Flexible Thermoelectric Films Research Articles

High Performance of n-Type Silver Telluride Nanoparticle-Embedded Nylon Membrane Composite Flexible Films for Thermoelectric Generators

Due to the rapid advancement of flexible electronics, flexible thermoelectric materials that capture waste thermal energy have attracted much interest in recent years. In this study, we presented the preparation of a flexible Ag2Te-nylon composite film using the vacuum filtration method, which exhibited a high Seebeck coefficient (−135.5 μV/K) and simultaneous lower thermal conductivity (0.29 W/m K), resulting in an enhanced power factor of about 450 μW/m K2 and a figure of merit (zT) of about 0.48 at 313 K. The developed composite film demonstrates good flexibility in the bending test by retaining about 87% of the electrical conductivity even after 500 times bending. A single strip of the Ag2Te-nylon film can generate a maximum power density (PDmax) of ∼466 μW/cm2 at a ΔT of ∼36.8 K. The obtained thermoelectric performance of the present flexible film is higher in comparison to that of previously reported Ag2Te-based flexible thermoelectric generators. This shows great potential for the current method of fabrication of a flexible thermoelectric film for converting low-grade heat into useful electrical energy.

Ultrafast and Cost-Effective Fabrication of High-Performance Carbon-Based Flexible Thermoelectric Hybrid Films and Their Devices.

Due to their cost-effectiveness and industry-scale feasibility, carbon-based composites have been considered to be promising thermoelectric materials for low-grade power generation. However, current fabrications for carbon-based composites are time-consuming, and their thermoelectric properties are still low. Herein, we develop an ultrafast and cost-effective hot-pressing method to fabricate a novel carbon-based hybrid film, which consists of ionic liquid/phenolic resin/carbon fiber/expanded graphite. This method only costs no more than 15 min. We found that the expanded graphite as the major component enables high flexibility and the introduction of phenolic resin and carbon fiber enhances the shear resistance and toughness of the film, while the ion-induced carrier migration contributes to a high power factor of 38.7 μW m-1 K-2 at 500 K in the carbon-based hybrid film. After the comparison based on the ratios between the power factor with fabrication time and cost among the current conventional carbon-based thermoelectric composites, our hybrid films show the best cost-effective property. Besides, a flexible thermoelectric device, assembled by the as-designed hybrid films, shows a maximum output power density of 79.3 nW cm-2 at a temperature difference of 20 K. This work paves a new way to fabricate cost-effective and high-performance carbon-based thermoelectric hybrids with promising application potential.

Carrier concentration and orientation optimization for high performance (Sb,Bi)2Te3 thermoelectric films via magnetron co-sputtering

High performance flexible thermoelectric thin films are desired for power generation of flexible thermoelectric device. Thermoelectric performance of (Sb,Bi)2Te3 films are determined by the Te content in the matrix as anti-site defect dominates the carrier concentration. By controlling the Te target co-sputtering power, annealing temperature and time, not only the film in-plane orientation is enhanced, the carrier concentration is also effectively controlled in this work. Through a systematically investigation of Te content dependence of the thermoelectric performance, the carrier concentration and orientation is optimized through tuning Te content, and a high power factor of ∼32 μW/cm-K2 for Sb2Te3 film, ∼36 μW/cm-K2 for Bi0.5Sb1.5Te3 film is realized in in-plane orientation. Besides, The thermal conductivity along in-plane direction is determined by photon-electro-thermal (TPET) technique, and the final zT values are ∼0.49 for Sb2Te3, and ∼0.58 for Bi0.5Sb1.5Te3 films at room temperature, respectively.

Positive and Negative Changes in the Electrical Conductance Related to Hybrid Filler Distribution Gradient in Composite Flexible Thermoelectric Films Subjected to Bending

P-type multiwalled carbon nanotubes (MWCNTs), as well as heterostructures fabricated by direct deposition of inorganic thermoelectric materials as antimony and bismuth chalcogenides on MWCNT networks are known as perspective materials for application in flexible thermoelectric polymer-based composites. In this work, the electrical response of three types of Sb2Te3-MWCNT heterostructures-based flexible films-free standing on a flexible substrate, encapsulated in polydimethylsiloxane (PDMS), and mixed in polyvinyl alcohol (PVA) is studied in comparison with the flexible films prepared by the same methods using bare MWCNTs. The electrical conductance of these films when each side of it was subsequently subjected to compressive and tensile stress during the film bending down to a 3 mm radius is investigated in relation to the distribution gradient of Sb2Te3-MWCNT heterostructures or bare MWCNTs within the film. It is found that all investigated Sb2Te3-MWCNT films exhibit a reversible increase in the conductance in response to the compressive stress of the film side with the highest filler concentration and its decrease in response to the tensile stress. In contrast, free-standing and encapsulated bare MWCNT networks with uniform distribution of nanotubes showed a decrease in the conductance irrelevant to the bending direction. In turn, the samples with the gradient distribution of the MWCNTs, prepared by mixing the MWCNTs with PVA, revealed behavior that is similar to the Sb2Te3-MWCNT heterostructures-based films. The analysis of the processes impacting the changes in the conductance of the Sb2Te3-MWCNT heterostructures and bare MWCNTs is performed. The proposed in this work bending method can be applied for the control of the uniformity of distribution of components in heterostructures and fillers in polymer-based composites.

A self-powered flexible sensor based on thermoelectric generation for NO2 gas detection

ABSTRACT Harmful gas leakage often occurs in the engine room of ocean-going ships. Among these harmful gases, NO2 gas accounts for a high proportion. Generally, sensors for detecting NO2 gas in the machinery space have problems such as small detection range, poor sensitivity, and poor stability. Therefore, we present a novel self-powered sensing prototype using electronic printing. This prototype consists of a flexible thermoelectric film and a flexible gas sensor. At 80K temperature difference, the maximum output voltage and power of the prototype reached 102.5 mv and 64.5μw, respectively. The prototype can charge the supercapacitor (5.5 V, 0.47uF) to 5.5 v in 10 minutes. The sensitivity, selectivity and repeatability of gas sensor in different concentration gas environment were studied. The results show that in the range of 20 -100 ppm, the detection current of NO2 concentration curve is approximately linear. The prototype has good stability and repeatability. After 1,000 flexibility tests, the prototype still has high flexibility. After connecting the boost circuit, the prototype can drive the single chip microcomputer to realize the self-power supply and danger. This study provides a new way for the monitoring of harmful gases in the ship engine rooms.

Robust, Flexible Thermoelectric Film for Energy Harvesting by a Simple and Eco-Friendly Method.

As for the self-supporting composite films, it is significant to develop a structural design that allows for excellent flexibility while reducing the negative effect on thermoelectric (TE) properties. Herein, a robust, flexible TE film was fabricated by in situ chemical transformation and vacuum-assisted filtration without any organic solvents involved. The performance of the films was further optimized by adjusting the Ag/Te ratio and post-treatment methods. Owing to the semi-interpenetrating nanonetwork structure formed by AgxTe nanowires and bacterial cellulose, the obtained TE film displayed a high tensile strength of ∼78.4 MPa and a high power factor of 48.9 μW m-1 K-2 at room temperature. A slight electrical conductivity decrement of the TE film in flexible test (∼2% after 1000 bending cycles) indicates an excellent flexibility. Finally, a TE bracelet was assembled to harvest body heat energy, and a steady current of ∼2.7 μA was generated when worn on the wrist indoors. This work provides a reference for the structural design and practical application of flexible TE films.

Highly Electrical Conductive PEDOT:PSS/SWCNT Flexible Thermoelectric Films Fabricated by a High-Velocity Non-solvent Turbulent Secondary Doping Approach.

Materials based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) can be potentially employed as flexible thermoelectric generators (TEGs) to capture waste heat and generate electrical energy. Among various methods, secondary doping is an effective way to modulate its thermoelectric (TE) performance. Different from conventional measures such as dropping, soaking, and steam fumigation, strong shear is integrated with the doping process and termed high-velocity non-solvent turbulent secondary doping (HNTD). We systematically investigate the transformation of PEDOT:PSS during this procedure and the formation mechanism of its highly conductive pathway. It is illustrated that PEDOT:PSS experiences PSS swelling, the phase separation of PEDOT from PSS, the removal of isolated PSS, and the evolution of PEDOT to a linear conformation. These evolutions contribute to the substantial elevation of electrical conductivity (σ). Furthermore, by employing continuous single-walled carbon nanotube (SWCNT) networks as structural units, highly conductive flexible PEDOT:PSS/SWCNT TE thin films could be prepared without sacrificing the Seebeck coefficient (S). Additionally, the effect of HNTD and direct addition method on TE properties of composite films is also compared. Finally, the PEDOT:PSS composite film with 40 wt % SWCNTs by the HNTD method exhibits the maximized power factor (PF) of 501.31 ± 19.23 μW m-1 K-2 with σ of 4717.8 ± 41.51 S cm-1 and S of 32.6 ± 0.13 μV K-1 at room temperature. It is worth mentioning that the σ value 4717.8 ± 41.51 S cm-1 is the highest among the composites based on commercial carbon fillers and organic semiconductors. Finally, a 6-leg TEGs prototype is assembled and illustrates an output power of 4.416 μW under a temperature difference (ΔT) of 58 K. It is thought that such a strategy may provide some guidelines for manufacturing PEDOT:PSS-based functional materials.

Realization of high output power density in solution-processed flexible α-Cu2Se film by compositional off-stoichiometry and optimization of length

The solution-process method can be easily realized without expensive and complicated equipment, which provides the possibility for cost-effective application of flexible thermoelectric films. Nonetheless, the reported output properties of solution-processed Cu2Se based films are not satisfactory due to the absence of effective compositional adjustment and optimal length. In this work, a series of solution-processed nylon-supported flexible Cu2+xSe films have been fabricated. The excess Cu not only fills the vacancies, but also transforms the β-Cu2Se with disordered Cu atoms into long-range ordered lamellar α-Cu2Se, thereby reducing the carrier concentration and improving the carrier mobility of the films. As a result, a high power factor of 856.59 ± 119.92 μW m−1 K−2 has been achieved in the Cu2.20Se film at 303 K. In addition, by numerical simulation, the ideal length of single Cu2.20Se film was calculated to be 2 mm. With an actual temperature difference of 6.6 K, a maximum output power density of 2.918 μW cm−2 K−2, which is superior to those of other p-type flexible thermoelectric films, is realized in the single Cu2.20Se film. This work provides a feasible idea to promote the output performance of solution-processed flexible thermoelectric films.

Pulse Electrochemically Driven Multilayer Assembly of Single‐Walled Carbon Nanotube/Polypyrrole/Tellurium Composite Films for Ultra‐High‐Performance Flexible Thermoelectric Applications

AbstractAlthough several efforts were made to develop high‐performance thermoelectric (TE) composites by a combination of single‐walled carbon nanotubes (SWCNTs) with a high conductivity and tellurium (Te) with a large Seebeck coefficient, only a very limited advance has been achieved because of their intrinsic interfacial incompatibility. In this work, a range of SWCNT/polypyrrole (PPy)/Te flexible composite films are prepared through sequentially pulse electrodepositing PPy and Te over the prefabricated SWCNT membrane electrode, where both the introduction of the PPy sandwich layer and the adoption of two pulse electrodepositions play a vital role in ameliorating the TE performance of the composites via the synergic optimization of an interfacial engineering. Consequently, the best power factor for the optimal SWCNT/PPy/Te composite film reaches up to 1602.4 ± 87.6 µW m−1 K−2 at 300 K, which hits the record for the p‐type PPy‐based TE composites. Moreover, the five‐leg flexible thermoelectric generators assembled with the optimal film harvest an output power of 1512.5 nW at the applied temperature difference of 22.4 K. This work suggests that the multilayer assembly technology driven by pulse electrochemistry is a feasible and effective tactic for architecting high‐performance flexible TE films.

Polyaniline/SWCNT composite films prepared via the solvent-induced strategy for flexible energy harvesting

Flexible thermoelectric nanocomposite films are prepared via a facile solvent-induced strategy, exhibiting high power factor at room temperature. The thermoelectric module prepared from the films exhibits excellent output performance.

Flexible Te/PEDOT:PSS thin films with high thermoelectric power factor and their application as flexible temperature sensors.

Flexible, lightweight, and low-cost thermoelectric thin films are promising for self-powered wearable electronics and sensors. In this work, we report on flexible Te nanostructures/PEDOT:PSS composite thin films with high power factor and their application as flexible temperature sensors. Te nanostructures with high crystallinity and high aspect ratios were synthesized through an environmentally friendly method without using highly toxic chemicals. Individual Te nanostructures achieve a thermoelectric figure of merit (ZT) of 0.13 at 300 K, indicating good potential as inorganic fillers for nanostructures/polymer hybrid materials. Based on the synthesized Te nanostructures, flexible p-type Te/PEDOT:PSS thin films were fabricated through a simple dilution and vacuum filtration method. The power factor of the as-prepared composite thin film outperforms that of either a Te or DMSO-treated PEDOT:PSS thin film, and importantly, it can be further enhanced to 149 μW m-1 K-2 by hot pressing, which is nearly threefold enhancement compared to the values reported for the vacuum-filtered flexible Te/PEDOT:PSS thin films in the literature. The hot-pressed composite thin film shows high flexibility with the electrical conductivity remaining almost unchanged after 1000 bending cycles under a bending radius of 5 mm. Flexible temperature sensors were fabricated based on the hot-pressed Te/PEDOT:PSS thin film, which exhibited high sensitivity in detecting temperature stimuli. The developed temperature sensors were applied onto a two-finger flexible mechanical claw for identifying hot/cold objects in robotic grasping. This work demonstrates an effective approach to enhance the thermoelectric power factor of flexible Te nanostructures/polymer composites and their promising application in flexible thermal sensing.

High-performance, thin-film thermoelectric generator with self-healing ability for body-heat harvesting

Flexible thermoelectric generators (TEGs) are attractive for their ability to power wearable electronics utilizing the temperature difference between the human body and the environment. Here, we present a self-healing flexible TEG assembled with high-performance Ag 2 Se films. A room temperature power factor (PF) as high as 20.8 μW cm −1 K −2 is obtained via isoelectronic copper doping. The relative resistance change of the film is less than 5% of the initial value after 1,000 bending cycles, and the resistance of the Ag 2 Se film recovers to its initial value within a few hours of the bending test. The 6-leg flexible TEG demonstrates a maximum power density of 80 W m −2 at a temperature difference of 50 K. An output voltage of 1.5–2.8 mV can be achieved on the arm in different motion states. These results demonstrate the promising application of Ag 2 Se-based flexible TEGs for wearable electronics. • RT power factor of 20.8 μW cm −1 K −2 is obtained in the Cu-doped Ag 2 Se film • The film exhibits self-healing capability • The 6-leg TEG demonstrates output power density of 80 W m −2 at Δ T of 50 K Hou et al. report a wearable thermoelectric generator (TEG) based on a copper-doped silver selenide flexible thermoelectric film. This TEG demonstrates a high output power density, excellent flexibility, and self-healing ability and is promising for wearable electronic applications.

N-type flexible Bi2Se3 nanosheets/SWCNTs composite films with improved thermoelectric performance for low-grade waste-heat harvesting

Due to the limited thermoelectric performance of polymers and intrinsic rigidness of inorganic materials, it is difficult to obtain n-type thermoelectric materials and devices with low-cost, excellent flexibility, and high performance. In this work, we have successfully synthesized n-type flexible free-standing thermoelectric films by a low-cost solvothermal method, which is composed of Bi2Se3 nanosheets and single-wall carbon nanotubes (SWCNTs). Bi2Se3 nanosheets with excellent crystallinity and rhombohedral morphology were grown on SWCNTs. The optimized Bi2Se3/SWCNTs composite films exhibited a high electrical conductivity of 292.7 S cm−1 and a Seebeck coefficient of − 42.4 μV K−1 at room temperature, eventually achieving an improved power factor of 52.7 μW m−1 K−2. Furthermore, the composite films exhibited excellent flexibility due to the interweaving of Bi2Se3 nanosheets with SWCNTs, where the thermoelectric performance remained almost unchanged after 5000 bending cycles around a 3.5 mm radius rod. A thermoelectric device, composed of the optimized films, was constructed to further show the practicality, which generated a voltage and a power density of 11.5 mV and 86.2 μW cm−2 at a temperature gradient of 58 K, respectively. This work can provide support for the preparation of other n-type free-standing thermoelectric films with both high thermoelectric performance and excellent flexibility.

High Figure-of-Merit Telluride-Based Flexible Thermoelectric Films through Interfacial Modification via Millisecond Photonic-Curing for Fully Printed Thermoelectric Generators.

The thermoelectric generator (TEG)shows great promise for energy harvesting and waste heat recovery applications. Cost barriers for this technology could be overcome by using printing technologies. However, the development of thermoelectric (TE) materials that combine printability, high-efficiency, and mechanical flexibility is a serious challenge. Here, flexible (SbBi)2 (TeSe)3 -based screen-printed TE films exhibiting record-high figure of merits (ZT) and power factors are reported. A high power factor of 24µWcm-1 K-2 (ZTmax ≈1.45) for a p-type film and a power factor of 10.5µWcm-1 K-2 (ZTmax ≈0.75) for an n-type film are achieved. The TE inks, comprised of p-Bi0.5 Sb1.5 Te3 (BST)/n-Bi2 Te2.7 Se0.3 (BT) and a Cu-Se-based inorganic binder (IB), are prepared by a one-pot synthesis process. The TE inks are printed on different substrates and sintered using photonic-curing leading to the formation of a highly conducting β-Cu2- δ Se phase that connects "microsolders," the grains resulting in high-performance. Folded TEGs (f-TEGs) are fabricated using the materials. A half-millimeter thick f-TEG exhibits an open-circuit voltage (VOC ) of 203mV with a maximum power density (pmax ) of 5.1Wm-2 at ∆T=68K. This result signifies that a few millimeters thick f-TEG could power Internet-of-Things (IoTs) devices converting low-grade heat to electricity.

Highly Efficient Flexible n‐Type Thermoelectric Films Formed by Encapsulation of Bi2Se3‐MWCNT Hybrid Networks in Polyvinyl Alcohol

AbstractThe use of organic–inorganic nanocomposites has shown the greatest potential for engineering efficient flexible thermoelectric devices. In this work, a novel approach of encapsulation of as‐grown bismuth selenide‐multiwalled carbon nanotubes (Bi2Se3‐MWCNT) hybrid network in polyvinyl alcohol for fabrication of n‐type flexible thermoelectric films is demonstrated as a successful alternative to the mechanically mixed counterparts. The developed stable flexible n‐type thermoelectric material has a Seebeck coefficient and power factor at room temperature as high as −85 μV K−1 and 0.4 μW m−1 K−2, and figure‐of‐merit, exceeding the value shown by the mixed counterpart by ≈2 orders of magnitude, while requiring 3–4 times less inorganic material in comparison with mixed composites. Charge carrier transport mechanisms and contribution of Bi2Se3 and MWCNT components of not encapsulated and encapsulated hybrid networks to the total Seebeck coefficient, electrical conductance, and power factor are studied. In addition, the fabricated flexible thermoelectric films show good environmental stability at relative humidity levels up to 60%, as well as great mechanical and electrical stability with the increase of resistance within 0.5% and deviations of the Seebeck coefficient within 2% from the initial value during the 100 repetitive bending cycles.

High-sensitivity self-powered temperature/pressure sensor based on flexible Bi-Te thermoelectric film and porous microconed elastomer

• A self-powered Bi-Te and porous microcone-based temperature/pressure sensor is presented. • A flexible TEG could harvest body heat to power pressure sensor and sense temperature. • Bi-Te based TE thin film with heat sink achieves a high-precision temperature sensor. • The porous microconed architectures greatly enhance the sensitivity of pressure sensor. Electronic skins are artificial skin-type multifunctional sensors, which hold great potentials in intelligent robotics, limb prostheses and human health monitoring. However, it is a great challenge to independently and accurately read various physical signals without power supplies. Here, a self-powered flexible temperature-pressure bimodal sensor based on high-performance thermoelectric films and porous microconed conductive elastic materials is presented. Through introducing flexible heat-sink design and harvesting body heat energy, the thin-film thermoelectric device could not only precisely sense temperature signal but also drive the pressure sensor for detecting external tactile stimulus. The integration of Bi-Te based thermoelectric film with high stability in wide temperature range enables the sensor to sense the ambient temperature with high resolution (<0.1 K) as well as excellent sensitivity (3.77 mV K –1 ). Meanwhile, the porous microconed elastomer responds to pressure variation with low-pressure detection (16 Pa) and a high sensitivity of 37 kPa –1 . Furthermore, the bimodal sensor could accurately and simultaneously monitor human wrist pulse and body temperature in real time, which demonstrates promising applications in self-powered electronic skins for human health monitoring systems.

Effect of L-Ascorbic Acid Solution Concentration on the Thermoelectric Properties of Silver Selenide Flexible Films Prepared by Vacuum-Assisted Filtration.

Currently, there are several thermoelectric materials, such as Ag2Te, Bi2Te3, and Sb2Te3, that have been investigated for thermoelectric applications. However, the toxicity and rarity of most of these materials make them unsuitable for practical applications. In contrast, silver selenide (Ag2Se) is an abundant and environment-friendly thermoelectric material. This study provides a facile synthetic approach for preparing high-performance, low-cost, and flexible Ag2Se thermoelectric films. Ag2Se nanomaterials were prepared based on the chemical template method, and the reaction solution concentration was varied to systematically investigate the effects of reaction solution concentration on the characterization and thermoelectric properties of Ag2Se nanomaterials. For convenience of testing, the flexible Ag2Se films were prepared on porous nylon membranes using vacuum-assisted filtration. The prepared thermoelectric films were tested using an X-ray diffractometer, scanning electron microscope, Seebeck coefficient tester, and Hall tester. The film prepared from the solution with the lowest concentration (18.0 mM) demonstrated the best thermoelectric performance, with a maximum power factor of 382.18 μW∙m−1∙K−2 at ~400 K. Additionally, a cold-pressing treatment could effectively enhance the electrical conductivity of the film, without damaging the substrate, as the conductivity of the film remained at 90% of the original value after 1500 bending cycles.

Bi2Te3-based flexible thermoelectric generator for wearable electronics

The rapid development of the Internet of Things increases the demand for wearable devices. Compared with traditional chemical batteries, flexible thermoelectric technology contributes a solution for solving the power supply of wearable electronics. Here, we prepared n-type Bi2Te3 and p-type Bi0.5Sb1.5Te3 flexible thermoelectric films by the magnetron sputtering method, where the thermoelectric performance and their microstructures are systematically studied. The carrier concentration and mobility are optimized by adjusting the deposition temperature, eventually improving the thermoelectric performance and achieving the room-temperature power factors of 3.2 and 6.1 μW cm−1 K−2 for Bi2Te3 and Bi0.5Sb1.5Te3 films, respectively. Furthermore, after being bent 900 times with a radius of 5 mm, the resistance of these films barely increases, demonstrating the great potential for applications in wearable electronics. In order to further evaluate the practicability, these films are used to design a flexible thermoelectric generator, in which output performance improves with the increase in the temperature difference. The power density is up to ∼218.8 μW cm−2 at temperature differences of ∼41 K.

Design, fabrication and performance evaluation of graphene/Bi&lt;sub&gt;0.5&lt;/sub&gt;Sb&lt;sub&gt;1.5&lt;/sub&gt;Te&lt;sub&gt;3&lt;/sub&gt; flexible thermoelectric films and in-plane heat dissipation devices

In-plane heat dissipation technology based on flexible thermoelectric film cooling is expected to provide a solution to efficient in-plane heat dissipation of electronic devices. However, the low electrical transport performance of flexible thermoelectric films and the difficulty in designing the structure of in-plane heat dissipation device seriously restrict the applications of this technology in heat dissipation of electronic devices. In this work, an epoxy/Bi&lt;sub&gt;0.5&lt;/sub&gt;Sb&lt;sub&gt;1.5&lt;/sub&gt;Te&lt;sub&gt;3&lt;/sub&gt; flexible thermoelectric film is incorporated with graphene which can simultaneously regulate the electrical and thermal transport behaviors. It is found that the incorporating of graphene not only contributes to the preferential orientation of Bi&lt;sub&gt;0.5&lt;/sub&gt;Sb&lt;sub&gt;1.5&lt;/sub&gt;Te&lt;sub&gt;3&lt;/sub&gt; grains along (000&lt;i&gt;l&lt;/i&gt;), but also provides a fast carrier transport channel. The carrier concentration and mobility of graphene/Bi&lt;sub&gt;0.5&lt;/sub&gt;Sb&lt;sub&gt;1.5&lt;/sub&gt;Te&lt;sub&gt;3&lt;/sub&gt; flexible thermoelectric film are simultaneously increased. Comparing with the epoxy/Bi&lt;sub&gt;0.5&lt;/sub&gt;Sb&lt;sub&gt;1.5&lt;/sub&gt;Te&lt;sub&gt;3&lt;/sub&gt; flexible thermoelectric film, the highest power factor of the flexible thermoelectric film with 1.0% graphene at room temperature reaches 1.56 mW/(K&lt;sup&gt;2&lt;/sup&gt;·m), increased by 71%, while the cooling temperature difference is doubled. Using this high-performance graphene/Bi&lt;sub&gt;0.5&lt;/sub&gt;Sb&lt;sub&gt;1.5&lt;/sub&gt;Te&lt;sub&gt;3&lt;/sub&gt; flexible thermoelectric film cooling, a cascade structure high-efficiency in-plane heat dissipation device is designed and fabricated. The device can dissipate heat from the heat source area to the heat dissipation area step by step and reduce the temperature of the heat source area by 1.4–1.9 ℃, showing an efficient and stable in-plane heat dissipation capability.

Excellent Thermoelectric Performance from In Situ Reaction between Co Nanoparticles and BiSbTe Flexible Films.

Low-cost flexible thermoelectric (TE) films with excellent cooling performance are critical for the in-plane heat dissipation application based on the TE film refrigeration technology. In this work, a flexible film epoxy/Bi0.5Sb1.5Te3 is developed by the incorporation of ferromagnetic Co nanoparticles to improve the electrical transport and cooling performance. The magnetic properties and microstructures clearly indicate that part of Co nanoparticles in situ reacts with Te from Bi0.5Sb1.5Te3 to form CoTe2, as well as BiTe' antisite defects. The electric conductivity is greatly enhanced because of the increased carrier density, while a large Seebeck coefficient is well maintained because of the extra magnetic scattering. The power factor of the flexible film with 0.2 wt % Co nanoparticles reached 2.28 mW·m-1·K-2 at 300 K, increased by 34% compared to the epoxy/Bi0.5Sb1.5Te3 film. The maximum cooling temperature difference is 1.5 times higher compared with the epoxy/Bi0.5Sb1.5Te3 film. This work provides a general method to improve the electrothermal conversion performance of BiSbTe-based flexible films through in situ reaction.