▎ 摘　　要

Thermoelectric materials can convert thermal energy and electrical energy into each other, which have attracted extensive attention in recent years. In this paper, we systematically investigate the ballistic thermoelectric performance of four zigzag graphene-graphyne nanoribbon heterostructures Mi(i = 1-4) through utilizing non-equilibrium Green's function method. Our results show that heterostructures possess superior thermoelectric properties with respect to pristine graphene nanoribbon. Especially, the ZT value of M4 reaches 1.5 at 700 K, which is about 15 times that of graphene. Such improvement mainly originates from the reduction of phononic and electronic thermal conductance and the increase of Seebeck coefficient. Meanwhile, because M4 has the lowest phonon thermal conductance and favorable thermal power, its thermoelectric figure of merit is the best. These findings in this paper demonstrate that heterostructure is a viable approach to optimize the thermoelectric performance of graphene, which provides useful guidance for the design and fabrication of nanoscale thermoelectric devices.