Ultrahigh Performance of n-Type Ag₂Se Films for Flexible Thermoelectric Power 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 Ag₂Se 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 Ag₂Se film and the tuned grain orientation, which is realized by the synthesis of multisized Ag₂Se 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 Ag₂Se 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.