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Wang et al. Soft Sci 2023;3:34 https://dx.doi.org/10.20517/ss.2023.25 Page 9 of 26

Table 1. Room-temperature TE properties of PEDOT/inorganic composite films
S σ PF
Materials Preparation method 2 ZT Ref.
(μV/K) (S/cm) (μW/mK )
PEDOT:PSS/PF-Te Wet-chemical process ~ ~ 51.4 0.076 [41]
PEDOT:PSS/Ag Te Wet-chemical process -62.3 369.3 143.3 ~ [42]
2
PEDOT:PSS/Cu Se Wet-chemical process, 50.8 1,047.1 270.3 ~ [43]
x y
cold pressing
PEDOT:PSS/Cu Se Wet-chemical process, 78.2 470 287.4 ~ [44]
2
hot pressing
PEDOT:PSS/Bi-Te-based alloy Lithium intercalation 20.7 1,223.8 52.3 ~ [45]
PEDOT:PSS/Cu S Cold pressing ~ ~ 111.54 (393 K) ~ [46]
2
PEDOT:PSS/SnSe Vacuum filtration ~ ~ 24.42 (353 K) [47]
PEDOT:PSS/MoS Liquid-phase exfoliate 19.5 1,250 45.6 0.04 [48]
2
PEDOT:PSS/SiC-NWs Vacuum filtration 20.3 3,113 128.3 0.17 [49]
PEDOT:PSS/SiO Vacuum filtration 24.2 1,131.9 66.29 ~ [50]
2
PEDOT NWs/ Bi Te NWs Wet-chemical process 10.8 776.52 9.06 ~ [51]
2
3
PEDOT NWs/Te NWs Wet-chemical process 89.52 72.41 58.03 ~ [52]
NW: Nanowire; PEDOT: poly(3,4-ethylenedioxythiophene); PEDOT:PSS: poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid); PF:
PEDOT:PSS-functionalized; TE: thermoelectric; ZT: thermoelectric figure of merit.

Conducting polymer/carbon nanoparticle composite TE materials
Carbon nanoparticles, including graphene (GN) and CNTs, have been considered as promising candidates
to prepare conducting polymer-based composite materials through the vacuum filtration method owing to
their high electrical conductivities and decent Seebeck coefficient, which can remarkably improve the TE
performance of composite [55-57] . On the one hand, their large active conjugated fused aromatic ring systems
and the large specific surface areas can promote interfacial contacts between carbon nanoparticles and
conducting polymers significantly, thus resulting in a synergistic effect of the components. On the other
hand, the high thermal conductivities of the carbon nanoparticles can be mitigated by the conducting
polymers (usually with thermal conductivities of ~ < 1 W/mK) wrapping or connection. Therefore,
conducting polymer/carbon nanoparticle TE composites has received increasing attention.

Early in 2015, Xiong et al. fabricated highly conductive PEDOT:PSS/graphene composite films via vacuum
filtration, and the sample containing 3 wt% graphene in N,N-Dimethylformamide (DMF) showed a power
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factor of 38.6 μW/mK . Subsequently, a hydrazine treatment was used to further optimize the TE
performance of the composite, and finally, an estimated ZT value of 0.05 was obtained at room temperature
[Figure 7] . In another work, they fabricated PEDOT:PSS/SWCNT composite films using a similar
[58]
process, and the composites showed an increasing trend with the increase of SWCNT content . An
[59]
optimized power factor of 105 μW/mK was obtained at 60 wt% SWCNTs. And despite the high intrinsic
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thermal conductivity (~1,000 W/mK [60,61] ) of SWCNTs, the composite retained a low polymer-like thermal
conductivity around 0.15 to 0.36 W/mK due to less favorable paths for thermal energy transport caused by
the PEDOT:PSS connection between tube-tube junctions; therefore, a maximum ZT value of 0.12 was
obtained. Also, the TE properties of some other PEDOT:PSS/SWCNTs and PEDOT:PSS/GN composite
films fabricated by a similar vacuum filtration process with different post-treatment techniques were
reported [62-65] . For example, Deng et al. prepared free-standing PEDOT:PSS/SWCNT composite films with
an ionic liquid (IL) treatment using a vacuum filtration method [Figure 8] . The ion-exchange effect and
[64]
promotion of SWCNT dispersion by the IL realized a synergistic boost of electrical conductivity and a
Seebeck coefficient. The maximum power factor reached 182.7 ± 9.2 μW/mK at room temperature. Another
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