PSS Dispersion Research Articles

A transparent, solvent-free laminated top electrode for perovskite solar cells

A simple lamination process of the top electrode for perovskite solar cells is demonstrated. The laminate electrode consists of a transparent and conductive plastic/metal mesh substrate, coated with an adhesive mixture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS, and sorbitol. The laminate electrode showed a high degree of transparency of 85%. Best cell performance was achieved for laminate electrodes prepared with a sorbitol concentration of ~30 wt% per milliliter PEDOT:PSS dispersion, and using a pre-annealing temperature of 120°C for 10 min before lamination. Thereby, perovskite solar cells with stabilized power conversion efficiencies of (7.6 ± 1.0)% were obtained which corresponds to 80% of the reference devices with reflective opaque gold electrodes.

Flexible and highly stable organic electrochemical transistors for bioelectronics applications

Event Abstract Back to Event Flexible and highly stable organic electrochemical transistors for bioelectronics applications Fabio Cicoira1, Shiming Zhang1, Elizabeth Hubis1, Camille Girard1 and Prajwal Kumar1 1 École Polytéchnique de Montréal, Génie Chimique, Canada In recent years, research on organic electrochemical transistors (OECTs) is rapidly increasing due to its potential applications in bioelectronics. Although flexible substrates are critically required to produce devices that conform to any deformable surface of the targets, fundamental physics of flexible OECTs are remain largely unexplored. In this research project, we developed low cost, transparent, and micro-scale OECTs arrays based on conducting polymer, poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS), on a flexible poly(ethylene terephthalate) (PET) substrate. Significantly, the PEDOT:PSS film (spin-coated from CleviosTM PH1000 PEDOT:PSS dispersion mixed with 5% glycerol), without the addition of any cross-linking agent, shows robust adhesion on the substrate even after 3-month water immersion tests. Accordingly, a widespread fabrication procedure has nto only been simplified but rendered completely biocompatible. Transistor channel lengths as short as 5 um are achieved by patterning with a biocompatible fluorinated photoresist. Bending tests show that the film conductivity is stable at different bending angles. This work significantly contributes to the organic bioelectronics research aiming at practical applications such as brain activity monitoring – thanks to the biocompatible fabrication process chosen for device realization.

Visible Luminescence of Dedoped DBU-Treated PEDOT:PSS Films

Dedoping of PEDOT:PSS by a simple and physical process has been performed by the addition of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), a strong organic base, in the PEDOT:PSS aqueous dispersion. The DBU-treated PEDOT:PSS samples showed a strong absorption band at 600 nm (π–π* transition) and a small band at 900 nm (polaronic band), which indicates that some PEDOT chains were being reduced. The dedoping efficiency depended of the amount of DBU added to the aqueous PEDOT:PSS dispersion. The DBU-treated PEDOT:PSS aqueous dispersions and films showed a strong yellow emission, visible with the naked eye, when they were excited with a 488 nm laser. In addition, the same emission features were observed using another reducing agent like sodium hydroxide (NaOH), which indicates that the emission originates from neutral PEDOT chains rather than artifacts. Finally, Raman and FTIR spectroscopies were used to figure out the mechanism responsible for the PEDOT reduction. The reduction of PEDOT chains is due to the form...

Aging process of PEDOT:PSS dispersion and robust recovery of aged PEDOT:PSS as a hole transport layer for organic solar cells

Conducting p-type polymer of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been widely used for organic optoelectronics, particularly as a hole transport layer for organic solar cells. While the aged PEDOT:PSS dispersion impacts device performance, the aging of PEDOT:PSS dispersion have not been well investigated. Moreover, the recovery process of aged (two-year-old) PEDOT:PSS dispersion has not been demonstrated yet. Herein, it is found that aqueous PEDOT:PSS dispersion undergoes extensive phase separation during the aging process, resulting in both nanoscale and macroscale hydrophobic PEDOT-rich agglomerates. When the aged PEDOT:PSS thin film is integrated into P3HT:PCBM organic solar cells, the PEDOT-rich agglomerates trap the photogenerated holes at the PEDOT:PSS/P3HT interface, resulting in poor extraction efficiency in organic solar cells. To recover a hole transport functionality from aged PEDOT:PSS, three different solvents such as isopropyl alcohol (C3H7OH), ethanol (C2H5OH) and methanol (CH3OH) are investigated. Among them, it is found that isopropyl alcohol (IPA) yielded very uniform PEDOT:PSS thin film layer. This is because hydrophobic functional groups of IPA solvent facilitated the preferential solvation of phase separated hydrophobic PEDOT-rich agglomerates. However, when non-optimal concentration of IPA solvents was added into the aged PEDOT:PSS dispersion, the size of PEDOT-rich agglomerates was adversely enlarged. When organic solar cells were fabricated using more than a two-year-old PEDOT:PSS that was treated with IPA solvent, the resulting device performance of organic solar cells was fully recovered and became comparable or better than that of organic solar cells fabricated with fresh PEDOT:PSS.

Voltammetric determination of phytoinhibitor maleic hydrazide using PEDOT:PSS composite electrode

Maleic hydrazide (MH) was successfully detected using a novel electrochemical sensor based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)-carboxymethyl cellulose-single-walled carbon nanotubes modified glassy carbon electrode (PEDOT:PSS-CMC-SWCNT/GCE). A commercially available aqueous PEDOT:PSS dispersion with good processability and conductivity was used as electrode modified substrate material, while a water-soluble and adhesive CMC was selected as both binder and dopant to improve the long-term electrode stability in water of the PEDOT:PSS composite film and obtain synergistically enhanced electrocatalytic ability for analytes. A commercially available SWCNT dispersion with good processability, enhanced electrocatalytic ability and large rough surface area was selected as enhancer to improve the sensing performance of PEDOT:PSS composite electrode. The properties of the prepared composite film and its electrode were characterized and employed for the electrochemical detection of MH. The electrochemical behaviors of MH, optimum experimental parameters, and the performance of sensing electrode were investigated. The fabricated PEDOT:PSS-CMC-SWCNT/GCE accelerated electron transfer, enhanced synergistically electrocatalytic ability toward MH oxidation and displayed excellent sensing performance such as wide linear range (0.8–51μM) and a low limit of detection (0.1μM) and good sensing stability.

Conducting poly(3,4-ethylenedioxythiophene):poly(styrene- sulfonate) film electrode with superior long-term electrode stability in water and synergistically enhanced electrocatalytic ability for application in electrochemical sensors

A novel poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) composite film with superior stability in water, adhesion and flexibility, which is very critical for maintaining the long-term stability in water of the PEDOT:PSS film electrode, was easily prepared by introducing a water-soluble, anionic, non-toxic and biocompatible biopolymer (sodium carboxymethyl cellulose, Na-CMC) into a commercially available aqueous dispersion of the conducting polymer (PEDOT:PSS dispersion). The high conducting PEDOT:PSS-CMC film exhibited good flexibility and long-term stability in water after being soaked in water for 35 days. The high performance film electrode with excellent adhesion, long-term electrode stability in water (retaining almost 99.4% of its original activity for 105 days), and electrochemical properties was prepared facilely by drop-coating, and displayed good synergistically enhanced electrocatalytic ability towards the anodic oxidation of harmful substances and nutritional ingredients in edible agro-products, which were employed for its application in electrochemical sensors. The simultaneous or individual detection of maleic hydrazide, salicylic acid, nitrite, sunset yellow, and tryptophan was successfully realized using PEDOT:PSS-CMC/GCE, and exhibited superior sensing stability. All satisfactory results indicated that the introduction of CMC into PEDOT:PSS could improve the flexibility, adhesion, long-term electrode stability in water and electrocatalytic ability, which would provide a promising platform for the application in electrochemical fields of the high performance film electrode, especially the application in electrochemical sensors.

Non-aqueous PEDOT:PSS dispersion for improved inverted organic solar cells

ABSTRACTA non-aqueous Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) dispersion was developed to enable the accommodation of non-polar additives. This additional functionalisation targets selected interface characteristics and results in an improved adhesion of PEDOT:PSS on the photo-active layer. Such mechanical robustness is paramount in inverted organic photovoltaic cells contributing to improved long-term stability.

PEDOT:PSS incorporated silver nanoparticles prepared by gamma radiation for the application in organic solar cells

Poly(3,4-ethylenedioxythiophene):Polystyrene sulfonate (PEDOT:PSS) is a dispersion used as a buffer layer on the ITO electrode in the organic solar cells. Silver nanoparticles (Ag NPs) are incorporated to the dispersion using two different strategies. The first is by reduction of silver ions in the PEDOT:PSS dispersion. Chemical reduction of silver ions using sodium borohydried is compared with reduction using gamma radiation. The TEM and UV-visible spectra indicates that smaller Ag NPs are obtained for the chemical reduction method than those obtained from the radiochemical. The second strategy, is by preparing Ag NPs in polyvinyl pyrolidone (PVP) solution using gamma irradiation then adding them to the PEDOT:PSS dispersion. Layers of the PEDOT:PSS incorporated different concentrations of Ag NPs (1, 2, 4, 6, 8, 10%) are formed. The SEM and AFM studies of the layers morphology reveal that smooth morphology on the obtained for layers containing Ag NPs up to concentrations of 4%.

Optimisation of the fabrication conditions of the PEDOT:PSS layer in organic solar cells based on P3HT:PCBM

This study aimed at studying the effect of the quality and thickness of PEDOT:PSS buffer layer that used in organic solar cells, on the performance of the cell. The effect of diluting the PEDOT:PSS dispersion with methanol on the morphology and thickness of the thin layer was studied using SEM and AFM. The results showed the dilution with 1:2. The effect of the buffer layer thickness on the performance of the solar cells based on P3HT:PCBM was studied using AFM and I-V measurements. It was found that a layer of thickness 40 nm is optimum for the best performance.

Influence of coating parameters on textile and electrical properties of a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/polyurethane-coated textile

Textile coatings with electrical conductivity were obtained by the addition of poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) and ethylene glycol (EG) to a polyurethane (PU)-based coating formulation. Variations of the coating formulation, the coating amount and the drying conditions, as well as the absence of an annealing step, were investigated. The coated fabrics were evaluated for tear strength and bending rigidity as well as surface resistivity and appearance before and after Martindale abrasion. A high proportion of PEDOT:PSS dispersion in the formulation and the presence of EG provided low surface resistivity. This composition resulted in softer samples with higher tear strength than those containing more PU-binder. All coatings proved to withstand abrasion to a similar extent. The surface resistivity increased gradually with the abrasion, about one half order of magnitude, except for those coatings that had been subjected to a faster drying process, where the surface resistivity increased somewhat faster.

Ionic liquid induced supramolecular self-assembly of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) thin films with enhanced conductivity and tunable nanoporosity

We present a facile strategy, for the first time as the best of our known, to prepare high conducting poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT:PSS) film with a novel nanoporous morphol- ogy directly from a commercial PEDOT:PSS dispersion. Both conducting properties and surface morphology of PEDOT:PSS film can be systematically tunable by simply controlling addition of an ionic liquid, 1,3-dihydroxy-2- methylimidazolium bis(trifluoromethylsulfonyl)-imide (DHIL). The electrical conductivity increases from 0.07 for pristine PEDOT:PSS to 55 S cm -1 after addition of 2 wt% DHIL, with no necessary of any further heat treatment, which is around 800 times increase in the electrical conductivity. On the other hand, the discrete compact PEDOT:PSS film is gradually transformed into the nanoporous film with addition of DHIL. It is considered that such size-tunable porous PEDOT:PSS films with high surface area as well as high conductivity combining solution-processibility show great potential in applications that require high interfacial area, such as flexible electronic components, next- generation catalytic, and separation supports.

Core–shell composite latexes derived from PEDOT:PSS dispersion and the preparation of conductive, flexible and transparent films

In this study, a highly conductive poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic acid) (PEDOT:PSS) dispersion served as a stabilizer for producing conductive PEDOT:PSS–poly(styrene-co-butyl acrylate) (PEDOT:PSS–P(St–BA)) composite latexes by emulsion polymerization. Furthermore, soft latex particles of poly(styrene-co-butyl acrylate), P(St–BA), were synthesized via emulsion polymerization and then mixed with the conductive PEDOT:PSS–P(St–BA), followed by casting on the substrate. After drying, conductive composite films with flexibility and transparency could be obtained. The particle size and morphology of PEDOT:PSS–P(St–BA) were observed by a scanning electron microscope. The film surface resistance, thickness, conductivity and transmittance of the composite films were measured and studied. Bending tests were also conducted to detect the flexibility. According to the results, the composite films showed high transmittance while possessing good conductivity and superior flexibility. The method may serve as a practical approach to fabricate conductive, flexible and transparent films.

In Situ Formation of MoO3 in PEDOT:PSS Matrix: A Facile Way to Produce a Smooth and Less Hygroscopic Hole Transport Layer for Highly Stable Polymer Bulk Heterojunction Solar Cells

AbstractA solution‐processed neutral hole transport layer is developed by in situ formation of MoO3 in aqueous PEDOT:PSS dispersion (MoO3‐PEDOT:PSS). This MoO3‐PEDOT:PSS composite film takes advantage of both the highly conductive PEDOT:PSS and the ambient conditions stability of MoO3; consequently it possesses a smooth surface and considerably reduced hygroscopicity. The resulting bulk heterojunction polymer solar cells (BHJ PSC) based on poly[2,3‐bis‐(3‐octyloxyphenyl)quinoxaline‐5,8‐diyl‐alt‐thiophene‐2,5‐diyl] (TQ1):[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM) blends using MoO3‐PEDOT:PSS composite film as hole transport layer (HTL) show considerable improvement in power conversion efficiency (PCE), from 5.5% to 6.4%, compared with the reference pristine PEDOT:PSS‐based device. More importantly, the device with MoO3‐PEDOT:PSS HTL shows considerably improved stability, with the PCE remaining at 80% of its original value when stored in ambient air in the dark for 10 days. In comparison, the reference solar cell with PEDOT:PSS layer shows complete failure within 10 days. This MoO3‐PEDOT:PSS implies the potential for low‐cost roll‐to‐roll fabrication of high‐efficiency polymer solar cells with long‐term stability at ambient conditions.

Hybrid method involving atmospheric plasma treatment and inkjet deposition for the development of conductive patterns on flexible polymers

In this study, the flexible polymer substrate polyethylene naphthalate (PEN) was modified under two different plasma chemistries, namely helium–oxygen (He–O2) and helium–water vapor (He–H2O) plasmas at atmospheric pressure and room temperature. Surface changes related to wettability, chemical functionalization, surface energy, and morphology after plasma treatment were investigated using water contact angle (WCA) goniometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Each plasma resulted in a more hydrophilic PEN surface, with WCA decreasing by 68% and 85% for He–O2 and He–H2O plasma treated PEN, respectively, after only 1.0s of exposure. An aging study of plasma treated PEN shows an increase in WCA that is still 30° lower than that of the as-received PEN after 1month. XPS and AFM results show that improved wettability of the plasma modified PEN is due to the oxidation of the surface and not due to the increased surface roughness. To promote a roll-to-roll process of atmospheric plasma treatment and inkjet deposition, printing was performed using the conductive polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) on the as-received and plasma treated PEN surfaces where the shape and morphology of the lines were studied. Each plasma treated PEN surface exhibited well-defined, uniform inkjet-printed lines due to the improved wettability and increased surface energy. After scanning electron microscopy (SEM) analysis of the PEDOT:PSS dispersion of a single drop on each substrate, the He–H2O plasma treated surface led to less agglomeration of PEDOT:PSS and a more homogeneous drop deposit.

Highly efficient all solid state dye-sensitized solar cells by the specific interaction of CuI with NCS groups II. Enhancement of the photovoltaic characteristics

Highly efficient all solid state dye-sensitized solar cells (DSSC) were fabricated by the specific interaction of CuI with the NCS groups of the dye molecules and that of the counter electrodes. The counter electrodes were prepared by blending nano size carbon in the PEDOT:PSS dispersion. The counter electrodes were covered with the solution containing guanidine thiocyanate, and heated to give the electrode with larger number of NCS groups. Electrostatic adsorption between PEDOT:PSS and guanidine was investigated by X-ray photoelectron spectroscopy (XPS). DSSC were prepared by connecting the NCS groups of the dye molecule with those of the counter electrode with large surface area. The performances of the resulting DSSC were improved dramatically by the increase of the NCS groups on the counter electrode. It is noteworthy that the performances of the cell were higher than that of the cells prepared by the conventional liquid electrolyte. The highly efficient all solid state DSSC are manufactured with inexpensive and low quality materials, and the practical use is promising.

Cooperative doping in polyaniline-poly(ethylene-3,4-dioxythiophene): poly(styrenesulfonic acid) composite system

Interaction of emeraldine base of polyaniline (PANI) and poly(ethylene-3,4-dioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) in a complex solution is shown to lead to a new polymer complex whose components act to each other to favor an increase in intramolecular conductivity in both PANI and PEDOT backbones. Asymmetric changes in intramolecular conductivity of the polymer mixture have been demonstrated upon addition of PANI to PEDOT:PSS dispersion and vise versa. Complex films cast from the solution revealed a specific spherulite-like morphology and increased conductivity up to one order of magnitude as compared to films of the net PEDOT:PSS, which allowed us to conclude on formation of a qualitatively new system rather than a simple blend of the polymers and the effect of cooperative doping of the components by each other, respectively. The doping efficiency was shown to be strongly dependent on the solvent environment and concentration of the polymers in solutions. It is discussed that the increase in conductivity of the composite system is controlled not only by the direct doping of PANI with PSS, but also by weakening of interaction of PSS with the PEDOT backbone itself as a result of the above doping process.

Synthesis and optoelectronic properties of high transparent polymer based anode materials with good wetting abilities and their application in electroluminescent devices

Electroluminescent (EL) phenomenon has been widely used in the illumination industry such as light emitting diode (LED) and organic light emitting diode (OLED) nowadays. In this research, flexible EL devices were fabricated by using the flexible substrates and conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) dispersions as the anode materials. The PEDOT:PSS dispersion was firstly prepared by oxidative polymerization while PSS was served as a polymeric template. Via introducing poly(vinyl pyrrolidone) (PVP) ethanol solution into the PEDOT:PSS dispersion, viscosity and wetting ability of the mixed PEDOT:PSS/PVP solution were enhanced in the same time. The three formed PEDOT:PSS/PVP thin films on glass substrates presented good conductivity and high transmittance (transmittance >76%). The wetting abilities of these PEDOT:PSS/PVP dispersions on the PET films coated with the low dielectric resin were evaluated from the contact angle measurements. It showed that the contact angle was decreased with increasing the addition of PVP ethanol solution. The different PEDOT:PSS/PVP dispersions were further used as the anode material in the EL flat plates and EL wires by dip coating process. Uniform and smooth conductive thin films with high transmittance were formed on the low dielectric resin layer. The luminance of these EL devices was observed and photographed after connecting to 110V AC power.

Solution Processed Vanadium Pentoxide as Charge Extraction Layer for Organic Solar Cells

Organic solar cells (OSCs) based on polymers and small molecules have seen a tremendous increase in interest during the past few years. Signifi cant progress in this fi eld seeded the prospect for a cost-effective and easy-to-fabricate photovoltaic technology—typical advantages claimed for organic (opto-)electronic devices. Very recently, certifi ed cell effi ciencies in excess of 7% have been reported for polymer based cells. [ 1 ] For large-scale and high-throughput production of OSCs, liquid processing of the functional layers is desirable. Aside from the active organic layers, inter-layers are typically required to facilitate the extraction of the photo-generated charges. Specifi cally, on the anode side, polyethylene dioxythiophene:polystyrenesulfonate (PEDOT:PSS) is regularly used. [ 2 ] However, PEDOT:PSS is burdened with structural and electrical inhomogeneity [ 3,4 ] and has been demonstrated to be an origin of limited device lifetime. [ 5 ] Particularly, the aqueous PEDOT:PSS dispersion and the acidic nature can cause substantial degradation. [6,7 ] Very recently, transition metal-oxides (TMOs) such as molybdenum-, vanadium-, or tungsten-oxide (MoO 3 , V 2 O 5 , and WO 3 ) with high work functions (WFs) of up to 6.9 eV have been shown to be promising alternatives to PEDOT:PSS. [ 8‐11 ] TMOs have also been used as constituents of the connecting architecture in stacked organic light-emitting diodes and organic tandem solar cells. [ 12‐15 ] The unique energetics of these TMOs has so far been predominantly

High work function transparent middle electrode for organic tandem solar cells

The use of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) in combination with ZnO as middle electrode in solution-processed organic tandem solar cells requires a pH modification of the PEDOT:PSS dispersion. We demonstrate that this neutralization leads to a reduced work function of PEDOT:PSS, which does not affect the performance of polythiophene:fullerene solar cells, but results in a lower open-circuit voltage of devices based on a polyfluorene derivative with a higher ionization potential. The introduction of a thin layer of a perfluorinated ionomer recovers the anode work function and gives an open-circuit voltage of 1.92 V for a double junction polyfluorene-based solar cell.

Characterization of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) adsorption on cellulosic materials

The interaction between poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) and cellulosic fibers was characterized in order to obtain further understanding of the conductivity properties of the modified cellulosic fiber material. Microcrystalline cellulose (MCC) was used as a model surface to study the adsorption behavior at various pH and salt concentrations, while samples of low-conductivity paper, normally used for the production of electrical insulation papers, were dipped into PEDOT:PSS dispersion and air-dried for X-ray photoelectron spectroscopy (XPS) studies. The results showed a strong interaction between the MCC and PEDOT:PSS, which implied a broad molecular distribution of the conducting polymer. With increasing pH, less amount of the conducting polymer was adsorbed whereas the amount adsorbed passed through a maximum value with varying salt concentration. Zeta potential measurement and polyelectrolyte titration were used to determine the surface charge of both suspended MCC particles and dispersed PEDOT:PSS at various pH levels and salt concentrations. Dip-coated paper samples exhibited two peaks in the S(2p) XPS spectra at 168–169 and 164–165 eV which correspond to the sulfur signals of sulfonate (in PSS) and in thiophene (in PEDOT), respectively. It was found that the PEDOT:PSS with a ratio of 1:2.5 was adsorbed more in the base paper than that with a ratio of 1:6. The PEDOT:PSS ratio on the surface of the cellulosic material was higher than that in the bulk liquid for all samples. The results indicated that PEDOT was preferentially adsorbed rather than PSS. The degree of washing of the conducting polymer did not significantly affect the PEDOT enhancement on the surface.