Morphology Of PEDOT Research Articles

Long-term noninvasive cardiac monitoring via Neutralized interfacial design for noise-suppressed near-infrared organic photodetectors

Organic photodetectors (OPDs) are the prime candidates for realizing commercial photoplethysmography (PPG) sensors in the future, although their performance and stability limitations remain as challenges. This study presents a strategy for fabricating high-precision, long-term, sustainable OPDs for non-invasive cardiac monitoring. In this work, the use of appropriate amounts of heterocyclic 1,3-diazoles (solid surfactants) enhances the morphology of PEDOT:PSS films and optimizes its energy level alignment, thus directly reducing the leakage current noise and improving the stability of the OPD. The OPDs with 0.5 wt% heterocyclic 1,3-diazole demonstrate enhanced dark current suppression and detectivity enhancement in the photoconductive and self-powered modes. Improved charge recombination dynamics and optimal resistance ratios lead to better performance of the champion device under low-intensity illumination. The champion device yields a more precise Photoplethysmography (PPG) signal under normal and exercise conditions when using a near-infrared light source, and it maintains a PPG signal intensity of more than 90 % after 315 days (7560 h) of storage in a nitrogen atmosphere. Optimized PPG sensors based on flexible substrates maintain signal intensity after seven days of air storage. The low hysteresis behavior also verifies that the optimized device has higher driving stability. High-reliability, high-validity accelerated photoplethysmography (APG) demonstrated that the champion PPG sensor would be used for accurate cardiovascular diagnostics, even over an extended period.

Solution‐Processed Tandem Quantum‐Dot Light‐Emitting Diodes with Dual Charge Generation Interfaces: Achieving Over Threefold Efficiency Enhancement

AbstractDespite the commercialization of thermally evaporated tandem organic light‐emitting diodes (OLEDs), challenges remain for solution‐processed tandem quantum‐dot light‐emitting diodes (QLEDs), including low efficiency and solvent‐induced damage to functional layers. Therefore, there is an urgent need for the optimization of the interconnecting layer (ICL) design in order to fabricate high‐performance solution‐processed tandem QLEDs. Here, by introducing a phosphomolybdic acid (PMA) layer between poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and poly(9‐vinylcarbazole) (PVK), an novel ICL, PVK/PMA/PEDOT:PSS/ZnO is proposed, with dual charge generation interfaces (CGIs): PVK/PMA and PEDOT:PSS/ZnO. The PMA interlayer serves not only smoothing the morphology of PEDOT:PSS to improve charge transport, but also forming a PVK/PMA CGI to enhance charge generation. Based on the excellent electrical and optical properties of the dual‐CGI ICL, the solution‐processed inverted tandem red QLEDs achieve an increased external quantum efficiency (EQE) of over three times compared to single‐junction devices. This provides a novel approach for the high‐efficiency solution‐processed tandem QLEDs, paving the way for the practical application of QLEDs.

Tuning of Morphological and Antibacterial Properties of Poly(3,4-ethylenedioxythiophene):Peroxodisulfate by Methyl Violet.

This study demonstrates a one-step synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) in the presence of the methyl violet (MV) dye. The structural properties of PEDOT:peroxodisulfate were studied using Raman and MALDI-TOF spectroscopies. The use of the MV dye in the polymerization process resulted in a change in the typical irregular morphology of PEDOT:peroxodisulfate, leading to the formation of spherical patterns. SEM and TEM analyses revealed that increasing the dye concentration can produce larger spherical aggregates probably due to the hydrophobic and π-π interactions. These larger aggregates hindered the charge transport and reduced the electrical conductivity. Interestingly, at higher dye concentrations (0.05 and 0.075 M), the PEDOT:peroxodisulfate/MV films exhibited significantly improved antibacterial activity against Staphylococcus aureus and Escherichia coli. Furthermore, the PEDOT:peroxodisulfate films with the incorporated MV dye exhibited a well-defined and repeatable redox behavior. The remarkable amalgamation of their optical, electrochemical and antibacterial properties provides the PEDOT:peroxodisulfate/MV materials with an immensely diverse spectrum of applications, including in optical sensors and medical devices.

Improving open-circuit voltage and short-circuit current of high-efficiency silicon-based planar heterojunction solar cells by combining V2O5 with PEDOT:PSS

In recent years, a novel PEDOT:PSS/n-Si planar heterojunction solar cell has been extensively studied in the photovoltaic field. Different V2O5-IPA concentrations mixed in PEDOT:PSS samples as hole transport layer were prepared by means of spin coating technique and mechanical mixing of organic and inorganic materials. V2O5 was studied for its effects on the surface morphology, chemical composition, and optical transmittance of PEDOT:PSS films. The findings of the study show that the addition of V2O5 particles changes the surface morphology of PEDOT:PSS films and promotes its superior ohmic contact with the Si interface. Furthermore, PEDOT:PSS incorporated with V2O5 particles that have outstanding optical and semiconductor properties reduces the rate of carrier recombination at the device interface and blocks electron transport to the anode in the fabricated Si-based solar cells. When compared to conventional PEDOT:PSS/Si planar heterojunction solar cells, the fill factor, photoelectric conversion efficiency, open-circuit voltage, and short-circuit current density of the devices prepared in this study can be significantly improved, reaching up to 70.98%, 15.17%, 652 mV and 32.8 mA/cm2, respectively. This research provides a promising and effective method for improving the photoelectric conversion performance of PEDOT:PSS/Si heterojunction solar cells, which enables the application of V2O5 in Si solar cells.

(Invited) Toward Nanocarbon Materials-Based Organic and Perovskite Solar Cells

In this presentation, we introduce our recent research progress on organic and perovskite solar cells using functionalized nanocarbon materials. We applied wet-processed scalable single-walled carbon nanotubes (SWCNT) films to transparent and back electrodes in organic solar cells for large area solar cells. Gas-phase growth SWCNT was dispersed with sodium dodecylbenzenesulfonate surfactant in an organic solvent and solution-coated on a treated glass substrate to make a SWCNT film as a transparent electrode. We achieved the first high efficiency e-DIPS/wet-processed SWCNT film electrode in organic solar cells with a best-efficiency of 5.93% through the optimized HNO3 doping methodology.We also report 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. The power conversion efficiency of the CNG-coated PEDOT:PSS-applied OSC reaches 2.76% using poly(3-hexylthiophene), which is an increase of 40% compared to that of the pristine PEDOT:PSS-applied OSC (1.96%). This technology improved the efficiency of organic solar cells using a low-bandgap polymer from 6.54% to 7.79%. The significantly enhanced performance is contributed by the increased hole-transporting ability, and the improved interfacial morphology of PEDOT:PSS.

Investigation of the one-step electrochemical deposition of graphene oxide-doped poly(3,4-ethylenedioxythiophene)-polyphenol oxidase as a dopamine sensor.

In this paper, we fabricated poly(3,4-ethylenedioxythiophene) (PEDOT)–graphene oxide–polyphenol oxidase (PEDOT–GO–PPO) as a dopamine sensor. The morphology of PEDOT–GO–PPO was observed using scanning electron microscopy. Cyclic voltammetry was conducted to study the oxidation–reduction characteristics of dopamine. To optimize the pH, potential and limit of detection of dopamine, the amperometric technique was employed. The found limit of detection was 8 × 10−9 M, and the linear range was from 5 × 10−8 to 8.5 × 10−5 M. The Michaelis–Menten constant (Km) was calculated to be 70.34 μM, and the activation energy of the prepared electrode was 32.75 kJ mol−1. The electrode shows no significant change in the interference study. The modified electrode retains up to 80% of its original activity after 2 months. In the future, the biosensor can be used for the quantification of dopamine in human urine samples. The present modified electrode constitutes a tool for the electrochemical analysis of dopamine.

Influence of the molecular weight and size distribution of PSS on mixed ionic-electronic transport in PEDOT:PSS.

The commercially available polyelectrolyte complex poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is ubiquitous in organic and hybrid electronics. As such, it has often been used as a benchmark material for fundamental studies and the development of new electronic devices. Yet, most studies on PEDOT:PSS have focused on its electronic conductivity in dry environments, with less consideration given to its ion transport, coupled ionic-electronic transport, and charge storage properties in aqueous environments. These properties are essential for applications in bioelectronics (sensors, actuators), charge storage devices, and electrochromic displays. Importantly, past studies on mixed ionic-electronic transport in PEDOT:PSS neglected to consider how the molecular structure of PSS affects mixed ionic-electronic transport. Herein, we therefore investigated the effect of the molecular weight and size distribution of PSS on the electronic properties and morphology of PEDOT:PSS both in dry and aqueous environments, and overall performance in organic electrochemical transistors (OECTs). Using reversible addition-fragmentation chain transfer (RAFT) polymerization with two different chain transfer agents, six PSS samples with monomodal, narrow (Đ = 1.1) and broad (Đ = 1.7) size distributions and varying molecular weights were synthesized and used as matrices for PEDOT. We found that using higher molecular weight of PSS (M n = 145 kg mol-1) and broad dispersity led to OECTs with the highest transconductance (up to 16 mS) and [μC * ] values (~140 F·cm-1V-1s-1) in PEDOT:PSS, despite having a lower volumetric capacitance (C * = 35 ± 4 F cm-3). The differences were best explained by studying the microstructure of the films by atomic force microscopy (AFM). We found that heterogeneities in the PEDOT:PSS films (interconnected and large PEDOT- and PSS-rich domains) obtained from high molecular weight and high dispersity PSS led to higher charge mobility (μ OECT ~ 4 cm2V-1s-1) and hence transconductance. These studies highlight the importance of considering molecular weight and size distribution in organic mixed ionic-electronic conductor, and could pave the way to designing high performance organic electronics for biological interfaces.

Controlling the Morphology of PEDOT:PSS Blend Films with Pre-Deposition Solution Composition and Deposition Technique

Controlling the Morphology of PEDOT:PSS Blend Films with Pre-Deposition Solution Composition and Deposition Technique

PEDOT:PSS: From conductive polymers to sensors

PEDOT:PSS conductive polymers have received tremendous attention over the last two decades owing to their high conductivity, ease of processing, and biocompatibility. As a flexible versatile material, PEDOT:PSS can be developed into various forms and has had a significant impact on emerging sensing applications. This review covers the development of PEDOT:PSS from material to physical sensors. We focus on the morphology of PEDOT:PSS in the forms of aqueous dispersions, solid films, and hydrogels. Manufacturing processes are summarized, including coating, printing, and lithography, and there is particular emphasis on nanoimprinting lithography that enables the production of PEDOT:PSS nanowires with superior sensing performance. Applications to various physical sensors, for humidity, temperature, pressure, and strain, are demonstrated. Finally, we discuss the challenges and propose new directions for the development of PEDOT:PSS.

Influence of surface structure and morphology of PEDOT: PSS on its optical and electrophysical characteristics

This paper presents the results of a study of the effect of modification of the structure of the PEDOT: PSS polymer with hole conductivity on the optical and electrophysical properties of an organic solar cell. It was found that the modification of a polymer film with ethyl and isopropyl alcohols leads to a change in the morphology and roughness of the film surface. It has been determined that annealing of films in alcohol vapor promotes the formation of more uniform films. It is shown that upon modification of the PEDOT: PSS film in alcohol vapor the absorption spectrum shifts the absorption maximum of PEDOT to the short-wavelength region of the spectrum, the absorption of the aromatic PSS fragment decrease. X-ray phase analysis showed that after surface modification with alcohol vapor, the PEDOT and PSS chains change their structure. It is shown that the structural features of the surface morphology of PEDOT: PSS affect the electrophysical parameters of the films, such as the effective extraction rate and the effective time of flight of charge carriers. It was found that the modification of the surface of the PEDOT: PSS film leads to an improvement in the electrical transport properties of the films.

How Long are Polymer Chains in Poly(3,4-ethylenedioxythiophene):Tosylate Films? An Insight from Molecular Dynamics Simulations.

Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most important conductive polymers utilized in a variety of applications in organic electronics and bioelectronics and energy storage. PEDOT chains are believed to be rather short, but detailed knowledge of their length is missing because of the challenges in its experimental determination due to insolubility of PEDOT films. Here, we report a molecular dynamics (MD) study of in situ oxidative chemical polymerization and simultaneous crystallization of molecularly doped PEDOT focusing on the determination of its chain lengths at different polymerization temperatures. We find the average chain length to be 6, 7, and 11 monomers for 298, 323 and 373 K, respectively. At the same time, the length distribution is rather broad, for example, between 2 and 16 monomer units for T = 323 K. We demonstrate that the limiting factor determining the chain length is the diffusivity of the reactants (PEDOT monomers and oligomers). We also study the polymer film formation during solvent evaporation, and we find that although crystallization starts and proceeds already during the polymerization and doping phases, it mostly occurs during the evaporation phase. Finally, we believe that our results providing the oligomer chain length and polymerization and crystallization mechanisms obtained by means of MD "computational microscopy" provide an important insight into the morphology of PEDOT that cannot be obtained by other means.

Molecular manipulation of PEDOT:PSS for efficient hole transport by incorporation of N-doped carbon quantum dots

Solution-processed poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films have great potential for organic optoelectronic applications due to their high throughput, low cost, and mechanical flexibility. However, the strong acidity and insulating nature of PSS causes a crucial deterioration of device performance. Here, we present an efficient route for addressing the limitations of PSS by molecular manipulation via incorporation of nitrogen-doped carbon quantum dots (N-CQDs) into PEDOT:PSS. The incorporation of N-CQDs significantly reduces resistance, increases work function, modifies the surface energy and smooths the surface morphology of PEDOT:PSS. In our density functional theory (DFT) calculations, inclusion of N-CQDs weakens the electrostatic interaction between PEDOT and PSS, resulting in molecular manipulation of PEDOT:PSS. Compared to conventionally oxidized CQDs (O-CQDs), N-CQDs have better effects in PEDOT:PSS matrices, including π−π stacking with PEDOT and hydrophilic interaction with PSS, which can effectively induce molecular reorientation. The enhancement of charge extraction and charge injection performance of N-CQD-incorporated PEDOT:PSS are demonstrated via organic optoelectronic devices including organic photovoltaics and organic light-emitting diode with significant improvements in power conversion efficiency and quantum efficiency, respectively. Molecular manipulation via the incorporation of N-CQDs holds promise for the development of highly efficient PEDOT:PSS hole-transporting layers in various optoelectronic devices.

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.

Role of Doping Agent Degree of Sulfonation and Casting Solvent on the Electrical Conductivity and Morphology of PEDOT:SPAES Thin Films.

Poly(3,4-ethylenedioxythiophene) (PEDOT) plays a key role in the field of electrically conducting materials, despite its poor solubility and processability. Various molecules and polymers carrying sulfonic groups can be used to enhance PEDOT’s electrical conductivity. Among all, sulfonated polyarylether sulfone (SPAES), prepared via homogenous synthesis with controlled degree of sulfonation (DS), is a very promising PEDOT doping agent. In this work, PEDOT was synthesized via high-concentration solvent-based emulsion polymerization using 1% w/w of SPAES with different DS as dopant. It was found that the PEDOT:SPAESs obtained have improved solubility in the chosen reaction solvents, i.e., N, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone and, for the first time, the role of doping agent, DS and polymerization solvents were investigated analyzing the electrical properties of SPAESs and PEDOT:SPAES samples and studying the different morphology of PEDOT-based thin films. High DS of SPAES, i.e., 2.4 meq R-SO3− g−1 of polymer, proved crucial in enhancing PEDOT’s electrical conductivity. Furthermore, the DMSO capability to favor PEDOT and SPAES chains rearrangement and interaction results in the formation of a polymer film with more homogenous morphology and higher conductivity than the ones prepared from DMAc, DMF, and NMP.

Bottom Contact Metal Oxide Interface Modification Improving the Efficiency of Organic Light Emitting Diodes.

The performance of solution-processed organic light emitting diodes (OLEDs) is often limited by non-uniform contacts. In this work, we introduce Ni-containing solution-processed metal oxide (MO) interfacial layers inserted between indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to improve the bottom electrode contact for OLEDs using the poly(p-phenylene vinylene) (PPV) derivative Super-Yellow (SY) as an emission layer. For ITO/Ni-containing MO/PEDOT:PSS bottom electrode structures we show enhanced wetting properties that result in an improved OLED device efficiency. Best performance is achieved using a Cu-Li co-doped spinel nickel cobaltite [(Cu-Li):NiCo2O4], for which the current efficiency and luminous efficacy of SY OLEDs increased, respectively, by 12% and 11% from the values obtained for standard devices without a Ni-containing MO interface modification between ITO and PEDOT:PSS. The enhanced performance was attributed to the improved morphology of PEDOT:PSS, which consequently increased the hole injection capability of the optimized ITO/(Cu-Li):NiCo2O4/PEDOT:PSS electrode.

Tailoring the Vertical Morphology of Organic Films for Efficient Planar-Si/Organic Hybrid Solar Cells by Facile Nonpolar Solvent Treatment.

The optical and electrical properties of the blending organic film poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) are strongly affected by its morphology, resulting in the performance variation in Si/organic hybrid solar cells. Here, a facile postsolvent treatment is used to tailor the vertical morphology of PEDOT:PSS by introducing a nonpolar solvent. X-ray photoelectron spectroscopy depth-profiling measurements show that the distribution of PEDOT and PSS on the surface of n-type Si can be changed by nonpolar solvent n-hexane (NHX) treatment, where more PSS aggregate at the bottom of the blend film and more PEDOT float up to the top, as compared with the reference sample. As a result, after NHX treatment, the average lifetime of the Si/organic films is increased from 152 μs for untreated samples to 248 μs for NHX-treated ones because of the better passivation effect of PSS on Si. Moreover, the transmission line model measurements indicate that the contact resistance (RC) of PEDOT:PSS film and the Ag electrode is decreased for better charge collection after NHX treatment. Eventually, the best power conversion efficiency (PCE) of 13.78% for NHX-treated planar solar cells is obtained, much higher than the PCE (with best of 12.78%) of reference devices without nonpolar solvent treatment. Our results provide a facile method to tailor the vertical morphology of the PEDOT:PSS in Si/organic hybrid solar cells.

Synergistic effect of poly(3,4-ethylenedioxythiophene), reduced graphene oxide and aluminium oxide) as counter electrode in dye-sensitized solar cell

Abstract A new counter electrode which makes use of reduced graphene oxide (rGO), poly (3,4-ethylenedioxythiophene) (PEDOT) and aluminium oxide (Al2O3) was developed to enhance the performance of dye-sensitized solar cell (DSSC) device in replacing platinum as a counter electrode. PEDOT/rGO-Al2O3 was fabricated through the deposition of rGO/Al2O3 on indium tin oxide (ITO) glass by cyclic voltammetry followed by the deposition of PEDOT via chronoamperometry. The morphology of PEDOT/rGO-Al2O3 showed the combination of the wrinkled paper-like structure of rGO and coral-like morphology of PEDOT with nanoparticles of alumina, which gave the positive synergistic effects of the counter electrode to increase the performance of the DSSC. The electrochemical analyses indicated that PEDOT/rGO-Al2O3 exhibited a good electrocatalytic activity to act as a counter electrode in DSSC compared to PEDOT-rGO, PEDOT and rGO. The PEDOT/rGO-Al2O3 achieved power conversion efficiency (PCE) of 2.15%, which is higher compared to PEDOT-rGO (1.00%), PEDOT (0.69%) and rGO (0.09%).

Synthesis of Solution-Stable PEDOT-Coated Sulfonated Polystyrene Copolymer PEDOT:P(SS-co-St) Particles for All-Organic NIR-Shielding Films

We prepared poly(3,4-ethylenedioxythiophene) (PEDOT)-coated sulfonated polystyrene copolymer particles as efficient heat-shielding agents, which showed strong near-infrared (NIR) absorption, with high solid contents and good solution stability. The poly(styrene sulfonate-co-styrene) (P(SS-co-St)) copolymers were successfully synthesized via radical solution polymerization, and PEDOT-coated P(SS-co-St) (PEDOT:P(SS-co-St)) was synthesized via Fe+-catalyzed oxidative polymerization. PEDOT:P(SS-co-St) was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopies. The particle size and morphology of PEDOT:P(SS-co-St) were examined using transmission electron microscopy, dynamic light scattering, and zeta potential measurements. The maximum NIR-shielding efficiency of the film was 92.0% with 40% transmittance. The high solution stability of PEDOT:P(SS-co-St) make it an ideal candidate for heat-insulating materials that find application in semi-transparent heat-insulator-coated windows.

Insight into the Interfacial Elastic Contact in Stacking Perovskite Solar Cells

AbstractStacking perovskite solar cells (PSCs) are emerging cells with two detached electrodes during fabrication process, in which the crucial step is the intimate mechanical and electronic contact between the laminated parts. The interfacial elastic contact of stacking PSCs with four different p‐type organic semiconductors has been systematically studied. Studies confirm that poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is an elastic interface material with excellent performance. The convex–concave morphology of PEDOT:PSS surface and the interfacial elastic deformation make a contribution to a desirable conductive contact between two electrodes with sufficient contact area, thereby providing a highly reliable connection and efficient charge transport channel between the semi‐cells. Based on conducting polymer PEDOT:PSS, planar‐structured stacking PSCs are fabricated exhibiting power conversion efficiency of 13.49% with 1.0 cm2 area. Connecting electrodes with excellent conductivity and elasticity are also proved to be essential to the flexible assembly and readily detachment.

Computational microscopy study of the granular structure and pH dependence of PEDOT:PSS.

Computational microscopy based on Martini coarse grained molecular dynamics (MD) simulations of a doped conducting polymer poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (best known as PEDOT:PSS) was performed focussing on the formation of the granular structure and PEDOT crystallites, and the effect of pH on the material morphology. The PEDOT:PSS morphology is shown to be sensitive to the initial distribution of PEDOT and PSS in the solution, and the results of the modelling suggest that the experimentally observed granular structure of PEDOT:PSS can be only obtained if the PEDOT/PSS solution is in the dispersive state in the initial crystallization stages. Variation of the pH is demonstrated to strongly affect the morphology of PEDOT:PSS films, altering their structure between granular-type and homogeneous. It also affects the size of crystallites and the relative arrangement of PEDOT and PSS chains. It is shown that the crystallites in PEDOT:PSS are smaller than those in PEDOT with molecular counterions such as PEDOT:tosylate, which is consistent with the available experimental data. The predicted changes of the PEDOT:PSS morphology with variation of the pH can be tested experimentally, and the calculated atomistic picture of PEDOT:PSS films (not accessible by conventional experimental techniques) is instrumental for understanding the material structure and building realistic models of PEDOT:PSS morphology.