Green solvent-processed n-type fluorinated salt/single-walled carbon nanotube film with high performance for multifunctional wearable thermoelectric devices.

Developing high-performance n-type thermoelectric materials is critical for advancing wearable energy harvesting and sensing technologies. Herein, a series of novel n-type single-walled carbon nanotube (SWCNT) composite films are doped with fluorinated salts via a simple vacuum filtration method. Moreover, ethanol, as an environmentally friendly solvent, is utilized in the material preparation process, effectively replacing toxic and harmful solvents. Through systematic molecular design and density functional theory (DFT) analysis, it demonstrates that cation structure modulates doping efficiency, with SWCNT/(1-pentyl)triphenylphosphonium fluoride (PTPF) achieving a power factor of 293.7 μW∙m-1∙K-2. This superior performance, attributed to enhanced π-π interactions and uniform dispersion, represents a high value reported for such materials fabricated using eco-friendly solvent and vacuum filtration. Leveraging this material, we fabricated a flexible wristband thermoelectric generator (TEG) that integrates energy harvesting, high-resolution temperature sensing (0.08 K), and digital signal encoding via Morse code, driven by body-environment temperature differences. The device exhibits excellent cycling stability (>100 cycles) and rapid response (<1 s), showcasing its potential for self-powered wearables, medical monitoring, and human-machine interaction. This work represents a molecular-design-driven exploration of fluorinated salts in n-type SWCNT systems, providing key insights into cation-modulated doping for advancing sustainable, high-performance thermoelectric material.