Stretchable p/n ‐Pair Thermoelectric Fibers Based on Core (Ag)–Shell (Ag ₂ Se) Structure for Wearable Electronics

The development of stretchable p/n‐pair thermoelectric (TE) fibers holds significant promise for multifunctional wearable electronics, yet remains challenging due to complex processing and limited mechanical durability. Here, a novel strategy is presented for the facile fabrication of stretchable Ag@Ag 2 Se‐based TE fibers using a selective in situ chemical reduction process, eliminating the need for thermal treatment or specialized equipment. The resulting fibers feature a robust core–shell architecture, with conductive Ag cores and n‐type Ag 2 Se shells, achieving a Seebeck coefficient of −96.75 µV K −1 under 100% strain and stable electrical conductivity under 200% strain. Notably, the fibers exhibit excellent cyclic stability with ΔV/V 0 maintained within 1.75% under mechanical deformation. When patterned into p/n‐pair arrays through localized chemical treatment, the fibers function as efficient energy harvesters and strain/temperature sensors. Integrated into wearable platforms, these fibers demonstrate simultaneous mechanical and thermal sensing and effective energy harvesting from body heat. This work establishes a versatile platform for scalable, miniaturized, and multifunctional TE fiber systems, advancing the future of smart textiles and wearable electronics.