탄소나노튜브-셀룰로스 복합체의 n-형 열전 성능 및 공기 안정성 향상을 위한 도핑 전략 탐구

Abstract

Single-walled carbon nanotubes (SWCNTs) have attracted much attention in developing low-cost and flexible thermoelectric (TE) materials due to their great electrical and mechanical properties. Interestingly, SWCNTs have shown broad electronic tunability for either p-type or n-type TE characteristics through specific strategies, with potential high TE performance. However, it has been challenging to achieve SWCNTs with highly stable n-type features as they can be easily re-oxidized and converted to p-type in ambient conditions. In this study, we propose a novel approach for n-type conversion of SWCNTs using polyethyleneimine (PEI) as a stable n-type dopant. Specifically, we developed a hybrid doping method that combines addition and immersion processes enhancing the TE performance and long-term stability of SWCNT at the same time. As a result, we obtained an electrical conductivity of 860 S cm−1, a Seebeck coefficient of 36 μV K−1, and consequently, a maximum power factor of 95 μW m−1 K−2, which is remarkable improvement in n-type TE materials. Moreover, the hybrid doping demonstrated outstanding long-term stability by inhibiting the oxidation of SWCNT-CMC at nanoscales, which ensures the initial power factor even after storing in ambient for a month. This work could open up a new way for efficient n-type tuning of CNT-based TE materials and their practical applications in printed and flexible TE devices.