Fully Organic Nanocomposites with High Thermoelectric Power Factors by using a Dual‐Stabilizer Preparation

Abstract

The thermoelectric properties of fully organic nanocomposites were investigated, for which meso‐tetra(4‐carboxyphenyl) porphine (TCPP) and poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were used as instrinically conductive and semiconducting stabilizers, respectively. The electrical conductivity (σ) of these dual‐stabilizer organic composites increased to approximately 9500 S m−1 as the concentrations of both the multiwalled carbon nanotubes (MWNTs) and PEDOT:PSS were increased. The thermopower (or Seebeck coefficient, S) and thermal conductivity, however, remained relatively unaffected by the increase in concentration (≈40 μV K−1 and ≈0.12 W m−1 K−1, respectively). Replacing MWNTs with double‐walled carbon nanotubes (DWNTs) increased σ and S to approximately 96 000 S m−1 and 70 μV K−1, respectively, at 40 wt % DWNTs. This study suggests that σ and S can be simultaneously tailored by using multiple stabilizing agents to affect the transport properties of the junctions between nanotubes. Combining semiconducting and intrinsically conductive molecules as CNT‐stabilizers has led to a power factor that is among the best for a completely organic, free‐standing film (≈500 μW m−1 K−2). These flexible, segregated‐network nanocomposites now exhibit properties that rival the more conventional inorganic semiconductors, particularly when normalized by the mass.

Flexible Thermoelectric Materials and Generators: Challenges and Innovations

“…c) Schematic illustration of electrically connected but thermally disconnected junctions in carrier‐transport tunnels. d) Power factors ( S 2 σ) of composites with different CNT and stabilizer types plotted against CNT content …”

Enhanced thermoelectric properties of hybridized conducting aerogels based on carbon nanotubes and pyrolyzed resorcinol–formaldehyde resin

“…By manipulating the carrier transport properties of the junctions between CNTs in the segregated-network structure with intrinsically conducting and semiconducting polymers, a power factor of up to 500 mW m À1 K À2 was generated [32]. These researches have provided the prominent potential of using carbon-based materials as TE materials.…”

“…Nevertheless, a breakthrough was achieved by controlling the doping and oxidation level of PEDOT, which generated ZT values comparable to those of some traditional inorganic materials [24][25][26][27][28]. Organic/inorganic hybridization is another promising way to improve the thermoelectric performance of polymers [29][30][31][32][33][34][35][36][37][38][39][40][41].…”

“…For example, Yu and co-workers [30][31][32] found that a and s could be independently regulated by forming a segregated-network structure of carbon nanotubes (CNTs) within polymer matrices. By manipulating the carrier transport properties of the junctions between CNTs in the segregated-network structure with intrinsically conducting and semiconducting polymers, a power factor of up to 500 mW m À1 K À2 was generated [32].…”

Carbon-Based Materials for Thermoelectrics

“…Specifically, 30-40 wt% (weight percent) CNT is required to enhance the TE property of PVAc/DWCNT/TCPP [204] PANI/MWCNT(c) [186] P3HT:SWCNT(a) [199] PVAc/SWCNT(a) [127] PANI/MWCNT(d) [187] P3HT: MWCNT [200] PVAc/SWCNT(b) [206] PEDOT:PSS/SWCNT/GA [205] P3HT:SWCNT(b) [215] Nafion/FWCNT [179] PEDOT:PSS/SWCNT/PVAc [172] P3HT:SWCNT(c) [211] PANI/SWCNT(a) [182] PEDOT:PSS/SWCNT [190] PANI/graphene/PANI/DWCNT [202] PANI/SWCNT(b) [208] PEDOT:PSS/DWCNT/TCPP [191] PANI/SWCNT(c) [214] PEDOT:PSS/SWCNT [192] PANI/graphne/PANI/DWCN-PEDOT:PSS [203] PANI/SWCNT(d) [212] PEDOT:PSS/graphene/MWCNT [211] PANI/SWCNT/Te [183] PEI-DWCNT/PVP-graphene [221] PANI/DWCNT [188] PEDOT:PSS/DWCNT [193] PEI/SWCNT/PEI [220] PANI/MWCNT(a) [184] PPy/MWCNT [195] PEI/SWCNT/NaBH [219] 4 PANI/MWCNT(b) [185] PPy/SWCNT [196] PEI:DWNT:graphene [221] p-type n-type PEDOT:PSS, while only 2 wt% graphene can increase the ZT of PEDOT:PSS by 10 times. Strong -bonding that facilitates the dispersion was observed in graphene-embedded PEDOT:PSS thin films.…”