High-performance PEDOT Research Articles

Continuous fabrication of flexible, high-performance PEDOT: PSS thermoelectric fiber without post-processing

Organic thermoelectric fibers (OTEFs) are popular in wearable self-powered technology due to easy weaving and power generation. However, limitations include poor spinning capability, weak mechanical strength, low output power, and dangerous post-treatment. Here, we report the rapid preparation of flexible, high-performance OTEFs without post-treatment through introducing ionic liquid (IL) of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMIM: TFSI) into the Poly (3,4-ethylene dioxythiophene): Poly (styrene sulfonate) (PEDOT: PSS) to enhance thermoelectric properties, and mechanical strength, with just 1 wt% of IL enabling continuous fabrication of the PEDOT: PSS fiber. The resulting fiber exhibits remarkable electrical, and thermoelectric performance of ∼2267.7 S cm−1, and ∼85 μW m−1 K−2, respectively. It also demonstrates excellent strength (∼289.72 MPa), with a resistance change of less than 8 % after 10,000 bending cycles. The fabricated five-legs devices achieve an impressive output power and output power density of ∼7.84 nW and ∼4.32 μW cm−2 at 49 K, and the fabric textile generates a significant voltage of ∼47.8 mV using human body heat. This work proposes a new design strategy for high-performance organic thermoelectric fibers without additional post-processing, and the ultra-high output power and flexibility exhibit excellent combined application potential in both organic and inorganic TE fields.

TCO-free quantum dot light-emitting diodes based on PEDOT:PSS electrode treated with mild acid

Poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) has emerged as a promising candidate for high-cost transparent conductive oxide (TCO) electrodes. However, achieving high conductivity in PEDOT:PSS typically requires treatment with strong acids, which presents inherent risks. In this study, we propose an alternative approach utilizing a mild methane sulfonic acid (MSA) treatment for PEDOT:PSS as a transparent conductive electrode (TCE). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses unveil heightened phase separation between PEDOT and PSS by MSA treatment, accompanied by structural modifications in PEDOT. Moreover, the interfacial morphology between the MSA-treated electrode and the hole injection layer underwent significant changes. It is precisely this improved interface morphology, combined with enhanced conductivity, that significantly improves the efficiency of the obtained TCO-free blue quantum dot light-emitting diode (QLED) by 300 % compared to the reference device. Finally, leveraging the high performance of the TCO-free blue QLEDs, we fabricate the above device on a yellow-emissive phosphors-in-glass substrate, enabling a white light-emitting LED (WLED) device. This experiment not only elucidates the structural changes in PEDOT:PSS under mild acid treatment but also introduces an innovative strategy for developing high-performance PEDOT:PSS electrodes.

High-performance PEDOT: PSS/Cu mesh flexible transparent conductors with enhanced durability, adhesion and stability

High-performance PEDOT: PSS/Cu mesh flexible transparent conductors with enhanced durability, adhesion and stability

Characterization of PEDOT:PSS Nanofilms Printed via Electrically Assisted Direct Ink Deposition with Ultrasonic Vibrations.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has emerged as a promising conductive polymer for constructing efficient hole-transport layers (HTLs) in perovskite solar cells (PSCs). However, conventional fabrication methods, such as spin coating, spray coating, and slot-die coating, have resulted in PEDOT:PSS nanofilms with limited performance, characterized by a low density and non-uniform nanostructures. We introduce a novel 3D-printing approach called electrically assisted direct ink deposition with ultrasonic vibrations (EF-DID-UV) to overcome these challenges. This innovative printing method combines programmable acoustic field modulation with electrohydrodynamic spraying, providing a powerful tool for controlling the PEDOT:PSS nanofilm's morphology precisely. The experimental findings indicate that when PEDOT:PSS nanofilms are crafted using horizontal ultrasonic vibrations, they demonstrate a uniform dispersion of PEDOT:PSS nanoparticles, setting them apart from instances involving vertical ultrasonic vibrations, both prior to and after the printing process. In particular, when horizontal ultrasonic vibrations are applied at a low amplitude (0.15 A) during printing, these nanofilms showcase exceptional wettability performance, with a contact angle of 16.24°, and impressive electrical conductivity of 2092 Ω/square. Given its ability to yield high-performance PEDOT:PSS nanofilms with precisely controlled nanostructures, this approach holds great promise for a wide range of nanotechnological applications, including the production of solar cells, wearable sensors, and actuators.

A high-performance PEDOT:PSS platform electrochemical biosensor for the determination of HER2 based on carboxyl-functionalized MWCNTs and ARGET ATRP

Human epidermal growth factor receptor 2 (HER2) is an important breast cancer marker that is abnormally expressed in 20–30% of breast cancer patients.

Two-step post-treatment to deliver high performance thermoelectric device with vertical temperature gradient

The power factor of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film can be significantly improved by optimizing the oxidation level of the film in oxidation and reduction processes. However, precise control over the oxidation and reduction effects in PEDOT:PSS remains a challenge, which greatly sacrifices both S and σ. Here, we propose a two-step post-treatment using a mixture of ethylene glycol (EG) and Arginine (Arg) and sulfuric acid (H2SO4) in sequence to engineer high-performance PEDOT:PSS thermoelectric films. The high-polarity EG dopant removes the excess non-ionized PSS and induces benzenoid-to-quinoid conformational change in the PEDOT:PSS films. In particular, basic amino acid Arg tunes the oxidation level of PEDOT:PSS and prevents the films from over-oxidation during H2SO4 post-treatment, leading to increased S. The following H2SO4 post-treatment further induces highly orientated lamellar stacking microstructures to increase σ, yielding a maximum power factor of 170.6 μW m−1 K−2 at 460 K. Moreover, a novel trigonal-shape thermoelectric device is designed and assembled by the as-prepared PEDOT:PSS films in order to harvest heat via a vertical temperature gradient. An output power density of 33 μW cm−2 is generated at a temperature difference of 40 K, showing the potential application for low-grade wearable electronic devices.

Vapor phase polymerized high-performance Poly(3,4-ethylenedioxythiophene) using polyethyleneimine (PEI) as the base inhibitor and grafting agent for electrochromic medical face shields

Synthesizing of highly conductive conjugated polymers on target substrates must consider both the reaction regime and adhesion. Vapor phase polymerization (VPP) with a relatively simple procedure and mild reaction temperature (40–50 °C) is favorable for polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) on PET substrates. However, achieving high conductivity and good surface adhesion with target substrates has been challenging. Addressing this, we report that weak alkalinity and enriched amine groups of polyethyleneimine (PEI) were used as a base inhibitor and grafting agent during VPP to improve the PEDOT film's electrical and mechanical properties. The base-inhibited VPP results in a needle-like morphology with enhanced crystallinity in PEDOT, and with this, the conductivity of 1980 S/cm has been achieved. Moreover, many amine groups with high chemical activity in PEI make it successfully grafted on the polydopamine (PDA)-coated substrates. The surface grafting of PEI in PEDOT with PDA through Schiff base and Michael addition reactions make the PEDOT film resistant to ultrasonic cleaning in water or organic electrolyte, presenting significant potential in applying washable and cleanable electronics. We then demonstrate an anti-ultrasonic cleaning electrochromic display based on vapor phase polymerized PEDOT. This work experimentally confirms that PEI is critical in ensuring high-performance PEDOT films. Incorporating this technique on a PET-based medical face shield renders robust wearable electronics.

Template molecular weight-dependent PEDOT surface energy: impact on the photovoltaic performance of bulk-heterojunctions

A simple strategy based on the template Mw effect is developed for the realization of high-performance PEDOT AIMs with continuous gradient surface energies, and we found that low surface energy donor (or acceptor) based BHJs favor low surface energy PEDOT.

Nanoengineering of poly(3,4-ethylenedioxythiophene) for boosting electrochemical applications

As one of the most promising conducting polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) has attracted significant interests in electrochemical applications such as energy storage and electrochromism. However, the intrinsic PEDOT having a dense structure usually exhibits unsatisfactory electrochemical performance such as low charge storage capacity and optical modulation behavior, which limits their applications in supercapacitors and electrochromic devices. In this case, nanoengineering provides an effective strategy to improve the electrochemical performance by optimizing the conjugated structure of PEDOT. Herein, comprehensive reviews and discussions are conducted to demonstrate the nanoengineering of PEDOT for boosting the electrochemical applications. The advantages and shortcomings of PEDOT are discussed firstly, and thus introducing the necessary of nanoengineering for optimizing the electrochemical performance. Some strategies of nanoengineering are summarized according to the classification of physical and chemical methods. Then, the latest advances and progresses are reviewed in detail concerning the applications of nanoengineered PEDOT in supercapacitors and electrochromic devices. Finally, some challenges and prospects are proposed to show the further development of nanoengineering of advanced PEDOT materials and devices. We anticipate that this review will spark new ideas for the construction of high-performance PEDOT towards developing advanced electrochemical devices.

High-performance PEDOT:PSS-based thermoelectric composites

Over the past decades, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has emerged as one of the most attractive conducting polymers for organic electronics. In particular, PEDOT:PSS based composites have demonstrated its high potential as thermoelectrics. In this review, we aim to summarize the latest developments of PEDOT:PSS-based composite materials focusing on PEDOT:PSS/carbon nanostructures composites, PEDOT:PSS/tellurium composites, PEDOT:PSS/alloy composites, PEDOT:PSS/two-dimensional additives composites. The effects of various nanostructures such as nanoparticles, nanotube, nanowires and nanosheets on the thermoelectric properties of PEDOT:PSS was compared and discussed. The role of inorganic materials such as high-performance thermoelectric telluride-based alloys and certain two-dimensional materials e. g. SnSe, MoS2, as dopants in enhancing the thermoelectric properties of PEDOT:PSS composites was reviewed. The recent advances of post-treatment using some new chemical reagents such as dimethyl sulfone and sodium formaldehyde sulfoxylate to improve thermoelectric properties of PEDOT:PSS composites are also outlined. At the end, challenges and opportunities of PEDOT:PSS composites in enhancing the thermoelectric performance are commented.

Cationic nitrogen-doped graphene as a p-type modifier for high-performance PEDOT:PSS hole transporters in organic solar cells

This research paper reports the enhanced hole-transporting ability of widely utilized poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) achieved by applying cationic nitrogen-doped graphene (CNG) as a p-type modifier for efficient organic solar cells (OSCs). The power conversion efficiency (PCE) of the CNG-coated PEDOT:PSS-applied OSC reaches 2.76%, which is an increase of 40% compared to that of the pristine PEDOT:PSS-applied OSC (1.96%). The significantly enhanced performance is contributed by the increased hole-transporting ability, and the improved interfacial morphology of PEDOT:PSS, which affords high-quality active layers. © 2020 The Japan Society of Applied Physics.

Regulating monomer assembly to enhance PEDOT capacitance performance via different oxidants

The development of poly(3,4-ethylenedioxythiophene) (PEDOT) with high specific capacitance is the key to pursuing high-performance supercapacitors, and the electrochemical properties of PEDOT are closely related to the oxidation degree and conjugated chain length of its molecular chain. In this work, the influences of various oxidants (FeCl3, Fe(Tos)3 and MoCl5) on the molecular chain structure and capacitive properties of PEDOT via vapor phase polymerization were systematically investigated. Fe(Tos)3 can significantly improve the degree of oxidation and the length of the conjugated chain of PEDOT compared to FeCl3 and MoCl5, enhancing the conductivity and providing more active sites for Faraday reaction. Therefore, the PEDOT/P(Fe(Tos)3) electrode displays a considerable conductivity of 73 S cm-1, high areal capacitance (419 mF cm-2) and excellent electrochemical stability under the different bent state. Moreover, the conjugated structure strengthens the interaction between PEDOT chains, achieving good cycle stability. Therefore, Fe(Tos)3 is an ideal oxidant for obtaining high-performance PEDOT electrode materials.

An antimonene modified hole extraction layer for high efficiency PEDOT:PSS-free nonfullerene organic solar cells

In this paper, a bilayer hole extraction layer (HEL) with solution-processed molybdenum trioxide (MoO 3 ) and two-dimensional (2D) material of antimonene was developed to achieve high performance nonfullerene organic solar cells (NF–OSCs). The application of antimonene facilitates effective charge extraction and lowered recombination loss, achieving improved photovoltaic performance. By inserting the antimonene layer, power conversion efficiency ( PCE ) of devices with MoO 3 HEL was increased from 8.92% to 11.30% in OSCs with non-fullerene systems of PBDB-T-2F:IT-4F, which was even much higher than that of the devices with PEDOT:PSS HEL (10.59%). Results make it clear that the solution-processed bilayer MoO 3 /antimonene HEL shows great potential for application in high performance PEDOT:PSS-free NF–OSCs. • A bilayer HEL with solution-processed MoO 3 and antimonene was developed to achieve high performance PEDOT:PSS-free NF-OSCs. • The MoO 3 /antimonene HEL favors the efficient operation of NF–OSCs, achieving suppressed trap-limited recombination and enhanced charge extraction efficiency.

Solution Processed Organic/Silicon Nanowires Hybrid Heterojunction Solar Cells Using Organosilane Incorporated Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) as Hole Transport Layers.

Hybrid heterojunction solar cells (HHSCs) using crystalline Si nanowires (SiNWs) as the absorber and conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole-selective transport layer (HTL) show great potential in both low-cost and high-power conversion efficiency (PCE). However, due to the poor wettability of the PEDOT:PSS solution on SiNWs, conformal coverage of PEDOT:PSS on SiNWs is not easy to achieve. Here, an effective method was developed to decrease the surface tension of the PEDOT:PSS and increase the wettability between PEDOT:PSS and SiNWs by incorporating organosilane into the PEDOT:PSS solution. Two kinds of organosilanes including tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMO) were selected as the additives. The surface passivation quality of the SiNWs was dramatically enhanced. The HHSCs utilizing VTMO as the additive show a higher open circuit voltage and higher PCE compared with the TMOS adding ones. By spin-coating Ag nanowires onto the PEDOT:PSS HTL layer and using spin-coated phenyl-C61-butyric acid methyl ester as the electron-selective transport layer, a champion PCE up to 18.12% and a fill factor of 80.1% have been achieved on the full solution processed PEDOT:PSS/n-type SiNWs HHSCs. The findings provide a simple and promising method to achieve high-performance PEDOT:PSS/SiNWs HHSCs.

Wearable Temperature Sensors with Enhanced Sensitivity by Engineering Microcrack Morphology in PEDOT:PSS-PDMS Sensors.

Wearable temperature sensors with high sensitivity, linearity, and flexibility are required to meet the increasing demands for unobtrusive monitoring of temperature changes indicative of the onset of infections and diseases. Herein, we present a new method for engineering highly sensitive and flexible temperature sensors made by sandwiching a poly(3,4-ethylenedioxythiophene):polystyrene (PEDOT:PSS) sensing film between two poly(dimethylsiloxane) (PDMS) substrates. Pre-stretching the sensor to a certain strain can create stable microcracks in the sensing layer that bestow high senstivity and linearity. The average length and density of the microcracks, which dictate the sensor's temperature sensitivity, can be engineered by controlling three key processing parameters, incuding (a) pre-stretching strain, (b) sulfuric acid treatment time, and (c) surface roughness of the substrate. For a given acid treatment time and surface roughness condition, the density and average length of the microcracks increase pre-stretching strain. A smooth PDMS substrate tends to yield long and straight cracks in the PEDOT:PSS film, compared to shorter microcracks with higher density on rough surfaces. Crack density can be further increased via sulfuric acid treatment with an optimum duration of approximately 3 h. Prolonged treatment would result in weak adhesion between the PEDOT:PSS film and the PDMS substrate, which in turn reduces the microcrack density but increases the crack length. By optimizing the three design parameters we have designed a high performance PEDOT:PSS-PDMS sensor that provides a combined high temperature sensitivity of 0.042 °C-1 with an excellent linearity of 0.998 (from 30 to 55 °C), better than the highest temperature sensitivity of PEDOT:PSS based sensors reported in the literature. With a good optical transparency, high temperature sensitivity, excellent linearity, and high flexibility, this microcrack-based sensor is a very promising wearable temperature-sensing solution.

High-Performance PEDOT:PSS Flexible Thermoelectric Materials and Their Devices by Triple Post-Treatments

Searching an effective method to enhance the thermoelectric properties of flexible organic films can significantly widen the application of flexible thermoelectric devices. Tuning the microstacking structure and oxidation level can effectively optimize the thermoelectric properties of poly(3,4 ethylenedioxithiophene):poly(styrenesulfonate)(PEDOT:PSS) organic films. Here, we adopt triple post-treatments with formamide (CH3NO), concentrated sulfuric acid (H2SO4), and sodium borohydride in sequence to engineer flexible PEDOT:PSS thermoelectric films. A high power factor of 141 μWm−1 K−2 at 25 °C has been obtained for the PEDOT:PSS film. Such a high power factor stems from the high σ (1786 Scm−1) and S (28.1 μVK−1) after posttreatment with CH3NO, H2SO4, and NaBH4 in order. The increased carrier mobility resulting from both the selective removal of excess insulating PSS within the films and the conformation transition after CH3NO and H2SO4 treatments is responsible for the enhancement of σ, while the subsequent NaBH4 treatment optimize the electrical properties (σ and S) by modulating the oxidation level. A homemade thermoelectric device has also been fabricated using the as-prepared flexible PEDOT:PSS films and had a high output power density of ∼1 μWcm−2 with human arm as a heating source. This study indicates that flexible thermoelectric devices based on cheap conducting polymers have great potential in wearable electronics.

Enhanced electrical properties of poly(3,4-ethylenedioxythiophene:poly(4-styrenesulfonate) using graphene oxide

Abstract Thin film of graphene oxide and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) is a promising candidate of transparent conductive electrode material for economical thin film devices. In this research, spin coating technique was utilized to fabricate high-performance PEDOT:PSS/GO (graphene oxide) thin films. Graphene oxide sheets were evenly dispersed in aqueous solution of PEDOT:PSS. The solution-processing of PEDOT:PSS/GO was simplified in this experiment to enable economical commercialization of electronic devices. The fabricated PEDOT:PSS/GO thin films have been proven to have outstanding electrical properties. When 5% of graphene oxide was added into the solution, the electrical conductivity of PEDOT:PSS/GO thin film was found to be 90 S/cm, which is an increase of 5 times compared to the conductivity of pristine PEDOT:PSS. This exceptional improvement is attributed to the higher carrier mobility, due to interaction between GO with PEDOT via π→π stacking.

High-Performance PEDOT:PSS/Hexamethylene Diisocyanate-Functionalized Graphene Oxide Nanocomposites: Preparation and Properties.

Graphene oxide (GO) has emerged as an ideal filler to reinforce polymeric matrices owing to its large specific surface area, transparency, flexibility, and very high mechanical strength. Nonetheless, functionalization is required to improve its solubility in common solvents and expand its practical uses. In this work, hexamethylene diisocyanate (HDI)-functionalized GO (HDI-GO) has been used as filler of a conductive polymer matrix, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The nanocomposites have been prepared via a simple solution casting method, and have been characterized by scanning electron microscopy (SEM), UV–Vis and Raman spectroscopies, X-ray diffraction (XRD), thermogravimetric analysis (TGA), tensile tests, and four-point probe measurements to get information about how the HDI-GO functionalization degree (FD) and the HDI-GO concentration in the nanocomposite influence the final properties. SEM analysis showed a very homogenous dispersion of the HDI-GO nanosheets with the highest FD within the matrix, and the Raman spectra revealed the existence of very strong HDI-GO-PEDOT:PSS interactions. A gradual improvement in thermal stability was found with increasing HDI-GO concentration, with only a small loss in transparency. A reduction in the sheet resistance of PEDOT:PSS was found at low HDI-GO contents, whilst increasing moderately at the highest loading tested. The nanocomposites showed a good combination of stiffness, strength, ductility, and toughness. The optimum balance of properties was attained for samples incorporating 2 and 5 wt % HDI-GO with the highest FD. These solution-processed nanocomposites show considerably improved performance compared to conventional PEDOT:PSS nanocomposites filled with raw GO, and are highly suitable for applications in various fields, including flexible electronics, thermoelectric devices, and solar energy applications.

All-Solution-Processed Metal-Oxide-Free Flexible Organic Solar Cells with Over 10% Efficiency.

All-solution-processing at low temperatures is important and desirable for making printed photovoltaic devices and also offers the possibility of a safe and cost-effective fabrication environment for the devices. Herein, an all-solution-processed flexible organic solar cell (OSC) using poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) electrodes is reported. The all-solution-processed flexible devices yield the highest power conversion efficiency of 10.12% with high fill factor of over 70%, which is the highest value for metal-oxide-free flexible OSCs reported so far. The enhanced performance is attributed to the newly developed gentle acid treatment at room temperature that enables a high-performance PEDOT:PSS/plastic underlying substrate with a matched work function (≈4.91 eV), and the interface engineering that endows the devices with better interface contacts and improved hole mobility. Furthermore, the flexible devices exhibit an excellent mechanical flexibility, as indicated by a high retention (≈94%) of the initial efficiency after 1000 bending cycles. This work provides a simple route to fabricate high-performance all-solution-processed flexible OSCs, which is important for the development of printing, blading, and roll-to-roll technologies.

High-performance, polymer-based direct cellular interfaces for electrical stimulation and recording

Due to the trade-off between their electrical/electrochemical performance and underwater stability, realizing polymer-based, high-performance direct cellular interfaces for electrical stimulation and recording has been very challenging. Herein, we developed transparent and conductive direct cellular interfaces based on a water-stable, high-performance poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film via solvent-assisted crystallization. The crystallized PEDOT:PSS on a polyethylene terephthalate (PET) substrate exhibited excellent electrical/electrochemical/optical characteristics, long-term underwater stability without film dissolution/delamination, and good viability for primarily cultured cardiomyocytes and neurons over several weeks. Furthermore, the highly crystallized, nanofibrillar PEDOT:PSS networks enabled dramatically enlarged surface areas and electrochemical activities, which were successfully employed to modulate cardiomyocyte beating via direct electrical stimulation. Finally, the high-performance PEDOT:PSS layer was seamlessly incorporated into transparent microelectrode arrays for efficient, real-time recording of cardiomyocyte action potentials with a high signal fidelity. All these results demonstrate the strong potential of crystallized PEDOT:PSS as a crucial component for a variety of versatile bioelectronic interfaces.