Systematic Enhancement of Thermoelectric Figure of Merit in Edge-Engineered Nanoribbons

Nanomaterials provide unique promise to thermoelectric energy conversion owing to their possible phonon confinement and reduced thermal conductivity. These effects can, in particular, occur in nanoribbons upon edge-engineering. Here, we study graphene, boron nitride, and silicene chevron nanoribbons (CNRs) because of their high edge-length to surface area ratio to assess phonon boundary scattering effects on improving the thermoelectric figure of merit (ZT). The ab initio based nonequilibrium Green's function method is utilized to calculate quantum electronic and phononic thermal conductance, electrical conductance, and Seebeck coefficient. Our results show that, compared to straight nanoribbons, ZT in CNRs is systematically enhanced. Detailed contributions to CNRs' ZT for different geometries and materials are analyzed, in particular, separation of electrical and electron-contributed thermal conductance versus chemical potential. Taking the corresponding recent fabrications into account, edge-engineering of nanoribbons is shown to provide a possible strategy for achieving competitive thermoelectric energy conversion.