Chromium ditelluride monolayer: A novel promising 2H phase thermoelectric material with direct bandgap and ultralow lattice thermal conductivity

Abstract

Inspired by the groundbreaking discoveries of the transition metal dichalcogenides materials (TMDCs) with 2H- and 1T- phases, the crystal structure, electronic and phonon thermal transport, and thermoelectric properties of novel 2H-phase CrTe2 monolayer are theoretically evaluated by the first-principles calculation and Boltzmann transport theory. The 2H-CrTe2 monolayer is a direct semiconductor with a bandgap of ∼ 0.93 eV. The elastic modulus and phonon dispersion calculations demonstrate that the 2H-CrTe2 monolayer is mechanically and dynamically stable due to the absence of negative value in elastic constant and frequency. Ab initio molecular dynamics (AIMD) simulations demonstrate the thermal stability of the 2H-CrTe2 monolayer at high temperature, as evidenced by slight fluctuations in total energy. In combination with the small group velocity, large Grüneisen parameter, and strong anharmonic scattering, the ultralow lattice thermal conductivity is predicated for the 2H-CrTe2 monolayer (∼ 0.21 W/mK @ 300 K). The optimal dimensionless figure of merit (ZT) values for the p- and n-type 2H-CrTe2 monolayers are ∼ 4.05 and ∼ 3.08 at 900 K, respectively. Our present results would not only provide a fundamental understanding of electronic transport and thermoelectric properties of the 2H-CrTe2 monolayer, but also shed some light on the theoretical design of low dimensional nanomaterials with high thermoelectric applications.