Thermoelectric performance in two-dimensional CX (X=Si, Ge, Sn) compounds

The thermoelectric performance of the materials, which is of great interest for the waste heat recovery and solid-state cooling, is determined by figure of merit or the ZT for the two-dimensional honeycomb lattices GeC, SnC and SiC. Using the first principles calculations based on the GGA and HSE approximation, it is found that that SiC and SnC are indirect semiconductors, unlike GeC which exhibits a direct band gap. Furthermore, calculations employing semi-classical Boltzmann transport theory reveal that the thermoelectric performance of these 2D compounds is improved with respect to their graphene, silicene and germanene counterparts. At 700 K, the highest figure of merit (ZT) is 0.78 and 0.46 for GeC and SiC respectively, while it reaches the great value of 2.08 for SnC material that exhibits the lowest thermal conductivity. Our findings assess the potential of CX {X = Si,Ge,Sn} compounds as suitable thermoelectric materials at the temperature gradient from 100 to 700 K. •Thermoelectric performance of XC (X = Si, Ge, Sn) compounds is explored.•Carrier mobility, relaxation time and conductivity are determined at different temperatures.•The increasing in temperature results in the increase of the Seebeck coefficients.•SnC exhibits the highest figure of merit, largely followed by GeC then SiC.•CX compounds are suitable thermoelectric materials at the temperature gradient from 100 to 700 K.