Nanoscale control by chemically vapour-deposited polymers

Gleason, Karen K.

doi:10.1038/s42254-020-0192-6

Cited by 63 publications

(105 citation statements)

References 178 publications

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“…Achieving conformal PEDOT coatings by the oCVD method has two significant advantages for electrochemical applications compared to the PEDOT:PSS solution‐applied process: i) maintaining a high surface area for effective contact with the electrolyte, and ii) enabling changes in polymer thickness upon ion exchange without the development of significant mechanical strain by leaving the void space open throughout the mesh electrode thickness. [ 34 ] In addition, due to its unique doping process, the oCVD PEDOT has a significant advantage in electrochemical applications over its PEDOT:PSS counterpart. The small anion dopant, here chloride (Cl ‐ ), makes oCVD PEDOT films compositionally distinct from spun‐cast PEDOT:PSS.…”

Section: Figurementioning

confidence: 99%

Ultrathin Conformal oCVD PEDOT Coatings on Carbon Electrodes Enable Improved Performance of Redox Flow Batteries

Gharahcheshmeh

Wan

Gandomi

et al. 2020

Adv Materials Inter

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broad adoption, motivating research into optimizing reactor design, electrolyte formulations, and separation strategies. The porous carbon electrode is a critical component of the RFB stack, providing active sites for redox reactions, controlling electrolyte distribution and pressure drop, and cushioning compressive forces required to seal the system and minimize contact resistances. [6] While functional, the electrodes used in advanced RFBs, which are typically based on porous carbon and graphite papers, cloths, or felts, generally possess low surface area (≈0.1-10 m 2 g −1), spatially varying surface chemistry, and poor aqueous wettability. [7] To address these limitations, electrodes are commonly oxidatively pretreated, via thermal, [8-11] electrochemical, [12] or chemical means, [13,14] which can simultaneously increase surface area and introduce oxygen-rich functional groups on the electrode surface that improve wetting and reaction kinetics. While effective, these methods offer limited control of specific surface chemistry and compositional uniformity across the 3D geometry. A potentially effective strategy for tailoring electrode-electrolyte interfaces is through the deposition of conductive polymeric overlayers, which have been shown to enhance the areal energy and power density in supercapacitors by improving pseudocapacitance, [15] and stabilize the structure and thermal stability of the electrode-electrolyte interface in lithium-ion batteries with nickel-rich positive electrodes. [16] These studies utilized continuous polymer layers, as thin as 3 nm, grown by oxidative chemical vapor deposition (oCVD) to support facile electrical and ionic conduction. In contrast to solution-applied layers, the oCVD films conformally encapsulated the nanostructured surfaces, leaving void space to enable changes in polymer layer thickness upon ion exchange without the development of significant mechanical strain. Additionally, conformal coverage maintains high surface area for effective contact with the electrolyte. Here, we explore the potential of oCVD processing to improve the performance of carbon fiber-based electrodes in Surface engineering of porous carbon electrodes is an effective strategy to enhance the power output of redox flow batteries (RFBs) and may enable new cost reduction pathways for energy storage. Here, a surface modification strategy that enhances the electrochemical performance of RFBs in iron-based electrolytes is demonstrated. Nanometric films of poly-(3,4-ethylenedioxythiophene) (PEDOT) are grown conformally onto carbon cloth electrodes using oxidative chemical vapor deposition (oCVD) and the impact of film properties on electrode performance in model iron-based electrolytes is investigated. Depositing oCVD PEDOT films on the electrode surface is found to reduce ohmic, kinetic, and mass transport resistances, with the highest current densities and lowest resistances observed for electrodes coated with a ≈78 nm thick film. As compared to unmodified electrodes, coated electrodes enhance the maxim...

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Section: Figurementioning

confidence: 99%

Ultrathin Conformal oCVD PEDOT Coatings on Carbon Electrodes Enable Improved Performance of Redox Flow Batteries

Gharahcheshmeh

Wan

Gandomi

et al. 2020

Adv Materials Inter

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“…Conjugated polymers hold exceptional promises in a variety of technological applications, including optoelectronics, energy storage, wearable electronics, and biomedical devices. [1,2] Poly(3,4-ethylenedioxythiophene) (PEDOT) has emerged as one of the most researched and promising conjugated polymers for organic electronics. [1][2][3][4][5] The combination of its optical transparency with electrical conductivity (σ), makes PEDOT a mechanically flexible alternative to transparent conductive oxides (TCOs).…”

Section: Introductionmentioning

confidence: 99%

“…[7] The presence of highly face-on texture (Figure 1b) lowers the barrier to intercrystallite charge transport and hence enhances in-plane conductivity. [1,6,7,29] The formation of highly face-on texture may be favored by chain reorientation at deposition temperatures above the glass transition (T g ) for PEDOT (≈100 °C). [1,7] As shown schematically in Figure 1b, a mixture of face-on and edge-on orientation deteriorates the percolation pathway for charge transport, hence lowering σ.…”

Section: Introductionmentioning

confidence: 99%

Optimizing the Optoelectronic Properties of Face‐On Oriented Poly(3,4‐Ethylenedioxythiophene) via Water‐Assisted Oxidative Chemical Vapor Deposition

Gharahcheshmeh

Robinson

Gleason

et al. 2020

Adv Funct Materials

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Engineering the texture and nanostructure to improve the electrical conductivity of semicrystalline conjugated polymers must address the rate-limiting step for charge carrier transport. In highly face-on orientation, the charge transport between chains within a crystallite becomes rate-limiting, which is highly sensitive to the π-π stacking distance and interchain charge transfer integral. Here, face-on oriented semicrystalline poly(3,4-ethylenedioxythiophene) (PEDOT) thin films are grown via water-assisted (W-A) oxidative chemical vapor deposition (oCVD). Combining W-A with the volatile oxidant, antimony pentachloride, yields an optimized electrical conductivity of 7520 ± 240 S cm −1 , a record for PEDOT thin films. Systematic control of π-π stacking distance from 3.50 Å down to 3.43 Å yields an electrical conductivity enhancement of ≈1140%. The highest electrical conductivity also corresponds to minimum in Urbach energy of 205 meV, indicating superior morphological order. The figure of merit for transparent conductors, σ dc /σ op , reaches a maximum value of 94, which is 1.9× and 6.7× higher than oCVD PEDOT grown without W-A and utilizing vanadium oxytrichloride and iron chloride oxidizing agents, respectively. The W-A oCVD is single-step all-dry process and provides conformal coverage, allowing direct growth on mechanical flexible, rough, and structured surfaces without the need for complex and costly transfer steps.

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“…In particular, oCVD PEDOT is a promising organic material for electronic applications in hybrid devices with conductivities up to 6260 S cm −1 (ref. 12 ), large tunable work functions around 5.1–5.4 eV 13 and good transparency in the visible spectral range 14 – 16 .…”

Section: Introductionmentioning

confidence: 99%

Toward three-dimensional hybrid inorganic/organic optoelectronics based on GaN/oCVD-PEDOT structures

et al. 2020

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The combination of inorganic semiconductors with organic thin films promises new strategies for the realization of complex hybrid optoelectronic devices. Oxidative chemical vapor deposition (oCVD) of conductive polymers offers a flexible and scalable path towards high-quality three-dimensional inorganic/organic optoelectronic structures. Here, hole-conductive poly(3,4-ethylenedioxythiophene) (PEDOT) grown by oxidative chemical vapor deposition is used to fabricate transparent and conformal wrap-around p-type contacts on three-dimensional microLEDs with large aspect ratios, a yet unsolved challenge in three-dimensional gallium nitride technology. The electrical characteristics of two-dimensional reference structures confirm the quasi-metallic state of the polymer, show high rectification ratios, and exhibit excellent thermal and temporal stability. We analyze the electroluminescence from a three-dimensional hybrid microrod/polymer LED array and demonstrate its improved optical properties compared with a purely inorganic microrod LED. The findings highlight a way towards the fabrication of hybrid three-dimensional optoelectronics on the sub-micron scale.

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Nanoscale control by chemically vapour-deposited polymers

Abstract: The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. CitationGleason, Karen K. "Nanoscale control by chemically vapourdeposited polymers." Nature Reviews Physics 2, 7 (June 2020

Cited by 63 publications

References 178 publications

Ultrathin Conformal oCVD PEDOT Coatings on Carbon Electrodes Enable Improved Performance of Redox Flow Batteries

Ultrathin Conformal oCVD PEDOT Coatings on Carbon Electrodes Enable Improved Performance of Redox Flow Batteries

Optimizing the Optoelectronic Properties of Face‐On Oriented Poly(3,4‐Ethylenedioxythiophene) via Water‐Assisted Oxidative Chemical Vapor Deposition

Toward three-dimensional hybrid inorganic/organic optoelectronics based on GaN/oCVD-PEDOT structures

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