Abstract
Increasing the Seebeck coefficient S in thermoelectric materials usually drastically decreases the electrical conductivity σ, making significant enhancement of the thermoelectric power factor σS2 extremelly challenging. Here we predict, using first-principles calculations, that the extraordinary properties of charged ferroelectric domain walls (DWs) in GeTe enable a five-fold increase of σS2 in the DW plane compared to bulk. The key reasons for this enhancement are the confinement of free charge carriers at the DWs and Van Hove singularities in the DW electronic band structure near the Fermi level. These effects lead to an increased energy dependence of the DW electronic transport properties, resulting in more than a two-fold increase of S with respect to bulk, without considerably degrading the in-plane σ. We propose a design of a nano-thermoelectric device that utilizes the exceptional thermoelectric properties of charged ferroelectric DWs. Our findings should inspire further investigation of ferroelectric DWs as efficient thermoelectric materials.
Highlights
Thermoelectric materials can convert waste heat into electrical power or, in reverse, cool devices using electrical current
We report a prediction that the thermoelectric power factor in the plane of ferroelectric domain walls (DWs) in germanium telluride (GeTe) can be up to five times larger than that of bulk GeTe
To harness the predicted outstanding thermoelectric properties of ferroelectric DWs, we propose a nano-thermoelectric device consisting of H-H and T-T DWs acting as n-type and p-type legs of the thermoelectric couple[50], separated by electrically insulating domains
Summary
Thermoelectric materials can convert waste heat into electrical power or, in reverse, cool devices using electrical current. We will show that a large enhancement of power factor could be realized in a novel class of thermoelectric materials: ferroelectric domain walls (DWs). Several normally insulating perovskite materials show conductive behaviour at DWs14–20, with the electrical conductivity of DWs up to 13 orders of magnitude larger than that in the domains[21]. These discoveries have lead to a new paradigm of ferroic devices where DWs, rather than domains, are active elements in nanoelectronic circuits[13], such as diodes[22], rectifiers[23], resistive memories[24,25], and memristors[26]. Despite over a decade of research of the DW conductive properties, the idea that their thermoelectric properties may be superior to those of bulk has not been considered
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