Ultrahigh power factor and flexible silver selenide-based composite film for thermoelectric devices

Herein, an n-type Ag2Se/Ag/CuAgSe thermoelectric (TE) composite film supported by a porous nylon membrane with a record power factor (2231.5 μW m−1 K−2 at 300 K) is obtained via a simple approach. The ultrahigh power factor mainly originates from the optimized carrier transport of the composite material and the interfacial energy filtration effect. HAADF-STEM observations of a focused ion beam (FIB) prepared sample reveal that the Ag and CuAgSe in the composite exist as nanoparticles and most of the Ag nanoparticles and CuAgSe nanoparticles are randomly distributed at the surfaces and grain boundaries of the Ag2Se grains. Bending tests demonstrate superior flexibility of the hybrid film and the power factor decreases by only 10% after bending for 1000 cycles along a rod with a radius of 4 mm. The excellent flexibility is attributed to a synergetic effect of the nanocomposite film with numerous submicron-sized pores and the flexible nylon membrane. A flexible TE module is assembled using the optimum hybrid film, which generates an outstanding power density of 5.42 W m−2 at a temperature difference of 45 K. This work not only demonstrates the tremendous potential of inorganic TE materials for flexible application, but also provides an effective strategy to design high-performance TE composites.