Excellent optoelectronic and thermoelectric properties of two-dimensional transition metal dinitride HfN2

Optoelectronic and thermoelectric properties of two-dimensional (2D) transition metal dinitride (HfN2) have been studied using first-principles calculations. Monolayer and bilayer HfN2 transport properties were calculated by solving the transport equations for electrons and phonons. The highest calculated ZT value for the bilayer HfN2 was 0.85 at 900 K in the negative chemical potential region. This high value of the figure of merit suggests that the material would be an excellent choice for thermoelectric energy harvesting devices. The optical property of the material suggests that it is a very good absorber in the ultraviolet (UV) region; thus, it can also be used as a UV-photodetector and as an absorber layer in photovoltaic devices.