Simple Layer-by-Layer Assembly Method for Simultaneously Enhanced Electrical Conductivity and Thermopower of PEDOT:PSS/ce-MoS₂ Heterostructure Films

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.