Enhanced thermopower in two-dimensional ruthenium dichalcogenides $Ru{X}_2$ (X = S, Se): a first-principles study

Transition metal dichalcogenides (TMDs) have garnered attention for their potential in thermoelectric applications due to their unique electronic properties and tunable bandgaps. In this study, we systematically explore the electronic and thermoelectric properties of $T^{\mathrm{\prime }}-Ru{X}_2$ (X = S, Se) using first-principles calculations and semi-classical Boltzmann transport equations. Our findings confirm that $T^{\mathrm{\prime }}-Ru{X}_2$ is energetically and mechanically stable, with high thermopower values such that $T^{\mathrm{\prime }}-Ru{S}_2$ exhibits a Seebeck coefficient of $2685\mu V\mathrm{/}K$ for hole doping and $2585\mu V\mathrm{/}K$ for electron doping, while $T^{\mathrm{\prime }}-RuS{e}_2$ shows values of $1515\mu V\mathrm{/}K$ and $1533\mu V\mathrm{/}K$ for hole and electron doping, respectively. Both materials exhibit reasonable power factors and $ZT$ values, with p-type $T^{\mathrm{\prime }}-Ru{S}_2$ and $T^{\mathrm{\prime }}-RuS{e}_2$ achieving maximum ZT values of 0.85 and 0.87, respectively, at 1200~K along the y-direction. These results highlight $T^{\mathrm{\prime }}$-$Ru{S}_2$ and $T^{\mathrm{\prime }}$-$RuS{e}_2$ as promising candidates for high-temperature TMD-based thermoelectric devices.