Wearable Inorganic Yarn Thermoelectric Generator Based on Solution-Processed Silver Selenide

Abstract: Thermoelectric generators (TEGs) are a promising strategy for harvesting body heat to power wearable electronics. However, the development of a TEG that combines high mechanical durability, effective utilization of vertical temperature gradients, and scalable fabrication remains a major challenge exacerbated by the inherent brittleness of most inorganic thermoelectric materials. We report a TEG where cotton yarn serves as a flexible substrate that is coated with silver selenide (Ag₂Se), which is an intrinsically ductile thermoelectric material. Ag₂Se is coated on cotton yarns by a simple solution process that eliminates the need for high temperatures while preserving scalability and mechanical flexibility. Systematic optimization of the Ag₂Se-coated yarns resulted in a figure of merit of 0.343 at 295 K. A yarn-based TEG was fabricated that maintained excellent durability over 5000 bending cycles with a 6 mm radius of curvature. Under real-world conditions for wearable applications, the yarn TEG generated 0.326 µW at a temperature difference of 2.8 K (stationary) and 0.604 µW at a temperature difference of 4.4 K (walking). This work establishes a scalable and practical platform for integrating high-performance inorganic thermoelectric materials into flexible and wearable energy-harvesting systems.