Search Results (219)

Tungsten trioxide (WO₃) is the most widely studied cathodic electrochromic (EC) material, serving as the core component of energy-efficient smart windows, displays, and optical modulation devices. Post-deposition annealing, as a critical post-processing technique, precisely regulates the microstructure, crystallinity, oxygen vacancy concentration, and electronic structure of WO₃ thin films, thereby directly determining their EC performance. This review summarizes the research progress of annealing effects on WO₃ films, focusing on the synergistic regulation of annealing temperature, atmosphere, and dwell time. It elaborates on the fundamental EC mechanisms of amorphous and crystalline WO₃, including polaron hopping and free-electron Drude behavior, and analyzes the influence of different deposition methods (magnetron sputtering, sol–gel, electrodeposition, etc.) on the annealing response of films. The optimal annealing windows for balancing optical modulation, coloration efficiency, switching speed, and cycling stability are clarified: moderate temperatures (200–350 °C) and inert/air atmospheres yield mixed amorphous–nanocrystalline structures with optimal oxygen vacancy content. Current challenges such as the inherent contrast–stability trade-off and thermal budget limitations of flexible substrates are discussed, and future directions including spatially resolved annealing, interface co-design, and machine learning-assisted optimization are prospected. This work provides a theoretical reference and process guidance for the development of high-performance WO₃-based EC devices. Full article

Chromic materials exhibiting reversible changes in optical properties under external stimuli represent an important class of smart materials with applications in smart windows, sensors, and optoelectronic devices. Transition-metal oxides (TMOs) provide a versatile platform for chromic functionality due to their coupled structural, electronic, and optical properties. In this review, the chromic response of selected TMO thin films is analyzed using both microscopic and phenomenological approaches. The microscopic description is based on many-body theory, including Green’s function methods and correlation effects, while the macroscopic optical response is described using Drude–Lorentz and Tauc–Lorentz models within the effective medium approximation. Chromic behavior in TMOs is shown to originate from two principal mechanisms: (i) electronic and structural reconstruction driven by Peierls–Mott metal–insulator phase transitions, leading to thermochromism (notably in VO₂ and V₂O₃), and (ii) formation of localized states driven by small-polaron injection, giving rise to electrochromism, gasochromism, and photochromism. The models are applied to representative systems, including VO₂, WO₃, NiO, and TiO₂, demonstrating the chromic changes in the dielectric function spectra. These results highlight chromism in TMOs as a multiscale phenomenon linking microscopic interactions with macroscopic optical response. Full article

Silver nanowire (AgNW) networks have attracted significant attention as leading candidates for flexible transparent electrodes owing to their unique combination of high electrical conductivity, optical transparency, and mechanical compliance. This review presents an overview of recent developments in AgNW-based transparent electrode technologies, with particular emphasis on strategies to improve network conductivity and long-term reliability, including junction engineering, surface modification, encapsulation approaches, and composite structure design. Representative applications in flexible optoelectronic systems, such as organic light-emitting devices, transparent heating elements, and electrochromic platforms, are also discussed. Finally, current challenges and future research directions toward scalable manufacturing and practical implementation of high-performance AgNW electrodes are outlined. Full article

The advancement of electrochromic devices, including smart windows, is important for improving energy efficiency in modern society. Nickel oxide thin films are key functional materials in this technology and have attracted significant attention due to their electrochemical activity and optical properties. However, existing theoretical studies have primarily focused on crystalline NiO, while systematic understanding of Li⁺ diffusion mechanisms in amorphous NiO remains limited. In this work, first-principles calculations combined with second-generation Car–Parrinello molecular dynamics simulations and the melt-quenching method are employed to construct amorphous NiO models with varying oxygen content, enabling investigation of oxygen-dependent Li⁺ diffusion behavior. The results show that the Li⁺ diffusion coefficient increases with increasing oxygen content, accompanied by a reduction in diffusion barriers. Analysis of local structural environments further reveals that Li coordination with under-coordinated Ni–O polyhedra plays a key role in facilitating ion migration, providing atomistic insight into the observed diffusion trends. This study establishes a structure–diffusion relationship in amorphous NiO and provides atomistic understanding of how oxygen stoichiometry modulates Li⁺ transport behavior in electrochromic materials. Full article

In this work, we elaborately designed two nickel(II) Schiff base complexes (NiL and NiL’) with different π-conjugated systems (benzene vs. naphthalene) to prepare uniform metallopolymer films with nickel(II) chelates as repeating units on ITO substrates through oxidative electropolymerization. The π-conjugation extending from the benzene moiety to the naphthalene moiety greatly enhances the electron delocalization of the metallopolymer film, resulting in a significant increase in optical contrast from 25% ([NiL]_n) to 80% ([NiL’]_n). The solid-state electrochromic devices based on metallopolymer film [NiL’]_n achieved a transmittance modulation of 71% and an electrochromic efficiency of 268.58 cm² C⁻¹. This work provides an effective strategy for developing low-cost and high-performance non-precious metal electrochromic materials through ligand conjugation engineering. Full article

As one of the core technologies in modern national defense and security fields, infrared stealth technology aims to realize the controllable regulation of the radiation characteristics of targets in the infrared band. This paper focuses on a novel electrochromic device with a structure of WO₃/nickel mesh/Al³⁺-Zn²⁺gel electrolyte/zinc foil. The structural composition and working mechanism are systematically analyzed, and the infrared stealth regulation performance is emphatically studied. The WO₃ thin film and device structure were characterized by scanning electron microscopy (SEM). The infrared emissivity modulation and optical response properties of the device were measured using an infrared thermal imager and a UV-Vis-NIR spectrophotometer. The prepared WO₃ film exhibits a dense spherical morphology, indicating excellent uniformity and compactness. After 1000 cycles, the areal capacitance of the device remains 83.7% of its initial value, demonstrating good cycling stability. Under the voltage regulation of −0.1 V to 1.1 V, the emissivity ε of the device at the typical mid-wave infrared wavelength of 4.0 μm decreases from 0.89 (−0.1 V) to 0.67 (1.1 V), with an absolute modulation amplitude Δε of 0.22. At the typical long-wave infrared wavelength of 8.7 μm, ε decreases from 0.96 (−0.1 V) to 0.69 (1.1 V), with an absolute modulation amplitude Δε of 0.29. The electrochromic switching times for coloring and bleaching are 10.1 s and 2.44 s, respectively. According to infrared thermal imaging tests, in the temperature range of 30–40 °C, the surface temperature difference ΔT between the colored state and bleached state increases from 4.3 °C to 4.6 °C. The maximum regulation amplitude reaches 4.6 °C at 40 °C. The device achieves efficient regulation of infrared emissivity through the electrochromic effect, providing a new device design strategy for infrared stealth technology. Full article

Electrochromic devices have emerged as promising candidates for non-emissive displays due to their particular photoelectric performance in complex lighting environments. They exhibit considerable potential in emerging fields such as Internet of Things terminals, flexible wearables and human–computer interaction interfaces. In this study, we developed a low-power electrochromic display based on a Pt/FTO (Fluorine doped tin oxide) electrocatalytic counter electrode and a Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) porous gel electrolyte. The Pt catalyst enhances Br⁻/Br³⁻ redox reactivity, which reduces the driving voltage from 2 V to 1 V, and accelerates the electrode reaction kinetics. It is systematically explained by the Density Functional Theory (DFT) calculations and electrochemical characterization. Furthermore, we demonstrate a proof-of-concept multicolor display incorporating the electrocatalytic counter electrode with various viologen derivatives. This approach provides a significant advancement toward next-generation high-performance displays and is supportive of the development of energy-efficient optoelectronic devices. Full article

Nickel-oxide-based anodic electrochromic materials are extensively utilized as counter electrodes in smart window systems due to their reversible optical response during ion insertion and extraction. This study systematically investigates the influence of substrate temperature on the electrochromic properties of sputtered nickel-tungsten oxide thin films. The deposited thin films exhibit an amorphous structure. An increase in substrate temperature results in a decrease in nickel-vacancy concentration. Raman spectroscopy verifies the amorphous nature. Films deposited at lower substrate temperatures exhibit superior electrochromic performance, characterized by improved optical contrast of 64% and rapid coloration (2.21 s) and bleaching (0.93 s) dynamics. The enhanced performance is ascribed to the disordered amorphous structure and the existence of enough nickel vacancies, which collectively facilitate efficient and reversible lithium-ion transfer. This study illustrates that meticulous regulation of substrate temperature is an effective method for adjusting the microstructure and defect chemistry of nickel–tungsten oxide thin films, rendering them appropriate as effective counter electrodes for energy-efficient smart window applications. Full article

Escalating requirements for smart energy management are driving advances in functional electrochromic devices (ECDs), which are pivotal for the regulation of light, heat, and reduction in energy consumption in buildings, transportation, and smart devices. However, the commercialization of ECDs is hindered by com plex designs, high fabrication costs, and slow switching speeds. Additive manufacturing (AM, 3D-printing) emerges as a promising approach to overcome these limitations, as it enables the creation of complex structures, enhances design flexibility, and can reduce production costs. For such printed devices, materials combining poly(ionic liquids) (PILs) with ionogels—an emerging and promising class of materials known for their high ionic conductivity, stability, and tunable properties—are particularly suitable for integration with 3D printing. Comparing previous reviews that address PILs, ionogels, or AM modalities in isolation, this work uniquely combines the structure–property–processing relationships specific to the synergistic integration of these fields. Current work highlights recent progress in PIL/ionogel-based ECDs and distills specific design guidelines for optimizing ink rheology, balancing ionic conductivity with mechanical integrity, and selecting appropriate printing modalities. These insights provide a roadmap for overcoming current fabrication challenges and scaling up next-generation smart devices. Full article

NiO electrochromic films have significant potential for applications in smart windows, displays, energy-efficient buildings, and portable electronics, owing to their excellent electrochemical stability, favorable optical modulation performance, and environmental friendliness. However, several challenges remain, such as limited long-term durability, stability under extreme environmental conditions, and the cost-effectiveness of large-scale production. Future research efforts should focus on enhancing the cyclic stability and environmental adaptability of NiO films, developing low-cost fabrication techniques, and advancing multifunctional composite materials for smart devices. This review summarizes recent advances in the preparation and performance optimization of NiO electrochromic films. Several key fabrication methods—including magnetron sputtering, hydrothermal synthesis, electrodeposition, chemical bath deposition, sol–gel processing, and spray pyrolysis—are highlighted, and their effects on film structure, thickness uniformity, and optical properties are analyzed. Furthermore, the critical role of different electrolytes (inorganic, organic, and gel-based) in the electrochromic process is discussed, with a comparative evaluation of their influence on the electrochromic performance of NiO films. This article offers a comprehensive overview of the progress in high-performance NiO electrochromic films and provides theoretical insights and technical support for their broader application in renewable energy and smart home technologies. Full article

Structural coloration has attracted significant attention as a concept for next-generation reflective displays and optical devices. It enables high optical stability and durability, appearing vivid and highly visible compared to conventional light-absorption systems. We present a novel hybrid light-reflecting device that integrates electrochromic materials with structural coloration to dynamically and reversibly modulate the reflected light. Experiments confirm that the electrochromic materials enable color modulation through redox reactions under an applied voltage, whereas photonic structures provide vivid, angle-dependent structural coloration based on interference or diffraction effects. The developed device can achieve multistage visual modulation by integrating structural coloration with electrochromic functionality. Further, by combining these two light-modulating mechanisms, our device offers enhanced functionality compared with conventional reflective systems. Full article

Escalating climate change and the increasing frequency of weather extremes pose a threat to the resilience of urban environments and human health, highlighting the urgent need for implementing energy-efficient interventions and reducing building cooling loads. This study investigates the passive building envelope retrofit technologies of external shading, electrochromic windows, and thermochromic windows through a multi-criteria evaluation analysis based on energy savings, economic performance, and indoor thermal comfort improvement. Thermochromic windows are discerned by a mean colour transition temperature of 34 °C and operate throughout the entire year, while electrochromic windows are activated only during cooling periods. Both technologies present total solar transmittance indices of 72.6% and 8.4% in the bleached and tinted state, respectively. External shading devices are either static or movable, applied with an inclination angle, and are either standalone interventions or combined with chromogenic glazing. Eight retrofit scenarios are investigated for a single-story, fully electrified residential building in Athens, Greece. The building features south- and east-oriented windows, which is an appropriate case to assess the effectiveness of these passive envelope cooling technologies in regulating solar heat gains. Thermal comfort is assessed using Fanger’s PMV (predicted mean vote) and PPD (Predicted Percentage of Dissatisfied) indices. The combination of electrochromic windows and movable external shading yields the highest annual electricity savings at 22.2% and reduces the PPD by 15.8%. Local static shading, on the other hand, ranks as the optimal retrofit solution in terms of economic performance, with a life-cycle cost of €6378, a 9.3% improvement in thermal comfort, and a corresponding reduction of 626 thermal discomfort hours. While the proposed multi-criteria framework can be applied to other buildings and climates, the quantitative results reported here are linked to the specific case examined: a residential building with south- and east-facing glazing in Athens, Greece, representing Mediterranean climatic conditions. Full article

There is an increasing demand for multifunctional devices, that can operate simultaneously as energy storage and electrochromic display devices, widely known as electrochromic supercapacitors. For instance, Prussian blue (PB) exhibits outstanding electrochromic properties; however, it has not been well explored for energy storage applications. Moreover, the electrochemical properties can be enhanced by surface engineering the host material via compositing with conducting polymers. In this work, we studied the electrochromic supercapacitor properties of composites such as Prussian blue-polyaniline (PB-PANI). The PB-PANI 90 composite thin-film electrode exhibited the highest coloration efficiency of 461.39 cm²/C and demonstrated superior electrochemical performance, with an aerial capacitance of 50.80 mF/cm² and an optical modulation of 19.4%. All samples achieved rapid switching times of less than 3 s. These findings highlight the potential of optimizing conducting polymer coatings on Prussian blue to achieve a well-balanced composite structure with enhanced morphological properties, paving the way for advanced multifunctional electrochromic supercapacitor devices in next-generation smart systems. Full article

In the present study, highly transparent evaporated tungsten oxide films with improved charge storage properties were used in battery-like (b-ECDs) and hybrid electrochromic devices (h-ECDs). A Co^2+/3+ redox couple was added to the electrolyte as an alternative to other redox couples that have been already used in h-ECDs. The as-prepared h-ECDs, colored homogeneously, exhibited a contrast ratio of up to 7:1 in the visible spectrum, at a cathodic voltage of −2.5 V for only 10 s, compared to 3.5:1 at a cathodic voltage of −3 V for 180 s for a b-ECD. Moreover, when the redox couple was present in the electrolyte, almost a 50% higher areal capacitance and a 55% lower charge transfer resistance at the electrochromic layer/electrolyte interface were achieved. Also, the results show that the optical performance depends strongly on the coloration procedure (potentiostatic or galvanostatic), that self-bleaching is not so intense, and especially that the energy density consumed during bleaching is reduced in the presence of the redox couple. Overall, the findings of this study highlight the benefits of using a cobalt redox electrolyte in h-ECDs, allowing a direct comparison with b-ECDs, to dynamically control incoming solar irradiation in a building, thus improving buildings’ energy efficiency. Full article

In this work, we report the divergent synthesis of a novel corrole macrocycle with a T-shaped geometry, functionalized with triphenylamine (TPA) units. The synthetic route involved a green preparation of 5-(pentafluorophenyl)dipyrromethane, condensation with pentafluorobenzaldehyde, and DDQ oxidation to afford the target corrole. In parallel, a TPA-based chalcone derivative was obtained and introduced via regioselective nucleophilic aromatic substitution. The resulting photoactive corrole–TPA conjugate exhibited efficient electropolymerization, retaining the corrole chromophore while forming conductive TPB-linked films (TPB, tetraphenylbenzidine). Spectroelectrochemical studies confirmed reversible redox activity, color switching, and electrochromic behavior, highlighting its potential as a building block for photo- and electroactive devices. Full article