Ionic Liquids as Post-Treatment Agents for Simultaneous Improvement of Seebeck Coefficient and Electrical Conductivity in PEDOT:PSS Films

Saxena, Nitin; Pretzl, Benjamin; Lamprecht, Xaver; Bießmann, Lorenz; Yang, Dan; Li, Nian; Bilko, Christoph; Bernstorff, Sigrid; Müller‐Buschbaum, Peter

doi:10.1021/acsami.8b21709

Cited by 73 publications

(87 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, Saxena et al treated PEDOT:PSS film with EMIM-DCA in THF solution. They observed the simultaneous improvement of σ and S, and a maximum PF of 170 µW/K 2 m had been obtained because of the binary nature of both ionic liquids and PEDOT:PSS (Saxena et al, 2019). Therefore, approaches that can only slightly lower the high σ of formamide-treated PEDOT:PSS films while significantly improve the S could be effective for improving the TE properties of PEDOT:PSS films.…”

Section: Introductionmentioning

confidence: 97%

Improved Thermoelectric Properties and Environmental Stability of Conducting PEDOT:PSS Films Post-treated With Imidazolium Ionic Liquids

et al. 2020

View full text Add to dashboard Cite

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most popular conducting polymers and widely used as polymer thermoelectric materials, and its thermoelectric performance could be improved by a variety of post-treatment processes. This paper reported two series of post-treatment methods to enhance the thermoelectric performance. The first series method included pre-treatment of PEDOT:PSS film with formamide, followed by imidazolium-based ionic liquids. The second series method included pre-treatment of PEDOT:PSS film with formamide, followed by sodium formaldehyde sulfoxylate, and finally imidazolium-based ionic liquids. Two series of post-treatment methods significantly improved the power factor of PEDOT:PSS when compared to that of PEDOT:PSS treated with formamide only. For example, using the first series post-treatment method with 40 vol.% ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide, the Seebeck coefficient of the PEDOT:PSS film increased from 14.9 to 28.5 µV/K although the electrical conductivity reduced from 2,873 to 1,701 S/cm, resulting in a substantial improvement in the overall power factor from 63.6 to 137.8 µW/K 2 m. The electrical conductivity enhancement in the formamide-treatment process was in part ascribed to the removal of the insulating PSS component. Further treatment of PEDOT:PSS film with ionic liquid caused dedoping of PEDOT and hence increased in Seebeck coefficient. In contrast, second series posttreatment method led to the reduction in electrical conductivity from 2,873 to 641 S/cm but a big improvement in the Seebeck coefficient from 14.9 to 61.1 µV/K and thus the overall power factor reached up to ∼239.2 µW/K 2 m. Apart from the improvement in electrical conductivity, the increase in Seebeck coefficient is on account of the substantial dedoping of PEDOT polymer to its neutral form and thus leads to the big improvement of its Seebeck coefficient. The environmental stability of ionic liquid-treated PEDOT:PSS films were examined. It was found that the ionic liquid treated PEDOT:PSS retained Yemata et al. Improved Thermoelectric Properties of PEDOT:PSS more than 70% Seebeck coefficient and electrical conductivity at 75% RH humidity and 70 • C for 480 h. The improved long-term TE stability is attributed to the strong ionic interaction between sulfonate anions and bulky imidazolium cations that effectively block the penetration of water and lessen the tendency to take up water from the air.

show abstract

Section: Introductionmentioning

confidence: 97%

Improved Thermoelectric Properties and Environmental Stability of Conducting PEDOT:PSS Films Post-treated With Imidazolium Ionic Liquids

et al. 2020

View full text Add to dashboard Cite

show abstract

“…post‐treated pristine PEDOT:PSS films with various ionic liquids to induce an increased π–π stacking between PEDOT molecules. [ 4 ] 1‐ethyl‐3‐methylimidazolium tetracyanoborate (EMIM TCB) treated films exhibited a record short π–π stacking distance of 3.35 Å due to an enormous bonding effect of TCB to PEDOT and EMIM to PSS and subsequent phase separation. Fan et al.…”

Section: Introductionmentioning

confidence: 99%

Role of the Processing Solvent on the Electrical Conductivity of PEDOT:PSS

Dong

Portale

2020

Adv Materials Inter

View full text Add to dashboard Cite

addition, solvent-thermal post-treatment, organic-inorganic blending, and even film stretching. [1] Different compounds like polar solvents, salt, strong acids, ionic liquids, carbon nanotube, e.g., were utilized as additives, post-treatment agents, or blending components. For example, Saxena et al. post-treated pristine PEDOT:PSS films with various ionic liquids to induce an increased π-π stacking between PEDOT molecules. [4] 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM TCB) treated films exhibited a record short π-π stacking distance of 3.35 Å due to an enormous bonding effect of TCB to PEDOT and EMIM to PSS and subsequent phase separation. Fan et al. reported an impressive electrical conductivity of 3088 S cm −1 after the exposure of PEDOT:PSS:5% DMSO (dimethyl sulfoxide) films with sulfuric acid. [3] Worfolk et al. reported solution sheared PEDOT:PSS films further posttreated with methanol with extremely high conductivity of 4600 S cm −1. [2] Among various strategies, polar solvents addition and post-treatment are among the most used and most efficient ways to improve PEDOT:PSS electrical conductivity. [1,5-8] Both processes can induce different effects on PEDOT:PSS thin films, such as π-π stacking distance shortening (i.e., increased π-π orbital overlap), alteration of the crystallite orientation (face-on vs edge-on), overall crystallinity increase, PSS removal, and phase separation. [9,10] Polar solvents with high dielectric constants and high boiling points are common additives and post-treatment agents, especially DMSO and EG (ethylene glycol). In 2002, Kim et al. reported for the first time about the use of DMSO as an additive to dramatically increased the conductivity of PEDOT:PSS thin films (about two orders of magnitude higher at room temperature), and since then polar solvents got more and more attention from the research field. [11,12] Pipe et al. reported a promising thermoelectric property for PEDOT:PSS by EG dip treatment following pre-doping PEDOT:PSS nanofilms with DMSO or EG. [13] The DMSO and EG pre-doped films exhibited σ > 600 S cm −1. After dipping them into an EG bath, conductivities up to 1000 S cm −1 were obtained, which were three orders of magnitude higher than pristine PEDOT:PSS. The effective improvement was mainly attributed to the selective removal of excessive PSS. Palumbiny et al. observed that the in-plane electrical conductivity of PEDOT:PSS increased from 0.2 to 1200 S cm −1 upon EG treatment. The authors drew the emphasis on the formation of larger PEDOT crystallites with more pronounced Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most studied conductive polymers, holding great potential in many applications such as thermoelectric generators, solar cells, and memristors. Great efforts have been invested in trying to improve its mechanical and electrical properties and to elucidate the structure-property relationship. In this work, a systematic and quantitative study of the effect of solvent polarity and solution processing on the f...

show abstract

“…77,78 A less amount of the PSS in the treated PEDOT:PSS film leads to less H 2 O uptake and then the film becomes more intact even in wet conditions. 68 Moreover, as demonstrated by XRD, the treated samples exhibited a much higher crystallinity than the untreated sample, hence enhancing the overall stability as reflected by the small reduction in the s and S. 37 On the other hand, strong electrostatic attraction between the negatively charged sulfonate anions and the positively charged bulky imidazolium cations may block the diffusion of H 2 O molecules from the film surface into the interior and consequently reduces the H 2 O uptake, partially contributing to the stability enhancement. In addition, neutralization happening between imidazolium derivatives with acidic PEDOT:PSS suspension additionally contributes to improvement in stability with a reasonable decline of the s, which is consistent with reported result.…”

Section: Stability Study Of Pedot:pss Filmsmentioning

confidence: 98%

“…35 In their recent work, they used ionic liquid to treat PEDOT:PSS films, and obtained an extremely high PF of 754 mW m À1 K À2 , 36 being much greater than that obtained by Saxena et al using a same ionic liquid (PF = 170 mW m À1 K À2 ). 37 Recently, we reported a series of work on post-treatment of PEDOT:PSS film using a combination of chemicals including a variety of reagents such as formamide, 8 formic acid, 38 trifluoroacetic acid, 19 trifluoromethanesulfonic acid, 24 hydrazine, 38 formaldehyde sulfoxylate 39 and ionic liquid. 40 For example, PEDOT:PSS films were post-treated with formamide and ionic liquids, and it was found that treatment only marginally had effect on the s but remarkably increased the S, achieving an overall PF up to B239.2 mW m À1 K À2 .…”

Section: Introductionmentioning

confidence: 99%

Binary treatment of PEDOT:PSS films with nitric acid and imidazolium-based ionic liquids to improve the thermoelectric properties

et al. 2020

View full text Add to dashboard Cite

show abstract

Ionic Liquids as Post-Treatment Agents for Simultaneous Improvement of Seebeck Coefficient and Electrical Conductivity in PEDOT:PSS Films

Cited by 73 publications

References 57 publications

Improved Thermoelectric Properties and Environmental Stability of Conducting PEDOT:PSS Films Post-treated With Imidazolium Ionic Liquids

Improved Thermoelectric Properties and Environmental Stability of Conducting PEDOT:PSS Films Post-treated With Imidazolium Ionic Liquids

Role of the Processing Solvent on the Electrical Conductivity of PEDOT:PSS

Binary treatment of PEDOT:PSS films with nitric acid and imidazolium-based ionic liquids to improve the thermoelectric properties

Contact Info

Product

Resources

About