Search

Electrochromic materials are a significant class of optoelectronic functional materials that can change colour by adjusting the voltage periodically. In recent years, there has been rapid development in electrochromic technology. However, current research predominantly focuses on traditional rigid electrochromic devices (ECDs), typically using conductive glass substrates such as indium tin oxide. These rigid colour‐changing devices face significant challenges, including large thickness, low mechanical strength, and high cost, which hinder the advancement and commercialisation of electrochromic technology. With the rise of wearable devices and electronic skins, among other future technologies, flexible ECDs have garnered much attention due to their foldability, wearability, and even embeddability. They have emerged as a research hotspot in the field of electrochromism. As a further development direction of flexible ECDs, achieving stretchability poses higher difficulties as it requires maintaining high performance under large strains and even distortions. This article provides an overview of the latest advances in stretchable electrochromic devices (SECDs) from the perspectives of structural and material design. Regarding structural design, the 'island‐bridge' structure, the 'longitudinal wave' structure, and core‐shell structures are discussed. In terms of material design, the design schemes of substrate, conductive layer, electrochromic layer and electrolyte layer are mainly introduced, with particular emphasis on the introduction of gel electrolyte. Finally, the challenges and difficulties faced by the development of SECDs are briefly analysed. [ABSTRACT FROM AUTHOR]

Electrochromic supercapacitors, which indicate energy states through optical color changes, are gaining significant attention for their potential in energy saving and recycling. In this study, a novel metal–organic coordination polymer (DTPB‐MCP) is successfully synthesized using an N,N’‐diphenyl‐1,4‐phenylenediamine (DTPB)‐functionalized phenanthroline ligand. The resulting DTPB‐MCP film demonstrated desirable electrochromic performance in both the visible light (ΔT:77.6% at 730 nm) and near‐infrared (ΔT: 49.2% at 1410 nm) regions, as well as decent energy‐storage capabilities (16.4 mF cm−2 at 0.1 mA cm−2), attributed to the presence of multiple redox centers. Furthermore, a hybrid electrochromic supercapacitor is also developed by combining DTPB‐MCP with V₂O₅ (DTPB‐MCP//V₂O₅), showcasing a significant optical contrast (47.6% at 750 nm and 14.5% at 1420 nm), an acceptable capacitance of 11.5 mF cm−2 with good rate performance, and impressive cycling stability (maintaining 81% of capacitance after 2750 charging/discharging cycles). In addition, >60% of electric energy can be reused to drive small household appliances during the bleaching process. The design principles outlined in this study offer valuable insights into the development of high‐performance dual‐band electrochromic energy‐storage materials, highlighting their potential applications in energy recovery and reuse. [ABSTRACT FROM AUTHOR]

As a promising energy‐saving technology, electrochromic technology has been widely investigated for practical applications. However, there is relatively few research about the applications under certain extreme climatic conditions since gel electrolytes often occur freezing and volatilizing. In this work, a poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) gel electrolyte with good anti‐freezing and heat‐resistance performance is developed. Utilizing hydrated tungsten oxide (WO3·xH2O) and polyaniline (PANI) as electrochromic materials and the PVA/PAA gel as electrolyte, a WO3·xH2O/PVA/PAA‐ethylene glycol (EG)‐H2O/PANI electrochromic device (WO3·xH2O/PAEH/PANI ECD) is obtained, which can work efficiently at wide operating temperatures from −20 to 60 °C. The device has multiple reversible color changes, a large optical modulation of 66.2% at 600 nm, high coloration efficiency of 386.0 cm2 C−1, fast responses (with coloration/bleaching times of 1.3/1.1 s), as well as excellent cyclic stability (82.0% of the initial optical modulation is still retained after 2100 cycles). This work reveals the potential application prospects of PAEH gel electrolyte in practical extreme operating conditions. [ABSTRACT FROM AUTHOR]

Cracking caused by aging or repeated bending can severely affect the lifetime of electrochromic devices. In this work, a self‐healing electrochromic hydrogel was developed with poly (vinyl alcohol) (PVA)‐sodium carboxymethyl chitosan (SCC) semi‐inter transfer network as the matrix, viologen bromide (HPV2+2Br−) as the electrochromic substance, and borax as the cross‐linking agent. The self‐healing properties of hydrogel stem from the dynamic and reversible borate bonds between borax and PVA molecular chains. As the voltage changes, the color of the device transitions from colorless to light purple and then to dark purple. The optical contrast at 600 nm reaches approximately 51 %. At room temperature, the disconnected hydrogel can fully restore its original state after 30 minutes of contact, effectively addressing issues related to cracks and damage in flexible electrochromic devices. This research holds significant implications for enhancing the reliability and stability of flexible electrochromic devices. [ABSTRACT FROM AUTHOR]

Viologens, with their unique redox‐active properties, have garnered increasing attention in the development of electrochromic devices. This review focuses on key strategies in molecular design, synthesis methodologies, and tailored functionalities that have propelled the field forward from 2019 to the present. The convergence of these approaches has led to the construction of viologen‐based electrochromic materials with enhanced performance, stability, and responsiveness. The review not only examines the current state of the field but also explores promising outlooks and opportunities, including tailored applications, environmental sustainability, and integration with emerging technologies. The synergy between molecular engineering and viologen‐based electrochromic materials holds significant promise, shaping the future of dynamic, responsive materials in diverse technological domains. This review serves as a valuable resource for researchers, offering insights into recent breakthroughs and inspiring further advancements in this rapidly evolving field. [ABSTRACT FROM AUTHOR]

Reconstructing the visible spectra of real objects is critical to the spectral camouflage from emerging spectral imaging. Electrochromic materials exhibit unique superiority for this goal due to their subtractive color‐mixing model and structural diversity. Herein, a simulation model is proposed and a method is developed to fabricate electrochromic devices for dynamically reproducing the visible spectrum of the natural leaf. Over 20 kinds of pH‐dependent leuco dyes have been synthesized/prepared through molecular engineering and offered available spectra/bands to reconstruct the spectrum of the natural leaf. More importantly, the spectral variance between the device and leaf is optimized from an initial 98.9 to an ideal 10.3 through the simulation model, which means, the similarity increased nearly nine‐fold. As a promising spectrum reconstruction approach, it will promote the development of smart photoelectric materials in adaptive camouflage, spectral display, high‐end encryption, and anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Multivalent ions, especially Al3+ in aqueous electrolyte contributes to higher capacity and color contrast for more sustainable post‐lithium electrochromism and energy storages. However, the lack of suitable cathodic and anodic electrochromic materials is a major challenge for Al‐ion electrochromic batteries, which limits their optical contrast and lifespan. Herein, we report that Wadsley‐Roth phase Nb18W16O93 with open structure achieves Al3+ intercalation/extraction reversibly. The complementary electrochromic energy storage devices based on Nb18W16O93 coupled with Prussian blue using hybrid Al3+/K+ aqueous electrolytes show a fast response, a high capacity and a large coloring efficiency. The superior performances are due to the cations of Al3+ and K+ selectively insert/extract in the electrode of Nb18W16O93 and Prussian blue, respectively. This work provides an effective strategy for high‐performance and low‐cost electrochromic batteries with higher sustainability. [ABSTRACT FROM AUTHOR]

Electrochromic materials (ECMs), the colors of which can be electrically modulated by small driving voltages with a unique open‐circuit memory effect, are in great demand in various application fields. However, traditional ECMs exhibit a narrow modulation range of color gamut under the electric stimulus, owing to the monotonous chemical coloration in an absorption manner. Multicolor ECMs with optical nanostructures can greatly extend the color gamut by incorporating complex optical interactions such as interference and diffraction. Mie scatterer nanospheres (MSNSs) are a kind of nanospheres with unique optical structures that can simply exhibit and change vivid structural colors by adjusting their diameters. Herein, this work reports multicolor ECMs based on MSNSs with polymer shells of poly‐3,4‐ethylenedioxythiophene (PEDOT) and poly‐pyrrole (PPY). They possess a superior optical modulation capability with a wide color gamut, a fast response rate, a visible‐angle‐independence, etc. Additionally, a nano‐dispersion strategy is used to prepare mixed electrochromic pigments with a nanoscale uniformity, further broadening the color gamut tunability. Simulations in wave optics and Mie scattering theory are conducted to unveil the multicolor modulation mechanism, demonstrating the interactions of MSNSs with incident lights. This work provides a feasible approach for fabricating multicolor ECMs with more application potential. [ABSTRACT FROM AUTHOR]

Organic‐hybrid particle‐based materials are increasingly important in (opto)electronics, sensing, and catalysis due to their printability and stretchability as well as their potential for unique synergistic functional effects. However, these functional properties are often limited due to poor electronic coupling between the organic shell and the nanoparticle. N‐heterocyclic carbenes (NHCs) belong to the most promising anchors to achieve electronic delocalization across the interface, as they form robust and highly conductive bonds with metals and offer a plethora of functionalization possibilities. Despite the outstanding potential of the conductive NHC‐metal bond, synthetic challenges have so far limited its application to the improvement of colloidal stabilities, disregarding the potential of the conductive anchor. Here, NHC anchors are used to modify redox‐active gold nanoparticles (AuNPs) with conjugated triphenylamines (TPA). The resulting AuNPs exhibit excellent thermal and redox stability benefiting from the robust NHC‐gold bond. As electrochromic materials, the hybrid materials show pronounced color changes from red to dark green, a highly stable cycling stability (1000 cycles), and a fast response speed (5.6 s/2.1 s). Furthermore, TPA‐NHC@AuNP exhibits an ionization potential of 5.3 eV and a distinct out‐of‐plane conductivity, making them a promising candidate for application as hole transport layers in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The regulation of infrared (IR) thermal radiation has received widespread attention; the proposals have been made for various devices that use electrochromic materials. However, the visible appearance of the mentioned devices also changes when the IR states are altered. Herein, the memristive mechanism is utilized to regulate IR emissivity and design a novel transparent memristor‐type modulator featuring an Indium tin oxide (ITO)/HfO2/ITO structure. The modulator exhibits a dynamic emissivity variation of 0.38 in the IR region of 2.5–25 μm, without compromising transparency in the visible region under the application of an electric voltage. The migration of oxygen vacancies results in the modification of interface barriers and the formation of oxygen vacancy‐enriched regions, thereby enabling the modulator to exhibit resistive switching behavior and regulate IR emissivity. An array of modulators is also assembled, demonstrating the ability to independently display visible and IR information. In this work, new possibilities are presented for various applications such as multispectral displays, energy‐efficient thermoregulation, encrypted information displays, and camouflage. [ABSTRACT FROM AUTHOR]

Unveiling the ion transport mechanism to design and explore efficient and stable ion transport pathways for high‐performance transition metal oxide (TMO)−based electrochromic materials is highly desired yet challenging. Herein, this study has demonstrated that the interlayer spacing of layered vanadium penoxide (V2O5) films can be tuned by inserting different amounts of lithium−ion (Li+) within host V2O5 material, as well as adjusting ion transport behavior and electrochromic performance. These results show that V2O5 with a small amount of ion insertion delivers a stable ion transport process and electrochromic properties. Increasing the amount of inserted Li+ will enlarge the interlayer spacing, which provides abundant active sites and efficient ion transport channels, and thus reversible and rich color variation of yellow−green−blue−olive green−orange is realized. Nevertheless, an excess of ion insertion results in the crystal structure collapse and cyclic stability degradation. These findings give a rationale for the evolution of electrochromic properties during different electrochemical reaction stages. This work provides considerable insight into the ion transport behavior within the layered V2O5 films, which gives fundamental theoretical guidance for developing and designing superior layered TMO electrochromic materials. [ABSTRACT FROM AUTHOR]

In recent years, multicolor electrochromic devices (ECDs) have attracted much attention due to their application potential for rich color similar to RGB mode. Although organic electrochromic (EC) materials are widely used in multicolor electrochromism because of their multicolor properties, remarkable weatherability remains challenging. Inorganic EC materials especially transition metal oxide are particularly attractive for excellent weatherability in ECD fabrication. Moreover, by selection of electrolytes, better ionic transfer efficiency can be rendered in the EC process. Although the morphology regulation of the EC film and the selection of electrolytes in the ion transmission layer play important roles in optimizing EC performance and have been extensively studied, a systematic and comprehensive review is lacking. In this review, the morphology regulation of the EC film and selection rules of electrolytes in the multicolor ECDs is focused, and the advantages and disadvantages of existing ways are discussed. The current application of multicolor ECDs is also outlined and it is hoped that this review can contribute some inspiration to designing and improving multicolor ECDs. [ABSTRACT FROM AUTHOR]

The systematic study of two ionic porous organic polymers (iPOPs) based on viologens and their first applications in the electrochromic field are reported. The viologen‐based iPOPs are synthesized by electrochemical polymerization with cyano groups, providing a simple and controllable method for iPOPs that solves the film preparation problems common to viologens. After the characterization of these iPOPs, a detailed study of their electrochromic properties is conducted. The iPOP films based on viologens structure exhibit excellent electrochromic properties. In addition, the resulting iPOP films show high sensitivity to electrolyte ions of different sizes in the redox process. Electrochemical and electrochromic data of the iPOPs explain this phenomenon in detail. These results demonstrate that iPOPs of this type are ideal candidates as electrochromic materials due to their inherent porous structures and ion‐rich properties. [ABSTRACT FROM AUTHOR]

Cu(I) complexes have garnered substantial attention in recent years because of their intriguing photophysical properties and their applications in different fields. Herein, we have reported a new four‐coordinated heteroleptic Cu(I) complex using dicnq, a 1,10‐phenanthroline‐based cyno‐substituted ligand, and Xantphos, a bulky as well as rigid chelating diphosphine ligand. The synthesized complex is characterized by multinuclear NMR and HRMS and described as [Cu (Xantphos)(dicnq)]PF6 (1). Complex 1 exhibits absorption within the range of 380–500 nm and emits around 700 nm, attributed to the metal‐to‐ligand charge transfer transition. Theoretical calculations suggest that the HOMO is predominantly located on the Cu(I) center, whereas LUMO is associated with the dicnq ligand. Further, 1 was found to show vapochromic behavior and blue‐shifted emission was observed in the presence of solvent vapors which can show π–π interaction with dicnq. Notably, the complex demonstrates electrochromic activity, prompting the fabrication of a device (ITO/P3HT/Cu complex/ITO) for an in‐depth exploration of its electrochromic properties. The working potential range for the device was found to be ±3 V. On and Off states show the device has an impressive contrast ratio of ~40% and 38% at 520 and 800 nm, respectively. In addition to this, the device shows rapid coloration and bleaching times of 0.8 and 0.5 s, respectively. In terms of contrast, switching speed, stability, and efficiency values at two different wavelengths, the device shows good electrochromic results. [ABSTRACT FROM AUTHOR]

Electrochromic devices (ECDs) possess the performance advantages in terms of color adjustability, low power consumption, and visual friendliness, emerging as one of the ideal candidates for energy‐efficient smart windows, next‐generation displays, and wearable electronics. The optical and electrical characteristics of ECDs can be adjusted by modifying the materials or structure of devices. This review summarizes the recent developments of innovative technologies and key materials of ECDs for display applications, highlighting the key issues and development trends in this area. [ABSTRACT FROM AUTHOR]

NiO, an anodic electrochromic material, has applications in energy‐saving windows, intelligent displays, and military camouflage. However, its electrochromic mechanism and reasons for its performance degradation in alkaline aqueous electrolytes are complex and poorly understood, making it challenging to improve NiO thin films. We studied the phases and electrochemical characteristics of NiO films in different states (initial, colored, bleached and after 8000 cycles) and identified three main reasons for performance degradation. First, Ni(OH)2 is generated during electrochromic cycling and deposited on the NiO film surface, gradually yielding a NiO@Ni(OH)2 core–shell structure, isolating the internal NiO film from the electrolyte, and preventing ion transfer. Second, the core–shell structure causes the mode of electrical conduction to change from first‐ to second‐order conduction, reducing the efficiency of ion transfer to the surface Ni(OH)2 layer. Third, Ni(OH)2 and NiOOH, which have similar crystal structures but different b‐axis lattice parameters, are formed during electrochromic cycling, and large volume changes in the unit cell reduce the structural stability of the thin film. Finally, we clarified the mechanism of electrochromic performance degradation of NiO films in alkaline aqueous electrolytes and provide a route to activation of NiO films, which will promote the development of electrochromic technology. [ABSTRACT FROM AUTHOR]

The interest in all solid organic based electrochromic devices (ECDs) is on the increase. This is because these devices offer the applicability of electrochromic materials in products such as smart sensors, smart windows, flexible wearables and energy storage devices. The use of quasi‐solid electrolytes for the construction of these ECDs is attractive because of their ease of preparation, availability, low cost, improve electrochromic performance, good ionic conductivity and prevention of leakages in ECDs. Hence, in this review, a detailed discussion is presented on the progress in the development of semi‐solid electrolytes for ECDs fabrication. The preparation of the most common electrolytes that have been applied for organic based ECDs are summarized. Particular attention is given to efforts and strategies that have been adopted to improve the efficiency of quasi‐solid electrolytes. Importantly, knowledge gaps that warrant further research are clearly identified and recommendations for future works are suggested. This review will be very beneficial for both established and new researchers in the field of electrochromic devices and material science. [ABSTRACT FROM AUTHOR]

As the proportion of buildings energy consumption increases, the issue of low energy utilization efficiency becomes increasingly prominent. Approximately 45% of the energy is lost through doors and windows, a significant concern that has drawn society's attention to the potential of electrochromic technology, which can regulate light transmittance and absorption effectively. Specifically, dual‐band electrochromic materials offer a promising solution to this issue, as they can manipulate the transmission ratios of visible (VIS) and near‐infrared (NIR) light to obtain "bright," "cold," "warm," and "dark" independent modes. However, research on dual‐band electrochromic materials and smart windows is still infant, and many challenges including performance and assembly issues, are significant obstacles to the advancement and application of this technology. This review clarifies the basic characteristics of dual‐band electrochromic materials and smart windows, including configurations, operational mechanisms, and performance assessment parameters. In‐depth examination of potential dual‐band electrochromic materials and methods for achieving independent modulation is provided, along with an analysis of the challenges and potential solutions for performance and assembly issues. Finally, the future prospects of dual‐band electrochromic smart windows (ESWs) are underscored. The hope is to eventually facilitate the commercial application of these windows, which can significantly contribute to the creation of modern, energy‐efficient buildings. [ABSTRACT FROM AUTHOR]

Recent years have shown many advances in the development of tunable structural colors by combining nanostructures with electrochromic materials. One main goal is to develop energy saving color displays that rely on ambient light instead of being emissive. However, all displays need to be pixelated to show arbitrary images and few studies have addressed the challenge of preparing and controlling individual electrochromic pixels. Herein, a very simple method to reach this milestone by using passive matrix addressing is presented, which requires no additional electronic components in the pixels. It is shown that the common transparent conductor indium tin oxide (ITO) in non‐aqueous electrolytes exhibits the diode‐like behavior (threshold in voltage in relation to current and coloration) necessary to prevent significant cross‐talk between pixels. The chemical nature of the redox activity that enables this behavior is attributed to omnipresent oxygen and the formation of superoxide ions. Additionally, it is shown that a gel‐like electrolyte can be prepared by optical lithography, which makes the concept compatible with patterning of pixels at high resolution. This method for preparing pixelated displays should be compatible with practically any type of electrochromic surface in both reflective and transmissive configurations. Also, the counter electrode maintains excellent transparency since it simply consists of ITO. The results should prove very useful as the research field of tunable structural colors moves from proof‐of‐concept to real devices. [ABSTRACT FROM AUTHOR]

Electrically triggered color‐changing materials, termed as electrochromic materials, offer precise and programmable color transistions through the manipulation of electric field frequency and amplitude. They are used as displays, sensors, military camouflage, wearable devices, and anticounterfeiting materials. Their future advancements depend on clear understanding of the color change mechanisms and pros/cons between different electrochromic materials. To this end, we starts by categorizing electrochromism into two classes according to color production mechanism: chemical color‐based and physical color‐based. Within the former, color emerges from chemical molecules selectively absorbing specific wavelengths of light and color changes stem from electrochemical redox reactions. The latter, meanwhile, hinges upon electrically induced alterations in the geometries, dimensions, or arrangements of nano/micro structures, such as photonic crystals and plasmonic nanostructures. The principles of color changes in both categories are detailed, and compare their differences in terms of response time, operating voltage, degree of color change, and stability. At the end, their applications will be discussed spanning from smart windows to color display, dynamic camouflage, energy storage, and thermal management. This critical review is aimed to provide multidisciplinary insights that will benefit both novices and seasoned experts engaged in fundamental exploration or practical investigations of electrochromic materials. [ABSTRACT FROM AUTHOR]

Electrochromic materials (ECMs) have important potential applications in the field of intelligent optoelectronic displays. However, ECMs and its devices cannot be truly applied on a large scale until the problem of their long‐period performance degradation is really solved. This article focuses on summarising the attenuation mechanism of common ECMs, which is mainly divided into three types: structural damage, irreversible reaction and ion capture, and summarises four optimisation strategies for the cyclic stability of ECMs at the present stage: doping is used to change the internal structure of the material in order to achieve the purpose of improving the cyclic stability; composite means to allow a variety of materials to interact with each other in order that the original material has no excellent performance; improve the cyclic stability of ECMs by the special characteristics of nanostructures; and enhance the performance by optimising the preparation process and regulating the parameters in the preparation process. Finally, the article discusses the potential for optimising the long‐term stability of ECMs in the future, based on the earlier‐mentioned research. [ABSTRACT FROM AUTHOR]

Electrochromic devices (ECDs) have attracted substantial attention on account of their unique characteristics and prosperous applications. However, their monotonous color modification remains a momentous challenge that significantly restricts their application scope. Integrating structural colors that arise from the interaction between light and periodic micro/nanostructures with electrochromic materials (ECMs) turns out to be an effective approach to enhancing the comprehensive performance of ECDs more than the coloration effectiveness. This review provides an overview on the recent burgeoning development of structural color ECDs regarding strategies and applications. The performance parameters of ECDs and physical principles regarding the generation of structural colors are introduced. Then, strategies that introduce structural colors into ECDs are discussed according to the category of chromogenic micro/nanostructures, namely, gratings, (single‐layer and multilayer) thin films, photonic crystals, plasmonic metasurfaces, and composite structures. The current state‐of‐the‐art research activities of structural color ECDs for display application including segmented and pixelated devices are also presented. Additionally, the future perspective of structural color ECDs with respect of major challenges and potential solutions is proposed. [ABSTRACT FROM AUTHOR]

Electrochromic devices have important applications in building energy conservation, next‐generation displaying, and security encryption, while durable and high‐performance electrochromic materials are highly desirable. Herein, a Zn‐based electrochromic smart window by using 3D ordered macroporous amorphous WO3 (a‐WO3) arrays as cathode is reported. Benefiting from a 3D ordered macroporous structure with a high specific surface area that accelerates the ion diffusion and migration, and the oxygen vacancy modulated a‐WO3 providing abundant zinc ion insertion channels, the as‐fabricated zinc‐based a‐WO3 inverse opal (a‐WO3‐IO) device exhibits excellent electrochromic properties, including large light modulation (83% optical contrast at 700 nm), fast response time (5.3 s for coloring and 3.2 s for bleaching), and robust cycling stability. Moreover, a solid‐state a‐WO3‐IO prototype electrochromic smart window is demonstrated for light modulation, electronic display, and power supply. Furthermore, experimental results and theoretical calculations reveal that 3D macroporous amorphous WO3 with rich oxygen vacancies can enhance the zinc ion absorption and diffusion, leading to the enhancement of electrochromic performance. [ABSTRACT FROM AUTHOR]

Layered Double Hydroxide (LDH) is an α‐modification of the M‐host (M2+) hydroxide, in which some part of the M‐host cations is replaced by M‐guest cations (M3+ or M4+). The emerging excess positive charge is compensated by the intercalation of anions into the interlayer space, which also contains water molecules. LDHs exhibit anion exchange properties. Targeted ionic design of LDHs via combining three components (M‐host, M‐guest cations, intercalated anions) allows the creation of a very wide range of highly efficient electrochemical, electrocatalytic, electrochromic substances, catalysts, ion exchangers, sorbents, color pigments, pharmacological drugs, food, and cosmetic additives. In this review, the structure and areas of application of LDHs are considered from the perspective of the targeted ionic design of a substance for a specific application. [ABSTRACT FROM AUTHOR]

Nickel hydroxides (monohydroxides of several modifications and layered double hydroxides, based on nickel hydroxide) have high electrochemical, electrochromic, and electrocatalytic properties that allow them to be effectively used as an active substance in alkaline batteries, hybrid supercapacitors, electrochemical sensors, for electrocatalytic oxidation of organic substances and as an electrochromic device. Each application has its specific requirements for nickel hydroxides which must be defined. For an effective application, it is necessary to carry out a targeted construction of structure and composition, and selection of characteristics of nickel hydroxides and to develop targeted methods and conditions for nickel hydroxide synthesis. The structure, properties, and methods of preparation for use in various fields of nickel hydroxide application have been considered from the targeted ternary points of view: requirements definition, types and characteristics selection, and applying the synthesis method in industry. The 3‐level hierarchical complex of mechanisms for the formation of nickel hydroxides has been described. Also, the contribution of Ukrainian scientists to research in the field of nickel hydroxides is considered. [ABSTRACT FROM AUTHOR]

Viologens, a typical group of electrochromic materials, show rich color changes under the external electrical stimulus. Recently, some of the viologen derivatives are reported to exhibit good luminescent performance. However, their luminescence colors are difficult to adjust owing to the strong electron‐accepting properties of viologens, which seriously hinders their applications in smart light‐emitting devices. In this work, the color/emission dual‐switchable viologen derivative Phen‐vio is designed and synthesized by introducing fluorophore 1,10‐phenanthroline into 4,4′‐bipyridine, for multicolor large‐area and patterned electrochromic/electrofluorochromic devices. Under voltage driving of −2.3 and −2.8 V, the devices exhibited reversible color and fluorescence color changes from light yellow to dark orange to dark blue, and from yellow to orange to green, respectively. Moreover, the devices displayed a high color contrast ratio of up to 77% at 600 nm. More importantly, the driving voltages of the devices do not vary with the change of the device area, which is huge application potential in smart windows and tags. [ABSTRACT FROM AUTHOR]

Owing to low‐power, fast and highly adaptive operability, as well as scalability, electrochemical random‐access memory (ECRAM) technology is one of the most promising approaches for neuromorphic computing based on artificial neural networks. Despite recent advances, practical implementation of ECRAMs remains challenging due to several limitations including high write noise, asymmetric weight updates, and insufficient dynamic ranges. Here, inspired by similarities in structural and functional requirements between electrochromic devices and ECRAMs, high‐performance, single‐transistor and neuromorphic devices based on electrochromic polymers (ECPs) are demonstrated. To effectively translate electrochromism into electrochemical ion memory in polymers, this study systematically investigates polymer–ion interactions, redox activity, mixed ionic–electronic conduction, and stability of ECPs both experimentally and computationally using select electrolytes. The best‐performing ECP‐electrolyte combination is then implemented into an ECRAM device to further explore synaptic plasticity behaviors. The resulting ECRAM exhibits high linearity and symmetric conductance modulation, high dynamic range (≈1 mS or ≈6x), and high training accuracy (>84% within five training cycles on a standard image recognition dataset), comparable to existing state‐of‐the‐art ECRAMs. This study offers a promising approach to discover and design novel polymer materials for organic ECRAMs and demonstrates potential applications, taking advantage of mature knowledge basis on electrochromic materials and devices. [ABSTRACT FROM AUTHOR]

Electrochromism is a unique phenomenon based on the ability to change the optical properties or color of a material when an external potential is applied. Conventional electrochromic materials are based on inorganic materials. In particular, transition metal oxides, such as tungsten oxide and molybdenum oxide, are extensively investigated for use in commercial electrochromic devices (ECDs). However, these devices have several drawbacks including single color change, expensive materials, and a slow switching speed. To overcome these challenges, new substitute materials need to be investigated with the advantages of multicolor, fast response, low cost, ease of processing, and environmentally friendly materials. Among the many great candidates, conducting polymers (CPs) have emerged as a prominent approach. In this review, the current state‐of‐the‐art development of ECDs based on the three most popular CPs, namely, polyaniline, polypyrrole, and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate, is introduced, with emphasis on their synthetic approaches and electrochromic performance. [ABSTRACT FROM AUTHOR]

Most redox systems generally cannot avoid the involvement of open‐shell species upon generating multiply charged species, which often reduces reversibility in multi‐color electrochromic systems. In this study, we newly synthesized octakis(aminophenyl)‐substituted pentacenebisquinodimethane (BQD) derivatives and their hybrids with alkoxyphenyl analogues. Thanks to apparent two‐electron transfer accompanied by double dramatic changes in the structure of the arylated quinodimethane skeleton, the dicationic and tetracationic states were generated and isolated quantitatively because of the negligible steady‐state concentration of intermediary open‐shell species such as monocation or trication radicals. When two electrophores with different donating abilities are attached to the BQD skeleton, a dicationic state with a different color can be isolated in addition to the neutral and tetracationic states. For these tetracations, an interchromophore interaction induces a red‐shift of the NIR absorptions, thus realizing tricolor UV/Vis/NIR electrochromic behavior involving only closed‐shell states. [ABSTRACT FROM AUTHOR]

The present era has seen tremendous demands for low‐cost electrochromic materials for visible‐region multicolor display technology, paper‐based, flexible, and wearable electronic devices, smart windows, and optoelectronic applications. Towards this goal, the authors report large‐scale, high‐yield and robust polyelectrochromic devices fabricated on rigid to flexible ITO substrates comprising novel anthracene containing viologen, (1,1″‐bis(anthracen‐9‐ylmethyl)‐[4,4″‐bipyridine]‐1,1'‐diium bromide, abbreviated as AnV2+), and polythiophene (P3HT). Interestingly, the devices show three states of reversible visible color in response to the applied bias, sub‐second to second switching time (0.7 s/1.6 s), high coloration efficiency (484 cm2/C), and longer cycling stability up to 9,000 s (3,000 switching cycles). Introduction of the anthracene moieties to viologen inhibits the formation of an undesired dimer of cation radicals in response to the applied bias, otherwise the device's color‐switching would be hampered when the bias polarity is reversed. The fabricated electrochromic devices are tested with commercially available low‐cost cells to perform—a unique approach toward practical applications. The computational study facilitates the understanding of experimental results. Alternating current (AC)‐based electrical impedance spectroscopy reveals that P3HT facilitates enhanced charge transfer to AnV2+. This work shows CMOS compatibility and can pave the way for developing cost‐effective flexible and wearable electrochromic devices. [ABSTRACT FROM AUTHOR]

Localized surface plasmon resonance (LSPR) is attractive to fabricate visible (VIS) and near‐infrared (NIR) dual‐band electrochromic materials. However, the introduction of the LSPR effect in the available dual‐band electrochromic materials can only be manifested to the spectral enhancement in the NIR region, and difficult issues of electrochromic materials such as low coloration efficiency and unsatisfactory long‐term cycling durability still remain. Here, a dual‐band electrochromic thin film consisting of a 2D ordered macroporous (2DOM) Au LSPR layer and a poly(3,4‐(2,2‐dimethylpropylenedioxy)thiophene) (PProDot‐Me2) electrochromic layer is presented, where LSPR and electrochromism interact in a complementary fashion. The 2DOM Au exhibits LSPR effect at wavelengths of 550 and 1700 nm, leading to a unique electrochromic performance improvement of the film in both of the VIS and NIR spectral regions. Large optical modulation, rapid switching speed, high coloration efficiency, and long‐term durability are achieved due to the collective effect of the near‐field enhancement of the 2DOM Au and the reduced bandgap of PProDot‐Me2. These advantages can be well retained in the dual‐band electrochromic device using the 2DOM Au/PProDot‐Me2 films as the electrochromic layers. This work provides new ideas for designing LSPR‐based devices, especially dual‐band electrochromic materials and devices, both experimentally and theoretically. [ABSTRACT FROM AUTHOR]

Electrochromic devices (ECDs) with adjustable transmittance have opened new opportunities to the development of smart windows for energy-efficiency building. However, the switching between colored and bleached state of conventional ECD will bring extra energy consumption, the design of highperformance ECD with low consumption is still an elusive goal. To address this issue, a self-driven and energy-saving Ni anode-based ECD using Prussian blue as electrochromic material is developed. During the day, it can be colored by solar energy. By contrast, it can spontaneously bleach when the ECD's anode and cathode are short-circuiting using the internal redox potential during the night. It is worth noting that no extra energy is inputted in the coloring-bleaching cycle. In comparison with the ECD using electrolyte with high Ni2+ (K+:Ni2+ = 1:9) or high K+ (K+:Ni2+ = 9:1) concentration with poor optical contrast and cyclic stability (failed <100 cycles), the Ni-based ECD with the electrolyte containing equal amount of K+ and Ni2+ exhibits a high optical contrast (39.45%), good coloration response time (6 s), and excellent stability (1000 cycles). These properties suggest that the Ni-based electrochromic configuration is expected to be a catalyst for the development of energy-storage EC smart window in the future. [ABSTRACT FROM AUTHOR]

The 4‐[5‐(undecylthio)‐1,3,4‐oxadiazol‐2‐yl)phenol (3)and 4‐(4‐(5‐(undecylthio)‐1,3,4‐oxadiazol‐2‐yl)phenoxy)phthalonitrile (5)were prepared viasubstitution reactions. Metallo‐phthalocyanines (6–9) were obtained by the cyclotetramerization of the phthalonitrile (5). The structures of novel compounds were verified using IR, 1H‐NMR, mass, UV‐Vis methods. Electrochemical characterization of synthesized MPcs (6–9)was carried out by the CV and SWV techniques in DCM/TBAP electrolyte. While MnClPc and CoPc complexes exhibited metal‐based and ring‐based reduction redox couples, CuPc and NiPc gave two ring‐based reduction redox couples. Spectroelectrochemical measurements were performed to observe the color transition during the reduction and oxidation reactions. Thus, the potentials of using the complexes as electrochromic materials were investigated. The CoPc gave the Q band at 667 nm with a shoulder at 663 nm. When the potential was applied to the cell, the intensity of Q band decreased with a shift in wavelength (from 667 nm to 663 nm). In addition, the natural turquoise color (x=0.2720, y=0.3366) of CoPc turned to greenish blue color (x=0.3080, y=0.3461). During the oxidation reactions, CuPc and NiPc gave ring‐based oxidation species. The intensity of Q bands decreased without shift. As a result of the in‐situ spectroelectrochemical measurements, it was observed that CuPc and NiPc, have sharper color transitions and have the potential to be used as electrochromic materials. [ABSTRACT FROM AUTHOR]

The electrochromic detection of latent fingermarks on polished or unpolished, flat or curved metal surfaces is described using electrochromic material, 1,1'‐dibenzyl‐4,4'‐bipyridinium dichloride. The surface area covered by fingermarks acts as an insulating mask, causing 1,1'‐dibenzyl‐4,4'‐bipyridinium dichloride to change color and produce inversed images of the fingermark. By changing the applied potential, the optical properties of 1,1'‐dibenzyl‐4,4'‐bipyridinium dichloride can be continuously and reversibly adjusted to optimize the visual contrast of fingermarks, so as to realize the detection of latent fingermarks on stainless steel surface. It is demonstrated that the fabricated electrochromic devices can detect the fingermarks on these types of surfaces within twenty seconds at −1.0∼−2.0 V. This work can qualify as a tangible improvement in fingermark detection of the natural fingermarks on the never‐cleaned (more than 3 years) and curved surfaces of daily‐used container, e. g. cup, and the handle of cleaning tool, mop. [ABSTRACT FROM AUTHOR]

Electrochromic effect has been discovered in many materials with a wide range of applications from visible to infrared, such as smart windows, electronic displays, infrared camouflage, and color‐changeable tactile sensor. However, conventional electrochromic materials cannot meet the growing demand for electrochromic performance in terms of optical contrast, response time, durability, color diversity, and flexibility, which slows down developments in this area. This is mainly due to the limited number and variety of electrochromic materials. In strong contrast, nanoarchitectonics of 2D materials with atomically thin thickness, large lateral size, and diversified series can be an effective way to address these issues and improve the electrochromic performances. This review highlights the recent achievements of emerging 2D electrochromic materials, namely covalent organic frameworks, coordination nanosheets, and transition metal carbides/nitrides/carbonitrides (MXenes). The structures, electrochromic performances and their structure–performance relationship, and future challenges of these materials have been systematically explored. This review can pave a new avenue for the promotion of the nanoarchitectonic 2D materials for the up‐scaled practical electrochromic applications. [ABSTRACT FROM AUTHOR]

Poly(3,4‐ethylene dioxythiophene) (PEDOT) is a promising electrochromic material in many practical application, such as smart windows and displays. However, there are still difficulties in currently realizing green manufacturing, high coloration efficiency, and rapid response. Herein, in‐situ electrochemical polymerization of PEDOT:PSS/Reline films was suggested in aqueous solution. Deep eutectic solvents (DES) composed of choline chloride and urea (Reline) were employed as green solvents in reaction system and used as dopants for the PEDOT:PSS. The as‐prepared PEDOT:PSS/Reline films exhibited remarkable electrochromic properties, including great ion diffusion coefficient, fast reaction time (coloration response time was 1.4 s), prominent transmittance modulation (38%), high coloration efficiency (223 cm2/C) and excellent cyclic stability. Impressively, doping of Reline cannot only provide a green polymerization environment, but also significantly boost the electrochromic properties. [ABSTRACT FROM AUTHOR]

Two reported D‐A‐D monomers based on 3,4‐ethylenedioxythiophene (EDOT) were selected for electrochemical copolymerization to obtain copolymer film, named pRG. Then, a soluble polymer poly[3,4‐ethylenedioxythiophene‐alt‐3,4‐bis([2‐ethylhexyl]oxy)thiophene] (pEA) based on the EDOT derivative was screened out, which is complementary to the absorption trough of the pRG film in visible region and matched with its working potential. The bilayer composite film pRG/pEA was obtained by spinning pEA basement membrane on fluorine doped tin oxide (FTO) coated glass surface, and then in situ electrochemical polymerization of pRG film. Compared to the pRG monolayer film, the bilayer composite film shows a more saturated black color in the neutral state and significant improvement on cyclic stability (only decreased by 1.7% after 250 cycles, while pRG film decreased by 17.1%). The introduction of pEA buffer layer not only achieves the full spectral absorption of the composite film in the visible region, but also significantly improves the cyclic stability of the bilayer composite film. The assembled EC prototype device based on the pRG/pEA composite film exhibits a "black to high transmission" reversible switch. Finally, this method combining electrochemical copolymerization, spin‐coating, lamination and other methods provides a new research idea for designing and preparing black to transmissive electrochromic materials. [ABSTRACT FROM AUTHOR]

Molecular assembly induced by metal‐terpyridine‐based coordinative interactions has become an emergent research topic due to its ease of synthesis and diverse applications. This article highlights recent significant developments in the metal‐terpyridine‐based supramolecular architectures. At first, the design aspect of the molecular building blocks has been described, followed by elaboration on how the ligand backbone plays an important role for achieving different dimensionalities of the resulting assemblies which exhibit a wide range of potential applications. After that, we discussed different synthetic approaches for constructing these assemblies, and finally, we focused on their significant developments in three specific areas, viz., electrochromic materials, catalysis and a new application in wastewater treatment. In the field of electrochromic materials, these assemblies made important advancements in various aspects like sub‐second switching time (<1 s), low switching voltage (<1 V), increased switching stability (>10000 cycles), tuning of multiple colors by using multimetallic systems, fabrication of charge storing electrochromic devices, utilizing and storing solar energy etc. Similarly, the catalysis field witnessed application of the metal‐terpyridine assemblies in C−H monohalogenation, heterogeneous Suzuki‐Miyaura coupling, photocatalysis, reduction of carbon dioxide, etc. Finally, the environmental application of these coordination assemblies includes capturing Cr(VI) from waste water efficiently with high capture capacity, good recyclability, wide pH independency etc. [ABSTRACT FROM AUTHOR]

Electrochromism is a reversible color change triggered by the external electrical field, which can be utilized in smart windows, displays, etc. The ability to display multiple colors in a single electrochromic device is highly beneficial for the versatile applications of the electrochromic technique. Yet, achieving the ability to adopt multiple colors in one electrochromic device has proven to be a challenging task by merely using the conventional chemical structure engineering of the electrochromic materials. In this study, a thermochromic electrolyte is introduced. A multicolor electrochromic prototype device is produced by integrating the thermochromic engineered electrolyte together with electrochromic material in which both can independently contribute to the coloring of the device. This "color palette" strategy gives an additional degree of freedom and extensive flexibility to the design of multicolor electrochromic devices. It introduces a new pathway for producing multicolor electrochromic devices and removes a bottleneck imposed by conventional strategies merely depending on the electrochromic material structure engineering. Moreover, it inspires further development of electrolytes, that share the responsibility of tuning the optical properties of electrochromic devices together with the electrochromic materials, thereby accelerating and diversifying the applications of electrochromics in industry. [ABSTRACT FROM AUTHOR]

Al3+‐based electrochromic devices (ECDs) are expected to substitute Li+‐based ECDs as the next‐generation smart windows options. Compared to Li+, Al3+ possess large quantities in the earth and safety, while the smaller ionic radius and three‐electron redox mechanism can break the capacity bottleneck of inorganic electrochromic materials (ECM). However, limited by the strong electrostatic interaction between Al3+ with ECM and the lack of matching counter electrodes, the research on Al3+ is still focused on three‐electrode system without applications in ECDs. Different from conventional complementary structure, the ECM/redox/CCE (catalytic counter electrode) structure is introduced to enhance the kinetics (from 1.56 × 10−11 to 9.45 × 10−11 cm2 s−1) of the Al3+ intercalation/extraction process. Based on this structure, Al3+‐based ECDs achieve a series of excellent properties: a) almost total absorption of visible and near‐infrared waveband (T500–1500 nm ≈0%) under −1.0 V; b) ultra‐low driving voltage (53% transmittance modulation under −0.1 V); c) excellent memory effect with the presence of redox couple; d) wide range of color modulation capability (yellow, green, blue, and black); e) outstanding energy efficiency. Moreover, the possibility of Na+ as an alternative to Li+ is also verified and Na+‐based ECDs exhibit comparable electrochromic properties to Li+‐based ECDs. [ABSTRACT FROM AUTHOR]

Electrochromic materials can tune the illumination and heat exchange of a building with the environment and thereby save energy in lighting, heating, and air conditioning in a cost‐effective way, which is vital in realizing carbon neutrality. 2D frameworks such as coordination nanosheets (CONASHs) that are widely explored for a wide range of applications in energy storage and conversion can be a cluster of novel electrochromic materials. In this work, a series of transition metal benzenehexathiol (TM‐BHT) CONASHs are theoretically investigated via first‐principles simulations. During ion intercalation and deintercalation in TM‐BHTs, changes in lattice structures, lithium diffusion barriers, atomic charges, bond strength, and electronic properties are explored in‐depth. The incurred changes are then correlated with critical electrochromic properties, including the transmittance adjustment ranges in the visible light, near‐infrared, solar spectrum, and mid‐infrared. Among the various TM‐BHT systems, Cu‐BHT and Ag‐BHT are the most promising broadband electrochromic materials for optical and thermal management in the wavelength range from visible to mid‐infrared. The theoretical guidance from this work paves a new path toward electrochromic applications of CONASHs that exploit the versatility of these 2D materials. [ABSTRACT FROM AUTHOR]

Electrochromic small molecules suffer from the difficult film processibility and serious dissolvability at their oxidation state, which greatly limit their applications in electrochromic areas. Here, well‐defined electrochemical polymer structures, pCZ‐FSQ and pCZ‐FEQ, are obtained by taking advantage of the unique electrochemical dimerization of carbazole, and low redox‐potential phenothiazine and phenoxazine groups are introduced as an electrochromic color‐changing unit with the interruption of conjugation between them via an alkyl chain linkage. The obtained polymer films pCZ‐FSQ and pCZ‐FEQ are composed of the independent dimeric carbazole and organic small molecule units. Finally, they exhibit outstanding electrochromic properties with optical contrast of more than 50%, switching time of less than 1 s, excellent stability (over 500 cycles of optical stability), and ultrahigh coloration efficiency (276 cm2 C−1 for pCZ‐FSQ, 384 cm2 C−1 for pCZ‐FEQ). This is thought to be greatly attributed to the well‐defined electrochemical polymer structures with dual electrochromic color‐changing properties of both phenothiazine/phenoxazine and dimeric carbazole. This can also provide some implications for the future in‐depth study of small molecule electrochromism and the solution to the problem of difficult processing of small molecules. [ABSTRACT FROM AUTHOR]

The development of bistable electrochromic materials is a promising way to reduce the energy consumption of displays. However, bistable devices with ideal implementation schemes and electrochromic performance still remain challenging due to the inherent limitations of existing electrochromic materials. Herein, a theory of "hydroxyl‐acids" assisted improvement of electrochromic rate and bistability of fluorane dyes is proposed and applied to solid‐state electrochromic devices. 80% hydroxypropyl acrylate‐20% methyl methacrylate copolymer‐based electrochromic film prepared by the theory of "hydroxyl‐acids" has a higher electrochromic rate (4.1 times) and bistability (5.4 times) than traditional PMMA‐based electrochromic films in the device. In addition, the optimum device is obtained by optimizing each layer component content of the device. The novel electrochromic device has good overall performance, including coloring time (7.5 s), transmittance change (>70%), coloration efficiency (872 cm2 C‐1), bistability (50 h), and reversibility (1,000 cycles). The theory of "hydroxyl‐acids" is suitable for a variety of fluorane dyes, and polychromatic bistable electrochromic windows are developed. [ABSTRACT FROM AUTHOR]

In recent years, the research on electrochemical devices, especially the promising electrochromic material, is gradually in a wide range of application. But there is few corresponding research about specific industrial manufacturing. The paper starts from the structure of small and medium-sized intelligent factories and designs a system framework optimized by blockchain technology. It connects the electrochromic material quality control module with the product traceability module through a blockchain-based server, which not only ensures the production quality but also effectively improves the product supply chain, which is significant for the development of the electrochromic field. [ABSTRACT FROM AUTHOR]

Previous work has reported the synthesis of donor–acceptor–donor molecules based on dibenzophenazine acceptor group, presenting thermally activated delayed fluorescent (TADF) properties and their application in the assembly of highly efficient electroluminescent devices. Herein, we focus on the characterisation of charge carrier species through UV‐Vis‐NIR spectroelectrochemical and potentiostatic EPR techniques, in addition to the investigation of electropolymerisation properties of some compounds depicted in this study. The promising electrochromic features of both small molecules and conjugated polymers led to the assembly and investigation of electrochromic devices, evidencing the materials' versatility, applied in such different approaches as electrochromic windows and electroluminescent devices. Furthermore, the assembled OLEDs provided high efficiencies, with small roll‐off, EQEs up to 20.5 % and luminance values up to 85 000 cd/m2. [ABSTRACT FROM AUTHOR]

Novel organic redox systems that display multistage redox behaviour are highly sought‐after for a series of applications such as organic batteries or electrochromic materials. Here we describe a simple strategy to transfer well‐known two‐electron redox active bipyridine and phenanthroline architectures into novel strongly reducing four‐electron redox systems featuring fully reversible redox events with up to five stable oxidation states. We give spectroscopic and structural insight into the changes involved in the redox‐events and present characterization data on all isolated oxidation states. The redox‐systems feature strong UV/Vis/NIR polyelectrochromic properties such as distinct strong NIR absorptions in the mixed valence states. Two‐electron charge–discharge cycling studies indicate high electrochemical stability at strongly negative potentials, rendering the new redox architectures promising lead structures for multi‐electron anolyte materials. [ABSTRACT FROM AUTHOR]

Dual‐band electrochromism is a phenomenon where materials can independently regulate the transmittance of visible (VIS) and near‐infrared (NIR) light. Owing to their bistability, low energy consumption, and independent control over VIS and NIR regions, dual‐band electrochromic (EC) devices have been of great significance to fully harnessing VIS and NIR light and building an energy‐saving society. The past several years have witnessed the efforts put in developing novel EC materials to improve their dual‐band optical performance through altering their composition, structural, and physicochemical features, which determine the optical behavior of dual‐band EC devices. In this review, the concept, significance, working principle, and key influence factors of dual‐band electrochromism are briefly introduced. Next, the up‐to‐date progress of dual‐band EC materials including inorganic, organic, and composites materials are summarized, with a focus on material design, device fabrication, and performance optimization. Finally, the challenges and perspectives of dual‐band EC materials and devices are also presented. [ABSTRACT FROM AUTHOR]

In the era of intelligent automation, smart energy storage devices are highly sought after due to their capability to reveal their state of charge by a visual color change. In principle, this is typically obtained by integrating electrochromic materials which demonstrate a change in optical band gap during redox reactions as electrodes in batteries/supercapacitors. Among various electrochromic materials, transition metal oxides have received significant interests because of their natural abundance, good cycling stability and high electrochemical response. In this work, metal organic framework (MOF) derived carbon embedded NiO (NiO@C) demonstrates very fast switching speeds of ∼1.4 s for coloration and ∼3.5 s for bleaching with high coloration efficiency of ∼135.16 cm2/C. These aspects make MOF‐derived NiO@C a potential candidate to be integrated as a smart positive electrode in an alkaline zinc (Zn) battery to construct a rechargeable Zn−NiO electrochromic (EC) battery. The Zn−NiO EC battery delivers an average voltage of ∼1.84 V and demonstrates a specific capacity of ∼85.3 mAh/m2 at 0.1 mA/cm2 current density. It visually displays its energy storage level by changing its color from dark brown (charged state) to colorless (discharged state), making it a potential candidate in smart windows and energy storage displays. [ABSTRACT FROM AUTHOR]

The rapidly expanding field of intelligent ion‐based devices has increased interest in the use of anodically‐coloring electrochromic nickel oxide thin films. The degradation and coloration mechanisms of nickel oxide, especially in Li+‐based electrolytes, are yet to be well understood. Herein we demonstrate that high potentials have a positive effect on the electrochromic performance of nickel oxide thin films. Our studies show that Cl− ions involved in the electrochromic process have been accumulated on the surface of the films upon extended electrochemical cycling, as confirmed by the X‐ray Photoelectron Spectroscopy. X‐ray Absorption Spectroscopy results indicate that the formation of Ni−Cl bonds influence the structural distortion and that the hybridization between Ni 3d and O 2p orbitals has been enhanced. Density functional theory calculations provide further insights for the band structures and how they change when Li+ and Cl− are adsorbed. Our results have revealed the underlying physical and chemical origins associated with the coloration mechanism and the degradation of nickel oxide thin films and highlighted the key role of Cl−. These new understandings will advance the development of superior electrochromic materials and the designing of efficient and durable electrochromic devices, both experimentally and theoretically. [ABSTRACT FROM AUTHOR]

Dual‐band electrochromic (EC) smart windows, which can selectively modulate visible (VIS) and near‐infrared (NIR) light are widely regarded as one of the most attractive options to drastically reduce energy consumption in modern buildings. However, dual‐band EC smart windows still face many challenges such as weak modulation selectivity between VIS and NIR bands, low switching speed, poor durability, and high cost. Here, inspired by pine needles, a unique pine‐needle‐like (PNL) W18O49/TiO2 heterostructure is rationally constructed with W18O49 nanothorns (as branches) and TiO2 nanofibers (as backbones). The PNL‐W18O49/TiO2 heterostructures exhibit superior dual‐band EC performance in both VIS and NIR bands, which can block up to 81.4% of the VIS light at 633 nm and 91.3% of NIR at 1800 nm, and they also show extremely short bleaching/coloring time (0.9/1.2 s) and excellent stability (85% of capacity retention after 20 000 cycles) in a narrow potential window of −0.8 to 0.6 V. Besides, abundant patterned EC layers on a fluorine‐doped‐tin‐oxide‐coated conductive glass and flexible polyester conductive films can also be realized. This work provides an effective way for dual‐band EC materials' design and their further development in smart windows and intelligent displays. [ABSTRACT FROM AUTHOR]