A systematic Investigation of Thermoelectric Properties of Monolayers of ZrX2N4(X = Si, Ge)

In the past decade, it has been demonstrated that monolayers of metal dichalcogenides are well-suited for thermoelectric applications. ZrX2N4 (X = Si, Ge) is a reasonable choice for thermoelectric applications when considering a favorable value of the figure of merit in two-dimensional (2D) layered materials. In this study, we examined the thermoelectric characteristics of the two-dimensional monolayer of ZrX2N4 (where X can be either Si or Ge) using a combination of Density Functional Theory (DFT) and the Boltzmann Transport Equation (BTE). A thermoelectric figure of merit (ZT) of 0.90 was achieved at a temperature of 900 K for p-type ZrGe2N4, while a ZT of 0.83 was reported for n-type ZrGe2N4 at the same temperature. In addition, the ZrGe2N4 material exhibited a thermoelectric figure of merit (ZT) of around 0.7 at room temperature for the p-type. Conversely, the ZrSi2N4 exhibited a relatively lower thermoelectric figure of merit (ZT) at ambient temperature. At higher temperatures, the ZT value experiences a substantial increase, reaching 0.89 and 0.82 for p-type and n-type materials, respectively, at 900 K. Through our analysis of the electronic band structure, we have determined that ZrSi2N4 and ZrGe2N4 exhibit indirect bandgaps (BG) of 2.74 eV and 2.66 eV, respectively, as per the Heyd-Scuseria-Ernzerhof (HSE) approximation.