GeI2 monolayer: a model thermoelectric material from 300 to 600 K

In this work, the electronic structure, optical properties and thermoelectric properties of the GeI2 monolayer are calculated by the first principles with the Boltzmann transport equation. The monolayer is calculated as an indirect band gap semiconductor with an indirect band gap of a value 2.19 eV. This GeI2 monolayer is good for absorbing low-energy photons, and it is insensitive to high-energy photons. The material is stable at temperatures up to 600 K, so we calculated the thermal conductivity (K-L), Seebeck coefficient (S), power factor (PF) and thermoelectric figure of merit (ZT) of the GeI2 monolayer at various carrier concentrations from 300 to 600 K. Due to the lower group velocity, the GeI2 monolayer has a lower thermal conductivity of 0.48 W/m K at 300K. In P-type doping, the power factor can up to 0.11 mW/m K-2, and its ZT value is 4.04 at 600 K of the GeI2 monolayer, indicating that the GeI2 monolayer is a potential thermoelectric material.