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.