Solvent polarity-dependent charge polarity recoverable polyaniline-carbon nanotube composites

Abstract

N-type organic thermoelectric materials face critical challenges from oxygen-induced p-doping, compromising their stability and performance. This study introduces a solvent-mediated polarity control strategy to suppress oxygen doping in polyaniline/single-walled carbon nanotube (PANI/SWCNT) hybrids, enabling air-stable n-type behavior. By modulating solvent polarity (via the ET parameter), we achieve reversible p-to-n polarity switching without chemical dopants. Low-polarity solvents (ET < 50 kcal mol-1) and the cold-compression process induce n-type characteristics with a high power factor of 911.3 μW m-1 K-2, while high-polarity solvents restore p-type behavior. Theoretical modeling reveals solvent-regulated interfacial charge transfer, where low-polarity solvents promote electron donation from PANI to SWCNTs. Cold-compression further enhances electrical conductivity (2.3-fold increase) while maintaining Seebeck coefficients, yielding a 253% power factor improvement. The n-type films exhibit exceptional air stability, retaining 73% conductivity and 96% Seebeck coefficient after 4-day ambient exposure. In addition, cyclic polarity reversibility is demonstrated through solvent immersion, highlighting the system’s robustness. This work demonstrates a universal platform for designing oxygen-immune n-type organic electronics with industrial viability, bridging the gap between fundamental charge-transport understanding and scalable material engineering.