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Highlights: A thermoelectric aerogel of highly elastic, flame-retardant and high-temperature-resistant PEDOT:PSS/SWCNT composite is fabricated. The assembled thermoelectric generator generates a maximum output power of 400 μW at a temperature difference of 300 K. The self-powered wearable sensing glove can achieve wide-range temperature detection, complex hand motion recognition and high-temperature warning. The intelligent fire warning system enables highly sensitive and repeatable monitoring and alarm capabilities for high-temperature fire sources. Despite notable progress in thermoelectric (TE) materials and devices, developing TE aerogels with high-temperature resistance, superior TE performance and excellent elasticity to enable self-powered high-temperature monitoring/warning in industrial and wearable applications remains a great challenge. Herein, a highly elastic, flame-retardant and high-temperature-resistant TE aerogel, made of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/single-walled carbon nanotube (PEDOT:PSS/SWCNT) composites, has been fabricated, displaying attractive compression-induced power factor enhancement. The as-fabricated sensors with the aerogel can achieve accurately pressure stimuli detection and wide temperature range monitoring. Subsequently, a flexible TE generator is assembled, consisting of 25 aerogels connected in series, capable of delivering a maximum output power of 400 μW when subjected to a temperature difference of 300 K. This demonstrates its outstanding high-temperature heat harvesting capability and promising application prospects for real-time temperature monitoring on industrial high-temperature pipelines. Moreover, the designed self-powered wearable sensing glove can realize precise wide-range temperature detection, high-temperature warning and accurate recognition of human hand gestures. The aerogel-based intelligent wearable sensing system developed for firefighters demonstrates the desired self-powered and highly sensitive high-temperature fire warning capability. Benefitting from these desirable properties, the elastic and high-temperature-resistant aerogels present various promising applications including self-powered high-temperature monitoring, industrial overheat warning, waste heat energy recycling and even wearable healthcare. [ABSTRACT FROM AUTHOR]

The emergence of the Internet of Things (IoT) era has necessitated the development of intelligent wearable electronics for fire warning to mitigate fire hazards prior to ignition. Although significant advancements are achieved in thermoelectric materials and devices, the design of a specific thermoelectric wearable device for precision fire warning still remains challenging. In this study, an intelligent sensing system for human IoT fire warning that utilizes a novel light/heat dual‐parameter‐responsive single‐walled carbon nanotube/poly(3‐hexylthiophene‐2,5‐diyl) (SWCNT/P3HT) composite is developed. This system comprises the composite, a circuit microcontroller, and a message transmission system, which together create an intelligent fire source sensing device. The synergistic effect of light and heat is observed to enhance the output voltage and response time under concurrent stimuli, as compared to heating alone. The intelligent sensing system is found to effectively identify and alarm for fire sources, owing to the high thermoelectric and photoelectric performance of the SWCNT/P3HT composite, precise fire recognition, and the ability to adjust the alarming threshold for detecting fire hazards. This study presents a new approach for designing light/heat dual‐parameter‐responsive materials and wearable devices, which hold potential applications in smart home living environments, including child protection against fire hazards. [ABSTRACT FROM AUTHOR]

Smart wearable electronics have attracted increasing attention because of their great prospects in motion monitoring. To date, a specific design of thermoelectric wearable devices aiming at precision monitoring is still challenging, although thermoelectric materials and devices have witnessed significant developments. In this work, intercalated composites of reduced graphene oxide/reduced poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (rGO/rPEDOT:PSS) are reported through the insertion of PEDOT:PSS into 2D graphene oxide layers followed by precise optimization of oxidation‐level of composite, exhibiting an outstanding thermoelectric performance along with excellent thermoelectric stability and mechanical flexibility. Furthermore, a novel‐concept, simple‐structural, self‐powered thermoelectric wearable sensor is demonstrated with rGO/rPEDOT:PSS composite as the active sensing component of the thermoelectric device. Combined with the excellent thermoelectric performance, ingenious device design, and optimized algorithm, the thermoelectric wearable device achieves precision recognition of various hand motions. This study provides a new way to design wearable sensors toward the precision recognition of human motions. [ABSTRACT FROM AUTHOR]

With the rapid development of intelligent devices, flexible robots, medical monitors, and electronic skins, stretchable wireless power supplies are in great demand. Thermoelectric devices have proven to be promising candidates for wearable electronics owing to their significant conversion capability from low‐grade waste heat in the environment to electric energy. Therefore, stretchable thermoelectric generators attract widespread attention and remarkable progress has been made recent years. In this review, various design strategies are comprehensively overviewed from the perspective of material composition design and structure design for enhanced stretchability of thermoelectric materials and devices. Furthermore, the thermoelectric performance and multifunctional applications of stretchable materials and devices are emphasized. Finally, the challenges and prospects in the development and applications of stretchable thermoelectrics are presented. [ABSTRACT FROM AUTHOR]

Solution processability and flexibility still remain major challenges for many thermoelectric (TE) materials, including bismuth telluride (Bi2Te3), a typical and commercially available TE material. Here, we report a new solution‐processed method to prepare a flexible film of a Bi2Te3/single‐walled carbon nanotube (SWCNT) hybrid, where the dissolved Bi2Te3 ion precursors are mixed with dispersed SWCNTs in solution and recrystallized on the SWCNT surfaces to form a "cement–rebar"‐like architecture. The hybrid film shows an n‐type characteristic, with a stable Seebeck coefficient of −100.00 ± 1.69 μV K−1 in air. Furthermore, an extremely low in‐plane thermal conductivity of ∼0.33 W m−1 K−1 is achieved at 300 K, and the figure of merit (ZT) reaches 0.47 ± 0.02. In addition, the TE performance is independent of mechanical bending. The unique "cement–rebar"‐like architecture is believed to be responsible for the excellent TE performances and the high flexibility. The results provide a new avenue for the fabrication of solution‐processable and flexible TE hybrid films and will speed up the applications of flexible electronics and energy conversion. [ABSTRACT FROM AUTHOR]

The urgent need for consistent, reliable, ecofriendly, and stable power sources drives the development of new green energy materials. Thermoelectric (TE) materials receive increasing attention due to their unique capability of realizing the direct energy conversion between heat and electricity, showing diverse applications in harvesting waste heat and low‐grade heat. Carbon materials such as carbon nanotubes (CNTs) and graphene have experienced a rapid development as TE materials because of their intrinsic ultrahigh electrical conductivity and light weight. Besides, polymer‐based carbon composites are particularly fascinating as the combination of the merits of polymers and filler materials leads to high TE performance and superior flexibility. Herein, the recent TE advances are systematically summarized in the studied popularity of carbon materials (ie, CNTs and graphene) and the category of polymers. The conducting polymer‐based carbon materials are particularly highlighted. Finally, the remaining challenges and some tentative suggestions possibly guiding future developments are proposed, which may pave a way for a bright future of carbon and carbon composites in the energy market. [ABSTRACT FROM AUTHOR]

We present an unusual coral-like coating morphology for the poly(3,4-ethylenedioxythiophene)/carbon nanotube (PEDOT/CNT) composites with dramatically improved thermoelectric performance. First, the PEDOT/CNT composites are prepared via chemical oxidation polymerization procedure in reverse microemulsions, using hexane or xylene as the reaction medium. The composite films exhibit excellent mechanical flexibility against bending and twisting. Then, the cable-like (in hexane) or coral-like (in xylene) morphology for the thick and uniform coating layer is directly proved by field-emission scanning electron microscopic images. Subsequently, their thermoelectric performances are quantitatively measured at room temperature. After that, the ordered arrangement structures of PEDOT macromolecules, the level of doping and the level of oxidation are investigated by X-ray diffraction technique and X-ray photoelectron spectra, respectively. Finally, the molecular mechanism for the enhanced thermoelectric performance is discussed. [ABSTRACT FROM AUTHOR]

Molecular doping is vital to control the charge transport in organic/inorganic semiconductors, which provides an important technique to optimize the thermoelectric (TE) performance. Here, two organic borates with designed molecular structures, Ph 3 C+[B(C 6 F 5) 4 ]- and Ph 2 I+[B(C 6 F 5) 4 ]-, were employed as p-type dopants to enhance the TE performance of single-walled carbon nanotubes (SWCNTs). The electrons are transferred from SWCNTs to the electron-deficient cations of the borates, resulting in charge-transfer complexes stabilized by [B(C 6 F 5) 4 ]-. Specifically, compared to the pristine SWCNTs, the borate-doped SWCNT films reveal enhanced power factors of 135.5 ± 8.4 μW m−1 K−2 for SWCNT/Ph 3 C+[B(C 6 F 5) 4 ]-, and 156.6 ± 7.2 μW m−1 K−2 for SWCNT/Ph 2 I+[B(C 6 F 5) 4 ]-. Moreover, the p-doped SWCNTs display good air and thermal stabilities due to the chemical inertness and thermal stability of the organic [B(C 6 F 5) 4 ]- anions. In addition, by immersion in organic solvent, the TE performance can be further increased. This work provides a novel strategy to achieve stable p-doped SWCNT films with excellent TE performance via rational molecular design of organic borate dopants. Novel organic p-type borate dopants were designed to achieve single-walled carbon nanotube hybrids with enhanced thermoelectric performance by effective electron transfer mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

Organic and hybrid thermoelectric (OHT) materials have attracted increasing research interest over the past decade. Thermal conductivity measurement plays a critical role in evaluating and improving the thermoelectric performance of various types of these novel materials, ranging from bulks to low‐dimensional structures. Commonly used and newly developed techniques for thermal conductivity measurement, most of which have been applied to OHT materials in recent years, are reviewed. They are categorized as steady‐state methods, time‐domain methods, or frequency‐domain methods. The operating principles, merits and limitations, technical issues, and application examples for each technique are also discussed. [ABSTRACT FROM AUTHOR]

Although organic and composite thermoelectric (TE) materials have witnessed explosive developments in the past five years, the research of flexible TE devices is rather limited. In particular, their assembly strategies and device performance reported in the literature cannot be directly compared, due to a variety of deviances including p‐ and n‐type component materials, shape and dimensions of p‐n flexible films, and applied temperature gradient (ΔT). Here, three types of assembly strategies for flexible TE devices, that is, serial, folding, and stacking, are compared by fixing the corresponding experimental parameters. Furthermore, a convenient and general method to evaluate the flexible device performance (FDP) is put forward, that is, FDP  =  PmaxmΔTN, where the maximum output power (Pmax) is divided by product mass (m), ΔT, and pair number of p‐n couples (N). The FDPs for the present serial, folding, and stacking devices are 11.13, 8.87, and 0.05 nW g−1 K−1, respectively, confirming that the serial configuration is the best among the three strategies for flexible device fabrication. The preliminary evaluation method proposed herein will pave the way for a design strategy of flexible TE devices and speed up their applications in waste‐heat harvesting, e‐skin, wearable electronics, etc. [ABSTRACT FROM AUTHOR]

Despite the significant progress in thermoelectric composites in the last five years, examining the existing main body of publications shows the scarcity of composite systems and limited preparation strategies. Metal-organic frameworks (MOFs) have been extensively studied and have wide applications, however, MOF-related thermoelectric composites have been seldom reported mainly due to their poor electrical conductivity. In this work, we propose a conceptual strategy, in situ growing reaction and subsequent annealing, to achieve zeolitic imidazolate framework 67/carbon nanotube (ZIF-67@CNT) composites with a unique microstructure of MOFs growing on CNT surfaces. The ZIF-67@CNT composites display outstanding and tunable thermoelectric properties. Annealing plays an important role in the composite morphology, structure and thermoelectric performance. Both the electrical conductivity (825.7 ± 12.0 S cm−1) and the figure of merit (ZT = ∼0.02) at room temperature are the highest in the experimental data reported so far for MOF-related materials, and even comparable to the corresponding theoretical values. The results inspire a new insight into MOF-related thermoelectric composites, which should be considered for future design strategies for novel high-performance thermoelectric composites. Image 1 [ABSTRACT FROM AUTHOR]

Organic polymer/inorganic thermoelectric (TE) composites are emerging green energy materials for diverse applications including harvesting waste or low-quality heat, local cooling, sensing and wearable electronics. Here, we report flexible films of new TE composites by employment of SnS nanobelt into polymer matrix. First, the SnS nanobelts with high purity were prepared by a convenient hydrothermal process. Then, the poly (3,4-ethylenediox-ythiophene): poly (styrenesulfonate) (PEDOT:PSS)/SnS nanobelt composites were obtained by a solution mixing procedure aided by ultrasonication. The structure and morphology of the SnS nanobelts as well as the PEDOT:PSS/SnS composites were characterized by X-ray diffraction (XRD) and field-emission scanning electroscopic (FESEM) techniques. The effects of the SnS content and the dispersing agent (organic solvent) on the dispersion state and the TE performance for the composites were investigated. The highest power factor at room temperature reached 27.8 ± 0.5 μW m −1  K −2 for the PEDOT:PSS/SnS nanobelt composite prepared in N , N -Dimethylformamide. The present study opens a novel avenue to exploit of excellent polymer TE composites by introduction of inorganic nanoparticles with large Seebeck coefficients. [ABSTRACT FROM AUTHOR]

Polymer based ternary thermoelectric composites have been studied. Here, poly(3,4-ethylenedioxythiophene)/graphene/carbon nanotube (PEDOT/graphene/CNT) ternary composites are prepared by in situ polymerization and subsequent physical mixing. Then, the morphology is directly observed by scanning electron microscopy. Finally, the thermoelectric performances are measured and discussed, where the effect of acid-treatment is investigated and comparison with those of the neat PEDOT and the binary PEDOT/graphene composite is conducted. [ABSTRACT FROM AUTHOR]

Despite the explosive achievements in thermoelectric (TE) composites, their mechanical (ME) performance has received little attention relative to the significant enhancement of the TE performances. Furthermore, there always exists a trade-off between TE and ME performances, i.e. , both are difficult to be improved simultaneously. Herein, we realize the decoupling of the trade-off between TE and ME performances for flexible polycarbonate (PC)/single-walled carbon nanotube (SWCNT) composites via interfacial adjustment. The barrel-shaped droplet-like PC granules are observed on the surfaces of the acid-treated SWCNTs (a-SWCNTs), indicating high wettability and interfacial affinity. The obtained PC/a-SWCNT composite displays a maximum power factor (PF) value of 6.2 μW m−1 K−2, which distinctly overmatches the PC/pristine SWCNT (p -SWCNT) with a PF value of 4.8 μW m−1 K−2. In addition, the composites reveal the increments of 22% and 16% in the fracture strength and tensile modulus over the PC/p-SWCNT composite, respectively. This decoupling of the trade-off is ascribed to the high electrical conductivity of a-SWCNTs and the strong interfacial interaction between PC and a-SWCNTs. The present work provides an easy and promising methodology to decouple the intractable trade-off issue of TE and ME performances and benefits their practical TE applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of aggregation structure evolution on thermoelectric performance is studied. • Thermal annealing induces notably increased PEDOT crystallinity. • Solvent treatment affects nanofibril formation, edge-on stacking, phase separation. • Power factor of the treated film is 216 times of that of the pristine. Organic polymer thermoelectric (TE) materials have developed rapidly in recent years in terms of strategies to improve their TE performance. However, the effect of molecular mechanisms on their TE performance remains yet to be unveiled. Insights into the evolution of crystalline microstructures of conjugated polymers are critical in determining their aggregate structure and hence their TE performance. Herein, an effective approach has been developed to modify the aggregate structures of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). During annealing and subsequent solvent post-treatment, phase separation between the conductive PEDOT and the insulating PSS occurs and the excess PSS in the skin layer is effectively removed. As a result, carrier mobility and carrier concentration are synergistically boosted via the formation of well-crystallized molecular morphology and the increase of PEDOT doping level, leading to significantly enhanced TE performance with an unprecedented power factor that is 216 times of that of the pristine samples. The corresponding molecular mechanisms are discussed in detail and the aggregate structure evolution route is thoroughly proposed. It is believed that the aggregate structure evolution proposed in this work and its influential mechanisms on TE performance can be extended to other polymers and potentially direct the future design of high-performance polymer-based TE materials. [ABSTRACT FROM AUTHOR]