Thermoelectric properties of PEDOT: PSS and acid-treated SWCNT composite films

We investigated the thermoelectric properties of composite films that consist of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and single-walled carbon nanotubes (SWCNTs). Thin films with 5−10 μm thickness of PEDOT:PSS/SWCNT and PEDOT:PSS/acid-treated SWCNT (AC-SWCNT) were prepared by varying the CNT content to determine their power factor. Both PEDOT:PSS/SWCNT and PEDOT:PSS/AC-SWCNT films showed an increase in their power factors with CNT content. The power factor values of PEDOT:PSS/AC-SWCNT films were higher than those of PEDOT:PSS/SWCNT films over the entire experimental range, which was mainly attributed to the significantly increased electrical conductivity. Thus, a series of PEDOT:PSS/AC-SWCNT freestanding films with 100−250 μm thickness were synthesized, and the same sample was used to measure electrical conductivity, Seebeck coefficient, and thermal conductivity to calculate the in-plane figure-of-merit ZT values. The composite films exhibited lower ZT values than those of PEDOT:PSS and AC-SWCNT films because of the high in-plane thermal conductivity caused by the dimensional anisotropy of AC-SWCNTs.