A Strategic Comparison Between Monolayers of WX2N4(X≐Si, Ge) Toward Thermoelectric Performance and Optoelectronic Properties.

New 2D layered materials WX2N4(X & esdot;Si, Ge)(1) are suitable for thermoelectric applications for a pretty good value of the figure of merit (ZT). Here, the thermoelectric properties of the 2D monolayer of WX2N4(X & esdot;Si, Ge) using Density Functional Theory (DFT) is investigated combined with Boltzmann Transport Equation (BTE) along with spin-orbit coupling (SOC). An excellent thermoelectric ZT of 0.91 (0.92 with SOC) is obtained at 900 K for p-type WGe2N4, and a ZT of 0.81 (0.86 with SOC) is observed for n-type at the same temperature. Furthermore, the WGe2N4 showed a ZT of more than 0.7 (0.79 with SOC) at room temperature for p-type. On the other hand, the WSi2N4 showed a comparatively lower ZT at room temperature. However, the ZT value increases significantly at higher temperatures, reaching 0.72 (0.79 with SOC) and 0.71 (0.62 with SOC) for p and n-type at 900 K, respectively. The electronic band structure is examined and discovered that WSi2N4 and WGe2N4 possess indirect bandgaps (BG) of 2.68 eV (2.57 eV with SOC) and 1.53 eV (1.46 eV with SOC), respectively, according to Heyd-Scuseria-Ernzerhof (HSE) approximation. These materials may also be useful in UV and visible range optoelectronic devices because of their strong absorption in the respective regions.