(438a) Design Principles of Telluride-Based Nanowire Heterostructures for Thermoelectric Applications

Thermoelectric (TE) devices, which can perform a direct conversion between thermal and electrical energy, have attracted great attention due to their promising potential in improving the energy efficiency and in solid-state cooling.However, the low efficiency of the TE materials prohibits their wide applications. Certain TE materials, such as Bi₂Te₃/Sb₂Te₃ superlattice film (ZT~2.4) and AgPb_mSbTe_2+m bulk crystals (ZT~2.2), although possessing high performance due to the improved phonon scattering at nanoscale interfaces and grain boundaries, require very complicated material composition or extremely expensive/time-consuming manufacture process such as molecular beam epitaxy. Theoretical predictions and initial experimental results have suggested that one-dimensional (1D) nanostructures, especially the nanowire heterostructures, which take the advantages of both quantum confinement to enhance the power factor and phonon scattering at nanowire surface and compositional interfaces to lower thermal conductivity, could offer a much higher ZT value. Meanwhile, the syntheses of various 1D nanowire heterostructures have been demonstrated through the chemical vapor deposition process based on vapor-liquid-solid (VLS) growth mechanism as well as the pulsed electrodeposition, but it is still a great challenge to obtain high-quality thermoelectric nanowire heterostuctures at a simple yet scalable way. Here we present a design principle to develop new categories of telluride-based thermoelectric nanowire heterostructures through rational solution-phase reactions. The synthesis yields “barbell” and "dumbbell" compositional-modulated nanowire heterostructures with narrow diameter and length distribution. Initial characterizations of the hot-pressed nanostructured bulk pellets of these heterostructure show a largely enhanced Seebeck coefficient and greatly reduced thermal conductivity, which lead to an improved thermoelectric figure of merit. This approach opens up new platforms to investigate the phonon scattering and energy filtering.