High Thermoelectric Performance of Ge/Si Core−Shell Nanowires: First-Principles Prediction

In an effort to enhance the thermoelectric performance in Si nanowires, we have explored the thermoelectric figure of merit ( ZT ) of the Ge/Si core−shell structured nanowires by using ab initio electronic structure calculations in the framework of Boltzmann transport theory. Our results show that the ZT value of the Ge/Si core−shell nanowire with p-type doping can reach 0.85 at 300 K, significantly larger than the observed ZT value of 0.36 in pure Si nanowires. The underlying mechanism for this enhanced ZT is mainly attributed to the reduced lattice thermal conductivity in the Ge/Si core−shell structure. Moreover, we suggest that appropriate Ge content in the Ge/Si core−shell nanowire may further optimize its ZT value. The current research proposed a way to design high-performance thermoelectric materials through a proper construct of heterostructured materials.