Enhanced thermoelectric performance and reversed anisotropy in the Janus penta-PdSeTe monolayer via biaxial strain

Abstract

Different from common isotropic 2H and 1T phases of 2D transition metal dichalcogenides, the pentagonal phase with structural anisotropy exhibits versatile properties. We herein explore the Janus penta-PdSeTe monolayer under biaxial strain using first-principles and Boltzmann transport theory. We find that it is necessary to consider the Coulomb interaction in order to calculate the accurate electronic band structure and phonon spectrum. Compared to without strain, a compressive strain of −3% increases the n-type power factor due to the increased n-type electrical conductivity with long electron relaxation time, and decreases the lattice thermal conductivity due to the decreased phonon group velocity and phonon relaxation time, leading to an increase from 0.33 (0.74) to 0.84 (1.24) of the n-type thermoelectric figure of merit (ZT) at 700 K along the x(y) direction. Although the p-type ZT value decreases under −3% strain, the anisotropy is reversed and enhanced by the p-type Seebeck coefficient. Under 4% tensile strain, although the ZT values decreased in both lattice directions and in both doping types, the p-type ZT value at 700 K along the y direction reached 1.52. The present work indicates the potential thermoelectric performance of the penta-PdSeTe monolayer without and with strain, and the compressive strain can greatly enhance the n-type ZT and reverse the p-type anisotropy, which will stimulate broad studies on strain-tuned thermoelectric performance and anisotropy of this class of Janus systems.