<i>In Situ</i> Observation of Morphological and Oxidation Level Degradation Processes within Ionic Liquid Post-treated PEDOT:PSS Thin Films upon Operation at High Temperatures

Oechsle, Anna Lena; Heger, Julian E.; Li, Nian; Yin, Shanshan; Bernstorff, Sigrid; Müller‐Buschbaum, Peter

doi:10.1021/acsami.2c05745

Cited by 21 publications

(29 citation statements)

References 68 publications

(112 reference statements)

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“…In both EG/GOPS-PEDOT:PSS and pg2T-TT, the differences in GISAXS patterns across conditions indicate small morphological changes relative to the mesoscale changes that occur in related conjugated polymer systems during codeposition, 83 in response to changes in humidity, 84 and in operation in thermoelectric 25 or photovoltaic devices. 85 In contrast to the subtle changes in small-angle scattering in EG/GOPS-PEDOT:PSS and pg2T-TT, crys-PEDOT:PSS showed much larger differences in small-angle scattering between ex situ conditions (Figures 5c and 6a−d).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Quantitative Composition and Mesoscale Ion Distribution in p-Type Organic Mixed Ionic-Electronic Conductors

Paulsen

et al. 2023

ACS Appl. Mater. Interfaces

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Understanding the ionic composition and distribution in organic mixed ionic-electronic conductors (OMIECs) is crucial for understanding their structure–property relationships. Despite this, direct measurements of OMIEC ionic composition and distribution are not common. In this work, we investigated the ionic composition and mesoscopic structure of three typical p-type OMIEC materials: an ethylene glycol-treated crosslinked OMIEC with a large excess fixed anionic charge (EG/GOPS-PEDOT:PSS), an acid-treated OMIEC with a tunable fixed anionic charge (crys-PEDOT:PSS), and a single-component OMIEC without any fixed anionic charge (pg2T-TT). A combination of X-ray fluorescence (XRF) and X-ray photoelectron spectroscopies, gravimetry, coulometry, and grazing incidence small-angle X-ray scattering (GISAXS) techniques was employed to characterize these OMIECs following electrolyte exposure and electrochemical cycling. In particular, XRF provided quantitative ion-to-monomer compositions for these OMIECs from passive ion uptake following aqueous electrolyte exposure and potential-driven ion uptake/expulsion following electrochemical doping and dedoping. Single-ion (cation) transport in EG/GOPS-PEDOT:PSS due to Donnan exclusion was directly confirmed, while significant fixed anion concentrations in crys-PEDOT:PSS doping and dedoping were shown to occur through mixed anion and cation transport. Controlling the fixed anionic (PSS–) charge density in crys-PEDOT:PSS mapped the strength of Donnan exclusion in OMIEC systems following a Donnan–Gibbs model. Anion transport dominated pg2T-TT doping and dedoping, but a surprising degree of anionic charge trapping (∼1020 cm–3) was observed. GISAXS revealed minimal ion segregation both between PEDOT- and PSS-rich domains in EG/GOPS-PEDOT:PSS and between amorphous and semicrystalline domains in pg2T-TT but showed significant ion segregation in crys-PEDOT:PSS at length scales of tens of nm, ascribed to inter-nanofibril void space. These results bring new clarity to the ionic composition and distribution of OMIECs which are crucial for accurately connecting the structure and properties of these materials.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Quantitative Composition and Mesoscale Ion Distribution in p-Type Organic Mixed Ionic-Electronic Conductors

Paulsen

et al. 2023

ACS Appl. Mater. Interfaces

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“…24 Small angle X-ray scattering with synchrotron sources enables the probing of mesoscale structure. Significant work has been carried out to understand OMIEC as-cast structure, revealing the effect of additives and processing conditions on meso-scale structure, 25,26 and meso-scale structure formation during film deposition. 27,28 While in situ work has been reported on the electrochemical potential meso-scale structure in Li + transporting block copolymers for battery applications, 29,30 there have been a noted absence of work reporting small angle scattering in other types of OMIECs exposed to application-relevant conditions in situ or ex situ.…”

Section: Introductionmentioning

confidence: 99%

Quantitative composition and mesoscale ion distribution in p-type organic mixed ionic-electronic conductors

Wu¹,

Paulsen²,

Qian³

et al. 2023

Preprint

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Understanding the ionic composition and distribution in organic mixed ionic-electronic conductors (OMIECs) is crucial for understanding their structure-property relationships. However, direct measurement of OMIEC ionic composition and distribution is not common. In this work, we investigate the ionic composition and mesoscopic structure of three typical p-type OMIEC materials: an ethylene glycol treated crosslinked OMIEC with large excess fixed anionic charge (EG/GOPS-PEDOT:PSS), an acid treated OMIEC with tunable fixed anionic charge (crys-PEDOT:PSS), and a single component OMIEC absent any fixed anionic charge (pg2T-TT). A combination of X-ray fluorescence (XRF) and photoelectron spectroscopies (XPS), gravimetry, coulometry, and grazing incidence small angle X-ray scattering (GISAXS) techniques were employed to characterize these OMIECs following electrolyte exposure and electrochemical cycling. In particular, XRF provided quantitative ion-to-monomer compositions for these OMIECs from passive ion uptake following aqueous electrolyte exposure, and potential driven ion uptake/expulsion following electrochemical doping and dedoping. Single ion (cation) transport in EG/GOPS-PEDOT:PSS due to Donnan exclusion was directly confirmed, while despite significant fixed anion concentration in crys-PEDOT:PSS doping and dedoping was shown to occur through mixed anion and cation transport. Controlling the fixed anionic (PSS-) charge density in crys-PEDOT:PSS mapped the strength of Donnan exclusion in OMIEC systems following a Donnan-Gibbs model. Anion transport dominated pg2T-TT doping and dedoping, but a surprising degree of anionic charge trapping (~1020 cm-3) was observed. GISAXS revealed minimal ion segregation both between PEDOT- and PSS-rich domains in EG/GOPS-PEDOT:PSS, and between amorphous and semicrystalline domains in pg2T-TT, but showed significant ion segregation in crys-PEDOT:PSS at length scales of tens of nm, ascribed to inter-nanofibril void space. These results bring new clarity to the ionic composition and distribution of OMIECs that are crucial for accurately connecting structure and properties in these materials.

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“…The modeling is done in the framework of the distorted‐wave Born approximation (DWBA) and the effective interface approximation (EIA). [ 46 ] With the experimental resolution of the in situ GISAXS experiment, domain sizes in the range of one to hundreds of nanometers are covered, which is well‐suitable for understanding OSC active layers.…”

Section: Resultsmentioning

confidence: 99%

Film Formation Kinetics of Polymer Donor and Nonfullerene Acceptor Active Layers During Printing Out of 1,2,4‐Trimethylbenzene in Ambient Conditions

et al. 2023

Self Cite

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Slot‐die coating is a promising upscaling fabrication method to promote commercialization in the field of organic solar cells. Herein, the nonfullerene active layer blend of a conjugated polymer PffBT4T‐2OD and a small molecule acceptor EH‐IDTBR, which is printed out of the nonhalogenated solvent 1,2,4‐trimethylbenzene, is studied. The film formation kinetics of the active layer PffBT4T‐2OD:EH‐IDTBR is probed in terms of the temporal evolutions in morphology as well as molecular conformation and aggregation as revealed by in situ grazing‐incidence small angle X‐ray scattering and UV–vis spectroscopy during the film printing process. A five‐regime mesoscale domain growth process is observed in the active layer from the liquid state to the final dry state. The solvent evaporation‐induced domain growth is accompanied with molecular stacking in a distinct J‐type aggregation of the acceptor and a slight H‐type aggregation of the donor molecules. The printed active layers exhibit an edge‐on dominated PffBT4T‐2OD and a face‐on dominated EH‐IDTBR crystallite structure. Compared to the neat PffBT4T‐2OD and EH‐IDTBR films, in the active layer, the crystallite structure deviates slightly in lattice spacing.

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In Situ Observation of Morphological and Oxidation Level Degradation Processes within Ionic Liquid Post-treated PEDOT:PSS Thin Films upon Operation at High Temperatures

Cited by 21 publications

References 68 publications

Quantitative Composition and Mesoscale Ion Distribution in p-Type Organic Mixed Ionic-Electronic Conductors

Quantitative Composition and Mesoscale Ion Distribution in p-Type Organic Mixed Ionic-Electronic Conductors

Quantitative composition and mesoscale ion distribution in p-type organic mixed ionic-electronic conductors

Film Formation Kinetics of Polymer Donor and Nonfullerene Acceptor Active Layers During Printing Out of 1,2,4‐Trimethylbenzene in Ambient Conditions

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