Thermoelectric Layers Research Articles

Electrospun biomass polyethylene furanoate nonwoven substrates for flexible thermoelectric generators

Polyethylene furanoate (PEF) stands out as a highly promising biopolymer, characterized by its lower melting point and higher flexibility than those of polyethylene terephthalate (PET). Moreover, the enhanced functionality of PEF broadens its potential applications across various domains. Herein, the synergistic integration of PEF with a polymer thermoelectric layer is explored via the formulation of advanced environmentally sustainable materials for prospective utilization in flexible thermoelectric generators for the emerging field of green energy. The fabrication process involves the creation of PEF nonwoven via the electrospinning technique, thereby endowing the PEF with considerable stretchability. Concurrently, the polymer thermoelectric layer is developed by blending dimethyl sulfoxide (DMSO) and d-sorbitol in a poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) solution, followed by drop-casting PEDOT:PSS onto glass substrates. Subsequently, free-standing PEDOT:PSS films are transposed onto PEF nonwoven substrates with a power factor of 17.84 μW m⁻1 K⁻2 and an elongation of 24 % at breaking point. The intimate compatibility between the PEDOT:PSS film and PEF nonwoven substrate is demonstrated by the cyclic bending test results, wherein over 90 % of the original conductivity is maintained after 1000 cycles, thereby highlighting the potential of the developed device as a thermoelectric generator. Finally, a 12-leg thermoelectric generator is fabricated, yielding an output voltage of 3.63 mV and an output power of 34.52 nW under a temperature gradient of 32.3 K.

How Plasmon Ag Nanoparticles can Enhance the Power Performance of a Thermoelectric Generator.

The development of wearable thermoelectric generators (wTEG) represents a promising strategy to replace batteries and supercapacitors required to supply electrical energy for portable electronic devices. However, the main drawback of wTEGs is that the thermal gradient between the skin and the ambient is minimal, reducing the power output produced by the generator. Therefore, it is necessary to improve the thermal management of wTEG in order to increase its efficiency. This work deals with the preparation of a thermoelectric generator that harnesses the plasmonic heating effect to enhance the thermal gradient of the final device. The thermoelectric layer is created through the in situ polymerization of terthiophene (3T) within a polyurethane matrix, utilizing silver (Ag) (I) and copper (II) perchlorate as oxidants. The plasmonic film, composed of Ag-NP (nanoparticles), is formed via photocatalytic reduction of silver nitrate in the presence of titanium oxide. These layers are then meticulously assembled to yield the hybrid plasmonic/thermoelectric generator.

A dual function flexible sensor for independent temperature and pressure sensing

Temperature and pressure sensing are two primary goals of bionic electronic skin. In this work, we developed a dual function flexible sensor, which achieved independent temperature and pressure sensing, with easy fabrication and without complicate signal decoupling. For this sensor, two flexible films with conductively bionic microstructure on the surface are combined face to face, which were replicated from rose petal and mulberry leaf. Ti3C2Tx nanoflakes were mixed with PEDOT: PSS as conductive layer and thermoelectric layer, and the performance of which can be optimized by regulating the concentration of Ti3C2Tx. The principles for temperature and pressure sensing are thermoelectric and piezo-resistive respectively, which are isolated by structure design. The change of contact area and resistance between the two micro-structured layers upon pressure determines the pressure response of the device. The thermoelectric response in one layer realizes the temperature sensing. The metallic conductivity of Ti3C2Tx is insensitive to temperature, leading to the invariable electric response to pressure upon varied temperature. The microstructure buffers most of the pressure, which keeps the substrate unchanged and results in the independent thermoelectric response upon varied pressure. This dual function sensor shows robust and repeatable response, and exhibits great application potential in flexible electronics.

Chiral photothermoelectric effect driven by high-Q quasi-bound states in the continuum

Bound states in continuum (BIC) have been proposed as a means to efficiently improve light-matter interactions in metasurfaces. While breaking the mirror symmetry of structure and developing BIC into a reachable and observable quasi-BIC, it is usually accompanied by the chiral phenomenon with high quality (Q) factor. Here, we report a spin-sensitive photodetector in the infrared (NIR) region comprising a silicon metasurface with chiral quasi-BIC, a silver layer, and a thermoelectric layer. A chiral quasi-BIC supported by a silicon metasurface can be realized under normal incidence. Based on finite element method simulations, a silicon metasurface with a silver layer shows a high Q-factor of 958.6 with a giant absorption circular dichroism of 0.83. Subsequently, we study the thermal performance of the chiral absorbers by using the heat transfer module of COMSOL. Combined with the thermoelectric material bismuth telluride, we calculate the differential photothermoelectric effects of the system under circular-polarized light irradiation. When the incident flux is 100 W cm−2, the output voltage under right-circular-polarization (left-circular-polarization) light reaches 0.59 mV (0.08 mV), which can be used for polarization detection. Therefore, our designed structure incorporating thermoelectricity broadens the applications of chiral BIC in sensors and detectors.

Direct-Contact Seebeck-Driven Transverse Magneto-Thermoelectric Generation in Magnetic/Thermoelectric Bilayers.

Transverse thermoelectric generation converts temperature gradient in one direction into an electric field perpendicular to that direction and is expected to be a promising alternative in creating simple-structured thermoelectric modules that can avoid the challenging problems facing traditional Seebeck-effect-based modules. Recently, large transverse thermopower has been observed in closed circuits consisting of magnetic and thermoelectric materials, called the Seebeck-driven transverse magneto-thermoelectric generation (STTG). However, the closed-circuit structure complicates its broad applications. Here, STTG is realized in the simplest way to combine magnetic and thermoelectric materials, namely, by stacking a magnetic layer and a thermoelectric layer together to form a bilayer. The transverse thermopower is predicted to vary with changing layer thicknesses and peaks at a much larger value under an optimal thickness ratio. This behavior is verified in the experiment, through a series of samples prepared by depositing Fe-Ga alloy thin films of various thicknesses onto n-type Si substrates. The measured transverse thermopower reaches 15.2 ± 0.4µVK-1, which is a fivefold increase from that of Fe-Ga alloy and much larger than the current room temperature record observed in Weyl semimetal Co2MnGa. The findings highlight the potential of combining magnetic and thermoelectric materials for transverse thermoelectric applications.

Environmental and energy assessment of photovoltaic-thermal system combined with a reflector supported by nanofluid filter and a sustainable thermoelectric generator

This study focuses on new design of a photovoltaic-thermal (PVT) unit through the utilization of a cylindrical reflector. The integration of a thermoelectric generator layer fabricated from Cu2SnS3 (CTS) and a nanofluid spectral filter composed of a MgO-water mixture within PVT leads to performance enhancement. A mathematical approach was established involving optical features and the Finite volume approach was employed for simulation. The validity of the method was verified through comparison with experimental data. By introducing fins and a filter duct, along with a cylindrical reflector, the overall performance is enhanced by 36.3%. Adding a reflector into the finned structure leads to an overall performance improvement of approximately 5.7% and 4.7% with and without a nanofluid filter. By increasing the velocity of the filter, the electrical performance was enhanced resulting in an improvement of 37.7% when a reflector is present. Integrating a reflector, fins and filter in a combined system leads to the maximum reduction in CO2 emission with a value 2 times higher than that of conventional PV.

Thermoelectric Sensor with CuI Supported on Rough Glass.

Thermoelectric generators convert heat into a potential difference with arrays of p- and n-type materials, a process that allows thermal energy harvesting and temperature detection. Thermoelectric sensors have attracted interest in relation to the creation of temperature and combustible gas sensors due to their simple operation principle and self-powering ability. CuI is an efficient p-type thermoelectric material that can be readily produced from a Cu layer by an iodination method. However, the vapor iodination of Cu has the disadvantage of weak adhesion on a bare glass substrate due to stress caused by crystal growth, limiting microfabrication applications of this process. This work presents a rough soda-lime glass substrate with nanoscale cavities to support the growth of a CuI layer, showing good adhesion and enhanced thermoelectric sensitivity. A rough glass sample with nanocavities is developed by reactive ion etching of a photoresist-coated glass sample in which aggregates of carbon residuals and the accumulation of NaF catalyze variable etching rates to produce local isotropic etching and roughening. A thermoelectric sensor consists of 41 CuI/In-CoSb3 thermoelectric leg pairs with gold electrodes for electrical interconnection. A thermoelectric leg has a width of 25 μm, a length of 3 mm, and a thickness of 1 μm. The thermoelectric response results in an open-circuit voltage of 13.7 mV/K on rough glass and 0.9 mV/K on bare glass under ambient conditions. Rough glass provides good mechanical interlocking and introduces important variations of the crystallinity and composition in the supported thermoelectric layers, leading to enhanced thermopower.

Photothermoelectric Synergistic Hydrovoltaic Effect: A Flexible Photothermoelectric Yarn Panel for Multiple Renewable-Energy Harvesting.

The human body is in a complex environment affected by body heat, light, and sweat, requiring the development of a wearable multifunctional textile for human utilization. Meanwhile, the traditional thermoelectric yarn is limited by expensive and scarce inorganic thermoelectric materials, which restricts the development of thermoelectric textiles. Therefore, in this paper, photothermoelectric yarns (PPDA-PPy-PEDOT/CuI) using organic poly(3,4-ethylenedioxythiophene) (PEDOT) and inorganic thermoelectric material cuprous iodide (CuI) are used for the thermoelectric layer and poly(pyrrole) (PPy) for the light-absorbing layer. With the introduction of PPy, the temperature difference of the photothermoelectric yarn can be increased for a better voltage output. Subsequently synergizing the photothermoelectric effect with the hydrovoltaic effect to create higher electric potentials, a single wet photothermoelectric yarn obtained by preparation can be irradiated under an infrared lamp at a voltage of up to 0.47 V. Finally, the photothermoelectric yarn PPDA-PPy-PEDOT/CuI was assembled in a series and parallel to obtain a photothermoelectric yarn panel, which was able to output 41.19 mV under an infrared lamp, and the synergistic photothermoelectric and hydrovoltaic effects of the photothermoelectric panel were tested outdoors on human body, and we found that the voltage was able to reach approximately 0.16 V under sunlight. Therefore, the voltage values obtained from the photothermoelectric yarns in this study are competitive and provide a new research idea for the study of photothermoelectric yarns.

Investigation of solar photovoltaic-thermoelectric system for building unit in presence of helical tapes and jet impingement of hybrid nanomaterial

Solar photovoltaic must be equipped with a cooling unit to gain thermal performance and in present research, a new configuration of unit for photovoltaic-thermal has been presented. To enhance the electrical performance, a thermoelectric layer has been attached above the absorber. Two regions for hybrid nanofluid flow exist within the system including a circular duct equipped with a turbulator and mini channel equipped with jet impingement. The regimes of both zones are laminar and single phase formulation for properties of hybrid nanomaterial has been utilized. With selecting the turbulator with the greatest level of revolution, the electrical efficiency enhances about 1.41% and useful heat enhances about 5.72%. The amount of performance factor for the case with highest revolution is 1.25 which means the good hydrothermal performance. The mentioned case has been equipped with confined jets and the amount of electrical and thermal performance of the best case reaches 15.50% and 85.30%. The temperature uniformity of the new design improves about 46.89%.

Concentrated solar photovoltaic cell equipped with thermoelectric layer in presence of nanofluid flow within porous heat sink: Impact of dust accumulation

Solar cell performance has been enhanced by means of a cooling system involving nanofluid jet impingement. A thermoelectric module has been located beneath the Tedlar layer resulting in greater electrical output. MWCNT nanoparticles were added to water as a testing fluid. The nanoparticles were concentrated up to a maximum value of 0.036, to achieve a homogenous mixture. To scrutinize the influence of dust accumulation on the performance of the unit, the transmissivity of glass was calculated based on dust density. Different concentration ratios (CR) were examined to assess their influence on the system's performance using Fresnel lenses in the setup. To further enhance the performance, the unit was tested both without (1) and with (2) pin fins. With the increase of CR from 2 to 14, the PV efficiency reduces by around 26.15% and 25.31% for cases 1 and 2, respectively. The value of TE efficiency for case 2 with CR=14 is 4.16 times greater than that with CR=2. The thermal efficiency of case 1 enhances by 4.8% with the growth of CR. For case 1, the improvement in PV, TE and thermal efficiencies is about 1.42%, 8.48% and 0.91%, respectively, with applying porous zones. Also, the temperature uniformity contributes a further 8.05% improvement. Thermal, TE and PV efficiency decrease respectively by about 7.69%, 12.11% and 26.47%, with an increase in dust density from 0 to 7.2 for case 2.

Multiple fields generated by two dissimilar conductive punches on thermoelectric material

Exposed to high load concentrations environments such as mechanical, thermal, and electrical, thermoelectric equipment may be damaged by the contact surface during operation, resulting in equipment failure. The effects of two dissimilar rigid punches on the thermoelectric material layer under mechanical force and thermoelectric loading are investigated in this article. Using the Fourier transform, the problem is turned into a system of three singular integral equations containing the thermoelectric effect, and the collocation methods are used to solve it numerically. The effects of thermoelectric load, thermoelectric material layer thickness, and the distance between two punches on the electric current density, energy flux, and surface normal stress distribution are thoroughly discussed. The results show that when the two punches are close to each other, below the two punches, the electric current density, energy flux, and contact stress values are larger near the distal end and lower at the inner edge. The stresses at the inner edge of the two indices show opposite characteristics with an increasing of total energy flow and total current, whereas they are consistent at the outer edge. The results aid in the measurement of the multifield coupling properties of finite-thickness thermoelectric material using indenter experiments.

Investigation of solar Photovoltaic cell utilizing hybrid nanofluid confined jet and helical fins for improving electrical efficiency in existence of thermoelectric module

One of the choices for improving the productivity of a PVT solar unit is selecting a more effective cooling unit. To reach the better configuration of cooling technique, the circular tube has been equipped with helical fins in current study. Also, the confined jet has been considered in the bottom of the PVT system. The existence of a thermoelectric layer under the Tedlar layer makes the electrical performance increase. The testing fluid consists of the mixture of water and ND-Co3O4. The regime of flow in both duct and heat sink is laminar and the properties of testing fluid were predicted according to homogeneous mixture. The validation step showed that present code has good accuracy with published experimental data. Among various scrutinized configurations of fins, the best performance obtained for the case with four fins and nine revolutions. Although such configuration makes the overall efficiency to increase about 9.12%, it should be evaluated in view of pressure drop with calculating performance evaluation coefficient (PEC). The value of PEC of best case is about 5.4 which means that it is logical to use such configuration. Combining the jet with the best configuration of cooling duct makes the temperature uniformity and overall performance to increase about 62.38% and 10.58%.

Efficiency improvement of ternary nanofluid within a solar photovoltaic unit combined with thermoelectric considering environmental analysis

Impacts of environmental parameters and dust deposition on the efficiency of solar panel have been scrutinized in this article. To gain thermal output, trapezoidal cooling channel has been attached in the bottom of the panel incorporating ternary nanofluid. To produce working fluid, water has been mixed with Fe3O4TiO2GO nanoparticles. Also, the arrangement of fins has been considered to grow the cooling rate of the silicon layer. The existence of a thermoelectric layer above the cooling channel leads to higher electrical output. Efficacy of ambient temperature (Ta), speed of wind (Vwind) and inlet temperature (Tin) and velocity (Vin) of ternary nanofluid on performance of PVT has been assessed. As Tin increases, electrical efficiency declines about 3.63%. Increase of ambient temperature makes thermal performance enhance about 33.46%. The PVT efficiency decreases about 13.14% and 16.6% with augment of wind speed and dust deposition. CO2 mitigation has been uced about 15.49% in presence of dust while it increases about 17.38% with growth of ambient temperature.

High-performance integrated chip-level thermoelectric device for power generation and microflow detection

Miniaturized thermoelectric devices (TED) possess great benefits in energy converting and sensing. By employing improved microfabrication technology, we succeed made an ultra-highly integrated TED with enhanced interfacial and structural qualities at a high filling factor of 61 %. Our micro-TED (2 cm × 2 cm×6 µm, 10,082 TE pairs) achieved an open-circuit voltage up to 2.6 V, an output power of 1.2 mW (temperature difference of 62.8 K). The micro-TED delivered a large temperature gradient up to ∼600 K/mm with input current, achieving a net cooling temperature of 3.6 K with a 3 µm thick thermoelectric layer. As a novel microflow sensor, micro-TED can distinguish ultra-slow cold/hot airflows down to 4 mm/s. The ultra-thin integrated micro-TED can find multi-featured applications in ultra-low-grade thermal energy harvesting, localized chip-to-chip cooling, and hypersensitive sensing.

Interlaminar mechanical performance of a multi-layered photovoltaic-thermoelectric hybrid device

A concentrated photovoltaic-thermoelectric hybrid device made up of a six-layer composite structure is considered. The hybrid device is composed of, from top to bottom, photovoltaic cell, ethylene vinyl acetate (EVA) layer, tedlar polyester tedlar (TPT) layer, ceramic layer, electrode, and thermoelectric legs. Under the service condition, the poor interlaminar mechanical performance of the hybrid device induced by the high interlaminar stresses level can give rise to very poor power generation performance. To understand this, an analytical model is built to study the influence of the thermal contact resistance and interfacial slip stiffness on the interlaminar stresses of the hybrid device. In particular, effects of the material parameters and geometric dimensions of the hybrid device are also studied by using the state space method. It is found that the thermal contact resistance mainly affects the interlaminar stresses of the photovoltaic module. The interlaminar stresses without considering the temperature-dependent material properties are greater than the actual stresses. The highest interlaminar shearing stress appears at the lower surface of the photovoltaic cell and the maximum peeling stress occurs at the interface between the EVA layer and TPT layer. A lower interfacial slip stiffness is conducive to reducing the interlaminar stresses. The interlaminar stresses decrease with decreasing elastic modulus and coefficient of thermal expansion of the EVA layer. In addition, a thinner thermoelectric layer contributes to lower the interlaminar stresses. The results offer helpful suggestions for the optimization of the interlaminar mechanical performance of the hybrid device.

Sb2Te3 nanoparticle-containing single-walled carbon nanotube films coated with Sb2Te3 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. To improve the thermoelectric performance while maintaining the excellent characteristics of SWCNTs, a novel approach to form inorganic thermoelectric layers on the SWCNT bundle surfaces using electrodeposition is proposed. We synthesized Sb2Te3 nanoparticle-containing SWCNT films and coated them with electrodeposited Sb2Te3 layers. The Sb2Te3 nanoparticles were synthesized via a spontaneous redox reaction, which were then added to a SWCNT dispersion solution, and films were produced via vacuum filtration. At higher nanoparticle contents in the films, the Sb2Te3 electrodeposited layers completely covered the SWCNT bundles owing to the increase in the concentration of precursor ions near the SWCNT bundle surface, which in turn was the result of melted nanoparticles. The thermoelectric performance improved, and the maximum power factor at approximately 25 °C was 59.5 µW/(m K2), which was 4.7 times higher than that of the normal SWCNT film. These findings provide valuable insights for designing and fabricating high-performance flexible thermoelectric materials.

Investigation of innovative cooling system for photovoltaic solar unit in existence of thermoelectric layer utilizing hybrid nanomaterial and Y-shaped fins

Perhaps the foremost issue of Photovoltaic (PV) cells is the lack of an enhanced cooling system and present work aims to offer a new configuration of system utilizing numerical approach. To increase electrical output, a new layer for thermoelectric has been added at the bottom of the Tedlar layer. The cooling system contains cooling ducts and confined jets and working fluid in both zones are hybrid nanofluid. The duct has been made with three shapes (circular, triangular and 3-lobed) and to enhance the convective rate, Y-shaped fins were installed within the ducts. Numerical method was applied for simulation of the present model which involves laminar flow in both fluid zones. Previous empirical and numerical data have been compared with outputs of present simulation and good accommodation proves that this code can be applied for present complex systems. Utilizing hybrid nanomaterial inside both zones instead of water makes the useful heat increase and cells become cooler. Regarding various configurations, the best performance has been reported for triangular duct equipped with fins and in existence of jet and its overall performance is 9.97% greater than that of circular pipe. Also, the amount of performance evaluation coefficient (PEC) for such a system is about 2.4 which means that such configuration has good hydrothermal performance. Considering the best case instead of a circular duct, the electrical and thermal performances enhance about 2.95% and 11.34%.

Mid-infrared circular-polarization-sensitive photodetector based on a chiral metasurface with a photothermoelectric effect.

Photothermoelectric conversion in chiral metasurfaces with thermoelectric material provides an effective way to achieve circular polarization recognition. In this paper, we propose a circular-polarization-sensitive photodetector in a mid-infrared region, which is mainly composed of an asymmetric silicon grating, a film of gold (Au), and the thermoelectric B i 2 T e 3 layer. The asymmetric silicon grating with the Au layer achieves high circular dichroism absorption due to a lack of mirror symmetry, which results in a different temperature increasing on the surface of the B i 2 T e 3 layer under right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) excitation. Then the chiral Seebeck voltage and output power density are obtained, thanks to the thermoelectric effect of B i 2 T e 3. All the works are based on the finite element method, and the simulation results are conducted by the Wave Optics module of COMSOL, which is coupled with the Heat Transfer module and Thermoelectric module of COMSOL. When the incident flux is 1.0W/c m 2, the output power density under RCP (LCP) light reaches 0.96m W/c m 2 (0.01m W/c m 2) at a resonant wavelength, which achieves a high capability of detecting circular polarization. Besides, the proposed structure shows a faster response time than that of other plasmonic photodetectors. Our design provides a novel, to the best of our knowledge, method for chiral imaging, chiral molecular detection, and so on.

Remarkable Electrical Conductivity Increase and Pure Metallic Properties from Semiconducting Colloidal Nanocrystals by Cation Exchange for Solution-Processable Optoelectronic Applications.

The authors report a strategic approach to achieve metallic properties from semiconducting CuFeS colloidal nanocrystal (NC) solids through cation exchange method. An unprecedentedly high electrical conductivity is realized by the efficient generation of charge carriers onto a semiconducting CuS NC template via minimal Fe exchange. An electrical conductivity exceeding 10 500 S cm-1 (13 400 S cm-1 at 2 K) and a sheet resistance of 17 Ω/sq at room temperature, which are among the highest values for solution-processable semiconducting NCs, are achieved successfully from bornite-phase CuFeS NC films possessing 10% Fe atom. The temperature dependence of the corresponding films exhibits pure metallic characteristics. Highly conducting NCs are demonstrated for a thermoelectric layer exhibiting a high power factor over 1.2mW m-1 K-2 at room temperature, electrical wires for switching on light emitting diods (LEDs), and source-drain electrodes for p- and n-type organic field-effect transistors. Ambient stability, eco-friendly composition, and solution-processability further validate their sustainable and practical applicability. The present study provides a simple but very effective method for significantly increasing charge carrier concentrations in semiconducting colloidal NCs to achieve metallic properties, which is applicable to various optoelectronic devices.

An Eshelby inclusion in a nonlinearly coupled thermoelectric bi‐material and tri‐material

AbstractWe first derive an analytic solution to Eshelby's problem concerning a circular inclusion within one of two perfectly bonded nonlinearly coupled thermoelectric half‐planes. The inclusion undergoes a prescribed uniform electric current‐free thermoelectric potential gradient and a prescribed uniform energy flux‐free temperature gradient. Closed‐form expressions for the six analytic functions characterizing the thermoelectric fields of electric current density and energy flux in all three phases of the composite are obtained primarily with the aid of analytic continuation. A general method is then proposed for the analytic solution of Eshelby's problem of an inclusion of arbitrary shape in a nonlinearly coupled thermoelectric bi‐material. Finally, we extend our ideas to the case of a tri‐material by developing an analytic solution to the thermoelectric problem associated with a circular Eshelby inclusion in a nonlinearly coupled thermoelectric tri‐material composed of two semi‐infinite thermoelectric media bonded together through an intermediate thermoelectric layer of finite thickness.