Won, Jongin Mun, Yeongjun Kang, Yeong A. Park, Woomin Kim, Hyun-Sik Kim, Jungwon Jang, Kwang-Suk 2025-07-18T03:00:11Z 2025-07-18T03:00:11Z 2025-07-18 2025-09 1385-8947 https://pubs.kist.re.kr/handle/201004/152759 We report a dual advance in wearable thermoelectrics by combining a materials-level doping strategy with a device-level architectural innovation. Freestanding, ultra-flexible Ag2Se films are doped with trace amounts (tens of ppm) of Cu2Se nanoparticles, yielding a dramatic enhancement in thermoelectric performance. At an optimal Cu2Se doping of 50 ppm, the n-type Ag2Se films achieve a room temperature zT of-0.55 (versus-0.46 for undoped films) while maintaining an extraordinary bending radius of 0.4 mm. This improvement is attributed to a finely tuned carrier concentration and increased phonon scattering imparted by the Cu2Se nanoparticle inclusions, leading to a favorable balance of Seebeck coefficient, electrical conductivity, and thermal conductivity. Building on this high-performance flexible freestanding film, we design and experimentally demonstrate a novel vertical thermoelectric generator (TEG) architecture optimized for the predominantly out-of-plane temperature gradients of human body heat. The wearable TEG generates a maximum power/area of-2.6 mu W cm-2 from a Delta T of-10 degrees C on a human forearm, substantially outperforming conventional in-plane designs. Our work highlights a synergistic approach to advance wearable energy harvesting: enhancing the intrinsic zT of flexible thermoelectric materials while pioneering device architectures that bridge the gap between material innovation and practical energy harvesting from the human body. English Elsevier BV Enhanced zT of highly flexible freestanding Ag2Se films via Cu2Se nanoparticle doping for wearable thermoelectric generator applications Article 10.1016/j.cej.2025.165068 1 Chemical Engineering Journal, v.519 Chemical Engineering Journal 519 N scie scopus 001518608000020 Engineering, Environmental Engineering, Chemical Engineering Article SELENIDE THIN-FILMS SILVER CU2-XSE COPPER CU Wearable thermoelectric generartor Flexible thermoelectric films Silver selenide Nanoparticle doping Vertical device architecture