Influence of copper telluride nanodomains on the transport properties of n-type bismuth telluride.

[Display omitted] • A low temperature approach to produce Bi 2 Te 3 -Cu 2-x Te nanocomposites is presented. • The approach allows a precise control of composition and distribution of phases. • A 250% improvement of the thermoelectric figure of merit is demonstrated. • Results are rationalized taking into account different band structures. The high processing cost, poor mechanical properties and moderate performance of Bi 2 Te 3 –based alloys used in thermoelectric devices limit the cost-effectiveness of this energy conversion technology. Towards solving these current challenges, in the present work, we detail a low temperature solution-based approach to produce Bi 2 Te 3 -Cu 2-x Te nanocomposites with improved thermoelectric performance. Our approach consists in combining proper ratios of colloidal nanoparticles and to consolidate the resulting mixture into nanocomposites using a hot press. The transport properties of the nanocomposites are characterized and compared with those of pure Bi 2 Te 3 nanomaterials obtained following the same procedure. In contrast with most previous works, the presence of Cu 2-x Te nanodomains does not result in a significant reduction of the lattice thermal conductivity of the reference Bi 2 Te 3 nanomaterial, which is already very low. However, the introduction of Cu 2-x Te yields a nearly threefold increase of the power factor associated to a simultaneous increase of the Seebeck coefficient and electrical conductivity at temperatures above 400 K. Taking into account the band alignment of the two materials, we rationalize this increase by considering that Cu 2-x Te nanostructures, with a relatively low electron affinity, are able to inject electrons into Bi 2 Te 3 , enhancing in this way its electrical conductivity. The simultaneous increase of the Seebeck coefficient is related to the energy filtering of charge carriers at energy barriers within Bi 2 Te 3 domains associated with the accumulation of electrons in regions nearby a Cu 2-x Te/Bi 2 Te 3 heterojunction. Overall, with the incorporation of a proper amount of Cu 2-x Te nanoparticles, we demonstrate a 250% improvement of the thermoelectric figure of merit of Bi 2 Te 3. [ABSTRACT FROM AUTHOR]