Herein, a flexible Ag2Se/Se composite film with a high power factor has been fabricated on a nylon membrane. The film has a high density and contains well-crystallized Ag2Se grains and embedded Se nanoinclusions, which exhibits not only excellent flexibility but also a comparably large room-temperature power factor and Seebeck coefficient of up to 2023 μW m-1 K-2 and -155 μV K-1, respectively. The high Seebeck coefficient is ascribed to the energy-filtering effect as caused by the Se/Ag2Se heterointerface. The assembled flexible thermoelectric generator (4-leg) exhibits a maximum output power of 1135 nW and a power density of up to 16.4 W m-2 when the applied temperature difference is 30 K. This work offers a feasible method to design high-performance and low-cost flexible thermoelectric generators used for wearable electronics.

In this work, we developed a facile method to fabricate low-cost, flexible, and high-thermoelectric-performance n-type Ag2Se1-xSx@(Ag2S1-ySey/S) composite film on a nylon membrane. The composite film was prepared by first performing wet-chemical synthesis of the S-doped Ag2Se powder, then vacuum-assisted filtration of the powder on a nylon membrane, and finally hot-pressing. Transmission electron microscopy (TEM) observation and energy-dispersive system (EDS) analysis of the film revealed that the film had a porous network-like microstructure, in which Ag2Se1-xSx sub-micron grains formed the skeleton and are coated by a ∼15 nm thick layer of S-rich Ag2S1-ySey nanograins mixed with an S amorphous phase. The film showed a power factor of ∼954.7 μW·m-1·K-2 at 300 K and superior flexibility (94.4% of the original electrical conductivity was preserved after bending 2000 times around a rod with a radius of 4 mm). Moreover, a six-leg flexible thermoelectric generator was assembled with the film and produced a maximum power of 6.67 μW (corresponding power density ∼14.8 W/m2) at a temperature difference of 38.7 K. This work reveals a novel approach to explore high-performance and low-cost flexible thermoelectric devices suitable for room-temperature applications.

Herein, we fabricate a high-performance Ag/Ag2Se thermoelectric (TE) film by a novel method. Firstly, Ag/Ag2Se nano-dendritic composite powders were synthesized by a microwave-assisted synthesis method, then the powders were vacuum filtrated on nylon filter membrane followed by hot-pressing. Through optimization of Ag: Se ratios, a maximum power factor of 2436 & PLUSMN; 240 mu W m(-1) K-2 at room temperature has been acquired. It is one of the best values reported for n-type flexible TE films to date. The high TE performance can be ascribed to the synergy effect between Ag and Ag2Se. Besides, the composite film also shows good flexibility: 94% and 87% of the electrical conductivity are maintained, respectively, when it is subjected to a compressive force and a tensile force after 1000 bending cycles along an 8-mm diameter rod. Meanwhile, the film also shows good stability in air and good moisture resistance. A 6-leg flexible TE generator assembled with the optimized film shows a low internal resistance of -5 & UOmega;, mainly owing to high electrical conductivity of -3030 & PLUSMN; 132 S cm(-1) of the film. It outputs a voltage and a maximum power of 16.1 mV and 6.08 mu W (corresponding power density of -13.56 W m(-2)), respectively, at a temperature gradient of 29.6 K. This work provides a great path for the fabrication of exceptional high-performance n-type flexible TE films, which will certainly promote the practical applications of TE films.

Transition metal hydroxides have shown high capacity performances when at a small mass loading of active material, while it is still a great challenge to obtain a high capacity performance when the mass loading is high. To maximize the capacity at high mass loading, the microstructure of the electrode should be rationally designed. Herein, we report a nickel-cobalt (oxy)hydroxide composite with three-dimensional hierarchical porous architecture realized by an in-situ electrochemical activation method to trigger the active sites and structural rearrangement. By systematically tuning the pore sizes in the hierarchical structure, an optimal composite delivers a record high areal capacity (34.8 mAh cm-2) and energy density (19.1 mWh cm-2) at the mass loading up to 230 mg cm-2. It gives new insights for preparing high performance electrode materials by a facile method and provides a blueprint for the design of high mass-loading supercapacitors.

A facile method to prepare flexible n-type Ag 2 Se/Se/polypyrrole (PPy) composite films is developed. First, Ag 2 Se nanostructures (NSs) are wet chemically synthesized; PPy is then in situ polymerized at the surface of the Ag 2 Se NSs; and finally, the Ag 2 Se/Se/PPy composite film on a porous nylon membrane is fabricated by a vacuum-assisted filtration process followed by hot pressing. An optimal composite film shows an exceptionally high power factor of ≈2240 µW m −1 K −2 at 300 K, mainly because of the synergistic effect between well-developed crystalline Ag 2 Se grains and a small amount of Se and PPy. The film also possesses outstanding flexibility (only about 6.5% decrease in electrical conductivity after 1000 times bending along a rod with a radius of 4 mm). Moreover, a flexible thermoelectric generator composed of six legs of the film outputs a voltage of 21.2 mV and a maximum power of 4.04 µW (corresponding power density of 37.6 W m −2 ) at a temperature difference of 34.1 K, verifying exceptionally high thermoelectric properties. This work shows the promise of the as-prepared composite film for practical applications in wearable devices and will surely promote the research and development of flexible TE generators.

Room-temperature thermoelectric materials are important for converting heat into electrical energy. As a wide-bandgap semiconductor material, CuI has the characteristics of non-toxicity, low cost, and environmental friendliness. In this work, CuI powder was synthesized by a wet chemical method, then CuI film was formed by vacuum assisted filtration of the CuI powder on a porous nylon membrane, followed by hot pressing. The film exhibits a large Seebeck coefficient of 600 μV · K −1 at room temperature. In addition, the film also shows good flexibility (∼95% retention of the electrical conductivity after being bent along a rod with a radius of 4 mm for 1000 times). A finger touch test on a single-leg TE module indicates that a voltage of 0.9 mV was immediately generated within 0.5 s from a temperature difference of 4 K between a finger and the environment, suggesting the potential application in wearable thermal sensors.

Herein, we report a Ag2Se/Ag/PEDOT (poly (3,4-ethylenedioxythiophene) composite film with a high thermoelectric performance and superior flexibility. First, we used PEDOT: poly (styrenesulfonate) (PSS) coated Se nanowires (NWs) as templates to prepare PEDOT:PSS coated Ag2Se/Ag composite powders, then Ag2Se/Ag/PEDOT composite films supported on porous nylon membrane were fabricated by vacuum assisted filtration and then hot pressing. An optimum composite film exhibits a high power factor of -1442.5 mu W m(-1) K-2, ultrahigh electrical conductivity (sigma) of -5957.3 S cm(-1) and superior flexibility (only 5.5% decrease in sigma after 1000 times bending around a 4 mm radius rod) at RT. A certain amount of Ag phase in the composite film leads to an ultrahigh sigma, while the PEDOT located at the interface between Ag and Ag2Se grains and at the surface of the Ag2Se grains causes the composite film with a low thermal conductivity. The excellent flexibility is due to the synergistic effect of the nylon membrane and PEDOT. Moreover, a 4-leg flexible thermoelectric power generator (f-TEG) assembled with the composite film shows a low internal resistance of -8 Omega, which makes it very possible to be integrated with a DC/DC converter for continually outputting power. The f-TEG produces a voltage of 5.6 mV and a maximum power of 1.8 mu W (power density of 7.47 W m(-2)) at a temperature gradient of 27 K. This work provides an effective avenue for preparing high-performance flexible thermoelectric film with ultrahigh electrical conductivity. (C) 2021 Elsevier Ltd. All rights reserved.

Herein, we prepared Ga doped Ag2Se flexible films on porous nylon membrane. First, Se nanowires (NWs) were wet chemically synthesized, then different amounts of Ga doped Ag2Se (Ag2-xGaxSe, x = 0.01, 0.02, 0.04) NWs were prepared using the Se NWs as templates in solution at 80 degrees C, and finally the Ga doped Ag2Se films on porous nylon membrane were fabricated by vacuum assisted filtration and then hot pressing at 230 degrees C and 1 MPa for 30 min. The Ag1.98Ga0.02Se film exhibits a higher power factor of similar to 1162 mu W m(-1) K-2 at 300 K and a superior flexibility: after bending for 1000 cycles around a 4-mm-radius rod, about 97% of the initial electrical con-ductivity is maintained.