High-Performance Ag2Se1–xSx Film on Nylon Membrane for Flexible Thermoelectric Generator

Herein, a facile method to fabricate high-performance Ag₂Se_1–xS_x thermoelectric (TE) films on nylon membranes was developed. The Ag₂Se_1–xS_x TE films were fabricated by first wet-chemically synthesizing Ag₂Se_1–xS_x powders beginning from Se/Ag₂S 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/Ag₂S molar ratio is ≤0.7, the films prepared consist of Se-substituted Ag₂S with a monoclinic structure; when it is 0.8, the film obtained is composed of Ag₂S and Ag₂Se in two phases; when it is 0.9, the film prepared consists of S-substituted Ag₂Se with an orthorhombic structure. The S-substituted Ag₂Se 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 Ag₂Se 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.