Facile preparations of layer-like and honeycomb-like films of poly(3,4-ethylenedioxythiophene)/carbon nanotube composites for thermoelectric application

Abstract

The morphologies of conjugated polymers and their composites have significant effects on their thermoelectric (TE) performance. In this study, flexible films of poly (3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotube (PEDOT:PSS/SWCNT) composites were fabricated by convenient solution mixing of commercialized PEDOT:PSS and SWCNT. Their morphologies displayed remarkable dependency on film-formation procedure. An unusual submicron-size honeycomb-like porous structure was observed for the vacuum-filtration composite film, whereas the solution-casting film showed a parallel layer-like morphology. Importantly, the film with honeycomb-like structure revealed a much higher power factor (~20.68 μW m−1 K−2) than the layer-like structure film (~8.67 μW m−1 K−2). Furthermore, the composite film with submicron-size honeycomb-like porous structure also reveals higher TE performance than most micron-sized porous materials and dense solid film with nano- or micro-structure of the neat PEDOT and PEDOT/SWCNT composites. After H2SO4 post-treatment, the power factor can be enhanced further to 45.72 ± 1.76 μW m−1 K−2. Therefore, the PEDOT:PSS/SWCNT composites with submicron honeycomb-like porous morphology are promising for flexible TE application.