High-Performance Ag₂Se_1–xS_x Film on Nylon Membrane for Flexible Thermoelectric Generator

Herein, a facile method to fabricate high-performance Ag 2 Se 1– x S x thermoelectric (TE) films on nylon membranes was developed. The Ag 2 Se 1– x S x TE films were fabricated by first wet-chemically synthesizing Ag 2 Se 1– x S x powders beginning from Se/Ag 2 S molar ratios of 0.5, 0.6, 0.7, 0.8, and 0.9, followed by vacuum-assisted filtration of the powders on nylon membranes, and finally by hot-pressing. When the Se/Ag 2 S molar ratio is ≤0.7, the films prepared consist of Se-substituted Ag 2 S with a monoclinic structure; when it is 0.8, the film obtained is composed of Ag 2 S and Ag 2 Se in two phases; when it is 0.9, the film prepared consists of S-substituted Ag 2 Se with an orthorhombic structure. The S-substituted Ag 2 Se film exhibits a power factor of ∼1035.4 μW m –1 K –2 at 300 K and excellent flexibility (it retains 94.4% of the pristine electrical conductivity after being bended 1000 times around a rod with a diameter of 8 mm). Furthermore, a flexible TE generator consisting of six legs was assembled with the S-substituted Ag 2 Se film, and it produces a maximum output power of ∼ 5.29 μW (equivalent to a power density of ∼10.5 W m –2 ) under a temperature gradient of 28.6 K. This work provides an avenue to explore high-performance and low-cost flexible TE devices for room temperature use.