Flexible hybrid thermoelectric films made of bismuth telluride-PEDOT:PSS composites enabled by freezing-thawing process and simple chemical treatment

Composite film type thermoelectric generators (TEG) have gained significant attention due to their flexibility, wearability, adaptability in various environments, and efficient thermoelectric (TE) output. However, the selection of the polymer support along with the TE fillers is a challenging task. Herein, flexible, high-performance TE composite films were developed by dispersing Bi_0·5Sb_1·5Te₃ (BST) particles into a poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (i.e. PEDOT:PSS) polymer through a drop-casting method. The power factor of the 10 wt% BST/PEDOT:PSS-based TE film has a value of 33.05 μW m^{− 1}⋅K^{− 2}, which is 17 times higher than that of the BST/poly (vinylidene fluoride) (i.e. PVDF)-film. A higher BST concentration (75 wt%) was required for the PVDF TE film to generate the 5.8 % power factor mentioned above. These results suggest that PEDOT:PSS is a potential candidate to replace the conventional PVDF polymer with enhanced TE properties due to its higher electrical conductivity. Furthermore, the flexible TEG (f-TEG) based on a 10 wt% BST/PEDOT:PSS film generates 25-fold higher TE electrical output power than the BST/PVDF-based f-TEG. Additionally, a finite element analysis was performed to understand the TE output of f-TEG with the same dimensions. Next, the f-TEG was tested in a real-automotive systems and the electrical outputs were (4.5 μA, 0.38 mV) from gripping the car steering wheel with a human hand (ΔT of 19 K), and (9 μA, 1.8 mV) from the car engine (ΔT of 30 K), respectively.