Construction of a cement–rebar nanoarchitecture for a solution-processed and flexible film of a Bi₂Te₃/CNT hybrid toward low thermal conductivity and high thermoelectric performance

Solution processability and flexibility still remain major challenges for many thermoelectric (TE) materials, including bismuth telluride (Bi₂Te₃), a typical and commercially available TE material. Here, we report a new solution-processed method to prepare a flexible film of a Bi₂Te₃/single-walled carbon nanotube (SWCNT) hybrid, where the dissolved Bi₂Te₃ ion precursors are mixed with dispersed SWCNTs in solution and recrystallized on the SWCNT surfaces to form a “cement–rebar”-like architecture. The hybrid film shows an n-type characteristic, with a stable Seebeck coefficient of −100.00 ± 1.69 μV K⁻¹ in air. Furthermore, an extremely low in-plane thermal conductivity of ∼0.33 W m⁻¹ K⁻¹ is achieved at 300 K, and the figure of merit (ZT) reaches 0.47 ± 0.02. In addition, the TE performance is independent of mechanical bending. The unique “cement–rebar”-like architecture is believed to be responsible for the excellent TE performances and the high flexibility. The results provide a new avenue for the fabrication of solution-processable and flexible TE hybrid films and will speed up the applications of flexible electronics and energy conversion.