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

Recent Progress of Two-Dimensional Thermoelectric Materials

“…As a potential high-performance thermoelectric material, conductive polymers exhibit unique advantages such as a low thermal conductivity, flexibility, lightweight, and efficient solution processability [9,[198][199][200][201][202]. However, more work needs to be done to further improve their thermoelectric performance to use them in flexible and wearable thermoelectric devices.…”

Carbon Nanotube-Based Organic Thermoelectric Materials for Energy Harvesting

“…The improvement in carrier mobility is attributed to the band alignment, which attracts hole carriers to CNTs whose mobility is much higher than that of the polymer. In addition, the energy barrier at the interface of CNT and PANI may play an important role [122,123,124,125,126]. Theoretical study suggests that the power factor can be remarkably improved by imposing an energy barrier at the interface of conjugated carbon structures [118,127,128].…”

Layer‐by‐layer assembly and electrically controlled disassembly of water‐soluble Poly(3,4‐ethylenedioxythiophene) derivatives for bioelectronic interface

“…The electroactive behavior of PEDOT was utilized not only for control of drug delivery [ 23,24 ] but also for neural engineering by applying redox‐triggered release. [ 25 ] However, PEDOT‐based LBL systems consist of materials (inorganic/organic) other than PEDOT derivatives, [ 1,26 ] and the LBL assembly of only PEDOT derivatives has not yet been investigated.…”

“…Wang et al, in 2018, while utilizing electrical conductive properties of PEDOT, demonstrated an enhancement in the thermoelectric property when a PEDOT polymer composite and chemically exfoliated MoS 2 were spin‐coated on the glass surface. [ 26 ] On the other hand, even if the PEDOT was not directly involved as the polymer in LBL, the conductive nature can still be used for different applications, such as in 2017, when Pappa et al used PEDOT: PSS as substrate not as a polymer layer for poly‐L‐lysine and polystyrenesulfonate for LBL assembly to functionalize an organic electrochemical transistor to sense mRNA. [ 32 ]…”