Showing papers on "Electrochromism published in 2020"

Fusing electrochromic technology with other advanced technologies: A new roadmap for future development

Abstract: Electrochromism is the phenomenon of certain materials reversibly changing their colours or optical properties through redox reactions under an applied electric field, which has found applications in smart windows, displays and so on. The past four decades have witnessed the rapid development of electrochromic technology; however, it remains severely developmentally challenged due to its limited practical applications. Predictably, as a colour control technology that gives visual information readable by the naked eye, electrochromism should have much wider applications by applying the visualization technique to various functional devices. Indeed, some recent research findings show that integrating electrochromic technology with other advanced technologies has imparted a new strong impetus for the further development of electrochromic technology. However, a systematic review of the literature on the fusing of electrochromic technology with other advanced technologies is still lacking, demonstrating the urgent need for further studies, although there are some review papers on electrochromic energy storage devices. In this review, we systematically discuss the recent advances in the fusing of electrochromic technology with other advanced technologies, including wearable technology, thermal control technology, energy storage technology, energy harvesting technology and sensing technology. The integration modes, design principles and performance optimization for different types of interdisciplinary electrochromic devices are highlighted. Finally, an outlook concerning future trends and issues in the research field is also provided.

Towards full-colour tunability of inorganic electrochromic devices using ultracompact fabry-perot nanocavities.

Abstract: Intercalation-based inorganic materials that change their colours upon ion insertion/extraction lay an important foundation for existing electrochromic technology. However, using only such inorganic electrochromic materials, it is very difficult to achieve the utmost goal of full-colour tunability for future electrochromic technology mainly due to the absence of structural flexibility. Herein, we demonstrate an ultracompact asymmetric Fabry-Perot (F-P) nanocavity-type electrochromic device formed by using partially reflective metal tungsten as the current collector and reflector layer simultaneously; this approach enables fairly close matching of the reflections at both interfaces of the WO3 thin layer in device form, inducing a strong interference. Such an interference-enhanced device that is optically manipulated at the nanoscale displays various structural colours before coloration and, further, can change to other colours including blue, red, and yellow by changing the optical indexes (n, k) of the tungsten oxide layer through ion insertion.

Plasmonic Oxygen-Deficient TiO2-x Nanocrystals for Dual-Band Electrochromic Smart Windows with Efficient Energy Recycling.

Abstract: Dual-band electrochromic smart windows capable of the spectrally selective modulation of visible (VIS) light and near-infrared (NIR) can regulate solar light and solar heat transmittance to reduce the building energy consumption. The development of these windows is however limited by the number of available dual-band electrochromic materials. Here, plasmonic oxygen-deficient TiO2-x nanocrystals (NCs) are discovered to be an effective single-component dual-band electrochromic material, and that oxygen-vacancy creation is more effective than aliovalent substitutional doping to introduce dual-band properties to TiO2 NCs. Oxygen vacancies not only confer good near-infrared (NIR)-selective modulation, but also improve the Li+ diffusion in the TiO2-x host, circumventing the disadvantage of aliovalent substitutional doping with ion diffusion. Consequently optimized TiO2-x NC films are able to modulate the NIR and visible light transmittance independently and effectively in three distinct modes with high optical modulation (95.5% at 633 nm and 90.5% at 1200 nm), fast switching speed, high bistability, and long cycle life. An impressive dual-band electrochromic performance is also demonstrated in prototype devices. The use of TiO2-x NCs enables the assembled windows to recycle a large fraction of energy consumed in the coloration process ("energy recycling") to reduce the energy consumption in a round-trip electrochromic operation.

Electrochromic two-dimensional covalent organic framework with a reversible dark-to-transparent switch.

Abstract: Electrochromic (EC) materials with a dark-to-transmissive switch have great applications in optical communications, infrared wavelength detectors for spacecraft, and infrared camouflage coatings. However, such electroactive materials with high stability and cyclability are rare. Considering the advantages of the donor-acceptor approach (wide-range tuneable band position) and porous two-dimensional (2D) covalent organic framework (COF, well-ordered crystalline framework with stable structure and high surface area), in this work we constructed an extended delocalised π-electron layered dark purple EC-COF-1 by reacting the donor N,N,N′,N′-tetrakis(p-aminophenyl)-p-benzenediamine (TPBD) with the acceptor 2,1,3-benzothiadiazole-4,7-dicarboxaldehyde (BTDD). A sandwiched device made of EC-COF-1 exhibits the two-band bleaching (370 nm and 574 nm) in the visible region and becomes transparent under the applied potential with an induced absorption centring at 1400 nm. This discovery of a stable dark-to-transmissive switch in COF might open another door for their application in many EC devices for various purposes. Electrochromic materials are important for different optical applications but often these materials show low stability. Here, the authors demonstrate a stable donor-acceptor covalent organic framework which shows a stable dark-to-transmissive switching behaviour.

Transparent Zinc-Mesh Electrodes for Solar-Charging Electrochromic Windows

Abstract: Newly born zinc-anode-based electrochromic devices (ZECDs), incorporating electrochromic and energy storage functions in a single transparent platform, represent the most promising technology for next-generation transparent electronics. As the existing ZECDs are limited by opaque zinc anodes, the key focus should be on the development of transparent zinc anodes. Here, the first demonstration of a flexible transparent zinc-mesh electrode is reported for a ZECD window that yields a remarkable electrochromic performance in an 80 cm2 device, including rapid switching times (3.6 and 2.5 s for the coloration and bleaching processes, respectively), a high optical contrast (67.2%), and an excellent coloration efficiency (131.5 cm2 C-1 ). It is also demonstrated that such ZECDs are perfectly suited for solar-charging smart windows as they inherently address the solar intermittency issue. These windows can be colored via solar charging during the day, and they can be bleached during the night by supplying electrical energy to electronic devices. The ZECD smart window platform can be scaled to a large area while retaining its excellent electrochromic characteristics. These findings represent a new technology for solar-charging windows and open new opportunities for the development of next-generation transparent batteries.

An electrochromic supercapacitor based on an MOF derived hierarchical-porous NiO film

Abstract: Nickel oxide (NiO) is a promising candidate for future electrochromic supercapacitors due to its pronounced electrical properties and low cost. Unfortunately, the weak interaction between NiO films and conductive substrates results in poor cycling stability. In addition, the long color-switching time and low capacitance by the small lattice spacing in dense NiO impede its practical applications seriously. Herein, a hierarchical porous NiO film/ITO glass bifunctional electrode has been prepared via the solvothermal and subsequent calcination process of growing MOF-74 in situ on ITO, which shows outstanding cycle reversibility, excellent capacitance, high coloration efficiency and short color-switching time. Because of the strong binding force between the NiO film and substrate, and large surface areas with a hierarchical porous structure which are beneficial to the ion transport, the NiO film demonstrates perfect capacitive and electrochromic properties. As a bifunctional electrode, the NiO film shows a specific capacitance of 2.08 F cm−2 at 1 mA cm−2, large optical modulation of 41.08% and about 86% of optical modulation retention after 10 000 cycles. Furthermore, we assembled a bifunctional device whose energy condition can be roughly estimated according to the color state of the device. This finding can provide us with a new application of MOFs in the dual device of electrochromic supercapacitors.

Molecular Level Assembly for High-Performance Flexible Electrochromic Energy-Storage Devices

Abstract: The rational design and scalable assembly of nanoarchitectures are important to deliver highly uniform, functional films with high performance. However, fabrication of large-area and high-performan...

Transparent inorganic multicolour displays enabled by zinc-based electrochromic devices

Abstract: Electrochromic displays have been the subject of extensive research as a promising colour display technology. The current state-of-the-art inorganic multicolour electrochromic displays utilize nanocavity structures that sacrifice transparency and thus limit their diverse applications. Herein, we demonstrate a transparent inorganic multicolour display platform based on Zn-based electrochromic devices. These devices enable independent operation of top and bottom electrochromic electrodes, thus providing additional configuration flexibility of the devices through the utilization of dual electrochromic layers under the same or different colour states. Zn–sodium vanadium oxide (Zn–SVO) electrochromic displays were assembled by sandwiching Zn between two SVO electrodes, and they could be reversibly switched between multiple colours (orange, amber, yellow, brown, chartreuse and green) while preserving a high optical transparency. These Zn–SVO electrochromic displays represent the most colourful transparent inorganic-based electrochromic displays to date. In addition, the Zn–SVO electrochromic displays possess an open-circuit potential (OCP) of 1.56 V, which enables a self-colouration behaviour and compelling energy retrieval functionality. This study presents a new concept integrating high transparency and high energy efficiency for inorganic multicolour displays. Transparent electrochromic displays with a richer colour palette are now possible. Electrochromic displays, which change their colour due to electrochemistry, are receiving interest due to their low power consumption but a lack of colours is problematic. Wu Zhang and coworkers from the University of Alberta in Canada and Louisiana State University in the USA fabricated multicolour displays using sodium ion stabilized vanadium oxide nanorods (Zn-SVO) as the electrochromic material. Two layers of this material, separated by a layer of zinc and a gel electrolyte were sandwiched between glass coated with indium tin oxide. Application of a small voltage causes the SVO film to exhibit a reversible switch between orange, yellow and green. The use of two independently-controlled films in the display provides a broader range of colours (orange, amber, yellow, brown, chartreuse and green).

Fabry-Perot Cavity-Type Electrochromic Supercapacitors with Exceptionally Versatile Color Tunability

Abstract: Electrochromic supercapacitors that can change their appearances according to their charged states are presently attracting significant interest from both academia and industry. Tungsten oxide is often used in electrochromic supercapacitors because it can serve as an active material for both benchmarking electrochromic devices and high-performance supercapacitor electrodes. Despite this, acceptable visual aesthetics in electrochromic supercapacitors have almost never been achieved using tungsten oxide, because, in its pure form, this compound only displays a 1-fold color modulation from transparent to blue. Herein, we defy this trend by reporting the first ever Fabry-Perot (F-P) cavity-type electrochromic supercapacitors based only on a tungsten oxide material. The devices were sensitively changeable according to their charge/discharge states and displayed a wide variety of fantastic patterns consisting of different, vivid colors, with both simple and complex designs being achieved. Our findings suggested a novel direction for the aesthetic design of intelligent, multifunctional electrochemical energy storage devices.

Nanostructured inorganic electrochromic materials for light applications

Abstract: Abstract Electrochromism, an emerging energy conversion technology, has attracted immense interest due to its various applications including bistable displays, optical filters, variable optical attenuators, optical switches, and energy-efficient smart windows. Currently, the major drawback for the development of electrochromism is the slow switching speed, especially in inorganic electrochromic materials. The slow switching speed is mainly attributed to slow reaction kinetics of the dense inorganic electrochromic films. As such, an efficient design of nanostructured electrochromic materials is a key strategy to attain a rapid switching speed for their real-world applications. In this review article, we summarize the classifications of electrochromic materials, including inorganic materials (e.g., transition metal oxides, Prussian blue, and polyoxometalates), organic materials (e.g., polymers, covalent organic frameworks, and viologens), inorganic-organic hybrids, and plasmonic materials. We also discuss the electrochromic properties and synthesis methods for various nanostructured inorganic electrochromic materials depending on structure/morphology engineering, doping techniques, and crystal phase design. Finally, we outline the major challenges to be solved and discuss the outlooks and our perspectives for the development of high-performance nanostructured electrochromic materials.

Reliable, High-Performance Electrochromic Supercapacitors Based on Metal-Doped Nickel Oxide.

Abstract: Herein, high-performance, reliable electrochromic supercapacitors (ECSs) are proposed based on tungsten trioxide (WO3) and nickel oxide (NiO) films. To maximize device performance and stability, the stoichiometric balance between anode and cathode materials is controlled by carefully adjusting the thickness of the anodic NiO film while fixing the thickness of WO3 to ∼660 nm. Then, a small amount (≤10 mol %) of metal (e.g., copper) is doped into the NiO film, improving the electrical conductivity and electrochemical activity. At a Cu doping level of 7 mol %, the resulting ECS exhibited the highest performance, including a high areal capacitance (∼14.9 mF/cm2), excellent coulombic efficiency (∼99%), wide operating temperature range (0-80 °C), reliable operation with high charging/discharging cyclic stability (>10,000 cycles), and good self-discharging durability. Simultaneously, the change in transmittance of the device is well synchronized with the galvanostatic charging/discharging curve by which the real-time energy storage status is visually indicated. Furthermore, the practical feasibility of the device is successfully demonstrated. These results imply that the ECS fabricated in this work is a promising potential energy storage platform and an attractive component for future electronics.

A flexible, electrochromic, rechargeable Zn-ion battery based on actiniae-like self-doped polyaniline cathode

Abstract: Flexible/wearable electrochromic zinc-ion battery (EC-ZIB) is considered to be promising smart multifunctional energy storage devices that monitor energy storage on the basis of their color variation. Herein, a self-doped PANI (SPANI) electrode has been prepared by a facile electrochemical copolymerization process. The prepared SPANI film exhibits a novel actiniae-like morphology, which is beneficial for electrolyte infiltration due to short ion diffusion pathways and fast electrochemical kinetics that ensure enhanced specific capacity. In a full all-in-one EC-ZIB device, the SPANI cathode provides a high specific capacitance of 180.5 mA h g−1 at 0.5 A g−1, excellent rate capability of 75.3% capacity retention even at a 20-fold current-density increase. The EC-ZIB possesses high energy and power densities (181.1 W h kg−1 @ 501.8 W kg−1 and 124.7 W h kg−1 @ 9148.6 W kg−1). At the same time, another positive is that the EC-ZIB has excellent electrochromic properties (light yellow, green and dark green) from 0.5 to 1.6 V. Therefore, its energy storage can be conveniently monitored according to color variation. The EC-ZIB efficiently combines multiple smart features, promoting the development of flexible intelligent energy storage devices.

Preparation of WO 3 Films with ControllableCrystallinity for ImprovedNear-Infrared Electrochromic Performances

Abstract: In this study, a WO3 film with controllable crystallinity has been prepared by radio frequency magnetron sputtering. The WO3 film with about 400 nm thickness and controllable crystallinity not only...

An Electrochromic Hydrogen‐Bonded Organic Framework Film

Abstract: Hydrogen-bonded organic frameworks (HOFs) possess various merits, such as high porosity, tunable structure, facile modification, and ready regeneration. These properties have yet to be explored in the context of new functional HOF materials. The facile and inexpensive electrophoretic deposition (EPD) method applied in this study generated a transparent HOF film at room temperature in just 2 min and is applicable to other HOFs. The resulting film exhibited reversible electrochromism with the advantage of long cycle life (>500 cycles). More strikingly, this all-organic film could be readily regenerated (through rinsing with DMF and redeposition) and showed tunable electrochromic behavior (through low-cost postsynthetic modification) with the ability to undergo successive color changes, which is difficult to achieve with conventional electrochromic materials. An electrochromic device was manufactured to further demonstrate the application potential of the film.

High Performance Multicolor Intelligent Supercapacitor and Its Quantitative Monitoring of Energy Storage Level by Electrochromic Parameters

Abstract: The construction of an electrochromic supercapacitor device (ESD) with multicolor change, good energy storage capacity, cyclic stability, and the realization of the quantitative monitoring of energ...

Revealing the Charge Storage Mechanism of Nickel Oxide Electrochromic Supercapacitors.

Abstract: Nickel oxide (NiO) is considered one of the most promising positive anode materials for electrochromic supercapacitors. Nevertheless, a detailed mechanism of the electrochromic and energy storage process has yet to be unraveled. In this research, the charge storage mechanism of a NiO electrochromic electrode was investigated by combining the in-depth experimental and theoretical analyses. Experimentally, a kinetic analysis of the Li-ion behavior based on the cyclic voltammetry curves reveals the major contribution of surface capacitance versus total capacity, providing fast reaction kinetics and a highly reversible electrochromic performance. Theoretically, our model uncovers that Li ions prefer to adsorb at fcc sites on the NiO(1 1 1) surface, then diffuse horizontally over the plane, and finally migrate in the bulk. More significantly, the calculated theoretical surface capacity (106 mA h g-1) accounts for about 77.4% of the total experimental capacity (137 mA h g-1), indicating that the surface storage process dominates the whole charge storage, which is in accordance with the experimental results. This work provides a fundamental understanding of transition-metal oxides for application in electrochromic supercapacitors and can also promote the exploration of novel electrode materials for high-performance electrochromic supercapacitors.

A new design of an electrochromic energy storage device with high capacity, long cycle lifetime and multicolor display

Abstract: Electrochromic energy storage (EES) devices with high capacity, long-term stability and multicolor display are highly desired for practical applications. Here, we propose a new three-electrode design of an EES device. Two kinds of electrochromic materials (WO3 and Ti-V2O5 respectively) deposited on ITO glass work as electrochromic active layers. Al metal is used as the anodic frame of the device and helps to seal the mixed Li/Al-ion electrolyte. For electrochromic applications, the device shows rapid, self-powered color switching with multicolor display (light yellow, transparent, light red, dark green, dark blue and black). As an energy storage device, the as-assembled device provides open-circuit voltages up to 3.5 V (Al anode/Ti-V2O5 cathode) with an areal capacity of up to 933 mA h m−2 (Al/Ti-V2O5 and Al/WO3), which are the best among those of all reported EES devices. Meanwhile, the utilization of the mixed Li/Al-ion electrolyte and the addition of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) into the films greatly promote the robustness and the cycle stability of the electrochromic layers. Such a new design of the EES device with multicolor display, large charge capacity and high cycle stability can be promising for future color switching/energy storage applications, which may also provide new insights into the design of multifunctional devices.

One-Dimensional π-d Conjugated Coordination Polymer for Electrochromic Energy Storage Device with Exceptionally High Performance.

Abstract: The rational design of previously unidentified materials that could realize excellent electrochemical-controlled optical and charge storage properties simultaneously, are especially desirable and useful for fabricating smart multifunctional devices. Here, a facile synthesis of a 1D π-d conjugated coordination polymer (Ni-BTA) is reported, consisting of metal (Ni)-containing nodes and organic linkers (1,2,4,5-benzenetetramine), which could be easily grown on various substrates via a scalable chemical bath deposition method. The resulting Ni-BTA film exhibits superior performances for both electrochromic and energy storage functions, such as large optical modulation (61.3%), high coloration efficiency (223.6 cm2 C-1), and high gravimetric capacity (168.1 mAh g-1). In particular, the Ni-BTA film can maintain its electrochemical recharge-ability and electrochromic properties even after 10 000 electrochemical cycles demonstrating excellent durability. Moreover, a smart energy storage indicator is demonstrated in which the energy storage states can be visually recognized in real time. The excellent electrochromic and charge storage performances of Ni-BTA films present a great promise for Ni-BTA nanowires to be used as practical electrode materials in various applications such as electrochromic devices, energy storage cells, and multifunctional smart windows.

Polythiophene-nanoWO3 bilayer as an electrochromic infrared filter: a transparent heat shield

Abstract: A power-efficient, ultrafast and stable organic–inorganic hybrid electrochromic device fabricated using WO3 and P3HT as active materials has been demonstrated herein for dual application in an electrochromic window as well as an IR filter. The device when turned ON using a bias as low as 1 V shows heat shielding effect as well as increased optical transparency to keep the area cooler by ∼8 °C (22%) to maintain the room temperature at 302 K, as imaged using an IR camera. The solid state electrochromic IR filter device was fabricated in simple cross bar geometry with the WO3/P3HT bilayer sandwiched between two electrodes. The device works on the principle of a bias-induced redox change process, as established using electrochemical and spectroscopic investigations. The device exhibits superior electrochromic behavior with dual function, with a maximum color contrast of ∼60% in the IR region with excellent coloration efficiency of ∼380 cm2 C−1 at 520 nm and stability of more than 1600 ON/OFF cycles without compromising its performance. Possibility of the device to be used as an electrochromic window and heat shield has been demonstrated using real life experiments.

Supramolecular G4 Eutectogels of Guanosine with Solvent‐Induced Chiral Inversion and Excellent Electrochromic Activity

Abstract: Supramolecular eutectogels, an emerging class of materials that have just developed very recently, offer a new opportunity for generating functional supramolecular gel materials in biocompatible anhydrous or low-water media. As the first example of supramolecular G4 eutectogels, complexes of natural guanosine and H3 BO3 exhibited excellent gelation capacity in choline chloride/alcohol deep eutectic solvents. The as-prepared supramolecular eutectogels displayed unexpected solvent-induced chiral inversion and significantly high ionic conductivity (up to 7.78 mS cm-1 ), as well as outstanding thixotropic/injectable properties, high thermal stability and excellent electrochromic activity. These features make these versatile supramolecular G4 eutectogels promising candidates for developing next-generation flexible electronics with low environmental impact.

Fast response of complementary electrochromic device based on WO 3 /NiO electrodes

Abstract: Nanoporous structures have proven as an effective way for enhanced electrochromic performance by providing a large surface area can get fast ion/electron transfer path, leading to larger optical modulation and fast response time. Herein, for the first time, application of vacuum cathodic arc plasma (CAP) deposition technology to the synthesis of WO3/NiO electrode films on ITO glass for use in fabricating complementary electrochromic devices (ECDs) with a ITO/WO3/LiClO4-Perchlorate solution/NiO/ITO structure. Our objective was to optimize electrochromic performance through the creation of electrodes with a nanoporous structure. We also examined the influence of WO3 film thickness on the electrochemical and optical characteristics in terms of surface charge capacity and diffusion coefficients. The resulting 200-nm-thick WO3 films achieved ion diffusion coefficients of (7.35 × 10−10 (oxidation) and 4.92 × 10−10 cm2/s (reduction)). The complementary charge capacity ratio of WO3 (200 nm thickness)/NiO (60 nm thickness) has impressive reversibility of 98%. A demonstration ECD device (3 × 4 cm2) achieved optical modulation (ΔT) of 46% and switching times of 3.1 sec (coloration) and 4.6 sec (bleaching) at a wavelength of 633 nm. In terms of durability, the proposed ECD achieved ΔT of 43% after 2500 cycles; i.e., 93% of the initial device.