Theoretical insights into the thermoelectric properties of carbon, germanium, and silicon nanosheets: a comparative study

Abstract

This study examined the electrical conductivity, Seebeck coefficient, electronic and phonon thermal conductance, and overall figure of merit (\(\text{ZT}\)) of (6,0) C–C, Ge–Ge, and Si–Si nanosheets as functions of chemical potential in order to systematically analyze their thermoelectric properties at room temperature. We achieved a thorough understanding of the interaction between electrical and thermal transport in these two-dimensional materials by using first-principles calculations based on density functional theory-based tight-binding (DFTB) combined with non-equilibrium green function (NEGF) calculations. The results indicate Si–Si nanosheets display higher thermoelectric properties due to their higher electrical conductivity and Seebeck coefficient along with lower phonon thermal conductance, leading to the highest ZT. The Ge–Ge nanosheets exhibit moderate thermoelectric performance, while the C–C nanosheets demonstrated are limited by lower electrical conductance. The results offers interesting insights into potential uses of C–C, Ge–Ge, and Si–Si nanosheets as next-generation thermoelectric materials for renewable energy applications.