Enhancement of thermoelectric efficiency by embedding hexagonal boron-nitride cells in zigzag graphene nanoribbons

We study thermoelectric properties of zigzag graphene nanoribbon (ZGNR)–boron nitride (BN) junctions coupled to square electrodes using nonequilibrium Green function formalism in the linear response regime. The embedding of hexagonal BN cells into the ZGNR results in the change of the thermoelectric properties with the length and position of BN cells. The influence of the width variation on the electrical conductance and the Seebeck coefficient of the ZGNR–BN junctions is examined. Also, the coupling of asymmetric electrodes to the ZGNR–BN junctions and the pristine ZGNR is considered. It is observed that the asymmetric electrodes lead to the increase of the Seebeck coefficients of both structures, while the phonon thermal conductance is decreased because of the reduction of the phonon transport in inhomogeneous structures. Our results predict that the thermoelectric efficiency of the system is increased by embedding the hexagonal BN cells, as well as coupling to the asymmetric electrodes. (paper)