Size Dependence of Electrical Conductivity and Thermoelectric Enhancements in Spin‐Coated PEDOT:PSS Single and Multiple Layers

Andrei, Virgil; Bethke, Kevin; Madzharova, Fani; Beeg, Sebastian; Knop‐Gericke, Axel; Kneipp, Janina; Rademann, Klaus

doi:10.1002/aelm.201600473

Cited by 44 publications

(42 citation statements)

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“…These results are in good agreement with previously reported activation energies for PEDOT:PSS films. [24] In contrast to previous reports, [25] we observe increasing electrical conductivity with decreasing film thickness. This might be related to an increased disorder in the films with increasing film thickness.…”

Section: Electrical Conductivitycontrasting

confidence: 98%

Complete Thermoelectric Characterization of PEDOT:PSS Thin Films with a Novel ZT Test Chip Platform

Linseis

Hassan

Reith

et al. 2018

Physica Status Solidi (a)

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For the first time, a complete thermoelectric characterization of PEDOT:PSS thin films is performed with a novel lab‐on‐a‐chip measurement platform, which Is developed for the nearly simultaneous in‐plane ZT characterization. The electrical conductivity, the Seebeck coefficient, the thermal conductivity, and consequently the power factor and ZT values as a function of temperature in a single measurement run is experimentally determined. A clear correlation is found between the film thickness of PEDOT:PSS and the thermoelectric properties. While the electrical conductivity increases with decreasing thickness, the thermal conductivity shows a contrary behavior. Both parameters increase monotonically with increasing temperature between 173 and 373 K. The Seebeck coefficient exhibits the same temperature dependency but, in contrast to the previous two parameters, is almost independent of the PEDOT:PSS film thickness. Furthermore, it is demonstrated that a ZT chip, with a complete set of thermoelectric test structures, can be successfully used for a full thermoelectric characterization of conductive organic thin films. This translates into a major testing time advantage for the screening and optimization of promising organic materials during the R&D phase, which can serve as potential candidates for future thermoelectric applications and devices.

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Section: Electrical Conductivitycontrasting

confidence: 98%

Complete Thermoelectric Characterization of PEDOT:PSS Thin Films with a Novel ZT Test Chip Platform

Linseis

Hassan

Reith

et al. 2018

Physica Status Solidi (a)

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“…DMSO with NaOH dedoping ~15.8 ~785 ~19.6 [120] Post DMSO + Hydrazin dedoping 49.3 1310 318.4 [115] Sorbitol + TDAE dedoping 27.47 ~295 ~22.3 [111] HI + DMSO (post treatment) ~30.8 ~475 ~45.1 [114] DMSO and Sorbitol 11.98 1063 15.3 [121] H2SO4 + NaOH 39.2 2170 333.5 [91] Multi-layered DMSO 10.6 187 2.1 [122] Salt + DMF 28 1831 143.6 [108] H2SO4 149.47 65.82 147.1 [123] DMSO and EMIMBF4 post treatment ~23.5 ~680 ~37.6 [124] TEMPO-OH ~22.5 ~33 ~1.7 [125] Depicted in Figure 10 is a collection of thermopower-conductivity data from literature obtained for PEDOT:PSS subjected to different treatments; for completeness also data for the PEDOT:Tos system are plotted. As noticed before, the majority of the data does not follow the empirical -¼ power-law relationship between conductivity and thermopower observed for most doped thiophenes and other doped polymers.…”

Section: Pedot:pssmentioning

confidence: 99%

Conjugated Polymer Blends for Organic Thermoelectrics

Zuo

Abdalla

Kemerink

2019

Adv Elect Materials

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A major attraction of organic conjugated semiconductors is that materials with new, emergent functionality can be designed and made by simple blending, as is extensively used in e.g. bulk heterojunction organic solar cells. Here, we critically review doped blends based on organic semiconductors (OSC) for thermoelectric applications. Several experimental strategies to improve thermoelectric performance, measured in terms of power factor (PF) or figure-ofmerit ZT, have been demonstrated in recent literature. Specifically, density-of-states design in blends of 2 OSCs can be used to obtain electronic Seebeck coefficients up to ∼2000 µV/K. Alternatively, blending with (high-dielectric constant) insulating polymers can improve doping efficiency and thereby conductivity, as well as induce more favorable morphologies that improve conductivity while hardly affecting thermopower. In the PEDOT:PSS blend system, processing schemes to either improve conductivity via morphology or via (partial) removal of the electronically isolating PSS, or both, have been demonstrated. Although a range of experiments have at least quasi-quantitatively been explained by analytical or numerical models, a comprehensive model for organic thermoelectrics is lacking so far.Strategies to increase thermoelectric performance of doped organic semiconductors by blending are reviewed. Experimental results are, where possible, compared to analytical and numerical models. Several promising strategies to increase conductivity and/or thermopower are experimentally identified in recent literature. In contrast, formal understanding, especially of the role of morphology, is somewhat lagging behind.

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“…[1] While the major effort is to achieve TEGs based on inorganic materials (ZT e = 1.2 at 300 K for Bi 2 Te 3 alloys), [5] recent studies also include oxides, carbon-based compounds, [6,7] and electronically conducting organic polymers entirely based on atomic elements of high natural abundance (ZT e = 0.2-0.4 at 300 K for poly (3, 4-ethylenedioxythiophene) (PEDOT)). [8][9][10] This opens up for mass production of thermoelectric modules using high-volume printing and extrusion technologies. [8] We now move from electronic to ionic electronic thermoelectric materials.…”

mentioning

confidence: 99%

Ionic Thermoelectric Figure of Merit for Charging of Supercapacitors

Wang

Zhao

Khan

et al. 2017

Adv Elect Materials

166

191

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a fair comparison between electronic and ionic thermoelectric devices.The electronic Seebeck coefficient α e of a material is defined as the ratio between the open circuit potential V oc and the temperature difference ΔT (compensated for the Seebeck coefficient of the metal contacts). If electrons and holes thermodiffuse toward the colder side at identical rate no thermovoltage is generated. Hence, a nonnegligible Seebeck coefficient is obtained for materials with different conductivities for electrons and holes. This is illustrated for a material displaying majority hole (h + ) conduction in Figure 1a,b. The electronic Seebeck effect provides the basic principle of operation for thermoelectric generators (TEGs), which can provide a continuous output current and power ( Figure 1c). The efficiency of the heat-to-electricity conversion is directly related to ZT e 1+ , where ZT e is the dimensionless thermoelectric figure of merit, as introduced by A. F. Ioffe already in 1949. [4] ZT T e e e ( / 2 σ α λ = ) is defined by three fundamental properties of the thermoelectric material: the electrical conductivity σ e , the Seebeck coefficient α e , and the thermal conductivity λ. Today, there is an intense strive to optimize the interplay between those three properties and to maximize ZT e . [1] While the major effort is to achieve TEGs based on inorganic materials (ZT e = 1.2 at 300 K for Bi 2 Te 3 alloys), [5] recent studies also include oxides, carbon-based compounds, [6,7] and electronically conducting organic polymers entirely based on atomic elements of high natural abundance (ZT e = 0.2-0.4 at 300 K for poly(3, 4-ethylenedioxythiophene) (PEDOT)). [8][9][10] This opens up for mass production of thermoelectric modules using high-volume printing and extrusion technologies. [8] We now move from electronic to ionic electronic thermoelectric materials. Figure 1d shows an example of an ionic conductor (that is not electrochemically active, thus excluding any contribution from thermogalvanic effects) [11] that favors the transport of cations over anions when exposed to a thermal gradient. The Soret effect induces ionic concentration differences that generate a thermovoltage. The ionic Seebeck voltage α i of the ionic conductor is measured as the open circuit voltage V oc established between the two metal electrodes exposed to different temperatures (assuming a negligible Seebeck coefficient of the metal contacts). [12] The ionic thermoelectric effect occurs Thermoelectric materials enable conversion of heat to electrical energy. The performance of electronic thermoelectric materials is typically evaluated using a figure of merit ZT = σα2T/λ, where σ is the conductivity, α is the so-called Seebeck coefficient, and λ is the thermal conductivity. However, it has been unclear how to best evaluate the performance of ionic thermoelectric materials, like ionic solids and electrolytes. These systems cannot be directly used in a traditional thermoelectric generator, because they are based on ions that cannot pass the interface bet...

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Size Dependence of Electrical Conductivity and Thermoelectric Enhancements in Spin‐Coated PEDOT:PSS Single and Multiple Layers

Cited by 44 publications

References 54 publications

Complete Thermoelectric Characterization of PEDOT:PSS Thin Films with a Novel ZT Test Chip Platform

Complete Thermoelectric Characterization of PEDOT:PSS Thin Films with a Novel ZT Test Chip Platform

Conjugated Polymer Blends for Organic Thermoelectrics

Ionic Thermoelectric Figure of Merit for Charging of Supercapacitors

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