Structural, electronic, vibrational, and thermoelectric properties of Janus Ge 2 P<i> X</i> (<i> X</i> = N, As, Sb, and Bi) monolayers

Abstract

Two-dimensional (2D) Janus systems have garnered significant scientific interest owing to their novel properties and potential applications. The growing interest in these materials is driven by the idea that their structural asymmetry offers unprecedented opportunities for enhancing thermoelectric performance and unlocking groundbreaking advancements in energy conversion and waste heat utilization. In this context, we present a comprehensive study on the structural, vibrational, electronic, thermal, and thermoelectric properties of Janus Ge2PX(X = N, As, Sb, and Bi) monolayers, using first-principles calculations combined with the Landauer formalism. The suggested configurations exhibit dynamical stability and retain structural integrity even at elevated temperatures. Electronic structure calculations employing hybrid functionals (HSE06) with spin-orbit coupling reveal that Ge2PAs and Ge2PSb monolayers exhibit anisotropic characteristics as indirect semiconductors, while Ge2PN and Ge2PBi exhibit metallic behavior. We also compare the thermal, electronic, and thermoelectric transport properties of these proposed monolayers to binary 2D GeP in the ballistic limit. Notably, both Ge2PAs and Ge2PSb exhibit n-type figure of merit (ZT ) values exceeding 1 at 800 K, with their n-type ZT values surpassing that of GeP at room temperature. Our analysis underscores the distinctive structural and electronic properties of Ge2PAs and Ge2PSb monolayers, accompanied by their highly promising thermoelectric performance. These findings position them as strong candidates for energy harvesting and conversion applications.