Strain-induced thermoelectric performance enhancement of monolayer ZrSe2

Abstract

Monolayer ZrSe₂ was previously predicted to be one kind of excellent thermoelectric material due to its low lattice thermal conductivity. Motivated by the recent proposal of enhancing thermoelectric performance via strain-induced electronic band degeneracy, we have performed first-principles calculations on the effect of biaxial tensile strain on the thermoelectric properties of monolayer ZrSe₂ combined with Boltzmann transport theory and deformation potential theory. The theoretical results demonstrate that the band degeneracy reaches its maximum at 7.5% strain, resulting in an increase of the Seebeck coefficient and, at the same time, a decrease of the lattice thermal conductivity. At this optimal strain, a two-fold increase of the figure of merit is obtained for an n-doped ZrSe₂ monolayer at room temperature. Moreover, the figures of merit for p- and n-type doping are much more balanced in the strain case compared with the unstrained one.