Thermoelectric performance and optoelectronic properties of Janus monolayer of ZrXY(X = O, S) (Y = S, Se)

Lower-dimensional TMDC materials are suitable for thermoelectric applications for their specific quantum confinement and being distinct in the density of states (DOS). Here we investigated thermoelectric properties of the 2D TMDC monolayer of ZrXY ((X = O, S,) (Y = S, Se)) by using Density Functional Theory (DFT) combined with Boltzmann Transport Equation (BTE). We obtained a standard thermoelectric figure of merit (ZT) of ZrOS, ZrOSe, and ZrSSe at 900 C. As ZrSSe monolayer showed a ZT value of 0.76 and 0.69 for n-type, and p-type materials respectively at 900 C, so, we investigated the new Janus monolayers of ZrOS and ZrOSe, and found a maximum ZT of 0.82 and 0.72 for n-type and p-type materials respectively, at 900 C which is quite satisfactory. While investigating the electronic property, we found that ZrOS, ZrOSe, and ZrSSe all possess an indirect bandgap (BG) of 1.88 eV, 1.02 eV, and 0.74 eV respectively. ZrOS and ZrOSe showed very high absorption in the ultraviolet (UV) region and blue region. However, ZrSSe showed a strong absorption between in the green region of the visible region, which suggests that these materials are useful in optoelectronic devices along with ther-moelectric applications.