Structurally-driven Enhancement of Thermoelectric Properties within Poly(3,4-ethylenedioxythiophene) thin Films

Organic Thermoelectric Materials for Wearable Electronic Devices

Wearable electronic devices have emerged as a pivotal technology in healthcare and artificial intelligence robots. Among the materials that are employed in wearable electronic devices, organic thermoelectric materials possess great application potential due to their advantages such as flexibility, easy processing ability, no working noise, being self-powered, applicable in a wide range of scenarios, etc. However, compared with classic conductive materials and inorganic thermoelectric materials, the research on organic thermoelectric materials is still insufficient. In order to improve our understanding of the potential of organic thermoelectric materials in wearable electronic devices, this paper reviews the types of organic thermoelectric materials and composites, their assembly strategies, and their potential applications in wearable electronic devices. This review aims to guide new researchers and offer strategic insights into wearable electronic device development.

One-Shot Remote Integration of Macromolecular Synaptic Elements on a Chip for Ultrathin Flexible Neural Network System

The field of biomimetic electronics that mimic synaptic functions has expanded significantly to overcome the limitations of the von Neumann bottleneck. However, the scaling down of the technology has led to an increasingly intricate manufacturing process. To address the issue, this work presents a one-shot integrable electropolymerization (OSIEP) method with remote controllability for the deposition of synaptic elements on a chip by exploiting bipolar electrochemistry. Condensing synthesis, deposition, and patterning into a single fabrication step is achieved by combining alternating-current voltage superimposed on direct-current voltage-bipolar electropolymerization and a specially designed dual source/drain bipolar electrodes. As a result, uniform 6 × 5 arrays of poly(3,4-ethylenedioxythiophene) channels are successfully fabricated on flexible ultrathin parylene substrates in one-shot process. The channels exhibited highly uniform characteristics and are directly used as electrochemical synaptic transistor with synaptic plasticity over 100 s. The synaptic transistors have demonstrated promising performance in an artificial neural network (NN) simulation, achieving a high recognition accuracy of 95.20%. Additionally, the array of synaptic transistor is easily reconfigured to a multi-gate synaptic circuit to implement the principles of operant conditioning. These results provide a compelling fabrication strategy for realizing cost-effective and disposable NN systems with high integration density.

Recent Progress in Conjugated Conducting and Semiconducting Polymers for Energy Devices

Advanced conductors (such as conducting and semiconducting polymers) are vital building blocks for modern technologies and biocompatible devices as faster computing and smaller device sizes are demanded. Conjugated conducting and semiconducting polymers (including poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), polythiophene (PTh), and polypyrrole (PPy)) provide the mechanical flexibility required for the next generation of energy and electronic devices. Electrical conductivity, ionic conductivity, and optoelectronic characteristics of advanced conductors are governed by their texture and constituent nanostructures. Thus, precise textural and nanostructural engineering of advanced conjugated conducting and semiconducting polymers provide an outstanding pathway to facilitate their adoption in various technological applications, including but not limited to energy storage and harvesting devices, flexible optoelectronics, bio-functional materials, and wearable electronics. This review article focuses on the basic interconnection among the nanostructure and the characteristics of conjugated conducting and semiconducting polymers. In addition, the application of conjugated conducting and semiconducting polymers in flexible energy devices and the resulting state-of-the-art device performance will be covered.

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.

Significant Enhancement of Thermoelectric Properties of PTB7 Conducting Polymer by Mixed-Solvent Approach

The thermoelectric properties of poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}), commonly known as PTB7 conducting polymer, were investigated for the first time by Rastegaralam et al. in 2017 [ Crystals 2017, 7, 292]. PTB7 showed higher electrical conductivity or Seebeck coefficient (or even both) and, hence, a higher thermoelectric power factor than a variety of organic semiconductors. Therefore, it is worth working more on this semiconductor to improve its thermoelectric figure of merit. In this work, for the first time the effect of cosolvents on the thermoelectric properties of PTB7 is investigated. PTB7 conducting polymer dissolved in chlorobenzene was treated with different solvents: N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetonitrile (AC), and 1,2-dichloroethane (DCE). Upon addition of DMF, DMSO, and NMP, a significant enhancement in the electrical conductivity of the samples accompanied by a reduction in the Seebeck coefficient occurred as a result of doping, while the use of AC and DCE led to simultaneous enhancement in the electrical conductivity and the Seebeck coefficient by increasing the mobility. The dopants used in this work are inexpensive, are easily available, and do not need to perform any synthesis process. The highest estimated figure of merit value obtained in this work without optimization is 0.1, which is of the highest values for organic thermoelectric materials.

Oxidative MLD of Conductive PEDOT Thin Films with EDOT and ReCl5 as Precursors

Because of its high conductivity and intrinsic stability, poly(3,4-ethylenedioxythiophene (PEDOT) has gained great attention both in academic research and industry over the years. In this study, we used the oxidative molecular layer deposition (oMLD) technique to deposit PEDOT from 3,4-ethylenedioxythiophene (EDOT) and a new inorganic oxidizing agent, rhenium pentachloride (ReCl5). We extensively characterized the properties of the films by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Raman, and conductivity measurements. The oMLD of polymers is based on the sequential adsorption of the monomer and its oxidation-induced polymerization. However, oMLD has been scarcely used because of the challenge of finding a suitable combination of volatile, reactive, and stable organic monomers applicable at high temperatures. ReCl5 showed promising properties in oMLD because it has high thermal stability and high oxidizing ability for EDOT. PEDOT films were deposited at temperatures of 125-200 °C. EDS and XPS measurements showed that the as-deposited films contained residues of rhenium and chlorine, which could be removed by rinsing the films with deionized water. The polymer films were transparent in the visible region and showed relatively high electrical conductivities within the 2-2000 S cm-1 range.

Printable and Semitransparent Nonfullerene Organic Solar Modules over 30 cm2 Introducing an Energy-Level Controllable Hole Transport Layer

For the commercialization of organic solar cells (OSCs), the fabrication of large-area modules via a solution process is important. The fabrication of OSCs via a solution process using a nonfullerene acceptor (NFA)-based photoactive layer is limited by the energetic mismatch and carrier recombination, reducing built-in potential and effective carriers. Herein, for the fabrication of high-performance NFA-based large-area OSCs and modules via a solution process, hybrid hole transport layers (h-HTLs) incorporating WO₃ and MoO₃ are developed. The high bond energies and electronegativities of W and Mo atoms afford changes in the electronic properties of the h-HTLs, which can allow easy control of the energy levels. The h-HTLs show matching energy levels that are suitable for both deep and low-lying highest occupied molecular orbital energy level systems with a stoichiometrically small amount of oxygen vacancies (forming W⁶⁺ and Mo⁶⁺ from the W⁵⁺ and Mo⁵⁺), affording high conductivity and good film forming properties. With the NFA-based photoactive layer, a large-area module fabricated via the all-printing process with an active area over 30 cm² and a high power conversion efficiency (PCE) of 8.1% is obtained. Furthermore, with the h-HTL, the fabricated semitransparent module exhibits 7.2% of PCE and 22.3% of average visible transmittance with high transparency, indicating applicable various industrial potentials.

Boosting the performance of printed thermoelectric materials by inducing morphological anisotropy

Thermoelectrics can generate electrical energy from waste heat and work also as active coolers. However, their widespread use is hindered by their poor efficiency, which is aggravated by their costly and hard-to-scale fabrication process. Good thermoelectric performances require materials with high (low) electrical (thermal) conductivity. Inducing morphological anisotropy at the nanoscale holds promise to boost thermoelectric performances, in both inorganic and organic materials, by increasing the ratio electrical/thermal conductivity along a selected direction without strongly affecting the Seebeck coefficient. Recent advances in 2D/3D printed electronics are revealing new simple and inexpensive routes to fabricate thermoelectrics with the necessary morphological control to boost performance by inducing anisotropy.

A simple electrochemical approach to fabricate functionalized MWCNT-nanogold decorated PEDOT nanohybrid for simultaneous quantification of uric acid, xanthine and hypoxanthine

Medical diagnostics and detection of food spoilage require estimation of hypoxanthine (HX), xanthine (XN), and uric acid (UA). A selective sensing platform has been proposed for simultaneous detection of all these species. Functionalized multi-walled carbon nanotube (fMWCNT) stabilized nanogold decorated PEDOT:TOS polymeric nanocomposite (Au-PEDOT-fMWCNT) was synthesized through rapid one-step electropolymerization to enhance conductivity and active surface area by several folds. Electrochemical activities of the proposed sensing platform were analyzed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS). Analyses through SEM, FESEM and TEM were performed to explore the surface morphology and elemental analysis of the polymeric nanohybrid was investigated by XPS, Raman, FTIR, XRD spectroscopy. Electro-catalysis of UA, XN and HX occurred at low oxidation potentials i.e. 0.082, 0.463 and 0.808 V, respectively in the optimized conditions. The uniquely designed simple, interference free Au-PEDOT-fMWCNT/GCE sensor exhibited high selectivity, good reproducibility, reusability (∼180 times) and stability (∼3 month) with excellent sensitivity of 1.73, 14.31 and 3.82 μA μM^-1 cm^-2 for UA, XN and HX, respectively. The sensor exhibited linear ranges of detection as 0.1-800, 0.05-175 and 0.1-150 μM with detection limits of 199.3, 24.1 and 90.5 nM for quantification of UA, XN and HX respectively. The performance of the proposed sensor was validated by addition of UA, XN and HX in human serum, urine and fish samples by comparing to those using HPLC. The results indicated good applicability of the proposed sensor for simultaneous detection of UA, XN, HX in real biological fluids.

Structural Control of Charge Storage Capacity to Achieve 100% Doping in Vapor Phase-Polymerized PEDOT/Tosylate

Vapor phase polymerization (VPP) is used to fabricate a series of tosylate-doped poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes on carbon paper. The series of VPP PEDOT/tosylate coatings has varying levels of crystallinity and electrical conductivity because of the use (or not) of nonionic triblock copolymers in the oxidant solution during synthesis. As a result, the impact of the structure on charge storage capacity is investigated using tetra-n-butylammonium hexafluorophosphate (0.1 M in acetonitrile). The ability to insert anions, and hence store charge, of the VPP PEDOT/tosylate is inversely related to its electrical conductivity. In the case of no nonionic triblock copolymer employed, the VPP PEDOT/tosylate achieves electrochemical doping levels of 1.0 charge per monomer or greater (≥100% doping level). Such high doping levels are demonstrated to be plausible by molecular dynamics simulations and density functional theory calculations. Experiments show that this high doping level is attainable when the PEDOT structure is weakly crystalline with (relatively) large crystallite domains.

The intrinsic volumetric capacitance of conducting polymers: pseudo-capacitors or double-layer supercapacitors?

The capacitance of conducting polymers represents one of the most important material parameters that in many cases determines the device and material performances. Despite a vast number of experimental studies, the theoretical understanding of the origin of the capacitance in conducting polymers remains unsatisfactory and appears even controversial. Here, we present a theoretical method, based on first principle capacitance calculations using density functional theory (DFT), and apply it to calculate the volumetric capacitance of two archetypical conducting polymers: poly(3,4-ethylene dioxythiophene) (PEDOT) and polypyrrole (PPy). Our aim is to achieve a quantitate description of the volumetric capacitance and to provide a qualitative understanding of its nature at the atomistic level. We find that the volumetric capacitance of PEDOT and PPy is ≈100 F cm-3 and ≈300 F cm-3, respectively, which is within the range of the corresponding reported experimental results. We demonstrate that the capacitance of conducting polymers originates from charges stored in atomistic Stern layers formed by counterions and doped polymeric chains. The Stern layers have a purely electrostatic origin, since the counterions do not form any bonds with the atoms of the polymeric chains, and no charge transfer between the counterions and conducting polymer takes place. This classifies the conducting polymers as double-layer supercapacitors rather than pseudo-capacitors. Further, we analyze contributions to the total capacitance originating from the classical capacitance C C and the quantum capacitance C Q, respectively, and find that the latter provides a dominant contribution. The method of calculations of the capacitance developed in the present paper is rather general and opens up the way for engineering and optimizing the capacitive response of the conducting polymers.

Flexible Organic Thermoelectric Materials and Devices for Wearable Green Energy Harvesting

In the past few decades, organic thermoelectric materials/devices, which can exhibit remarkable potential in green energy conversion, have drawn great attention and interest due to their easy processing, light weight, intrinsically low thermal conductivity, and mechanical flexibility. Compared to traditional batteries, thermoelectric materials have high prospects as alternative power generators for harvesting green energy. Although crystalline inorganic semiconductors have dominated the fields of thermoelectric materials up to now, their practical applications are limited by their intrinsic fragility and high toxicity. The integration of organic polymers with inorganic nanoparticles has been widely employed to tailor the thermoelectric performance of polymers, which not only can combine the advantages of both components but also display interesting transport phenomena between organic polymers and inorganic nanoparticles. In this review, parameters affecting the thermoelectric properties of materials were briefly introduced. Some recently developed n-type and p-type thermoelectric films and related devices were illustrated along with their thermoelectric performance, methods of preparation, and future applications. This review will help beginners to quickly understand and master basic knowledge of thermoelectric materials, thus inspiring them to design and develop more efficient thermoelectric devices.

Recent Advances in Organic Thermoelectric Materials: Principle Mechanisms and Emerging Carbon-Based Green Energy Materials

Thermoelectric devices have recently attracted considerable interest owing to their unique ability of converting heat to electrical energy in an environmentally efficient manner. These devices are promising as alternative power generators for harvesting electrical energy compared to conventional batteries. Inorganic crystalline semiconductors have dominated the thermoelectric material fields; however, their application has been restricted by their intrinsic high toxicity, fragility, and high cost. In contrast, organic thermoelectric materials with low cost, low thermal conductivity, easy processing, and good flexibility are more suitable for fabricating thermoelectric devices. In this review, we briefly introduce the parameters affecting the thermoelectric performance and summarize the most recently developed carbon-material-based organic thermoelectric composites along with their preparation technologies, thermoelectric performance, and future applications. In addition, the p- and n-type carbon nanotube conversion and existing challenges are discussed. This review can help researchers in elucidating the recent studies on carbon-based organic thermoelectric materials, thus inspiring them to develop more efficient thermoelectric devices.

Quantifying multiple crystallite orientations and crystal heterogeneities in complex thin film materials

Using the mosaicity factor and GIWAXS diffraction patterns to quantify crystallite heterogeneities and orientation in thin film materials.

Thermoelectric materials and applications for energy harvesting power generation

Thermoelectrics, in particular solid-state conversion of heat to electricity, is expected to be a key energy harvesting technology to power ubiquitous sensors and wearable devices in the future. A comprehensive review is given on the principles and advances in the development of thermoelectric materials suitable for energy harvesting power generation, ranging from organic and hybrid organic-inorganic to inorganic materials. Examples of design and applications are also presented.

Substrate-Dependent Morphology and Its Effect on Electrical Mobility of Doped Poly(3,4-ethylenedioxythiophene) (PEDOT) Thin Films

Deposition dynamics, crystallization, molecular packing, and electronic mobility of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films are affected by the nature of the substrate. Computational microscopy has been carried out to reveal the morphology-substrate dependence for PEDOT thin films doped with molecular tosylate deposited on different substrates including graphite, Si₃N₄, silicon, and amorphous SiO₂. It is shown that the substrate is instrumental in formation of the lamellar structure. PEDOT films on the ordered substrates (graphite, Si₃N₄, and silicon) exhibit preferential face-on orientation, with graphite showing the most ordered and pronounced face-on packing. In contrast, PEDOT on amorphous SiO₂ exhibits the dominant edge-on orientation, except in the dry state where both packings are equally presented. The role of water and the porosity of the substrate in formation of the edge-on structure on SiO₂ is outlined. On the basis of the calculated morphology, the multiscale calculations of the electronic transport and percolative analysis are performed outlining how the character of the substrate affects the electron mobility. It is demonstrated that good crystallinity (PEDOT on graphite substrate) and high content of edge-on (PEDOT on SiO₂ substrate) are not enough to achieve the highest electrical in-plane mobility. Instead, the least ordered material with lower degree of the edge-on content (PEDOT on silicon substrate) provides the highest mobility because it exhibits an efficient network of π-π stacked chain extending throughout the entire sample.

Isomeric cationic ionenes as n-dopant agents of poly(3,4-ethylenedioxythiophene) for in situ gelation

Three isomeric ionene polymers containing 1,4-diazabicyclo[2.2.2]octane (DABCO) and N,N'-(x-phenylene)dibenzamide (x = ortho-/meta-/para-) linkages have been used as dopant agents to produce n-doped poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes by reducing already dedoped conducting polymer (CP) films. This work focuses on the influence of the ionene topology on both the properties of n-doped PEDOT:ionene electrodes and the success of the in situ thermal gelation of the ionene inside the CP matrix. The highest doping level is reached for the para-isomeric ionene-containing electrode, even though the content of ortho- and meta-topomers in the corresponding n-doped PEDOT:ionene electrodes is greater. Thus, many of the incorporated ionene units are not directly interacting with CP chains and, therefore, they do not play an active role as n-dopant agents but they are crucial for the in situ formation of the ionene hydrogels. The effect of the ionene topology is practically non-existent on properties such as the specific capacitance and wettability of PEDOT:ionene films, and it is small but non-negligible on the electrochemical and thermal stability. In contrast, the surface morphology, topography, and distribution of dopant molecules significantly depend on the ionene topology. In situ thermal gelation was successful in PEDOT films n-doped with the ortho- and para-topomers, even though this assembly process was much faster for the former than for the latter. The gelation considerably improved the mechanical response of the electropolymerized PEDOT film, which was practically non-existent before it. Molecular dynamics simulations prove that the strength and abundance of PEDOTionene specific interactions (i.e. π-π stacking, N-HS hydrogen bonds and both N+O and N+S interactions) are higher for the meta-isomeric ionene, for which the in situ gelation was not achieved, than for the ortho- and para-ones.

Solvent Additives: Key Morphology-Directing Agents for Solution-Processed Organic Solar Cells

Organic photovoltaics (OPV) have the advantage of possible fabrication by energy-efficient and cost-effective deposition methods, such as solution processing. Solvent additives can provide fine control of the active layer morphology of OPVs by influencing film formation during solution processing. As such, solvent additives form a versatile method of experimental control for improving organic solar cell device performance. This review provides a brief history of solution-processed bulk heterojunction OPVs and the advent of solvent additives, putting them into context with other methods available for morphology control. It presents the current understanding of how solvent additives impact various mechanisms of phase separation, enabled by recent advances in in situ morphology characterization. Indeed, understanding solvent additives' effects on film formation has allowed them to be applied and combined effectively and synergistically to boost OPV performance. Their success as a morphology control strategy has also prompted the use of solvent additives in related organic semiconductor technologies. Finally, the role of solvent additives in the development of next-generation OPV active layers is discussed. Despite concerns over their environmental toxicity and role in device instability, solvent additives remain relevant morphological directing agents as research interests evolve toward nonfullerene acceptors, ternary blends, and environmentally sustainable solvents.

Imidazolium Iodide-Doped PEDOT Nanofibers as Conductive Catalysts for Highly Efficient Solid-State Dye-Sensitized Solar Cells Employing Polymer Electrolyte

The electrical conductivity and catalytic activity of nanofibrous poly(3,4-ethylenedioxythiophene)s (PEDOT NFs) was improved by redoping with dimethyl imidazolium iodide (DMII) as a charge transfer facilitator. Addition of the new DMII dopant into the PEDOT NFs reduced the concentration of dodecyl sulfate anions (DS^-) predoped during the polymerization process and concomitantly enhanced the doping concentration of I^- by ion exchange. Redoping with DMII increased the mobility of the PEDOT NFs by up to 18-fold and improved the conductivity due to the enhanced linearization, suppressed aggregation, and improved crystallinity of the PEDOT chains. The catalytic activity was also improved, primarily due to the increase in the compatibility and the effective surface area upon replacement of sticky DS^- with the more basic and smaller I^- of DMII on the surface of the PEDOT NFs. The charge-transfer resistance across the interface between the poly(ethylene oxide)-based solid polymer electrolyte and PEDOT NF counter electrode (CE) was thus reduced to a large extent, giving an energy conversion efficiency (ECE) of 8.52% for solid-state dye-sensitized solar cells (DSCs), which is even better than that achieved with Pt CE (8.25%). This is the highest ECE reported for solid-state DSCs with conductive polymer CEs under 1 sun conditions.

Morphology of a self-doped conducting oligomer for green energy applications

A recently synthesized self-doped conducting oligomer, salt of bis[3,4-ethylenedioxythiophene]3thiophene butyric acid, ETE-S, is a novel promising material for green energy applications. Recently, it has been demonstrated that it can polymerize in vivo, in plant systems, leading to a formation of long-range conducting wires, charge storage and supercapacitive behaviour of living plants. Here we investigate the morphology of ETE-S combining the experimental characterisation using Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) and atomistic molecular dynamics (MD) simulations. The GIWAXS measurements reveal a formation of small crystallites consisting of π-π stacked oligomers (with the staking distance 3.5 Å) that are further organized in h00 lamellae. These experimental results are confirmed by MD calculations, where we calculated the X-ray diffraction pattern and the radial distribution function for the distance between ETE-S chains. Our MD simulations also demonstrate the formation of the percolative paths for charge carriers that extend throughout the whole structure, despite the fact that the oligomers are short (6-9 rings) and crystallites are thin along the π-π stacking direction, consisting of only two or three π-π stacked oligomers. The existence of the percolative paths explains the previously observed high conductivity in in vivo polymerized ETE-S. We also explored the geometrical conformation of ETE-S oligomers and the bending of their aliphatic chains as a function of the oligomer lengths.

Insights on the Optical Properties of Poly(3,4-Ethylenedioxythiophene):Poly(styrenesulfonate) Formulations by Optical Metrology

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is among the most widely used polymers that are used as printed transparent electrodes for flexible Organic Electronic (OE) devices, such as Organic Photovoltaics (OPVs). The understanding of their optical properties and the correlation of the optical properties with their electronic properties and metallic-like behavior can lead to the optimization of their functionality as transparent electrodes in multilayer OE device architectures. In this work, we study the optical properties of different PEDOT:PSS formulations by non-destructive Spectroscopic Ellipsometry (SE), from the infrared to the far ultraviolet spectral regions. The optical response of PEDOT:PSS includes an intense optical absorption originated from the conductive part (PEDOT) at lower photon energies, whereas the electronic transition energies of the non-conductive PSS part have been measured at higher photon energies. Based on the different PEDOT:PSS formulations, the optical investigation revealed significant information on the relative contribution of conductive PEDOT and insulating PSS parts of the PEDOT:PSS formulation in the overall optical response, which can strongly impact the final device functionality and its optical transparency.

All-Polymeric Flexible Transparent Heaters

All-polymeric flexible transparent heaters (THs) are demonstrated for the first time. Thin films of four poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials embedding different dopants exhibit low sheet resistances, down to 57 Ω sq^-1 associated with good transparencies (>87%) and a haze lower than 1%. These transparent thin films show excellent heating properties, with high heating rates (up to 1.6 °C s^-1) and steady-state temperatures exceeding 100 °C when subjected to 12 V bias. Very high areal power densities were also measured, reaching almost 10 000 W m^-2. The temperature increase is finely fitted to a thermal model. It is further demonstrated that these new THs can be efficiently integrated for applications in thermochromic displays and visor deicers.

Highly Ordered Nanoconfinement Effect from Evaporation-Induced Self-Assembly of Block Copolymers on In Situ Polymerized PEDOT:Tos

Organic thermoelectric materials based on conducting polymers have focused on increasing electrical conductivity and optimizing thermoelectric properties via dedoping processes. To control the crystallinity and crystal alignment for enhanced electrical conductivity, a confinement geometry in nanostructures with grapho-epitaxial growth of conducting polymers during in situ polymerization could be a promising approach. We obtained highly ordered lamellar, cylindrical and disordered nanostructures from PEO-b-PPO-b-PEO block copolymer (BCP) and iron(III) tosylate (Fe(Tos)₃) oxidant blended films and solvent evaporation-induced self-assembly (EISA) processes. Then, in situ vapor phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT):Tos on differently ordered oxidant/BCP films was performed. The effect of BCP nanostructures on the crystallinity, crystal orientation and electrical conductivity of the PEDOTs was confirmed by nanostructural and crystallographic analyses using grazing incidence small and wide-angle X-ray scattering (GISAXS and GIWAXS, respectively) experiments before and after polymerization and after a washing process. Different washing solvents also affected the electrical conductance and crystal structure. We achieved thermoelectric thermopowers up to 70 μW·m^-1·K^-2 by using an immersion dedoping process to reduce the carrier concentration and enhance the Seebeck coefficient, with little change of crystal structure.