Boosting the Thermoelectric Properties of PEDOT:PSS via Low‐Impact Deposition of Tin Oxide Nanoparticles

Abstract

materials' efficiency to convert heat into electricity remains still quite low in the low-temperature range. To quantify the TE performances, the figure of merit zT is introduced, which is described by the equation = σ κ zT S T 2 , [4,5] where σ is the electrical conductivity, S the Seebeck coefficient, κ the thermal conductivity, and T the absolute temperature. Due to the intrinsically low thermal conductivity of polymeric TE materials, the power factor, which is described as PF = σS 2 , is the main factor to be improved. [6,7] However, σ and S influence each other and usually in an opposite way, meaning that when one of them increases, the other one will decrease. A large amount of research has been done to probe the relationship between these two variables and to try to improve them. [8][9][10] Poly(3,4-ethylenedioxy thiophene): poly(styrenesulfonate) (PEDOT:PSS, structure shown in Figure 1a) is one of the most studied among polymeric TE materials, being highly stable, easily processable, and showing the best TE properties for this family of materials so far. [11,12] Although various strategies including polar solvents treatment, acids/bases treatment, ionic liquids treatment, inorganic nanomaterials incorporation, etc. have been applied to improve the TE performance of PEDOT:PSS, [7] and PF as high as 380 µW m −1 K −2 can be achieved with the incorporation of 2D SnSe nanosheets, [13] effective and cost-effective methods simple enough that can be used for mass production are still lacking.Here we propose a new method to add "naked" nanoparticles (NPs) to PEDOT:PSS in order to improve its TE properties. The improvement in TE properties is achieved by a reorganization of the film structure induced by the NP addition via a specific interaction with the PSSchains. Key in this work is the use of "naked" NPs. Indeed, Zhang et al. proved the negative effect of the surface layer on inorganic Bi 2 Te 3 when embedded in PEDOT:PSS. [14] To incorporate "naked" inorganic NPs we selected a physical pathway for NP generation, namely spark discharge generation, which is one of the least expensive and most environmentally friendly methods to produce large amounts of NPs. [15,16] A flow of gas (Ar) can be used to carry the generated NPs towards the polymer target (see Figure 1b). Instead of applying the so-called impaction mode, where the NPs impinge vertically on the substrate, an alternative low Poly(3,4-ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS) exhibits valuable characteristics concerning stability, green-processing, flexibility, high electrical conductivity, and ease of property modulation, qualifying it as one of the most promising p-type organic conductors for thermoelectric (TE) applications. While blending with inorganic counterparts is considered a good strategy to further improve polymeric TE properties, only a few attempts succeed so far due to inhomogeneous embedding and the non-ideal organicinorganic contact. Here a new strategy to include nanoparticles (NPs) without any ligand termination inside ...

Gas Sensing and Thermoelectric Properties of Hybrid Composite Films Based on PEDOT:PSS and SnO or SnO2 Nanostructures

“…The increase in the electrical conductivity has been commonly attributed to the phase separation between PEDOT and PSS promoted by EG, which acts as a binder between PEDOT grains, facilitating charge transport. [ 14 ] Regarding the samples containing also the tin species, the mechanism behind the conductivity variation could be attributed to the interaction between Sn ions with oxygen from PSS − and the Coulombic interaction between PEDOT+ and the nanoparticles, as it has been recently suggested by Dong et al [ 26 ] . Some other authors reported an improvement in the thermoelectric performance of hybrid composites formed by PEDOT:PSS and Si nanoparticles owing to the changes in the polymeric molecular ordering involving increased Seebeck coefficient and reduced thermal conductivity.…”

“…In contrast, PEDOT:PSS has also been mixed either with carbon allotropies [23] or Bi or Se-based compounds [8,24] to improve its thermoelectric performance, while the use of oxide fillers such as ZnO [25] or SnO x has only been recently suggested. [26] In this work, both n-type SnO 2 and p-type SnO nanoparticles have been used as fillers in PEDOT:PSS-based hybrid layers, the performance of which were investigated in gas sensing and thermoelectrics. It is worth noting that p-type semiconducting binary oxides, such as SnO, are scarce, contrary to their n-type counterparts, hence their use is still underexplored despite their great potential.…”

“…In contrast, PEDOT:PSS has also been mixed either with carbon allotropies [ 23 ] or Bi or Se‐ based compounds [ 8,24 ] to improve its thermoelectric performance, while the use of oxide fillers such as ZnO [ 25 ] or SnO x has only been recently suggested. [ 26 ]…”

Synergistically Improving Flexibility and Thermoelectric Performance of Composite Yarn by Continuous Ultrathin PEDOT:PSS/DMSO/Ionic Liquid Coating

“…The rapid development of flexible and wearable electronics puts forward high requirements for wearable power supply systems. − Thermoeletric (TE) devices, which can harvest energy from the human body heat and convert it into electric power, have gained considerable attention because they can be used to provide energy for wearable devices sustainably and uninterruptedly. − To realize flexible and wearable application, various fiber-based TE devices were designed and prepared due to their advantages of flexibility, wearing comfort, and designable structure. Based on former studies, most fiber-based TE devices are obtained by combining fabrics with various TE materials, such as the poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS), poly­(3-hexylthiophene) (P 3 HT), PbTe, Sb 2 Te 3 , and Bi 2 Te 3 . − Compared with the brittle inorganic TE materials, the use of conducting polymers such as PEDOT, polythiophene (PTh), and polypyrrole (PPy) as coating layers to construct fiber-based TE devices offers numerous advantages of great flexibility, light weight, and low thermal conductivity. − Typically, PEDOT:PSS is the most commonly used organic TE material, which has high electrical conductivity, water solubility, and easy processability. , …”

“…16−18 Typically, PEDOT:PSS is the most commonly used organic TE material, which has high electrical conductivity, water solubility, and easy processability. 19,20 In order to be wearable, the fiber-based TE materials must be flexible enough to withstand the friction and bending during body movement, so as to reduce the unstable and attenuated performances. 21 However, pristine PEDOT:PSS has a Young's modulus of ∼500 MPa and a maximum tensile strain (ε) of ∼5%, making it too hard and brittle to be stably used in wearable TE devices.…”