Exceptionally High Power Factor Ag2Se/Se/Polypyrrole Composite Films for Flexible Thermoelectric Generators

Abstract 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.