High-performance organic thermoelectric modules based on flexible films of a novel n-type single-walled carbon nanotube

Abstract

Organic thermoelectric materials are emerging green energy materials, where n-type candidates are of special interest due to the strong demand for thermoelectric modules with flexibility, light weight, large-area fabrication and ease of processing into versatile shapes. Here, an exciting novel strategy to prepare an n-type single-walled carbon nanotube (SWCNT) is proposed by diethylenetriamine (DETA) doping (electron donation) and subsequent CaH₂ treatment of the pristine SWCNT (p-type). The Seebeck coefficient and the electrical conductivity for the obtained DETA-CaH₂-SWCNT are −41.0 ± 1.5 μV K⁻¹ and 165 ± 10 S cm⁻¹, respectively. A possible mechanism is discussed for the p- to n-type conversion. Then, a multilayered alternating stacked structure is employed to construct thermoelectric modules which realize the conduction layers electrically in series and thermally in parallel. Importantly, the module containing 14 couples displays large open circuit voltages of 62 mV and 125 mV at temperature gradients (ΔT) of 55 K and 110 K, respectively, and a maximum output power of 649 nW at ΔT = 55 K. The strategy proposed here opens a new way to fabricate organic n-type materials and flexible thermoelectric modules. These promising results show great potential in fabrication and applications of flexible and wearable power-conversion devices for next-generation power generators and waste-heat-recovery systems.