Thermoelectric properties of nanocomposite thin films prepared with poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) and graphene

Carbon nanotubes (CNTs), either single wall carbon nanotubes (SWNTs) or multiwall carbon nanotubes (MWNTs), can improve the thermoelectric properties of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), but it requires addition of 30-40 wt% CNTs. We report that the figure of merit (ZT) value of PEDOT:PSS thin film for thermoelectric property is increased about 10 times by incorporating 2 wt% of graphene. PEDOT:PSS thin films containing 1, 2, 3 wt% graphene are prepared by solution spin coating method. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses identified the strong pi-pi interactions which facilitated the dispersion between graphene and PEDOT:PSS. The uniformly distributed graphene increased the interfacial area by 2-10 times as compared with CNT based on the same weight. The power factor and ZT value of PEDOT:PSS thin film containing 2 wt% graphene was 11.09 mu W mK(-2) and 2.1 x 10(-2), respectively. This enhancement arises from the facilitated carrier transfer between PEDOT: PSS and graphene as well as the high electron mobility of graphene (200 000 cm(2) V-1 s(-1)). Furthermore the porous structure of the thin film decreases the thermal conductivity resulting in a high ZT value, which is higher by 20% than that for a PEDOT: PSS thin film containing 35 wt% SWNTs.