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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]

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: 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]