Printable All‐Organic Electrochromic Active‐Matrix Displays

All‐organic active matrix addressed displays based on electrochemical smart pixels made on flexible substrates are reported. Each individual smart pixel device combines an electrochemical transistor with an electrochromic display cell, thus resulting in a low‐voltage operating and robust display technology. Poly(3,4‐ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) served as the active material in the electrochemical smart pixels, as well as the conducting lines, of the monolithically integrated active‐matrix display. Different active‐matrix display addressing schemes have been investigated and a matrix display fill factor of 65 % was reached. This is achieved by combining a three‐terminal electrochemical transistor with an electrochromic display cell architecture, in which an additional layer of PEDOT:PSS was placed on top of the display cell counter electrode. In addition, we have evaluated different kinds of electrochromic polymer materials aiming at reaching a high color switch contrast. This work has been carried out in the light of achieving a robust display technology that is easily manufactured using a standard label printing press, which forced us to use the fewest different materials as well as avoiding exotic and complex device architectures. Together, this yields a manufacturing process of only five discrete patterning steps, which in turn promise for that the active matrix addressed displays can be manufactured on paper or plastic substrates in a roll‐to‐roll production procedure.     

Reconfigurable sticker label electronics manufactured from nanofibrillated cellulose-based self-adhesive organic electronic materials

Low voltage operated electrochemical devices can be produced from electrically conducting polymers and polyelectrolytes. Here, we report how such polymers and polyelectrolytes can be cast together with nanofibrillated cellulose (NFC) derived from wood. The resulting films, which carry ionic or electronic functionalities, are all-organic, disposable, light-weight, flexible, self-adhesive, elastic and self-supporting. The mechanical and self-adhesive properties of the films enable simple and flexible electronic systems by assembling the films into various kinds of components using a “cut and stick” method. Additionally, the self-adhesive surfaces provide a new concept that not only allows for simplified system integration of printed electronic components, but also allows for a unique possibility to detach and reconfigure one or several subcomponents by a “peel and stick” method to create yet another device configuration. This is demonstrated by a stack of two films that first served as the electrolyte layer and the pixel electrode of an electrochromic display, which then was detached from each other and transferred to another configuration, thus becoming the electrolyte and gate electrode of an electrochemical transistor. Further, smart pixels, consisting of the combination of one electrochromic pixel and one electrochemical transistor, have successfully been manufactured with the NFC-hybridized materials. The concept of system reconfiguration was further explored by that a pixel electrode charged to its colored state could be detached and then integrated on top of a transistor channel. This resulted in spontaneous discharging and associated current modulation of the transistor channel without applying any additional gate voltage. Our peel and stick approach promises for novel reconfigurable electronic devices, e.g. in sensor, label and security applications.     

平版印刷法制作电致发光显示器的微型化电极布线

平板印刷柔性的电致发光显示器的交错对插的电极.根据电致发光的荧光粉颗粒尺寸的大小采用的不同的方法将其沉积.小颗粒荧光粉分子可以很容易地与印刷油墨混合.使用这种交错对插电极的柔性显示器不需要透明的导电氧化物作为阳极,容易实现大规模生产,造价低.这种显示器使用 ACEL 可以实现多色彩显示.ACEL 可以发射出从绿光到使用ZnS:Clu,X(X=Cl,Br,I)荧光粉的蓝光,或者是到使用ZnS:Cu,Mn荧光粉的橙光.此外,还可以使用颜色转换材料以产生其他颜色的光.     

作为携带、沉积纳米荧光粉颗粒和纳米铁电体颗粒到FEDs和EL器件上的载体的可印刷的油墨、粘结剂

文章介绍了两种移植和可控纳米沉积荧光粉颗粒和纳米铁电体颗粒的载体.第一种载体是一种可以悬浮和沉积合成的具有亚微米级尺寸大小的荧光粉颗粒的油墨.解决了该油墨的聚集和沉降问题,并发现该油墨具有良好的液流学性能,从而可用于印刷高分辨率的荧光粉.测量了相关的单个象素的阴极发光密度以评定这种丝网印刷油墨的可重复性.第二种载体是一种粘结剂,这种粘结剂不仅可以携带 30 μm 以及更大的尺寸的电致发光的荧光粉,还可以携带纳米铁电体颗粒.这种新型的粘结剂可应用于不需要额外的绝缘反射层的低造价的 EL 显示器.从衬底按要求将发射层剥下来就形成了柔性薄膜,将该薄膜置于两电极之间,仍可保持其电致发光的活性.该粘结剂薄膜可以很容易地印刷和定型制成显示屏.     

Polypyrrole top-contact electrodes patterned by inkjet printing assisted vapor deposition polymerization in flexible organic thin-film transistors

Highly conductive polymer, polypyrrole (PPy) was successfully patterned as source and drain (S/D) electrodes for flexible pentacene thin film transistors in top-contact structure by combining inkjet printing and vapor deposition polymerization. Facile inkjet printing of initiator and subsequent exposure of pyrrole monomers resulted in selective absorption and polymerization of pyrrole monomers on the patterned initiator region. Pentacene transistors based on printed PPy electrodes exhibited higher electrical characteristics than that of the devices with thermally evaporated Au electrodes. Improved performance of the devices based on PPy electrodes could be attributed to the reduction of contact resistance at the interface between polymer and organic semiconductor. For the replacement of metal electrodes, vapor deposition polymerization assisted inkjet printing technique can provide a versatile method to utilize highly conductive polymer as a functional electrode of flexible organic electronic devices.     

Printable inorganic nanomaterials for flexible transparent electrodes: from synthesis to application

Printed and flexible electronics are definitely promising cutting-edge electronic technologies of the future.They offer a wide-variety of applications such as flexible circuits,flexible displays,flexible solar cells,skinlike pressure sensors,and radio frequency identification tags in our daily life.As the most-fundamental component of electronics,electrodes are made of conductive materials that play a key role in flexible and printed electronic devices.In this review,various inorganic conductive materials and strategies for obtaining highly conductive and uniform electrodes are demonstrated.Applications of printed electrodes fabricated via these strategies are also described.Nevertheless,there are a number of challenges yet to overcome to optimize the processing and performance of printed electrodes.     

Highly contrasted and stable electrochromic device based on well-matched viologen and triphenylamine

An electrochromic device (ECD) can change color absorption when subjected to an appropriate voltage. Such a device includes three components: a working electrode, a counter electrode and an electrolyte. Compatibility of these three components is important for ECD’s stability. In this study, two novel compatible electrochromic materials, cathodic 1-(9-hexyl-9H-carbazole)-1′-(propylphosphonic acid)-4,4′-bipyridilium dichloride and anodic (4-(diphenylamino)phenyl)methylphosphonic acid were designed, synthesized and fabricated into electrochromic electrodes using a chemisorption method. We characterized the electrochromic performance of these two electrodes, including the degree of color change, color changing voltage and charge capacity; the results indicated that they matched each other very well. An electrochromic device fabricated using these two electrodes, as expected, exhibited rapid, vivid color changes and proved highly stable for up to 100,000 cycles.     

Organische Feldeffekttransistoren auf Basis halbleitender Polymere

At present a variety of companies and institutes in the world are working on the development of organic field-effect transistors (OFET) and integrated polymer circuits (IPCs) to create a new low-cost low-performance electronics. This is especially suited for low-end electronics and RFID applications like electronic labels, smart cards, ident tags, electronic bar codes etc., which are needed in large amounts at lowest prices. The transistors are made as thin film transistors on flexible or rigid substrates by successive coating with the appropriate functional materials (polymer semiconductor, insulator, layers for electrodes). This setup can be realized either by organic and polymer materials only as well as by a combination of organic with inorganic materials. All-polymer field-effect transistors (PFETs) which completely consist of polymer layers (source, drain and gate electrodes, semiconductor, insulator) are of special interest. Later on they will offer the chance to use printing techniques for their production which enables high-volume printing of electronic circuits.     

Thermo-Adaptive Block Copolymer Structural Color Electronics

Flexible electronics that enable the visualization of thermal energy have significant potential for various applications, such as thermal diagnosis, sensing and imaging, and displays. Thermo-adaptive flexible electronic devices based on thin 1D block copolymer (BCP) photonic crystal (PC) films with self-assembled periodic nanostructures are presented. By employing a thermo-responsive polymer/non-volatile hygroscopic ionic liquid (IL) blend on a BCP film, full visible structural colors (SCs) are developed because of the temperature-dependent expansion and contraction of one BCP domain via IL injection and release, respectively, as a function of temperature. Reversible SC control of the bi-layered BCP/IL polymer blend film from room temperature to 80 °C facilitates the development of various thermo-adaptive SC flexible electronic devices including pixel arrays of reflective-mode displays and capacitive sensing display. A flexible diagnostic thermal patch is demonstrated with the bi-layered BCP/IL polymer blend enabling the visualization of local heat sources from the human body to microelectronic circuits.     

In Situ Spectroscopic Analysis of Sub‐Second Switching Polymer Electrochromes

As electrochromic polymers can switch with a high transmittance contrast in the sub‐second time frame, an analytical tool to rapidly probe the electrochemically‐induced optical transition is required for characterization of these materials for electronic displays and smart windows. A novel technique is described to synchronize the electrochemical and optical measurements by utilizing an external trigger to facilitate coordinated communication between the potentiostat, which applies a voltage to the electrode supported electrochromic polymers, and the optical spectrometer that records the induced optical transitions. By using a spectrometer containing a photodiode array detector, these measurements are capable of rapid data acquisition to track the electrochromic change in the polymer films, with as many as 500 spectra captured during a one‐second switch of the polymer from a colored, neutral to highly transmissive state. Additionally, with this rapid, full‐spectral measurement, it is possible to trace the temporal evolution of the electrochromic change to determine the presence of intermediate color tones, as well as their duration. Here, three polymers are shown, ECP‐Magenta, ECP‐Green, and ECP‐Black, which obtain high transmittance contrast between 40 to 50 Δ%T, with sub‐second switching times measured in the range of 400 to 700 ms, demonstrating their potential for use in electrochromic windows and displays where rapid transitions are desired.     

Inkjet-printed polymer thin-film transistors: Enhancing performances by contact resistances engineering

In this paper, we demonstrate how to enhance polymer thin-film transistors (PTFTs) performances made by low-cost inkjet printing technique. Indeed, in PTFTs, contact resistances between semiconducting conjugated polymers (SCPs) and Source and Drain (S&D) contacts may dominate the transport properties of such electronic devices. Here, we report measurements of these parasitic resistances for several couples of (i) SCPs, as active material, and (ii) electrodes, as S&D contacts, in bottom-contact inkjetted PTFTs. The differences in PTFT performances are discussed upon these contact resistance. For this, we evaluate the performances of several inkjetted couples of SCP/S&D compared to devices with evaporated metal-based S&D. By this way, we show that inkjet printing is a suitable low-cost technique to dispense polymers and inorganic nanoparticles for direct-writing of PTFTs. A significant reduction in the contact resistance R_C was achieved when inkjetted Pedot:Pss-based S&D electrodes are used instead of evaporated metal-based S&D electrodes. The improved efficiency of charge carrier injection is assumed to be due to the formation of a p-doped interfacial layer at the interface between the SCP and the S&D electrodes. All these results pave the way towards flexible electronics applications by using inkjetted polymers both for electrodes and semiconducting active layer on flexible plastic substrate.     

High‐Contrast Electrochromism and Controllable Dissolution of Assembled Prussian Blue/Polymer Nanocomposites

To maintain the momentum and impact of the field, assembled materials systems must increasingly incorporate broad functionality to meet real‐world applications. Here we describe nanocomposite films of specially synthesized inorganic Prussian blue (PB) nanoparticles and linear poly(ethylene imine) (LPEI) that possess the unusual functional combination of high‐performance electrochromism for displays and controllable dissolution for drug delivery. Fabrication using layer‐by‐layer (LBL) assembly was followed by spectroelectrochemical characterization, allowing a full composition determination rarely achieved for LBL films. The electrochromic performance of thick LPEI/PB nanocomposites most relevant to applications surpassed that of inorganic PB films with competitive switching speed and superior contrast. Oxidation beyond the primary electrochromic transition removes nanoparticle ionization and can controllably dissolve the films. Because PB is non‐toxic we suggest this mechanism for controlled in‐vivo drug delivery. The performance and multifunctional quality of these nanocomposites promise a strong impact on flexible displays, electrochromic windows, and even biomedical devices.     

Micromolding in capillaries and microtransfer printing of silver nanoparticles as soft-lithographic approach for the fabrication of source/drain electrodes in organic field-effect transistors

Within the past years there has been much effort in developing and improving new techniques for the processing of advanced functional materials used in promising applications like micro-optics or organic electronics. Much attention has been paid to solution-based techniques, which enable low-cost processing and new possible developments like flexible displays or inkjet printed electronics. An alternative approach to inkjet printing is soft-lithography, which is a collective term for a number of non-photolithographic techniques and has become an important tool for the micron-sized structuring of materials.Here we report on the use of micromolding in capillaries (MIMIC) and microtransfer printing (μTP) as two soft-lithographic techniques for the fabrication of silver source/drain electrodes in well-performing bottom-gate/bottom-contact organic field-effect transistors (OFETs) with poly(3-hexylthiophene) as active layer material.While MIMIC combines solution-processability with high lateral resolution for highly accurate patterns, μTP is the miniaturized counterpart to conventional letterpress printing.The performance of the OFETs fabricated with these techniques is similar to devices based on conventional gold source/drain electrodes with well-defined source-to-drain current saturation and a linear behavior at low drain voltages suggesting a low contact resistance and hence good carrier injection from the silver electrodes into the organic semiconductor.     

Paper‐Based Electrochromic Devices Enabled by Nanocellulose‐Coated Substrates

As environmental considerations for both the processing and disposal of electronic devices become increasingly important, the ability to replace plastic and glass substrates with bioderived and biodegradable materials remains a major technological goal. Here, the use of cellulose nanofiber‐coated paper is explored as an environmentally benign substrate for preparing low‐resistance (460 Ω sq^?1), colorless (a* = ?2.3, b* = ?2.7) printed poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes. The PEDOT:PSS/paper electrodes support the reversible oxidation of three electrochromic polymers (ECPs) (cyan, magenta, and yellow), affording the possibility for fully printed, color displays on paper. Lateral electrochromic devices (ECDs) incorporating an ion gel electrolyte are demonstrated where a magenta‐to‐colorless device achieves a color contrast (ΔE*) of 56 owing to a highly color‐neutral bleached state of the ECP (a* = ?0.5, b* = 2.9). Black‐to‐colorless devices achieve ΔE* = 29 and are able to retain 86% of their color contrast after 9000 switches. The switching times of these lateral devices are quantified through colorimetric image analysis which shows comparable performance for devices constructed on paper as devices using ITO/glass electrodes (10 Ω sq^?1). The paper ECDs are then combusted in air leaving 3% of the initial mass at 600 °C, highlighting this approach as a promising route toward disposable displays.     

Flexible and Transparent Electrochromic Displays with Simultaneously Implementable Subpixelated Ion Gel‐Based Viologens by Multiple Patterning

Electrochromic materials reversibly change colors by redox reactions depending on the oxidation states. To utilize electrochromic materials for active‐matrix display applications, an electrochromic display (ECD) requires simultaneous implementation of various colors and a fine‐pixelation process. Herein, flexible and transparent ECDs with simultaneously implementable subpixelated EC gels by sequential multiple patterning are successfully demonstrated. Ionic liquid‐based EC gels of monoheptyl‐viologen, diheptyl‐viologen (DHV), and diphenyl‐viologen (DPV) are used to create the colors of ECDs: magenta, blue, and green, respectively. Especially, to realize an improved green color, DHV–DPV composite gels are synthesized. Three EC gels exhibit stable properties without degradation during repetitive operation. Moreover, a transmittance greater than 90% is maintained in a bleached state, which is sufficient for application as a transparent display. The subpixelation process for multicolored‐flexible ECDs is designed to facilitate both easy fabrication and rapid operation with various patterns at low cost. The subpixelated EC gels using a film mask can be implemented to a minimum size of 200 µm. Furthermore, the subpixelated flexible ECDs exhibit high durability even after 1000 cycles of mechanical bending tests at a bending radius of 10 mm. Therefore, these EC materials can be used directly for flexible and transparent active‐matrix displays.     

有源矩阵有机电致发光像素电路的研究进展

有源驱动方式的有机发光二极管（AMOLED）较之无源驱动方式易于实现高亮度和高分辨率、功耗更小,更适合大屏幕显示。但传统的两管驱动电路会出现驱动管阈值电压在整个屏幕上分布不均匀,或长时间加偏压后驱动管的阂值电压发生漂移。本文在两管驱动电路的基础上介绍了几种最近提出的补偿电路并描述了它们的改善效果及各自存在的问题。     

3D Printed Micro-Electrochemical Energy Storage Devices: From Design to Integration

With the continuous development and implementation of the Internet of Things (IoT), the growing demand for portable, flexible, wearable self-powered electronic systems significantly promotes the development of micro-electrochemical energy storage devices (MEESDs), such as micro-batteries (MBs) and micro-supercapacitors (MSCs). By overcoming the limitations of traditional fabrication processes, 3D printing techniques have been attracting much attention in recent years. Theoretically, 3D printing technologies can manufacture any customized arbitrary geometry and structure of electrodes and other components by fast prototyping at a relatively low cost to achieve desirable electrochemical performance and simplified integration. To that end, a comprehensive review of recent progress on the applications of 3D printing in MEESDs is presented herein. Emphasis is given to the generally classified seven types of 3D printing techniques (their working principle, process control, resolution, advantages, and disadvantages), their applications to fabricate electrodes, and other components with different configurations. Finally, the integration of other electronics into MEESDs and a future perspective on the research and development direction in this important field are further discussed.     

Fast-switching all-printed organic electrochemical transistors

Symmetric and fast (～5 ms) on-to-off and off-to-on drain current switching characteristics have been obtained in screen printed organic electrochemical transistors (OECTs) including PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid)) as the active transistor channel material. Improvement of the drain current switching characteristics is made possible by including a carbon conductor layer on top of PEDOT:PSS at the drain electrode that is in direct contact with both the channel and the electrolyte of the OECT. This carbon conductor layer suppresses the effects from a reduction front that is generated in these PEDOT:PSS-based OECTs. In the off-state of these devices this reduction front slowly migrate laterally into the PEDOT:PSS drain electrode, which make off-to-on switching slow. The OECT including carbon electrodes was manufactured using only standard printing process steps and may pave the way for fully integrated organic electronic systems that operate at low voltages for applications such as logic circuits, sensors and active matrix addressed displays.     

Thermal Controlled Tunable Adhesive for Deterministic Assembly by Transfer Printing

Transfer printing techniques based on tunable adhesives that enable heterogeneous integration of materials in desired layouts are essential for developing existing and envisioned systems such as flexible electronics and micro-LED (µ-LED) displays. Here, a novel thermal controlled tunable adhesive, which not only has the ability of eliminating the interfacial adhesion for printing but also provides a new strategy for enhancing the interfacial adhesion for pick-up is reported. The tunable adhesive features cavities filled with air on the surface. This simple construct offers thermal controlled suction and thrust with their amplitudes on the order of a few tens of kPa within 100 °C temperature change, which enables a reliable damage-free transfer printing. Systematically theoretical and experimental studies reveal the underlying thermal induced pressure change mechanism and provide insights into the design and operation of the thermal controlled tunable adhesive. Demonstrations of this smart adhesive in manipulation of various surfaces and transfer printing of micro-scale Si inks and µ-LEDs illustrate its unusual capabilities for deterministic assembly by transfer printing.     

Inkjet printed flexible electrodes for surface electromyography

Recording of surface ElctroMyoGraphic (sEMG) signal represents a challenge, due to the nature both stochastic and deterministic of the biopotential. The sEMG signal results from the superimposed activity of a high number of motor units, artifacts, and background noise. Among the different non-invasive techniques to measure the muscle electrical activity, recent studies showed how High-Density surface EMG (HD-sEMG) constitutes a very effective tool. HD-sEMG uses multiple closely spaced electrodes overlying a restricted area of the skin and provides high definition temporal and spatial information on muscle activity. To optimize the features of the current devices for HD-sEMG signal detection, this paper reports on the realization of the first inkjet printed HD electrode matrix. The matrix was built by inkjet printing of a commercial silver-based ink on a flexible Kapton® substrate. While bringing about all advantages of drop-on-demand inkjet technology, such as rapid prototyping and simple CAD re-desing of customizable devices, the printed matrix produces interesting electrical results in terms of resolution, resistance and electrode–skin contact impedance. Electrode–skin impedance obtained with our measurement setup was indeed always in line, while not better than the one obtained with commercial electrodes.