Electrolyte‐Based One‐Shot Potential Application With Crosslinked Superbase Cation for Thermally Stable N‐Type Carbon Nanotubes With Tunable Thermoelectric Properties

Abstract Carbon nanotubes (CNTs) are promising organic thermoelectric (TE) materials, but their n‐doped state instability limits the development of all‐CNT TE modules. Previously, a bicyclic guanidine superbase has been identified as an efficient and thermally stable n‐type dopant, whose crosslinked version with two superbases joined by a decenylene chain enhances their thermal and humidity stability. In this study, first, a non‐crosslinked superbase with a decyl group is synthesized and used to dope CNTs. The structural effects on doping stability are evaluated. Stability under heat and humidity reveals that crosslinking is crucial to maintaining n‐type behavior. The planar molecular shape of the superbase moiety and hydrophobic alkyl chains contribute, respectively, to the thermal and humidity stability of n‐doped CNTs. Second, a crosslinked superbase cation is incorporated into an electrolyte for electrochemical doping. The superbase cation stabilizes the doped CNTs, which retain n‐type properties even under aging (1000 h at 100 °C in air). This approach allows precise control over electron and hole densities, increases TE power factors (230 and 108 mW m ⁻¹ K ⁻² for p‐ and n‐type, respectively), and stabilizes doped states through coordination with cationic and anionic species, demonstrating the importance of molecular design in achieving stable, high‐performance n‐type CNTs.