Enhancing the figure of merit of n-type PbTe materials through multi-scale graphene induced interfacial engineering

The intrinsically low thermal conductivity and excellent electrical properties of lead telluride (PbTe) compounds are highly promising for the thermoelectric conversion in intermediate temperature range. However, a problematic issue is that the inferior thermoelectric performance of n-type leg severely restricts the applications of PbTe-based thermoelectric couples. Here we report a highly boosted figure of merit peak value of 1.73 at 843 K in graphene-incorporated n-type PbTe compound. The dramatically improved thermoelectric performance is ascribed to the realization of a multi-scale feature of graphene-induced interfacial decorations distributing along grain boundaries, which creates massive PbTe/graphene interfaces for the manipulation of electron and phonon transport properties. In detail, lattice thermal conductivity is abundantly suppressed by the graphene-induced grain boundary scattering upon low-frequency phonons. Simultaneously, nano-scale graphene precipitates trigger the energy filtering effect, bringing about distinctly enhanced Seebeck coefficient and power factor. The present strategy of implementing high-efficiency interfacial engineering (IE) from graphene additions with multiple scales offers an applicable pathway for fabricating high-performance thermoelectric materials with both optimized thermal and electrical transport properties.