Wavy-structured thermoelectric device integrated with high-performance n-type carbon nanotube fiber prepared by multistep treatment for energy harvesting

Promoting the feasibility of thermoelectric (TE) devices toward wearable power generator application has sparked extensive interest for next-generation electronics. However, the lack of air-stable and high-performance n-type TE materials , which lag far behind those of p-type TE materials, and the deficiency of reasonable device structure design have always restricted the development of wearable thermoelectrics. Herein, we prepare a high-performance and air-stable n-type carbon nanotube fiber (CNTF) by multistep treatment and design a three-dimensional (3D) wavy-structured TE device to address the mentioned challenges. The multistep treatment including oleylamine (OA) doping followed by annealing process (250 °C) can contribute to an enhanced Seebeck coefficient of ~ −80 μV K −1 and an increased power factor of ~545 μW m −1  K −2 . Notably, it is found that the n-type CNTF prepared by this multistep treatment shows good air stability, which effectively diminishes the malignant effects of conventional annealing process on the air stability. Based on the optimized TE performance of an alternately p/n doped CNTF, the prepared wavy-structured generator integrated with two p-n couples can sustainably yield a stable amplitude of ~1.3 mV in voltage response during multiple fingering cycles and output a maximum power of ~8 nW under a temperature difference of ~5.7 K when the top of the device comes into contact with fingers. This paper provides a new insight into developing high-performance/air-stable n-type carbon nanotubes (CNTs) materials and designing reasonable device structure toward wearable applications.