypothetical $\tau$ can be adopted to estimate thermoelectric conversion efficiency. The maximal figure of merit $ZT$ is up to about 0.70 and 0.60 with scattering time $\tau$=$10^{-14}$ s and $\tau$=$10^{-15}$ s, respectively. These results make us believe that $\mathrm{Cs_2[PdCl_4]I_2}$ may be a potential thermoelectric material.