Humidity control in a closed system utilizing conducting polymers

Wei, Qingshuo; Mukaida, Masakazu; Ding, Wuxiao; Ishida, Takao

doi:10.1039/c8ra01776j

Cited by 8 publications

(8 citation statements)

References 20 publications

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“…Based on the unit cell volume of PEDOT:PSS (containing four monomer units) of 2027 Å 3 , [ 53 ] and the fact that H 2 O molecules form hydrogen bonds with PSS, the volume fraction of residual water is estimated to be ≈1.7%, corresponding to 5.7 × 10 20 H 2 O molecules cm −3 , which agrees with previous reports. [ 21,48 ] This water density translates for our PEDOT:PSS film (1 cm 2 × 70 nm) into an uptake of 1.20 × 10 −7 cm 3 of water, which is indeed readily available in a standard glove box (0.1 ppm H 2 O and 1 m 3 box volume correspond to a water volume of ≈7 × 10 −5 cm 3 ).…”

Section: Resultsmentioning

confidence: 99%

“…At room temperature, as-prepared PEDOT:PSS films contain residual water, unless annealed in UHV, as discussed previously. [20,21,33] Water has a high dielectric constant of ≈78 at room temperature, [43] and thus its presence in PEDOT:PSS could increase the dielectric constant of the film, even if the water molecules are bound to the ions of the polymer and not in pure liquid phase. An increased ε leads to a lowering of Φ SD according to Equation (1), and thus of the sample work function, compared to a film without any residual water.…”

Section: Resultsmentioning

confidence: 99%

“…[6] Due to the hydrophilic nature of PSS, thin films of PEDOT:PSS readily absorb water from the surrounding environment, with several percent water uptake at normal air humidity levels. [20,21] The presence of water in PEDOT:PSS thin films can have adverse effects on device stability and reproducibility. For example, degradation in organic solar cells was reported to accelerate by the presence of PEDOT:PSS due to increased water diffusion through the device, leading to delamination of the metal electrodes, [22] or deterioration of other organic components.…”

Section: Introductionmentioning

confidence: 99%

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Conductive Polymer Work Function Changes due to Residual Water: Impact of Temperature‐Dependent Dielectric Constant

Mansour

Kim

Park

et al. 2020

Adv Elect Materials

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Tremendous progress has been made in improving the performance and functionality of organic electronic devices. To a significant extent, this was possible by tuning the optical properties, electronic energy levels, and, foremost, charge transport properties of conductive polymers, as these are mostly employed as electrical contact layers. It should be noted that most polymers used in this field are semiconductors, and become sufficiently conductive only upon doping. Among the wide range of available polymers, polythiophenes have attracted attention for their moderate conductivity, high transparency, and air stability, which has enabled their implementation in various electronic and optoelectronic devices. [5-7] Molecular doping of polythiophenes, in which a small amount of dopant is added to the host polymer, has proven to be a successful approach to increase the density of mobile charge carriers and thus conductivity above 1 S cm −1. [8-14] A key challenge to the successful application of molecularly doped polymers lies in their relatively poor thermal stability, which ultimately leads to dopant diffusion and desorption at elevated temperatures. [15-17] A conductive polymer from the thiophene family that presently dominates in device applications is p-doped poly(ethylenedioxythiophene) (PEDOT). The breakthrough of Solution-processed conducting polymer thin films are key components in organic and flexible electronic and optoelectronic devices. An archetypal conducting polymer is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), which can feature a high work function and thus helps achieving Ohmic contacts for holes with many semiconductors. However, it is known that residual water in PEDOT:PSS films lowers their work function and is detrimental for device lifetime. Our photoelectron spectroscopy experiments reveal that the work function of PEDOT:PSS films containing residual water shows the same trend as function of temperature as does the dielectric constant (ε) of water, in the range between 25 °C and-100 °C. Consistently, it is found from impedance spectroscopy measurements that ε of residual water containing PEDOT:PSS films increases with decreasing temperature. After removal of residual water from PEDOT:PSS films by annealing in ultrahigh vacuum, the work function of thin films is much higher than before (reaching 6.1 eV) and, notably, independent of temperature. In contrast, no indication is found that the presence of residual water has any impact on the electrical conductivity. For a nominally water-free molecularly doped conjugated donor/acceptor copolymer films, a correlation between sample work function and temperature similar to those seen for PEDOT:PSS is found.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Conductive Polymer Work Function Changes due to Residual Water: Impact of Temperature‐Dependent Dielectric Constant

Mansour

Kim

Park

et al. 2020

Adv Elect Materials

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“…13,14 Atmospheric humidity can vary considerably and uncontrollably over short periods of time but its effects are not easily mitigated due to the fact that the moving parts in most devices do not operate in a controlled atmosphere. 15,16 Water molecules can usually enter the lubricant through several sources including condensation and adsorption from a humid environment, leakage from heat exchangers or as a by-product of chemical reactions. 17,18 The effect of water on the properties of lubricants are often detrimental, 17,18 especially when preventing the adsorption of organic lubricant molecules at the relevant interfaces.…”

Section: Introductionmentioning

confidence: 99%

Impact of water on the lubricating properties of hexadecane at the nanoscale

Cafolla

Voïtchovsky

2020

Nanoscale

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“…PANI films have been reported to be effective in ammonia gas sensors, which is beneficial for food-packaging applications [70,71]. In a humidity sensor, films of CPs, such as poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT/PSS) and poly(anilinesulfonic acid) have been shown to be capable of detecting a change in a wide range of humidity [72,73].…”

Section: Biosensorsmentioning

confidence: 99%

Research Progress on Conducting Polymer-Based Biomedical Applications

2019

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Conducting polymers (CPs) have attracted significant attention in a variety of research fields, particularly in biomedical engineering, because of the ease in controlling their morphology, their high chemical and environmental stability, and their biocompatibility, as well as their unique optical and electrical properties. In particular, the electrical properties of CPs can be simply tuned over the full range from insulator to metal via a doping process, such as chemical, electrochemical, charge injection, and photo-doping. Over the past few decades, remarkable progress has been made in biomedical research including biosensors, tissue engineering, artificial muscles, and drug delivery, as CPs have been utilized as a key component in these fields. In this article, we review CPs from the perspective of biomedical engineering. Specifically, representative biomedical applications of CPs are briefly summarized: biosensors, tissue engineering, artificial muscles, and drug delivery. The motivation for use of and the main function of CPs in these fields above are discussed. Finally, we highlight the technical and scientific challenges regarding electrical conductivity, biodegradability, hydrophilicity, and the loading capacity of biomolecules that are faced by CPs for future work. This is followed by several strategies to overcome these drawbacks.

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Humidity control in a closed system utilizing conducting polymers

Abstract: In this study, we demonstrate that conducting polymers could be ideal materials for continuously managing humidity in a wide range of enclosed spaces.

Cited by 8 publications

References 20 publications

Conductive Polymer Work Function Changes due to Residual Water: Impact of Temperature‐Dependent Dielectric Constant

Conductive Polymer Work Function Changes due to Residual Water: Impact of Temperature‐Dependent Dielectric Constant

Impact of water on the lubricating properties of hexadecane at the nanoscale

Research Progress on Conducting Polymer-Based Biomedical Applications

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