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

The high processing cost, poor mechanical properties and moderate performance of BiTe–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 BiTe-CuTe 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 BiTe nanomaterials obtained following the same procedure. In contrast with most previous works, the presence of CuTe nanodomains does not result in a significant reduction of the lattice thermal conductivity of the reference BiTe nanomaterial, which is already very low. However, the introduction of CuTe 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 CuTe nanostructures, with a relatively low electron affinity, are able to inject electrons into BiTe, 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 BiTe domains associated with the accumulation of electrons in regions nearby a CuTe/BiTe heterojunction. Overall, with the incorporation of a proper amount of CuTe nanoparticles, we demonstrate a 250% improvement of the thermoelectric figure of merit of BiTeThis work was supported by the European Regional Development Funds and by the Generalitat de Catalunya through the project 2017SGR1246. Y.Z, C.X, M.L, K.X and X.H thank the China Scholarship Council for the scholarship support. MI acknowledges financial support from IST Austria. YL acknowledges funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 754411. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project ENE2017-85087-C3. ICN2 is supported by the Severo Ochoa program from the Spanish MINECO (grant no. SEV-2017-0706) and is funded by the CERCA Program/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program