Achieving high thermoelectric properties in PEDOT:PSS/SWCNTs composite films by a combination of dimethyl sulfoxide doping and NaBH4 dedoping

Incorporating single-walled carbon nanotubes (SWCNTs) can effectively optimize the thermoelectric properties of poly(3,4-ethylenedioxithiophene):poly(styrenesulfonate) (PEDOT:PSS). However, the thermoelectric performance of flexible PEDOT:PSS/SWCNTs composites is still undesired due to the contradiction between electrical conductivity (sigma) and Seebeck coefficient (S). Here, we adopt dimethyl sulfoxide (DMSO) doping and NaBH4 dedoping to achieve high thermoelectric properties of PEDOT:PSS/SWCNTs composite film by simultaneously improving sigma and S. The PEDOT:PSS/SWCNTs composite with 60 wt% SWCNTs exhibits the highest power factor of 411 mu Wm(-1) K-2, originating from high sigma of 1718 S cm(-1) and high S of 49 mu V K-1. The high sigma is derived from the improved carrier transport by insulating PSS removal, the transition of PEDOT chains with ordered stacking structures, and the formed three-dimensional conductive network between PEDOT:PSS and SWCNTs. As well, the decreased carrier concentration induced by the reduction of oxidation level of PEDOT:PSS after NaBH4 dedoping leads to a compromise between sigma and S. Besides, a home-made thermoelectric device, fabricated using eight pieces of as-prepared PEDOT:PSS/SWCNTs composite films, shows an output power of 391 nW at a temperature difference of 20 K. Our work indicates that the combination of DMSO doping and NaBH4 dedoping can extend to promote the thermoelectric properties of flexible thermoelectric composite films.

Automated summary

By doping with DMSO and dedoping with NaBH4, the thermoelectric properties of PEDOT:PSS/SWCNTs composite film can be significantly improved, achieving high electrical conductivity and Seebeck coefficient. The high electrical conductivity is achieved by removing insulating PSS, changing the stacking structure of PEDOT chains, and forming a three-dimensional conductive network between PEDOT:PSS and SWCNTs. Dedoping with NaBH4 reduces the oxidation level of PEDOT:PSS, leading to a compromise between electrical conductivity and Seebeck coefficient.