Novel Janus gamma-Pb$$_2$$XY monolayers with high thermoelectric performance X=S, Se and Y=Se, Te X$$\ne $$Y

Abstract

The quest for efficient thermoelectric materials has intensified with the advent of novel Janus monolayers exhibiting exceptional thermoelectric parameters. In this work, we comprehensively investigate the structural, electronic, transport, phonon, and thermoelectric properties of novel Janus $$\gamma $$ γ -Pb$$_2$$ 2 XY (X=S, Se; Y=Se, Te; X$$\ne $$ ≠ Y) monolayers using density functional theory combined with the Boltzmann transport equation. Our findings unveil the energetic, dynamic, thermal, and mechanical stability of these monolayers, along with their remarkable thermoelectric performance. Remarkably, the p-type $$\gamma $$ γ -Pb$$_2$$ 2 SeTe monolayer exhibits an outstanding figure of merit (ZT) of 6.88 at 800 K, attributed to its intrinsically low lattice thermal conductivity of 0.162 Wm$$^{-1}$$ - 1 K$$^{-1}$$ - 1 arising from strong phonon scattering, low group velocity, low phonon relaxation time, and a high Grüneisen parameter. Furthermore, these monolayers demonstrate high Seebeck coefficients and electrical conductivities, making them promising for efficient charge transport and thermoelectric energy conversion. Our results highlight the immense potential of Janus $$\gamma $$ γ -Pb$$_2$$ 2 XY monolayers as promising candidates for high-temperature thermoelectric applications and open up exciting avenues for further exploration of these novel two-dimensional materials in energy-related technologies.