Superflexible Inorganic Ag₂ Te_0.6 S_0.4 Fiber with High Thermoelectric Performance

Fiber-based inorganic thermoelectric (TE) devices, owing to the small size, light-weight, flexibility, and high TE performance, are promising for applications in flexible thermoelectrics. Unfortunately, current inorganic TE fibers are strictly constrained by limited mechanical freedom because of the undesirable tensile strain, typically limited to a value of 1.5%, posing a strong obstacle for further application in large-scale wearable systems. Here, a superflexible Ag₂ Te_0.6 S_0.4 inorganic TE fiber is demonstrated that provides a record tensile strain of 21.2%, such that it enables various complex deformations. Importantly, the TE performance of the fiber shows high stability after ≈1000 cycles of bending and releasing processes with a small bending radius of 5 mm. This allows for the integration of the inorganic TE fiber into 3D wearable fabric, yielding a normalized power density of 0.4 µW m^-1 K^-2 under the temperature difference of 20 K, which is approaching the high-performance Bi₂ Te₃ -based inorganic TE fabric and is nearly two orders of magnitude higher than the organic TE fabrics. These results highlight that the inorganic TE fiber with both superior shape-conformable ability and high TE performance may find potential applications in wearable electronics.