Flexible Thermoelectrics for Wearable Electronics: Trends and Benchmarks in Solid‐State and Ionic Materials, Textile Architectures, Interface Engineering, and Device Performance

Abstract Thermoelectric generators (TEGs) convert waste heat into electricity via the Seebeck effect, offering a compelling route for self‐powered systems. While traditional TEGs have relied on rigid inorganic semiconductors, recent advances have pivoted toward organic, hybrid, 2D, and ionic thermoelectric materials that provide mechanical flexibility, structural tunability, and compatibility with wearable electronics. Emerging innovations including ionic thermopower modulation, textile‐based architectures, and hybrid TEG–supercapacitor systems enable multifunctional capabilities such as energy harvesting, thermal and pressure sensing, and real‐time power delivery. This review provides a comprehensive analysis of material development, interfacial engineering, and device integration strategies that define the evolving landscape of thermoelectric technologies. Special emphasis is placed on solid‐state and ionic TEGs, flexible and textile‐compatible platforms, and hybrid systems that combine thermoelectric generation with energy storage or other transduction mechanisms. Key performance metrics such as mechanical durability, interfacial stability, and Seebeck coefficient tunability are critically discussed. Finally, emerging challenges and future opportunities in sustainable material selection, large‐area manufacturing, and the design of adaptive, wearable energy systems for the next generation of self‐powered electronics are outlined.