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A series of electrochromic π-conjugated polymers which cover almost full-colour gamut are designed. This is the first time to deeply explore the multicolour electrochromic mechanism in this material system. Based on a fine adjustment on their energy level structures, which are further developed into flexible electrochromic prototype devices with dynamic multicolour displays. [Display omitted] Multicolour electrochromic materials have been considered as a promising alternative to achieve dynamic full-colour tuning towards next-generation electronic display technology. However, the development of electrochromics with wide colour gamut and subtle multicolour tunability still remains challenging due to inflexible energy level structures in intrinsic active materials. Herein, the electrochromic π-conjugated polymers with rich and subtle colour tunability were designed and developed based on a fine adjustment on the energy level structures. The chromatic transition covers almost full-colour gamut, and each colour scheme has a rich variety of categories stemming from versatile hues, chromas and lightnesses. Moreover, the multicolour π-conjugated polymers also demonstrate superior overall electrochromic performance, including fast switching (∼1.0 s), high colouration efficiency (160.4 cm2 C−1@550 nm) and good reversibility (over 90 % retention after 10,000 cycles). As a proof of concept, ultrathin and flexible prototype devices are developed by utilizing the multicolour π-conjugated polymers as electrochromic active layer, exhibiting a wide colour gamut and highly saturated multicolour tunability. The design principles proposed in this work may also be applicable to diverse optoelectronic applications. [ABSTRACT FROM AUTHOR]

The study of electrophysiological signals is crucial for understanding neural functions and physiological processes. Electrophysiological recordings offer direct insights into electrical activity across cellular membranes, aiding in diagnosing and treating neurological disorders. Different from the conventional recording method based on electrical signals and the genetically encoded with fluorescent proteins methods, this review explores label-free mechanisms for optically recording electrophysiological signals: electrochromic materials, surface plasmon resonance (SPR) responses, quantum dots (QDs), and semiconductor-based optoelectronic sensors. The sophistication and limitations of each technology have been discussed, providing insights into potential future directions in this field. Electrochromic materials change optical properties through redox reactions induced by voltages, offering high signal-to-noise ratios and rapid response capabilities. However, these materials have limited biocompatibility and stability. SPR technology modulates signals in response to local changes in electrical potential, achieving high sensitivity. However, challenges such as scattering noise and electro-optic effects still need to be addressed. QDs utilize their photoluminescent properties for high sensitivity and resolution, but concerns about connection efficiency and biocompatibility remain. Semiconductor optoelectronic technologies offer rapid response times, wireless functionality, and integration potential. However, improvements are needed in terms of toxicity, compatibility with biological tissues, and signal amplification and processing. These methods have advantages in neuroscience, medical diagnostics, and biological research, including rapid response, high sensitivity, and label-free monitoring. By combining different optical recording techniques, the performance of voltage imaging can be optimized. In conclusion, interdisciplinary collaboration and innovation are essential for advancing the optical recording of electrophysiological signals and developing diagnostic and therapeutic approaches. [ABSTRACT FROM AUTHOR]

Viologen-based organic electrochromic materials have been extensively studied due to their excellent electrochromic performance. Nevertheless, the dimerization of the radical cation state will destroy the reversibility of viologens and result in poor stability of the electrochromic device (ECD). Herein, two π-extended viologen derivatives (Spr-MPTT and Sbu-MPTT) are synthesized by inserting a thiazolo[5,4-d]thiazole unit between bipyridine moieties and N-bisubstituted with alkyl sulfonate groups. All-in-one hydrogel ECDs are assembled using Spr-MPTT or Sbu-MPTT and ferrocene modified by a water-soluble group. The Spr-MPTT-based ECD exhibited alternating color change between yellow-green and violet, while the Sbu-MPTT-based ECD displayed alternating color change between yellow-green and purple at 1.0/0 V pulse voltage. The extended conjugation of the viologen chromophore confers these devices with visible-NIR absorption and good cyclic stability. Their optical contrasts at 535 nm are 54.85% and 60.17%, respectively, for Spr-MPTT or Sbu-MPTT based ECD. These results demonstrate their potential application in electrochromic hydrogel smart windows. [ABSTRACT FROM AUTHOR]

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]

By functionalizing various polyphenyl nuclei with ester groups, five kinds of polyphenyl benzoate based electrochromic materials (M1–M5) are synthesized and characterized. These materials show typical aggregation-induced emission and aggregation-enhanced emission in water/N-methylpyrrolidone, good electrochemical properties, and an obvious electrochromic phenomenon. In the process of electrochemical reduction, each material shows distinct and well-separated redox couples, the introduction of ester moieties makes electron transfer much easier compared to the polyphenyl nuclei, and the synergistic effect of the ester group and polyphenyl structure reduces the LUMO level of the corresponding polyphenyl benzoates. In contrast, the polyphenyl nuclei markedly affect their electrochromic properties, and the electrochromic devices based on M1–M5 exhibit five different colored states. By combining with density functional theory calculations, it is found that an appropriate amount of benzene rings in the central benzene cores (M2 and M4) can effectively improve the coloration efficiency, response time, and switching stability; fewer benzene rings in the central benzene core (M1) cannot achieve stable conjugation of the material in the reduced state, while an excess of benzene rings in the central benzene core (M5) leads to excessive molecular volume, and this will lead to space congestion and is not beneficial for electron transfer. The application of M1–M5 in multi-colored functional display devices is explored, indicating its potential application prospect in display fields. [ABSTRACT FROM AUTHOR]

Developing high performance electrochromic materials with energy storage function is essential for next generation smart display devices. Here, a double-layer NiO film (NiO-dl) was prepared by compositing the defective NiO (d-NiO) with the crystalline NiO (c-NiO), with a unique prismatic nanosheet array structure. The synergistic effect as well as the large active area with defect sites and valence modulation brought about by the (111) crystal plane-oriented growth of the sputtering process can promote the intercalation and extraction of OH− and Li+, which greatly enhances the electrochemical properties. Specifically, the NiO-dl film achieves a prominent optical modulation covering visible region (89.5 % in KOH and 64.8 % in Li+ electrolyte at 550 nm) and near-infrared region (54.5 % in KOH and 37.2 % in Li+ electrolyte at 1000 nm), a high transparent bleached state (92.7 %), a superior coloring efficiency (44.7 cm2 C−1) and robust stability (95.1 % retention after 1000 cycles). A high area capacitance of 99.5 mF cm−2 at 0.14 mA cm−2 with the promising cycling performance exhibits the supercapacitor characteristics. The comprehensive evaluation of the NiO-dl film demonstrated its exploitative potential application in electrochromic energy storage fields. [Display omitted] • The approach focuses on designing multifunctional electrochromic energy storage materials. • A NiO-dl film with (111) crystal plane-oriented growth is prepared and the formation mechanism is studied. • The improved properties stem from Ni3+ ions, Ni vacancies and synergistic effect of crystalline and defective NiO. • The NiO-dl film exhibits prominent optical modulation and promising supercapacitance. [ABSTRACT FROM AUTHOR]

Electrochromic technology plays a pivotal role in various industries, offering significant benefits in energy efficiency and sustainability. By efficiently modulating sunlight, it reduces dependence on traditional climate control systems, thus decreasing overall energy consumption. Among electrochromic materials, tungsten oxide (WO 3) is highly favored for its outstanding stability and superior optical modulation amplitude. However, the escalating demands of commercial applications necessitate enhancements in electrochromic performance, achievable through doping or composite designs. This study investigates the electrochromic characteristics of novel niobium tungsten oxide (Nb 18 W 16 O 93) thin films, employing a gel electrolyte and examining their structural, optical, and electrochemical attributes. Compared to pure WO 3 , the Nb 18 W 16 O 93 -based electrochromic device exhibited a significant optical modulation of 55.1% in the visible spectrum and 31.3% in the near-infrared region. The gel-based device not only provides safety benefits over liquid electrolytes by mitigating leakage risks but also features rapid switching response times, with a coloration duration of 3.9 s and a bleaching interval of 3.6 s. Moreover, the device showcases exceptional long-term stability, retaining a ΔT of nearly 72% after 10,000 cycles. [ABSTRACT FROM AUTHOR]

The various physical properties recently induced by solid-state electrochemical reactions must be comprehensively understood, and their mechanisms of action should be elucidated. Reversible changes in conductivity, magnetism, and colour have been achieved by combining the redox reactions of d metal ions and organic materials, as well as the molecular and crystal structures of solids. This review describes the electrochemically driven physical properties of conductors, magnetic materials, and electrochromic materials using various electrochemical devices. [ABSTRACT FROM AUTHOR]

Recently, the Fabry–Perot (F–P) cavity electrochromic devices, which are constructed by combining nano-size inorganic electrochromic material WO 3 and reflective metal layers, have attracted considerable attention due to their potentials in the fields of dynamic multicolor displays and active camouflage. However, in the few studies that have been reported, the peak reflectance of flexible F–P cavity multicolor electrochromic devices in the visible wavelength band is generally lower than 30 %, which limits their reflective display and camouflage effects in high-brightness environments. Thus, we have combined multicolor reflective electrochromic electrodes in WO 3 /Au asymmetric F–P nanocavity constructed by magnetron sputtering on a Nylon 66 porous substrate with a highly transparent UV-cured gel electrolyte and a PET plastic sealing procedure. As a result, a flexible and dynamic multicolor electrochromic skin with high reflectance (R max ＞50 %) and excellent flexibility (bending radius of 4 mm) has been fabricated. The WO 3 electrochromic layer at the top works as the dynamic dielectric layer in the broadband absorption Fabry–Perot cavity, and the inert metal Au layer at the bottom works as the reflective layer. The WO 3 /Au asymmetric F–P cavity can acutely capture the variation in optical constants of WO 3 due to the thickness change and electric-driven effects. This cavity facilitates the selective reflection and absorption of the energy distribution of the spectrum after the induced interferometric resonance. As a result, the cavity exhibits a rich array of structural colors, including ocher, taupe, yellow, orange, green, and violet. The electrochromic skin exhibits a fast switching time and maintains 99.43 % of the optical modulation amplitude (ΔR) after 110 coloring/bleaching cycles. It provides a potential option in the field of flexible high-brightness reflective displays and dynamic camouflage in the future. [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]

We performed an electrochromic investigation to optimize the composition of reactive magnetron-sputtered mixed layers of zinc oxide and tin oxide (ZnO-SnO2). Deposition experiments were conducted as a combinatorial material synthesis approach. The binary system for the samples of SnO2-ZnO represented the full composition range. The coloration efficiency (CE) was determined for the mixed oxide films with the simultaneous measurement of layer transmittance, in a conventional three-electrode configuration, and an electric current was applied by using organic propylene carbonate electrolyte cells. The optical parameters and composition were measured and mapped by using spectroscopic ellipsometry (SE). Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) measurements were carried out to check the SE results, for (TiO2-SnO2). Pure metal targets were placed separately from each other, and the indium–tin-oxide (ITO)-covered glass samples and Si-probes on a glass holder were moved under the two separated targets (Zn and Sn) in a reactive argon–oxygen (Ar-O2) gas mixture. This combinatorial process ensured that all the compositions (from 0 to 100%) were achieved in the same sputtering chamber after one sputtering preparation cycle. The CE data evaluated from the electro-optical measurements plotted against the composition displayed a characteristic maximum at around 29% ZnO. The accuracy of our combinatorial approach was 5%. [ABSTRACT FROM AUTHOR]

This study explores the modeling, design, simulation, and testing of a new composite material designed for high-strength and high-temperature resistance in in-space optical mining, examining its properties at both the polymer and atomic/molecular levels. At the polymer level, the investigation includes mechanical and thermal performance analyses using COMSOL Multiphysics 6.1, employing layerwise theory, equivalent single layer (ESL) theory, and a multiple-model approach for mechanical modeling, alongside virtual thermal experiments simulating laser heating. Experimentally, porous Polyaniline (PANI) films are fabricated via electrochemical polymerization, with variations in voltage and deposition time, to study their morphology, optical performance, and electrochemical behavior. At the atomic and molecular levels, this study involves modeling the composite material, composed of Nomex, Kevlar, and Spirooxazine-Doped PANI, and simulating its behavior. The significance of this work lies in developing a novel composite material for in-space optical mining, integrating it into optical mining systems, and introducing innovative thermal management solutions, which contribute to future space exploration by improving resource efficiency and sustainability, while also enhancing the understanding of PANI film properties for in-space applications. [ABSTRACT FROM AUTHOR]

Prussian blue (PB), as a promising inorganic electrochromic material (ECM), has been widely used in smart windows, displays, sensors, etc. However, there are still many challenges for PB to achieve high electrochromic performance. Herein, we synthesized nitrogen-doped carbon dots-modified PB film (defined as PB@N-CDs) with a sandwich-like structure by a simple stepwise electrodeposition method. The carbon dots show an obvious advantage in ultrafast electron transfer ability, which can reduce charge loss during the transfer process, improve the electrochemical activity on both sides of PB, and thus facilitate a rapid electrochromic response. Furthermore, the surface of nitrogen-doped carbon dots contains multiple organic functional groups, which widen the movement path of K+ ions under electrostatic adsorption. Impressively, the PB@N-CDs film exhibits a short bleaching/coloring time (0.5/0.9 s) and a superior optical modulation range (78.6%). Particularly, the coloring efficiency has been significantly improved to 137.71 cm2/C (at 700 nm). All of these results open up new avenues for developing high-performance PB-based ECMs and promoting their applications in corresponding electrochromic devices (ECDs) and smart windows. [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]

Electrochromic materials enable the precise control of their optical properties, making them essential for energy-saving applications such as smart windows. This study focuses on the synthesis of molybdenum-doped niobium oxide (Mo-Nb2O5) thin films using a one-step hydrothermal method to investigate the effect of Mo doping on the material's electrochromic performance. Mo incorporation led to distinct morphological changes and a transition from a compact granular structure to an anisotropic rod-like feature. Notably, the MN-3 (0.3% Mo) sample displayed an optimal electrochromic performance, achieving 77% optical modulation at 600 nm, a near-perfect reversibility of 99%, and a high coloration efficiency of 89 cm2/C. Additionally, MN-3 exhibited excellent cycling stability, with only 0.8% degradation over 5000 s. The MN-3 device also displayed impressive control over color switching, underscoring its potential for practical applications. These results highlight the significant impact of Mo doping on improving the structural and electrochromic properties of Nb2O5 thin films, offering improved ion intercalation and charge transport. This study underscores the potential of Mo-Nb2O5 for practical applications in energy-efficient technologies. [ABSTRACT FROM AUTHOR]

Black-to-transparent electrochromism is hailed as the holy grail of organic optoelectronics. Despite its potential, designing black electrochromic materials that fully absorb visible light remains a significant challenge. Electroactive materials that simultaneously possess excellent cyclic stability, fast switching times, and high coloration efficiency are rare. In this study, we successfully designed copolymers that fully absorb the entire visible spectrum by judiciously selecting four types of monomers. We incorporated two types of polar side chains to synergistically enhance the ionic conductivity of the copolymers, thus improving the performance of electrochromic devices. Among these electrochromic devices, the P2-a device exhibits cycling stability exceeding 105 cycles, and the P2-c device demonstrates a coloring/ bleaching time of 0.82 s/0.86 s and achieves a coloration efficiency of 1078 cm²/C. This study proposes a strategy for designing and synthesizing high-performance black electrochromic copolymers. Black to transparent electrochromism is highly desirable for organic optoelectronics but design of black electrochromic materials that fully absorb visible light is challenging. Here, the authors report the synthesis of copolymers that absorb the entire visible spectrum by the rational design of their monomers. [ABSTRACT FROM AUTHOR]

Dual-band electrochromic windows have emerged as a promising approach to reduce building energy consumption. However, developing facile and effective method for preparing single-component dual-band electrochromic material remains a challenge. Herein, an in situ carbothermal reduction strategy was utilized to fabricate monoclinic oxygen-deficient tungsten oxide (WO 3-x) for high-performance dual-band electrochromism. Polyvinylpyrrolidone (PVP–K90) underwent transformation into amorphous carbon at high temperature, serving as the reducing agent embedded in the tungsten oxide film, and in situ inducing the formation of oxygen vacancies during annealing treatment. Lastly, the amorphous carbon was gasified without weakening the transmittance of WO 3-x film. The content of oxygen vacancies in WO 3-x could be modulated by controlling the added amount of PVP-K90. The intrinsic generation of oxygen vacancies not only obtained a strong local surface plasmon resonance (LSPR) absorption in near-infrared (NIR) range, but also improved lithium ion (Li+) diffusion in WO 3-x film. The WO 3-x electrochromic film exhibited excellent dual-band electrochromic performance in optical modulation, switching time, coloring efficiency, bistability, and cycle stability. Furthermore, the WO 3-x film was applied to electrochromic window to verify its available regulation in solar illumination and heat, indicating that the designed modification strategy has potential for developing a single-component dual-band electrochromic window with outstanding performance. [ABSTRACT FROM AUTHOR]

The interface mismatch between electrochromic materials and conductive layer seriously affects the cycle stability of electrochromic smart windows (ESW). However, it is difficult to improve the interface matching at the same time because of the different physical and chemical properties of anode and cathode materials. In this work, SnO 2 nanosheets are used as the interface modification layer between electrochromic materials and conductive layer. SnO 2 interface engineering significantly can improve the cycle stability of WO 3 film and Prussian blue (PB) film. The WO 3 /SnO 2 -PB/SnO 2 complementary ESW exhibits a high optical modulation of 60.2 % at 633 nm, fast response time (bleached/colored time = 8.5/2.5 s), and coloration efficiency of 91.7 cm2 C−1. The WO 3 /SnO 2 -PB/SnO 2 device can still maintain an optical modulation of 45.2 % after 2000 cycles, suggesting excellent long cycle stability. And the device shows the energy storage of 5.06 mF cm−2 at 0.1 mA cm−2, which can improve energy efficiency. The excellent electrochromic properties and energy storage suggests that SnO 2 interface engineering has a good application prospect in multi-functional ESW with excellent cycle stability. [ABSTRACT FROM AUTHOR]

This study reports the fabrication of electrochromic Ag decorated V 2 O 5 thin film by thermal evaporation method at 10−5 torr vacuum medium and the effects of the Ag doping to the V 2 O 5 matrix. Besides, the electrochromic capabilities and energy-saving characteristics of the films are also in the scope of this study. Structural and morphological properties are investigated by XRD, FESEM, and AFM. The films have a polycrystalline structure and a porous surface. FTIR and Raman spectra verify the molecular formation of the films. The performance of the electrochromic films is characterized by a variety of techniques such as cyclic voltammetry, chronoamperometry, chronocolumetry, and electrochemical impedance spectroscopy. The color of the films changes from yellow to green and then from green to blue in the range of −1.2 and + 1.0 V vs Ag/AgCl with a reversibility of 92.9 %. With the response times of t b = 13.6 s and t c = 9.4 s, an optical modulation of 51.7 % (from yellow to blue), and a coloration efficiency of 93.7 cm2 C−1, Ag:V 2 O 5 becomes an impressive electrochromic material produced by physical methods. Linear sweep voltammetry studies show that the photocurrent of both V 2 O 5 /ITO and Ag:V 2 O 5 /ITO electrodes increases under solar illumination. The supercapacitive performance of the film is investigated by cyclic voltammetry, and Ag:V 2 O 5 is an encouraging electrode material with a specific capacitance of 720.9 F g−1 at 5 mV s−1 scan rate. An equivalent circuit is fitted from the film Nyquist data and the results also confirm the positive contribution of Ag doping on the response times, energy saving, and photoresponse of V 2 O 5 thin film. In this regard, the produced electrodes are highly promising for potential applications in electrochromic, energy storage, and photovoltaic devices. [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]

In the article, electrochromic WO3 films were obtained from 25, 100, and 200 mM peroxytungstic acid (PTA) solution. A chronoamperogram of the cathodic reduction of tungsten oxide (WO3) through the stages of formation of a precursor film adsorbed on the surface of the ITO electrode and its subsequent staged reduction to WO3 and side formation of soluble reaction products is presented. The material yield of the WO3 film on ITO glass was within 50%, which is due to the parallel occurrence of side processes associated with hydrogen evolution and the reduction of tungsten complexes that were in the precipitation solution (WO3 reduction scheme). In this case, it was taken into account that thin WO3 films were the final product. The features of the synthesis of peroxytungstic acid have been studied. It has been shown that the reaction of W dissolution in 37% H2O2 proceeds exothermically. In this case, the reaction temperature reached 96°C within a few seconds, and its decline varied exponentially with the formation of reaction products. The dependence of the limiting current on the square root is obtained. The presented graphic dependence is characterized by linearity, while the beginning of the straight line does not coincide with the origin. The process of intercalation-deintercalation of protons (H+) (cathode-anode branches of CV) was a consequence of structural and reversible changes as a result of H+ intercalation. WO3 films obtained by electrochemical (cathodic) deposition can be recommended as an electrode material for electrochromic devices (cathode) and as a material for electrochemical sensors. Another promising direction is the development of a wide band gap anode based on WO3 for photovoltaic devices, which are energy efficient hydrogen generation systems. [ABSTRACT FROM AUTHOR]

Electrochromism is the process by which a material applies a small electrical signal to change the optical properties (transmittance, reflectance, absorptivity and emissivity) of the material reversibly or permanently through REDOX reactions resulting from ion and electron embedding/ejection. Metal-organic framework (MOF) are advantageous materials for electrochromic application due to their high porosity, large specific surface area and orderly pore structure, that promotes the adsorption of electrolyte ions, ion diffusion and charge transfer. In addition, MOFs possess a variety of ligands and metal centers, allowing for design of composition types and pore structure sizes. This grants them the advantages of both organic electrochromic materials, such as vivid colors and fast color transformation, and inorganic electrochromic materials, like high coloring efficiency and excellent stability. This paper reviews the current research progress of MOF electrochromic materials, including materials design, electrochromic properties, and application. [ABSTRACT FROM AUTHOR]

The increase in global temperature has led to a significant surge in energy consumption within the air conditioning industry, resulting in environmental deterioration. Electrochromic (EC) windows have emerged as a promising solution to address these challenges. Vanadium pentoxide (V2O5) stands out among all metal oxide materials due to its remarkable EC properties, including substantial Li+ ion insertion capacity and multicolor capabilities. Despite the potential of V2O5, there remains a lack of comprehensive research on the structural and optical properties of V2O5 films with varying thicknesses. Therefore, this study aims to investigate the structural and optical properties of V2O5 thin films with thicknesses ranging from 46 to 344 nm. By employing the sol-gel spin coating method, V2O5 thin films were fabricated and analyzed using X-ray diffraction (XRD) spectroscopy and ultraviolet-visible (UV-Vis) spectrophotometry. The fabricated V2O5 thin films with thicknesses of 46-274 nm demonstrated an average film transparency of 83%. XRD analysis further revealed that the V2O5 thin films reached their peak crystallinity at a thickness of 344 nm. Moreover, CV analysis revealed that the V2O5 device, with a thickness of 274 nm, exhibited a cathodic peak current of -1.63 mA, indicating its excellent ability to facilitate Li+ ion diffusion. Additionally, CA measurements displayed a high optical modulation of 37.78%. Ultimately, this research contributes to the development of energy-efficient solutions for sustainable environmental practices. [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]

Owing to their electrochromic performance, hierarchically structured transition-metal oxides have promising energy-saving device applications. In this study, nanosheet-structured nickel-cobalt (Ni-Co) oxide thin films were prepared via facile processes under simple solution conditions and were used as energy-saving electrochromic materials. As the growth time increased from 1.5 h to 8 h, the film thickness increased from ~ 0.7 μm to ~ 1.3 μm, and the porous nanosheet-like structures were more uniformly distributed throughout the thin film. At the 1000th cyclic voltammetry (CV) cycle (scan rate = 50 m/V), the in situ transmittance variation ( Δ T ) and optical density ( Δ OD ) of an Ni-Co oxide thin film grown for 8 h were ~ 49% and ~ 0.71 at a wavelength of 700 nm, respectively, which were better than those of samples grown for 1.5 h ( Δ T of ~ 26%, Δ OD of ~ 0.19) and 3 h ( Δ T of ~ 46%, Δ OD of ~ 0.61). However, the Ni-Co oxide thin-film samples grown for 1.5 h and 3 h had good electrochromic durability over 1000 cycles, with reversibility of 0.99. These Ni-Co oxide thin films exhibited tunable color modulation in the bleached and colored states, along with fast switching time (< 4 s) and excellent coloration memory effects. [ABSTRACT FROM AUTHOR]

Diarylethene (DAE) is one of the most widely used functional units for electrochromic or photochromic materials. To better understand the molecular modification effects on the electrochromic and photochromic properties of DAE, two modification strategies, substitution with functional groups or heteroatoms, were investigated theoretically by density functional theory calculations. It is found that red-shifted absorption spectra caused by a decreased highest occupied molecular orbital–lowest unoccupied molecular orbital energy gap and S0 → S1 transition energy during the ring-closing reaction become more significant by adding different functional substituents. In addition, for two isomers, the energy gap and S0 → S1 transition energy decreased by heteroatom substitution of S atoms with O or NH, while they increased by replacing two S atoms with CH2. For intramolecular isomerization, one-electron excitation is the most effective way to trigger the closed-ring (O → C) reaction, while the open-ring (C → O) reaction occurs most readily in the presence of one-electron reduction. Moreover, it is confirmed that substitution with strong electron donating groups (–OCH3/–NH2) or with one O/two CH2 heteroatoms leads to a more favorable closed-ring (O → C) reaction. Functionalized with strong electron-withdrawing groups (–NO2 and –COOH) or one/two NH heteroatom substitutions, the open-ring (C → O) reaction is easier. Our results confirmed that the photochromic and electrochromic properties of DAE can be tuned effectively by molecular modifications, which provides theoretical guidance for the design of new DAE-based photochromic/electrochromic materials. [ABSTRACT FROM AUTHOR]

Prussian blue (PB) is considered a potential electrochromic material owing to its open structure, simple synthesis and reversible conversion of multicolor, and studies are focused on its color change of transparent 2blue. However, the multicolor conversion of transparent 2blue2 green2yellow has rarely been reported because the alkali metal ion in the existing PB film is lower in concentration than its standard chemical formula, which makes the complete oxidation from PB to Prussian yellow (PY) unachievable. Herein, the Na-rich rhombic Prussian white (PW) is synthesized via the hydrothermal method, and its mechanism of multicolor conversion is studied. Benefitting from the adequate sodium, the PW film exhibits outstanding electrochromic performance with the reversible multicolor change of transparent 2 blue 2 green 2 yellow and excellent cycling stability (52.1% of capacity retention after 300 cycles). Simultaneously, the long cycling stability and high coloration efficiency of the PW film are also revealed in the process of PW 2 PB. In addition, the self-powered electrochromic device with the system of Zn||PW||Pt@CC is constructed, and it realizes fast coloring response time (26.3 s) and high reversibility. The reversible multicolor conversion and excellent cycling stability of the PW film make it a promising candidate for applications such as camouflage and high-performance smart windows. [ABSTRACT FROM AUTHOR]

Owing to the energy-efficient attributes of electrochromic technology, there has been a growing emphasis on the fabrication of electrochromic devices with high-contrast and stable performance. As an electron donor, the deliberate incorporation of oxygen vacancies into an electrochromic material is poised to significantly elevate the film's electrochromic characteristics. In this study, we successfully synthesized one-dimensional W 18 O 49 nanowires thin films with enhanced oxygen vacancies using a straightforward combination of solvothermal reactions and annealing in Ar. In comparison to films annealed in air, those treated in argon (Ar) exhibited a higher concentration of oxygen vacancies, resulting in improved light absorption characteristics. The optimal annealing conditions were determined to be 400 °C for 40 min. Under these conditions, the thin film demonstrates enhanced electrochromic performance, exhibiting a notable 71.6% modulation in transmittance, a 27.2% increase compared to the air condition. It displays a rapid response time (T b = 3.3 s, T c = 3 s), high coloration efficiency (CE = 55.9 cm2 C−1), and excellent cycling stability (with a ΔT retention rate of 93.9% after 750 cycles). [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]

Electrochromism has emerged as a pivotal technology in the pursuit of energy efficiency and environmental sustainability, spurring significant research efforts aimed at the creation of advanced electrochromic devices. Most electrochromic materials are used for smart window applications. However, current electrochromic materials have been applied to new energy vehicles, cell phone back covers, AR glasses, and so on. More application scenarios put forward more requirements for the color of the colored states. Choosing the right color change in the application will be the trend in the future. In this work, tungsten trioxide (WO3) thin films were prepared by adjusting the in situ heating temperature. WO3 with a crystalline structure showed excellent cyclic stability (5000 cycles), electrochromic performance (ΔT = 77.7% at 633 nm, CE = 37.1 cm2/C), relatively fast bleaching/coloring speed (20.0 s/19.4 s), and the darkest coloring effect (L* = 29.32, a* = 7.41, b* = −22.12 for the colored state). These findings offer valuable insights into the manipulation of smart materials and devices, contributing to the advancement of electrochromic technology. [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]

Covalent organic frameworks (COFs) with reversible redox units and a conjugated molecular skeleton possess novel photoelectrochemical properties. In this work, tris(4-aminophenyl)amine and 4,4-biphenyldiformaldehyde were chosen to synthesize TABP-COF electrochromic film with triphenylamine (TPA) active unit by a solvothermal method in a Teflon-lined reactor. The growth process and reaction time optimization of the TABP-COF were studied. TABP-COF shows a self-assembly growth process from an array of nanosheets to nanospheres. Owing to the redox characteristics of TPA, the TABP-COF film exhibits reversible electrochromic behavior. With a solvothermal reaction time of 72 h, the TABP-COF-3 film exhibits the best electrochromic properties, including contrast of 0.483 and response time of 7.3 s/13.6 s. Considering the abundance of redox-active units that can be chosen, COF materials with different redox units and color changes can be designed for a variety of applications in the field of electrochromic materials. [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 electrochromic (EC) mechanisms of inorganic materials are usually based on reversible cation insertion/extraction or metal deposition/dissolution, which are plagued by ion trapping and dendrite growth, respectively. In this paper, a novel conversion-type electrochromic mechanism is proposed, by making good use of the CuI/Cu redox couple. This CuI-based electrochromic system shows a neutral color switching from transparent and dim grey. By simply increasing the bleaching voltage, I 3 − / I − redox couple can be further activated. The generated I 3 − will readily react with Cu, effectively improving the conversion reversibility and thereby rejuvenating the degraded electrochromic performance. Thanks to the well-designed electrode and the self-healing ability, this conversion electrochromic system achieves rapid response times (tcoloring: 23 s, tbleaching: 6 s), decant optical modulation amplitude (26.4%), high coloration efficiency (86.15 cm2·C−1), admirable cyclic durability (without performance degradation after 480 cycles) and excellent optical memory ability (transmittance variation < 1% after 10 h open-circuit storage). The establishment of this conversion-type electrochromism may inspire the exploration of novel electrochromic materials and devices. [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]

Smart energy storage systems, such as electrochromic supercapacitor (ECSC) integrated technology, have drawn a lot of attention recently, and numerous developments have been made owing to their reliable performance. Developing novel electrode materials for ECSCs that embed two different technologies in a material is an exciting and emerging field of research. To date, the research into ECSC electrode materials has been ongoing with excellent efforts, which need to be systematically reviewed so that they can be used to develop more efficient ECSCs. This mini-review provides a general composition, main evaluation parameters and future perspectives for electrode materials of ECSCs as well as a brief overview of the published reports on ECSCs and performance statistics on the existing literature in this field. [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]

Phenazine-based redox-active centers are capable of averting chemical bond rearrangements by coupling during the reaction process, leading to enhanced stabilization of the material. When introduced into a high-performance polymer with excellent physicochemical properties, they can be endowed with electrochemical properties and related prospective applications while maintaining the capabilities of the materials. In this study, a facile C-N coupling method was chosen for the synthesis of serial poly(aryl ether sulfone) materials containing phenazine-based redox-active centers and to explore their electrochemical properties. As expected, the cyclic voltammetry curves of PAS-DPPZ-60, which basically overlap after thousands of cycles, indicate the stability of the electrochemical properties. As an electrochromic material, the transmittance change in PAS-DPPZ-60 exhibits only a slight attenuation after as long as 600 cycles. Meanwhile, as an organic battery cathode material, PAS-DPPZ has a theoretical specific capacity of 126 mAh g−1, and the capacity retention rate is 82.6% after 100 cycles at a 0.1 C current density. The perfect combination of advantageous features between phenazine and poly(aryl ether sulfone) is considered to be the reason for the favorable electrochemical performance of the material series. [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 been extensively investigated as promising candidates in broad cutting-edge applications, such as smart windows, electronic labels, adaptive camouflage, etc. However, they have suffered from either inadequate color variations or poor cycling stability for a long time. Herein, we developed a general strategy to boost the cyclic stability and enrich the color variations of ECDs by scrupulous design of the composition and nanostructure of electrodes, in which porous tin oxide (SnO2) nanosheets serve as the scaffold and typical metal oxides or conducting polymers as the active electrochromic materials. Various electrochromic composite materials, including polyaniline (PANI)@SnO2, V2O5@SnO2, and WO3@SnO2 heterostructured nanoarrays were prepared by the facile wet-chemical method. These composite electrodes exhibit remarkable electrochromic performances, e.g., superior cycling stability (more than 2000 cycles), rich color variations (more than 5 colors for PANI@SnO2), and enlarged optical modulation. These excellent performances account for the heterogenous porous nanoarrays, which not only facilitate the intercalation/extraction of ions but also relieve the stress generated during the electrochemical process. In addition, diverse prototypes of complementary multicolor ECD with excellent cycling stability (over thousands of cycles) and rich color variations (8 colors) were realized for the first time. We believe that our work put forward a general strategy for developing high-quality multicolor complementary electrochromic devices. [ABSTRACT FROM AUTHOR]