Conducting Polymer Thin Films Research Articles

Dopant Enhanced Conjugated Polymer Thin Film for Low-Power, Flexible and Wearable DMMP Sensor.

Conjugated polymer has the potential to be applied on flexible devices as an active layer, but further investigation is still hindered by poor conductivity and mechanical stability. Here, this work demonstrates a dopant-enhanced conductive polymer thin film and its application in dimethyl methylphosphonate (DMMP) sensor. Among five comparable polymers this work employs, poly(bisdodecylthioquaterthiophene) (PQTS12) achieves the highest doping efficiency after doped by FeCl3, with the conductivity increasing by about five orders of magnitude. The changes in Young's modulus are also considered to optimize the conductivity and flexibility of this thin film, and finally the decay of conductivity is only 9.2% after 3000 times of mechanical bending. This work applies this thin film as the active layer of the DMMP gas sensor, which could be operated under 1mV driving voltage and 28 nW power consumption, with a sustainable durability against bending and compression. In addition, this sensor is provided with alarm capability while exposed to the DMMP atmospheres at different hazard levels. This work expects that this general approach could offer solutions for the fabrication of low-power and flexible gas sensors, and provide guidance for next-generation wearable devices with broader applications.

The Enhanced Thermoforming Stability of ITO Transparent Electrode Film by Using the Conducting Polymer Thin-Film

The Enhanced Thermoforming Stability of ITO Transparent Electrode Film by Using the Conducting Polymer Thin-Film

A nuanced understanding of the doping of poly(3,4-ethylenedioxythiophene) with tosylate

The conducting polymer poly(3,4-ethylenedioxythiophene) (known as PEDOT) is routinely fabricated into doped thin films for investigation of its inherent properties as well as for a range of applications. Fabrication of PEDOT is often achieved via oxidative polymerisation, where the conducting polymer is polymerised and doped (oxidised) to yield a conductive polymer thin film. The oxidiser and the polymerisation temperature are two parameters that may influence the properties and performance of the resultant PEDOT thin film. In this study, the role of temperature for the chemical polymerisation of PEDOT using the oxidiser iron tosylate is investigated from a computational and experimental viewpoint. While computations of the doping energetics suggest increasing doping with increasing temperature, x-ray photoelectron spectroscopy of fabricated PEDOT thin films indicate doping is much more complicated. With the aid of computations of the spatial distribution functions for tosylate in PEDOT, experiments indicate that two different populations of tosylate anions exist in the PEDOT matrix. Their relative populations change as a function of the polymerisation temperature. Therefore, polymerisation temperature plays a critical role in tailoring the properties of PEDOT in pursuit of being fit-for-purpose for the desired application.

Controlling the electrocatalytic activities of conducting polymer thin films toward suitability as cost-effective counter electrodes of dye-sensitized solar cells

Role dopant anions and solvents in electropolymerized conducting polymers (CPs) on controlling the morphology of thin films and electrocatalytic activities to judge their suitability as low-cost counter electrodes (CE) of dye-sensitized solar cells ( DSSCs) was systematically investigated. Amongst various CPs such as polyaniline (PANI), polypyrrole (PPy), and PEDOT with sodium dodecyl sulfate (SDS) as a dopant, PEDOT was found to exhibit the best photovoltaic performance with a photoconversion efficiency (PCE) of 6.99 %. This was attributed to the best electrocatalytic activity due to the smallest ΔEp, most minor R1, and nano-morphology-assisted high surface area, as confirmed by CV, EIS, and FE-SEM investigations. Using PEDOT as CP, the nature of dopants such as SDS, TFSI, and ClO4 has also been found to control the electrocatalytic activities and the morphology of the fabricated thin films affecting overall photovoltaic performance DSSCs. Amongst the various CP-based CE fabricated using different dopants and solvents, PEDOT:TFSI thin films prepared in acetonitrile solvent and used as CE exhibited not only the best electrocatalytic activity as CE but also demonstrated the best photovoltaic performance with PCE of 7.0 %, which almost similar to that of DSSC utilizing Pt as CE with PCE of 7.1 %. Therefore, it was concluded that the nature of CP and dopant ions were vital factors in governing the electrocatalytic activities of the thin films to ensure their suitability as CE for optimal functioning and controlling the DSSC performance.

Improving vertical charge transport in organic Schottky diodes via interface engineering of large-area conducting polymer thin films fabricated on hydrophilic liquid surface of tunable surface energy

Molecular orientation and stacking genre proved to be one of the decisive factors for the performance of conducting polymer (CP) based electronic devices. In this context, harnessing the key advantages of the ribbon shaped “floating-film transfer method” (FTM) along with an interfacial engineering approach has been utilized for molecular rearrangement in polymer thin-films formed on the surface of a high surface energy hydrophilic liquid mixture. In this novel subphase modified floating-film transfer method (SM-FTM), dodecyl benzene sulfonic acid (DBSA) has been used to control the molecular backbone stacking proximate to the solution-liquid interface and regioregular-poly(3-hexylthiophen-2,5-diyl) (rr-P3HT) was used as the model CP to probe the polymer-DBSA interaction. The molecular arrangements in microcrystalline domains, electronic band structures, and the evolution of surface texture at the solution-liquid interface have been investigated through multiple characterization tools. After that, the electrical performances of Schottky barrier diodes (SBDs) were studied in an ITO/P3HT/AlOx/Al sandwiched structure and a dramatic enhancement of rectification ratio up to 8.2 × 106 at ± 6 V was achieved. Further, an analytical model for SM-FTM, developed using lubrication theory and thin-film dynamics, has also been presented to elucidate the polymer spreading dynamics and the mechanism of molecular rearrangement at the interface.

A Review on Application of Poly(3,4-ethylenedioxythiophene) (PEDOT) in Rechargeable Batteries

Since the very first patent on poly(3,4-ethylenedioxythiophene) (PEDOT) that was filed in 1988, this polymer has been widely utilized and has achieved great success owing to its high electrical conductivity and excellent stability. The application of the conducting polymer, PEDOT, in renewable energy devices, especially rechargeable batteries, is attracting increasing attention due to its potential to solve the energy and climate crisis. In this review, we summarize the research over the past few decades directed toward the application of PEDOT in rechargeable batteries aimed at improving their electrochemical performance. We focus on PEDOT synthesized via oxidative chemical vapor deposition (oCVD), a relatively new process known for its ability to grow conducting polymer thin films with uniform, pinhole-free properties, and controllable thickness and conformality. For a comparison purpose, PEDOT synthesized via solution-based methods is also briefly summarized. Finally, future research directions for applying oCVD PEDOT in rechargeable batteries are discussed.IntroductionPEDOT Synthesis MethodsApplication of oCVD PEDOT in Rechargeable BatteriesApplications of Solution-Based PEDOT in Rechargeable BatteriesConclusions and Outlook

Recent Developments and Implementations of Conductive Polymer-Based Flexible Devices in Sensing Applications.

Flexible sensing devices have attracted significant attention for various applications, such as medical devices, environmental monitoring, and healthcare. Numerous materials have been used to fabricate flexible sensing devices and improve their sensing performance in terms of their electrical and mechanical properties. Among the studied materials, conductive polymers are promising candidates for next-generation flexible, stretchable, and wearable electronic devices because of their outstanding characteristics, such as flexibility, light weight, and non-toxicity. Understanding the interesting properties of conductive polymers and the solution-based deposition processes and patterning technologies used for conductive polymer device fabrication is necessary to develop appropriate and highly effective flexible sensors. The present review provides scientific evidence for promising strategies for fabricating conductive polymer-based flexible sensors. Specifically, the outstanding nature of the structures, conductivity, and synthesis methods of some of the main conductive polymers are discussed. Furthermore, conventional and innovative technologies for preparing conductive polymer thin films in flexible sensors are identified and evaluated, as are the potential applications of these sensors in environmental and human health monitoring.

Precursor Customized Assembly of Wafer-Scale Polymerized Aniline Thin Films for Ultrasensitive NH3 Detection.

2D conducting polymer thin film recently has garnered numerous interests as a means of combining the molecular aggregate ordering and promoting in-plane charge transport for large-scale/flexible organic electronics. However, it remains far from satisfactory for conducting polymer chains to achieve desirable surface topography and crystallinity due to lack of control over the precursor-involved interfacial assembly. Herein, wafer-size polyaniline (PANI) and tetra-aniline thin films are developed via a controlled interfacial synthesis with customized surface morphology and crystallinity through two typical aniline precursors selective polymerization. Two crucial competing assembly mechanisms, a) direct interfacial polymerization, b) solution polymerization and subsequent interfacial assembly, are investigated to play a vital role in determining elemental chain length and aggregate architecture. The optimal PANI thin film manifests ultraflat surface topography and unambiguous crystalline domains, which also enabling fascinating ammonia sensing capability with 31.4% ppm-1 sensitivity, fast response time (88s) with astonishing selectivity, repeatability, and recovery capability. The thus-demonstrated strategy with wafer-scale processing potential and flexible microdevice offers a promising route for large-scale manufacturing thin-film organic electronics.

Improving Vertical Charge Transport in Organic Schottky Diodes Via Interface Engineering of Large-Area Conducting Polymer Thin Films Fabricated on Hydrophilic Liquid Surface of Tunable Surface Energy

Improving Vertical Charge Transport in Organic Schottky Diodes Via Interface Engineering of Large-Area Conducting Polymer Thin Films Fabricated on Hydrophilic Liquid Surface of Tunable Surface Energy

Interfacial synthesis of crystalline quasi-two-dimensional polyaniline thin films for high-performance flexible on-chip micro-supercapacitors

Quasi-two-dimensional (q2D) conducting polymer thin film synergizes the advantageous features of long-range molecular ordering and high intrinsic conductivity, which are promising for flexible thin film-based micro-supercapacitors (MSCs). Herein, we present the high-performance flexible MSCs based on highly ordered quasi-two-dimensional polyaniline (q2D-PANI) thin film using surfactant monolayer assisted interfacial synthesis (SMAIS). Owing to high electrical conductivity, rich redox chemistry, and thin-film morphology, the q2D-PANI MSCs show high volumetric specific capacitance (ca. 360 F/cm3) and energy density (17.9 mWh/cm3), which outperform the state-of-art PANI thin-film based MSCs and promise for future flexible electronics.

Development of the Structural, Optical, and Electrical Properties of PEDOT:PSS Conducting Polymer Thin Film for Energy Applications

We report on a development of the structural, optical and electrical properties of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) conducting polymer thin films. The PEDOT:PSS thin films were deposited by a controlled thin film applicator and their physical properties were found to be effectively modified by isopropanol. The deposited films were investigated by several techniques including XRD, UV–Vis, SPM and Hall-effect. Interestingly, by optimizing the PEDOTS:PSS/ISO volume ratio (v:v), we find that the film charge carriers type can be switched from p to n-type with a high bulk carriers concentration reaching 6×1017 cm-3. Moreover, the film surface roughness becomes smoother and reaching a small value of only 1.9 nm. Such development of the PEDOT:PSS film properties makes it very promising to act as an electron transport layer for different energy applications.

Measurement of Ionic and Electronic Conductivities of Conductive Polymers in Battery Electrolyte to Guide Binder Development

Conductive polymers are being studied increasingly as additives into lithium battery electrodes, supercapacitors and other electrochemical devices due to their ability to conduct electrons and ions and serve as binders.1 Accurately measuring the large changes of ionic and electronic conductivities in a relevant electrolyte as a function of electrochemical doping has been a challenge thus far. We have developed a methodology for such measurements that combines the use of impedance spectroscopy on interdigitated electrodes conducted in two separate electrode geometries.2 We demonstrate the wide applicability of this methodology for the measurement of conductivity of p-type and n-type conducting polymer thin films as a function of electrochemical doping in relevant battery electrolytes. Such measurements have aided the screening and selection of various p-doped polymers for lithium ion battery cathodes as well as n-doped polymers for lithium-ion battery anodes and sulfur cathodes.3 References J. Lopez, D. G. Mackanic, Y. Cui, and Z. Bao, Nat. Rev. Mater., 4, 312 (2019). B. Zayat, P. Das, B. C. Thompson, and S. R. Narayan, J. Phys. Chem. C, 125, 7533 (2021). P. Das, B. Zayat, Q. Wei, C. Z. Salamat, I.-B. Magdău, R. Elizalde-Segovia, D. Rawlings, D. Lee, G. Pace, A. Irshad, L. Ye, A. Schmitt, R. A. Segalman, T. F. Miller, S. H. Tolbert, B. S. Dunn, S. R. Narayan, and B. C. Thompson, Chem. Mater., 32, 9176 (2020).

Promoting Bandlike Transport in Well-Defined and Highly Conducting Polymer Thin Films upon Controlling Dopant Oxidation Levels and Polaron Effects

To close the technological gap between laboratory-based conducting polymers and commercially available inorganic semiconductors, it is imperative to develop synthesis approaches that allow for the ...

Conducting polymer thin film for optoelectronic devices applications

A crystalline and conjugated semiconductor thin film of poly(o‐phenylene diamine‐co‐m‐phenylene diamine) copolymer [PoPmP]TFwith a thickness of 150 ± 3 nm is fabricated by physical vapor deposition technique (PVD). The copolymer is produced in an acidic solution using oxidative polymerization method. The ratio between the monomers and initiator is 1:1:2. The characterization of the obtained copolymer powder is carried out using different techniques includes Fourier‐transform infrared spectroscopy (FTIR), UV–Vis spectroscopy (UV–Vis), proton nuclear magnetic resonance (1HNMR), X‐ray diffraction analysis (XRD), and scanning electron microscopy (SEM). The structure and optical properties of the thin film were measured experimentally and computationally using DFT simulation. The obtained DFT data provide good proof for the electronic transition in zero‐dimensional [PoPmP] as a single crystal molecule. The obtained thin film presented encouraging outcomes to be a worthy applicant for polymer solar cell uses. This study provides valuable information on the nature and sources of defect formation and electronic transition in conducting doped copolymer which open the way for the application as an optoelectronic device.

Crystallization and Stability of Flexible P-Type Semiconductors and Their Thin Film Transistor Application

In recent years, electronic devices that require superior mechanical flexibility have been extremely sought for potential applications in next-generation displays, sensors, bio-implantable and disposable medical devices. Polymeric materials, of which the flexibility far exceeds that of conventional brittle inorganic counterparts, are widely considered for various flexible devices due to their excellent stretchable, foldable and bendable characteristics.Oxidative chemical vapor deposition (oCVD) is an emerging technique that provides not only a capability to process mechanically flexible polymeric films but also strategies to address current challenges claimed in typical solution-based polymer processing1-2. The oCVD technique allows for greater uniformity, excellent conformality, enhanced performance (e.g., conductivity) and an ability of large area polymer processing that are limited in conventional solution-processed polymers3-4.Crystallization and air stability of organic materials have been issues that have to be mitigated to warrant high performance and sustainable device applications. The oCVD technique, in addition to the advantages described above, could also address the issues of crystallization and air stability to enhance the carrier transport and overall conductivity, and to secure sustainability. We recently found that an in-situ oCVD capability of substrate heating during depositions resulted in an substantial increase in ordered structures in conjugated polymers, leading to enhanced crystallization of the resulting oCVD polymers5. Consequently, the enhancement of the carrier transport and conductivity was obtained due to the increase in favorable conduction paths in the crystalline phase. Further, the vapor phase processing of oCVD may be of crucial relevance to achieve air stability since oCVD does not require any monomer solubility in specific solvents and, therefore, is able to polymerize insoluble materials6 that are not available for conventional solution processing techniques such as spin-coating or dip-casting. The reactivity of insoluble monomers is quite limited due to their rigid backbone structures; however, this limited reactivity is the key to achieve air stability since the reactions between insoluble materials and water (H2O)/oxygen, which are the main origins to cause instabilities of organic materials in air, are significantly prohibited.In this presentation, we report our recent findings of enhanced crystallization and air-stability of oCVD polymers. Particularly, the structure, chemical and electrical properties of two oCVD polymers, poly(3,4-ethylenedioxythiophene) (i.e., PEDOT) and unsubstituted polythiophene, will be compared with focuses on the crystalline state, dope-ability and air-stability. Further, thin film transistors (TFTs) that employ the two oCVD polymers as TFT channel are presented and the device performance of output and transfer characteristics will be compared with focuses on the carrier mobility and on/off switching properties. Acknowledgement: This work was supported by Purdue University and partly by an NSF grant, Award No. ECCS-193108. References Lock, J. P.; Im, S. G.; Gleason, K. K., Oxidative chemical vapor deposition of electrically conducting poly(3,4-ethylenedioxythiophene) films. Macromolecules 2006, 39 (16), 5326-5329.Im, S. G.; Gleason, K. K., Systematic control of the electrical conductivity of poly(3,4-ethylenedioxythiophene) via oxidative chemical vapor deposition. Macromolecules 2007, 40 (18), 6552-6556.Coclite, A. M.; Howden, R. M.; Borrelli, D. C.; Petruczok, C. D.; Yang, R.; Yaguee, J. L.; Ugur, A.; Chen, N.; Lee, S.; Jo, W. J.; Liu, A.; Wang, X.; Gleason, K. K., 25th Anniversary Article: CVD Polymers: A New Paradigm for Surface Modification and Device Fabrication. Adv. Mater. 2013, 25 (38), 5392-5422.Kovacik, P.; Hierro, G. d.; Livernois, W.; Gleason, K. K., Scale-up of oCVD: large-area conductive polymer thin films for next-generation electronics. Materials Horizons 2015, 2 (2), 221-227.Wang, X.; Zhang, X.; Sun, L.; Lee, D.; Lee, S.; Wang, M.; Zhao, J.; Shao-Horn, Y.; Dincă, M.; Palacios, T.; Gleason, K. K., High electrical conductivity and carrier mobility in oCVD PEDOT thin films by engineered crystallization and acid treatment. Science Advances 2018, 4 (9), eaat5780.Borrelli, D. C.; Lee, S.; Gleason, K. K., Optoelectronic properties of polythiophene thin films and organic TFTs fabricated by oxidative chemical vapor deposition. Journal of Materials Chemistry C 2014, 2 (35), 7223-7231. Figure 1

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

AbstractSolution‐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.

Integration of PEGylated Polyaniline Nanocoatings with Multiple Plastic Substrates Generates Comparable Antifouling Performance.

Conducting polymer nanocoatings render plastics to possess interesting optical, chemical, and electrical properties. It nevertheless remains technically challenging to deposit uniform conducting polymer nanocoatings on ambient plastic substrates ascribed to the inert and varied chemical properties of plastics and the notorious processability of conducting polymers. Previous studies have made progress in delivering various conducting polymer thin films via oxidative chemical vapor deposition. Herein, we develop a solution-based approach to polyaniline (PANI) and PEGylated PANI nanocoatings on multiple engineering plastics followed by evaluating their antifouling performance. The procedure relies on the formation of uniform, lyotropic V2O5·nH2O thin films on plastics assisted by a surfactant-sodium N-lauroylsarcosinate. Next, in situ, oxidative polymerization causes the formation of nanofibrous PANI nanocoatings. Finally, interfacial functionalization leads to PEGylated PANI nanocoatings, and the steric nanolayer effectively repels the adsorption of bovine serum albumin and the attachment of the bacterium Pseudoalteromonas sp. on the surface. It is worth noting that the antifouling properties rely mainly on the presence of PEGylated PANI nanocoatings, irrespective of the type of plastic substrates underneath. The current study therefore opens an avenue for the solution-based delivery of conducting polymer-based, functional nanocoatings on hydrophobic substrates in a controllable manner with the availability of further modification.

An Insight into Ionic Conductivity of Polyaniline Thin Films.

The work addresses an issue of the conductivity phenomenon in conductive polymer thin films. Polyaniline was chosen as a broadly used and thoroughly investigated conductive polymer in order to test and show capabilities of the developed original approach based on impedance spectra analysis. A number of films of different thickness were deposited onto a Pt electrode surface and consequently investigated in aqueous solution containing perchloric acid as an electrolyte. The processes that occur in polyaniline film were studied by cyclic voltammetry, electrochemical quartz crystal microgravimetry (EQCM) and electrochemical impedance spectroscopy (EIS). The role of incorporated ions as charge carriers was investigated with respect to the control of the conductivity properties of the film. Along with detailed polyaniline behavior study, the work makes up a fundamental scientific impact on theoretical electrochemistry and electroanalytical techniques.

Conductive Metal-Organic Framework Thin Film Hybrids by Electropolymerization of Monosubstituted Acetylenes.

1-Hexyne monomers were potentiostatically electropolymerized upon confinement in 1D channels of a surface-mounted metal-organic framework Cu(BDC) (SURMOF-2). A layer-by-layer deposition method allowed for SURMOF depostition on substrates with prepatterned electrodes, making it possible to characterize electrical conductivity in situ, i.e., without having to delaminate the conductive polymer thin film. Successful polymerization was evidenced by mass spectroscopy, and the electrical measurements demonstrated an increase of the electrical conductivity of the MOF material by 8 orders of magnitude. Extensive DFT calculations revealed that the final conductivity is limited by electron hopping between the conductive oligomers.

Thin film formation of PEDOT conductive polymer and PVDF piezoelectric polymer by dip‐coating method assuming application to flexible power generation element

AbstractPoly(3,4‐ethylenedioxythiophene) (PEDOT) conductive polymer and polyvinylidene difluoride (PVDF) piezoelectric polymer thin films were formed by dip‐coating method. The relationship between drawing speed and film thickness was experimentally investigated. Dip‐coated PEDOT and PVDF thin films were characterized and confirmed that both had surely worked as electrode and piezoelectric film of a flexible power generation element, respectively. Using dip‐coating method, these thin films were successfully formed on 3D surface of a bellows shaped spring made of silicone rubber.