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Displays are one of the most mature technologies in the field of printed electronics. Their ability to be manufactured in large quantities and at low cost has led to their recent uptake into the consumer market. Within this article this technology is extended to electrochromic display stickers. This is achieved using a recent reverse display architecture screen printed on textile and paper sticker substrates. The electrochromic stickers are comparable to plastic control substrates and show little performance difference even when adhered to curved surfaces. The electrochromic display technology is extended to sticker labels for authentication applications by patterning either the dielectric or the graphical layer. A proof‐of‐concept prototype emulating a wax seal on an envelope is presented to show that other colors can be implemented in this technology.

Organic materials have gained considerable attention for electrochromic (EC) applications owing to improved EC performance and good processability. As a class of well-recognized organic EC materials, viologens have received persistent attention due to the structural versatility and property tunability, and are major active EC components for most of the marketed EC devices. Over the past two decades, extensive efforts have been made to design and synthesize different types of viologen-based materials with enhanced EC properties. This review summarizes chemical structures, preparation and EC properties of various latest viologen-based electrochromes, including small viologen derivatives, main-chain viologen-based polymers, conjugated polymers with viologen side-chains and viologen-based organic/inorganic composites. The performance enhancement mechanisms are concisely discussed. The current marketed viologens-based electrochromic devices (ECDs) are briefly introduced and an outlook on the challenges and future exploration directions for viologen-based materials and their ECDs are also proposed.

The application potential of flexible electrochromic materials for wearable devices, smart textiles, flexible displays, electronic paper, and implantable biomedical devices is enormous. These materials offer the advantages of conformability and mechanical robustness, making them highly desirable for these applications. In this review, we comprehensively examine the field of flexible electrochromic materials, covering topics such as synthesis methods, structure design, electrochromic mechanisms, and current applications. We also address the challenges associated with achieving flexibility in electrochromic materials and discuss strategies to overcome them. By shedding light on these challenges and proposing solutions, we aim to advance the development of flexible electrochromic materials. We also highlight recent advances in the field and present promising directions for future research. We intend to stimulate further innovation and development in this rapidly evolving field and encourage researchers to explore new opportunities and applications for flexible electrochromic materials. Through this review, readers can gain a comprehensive understanding of the synthesis, design, mechanisms, and applications of flexible electrochromic materials. It serves as a valuable resource for researchers and industry professionals looking to harness the potential of these materials for various technological applications.

HighlightsA reversible Zn2+ insertion in anatase TiO2 nanocrystals is reported for the first time.This is the first report regarding TiO2 for zinc-anode-based electrochromic devices, which will subsequently broaden its applications to zinc-ion electrochemical cells.A prototype device based on the TiO2 nanocrystals delivers a high optical modulation, fast response times, and robust electrochemical stability.Zinc-anode-based electrochromic devices (ZECDs) are emerging as the next-generation energy-efficient transparent electronics. We report anatase W-doped TiO2 nanocrystals (NCs) as a Zn2+ active electrochromic material. It demonstrates that the W doping in TiO2 highly reduces the Zn2+ intercalation energy, thus triggering the electrochromism. The prototype ZECDs based on W-doped TiO2 NCs deliver a high optical modulation (66% at 550 nm), fast spectral response times (9/2.7 s at 550 nm for coloration/bleaching), and good electrochemical stability (8.2% optical modulation loss after 1000 cycles).

There is keen interest in the use of amorphous WO3 thin films as cathodic electrodes in transmittance-modulating electrochromic devices1–4. However, these films suer from ion-trapping-induced degradation of optical modulation and reversibility on extended LiC-ion exchange. Here,we demonstrate that ion-trapping-induced degradation, which is commonly believed to be irreversible, can be successfully eliminatedby constant-current-driven de-trapping; that is, WO3 films can be rejuvenated and regain their initial highly reversible electrochromic performance. Pronounced ion trapping occurs when x exceeds 0.65 in LixWO3 during ion insertion. We find two main kinds of Li+-ion-trapping site (intermediate and deep) in WO3, where the intermediate ones are most prevalent. Li+ ions can be completely removed from intermediate traps but are irreversibly bound in deep traps. Our results provide a general framework for developing and designing superior electrochromic materials and devices.

Highlights A flexible dual-band electrochromic device with a high optical modulation and a long cycle life was reported. The device assembled can modulate the visible light and near-infrared independently and effectively, showing higher energy-saving performance than commercial low-emissivity glass in most climatic zones around the world. The flexible device also shows good energy storage and energy recycling performances, recycling 51.4% of the energy consumed in the coloration process for local reusing. Dual-band electrochromic devices capable of the spectral-selective modulation of visible (VIS) light and near-infrared (NIR) can notably reduce the energy consumption of buildings and improve the occupants' visual and thermal comfort. However, the low optical modulation and poor durability of these devices severely limit its practical applications. Herein, we demonstrate an efficient and flexible bifunctional dual-band electrochromic device which not only shows excellent spectral-selective electrochromic performance with a high optical modulation and a long cycle life, but also displays a high capacitance and a high energy recycling efficiency of 51.4%, integrating energy-saving with energy-storage. The nanowires structure and abundant oxygen-vacancies of oxygen-deficient tungsten oxide nanowires endows it high flexibility and a high optical modulation of 73.1% and 85.3% at 633 and 1200 nm respectively. The prototype device assembled can modulate the VIS light and NIR independently and effectively through three distinct modes with a long cycle life (3.3% capacity loss after 10,000 cycles) and a high energy-saving performance (8.8 °C lower than the common glass). Furthermore, simulations also demonstrate that our device outperforms the commercial low-emissivity glass in terms of energy-saving in most climatic zones around the world. Such windows represent an intriguing potential technology to improve the building energy efficiency.

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.

Electrochromism is the exhibition of reversible optical property changes by certain materials upon administration of voltage across it. Tungsten oxide (WO 3 ) finds a diverse range of applications because of its exceptional electrochromism. Amidst all applications, an electrochromic device (ECD) can be considered the most prominent application due to energy saving perspective. Although, WO 3 itself has been noticed as an efficient electrochromic layer for EDCs; however, there exists a lot of space and ideas to enhance the electrochromism and hence the efficiency of an ECD. Recently, scientists are paying close attention to hybrid or composite films such as TiO 2 /WO 3 and TiO 2 /V 2 O 5 . Such hybrid films are known as electrochromic double layer (ECDL). This review article strives to deepen our understanding of ECDL and assess their feasibility in the enrichment of electrochromism in ECDs by replacing a single electrochromic layer with an ECDL toward an energy-saving regime. Graphical Abstract

Two di-ureasils incorporating oxyethylene segments with average molecular weights Y = 600 and 900 g mol −1 , prepared by the sol-gel method, and doped with the ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and lithium tetrafluoroborate (LiBF 4 ) salt were prepared. The as-obtained films are translucent, flexible, and hydrophobic, and have a low level of nanoscale surface roughness. The ionic conductivity values exhibited by an optimized sample are 8.10 × 10 −5 and 2.8 × 10 −4 S cm −1 at room temperature and 55 °C, respectively. The main goal of the work was to employ the electrolytes in prototype electrochromic devices (ECDs) with the [glass/a-IZO/a-WO 3 /d-U(Y)LiBF 4 -[Bmim]Cl/c-NiO/a-IZO/glass], noted as ECD1 for Y = 600 and ECD2 for Y = 900, where a-WO 3 and c-NiO stand for amorphous tungsten oxide and crystalline nickel oxide, respectively. At 555 nm the ECD1 device exhibited the highest coloration efficiency for coloring (CE in = −420.621 cm 2 ·C −1 ), the highest optical density value (∆(OD) = 0.13) and good cycling stability. In this article, the results of a preliminary evaluation of hybrid electrolytes, produced by a sol-gel process, as multi-functional components in prototype electrochromic devices are reported.

Tungsten oxide‐mica composites were prepared by adding different amounts of commercial mica (alumina silicate) in order to provide high luster to electrochromic coatings. The mechanical stability was sustained for up to 50 weight % mica for application in aqueous medium. The electrochemical properties, coloration, and luster were investigated. The luster of the composites increased roughly linearly with increased mica content and was retained after coloration. The addition of 10 weight % mica was found to be optimal with respect to the compromise between electrochromic coloration and pearlescent luster. This is, to the best of our knowledge, the first report on the preparation and characterization of WO 3 ‐mica inorganic composites with high luster in both bleached and colored states.