Simple Layer-by-Layer Assembly Method for Simultaneously Enhanced Electrical Conductivity and Thermopower of PEDOT:PSS/ ce-MoS<inf>2</inf> Heterostructure Films

Abstract

The organic/inorganic composites are considered as a promising strategy to gain high thermoelectric (TE) performance. Although many efforts have been focused on composites, complicated methods are real hindrance to the development of TE materials. Here, we demonstrate a potential TE thin film comprising highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and chemically exfoliated MoS2 (ce-MoS2) nanosheets by layer-by-layer (LbL) assembly method. This work achieves the effective integration of composite, treatment, and electron transfer based on the advantages of PEDOT:PSS and ce-MoS2. On the one hand, the negative charged ce-MoS2 nanosheets facilitate the formation of heterostructure TE films with positive charged PEDOT and reduce the oxidation level of PEDOT, which would favor an enhanced thermopower (21.9 μV K-1). On the other hand, the simultaneous enhancement in the electrical conductivity (867 S cm-1) of PEDOT:PSS/ce-MoS2 composite film is caused by dimethyl sulfoxide (DMSO) worked as the dispersion of ce-MoS2, which corresponds to the removal of the excess nonconductive PSS and the molecular conformation arrangement of PEDOT:PSS. This LbL assembly method incorporating electron-rich ce-MoS2 and DMSO has been confirmed to be an effective strategy to yield a simultaneous enhancement of electrical conductivity and thermopower. The optimized power factor is achieved to be 41.6 μW m-1 K-2 at the layer number of 4, which surpass that of the single-layer PEDOT:PSS film by a factor of 5. This work may provide a fundamental understanding of and design principles on how to build PEDOT:PSS-based composite films with highly enhanced TE performance, which can be potentially used in TE energy-harvesting systems.