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Discusses the use of infrared reflection-absorption spectroscopy to characterize thin overlayers of D[sub 2]O ice deposited in UHV onto a set of self-assembled alkanethiolate monolayers of controlled wettabilities on gold. Experimental spectra and effect of annealing of thin ice overlayers.

Printed electronic paper identifies its interest in flexible organic electronics and sustainable and clean energy applications because of its straightforward production method, cost‐effectiveness, and positive environmental impact. However, current limitations include restricted material thickness and the use of supporting substrate for printing. Here, 2D and 3D electronic patterned paper are fabricated from direct ink writing (DIW) nanocellulose and PEDOT:PSS‐based materials using syringe deposition and 3D printing. The conductor patterns are integrated in the bulk of the paper, while non‐conductive sections are used as support to form free‐standing paper. The strong interface between the patterns of electronic patterned paper gives mechanical stability for practical handling. The conductive paper‐based electrode has 202 S cm−1 and is capable of handling electric current up to 0.7 A, which can be used for high‐power devices. Printed supercapacitor papers show high specific energy of 4.05 Wh kg−1, specific power of 4615 W kg−1 at 0.06 A g−1, and capacitance retention above 95% after 2000 cycles. The new design structure of electronic patterned papers presents a solution for additive manufacturing of paper‐based composites for supercapacitors, wearable electronics, or sensors for smart packaging. [ABSTRACT FROM AUTHOR]

Organic light-emitting electrochemical cells (LEC) are promising for lighting applications but in many cases these devices suffer from unbalanced electrochemical doping, which cause instability and degradation of the cells. A predominant p-doping over n-doping causes an off-centered emissive p–n junction, which leads to poor power-conversion efficiency. Here, we report a half-gate LEC transistor (HG-LECT), in which an ion-conductive gate made from poly(3,4-ethylenedioxythiophene)-poly-(styrenesulfonate) is employed to combat this instability problem. The gate material, covering half of the channel, is used to enhance the n-doping process in this part by employing an appropriate operation protocol. We demonstrate a centered light emission zone, closely following the geometry of the gate configuration. The HG-LECT with centered emission profile is shown to be more efficient than the corresponding LEC without the gate electrode, and its n-doping level is measured to be 15%. [ABSTRACT FROM AUTHOR]

In conventional light-emitting electrochemical cells (LECs), an off-centered p–n junction is one of the major drawbacks, as it leads to exciton quenching at one of the charge-injecting electrodes and results in performance instability. To combat this problem, we have developed a new device configuration, the double-gate light-emitting electrochemical transistor (DG-LECT), in which the location of the light-emitting p–n junction can be precisely defined via the position of the two gate terminals. Based on a planar LEC structure, two gate electrodes made from an electrochemically active conducting polymer are employed to predefine the p- and n-doped area of the light-emitting polymer. Thus, a p–n junction is formed in between the p-doped and n-doped regions. We demonstrate a homogeneous and centered p–n junction as well as other predefined junction patterns in these DG-LECT devices. Additionally, we report an electrical model that explains the operation of the DG-LECTs. The DG-LECT device provides a new tool to study the fundamental physics of LECs, as it dissects the key working process of LEC into decoupled p-doping, n-doping, and electroluminescence. [ABSTRACT FROM AUTHOR]

Low-voltage-operating organic electrochemical light-emitting cells (LECs) and transistors (OECTs) can be realized in robust device architectures, thus enabling easy manufacturing of light sources using printing tools. In an LEC, the p-n junction, located within the organic semiconductor channel, constitutes the active light-emitting element. It is established and fixated through electrochemical p- and n-doping, which are governed by charge injection from the anode and cathode, respectively. In an OECT, the electrochemical doping level along the organic semiconducting channel is controlled via the gate electrode. Here we report the merger of these two devices: the light-emitting electrochemical transistor, in which the location of the emitting p-n junction and the current level between the anode and cathode are modulated via a gate electrode. Light emission occurs at 4 V, and the emission zone can be repeatedly moved back and forth within an interelectrode gap of 500 μm by application of a 4 V gate bias. In transistor operation, the estimated on/off ratio ranges from 10 to 100 with a gate threshold voltage of -2.3 V and transconductance value between 1.4 and 3 μS. This device structure opens for new experiments tunable light sources and LECs with added electronic functionality. [ABSTRACT FROM AUTHOR]

Abstract: An electrochemical circuit to record time–temperature history has been realized by using the propagation of over-oxidation fronts in stripes of poly(3,4-ethylenedioxythiopehene) blended with poly(styrenesulfonate) (PEDOT:PSS). The over-oxidation front propagation has been characterized and related to the phase change of polyethylene glycol (PEG) electrolytes. The electrolytes were chosen to have a phase transition in the temperature interval to be monitored, resulting in large conductivity variations and thereby an easily interpreted output. A demonstrator has been fabricated and shown to detect a temperature increase and a following temperature decrease. This very simple device is cheap to produce and could be used to monitor the temperature of packages. [ABSTRACT FROM AUTHOR]

The nature of mass transport in plants has recently inspired the development of low-cost and sustainable wood-based electronics. Herein, we report a wood electrochemical transistor (WECT) where all three electrodes are fully made of conductive wood (CW). The CW is prepared using a two-step strategy of wood delignification followed by wood amalgamation with a mixed electron-ion conducting polymer, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS). The modified wood has an electrical conductivity of up to 69 Sm-1 induced by the formation of PEDOT:PSS microstructures inside the wood 3D scaffold. CW is then used to fabricate the WECT, which is capable of modulating an electrical current in a porous and thick transistor channel (1 mm) with an on/off ratio of 50. The device shows a good response to gate voltage modulation and exhibits dynamic switching properties similar to those of an organic electrochemical transistor. This wood-based device and the proposed working principle demonstrate the possibility to incorporate active electronic functionality into the wood, suggesting different types of bio-based electronic devices. [ABSTRACT FROM AUTHOR]

The need for achieving sustainable technologies has encouraged research on renewable and biodegradable materials for novel products that are clean, green, and environmentally friendly. Nanocellulose (NC) has many attractive properties such as high mechanical strength and flexibility, large specific surface area, in addition to possessing good wet stability and resistance to tough chemical environments. NC has also been shown to easily integrate with other materials to form composites. By combining it with conductive and electroactive materials, many of the advantageous properties of NC can be transferred to the resulting composites. Conductive polymers, in particular poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate) (PEDOT:PSS), have been successfully combined with cellulose derivatives where suspensions of NC particles and colloids of PEDOT:PSS are made to interact at a molecular level. Alternatively, different polymerization techniques have been used to coat the cellulose fibrils. When processed in liquid form, the resulting mixture can be used as a conductive ink. This review outlines the preparation of NC/PEDOT:PSS composites and their fabrication in the form of electronic nanopapers, filaments, and conductive aerogels. We also discuss the molecular interaction between NC and PEDOT:PSS and the factors that affect the bonding properties. Finally, we address their potential applications in energy storage and harvesting, sensors, actuators, and bioelectronics. [ABSTRACT FROM AUTHOR]

Low weight, small footprint, and high performances are essential requisites for the implementation of energy storage devices within consumer electronics. One way to achieve these goals is to increase the thickness of the active material layer. In this work, carbonized and graphitized rayon felt, a cellulose‐derived material, is used as a three‐dimensional current collector scaffold to enable the incorporation of large amount of active energy storage materials and ionic liquid‐based gel electrolyte in the supercapacitor devices. PEDOT:PSS, alone or in combination with active carbon, has been used as the active material. Three‐dimensional supercapacitors with high per unit area capacitance (more than 1.1 F/cm2) have been achieved owing to the loading of large amount of active material in the felt matrix. Areal energy density of more than 101 μWh/cm2 and areal power density of more than 5.9 mW/cm2 have been achieved for 0.8 V operating voltage at a current density of 1 mA/cm2. A nanographite material was found to be beneficial in reducing the internal serial resistance of the supercapacitor to lower than 1.7 Ω. Furthermore, it was shown that even after 2000 times cycling test, the devices could still retain its performance with at least 88% coulombic efficiency for all the devices. All the materials are readily available commercially, environmentally sustainable and the process can potentially be upscaled with industrial process. [ABSTRACT FROM AUTHOR]

Organic electronic circuits based on organic electrochemical transistors (OECTs) are attracting great attention due to their printability, flexibility, and low voltage operation. Inverters are the building blocks of digital logic circuits (e.g., NAND gates) and analog circuits (e.g., amplifiers). However, utilizing OECTs in electronic logic circuits is challenging due to the resulting low voltage gain and low output voltage levels. Hence, inverters capable of operating at relatively low supply voltages, yet offering high voltage gain and larger output voltage windows than the respective input voltage window are desired. Herein, inverters realized from poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate‐based OECTs are designed and explored, resulting in logic inverters exhibiting high voltage gains, enlarged output voltage windows, and tunable switching points. The inverter designs are based on multiple screen‐printed OECTs and a resistor ladder, where one OECT is the driving transistor while one or two additional OECTs are used as variable resistors in the resistor ladder. The inverters' performances are investigated in terms of voltage gain, output voltage levels, and switching point. Inverters, operating at +/−2.5 V supply voltage and an input voltage window of 1 V, that can achieve an output voltage window with ∼110% increment and a voltage gain up to 42 are demonstrated. [ABSTRACT FROM AUTHOR]

Ultrathin devices are rapidly developing for skin‐compatible medical applications and wearable electronics. Powering skin‐interfaced electronics requires thin and lightweight energy storage devices, where solution‐processing enables scalable fabrication. To attain such devices, a sequential deposition is employed to achieve all spray‐coated symmetric microsupercapacitors (μSCs) on ultrathin parylene C substrates, where both electrode and gel electrolyte are based on the cheap and abundant biopolymer, cellulose. The optimized spraying procedure allows an overall device thickness of ≈11 µm to be obtained with a 40% active material volume fraction and a resulting volumetric capacitance of 7 F cm−3. Long‐term operation capability (90% of capacitance retention after 104 cycles) and mechanical robustness are achieved (1000 cycles, capacitance retention of 98%) under extreme bending (rolling) conditions. Finite element analysis is utilized to simulate stresses and strains in real‐sized μSCs under different bending conditions. Moreover, an organic electrochromic display is printed and powered with two serially connected μ‐SCs as an example of a wearable, skin‐integrated, fully organic electronic application. [ABSTRACT FROM AUTHOR]

Low‐voltage operating organic electronic circuits with long‐term stability characteristics are receiving increasing attention because of the growing demands for power efficient electronics in Internet of Things applications. To realize such circuits, inverters, the fundamental constituents of many circuits, with stable transfer characteristics should be designed to provide low‐power consumption. Here, a rational inverter design, based on fully screen printed p‐type organic electrochemical transistors with a channel size of 150 × 80 µm2, is explored for driving conditions with input voltage levels that differs of about 1 V. Further, three different inverter circuits are explored, including resistor ladders with resistor values ranging from tens of kΩ to a few MΩ. The performance of single inverters, 3‐stage cascaded inverters and 3‐stage ring oscillators are characterized with respect to output voltage levels, propagation delay, static power consumption, voltage gain, and operational frequency window. Depending on the application, the key performance parameters of the inverter can be optimized by the specific combination of the input voltage levels and the resistor ladder values. A few of the inverters are in fact fully functional up to 30 Hz, even when using input voltage levels as low as (0 V, 1 V). [ABSTRACT FROM AUTHOR]

Abstract: Poly(3,4-ethylenedioxythiophene) chemically doped with poly(styrene sulfonic acid) (PEDOT:PSS) is a material system commonly used as a conductive and transparent coating in several important electronic applications. The material is also electrochemically active and exhibits electrochromic (EC) properties making it suitable as the active element in EC display applications. In this work uniformly coated PEDOT:PSS layers were used both as the pixel electrode and as the counter electrode in EC display components. The pixel and counter electrodes were separated by a whitish opaque and water-based polyelectrolyte and the thicknesses of the two EC layers were varied independently in order to optimize the color contrast of the display element. A color contrast (ΔE ∗, CIE L ∗ a ∗ b ∗ color space) exceeding 40 was obtained with maintained relatively short switching time at an operational voltage less than 2V. [Copyright &y& Elsevier]

Abstract: Monolithic integration of an organic field-effect transistor (OFET) and an organic electrochromic display cell operating at around 1V is reported. This was achieved by utilising a common patterned layer of poly(styrenesulfonic acid) (PSSH). In the OFET, PSSH served as the electric double layer capacitors between the gate and the organic semiconductor channel. In the electrochromic pixel, PSSH was included as the electrolyte and transports protons from and to the electrochromic layer upon switching. The enhancement mode OFET enables a relatively faster updating speed, of the display cell, and provides a much simpler addressing and updating scheme as compared to smart pixels including a depletion mode electrochemical transistor. [Copyright &y& Elsevier]

Abstract The conductive polymer poly(3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) is widely used in organic electronics and printed electronics due to its excellent electronic and ionic conductivity. PEDOT:PSS films exhibit anisotropic conductivities originating from the interplay of film deposition processes and chemical structure. The previous studies found that high boiling point solvent treated PEDOT:PSS exhibits an anisotropy of 3–4 orders magnitude. Even though both the in-plane and out-of-plane conductivities are important for the device performance, the out-of-plane conductivity is rarely studied due to the complexity with the experiment procedure. Cellulose-based paper or films can also exhibit anisotropic behavior due to the combination of their intrinsic fibric structure and film formation process. We have previously developed a conductive paper based on PEDOT:PSS and cellulose which could be used as the electrodes in energy storage devices. In this work we developed a novel measurement set-up for studying the anisotropy of the charge transport in such composite materials. A tool with two parallel plates mounted with spring loaded probes was constructed enabling probing both lateral and vertical directions and resistances from in-plane and out-of-plane directions to be obtained. The measurement results were then input and analyzed with a model based on a transformation method developed by Montgomery, and thus the in-plane and out-of-plane conductivities could be detangled and derived. We also investigated how the conductivity anisotropy depends on the microstructure of the cellulose template onto which the conductive polymer self-organizes. We show that there is a relatively small difference between the in-plane and out-of-plane conductivities which is attributed to the unique 3D-structure of the composites. This new knowledge gives a better understanding of the possibilities and limitations for using the material in electronic and electrochemical devices. Graphical abstract Image 1 Highlights • Developed a simple to use generic tool for measuring 3-D resistances of thick conducting self-standing films. • The in-plane and out-of-plane conductivities were deduced by a method developed by Montgomery. • Both CNF-PEDOT:PSS and pulp-PEDOT:PSS films exhibit anisotropic conductivity. • CNF-PEDOT:PSS films show thickness independent anisotropic conductivity. • Pulp-PEDOT:PSS became less anisotropic with increasing thicknesses. [ABSTRACT FROM AUTHOR]

Advances in organic electronics necessitates, ultrathin and miniaturized implantable energy storage modules. Here, an approach for the fabrication of on-chip, ultraflexible electrochemical capacitors is demonstrated. Two different electroactive conjugated polymers are utilized in a fabrication route that allows the patterning of finger electrodes for an ultraflexible energy storage technology. A strategy is demonstrated to realize supercapacitors with a total device thickness of 4 μm, including substrate, polymer electrode, and electrolyte. Interdigitated 20-finger electrodes from either Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) or polythiophene functionalized with tetraethylene glycol side chains P(g42T-T), with 50 μm or 90 μm electrode spacings, are fabricated using a parylene peel off method, followed by electrolyte deposition. The miniaturized devices show 0.77 mF/cm2 areal capacitance for PEDOT:PSS and 0.06 mF/cm2 for P(g42T-T). Furthermore, the devices exhibit excellent mechanical durability, showing robust operational performance at a bending radius of 6.5 mm. [Display omitted] • Scalable fabrication route for polymer IDE structures using parylene peel off method. • PEDOT:PSS and P(g42T-T) microsupercapacitors with more than 0.6 mF/cm2 capacitance. • Ultrathin organic electronics device technology with total thickness of 4 μm. • Excellent mechanical durability, showing robust operational performance at a bending radius of 6.5 mm. [ABSTRACT FROM AUTHOR]

Abstract: State‐of‐the‐art solar energy harvesting systems based on photovoltaic technology require constant illumination for optimal operation. However, weather conditions and solar illumination tend to fluctuate. Here, a device is presented that extracts electrical energy from such light fluctuations. The concept combines light‐induced heating of gold nanodisks (acting as plasmonic optical nanoantennas), and an organic pyroelectric copolymer film (poly(vinylidenefluoride‐co‐trifluoroethylene)), that converts temperature changes into electrical signals. This hybrid device can repeatedly generate current pulses, not only upon the onset of illumination, but also when illumination is blocked. Detailed characterization highlights the key role of the polarization state of the copolymer, while the copolymer thickness has minor influence on performance. The results are fully consistent with plasmon‐assisted pyroelectric effects, as corroborated by combined optical and thermal simulations that match the experimental results. Owing to the tunability of plasmonic resonances, the presented concept is compatible with harvesting near infrared light while concurrently maintaining visible transparency. [ABSTRACT FROM AUTHOR]

A novel patterning technique of conductive polymers produced by vapor phase polymerization is demonstrated. The method involves exposing an oxidant film to UV light which changes the local chemical environment of the oxidant and subsequently the polymerization kinetics. This procedure is used to control the conductivity in the conjugated polymer poly(3,4-ethylenedioxythiophene):tosylate by more than six orders of magnitude in addition to producing high-resolution patterns and optical gradients. The mechanism behind the modulation in the polymerization kinetics by UV light irradiation as well as the properties of the resulting polymer are investigated. [ABSTRACT FROM AUTHOR]

Printed electronics are considered for wireless electronic tags and sensors within the future Internet-of-things (loT) concept. As a consequence of the low charge carrier mobility of present printable organic and inorganic semiconductors, the operational frequency of printed rectifiers is not high enough to enable direct communication and powering between mobile phones and printed e-tags. Here, we report an all-printed diode operating up to 1.6 GHz. The device, based on two stacked layers of Si and NbSi2 particles, is manufactured on a flexible substrate at low temperature and in ambient atmosphere. The high charge carrier mobility of the Si microparticles allows device operation to occur in the charge injection-limited regime. The asymmetry of the oxide layers in the resulting device stack leads to rectification of tunneling current. Printed diodes were combined with antennas and electrochromic displays to form an all-printed e-tag. The harvested signal from a Global System for Mobile Communications mobile phone was used to update the display. Our findings demonstrate a new communication pathway for printed electronics within loT applications. [ABSTRACT FROM AUTHOR]

Ion selective membranes are at the heart of energy conversion and harvesting, water treatment, and biotechnologies. The currently available membranes are mostly based on expensive and non-biodegradable polymers. Here, we report a cation-selective and low-cost membrane prepared from renewable nanocellulose and 1,2,3,4-butanetetracarboxylic acid which simultaneously serves as crosslinker and source of anionic surface groups. Charge density and structure of the membranes are studied. By using different degrees of crosslinking, simultaneous control over both the nanochannel structure and surface charge concentration is achieved, which in turn determines the resulting ion transport properties. Increasing negative charge concentration via higher crosslinker content, the obtained ion conductivity reaches up to 8 mS/cm (0.1 M KCl). Optimal ion selectivity, also influenced by the solution pH, is achieved at 20 wt% crosslinker addition (with ion conductivity of 1.6 mS/cm). As regular ~1.4 nm nanochannels were formed at this composition, nanofluidic contribution to ion transport is likely. • A renewable, low cost crosslinked nanocellulose membrane was reported. • The crosslinked membranes show excellent ion conductivity and selectivity. • A higher amount of crosslinker results in a greater ion conductivity. • An optimal ionic selectivity obtained at an addition of the crosslinker of 20 wt%. • This nanocellulose membrane is promising for ionic devices and upscaled applications. [ABSTRACT FROM AUTHOR]

Polyelectrolytes are promising electronicallyinsulating layers for low-voltage organic field effect transistors.However, the polyelectrolyte–semiconductor interface is difficultto manufacture due to challenges in wettability. We introduce an amphiphilicsemiconducting copolymer which, when spread as a thin film, can changeits surface from hydrophobic to hydrophilic upon exposure to water.This peculiar wettability is exploited in the fabrication of polyelectrolyte-gatedfield-effect transistors operating below 0.5 V. The prepared amphiphilicsemiconducting copolymer is based on a hydrophobic regioregular poly(3-hexylthiophene)(P3HT) covalently linked to a hydrophilic poly(sulfonated)-based randomblock. Such a copolymer is obtained in a three-step strategy combiningGrignard metathesis (GRIM), atom transfer radical polymerization (ATRP)processes, and a postmodification method. The structure of the diblockcopolymer was characterized using FT-IR, 1H NMR spectroscopy,and gel permeation chromatography (GPC). [ABSTRACT FROM AUTHOR]

Abstract: We report a method for inkjet-printing an organic semiconductor layer on top of the electrolyte insulator layer in polyelectrolyte-gated OFETs by using a surface modification treatment to overcome the underlying wettability problem at this interface. The method includes depositing an amphiphilic diblock copolymer (P3HT-b-PDMAEMA). This material is designed to have one set of blocks that mimics the hydrophobic properties of the semiconductor (poly(3-hexylthiophene) or P3HT), while the other set of blocks include polar components that improve adhesion to the polyelectrolyte insulator. Contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy confirm formation of the desired surface modification film. Successful inkjet printing of a smooth semiconductor layer allows us to manufacture complete transistor structures that exhibit low-voltage operation in the range of 1V. [Copyright &y& Elsevier]

Abstract: Printed electronics promise various kinds of sensor circuit labels, for applications in distributed sensing and monitoring, which can be manufactured using traditional printing tools at very low cost. Elevated humidity levels or water leakages cause tremendous costs in our society, such as in construction industries and in transportations. Distributed monitoring and remote sensing of the humidity level inside walls of buildings and packages is therefore desired and urgently needed. Here, we report a wireless humidity sensor label that is manufactured using screen-printing and dry-phase patterning. The sensor label includes a planar antenna, a tuning capacitor and a printed sensor-capacitor head. Through electromagnetic coupling between a reader and the printed sensor label, changes in humidity level were remotely detected and read-out as a shift of the resonant frequency. The manufacturing process of the humidity sensor label is fully compatible with inexpensive, reel-to-reel processing technologies, thus enabling low cost production. [Copyright &y& Elsevier]

Electrochromic devices have important implications as smart windows for energy efficient buildings, internet of things devices, and in low-cost advertising applications. While inorganics have so far dominated the market, organic conductive polymers possess certain advantages such as high throughput and low temperature processing, faster switching, and superior optical memory. Here, we present organic electrochromic devices that can switch between two high-resolution images, based on UV-patterning and vapor phase polymerization of poly(3,4-ethylenedioxythiophene) films. We demonstrate that this technique can provide switchable greyscale images through the spatial control of a UV-light dose. The color space was able to be further altered via optimization of the oxidant concentration. Finally, we utilized a UV-patterning technique to produce functional paper with electrochromic patterns deposited on porous paper, allowing for environmentally friendly electrochromic displays. [ABSTRACT FROM AUTHOR]