Synergistical Tuning Interface Barrier and Phonon Propagation in Au–Sb₂Te₃ Nanoplate for Boosting Thermoelectric Performance

Abstract

Engineering of low-dimensional metal–semiconductor nanocomposites is expected to decouple electrical and thermal property, leading to substantially higher thermoelectric property. In this study, we rationally design a unique 0D–2D Au–Sb2Te3 architecture with beneficial interface barrier and strengthened phonon scattering, resulting in synergistically optimized electrical and thermal properties. In-situ growth of Au nanoparticles ∼10 nm on Sb2Te3 nanoplates enables better manipulation of electron and phonon transport compared to traditional bulks. The energy barrier between Au and Sb2Te3 effectively filters low-energy holes, while the Au nanoparticles competently hinder the propagation of midto-long wavelength phonons. As a result, this unique 0D–2D Au–Sb2Te3 composite exhibits a concurrent increase in electrical conductivity and Seebeck coefficient, and a decrease in lattice thermal conductivity, which allows a double of ZT value (∼0.8 at 523 K) for 1 mol % Au–Sb2Te3 composites with respect to the pristine Sb2Te3 (∼0.39 at 523 K). This self-assembled heterostructure provides a direction to design other low-dimensional metal–semiconductor nanoassemblies for thermoelectric application.

Current State‐of‐the‐Art in the Interface/Surface Modification of Thermoelectric Materials

“…Increasing the Au concentration (4 mol%) will cause an increase in the size of the distributed particles (≈40 nm) and, in turn, an agglomeration of Au QDs. [ 91 ] By applying the classical percolation power law, while controlling the content/size/distribution of QDs, the zT value can reach a maximum of 0.8 if a 1.08 mol% Au solution is used (Figure 4d).…”

“…a) Illustration of the QDs structure in the matrix; b) Schematic diagram of the quantum confinement of the electron wave functions; c) Scanning electron microscopy (SEM) image of pure Sb 2 Te 3 and Au QDs‐Sb 2 Te 3 composites with an Au mole ratio of 1, 2, 4 mol; d) Comparison of experimental and theoretical zT value of an Au QDs‐Sb 2 Te 3 system using the percolation theory at 300 K. [ 91 ] Reproduced with permission. [ 91 ] Copyright 2019, American Chemical Society.…”

“…Although the benefits of adding a second phase have been extensively documented, there are certain issues that need be investigated further through experimentation. 1)Reduced metal particle size may result in a lower metal melting point, which may cause the diffusion of metal into the matrix and give an additional carrier. As a result, it is difficult to differentiate the increase in carrier produced from metal–semiconductor contact from the diffusion effect, as observed for Au‐Bi 2 Te 3 [ 65,91 ] and Au‐Sb 2 Te 3 . [ 91 ] To confirm the source of TE property variation, a comparison of the dispersion and doping methods on the TE properties is required.…”

“…As a result, it is difficult to differentiate the increase in carrier produced from metal–semiconductor contact from the diffusion effect, as observed for Au‐Bi 2 Te 3 [ 65,91 ] and Au‐Sb 2 Te 3 . [ 91 ] To confirm the source of TE property variation, a comparison of the dispersion and doping methods on the TE properties is required. Furthermore, when the TE matrix has extremely poor electrical conductivity, it is difficult to significantly improve overall electrical conductivity, even with metal particle dispersion, as seen in the Ag–Ca 3 Co 4 O 9 [ 237 ] and Au–ZnO systems.…”

Modifying the Thermoelectric Transport of Sb2Te3 Thin Films via the Carrier Filtering Effect by Incorporating Size-Selected Gold Nanoparticles

“…Faleev and Léonard investigated the enhancement in the Seebeck coefficient by energy-dependent carrier scattering at the metal–semiconductor interface. The carrier filtering approach has been experimentally implemented in several state-of-the-art TE materials such as PbTe, , Bi 2 Te 3 , Sb 2 Te 3 , , SnTe, and so forth by incorporating suitable NPs. Although the energy filtering effect has been successfully demonstrated in the systems mentioned above, it still suffers from a lack of control over nanoparticle (NP) dimension, size distribution, crystallinity, and so forth, which are particularly important for an optimized power factor and to minimize the thermal conductivity.…”