Cu₂Se hybridization advances high-performance flexible single-walled carbon nanotube based thermoelectrics

Single-walled carbon nanotubes (SWCNTs) with unique electronic structures, high electrical conductivity and processability have shown great promise for flexible thermoelectric devices. However, the inherently high thermal conductivity of SWCNTs significantly constrains their thermoelectric performance. To overcome this limitation, this study presents a composite of SWCNTs hybridized with the strategically selected cuprous selenide (Cu₂Se) through cold pressing. The obtained SWCNTs/Cu₂Se composite films achieve a notable room-temperature power factor of 16.39 µW cm^-1 K^-2, which is the highest among SWCNT-based composite films, and representing a 500 % enhancement in figure of merit value compared to pure SWCNT films, and the power factor further increases to 26 µW cm^-1 K^-2 at 373 K. This enhancement is attributed to the energy filtering effect at the Cu₂Se-SWCNT interface, which synergistically boosts both the electrical conductivity and Seebeck coefficient. Additionally, Cu₂Se coupled with the increased interface density facilitates phonon scattering, substantially reducing thermal conductivity of the composite films by about 45 %, while cold pressing densifies the composite films, significantly enhancing their electrical conductivity. A flexible device based on the composite films achieved a maximum output power density of 77μW cm^-2 under a 40 K temperature difference. This work introduces a new strategy for designing SWCNT-based thermoelectric materials and offers valuable insights for advancing flexible thermoelectric devices.