Flexible thermoelectric materials and device optimization for wearable energy harvesting

Bahk, Je‐Hyeong; Fang, Hanqing; Yazawa, Kazuaki; Shakouri, Ali

doi:10.1039/c5tc01644d

Cited by 530 publications

(343 citation statements)

References 92 publications

(280 reference statements)

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“…It has been one of the biggest issues inhibiting TEs from a wide usage for energy harvesting. Considering the amount of waste heat and the demand for energy harvesting, we must mass-produce TE modules at reasonable cost [6]. In contrast, flexibility of organic TE modules allows the economic mass-production, for example, using roll-to-roll processes, because the flexible TE modules can adjust their shapes to fit various heat elements even after being mass-produced.…”

Section: Introductionmentioning

confidence: 99%

Organic π-type thermoelectric module supported by photolithographic mold: a working hypothesis of sticky thermoelectric materials

Satoh

Otsuka

Ohki

et al. 2018

Science and Technology of Advanced Materials

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To examine the potential of organic thermoelectrics (TEs) for energy harvesting, we fabricated an organic TE module to achieve 250 mV in the open-circuit voltage which is sufficient to drive a commercially available booster circuit designed for energy harvesting usage. We chose the π-type module structure to maintain the temperature differences in organic TE legs, and then optimized the p- and n-type TE materials’ properties. After injecting the p- and n-type TE materials into photolithographic mold, we eventually achieved 250 mV in the open-circuit voltage by a method to form the upper electrodes. However, we faced a difficulty to reduce the contact resistance in this material system. We conclude that TE materials must be inversely designed from the viewpoints of the expected module structures and mass-production processes, especially for the purpose of energy harvesting.

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Section: Introductionmentioning

confidence: 99%

Organic π-type thermoelectric module supported by photolithographic mold: a working hypothesis of sticky thermoelectric materials

Satoh

Otsuka

Ohki

et al. 2018

Science and Technology of Advanced Materials

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“…Several excellent reviews and reports have already explored the distinct advancements of organic and inorganic materials for flexible TEG applications. [51][52][53][54][55] In fact, research on naturally-flexible, polymerbased materials have been focusing on improving their TE properties, whereas inorganic-based approaches have been relying on wellknown techniques for their implementation, such as molding 56 and lithographic patterning. 57,58 On the other hand, a different approach consist of the beneficial integration and mixing between organics and inorganics to form composite materials with increased functionality and performance; the ideal is to combine the best of each material.…”

Section: Mechanically Adaptable Thermoelectric Generators and Applicamentioning

confidence: 99%

“…64 In term of materials used to form composites, some well-known examples are polyaniline (PANI), polythiophene (PTH) and poly (3, 4-ethylenedioxythiophene):poly (styrenesulfonate) (PE-DOT:PSS) as conductive polymers, and nanostructured Au, Ag, Bi, Te, PbTe, Sb 2 Te 3 , Bi 2 Te 3 and their alloys, as well as carbon nanotubes (CNT), as common inorganic TE materials. 55,59,65 Current research in polymer-based and composite-based TEGs is focusing on finding novel strategies to further enhance their figure of merit (ZT), such including low-dimensional TE materials, as mentioned in the previous section, or including additional treatment for encapsulation in order to mitigate the impact of humidity on the electrical conductivity. 59,66 In the coming subsections we will discuss some of the most practical and novel implementation of mechanically flexible and stretchable TEGs, as well as their challenges and the advantages and applications that these devices could enable.…”

Section: Mechanically Adaptable Thermoelectric Generators and Applicamentioning

confidence: 99%

Review—Micro and Nano-Engineering Enabled New Generation of Thermoelectric Generator Devices and Applications

Rojas

Singh

Inayat³

et al. 2017

ECS J. Solid State Sci. Technol.

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As we are advancing our world to smart living, a critical challenge is increasingly pressing -increased energy demand. While we need mega power supplies for running data centers and other emerging applications, we also need instant small-scale power supply for trillions of electronics that we are using and will use in the age of Internet of Things (IoT) and Internet of Everything (IoE). Such power supplies must meet some parallel demands: sufficient energy supply in reliable, safe and affordable manner. In that regard, thermoelectric generators emerge as important renewable energy source with great potential to take advantage of the widely-abundant and normally-wasted thermal energy. Thanks to the advancements of nano-engineered materials, thermoelectric generators' (TEG) performance and feasibility are gradually improving. However, still innovative engineering solutions are scarce to sufficiently take the TEG performance and functionalities beyond the status-quo. Opportunities exist to integrate them with emerging fields and technologies such as wearable electronics, bio-integrated systems, cybernetics and others. This review will mainly focus on unorthodox but effective engineering solutions to notch up the overall performance of TEGs and broadening their application base. First, nanotechnology's influence in TEGs' development will be introduced, followed by a discussion on how the introduction of mechanically reconfigurable devices can shape up the emerging spectrum of novel TEG technologies. The technology-driven age we are currently in, have brought great advantages to establish a more comfortable and smarter living and it is leading the way for an even faster-growing development in all areas of science and engineering, but at the same time it brings an incredibly fast growing demand for energy. Current and future energy consumption mandate the need for alternative energy sources, with reduced environmental impact. Readily available solar and wind energies have lead the way as alternative energy sources to environmentally challenging fossil fuels.1 Moreover, thanks to more recent developments in thermoelectric (TE) materials and devices, the possibility of making a better use of the widely abundant and normally wasted thermal energy, has becoming a popular and feasible alternative.2 More importantly, thermal waste has become a very important and environmentallyfriendly source of otherwise wasted energy.3,4 There has been already an important set of studies covering the mechanism involved during the conversion from thermal to electric energy. [5][6][7][8] Such studies have been the starting point to develop and optimize novel TE materials with the resourceful aid of uprising nanotechnologies. 9,10 In this review, we will first shortly introduce some important basic concepts and relations about thermoelectrics, as well as some of the current efforts to use nanotechnologies and nano-materials to improve performance and viability. Next, we will focus on identifying innovative devices, novel engineering approach...

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“…[3,4] Examples of such wearable devices are personal textile-based health-monitoring systems, which have resulted in an urgent need for robust and mechanically flexible energy solutions such as body-heat-harvesting thermoelectrics. [5] Another class of devices requiring robust, low-profile, and cheap energy solutions is the ubiquitous low-power sensor and signaling systems, which are powered by energy harvested via thermo-, tribo-, or piezoelectric effect [6][7][8] and possibly stored in a supercapacitor [9] or a Li-ion microbattery. [10,11] In the following sections,…”

Section: Introductionmentioning

confidence: 99%

Flexible Thermoelectric ZnO–Organic Superlattices on Cotton Textile Substrates by ALD/MLD

Karttunen

Sarnes

Townsend

et al. 2017

Adv Elect Materials

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we focus on small-scale energy harvesting based on the thermoelectric effect.Thermoelectric materials can be used to convert waste heat to electric energy via Seebeck effect. They are characterized by a dimensionless figure-of-merit ZT = S 2 σT/(κ e + κ L ), where S is the Seebeck coefficient (thermopower), σ the electrical conductivity, T the temperature, and κ e and κ L the electronic and lattice contributions to the thermal conductivity κ. [12] Figure 1 illustrates the basic principle of a conventional thermoelectric (TE) energy conversion device and the concept of a TE generator device combined with a flexible substrate. Furthermore, Figure 1c shows how the ZT value arises from the abovementioned individual components. Alloys of bismuth telluride (Bi 2 Te 3 ) and antimony telluride (Sb 2 Te 3 ) are by far the most widely used TE materials. They show high ZT values for near-room-temperature applications and have been utilized for decades in solid-state refrigeration applications. A major obstacle for the widespread utilization of Bi-Sb-Te based thermoelectrics is the low abundance of tellurium: it is among the rarest elements in the Earth's crust. Furthermore, current thermoelectric generators based on conventional TE materials such as Bi 2 Te 3 are typically inflexible solid-state devices, which would not be convenient for mobile small-scale applications. [12] Consequently, there is a significant interest in producing flexible and efficient TE generator solutions. In particular, a mechanically flexible TE generator solution integrated with light-weight and comfortable textile substrates could be an enabling platform for body-heat-based energy harvesting.Recently Lee et al. fabricated woven-yarn thermoelectric textiles by coating electrospun polyacrylonitrile nanofiber cores with n-type Bi 2 Te 3 and p-type Sb 2 Te 3 and twisting them into flexible yarns. [13] By weaving the TE-coated yarns into textiles, they were able to obtain an output power of up to 8.56 W m −2 for a temperature difference of 200 K in the textile thickness direction. Another recent study on thermoelectric fabrics utilized a completely different type of material solution, where thermoelectric PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) polymer was used to coat a polyester fabric with a solution-based method. [14] This fabric-TE device was based on p-type PEDOT:PSS only, resulting in a so-called unileg-type device that produced an output power of about 260 µW m −2 for a temperature difference of 75 K.The thermoelectric properties of both pristine ZnO and ZnO-organic superlattice thin films deposited on a cotton textile are investigated. The thin films are fabricated by atomic layer deposition/molecular layer deposition, using hydroquinone as the organic precursor for the superlattices. The resulting thin-film coatings are crystalline, in particular when deposited on a textile substrate with a thin predeposited Al 2 O 3 seed layer. The thermoelectric properties of the ZnO and ZnO-organic superlattice coatings are comp...

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Flexible thermoelectric materials and device optimization for wearable energy harvesting

Cited by 530 publications

References 92 publications

Organic π-type thermoelectric module supported by photolithographic mold: a working hypothesis of sticky thermoelectric materials

Organic π-type thermoelectric module supported by photolithographic mold: a working hypothesis of sticky thermoelectric materials

Review—Micro and Nano-Engineering Enabled New Generation of Thermoelectric Generator Devices and Applications

Flexible Thermoelectric ZnO–Organic Superlattices on Cotton Textile Substrates by ALD/MLD

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