Flexible thermoelectrics provide a different solution for developing portable and sustainable flexible power supplies. The discovery of silver sulfide–based ductile semiconductors has driven a shift ...in the potential for flexible thermoelectrics, but the lack of good p-type ductile thermoelectric materials has restricted the reality of fabricating conventional cross-plane π-shaped flexible devices. We report a series of high-performance p-type ductile thermoelectric materials based on the composition-performance phase diagram in AgCu(Se,S,Te) pseudoternary solid solutions, with high figure-of-merit values (0.45 at 300 kelvin and 0.68 at 340 kelvin) compared with other flexible thermoelectric materials. We further demonstrate thin and flexible π-shaped devices with a maximum normalized power density that reaches 30 μW cm
−2
K
−2
. This output is promising for the use of flexible thermoelectrics in wearable electronics.
A flexible power source
Thermoelectric materials can harvest heat and turn it into power. Heat sources potentially include the heat generated by humans through wearable devices and might enable self-powering systems, but the lack of ductility for most thermoelectrics poses a major problem. Yang
et al
. found a thermoelectric silver/copper–based semiconductor that also is ductile (see the Perspective by Hou and Zhu). This material allows for a thin, flexible device capable of producing power, even when adhered to a wrist. —BG
A flexible thermoelectric was developed from a silver/copper–based semiconductor that can be fashioned into a thin device.
Hetero‐shaped thermoelectric (TE) generators (TEGs) can power the sensors used in safety monitoring systems of undersea oil pipelines, but their development is greatly limited by the lack of ...materials with both good shape‐conformable ability and high TE performance. In this work, a new ductile inorganic TE material, Ag20S7Te3, with high TE performance is reported. At 300–600 K, Ag20S7Te3 crystallizes in a body‐centered cubic structure, in which S and Te atoms randomly occupy the (0, 0, 1) site. Due to the smaller generalized stacking fault energy in the (101¯)010 slip system, Ag20S7Te3 shows better ductility than Ag2S, yielding excellent shape‐conformability. The high carrier mobility and low lattice thermal conductivity observed in Ag20S7Te3 result in a maximum dimensionless figure of merit (zT) of 0.80 at 600 K, which is comparable with the best commercial Bi2Te3‐based alloys. The prototype TEG consisting of 10 Ag20S7Te3 strips displays an open‐circuit voltage of 69.2 mV and a maximum power output of 17.1 µW under the temperature difference of 70 K. This study creates a new route toward hetero‐shaped TEG.
A new ductile inorganic thermoelectric (TE) material, Ag20S7Te3, with high carrier mobility, low lattice thermal conductivity, and a maximum zT of 0.80 at 600 K is reported. The prototype hetero‐shaped TE generator consisting of 10 Ag20S7Te3 strips displays an open‐circuit voltage of 69.2 mV and a maximum power output of 17.1 μW under a temperature difference of 70 K.
High-performance liquid-like thermoelectrics have attracted global renewed attention since the paradigm of ‘phonon-liquid electron-crystal’ was proposed in 2012. As one of the most typical ...liquid-like thermoelectric materials, Cu2Se-based compounds have been widely studied and their thermoelectric figure of merits have continuously increased up to >2.0. Herein, a comprehensive overview is presented on the recent progress and future challenges for Cu2Se-based thermoelectric materials. First, the basic properties of Cu2Se, such as the complex crystal structures, unique liquid-like behavior, and anomalous critical phenomenon during phase transition are presented. Next, some common synthesis recipes are concisely outlined and the impact on the thermoelectric properties is intercompared. The effective strategies for improving the thermoelectric performance are then summarized, with some typical studies highlighted. Furthermore, the utmost concerned stability issues, in particular Cu ion migration, are discussed followed by the latest progress on Cu2Se-based thermoelectric devices. Finally, the challenges and outlook toward further development of Cu2Se-based materials, devices, and applications are provided.
Non-classical actions of vitamin D were first suggested over 30 years ago when receptors for the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), were detected in various tissues and ...cells that are not associated with the regulation of calcium homeostasis, including activated human inflammatory cells. The question that remained was the biological significance of the presence of vitamin D receptors in the different tissues and cells and, with regard to the immune system, whether or not vitamin D plays a role in the normal immune response and in modifying immune mediated diseases. In this article findings indicating that vitamin D is a key factor regulating both innate and adaptive immunity are reviewed with a focus on the molecular mechanisms involved. In addition, the physiological significance of vitamin D action, as suggested by in vivo studies in mouse models is discussed. Together, the findings indicate the importance of 1,25(OH)2D3 as a regulator of key components of the immune system. An understanding of the mechanisms involved will lead to potential therapeutic applications for the treatment of immune mediated diseases.
Flexible thermoelectrics is a synergy of flexible electronics and thermoelectric energy conversion. To date, state-of-the-art thermoelectrics is based on inorganic semiconductors that afford high ...electron mobility but lack in mechanical flexibility. By contrast, organic materials are amply flexible but low in electrical mobility and power output; the inorganic-organic hybrid design is a viable material-level option but has critical device-level issues for practical application. Here, we reported high intrinsic flexibility and state-of-the-art figures of merit (up to 0.44 at 300 K and 0.63 at 450 K) in Ag
2
S-based inorganic materials, opening a new avenue of flexible thermoelectrics. In the flexible full-inorganic devices made of such Ag
2
S-based materials, high electrical mobility yielded a normalized maximum power density up to 0.08 W m
−1
under a temperature difference of 20 K near room temperature, orders of magnitude higher than organic devices and organic-inorganic hybrid devices. These results promised an emerging paradigm and market of wearable thermoelectrics.
Flexible thermoelectrics is a synergy of flexible electronics and thermoelectric energy conversion. In this work, we fabricated flexible full-inorganic thermoelectric power generation modules based on doped silver chalcogenides.
Manipulating nanowire assembly could help the design of hierarchical structures with unique functionalities. Herein, we first report a facile solution‐based process under ambient conditions for ...co‐assembling two kinds of nanowires which have suitable composition and functionalities, such as Ag and Te nanowires, for the fabrication of flexible transparent electrodes. Then Te nanowires can be etched away easily, leaving Ag nanowire networks with controllable pitch. By manipulating the assembly of Ag and Te nanowires, we can precisely tailor and balance the optical transmittance and the conductivity of the resulting flexible transparent electrodes. The network of Ag nanowires which have tunable pitch forms a flexible transparent conducting electrode with an averaged transmission of up to 97.3 % and sheet resistances as low as 2.7 Ω/sq under optimized conditions. The work provides a new way for tailoring the properties of nanowire‐based devices.
Nano networking: Silver nanowires and Te nanowires are co‐assembled by the Langmuir–Blodgett technique. Etching away the Te nanowires leaves Ag nanowire networks in which the spacing between the Ag wires is controlled by the Te nanowires. By manipulating the spacing between nanowires the optical transparency and electrical conductivity of flexible Ag nanowire electrodes can be precisely tailored.
Wearable touch panels, a typical flexible electronic device, can recognize and feed back the information of finger touch and movement. Excellent wearable touch panels are required to accurately and ...quickly monitor the signals of finger movement as well as the capacity of bearing various types of deformation. High‐performance thermistor materials are one of the key functional components, but to date, a long‐standing bottleneck is that inorganic semiconductors are typically brittle while the electrical properties of organic semiconductors are quite low. Herein, a high‐performance flexible temperature sensor is reported by using plastic Ag2S with ultrahigh temperature coefficient of resistance of −4.7% K−1 and resolution of 0.05 K, and rapid response/recovery time of 0.11/0.11 s. Moreover, the temperature sensor shows excellent durability without performance damage or loss during force stimuli tests. In addition, a fully flexible intelligent touch panel composed of a 16 × 10 Ag2S‐film‐based temperature sensor array, as well as a flexible printed circuit board and a deep‐learning algorithm is designed for perceiving finger touch signals in real‐time, and intelligent feedback of Chinese characters and letters on an app. These results strongly show that high‐performance flexible inorganic semiconductors can be widely used in flexible electronics.
A fully flexible intelligent thermal touch panel based on the intrinsically plastic Ag2S semiconductor can well perceive finger touch signals in real‐time and displays intelligent feed back of Chinese characters and letters on an app.
The development of flexible organic-inorganic thermoelectric composites constitutes a promising material approach toward harvesting heat from the human body or environment to power wearable ...electronics. To this end, compositing one-dimensional inorganic materials, such as carbon nanotubes or metal nanowires, with organic polymers has demonstrated efficacy but also drawbacks:
e.g.
, the Seebeck coefficient of an inorganic constituent is too low to meet the onset voltage requirement of electronics, and it is hard to attain coherent interfaces between the inorganic and organic constituents. Here, we proposed a dimensionality/morphology matching strategy and conducted a proof-of-principle study on (PVDF)/Ta
4
SiTe
4
organic-inorganic composites. A record high normalized maximum power density of 0.13 W m
−1
at a temperature difference of 35.5 K was obtained in prototype flexible thermoelectric modules made of (PVDF)/Ta
4
SiTe
4
composites. This study attests to the efficacy of the dimensionality/morphology matching strategy and the potential of using such conformal semiconducting organic-inorganic composites in wearable electronics.
The development of flexible organic-inorganic thermoelectric composites constitutes a promising material approach toward harvesting heat from the human body or environment to power wearable electronics.
Deformable thermoelectrics have great potential in self‐powered flexible or hetero‐shaped electronics. The exceptional room‐temperature plasticity recently discovered in several inorganic ...semiconductors makes it possible to develop new thermoelectric (TE) materials with both high performance and intrinsic deformability. Nonetheless, all the known plastic or ductile TE materials are n‐type semiconductors. It is urgent to explore p‐type counterparts for device design and fabrication. In this study, the first p‐type plastic inorganic TE material is reported. Via alloying Cu in n‐type plastic Ag2S0.7Se0.3 to modulate the charged crystal defects, (Ag1−xCux)2S0.7Se0.3 (x = 0.7–0.8) can simultaneously realize good plasticity and p‐type conduction. Particularly, (Ag0.2Cu0.8)2S0.7Se0.3 with a hexagonal structure shows a maximum zT of 0.42 at 800 K. Via the introduction of Cu deficiencies, the good plasticity is well maintained while the maximum zT is greatly enhanced to 0.95 at 800 K, a record‐high value for plastic TE materials. This study is expected to accelerate the development of plastic TE semiconductors and full‐inorganic deformable TE devices for the application in hetero‐shaped power generators.
The first p‐type plastic inorganic thermoelectric (TE) material is reported. (Ag0.2Cu0.8)2S0.7Se0.3 at room temperature shows a p‐type conduction behavior and large plastic deformability, that is, an ultimate bending strain of 10% and a compressive strain of 30%. The maximum zT reaches 0.95 at 800 K after compositional optimization, which represents the highest value for plastic TE materials.