Ultraflexible and High-Thermoelectric-Performance Sulfur-Doped Ag₂Se Film on Nylon for Power Generators

In this work, we developed a facile method to fabricate low-cost, flexible, and high-thermoelectric-performance n-type Ag2Se1–xSx@(Ag2S1–ySey/S) composite film on a nylon membrane. The composite film was prepared by first performing wet-chemical synthesis of the S-doped Ag2Se powder, then vacuum-assisted filtration of the powder on a nylon membrane, and finally hot-pressing. Transmission electron microscopy (TEM) observation and energy-dispersive system (EDS) analysis of the film revealed that the film had a porous network-like microstructure, in which Ag2Se1–xSx sub-micron grains formed the skeleton and are coated by a ∼15 nm thick layer of S-rich Ag2S1–ySey nanograins mixed with an S amorphous phase. The film showed a power factor of ∼954.7 μW·m–1·K–2 at 300 K and superior flexibility (94.4% of the original electrical conductivity was preserved after bending 2000 times around a rod with a radius of 4 mm). Moreover, a six-leg flexible thermoelectric generator was assembled with the film and produced a maximum power of 6.67 μW (corresponding power density ∼14.8 W/m2) at a temperature difference of 38.7 K. This work reveals a novel approach to explore high-performance and low-cost flexible thermoelectric devices suitable for room-temperature applications.