Facile and Rapid Fabrication of Thermoelectric Legs via Filtration of Doped Polymer Suspension

ABSTRACT Optimization of leg dimensions, including thickness, is essential for maximizing output powers of thermoelectric (TE) generators. However, fabricating thick and uniform active films with conjugated polymers remains challenging, as doping processes are limited either by reduced solubility in polymer‐dopant blend solutions or by a trade‐off between dopant diffusion and doping stability. Here, a vacuum filtration method is introduced to fabricate tens‐of‐micrometers‐thick films within a few seconds by selectively collecting large, doped polymer particles from a polymer‐dopant suspension. The polymer particles form smooth, thick, uniformly doped, and highly flexible TE films via interparticle coalescence, while the short‐conjugated polymers and inactive dopants are effectively removed during filtration, thereby greatly enhancing the TE performance. The ≈60‐µm‐thick doped polymer films are integrated to fabricate fingertip‐sized TE generators, which exhibit high output powers up to 2.00 µW at Δ T = 15.2 K, yielding a record‐high normalized areal power density (209 µW m −2 K −2 ) and enabling successful electronic device operations using body heat. It is believed that the vacuum filtration method offers a new experimental protocol for fabricating organic TE generators as well as for gaining deep insights into the effects of solution‐state doping on the electrical and structural properties of conjugated polymers.