Interface regulation of polyethyleneimine/carbon nanotubes by triethylene glycol to enhance thermoelectric performance

Faced with global energy sustainability and carbon neutrality demands, single-walled carbon nanotubes (SWCNTs) are promising for flexible thermoelectric (TE) applications but limited by severe agglomeration, high intrinsic thermal conductivity, and poor air stability of n-type derivatives. Herein, we report a novel n-type triethylene glycol/polyethyleneimine/SWCNT (TEG/PEI/SWCNT) composite film via facile drop-casting, where TEG (key co-dopant) dominates PEI/SWCNT interfacial regulation. TEG forms strong intermolecular interactions with PEI, remarkably enhancing PEI wettability on SWCNTs. This TEG-mediated interface modulation facilitates SWCNT dispersion into uniform networks (well-controlled bundle diameters), strengthens inter-bundle bonding (boosting carrier mobility and suppressing air molecule intrusion), and optimizes PEI-to-SWCNT carrier injection, alleviating excessive carrier concentration while increasing the Seebeck coefficient. The TEG-modulated film exhibits excellent performance: maximum power factor (PF) of 122 μW·m−1·K−2 at room temperature, 13-day stable n-type characteristics in ambient air, and monotonically increasing electrical conductivity up to 160 °C. A flexible TE device (five p-n junction pairs) based on this composite delivers 2.9 μW maximum output power under a 50 K temperature gradient. This TEG co-doping strategy, centered on precise PEI/SWCNT interface regulation, offers a simple, scalable route to high-performance flexible n-type carbon-based TE films, addressing key SWCNT-based TE bottlenecks.