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Dual-parameter pressure-temperature sensors are widely employed in personal health monitoring and robots to detect external signals. Herein, we develop a flexible composite dual-parameter pressure-temperature sensor based on three-dimensional (3D) spiral thermoelectric Bi 2 Te 3 films. The film has a (000l) texture and good flexibility, exhibiting a maximum Seebeck coefficient of −181 μV K –1 and piezoresistance gauge factor of approximately −9.2. The device demonstrates a record-high temperature-sensing performance with a high sensing sensitivity (−426.4 μV K −1 ) and rapid response time (~0.95 s), which are better than those observed in most previous studies. In addition, owing to the piezoresistive effect in the Bi 2 Te 3 film, the 3D-spiral deviceexhibits significant pressure-response properties with a pressure-sensing sensitivity of 120 Pa –1 . This innovative approach achieves high-performance dual-parameter sensing using one kind of material with high flexibility, providing insight into the design and fabrication of many applications, such as e-skin. A three-dimensional spiral architecture is used to exploit both thermoelectric and piezoelectric properties of Bi 2 Te 3 films to make a combined temperature and pressure sensor in a single material, with applications such as electronic skin.

Conjugated polymers promise inherently flexible and low-cost thermoelectrics for powering the Internet of Things from waste heat 1 , 2 . Their valuable applications, however, have been hitherto hindered by the low dimensionless figure of merit (ZT) 3 – 6 . Here we report high-ZT thermoelectric plastics, which were achieved by creating a polymeric multi-heterojunction with periodic dual-heterojunction features, where each period is composed of two polymers with a sub-ten-nanometre layered heterojunction structure and an interpenetrating bulk-heterojunction interface. This geometry produces significantly enhanced interfacial phonon-like scattering while maintaining efficient charge transport. We observed a significant suppression of thermal conductivity by over 60 per cent and an enhanced power factor when compared with individual polymers, resulting in a ZT of up to 1.28 at 368 kelvin. This polymeric thermoelectric performance surpasses that of commercial thermoelectric materials and existing flexible thermoelectric candidates. Importantly, we demonstrated the compatibility of the polymeric multi-heterojunction structure with solution coating techniques for satisfying the demand for large-area plastic thermoelectrics, which paves the way for polymeric multi-heterojunctions towards cost-effective wearable thermoelectric technologies. Thermoelectric plastics with a high figure of merit, suppressed thermal conductivity and an enhanced power factor are realized by combining layered and bulk heterojunctions to create a polymeric multi-heterojunction.

We demonstrate that the thermoelectric properties of p-type chalcogenides can be effectively improved by band convergence and hierarchical structure based on a high-entropy-stabilized matrix. The band convergence is due to the decreased light and heavy band energy offsets by alloying Cd for an enhanced Seebeck coefficient and electric transport property. Moreover, the hierarchical structure manipulated by entropy engineering introduces all-scale scattering sources for heat-carrying phonons resulting in a very low lattice thermal conductivity. Consequently, a peak zT of 2.0 at 900 K for p-type chalcogenides and a high experimental conversion efficiency of 12% at Δ T  = 506 K for the fabricated segmented modules are achieved. This work provides an entropy strategy to form all-scale hierarchical structures employing high-entropy-stabilized matrix. This work will promote real applications of low-cost thermoelectric materials. The synergism of entropy engineering and the typical optimization mechanisms in high-entropy-stabilized chalcogenide is unknown. Here, the authors find high-entropy-stabilized composition works as a promising matrix of applying synergistic effect to realize high thermoelectric performance.

Exploring new near-room-temperature thermoelectric materials is significant for replacing current high-cost Bi 2 Te 3 . This study highlights the potential of Ag 2 Se for wearable thermoelectric electronics, addressing the trade-off between performance and flexibility. A record-high ZT of 1.27 at 363 K is achieved in Ag 2 Se-based thin films with 3.2 at.% Te doping on Se sites, realized by a new concept of doping-induced orientation engineering. We reveal that Te-doping enhances film uniformity and (00 l )-orientation and in turn carrier mobility by reducing the (00 l ) formation energy, confirmed by solid computational and experimental evidence. The doping simultaneously widens the bandgap, resulting in improved Seebeck coefficients and high power factors, and introduces Te Se point defects to effectively reduce the lattice thermal conductivity. A protective organic-polymer-based composite layer enhances film flexibility, and a rationally designed flexible thermoelectric device achieves an output power density of 1.5 mW cm −2 for wearable power generation under a 20 K temperature difference. Flexible Ag 2 Se possesses promising near-room-temperature thermoelectric performance, while trade-off in thermoelectric performance and flexibility enhances its practical utility. Here, the authors fabricate polycrystalline Ag 2 Se-based thin film with a high ZT of 1.27 at 363 K by Te doping.

The heating and cooling energy consumption of buildings accounts for about 15% of national total energy consumption in the United States. In response to this challenge, many promising technologies with minimum carbon footprint have been proposed. However, most of the approaches are static and monofunctional, which can only reduce building energy consumption in certain conditions and climate zones. Here, we demonstrate a dual-mode device with electrostatically-controlled thermal contact conductance, which can achieve up to 71.6 W/m 2 of cooling power density and up to 643.4 W/m 2 of heating power density (over 93% of solar energy utilized) because of the suppression of thermal contact resistance and the engineering of surface morphology and optical property. Building energy simulation shows our dual-mode device, if widely deployed in the United States, can save 19.2% heating and cooling energy, which is 1.7 times higher than cooling-only and 2.2 times higher than heating-only approaches. Future zero-energy buildings require smart and dynamic utilization of renewable energy for efficient indoor temperature control. Here the authors show that the dual-mode device enables building envelopes to switch between solar heating and radiative cooling to save HVAC energy for all seasons and all climate zones.

Phase change materials (PCMs) offer great potential for realizing zero-energy thermal management due to superior thermal storage and stable phase-change temperatures. However, liquid leakage and solid rigidity of PCMs are long-standing challenges for PCM-based wearable thermal regulation. Here, we report a facile and cost-effective chemical cross-linking strategy to develop ultraflexible polymer-based phase change composites with a dual 3D crosslinked network of olefin block copolymers (OBC) and styrene-ethylene-butylene-styrene (SEBS) in paraffin wax (PW). The C-C bond-enhanced OBC-SEBS networks synergistically improve the mechanical, thermal, and leakage-proof properties of PW@OBC-SEBS. Notably, the proposed peroxide-initiated chemical cross-linking method overcomes the limitations of conventional physical blending methods and thus can be applicable across diverse polymer matrices. We further demonstrate a portable and flexible PW@OBC-SEBS module that maintains a comfortable temperature range of 39–42 °C for personal thermotherapy. Our work provides a promising route to fabricate scalable polymer-based phase change composite for wearable thermal management. Jing et al. report a cost-effective chemical cross-linking method for synthesizing ultraflexible polymer-based phase change composites with 3D crosslinked networks and further demonstrate portable applications for wearable thermal management.

Room-temperature bismuth telluride (Bi 2 Te 3 ) thermoelectrics are promising candidates for low-grade heat harvesting. However, the brittleness and inflexibility of Bi 2 Te 3 are far reaching and bring about lifelong drawbacks. Here we demonstrate good pliability over 1,000 bending cycles and high power factors of 4.2 (p type) and 4.6 (n type) mW m −1  K −2 in Bi 2 Te 3 -based films that were exfoliated from corresponding single crystals. This unprecedented bendability was ascribed to the in situ observed staggered-layer structure that was spontaneously formed during the fabrication to promote stress propagation whilst maintaining good electrical conductivity. Unexpectedly, the donor-like staggered layer rarely affected the carrier transport of the films, thus maintaining its superior thermoelectric performance. Our flexible generator showed a high normalized power density of 321 W m −2 with a temperature difference of 60 K. These high performances in supple thermoelectric films not only offer useful paradigms for wearable electronics, but also provide key insights into structure–property manipulation in inorganic semiconductors. The development of flexible thermoelectrics is limited by the low power factor and brittleness of materials. Here the authors present strategy to turn Bi 2 Te 3 -based single crystals into flexible films with staggered-layer structure while maintaining superior thermoelectric performance.

Most of the state-of-the-art thermoelectric materials are inorganic semiconductors. Owing to the directional covalent bonding, they usually show limited plasticity at room temperature 1 , 2 , for example, with a tensile strain of less than five per cent. Here we discover that single-crystalline Mg 3 Bi 2 shows a room-temperature tensile strain of up to 100 per cent when the tension is applied along the (0001) plane (that is, the a b plane). Such a value is at least one order of magnitude higher than that of traditional thermoelectric materials and outperforms many metals that crystallize in a similar structure. Experimentally, slip bands and dislocations are identified in the deformed Mg 3 Bi 2 , indicating the gliding of dislocations as the microscopic mechanism of plastic deformation. Analysis of chemical bonding reveals multiple planes with low slipping barrier energy, suggesting the existence of several slip systems in Mg 3 Bi 2 . In addition, continuous dynamic bonding during the slipping process prevents the cleavage of the atomic plane, thus sustaining a large plastic deformation. Importantly, the tellurium-doped single-crystalline Mg 3 Bi 2 shows a power factor of about 55 microwatts per centimetre per kelvin squared and a figure of merit of about 0.65 at room temperature along the a b plane, which outperforms the existing ductile thermoelectric materials 3 , 4 . The thermoelectric material Mg 3 Bi 2 is shown to be ductile in single-crystal form along certain directions, with a room-temperature tensile strain of 100%, which is attributed to the gliding of dislocations.

Thermoelectric technology converts heat into electricity directly and is a promising source of clean electricity. Commercial thermoelectric modules have relied on Bi 2 Te 3 -based compounds because of their unparalleled thermoelectric properties at temperatures associated with low-grade heat (<550 K). However, the scarcity of elemental Te greatly limits the applicability of such modules. Here we report the performance of thermoelectric modules assembled from Bi 2 Te 3 -substitute compounds, including p-type MgAgSb and n-type Mg 3 (Sb,Bi) 2 , by using a simple, versatile, and thus scalable processing routine. For a temperature difference of ~250 K, whereas a single-stage module displayed a conversion efficiency of ~6.5%, a module using segmented n-type legs displayed a record efficiency of ~7.0% that is comparable to the state-of-the-art Bi 2 Te 3 -based thermoelectric modules. Our work demonstrates the feasibility and scalability of high-performance thermoelectric modules based on sustainable elements for recovering low-grade heat. Though earth abundant magnesium-based materials are attractive for thermoelectrics (TEs) due to their device-level performance, realizing efficient modules remains a challenge. Here, the authors report a scalable route to realizing Mg-based compounds for high performance TE modules.

Although the thermoelectric effect was discovered around 200 years ago, the main application in practice is thermoelectric cooling using the traditional Bi 2 Te 3 . The related studies of new and efficient room-temperature thermoelectric materials and modules have, however, not come to fruition yet. In this work, the electronic properties of n-type Mg 3.2 Bi 1.5 Sb 0.5 material are maximized via delicate microstructural design with the aim of eliminating the thermal grain boundary resistance, eventually leading to a high zT above 1 over a broad temperature range from 323 K to 423 K. Importantly, we further demonstrated a great breakthrough in the non-Bi 2 Te 3 thermoelectric module, coupled with the high-performance p-type α-MgAgSb, for room-temperature power generation and thermoelectric cooling. A high conversion efficiency of ~2.8% at the temperature difference of 95 K and a maximum temperature difference of 56.5 K are experimentally achieved. If the interfacial contact resistance is further reduced, our non-Bi 2 Te 3 module may rival the long-standing champion commercial Bi 2 Te 3 system. Overall, this work represents a substantial step towards the real thermoelectric application using non-Bi 2 Te 3 materials and devices. The awaited studies of new and efficient thermoelectric modules have not come to fruition yet. Here, the authors demonstrate a high thermoelectric performance of non-Bi 2 Te 3 module for room-temperature power generation and thermoelectric cooling.