N-Type Nanocomposite Films Combining SWCNTs, BiTe Nanoplates, and Cationic Surfactant for Pn-Junction Thermoelectric Generators with Self-Generated Temperature Gradient Under Uniform Sunlight Irradiation.

Flexible thermoelectric generators (TEGs) with pn-junction single-walled carbon nanotube (SWCNT) films on a polyimide substrate have attracted considerable attention for energy harvesting. This is because they generate electricity through the photo-thermoelectric effect by self-generated temperature gradient under uniform sunlight irradiation. To increase the performance and durability of the pn-junction TEGs, n-type films need to be improved as a priority.

Stretchable and Flexible Painted Thermoelectric Generators on Japanese Paper Using Inks Dispersed with P- and N-Type Single-Walled Carbon Nanotubes.

As power sources for Internet-of-Things sensors, thermoelectric generators must exhibit compactness, flexibility, and low manufacturing costs. Stretchable and flexible painted thermoelectric generators were fabricated on Japanese paper using inks with dispersed p- and n-type single-walled carbon nanotubes (SWCNTs). The p- and n-type SWCNT inks were dispersed using the anionic surfactant of sodium dodecylbenzene sulfonate and the cationic surfactant of dimethyldioctadecylammonium chloride, respectively.

Determination of Seebeck coefficient originating from phonon-drag effect using Si single crystals at different carrier densities.

The phonon-drag effect is useful for improving the thermoelectric performance, especially the Seebeck coefficient. Therefore, the phonon and electron transport properties of Si single crystals at different carrier densities were investigated, and the relationship between these properties and the phonon-drag effect was clarified. Phonon transport properties were determined using nanoindentation and spot-periodic heating radiation thermometry.

SbTe nanoparticle-containing single-walled carbon nanotube films coated with SbTe electrodeposited layers for thermoelectric applications.

Single-walled carbon nanotubes (SWCNTs) are promising thermoelectric materials owing to their flexibility and excellent durability when exposed to heat and chemicals. Thus, they are expected to be used in power supplies for various sensors. However, their thermoelectric performances are inferior to those of inorganic thermoelectric materials.

High thermoelectric performance of flexible nanocomposite films based on BiTe nanoplates and carbon nanotubes selected using ultracentrifugation.

Thermoelectric generators with flexibility and high performance near 300 K have the potential to be employed in self-supporting power supplies for Internet of Things (IoT) devices. Bismuth telluride (BiTe) exhibits high thermoelectric performance, and single-walled carbon nanotubes (SWCNTs) show excellent flexibility. Therefore, composites of BiTe and SWCNTs should exhibit an optimal structure and high performance.

Ultra-long air-stability of n-type carbon nanotube films with low thermal conductivity and all-carbon thermoelectric generators.

This report presents n-type single-walled carbon nanotubes (SWCNT) films with ultra-long air stability using a cationic surfactant and demonstrates that the n-type Seebeck coefficient can be maintained for more than two years, which is the highest stability reported thus far to the best of our knowledge. Furthermore, the SWCNT films exhibit an extremely low thermal conductivity of 0.62 ± 0.

Heat source free water floating carbon nanotube thermoelectric generators.

Thermoelectric generators (TEGs) produce electric power from environmental heat energy and are expected to play a key role in powering the Internet of things. However, they require a heat source to create a stable and irreversible temperature gradient. Overcoming these restrictions will allow the use of TEGs to proliferate.

Origin of n type properties in single wall carbon nanotube films with anionic surfactants investigated by experimental and theoretical analyses.

We investigated the origin of n-type thermoelectric properties in single-wall carbon nanotube (SWCNT) films with anionic surfactants via experimental analyses and first-principles calculations. Several types of anionic surfactants were employed to fabricate SWCNT films via drop-casting, followed by heat treatment at various temperatures. In particular, SWCNT films with sodium dodecylbenzene sulfonate (SDBS) surfactant heated to 350 °C exhibited a longer retention period, wherein the n-type Seebeck coefficient lasted for a maximum of 35 days.

Flexible thermoelectric films formed using integrated nanocomposites with single-wall carbon nanotubes and BiTe nanoplates via solvothermal synthesis.

Single-wall carbon nanotubes (SWCNTs) and BiTe nanoplates are very promising thermoelectric materials for energy harvesting. When these two materials are combined, the resulting nanocomposites exhibit high thermoelectric performance and excellent flexibility. However, simple mixing of these materials is not effective in realizing high performance.

Self-powered broadband photo-detection and persistent energy generation with junction-free strained BiTe thin films.

We experimentally demonstrate efficient broadband self-powered photo-detection and power generation in thin films of polycrystalline bismuth telluride (BiTe) semiconductors under inhomogeneous strain. The developed simple, junction-free, lightweight, and flexible photo-detectors are composed of a thin active layer and Ohmic contacts on a flexible plastic substrate, and can operate at room temperature and without application of an external bias voltage. We attribute the observed phenomena to the generation of an electric field due to a spontaneous polarization produced by strain gradient, which can separate both photo-generated and thermally-generated charge carriers in bulk of the semiconductor material, without a semiconductor junction.

Facile preparation of air-stable n-type thermoelectric single-wall carbon nanotube films with anionic surfactants.

Thermoelectric generators based on single-wall carbon nanotubes (SWCNTs) have great potential for use in wearable and skin electronics because of their lightweight and mechanically soft structure. However, the fabrication of air-stable n-type thermoelectric SWCNTs using conventional processes is challenging. Herein, we propose a facile process for fabricating air-stable n-type SWCNT films with anionic surfactants via drop casting followed by heat treatment.

Solvothermal synthesis of n-type Bi(SeTe) nanoplates for high-performance thermoelectric thin films on flexible substrates.

To improve thermoelectric performance of materials, the utilization of low-dimensional materials with a multi-alloy system is a promising approach. We report on the enhanced thermoelectric properties of n-type Bi(SeTe) nanoplates using solvothermal synthesis by tuning the composition of selenium (Se). Variation of the Se composition within nanoplates is demonstrated using X-ray diffraction and electron probe microanalysis.

Growth of single-crystalline BiTe hexagonal nanoplates with and without single nanopores during temperature-controlled solvothermal synthesis.

Bismuth telluride (BiTe) is a promising thermoelectric material for applications near room temperature. To increase the thermoelectric performance of this material, its dimensions and thermal transport should be decreased. Two-dimensional nanoplates with nanopores are an ideal structure because thermal transport is disrupted by nanopores.

Effects of different electrolytes and film thicknesses on structural and thermoelectric properties of electropolymerized poly(3,4-ethylenedioxythiophene) films.

The effects of the type of electrolyte and film thickness on the structural and thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films on indium-tin-oxide (ITO) substrates prepared using electropolymerization were investigated. Two electrolytes were prepared using two different solvents: a water/methanol solvent (protic solvent) and acetonitrile (aprotic solvent) with 3,4-ethylenedioxythiophene (EDOT) and LiCFSO, typically included in electrolytes as dopants. The electrochemical properties of the two electrolytes were analyzed; it was found that the polymerization process for EDOT on an ITO substrate varied based on the electrolyte used.

Thermoelectric properties of nanocrystalline SbTe thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size.

The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (SbTe) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The SbTe thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the SbTe thin films, thermal annealing was performed at different temperatures.

Structural, optical, and transport properties of nanocrystalline bismuth telluride thin films treated with homogeneous electron beam irradiation and thermal annealing.

We investigated the effects of homogeneous electron beam (EB) irradiation and thermal annealing treatments on the structural, optical, and transport properties of bismuth telluride thin films. Bismuth telluride thin films were prepared by an RF magnetron sputtering method at room temperature. After deposition, the films were treated with homogeneous EB irradiation, thermal annealing, or a combination of both the treatments (two-step treatment).