3D Bi₂Te₃ Interconnected Nanowire Networks to Increase Thermoelectric Efficiency

Abstract

3D interconnected nanowire scaffoldings are shown to increase the thermoelectric efficiency in comparison to similar diameter 1D nanowires and films grown under similar electrodeposition conditions. Bi 2 Te 3 3D nanonetworks offer a reduction in thermal conductivity (κ T ) while preserving the high electrical conductivity of the films. The reduction in κ T is modeled using the hydrodynamic heat transport equation, and it can be understood as a heat viscosity effect due to the 3D nanostructuration. In addition, the Seebeck coefficient is twice that of nanowires and films, and up to 50% higher than in a single crystal. This increase is interpreted as a nonequilibrium effect that the geometry of the structure induces on the distribution function of the phonons, producing an enhanced phonon drag. These thermoelectric metamaterials have higher performance and are fabricated with large areas by a cost-effective method, which makes them suitable for up-scale production.

Universal Behavior of Highly Confined Heat Flow in Semiconductor Nanosystems: From Nanomeshes to Metalattices

“…To develop a comprehensive theory predicting the measured κ in both the metalattice and a broader class of highly confined nanostructured systems, ,, we combine a phonon hydrodynamics framework and the theory of rarefied gas dynamics in porous media. , Previous work has demonstrated that nanoscale size and frequency effects on heat transport in silicon can be modeled in terms of nonlocal and memory effects, as described by the Guyer–Krumhansl equation (GKE), with ab initio geometry-independent coefficients. ,,, However, the predictive capabilities of this hydrodynamic-like approach are restricted to systems with dimensions sufficiently large compared to the average bulk phonon MFP, since nanoscale confinement modifies the ab initio phonon properties used to determine the GKE coefficients. , This excludes the present metalattice and a broader class of nanostructured silicon materials.…”

Plasmon Resonances in 1D Nanowire Arrays and 3D Nanowire Networks of Topological Insulators and Metals

“…In the case of nickel ( Figure A1 b), the diffraction pattern obtained for the three different nanostructures show only peaks corresponding to the face-centered cubic (FCC) structure, demonstrating that it is a polycrystalline material. It is worth mentioning here that these kinds of nanostructures have already been fabricated and measured in previous works of our group (see, for instance, [ 33 , 35 , 36 , 39 , 40 ]), which has the expertise of controlling the growth parameters in such a way that the nanostructures obtained are highly reproducible.…”

“…Despite the different origins of the plasmon capabilities of the two materials, the results indicate that the optical response is determined by plasmon resonances, whose position depends on the nanowire interactions and material properties. Furthermore, given that Bi 2 Te 3 3D nanowire networks outperform their bulk or thin film counterparts regarding their thermoelectric efficiency [ 40 ] and that these metamaterials can be used to fabricate miniaturized thermoelectric generators, where establishing a thermal gradient can be challenging, the possibility of obtaining an additional localized temperature increase by using these plasmon resonances would result in an increase in the final power output. In our case, the light confinement produced by the plasmonic resonance in the Bi 2 Te 2 1D and 3D nanostructures would increase the effective thermal gradient in the material, and thus, increase the thermoelectric power output obtained in the nanostructured material.…”

Multifunctional Irradiation-Induced Defects for Enhancing Thermoelectric Properties of Scandium Nitride Thin Films

“…However, due to its promising thermoelectric properties, ScN is much desired in recent times. The ScN thin films exhibit a high thermoelectric power factor of (2–3.5) × 10 –3 W/(m·K 2 ) in the 600–840 K temperature range that is higher than the power factor of most well-established thermoelectric materials such as Bi 2 Te 3 , Bi 2 Se 3 , and PbTe. − Such a high power factor in ScN arises from its high electron concentration in the (1–5) × 10 20 cm –3 range due to the presence of unwanted impurities such as oxygen and possible nitrogen vacancies. − Molecular beam epitaxy (MBE) and sputter-deposited ScN films also exhibit moderately large mobility in the 90–120 cm 2 /(V·s) range. , However, the highest mobility of 284 cm 2 /(V·s) is reported in hybrid vapor phase epitaxy (HVPE)-deposited ScN films . Mg–hole doping has been used recently to reduce the carrier concentration in ScN, and p-type ScN films with a large Seebeck coefficient are demonstrated. , X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS) measurements have shown that both the unwanted n-type oxygen impurity and p-type Mg–hole doping do not introduce defect states inside the band gap, and the rigid band electronic structure remains unchanged with respect to the dopant introduction. , …”