Thermoelectric properties of graphene with grain boundaries.

As common defects in graphene, grain boundaries scatter phonons and charge carriers, leading to decreases in thermal conductivity and electrical conductivity. However, the thermoelectric transport parameters exhibit different sensitivities to grain boundaries. Therefore, regulating the thermoelectric properties of polycrystalline graphene via grain boundaries is considered to be a potentially effective way to improve the thermoelectric conversion efficiency of graphene. In this study, the effects of different grain boundary settings on the lattice thermal conductivity of graphene are studied by using homogeneous nonequilibrium molecular dynamics. Furthermore, the grain boundary types that are most likely to result in a high thermoelectric figure of merit are selected. The linear-scaling quantum transport method is used to further study the effect of the selected grain boundaries on the electrical conductivity of graphene and the ability to control the thermoelectric figure of merit. The results show that the existence of grain boundaries can significantly improve the thermoelectric figure of merit of graphene for the low thermal conductivity configurations.