High figure of merit of monolayer Sb2Te2Se of ultra low lattice thermal conductivity

Abstract The electronic structure and thermoelectric properties of monolayer Sb2Te2Se are studied by density functional theory and semi-classical Boltzmann transport equation. The Seebeck coefficient for monolayer Sb2Te2Se is very high, comparing with other thermoelectric materials. The strong coupling of acoustic and optical modes enhanced phonon scattering, which will cause lower lattice thermal conductivity. The heavy elements and small band gap cause the low thermal conductivity of monolayer Sb2Te2Se, so the lattice thermal conductivity of monolayer Sb2Te2Se is much lower than other thermoelectric materials. The optimal value ZeT of monolayer Sb2Te2Se is so high, mainly due to the very low lattice thermal conductivity. For the better n-type, ZeT reaches 1.5 at a temperature of 1000 K, which proves that monolayer Sb2Te2Se is a good choice for thermoelectric materials.