Researches on flexible thermoelectric materials usually focus on conducting polymers and conducting polymer-based composites; however, it is a great challenge to obtain high thermoelectric properties comparable to inorganic counterparts. Here, we report an n-type Ag2Se film on flexible nylon membrane with an ultrahigh power factor ~987.4 ± 104.1 μWm−1K−2 at 300 K and an excellent flexibility (93% of the original electrical conductivity retention after 1000 bending cycles around a 8-mm diameter rod). The flexibility is attributed to a synergetic effect of the nylon membrane and the Ag2Se film intertwined with numerous high-aspect-ratio Ag2Se grains. A thermoelectric prototype composed of 4-leg of the Ag2Se film generates a voltage and a maximum power of 18 mV and 460 nW, respectively, at a temperature difference of 30 K. This work opens opportunities of searching for high performance thermoelectric film for flexible thermoelectric devices.

A highly flexible Ag2Se based composite film on nylon with a record power factor is prepared for thermoelectric generators.

Due to the limited thermoelectric (TE) performance of conducting polymers and rigidity of inorganic materials, it is still a huge challenge to prepare low-cost, highly flexible, and high-performance TE materials. Herein, we fabricated n-type Ag 2 Se films using a porous nylon membrane as a flexible substrate by vacuum-assisted filtration, followed by hot pressing. A very high power factor of ∼1882 μW m −1 K −2 at room temperature is obtained. The high power factor is mainly the result of the high density of the Ag 2 Se film and the tuned grain orientation, which is realized by the synthesis of multisized Ag 2 Se nanostructures. The film also exhibits excellent flexibility with 90.7% retention of the power factor after bending around a rod of 4 mm radius for 1000 times. A four-leg TE generator is assembled with the Ag 2 Se film, and its maximum output power is up to 3.2 μW at a temperature difference of 30 K, corresponding to the maximum power density of 22.0 W m −2 and a normalized maximum power density of 408 μW m −1 K −2 . This work provides an effective route to achieve high-power-factor, high-flexibility, and low-cost TE films.

Herein, poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) coated Cu x Se y (PC-Cu x Se y ) nanowires are prepared by a wet-chemical method, and PEDOT:PSS/Cu x Se y nanocomposite films on flexible nylon membrane are fabricated by vacuum assisted filtration and then cold-pressing. XRD analysis reveals that the Cu x Se y with different compositions can be obtained by adjusting the nominal Cu/Se molar ratios of their sources. For the composite film starting from a Cu/Se nominal molar ratio of 3, an optimized power factor of ∼270.3 μW/mK2 is obtained at 300 K. Moreover, the film exhibits a superior flexibility with 85% of the original power factor retention after bending for 1000 cycles around a rod with a diameter of 5 mm. TEM and STEM observations of the focused ion beam (FIB) prepared sample reveal that it is mainly attributed to a synergetic effect of the nylon membrane and the composite film with nanoporous structure formed by the intertwined nanowires, besides the intrinsic flexibility of nylon. Finally, a thermoelectric prototype composed of nine legs of the optimized hybrid film generates a voltage and a maximum power of 15 mV and 320 nW, respectively, at a temperature gradient of 30 K. This work offers an effective approach for high TE performance inorganic/polymer composite film for flexible TE devices.

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