High-Performance thermoelectric generator based on n-Type flexible composite and its application in Self-Powered temperature sensor

Thermoelectric generators (TEGs) present a promising alternative to conventional power generation technologies for powering low-power wearable electronics. However, there are few n-type organic materials with high thermoelectric and mechanical performance. In this study, a polymer (PEI-PFA) via low temperature polycondensation between polyethyleneimine (PEI) and paraformaldehyde (PFA) is synthesized, and this is the first reported polymer which can be not only used as a novel n-type dopant of single-walled carbon nanotubes (SWCNTs) due to the PEI moieties, but also endow the composites with good flexibility due to the synthesized hemiaminal dynamic covalent networks. Subsequent addition of sodium hydroxide (NaOH) can further enhance the electron conductivity. The resulting SWCNT/PEI-PFA/NaOH composite film exhibits an excellent electrical conductivity of 1641.22 S cm−1, a power factor of 115.77 μW m−1 K−2, a tensile strength of 36.4 MPa, and flexibility up to 21 % strain. In addition, a self-powered sensor is assembled, which can efficiently monitor temperature changes and strain deformations. Moreover, a thermoelectric device containing five p-n junctions based on the pristine SWCNTs and SWCNT/PEI-PFA/NaOH composite is prepared, and a high output power of 5.33 μW at the temperature difference of 75.2 K is achieved. This work presents a promising approach to developing flexible n-type thermoelectric materials for self-powered wearable electronics.