Tuning the electronic structures and transport coefficients of Janus PtSSe monolayer with biaxial strain

Due to their great potential in electronics, optoelectronics, and piezoelectronics, Janus transition metal dichalcogenide monolayers have attracted an increased interest in research, and the MoSSe monolayer of them with the sandwiched S-Mo-Se structure has been synthesized experimentally. Here, we systematically study the effect of strain on electronic structures and transport properties of the Janus PtSSe monolayer. A detrimental effect on the power factor of the PtSSe monolayer can be observed when the spin-orbital coupling is included. With a/a0 from 0.94 to 1.06, the energy bandgap shows a nonmonotonic behavior, which is due to the position change of conduction band minimum. The strength of conduction bands convergence can be enhanced by changing the relative position of conduction band extrema caused by compressive strain, which is in favor of the n-type ZTe. Calculated results show that compressive strain can also induce flat valence bands around the Γ point near the Fermi level, which can lead to a high Seebeck coefficient due to large effective masses, giving rise to better p-type ZTe values. The calculated elastic constants with a/a0 from 0.94 to 1.06 all satisfy the mechanical stability criteria, which proves that the PtSSe monolayer is mechanically stable in the considered strain range. Our works provide a new route to tune the electronic structures and transport coefficients of the Janus PtSSe monolayer by biaxial strain and can motivate related experimental studies.