First-principles predictions of enhanced thermoelectric properties for Cs₂SnI₂Cl₂and Cs₂PbI₂Cl₂monolayers with...

Inspired by the exceptional charge transport properties and ultra-low thermal conductivity of halide perovskite, we investigate the electronic nature, thermal transport, and thermoelectric properties for Ruddlesden-Popper all-inorganic perovskite, Cs₂SnI₂Cl₂and Cs₂PbI₂Cl₂monolayers, using first-principles calculations. During the calculations, spin-orbit coupling has been considered for electronic transport as well as thermoelectric properties. The results show that the Cs₂SnI₂Cl₂and Cs₂PbI₂Cl₂monolayers exhibit high carrier mobility and low thermal conductivity. Stronger phonon-phonon interaction is responsible for the fact that thermal conductivity of Cs₂SnI₂Cl₂monolayer is much lower than that of Cs₂PbI₂Cl₂monolayer. At 700 K, the values of the figure of merit (ZT) for the n-type doped Cs₂SnI₂Cl₂and Cs₂PbI₂Cl₂monolayers are about 1.05 and 0.32 at the optimized carrier concentrations 5.42 × 10¹²cm^-2and 9.84 × 10¹²cm^-2. Moreover, when spin-orbit coupling is considered, the correspondingZTvalues are enhanced to 2.73 and 1.98 at 5.27 × 10¹¹cm^-2and 6.16 × 10¹¹cm^-2. These results signify that Cs₂SnI₂Cl₂and Cs₂PbI₂Cl₂monolayers are promising thermoelectric candidates.