  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.
