Search

Lower Critical Solution Temperature (LCST) of macromolecular systems is important in thermoresponsive smart window design. However, controlling the LCST behavior and sustaining the shelf‐life are challenging tasks. Herein, how photochemistry can be tweaked to design sustainable smart windows that allow controlled transmission of solar radiation is described. The cyanostilbene substituted naphthalenes 1(Z) and 2(Z), show Z/E‐photoisomerization and subsequent Mallory cyclization resulting in significant modulation in clouding temperatures (Tcloud). At 1 mM concentration, the Tcloud of 1(Z), and 1(E) are 33 ± 0.1 and 28 ± 0.13 °C, respectively whereas 2(Z) and 2(E) exhibit Tcloud around 37 ± 0.1 and 30 ± 0.1 °C, respectively. The high thermal barrier for the E/Z back isomerization of 1(E) and 2(E) and removal of oxygen from the reaction medium allow control of the photoprocesses, thereby facilitating the construction of sustainable smart windows that respond to the surrounding temperature. A 30 × 30 cm2 window prototype containing an aqueous solution of 1(Z) (1 mM) exhibits a fully transmissive state at 25 °C and a nearly zero‐transmissive state at 33 °C for 10,000 cycles of operation. [ABSTRACT FROM AUTHOR]

Electrochromic smart windows (ESWs) are an effective energy‐saving technology for near‐zero energy buildings. They consume electric energy unidirectionally during a round‐trip coloring‐bleaching process, with the energy involved in the bleaching process being wasted. It is highly desirable to reuse this wasted electric energy directly and/or transfer it into other energy storage equipment, further enhancing the overall efficiency of electric energy usage. Herein, a zinc anode‐based ESW (ESW‐PZ) is reported that not only has fascinating visible–near‐infrared (VIS‐NIR) dual‐band electrochromic performance (a high optical contrast of 63%) but also showcases good energy storage characteristics (a wide voltage window of 2.6 V and a high energy density of 127.5 µWh cm−2). The buildings utilizing ESW‐PZ to modulate indoor environments demonstrated an average annual energy saving of 366 MJ m−2 based on energy simulations, which is about 16% of the total energy consumption. Impressively, a high utilization efficiency of 90% (855 mWh m−2) of the wasted electric energy is realized through an ingenious circuit‐switching strategy, which can be reused to power small household appliances. [ABSTRACT FROM AUTHOR]

Energy‐efficient building materials are eye‐catching for reducing indoor energy consumption via eliminating electromagnetic interference and pollution, controlling the thermal transfer, and promoting sunlight harvesting and providing a comfortable living environment. To realize broadband microwave shielding, the elaborate control of microstructures has showed great potential and research direction. By composition regulation and structure design with various dimension, the synergistic effects including conductive networks, interfacial polarization, magnetic coupling, dipole polarization, and dielectric‐magnetic synergy, can significantly improve electromagnetic (EM) shielding capacity. Thermal management including thermal conversion, thermal storage, thermal radiation, and thermal conduction has enormous potential in enhancing the sustainability and energy efficiency for future buildings. Smart windows are able to switch optical transmittance and colors, which is contributed to saving building energy. Herein, in this review, the recent progress of broadband shielding, thermal management, and smart window in the field of energy‐efficient buildings is summarized, from the aspects of materials, mechanisms, and scenarios. Further, the main bottlenecks and problems are discussed, and potential research opportunities are further highlighted. [ABSTRACT FROM AUTHOR]

Harvesting low‐grade waste heat into electrical energy is recognized as a promising solution for sustainable energy supply. In parallel, thermotropic smart windows have emerged as an efficient way to reduce building energy consumption. It is posit that thermotropic smart windows with inherent thermoelectric property may offer unique advantages for practical applications. Herein, the preparation and characterization of a series of ionic hydrogels that exhibit temperature‐sensitive phase transition behavior is reported, which are suitable for both thermotropic smart windows and thermoelectric generators. Notably, the lower critical solution temperature (LCST) of this ionic hydrogels can be feasibly modulated, and the thermoteopic phase transition also induces a sharp increase in their Seebeck coefficient, reaching up to 39.03 mV K−1 with a power factor (PFi) value up to 0.838 mW m−1 K−2. A prototype dual functional thermotropic smart window that simultaneously works as an ionic thermoelectric generator is further demonstrated, achieving both efficient phase transition driven by solar heat at ≈26 °C and an energy density up to 250 mJ m−2. This study offers new opportunity for the development of smart materials that can bridge the gap between thermal comfort and energy sustainability for energy harvesting and smart building applicat. [ABSTRACT FROM AUTHOR]

Smart windows have the potential to respond dynamically and passively to external stimuli, controlling the amount of light passing through the window. When a smart window switches from a clear to a translucent state, energy flow through the window is partially attenuated, allowing a room to cool down passively, thereby reducing the energy and fossil fuel consumption for air conditioning. The smart window demonstrated here consists of a thermoresponsive liquid consisting of Tergitol 15‐S‐7, which can dynamically and passively switch the window's transmittance when a temperature of 39 °C is reached. It is also demonstrated how the transition temperature can be lowered by adding salts. Outdoor experiments in realistic environments show that the temperature of a model house built with a thermo‐responsive window can achieve an indoor temperature of 7 °C less than a control house with an ordinary window. This study quantifies the energy savings possible using such windows at the building scale for cooling and heating in different climates and times of the year. [ABSTRACT FROM AUTHOR]

Electrochromic (EC) thin films have received considerable attention due to their potential applications in various fields such as smart windows, electrochromic displays, and energy storage devices. This review highlights various methods used for the fabrication and functionalization of EC films for various applications. Various techniques for EC thin film deposition ranging from solution-processable, low-temperature approaches such as sol-gel, spin coating, dip coating, and spray pyrolysis, to advanced techniques for deposition such as physical vapor deposition, chemical vapor deposition, and sputtering are summarized in this review. In addition, various applications of EC thin films and the outcome of different deposition approaches on the opto-electrochromic properties of EC thin films have been discussed elaborately. This review has the potential to spark the interest of researchers from a broad range of disciplines, including photocatalysis, electrocatalysis, nanotechnology and materials science.

Optics has advanced through centuries of research into the fundamental properties of light and its interactions with matter. Within this rich history, one optical component stands out: the diffraction grating. Liquid crystals (LCs) have emerged as promising candidates in diffraction gratings. LCs are versatile and adaptable materials influenced by various external factors. Diffractive LC grating devices can be produced through methods such as photo alignment, using polymer walls, or employing patterned electrodes. However, photo alignment poses challenges in terms of manufacturing complexity, and using polymer walls is associated with some drawbacks, such as high driving voltage and slower response times, which must be considered in their application. Currently, research efforts are predominantly focused on manufacturing techniques involving patterned electrodes. In this review, we comprehensively explored the theoretical foundations underpinning diffraction gratings. Additionally, we summarized research on diffractive gratings based on LC using patterned electrodes and conducted a comparative analysis of the characteristics of each device.

[Display omitted] Stimuli-responsive poly(N -vinylcaprolactam) (PVCL)-based microgels, which could response to small external environmental changes, have attracted great interests in the fields of biomedicine and nanotechnology. However, the preparation of such microgels meets severe challenge due to their low incorporation efficiency and thermoresponsivity passivation. To address these issues, we select 3-(tert- butoxycarbonyl)- N- vinylcaprolactam (TBVCL), a carboxyl-functionalized VCL derivative, as a comonomer to develop pH/temperature dual-responsive microgels. TBVCL, with a structure similar to VCL, enhances incorporation efficiency and colloidal stability, while reducing thermoresponsivity passivation. The volume phase transition temperature (VPTT) of the microgels can be adjusted over a broad range (19.0–49.5 °C). Notably, the radial swelling ratios of the microgels can be modulated by pH, achieving a maximum swelling ratio of 3. The distinct changes in dissolution-precipitation behavior under different temperatures or pH conditions make these microgels suitable for applications such as smart windows and sensors. Furthermore, this novel approach for fabricating microgels with pH-tunable phase-transition temperatures demonstrates significant potential for the controlled release of nanoparticles (e.g., drugs, catalysts, and quantum dots) and the development of smart nanocrystal-polymer composite sensors. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A new gelator (BAzo‐Chol) comprising a diazocine core and two cholesterol units linked via carbamate groups has been designed and synthesized. Its gelation ability in several kinds of organic solvents is identified. Investigations with scanning electron microscopy (SEM), transmission electron microscopy (TEM), rheological measurements, and UV‐vis absorption and 1H NMR spectroscopy reveal that BAzo‐Chol can self‐assemble into elastically interpenetrating one‐dimensional nanostructures in organogels through a cooperative effect of the π‐π interactions, hydrogen‐bonding, and van der Waals forces. Moreover, the unconventional Z/E conformational transitions of these organogels, due to the inclusion of diazocine, endow the BAzo‐Chol gels with excellent photo‐responsive gel‐sol transition and remarkable visible light‐induced chromic properties. Lastly, due to its sensitive response to visible light accompanied by distinct changes in both colour and transparency of the gel‐sol transitions, the potential application of the current gelator in smart windows is signified. [ABSTRACT FROM AUTHOR]

This study proposes energy-efficient smart windows based on one-dimensional photonic crystal structures that operate without an external power source and discuss the design and analysis of the proposed smart window which is composed of SiO2/Vo2 layers, their interaction with light and heat, the effect of the incident waves angles and their potential to reduce energy consumption and radiation exposure. The proposed window proves the performance of blocking harmful rays of ultraviolet and infra-red region even the temperature, polarization and the incident wave angles change and transmitting visible light except the green color that the window appears with, which adds a beauty view to it. [ABSTRACT FROM AUTHOR]

Electrochromic (EC) thin films have received considerable attention due to their potential applications in various fields such as smart windows, electrochromic displays, and energy storage devices. This review highlights various methods used for the fabrication and functionalization of EC films for various applications. Various techniques for EC thin film deposition ranging from solution-processable, low-temperature approaches such as sol-gel, spin coating, dip coating, and spray pyrolysis, to advanced techniques for deposition such as physical vapor deposition, chemical vapor deposition, and sputtering are summarized in this review. In addition, various applications of EC thin films and the outcome of different deposition approaches on the opto-electrochromic properties of EC thin films have been discussed elaborately. This review has the potential to spark the interest of researchers from a broad range of disciplines, including photocatalysis, electrocatalysis, nanotechnology and materials science. [ABSTRACT FROM AUTHOR]

Optics has advanced through centuries of research into the fundamental properties of light and its interactions with matter. Within this rich history, one optical component stands out: the diffraction grating. Liquid crystals (LCs) have emerged as promising candidates in diffraction gratings. LCs are versatile and adaptable materials influenced by various external factors. Diffractive LC grating devices can be produced through methods such as photo alignment, using polymer walls, or employing patterned electrodes. However, photo alignment poses challenges in terms of manufacturing complexity, and using polymer walls is associated with some drawbacks, such as high driving voltage and slower response times, which must be considered in their application. Currently, research efforts are predominantly focused on manufacturing techniques involving patterned electrodes. In this review, we comprehensively explored the theoretical foundations underpinning diffraction gratings. Additionally, we summarized research on diffractive gratings based on LC using patterned electrodes and conducted a comparative analysis of the characteristics of each device. [ABSTRACT FROM AUTHOR]

Electrochromic (EC) mirrors fabricated using the electrodeposition of metals can dynamically transition between reflective and transparent states via the deposition and dissolution of the employed metals. In particular, the incorporation of an EC counter electrode enables the realization of an absorptive state under optimized applied voltage. Herein, we present reversible EC mirrors composed of Ag and WO 3 layers as the two electrodes, highlighting their EC properties in three optical transformation modes: transparent, reflective, and absorptive. The formation of Ag layers under optimized deposition conditions was confirmed, and the electrodeposited WO 3 layers exhibited compact or porous structures depending on the deposition conditions. The prepared Ag–WO 3 EC mirrors showed substantial transmittance modulation during the reflecting (53.7%) and coloring (63.5%) process. Interestingly, in comparison to the compact WO 3 , the EC mirrors with porous WO 3 layers exhibited dark-gray coloration in the reduced state, which was attributed to the localized surface plasmon resonance effect caused by codeposited Ag particles. [ABSTRACT FROM AUTHOR]

Smart windows are attractive considering their contribution to energy efficiency and privacy protection. However, the achievement of flexible reverse-mode film with good stability and well electro-optical performance for smart windows remains a fascinating challenge in recent years. Herein, we reported a low-driving-voltage, high-stability flexible reverse-mode liquid crystal/polymer composite film for energy-efficient smart windows by the formation of polymer structure with a polyhedral oligomeric silsesquioxane (POSS) core and strong epoxy resin as chains. The experimental results suggested that the polymer can not only stabilise the planar state of the cholesteric liquid crystal in the zero field but also provide enough support to the continuous liquid crystal phase on flexible substrate. Besides, the optimised optical device could be fully driven at 30 V (lower than safety voltage, 36 V) and keep contrast ratio of 100. Moreover, the flexible film showed outstanding optical regulation performance and excellent cycle stability under electric field. The strategy used in this research would open new doors for the development of energy-efficient smart windows in buildings. [ABSTRACT FROM AUTHOR]

Smart windows have become increasingly popular due to their ability to provide privacy protection, energy efficiency, and user control. Therefore, this technology has a wide range of applications in various fields such as construction, automotive, aviation, and renewable energy. However, commercialisation faces two significant challenges due to the slow response speed and low transmittance. This work demonstrates a 5CB-doped polymer-stabilised sphere-phase liquid crystal (PS-SPLC) smart window with sub-millisecond response time, which can be switched between transparent and scattering states by an electric field. The transmittance exceeds 90% when the voltage is on in the visible light range. This 5CB-doped PS-SPLC smart window has the potential to usher in a new era of smart window research. [ABSTRACT FROM AUTHOR]

The pursuit of energy‐saving materials and technologies has garnered significant attention for their pivotal role in mitigating both energy consumption and carbon emissions. In particular, thermochromic windows in buildings offer energy‐saving potential by adjusting the transmittance of solar irradiation in response to temperature changes. Radiative cooling (RC), radiating thermal heat from an object surface to the cold outer space, also offers a potential way for cooling without energy consumption. Accordingly, smart window and RC technologies based on thermochromic materials can play a crucial role in improving energy efficiency and reducing energy consumption in buildings in response to the surrounding temperature. Vanadium dioxide (VO2) is a promising thermochromic material for energy‐saving smart windows and RC due to its reversible metal‐to‐insulator transition, accompanying large changes in its optical properties. This review provides a brief summary of synthesis methods of VO2 nanostructures based on nanoparticles and thin films. Moreover, this review emphasizes and summarizes modulation strategies focusing on doping, thermal processing, and structure manipulation to improve and regulate the thermochromic and emissivity performance of VO2 for smart window and RC applications. In last, the challenges and recent advances of VO2‐based smart window and RC applications are briefly presented. [ABSTRACT FROM AUTHOR]

Thermochromic smart windows realize an intelligent response to changes in environmental temperature through reversible physical phase transitions. They complete a real-time adjustment of solar transmittance, create a livable indoor temperature for humans, and reduce the energy consumption of buildings. Nevertheless, conventional materials that are used to prepare thermochromic smart windows face challenges, including fixed transition temperatures, limited solar modulation capabilities, and inadequate mechanical properties. In this study, a novel thermochromic hydrogel was synthesized from 2-hydroxy-3-butoxypropyl hydroxyethyl celluloses (HBPEC) and poly(N-isopropylacrylamide) (PNIPAM) by using a simple one-step low-temperature polymerization method. The HBPEC/PNIPAM hydrogel demonstrates a wide response temperature (24.1–33.2 °C), high light transmittance (Tlum = 87.5%), excellent solar modulation (ΔTsol = 71.2%), and robust mechanical properties. HBPEC is a functional material that can be used to adjust the lower critical solution temperature (LCST) of the smart window over a wide range by changing the degree of substitution (DS) of the butoxy group in its structure. In addition, the use of HBPEC effectively improves the light transmittance and mechanical properties of the hydrogels. After 100 heating and cooling cycles, the hydrogel still has excellent stability. Furthermore, indoor simulation experiments show that HBPEC/PNIPAM hydrogel smart windows have better indoor temperature regulation capabilities than traditional windows, making these smart windows potential candidates for energy-saving building materials. [ABSTRACT FROM AUTHOR]

In hot climates, the large amount of cooling load in electric vehicle (EV) results in a lot of battery energy consumption, leading the decrease of driving range. With the widespread application of windows in EV, the electrochromic glass (EC) shows great prospect in lowering the cooling load. However, researches on the application of EC in EV lack the consideration of both passive cooling measures and passenger comfort, which limits the further application of EC. In this paper, we proposed an idea combining the novel techniques of both electrochromism and radiative cooling. Computational fluid dynamics (CFD) is modeled to simulate the application of electrochromic and radiative cooling coupled smart windows in hot parking conditions, exploring the improvement effect of the window on the thermal environment, comfort and energy saving of the EV. The results indicate that, under the intense sunlight with an outdoor temperature of 33 °C, activating the air conditioning to maintain an average interior temperature of 26 °C, the coupled windows reduced the cooling capacity of the air conditioning by 762 W compared to regular windows, which can further increase the range of EV. Meanwhile, compared to simple electrochromic fully colored glass, the integration of radiative cooling technology can lower the window surface temperature by up to 10.7 °C. Moreover, compared to regular windows, the coupled windows lowered the standard effective temperature (SET*) for passengers by approximately 7 °C, significantly improving comfort. These research findings are expected to provide guidance for optimizing window design and enhancing the performance of EV. [ABSTRACT FROM AUTHOR]

Silver vanadate nanorods were synthesized for the first time via co‐precipitation, followed by ambient drying. X‐ray diffraction (XRD), energy dispersive X‐ray (EDX), and scanning electron microscope (SEM) analyses were utilized to investigate the structure and morphology of the nanorods. The results of these analyses confirmed the fabrication of silver vanadate nanorods. Then, to check the ability of these nanostructures to be used in the smart window, their optical properties, including the visible–ultraviolet absorption spectrum and photoluminescence (PL), were studied. The results showed that this nanostructure has maximum absorption and emission at wavelengths of 530 and 670 nm, respectively. Next, the new smart window was made with a layer of silver vanadate nanorods, and wheat, barley, millet, and beet were placed under this smart window to perform phytochemical tests. It was observed that silver vanadate nanorods could shift the green wavelength to higher wavelengths and efficiently improve the phytochemical properties of the mentioned plants. [ABSTRACT FROM AUTHOR]

Smart windows with excellent near-infrared (NIR) light shielding capacity and controlled visible light transmittance are expected to reduce building energy consumption and improve indoor comfort. However, the ability of current thermochromic materials to regulate solar gain with the tunable extinction of phase-change materials is still far from optimum. In this work, an fluorine (F)-doped ATO (FATO) nanocrystals (NCs) are designed as a photothermal material to optimize the solar modulation of thermochromic hydrogels. F ion doping can modify the electronic structure of ATO, resulting in a high concentration of oxygen vacancies and free electrons, thereby enhancing the NIR absorption performance and photothermal conversion performance of the ATO NCs. On this premise, the designed smart window based on FATO NCs and thermochromic hydrogels exhibits the remarkable features of excellent NIR shielding, high initial visible transmittance and fast response speed. The window is capable of shielding 99.5% of the solar radiation from 300 to 2500 nm and permitting 75.0% of initial visible light. Moreover, the simulated indoor temperature of the smart window was 17.2 °C lower compared with the black one, demonstrating potentials in practical application of building energy saving. [Display omitted] • Novel chain-like FATO NCs were prepared by precipitation-hydrothermal method. • F-doping optimized electronic structure of ATO and improved the LSPR absorption. • The fabrication of FATO-PNC hydrogel provides a novel idea for smart window. • The smart window could shield 99.5% of solar radiation after optical switching. [ABSTRACT FROM AUTHOR]

Abstract Electrochromic smart windows (ESWs) are an effective energy‐saving technology for near‐zero energy buildings. They consume electric energy unidirectionally during a round‐trip coloring‐bleaching process, with the energy involved in the bleaching process being wasted. It is highly desirable to reuse this wasted electric energy directly and/or transfer it into other energy storage equipment, further enhancing the overall efficiency of electric energy usage. Herein, a zinc anode‐based ESW (ESW‐PZ) is reported that not only has fascinating visible–near‐infrared (VIS‐NIR) dual‐band electrochromic performance (a high optical contrast of 63%) but also showcases good energy storage characteristics (a wide voltage window of 2.6 V and a high energy density of 127.5 µWh cm−2). The buildings utilizing ESW‐PZ to modulate indoor environments demonstrated an average annual energy saving of 366 MJ m−2 based on energy simulations, which is about 16% of the total energy consumption. Impressively, a high utilization efficiency of 90% (855 mWh m−2) of the wasted electric energy is realized through an ingenious circuit‐switching strategy, which can be reused to power small household appliances.

The percentage of energy consumed by buildings is very large in industry. Recently, the cases of applying smart technology to efficiently improve the energy waste of these buildings are increasing, and this study targets Electrochromic (EC) smart windows. Smart window means a window that can freely change Visible Light Transmittance (VLT) and Solar Heat Gain Coefficient (SHGC). Since windows are the largest medium that can cause energy loss in buildings, the application of smart windows enables efficient energy management. However, this technology currently has a high-cost problem, so a partial application to windows is proposed. This study aims to analyze the relationship between partially applied smart windows and energy loads. Smart windows require an environment control strategy because windows are primarily to provide a comfortable indoor environment. An environmental control strategy was established according to the application area of the smart window, and Useful Daylight Illuminance (UDI) was used. In addition, the energy load of the smart window in which the environmental control strategy was established was derived, and the relationship with the partially applied area was analyzed. This study provides information on how much the partial application of smart windows can save energy wastage in buildings.

In the pursuit of sustainable technology, the synthesis of a novel biopolymer, C‐pBPV, through the polymerization of carboxymethyl cellulose sodium salt (CMC‐Na) and viologen (BPV), with ammonium persulfate as an initiator is presented. This groundbreaking process not only promises an eco‐friendly approach but also opens avenues for advanced applications in electrochromic devices (ECDs), particularly in smart windows, displays, and beyond. Departing from conventional multi‐layered approaches, the study underscores the significance of a single‐layer material. C‐pBPV serves both as an electro‐chrome and an electrolyte, making it a compelling material for ECDs. It is used to create a gel‐based electrochromic device G1 with exceptional bistable properties. Following, a systematically controllable device, G2 is accomplished, to enhance color‐switching capabilities by adding vitamin C as an electron mediator. Both devices exhibited outstanding electrochromic properties, showcasing dual‐band absorption in the Vis‐NIR region, with color transitions from transparency to a striking purple state at low voltages. Embracing an all‐in‐one layer configuration, this study set the stage for next‐generation smart windows that not only regulate solar light for energy conservation but also pioneer a more compact, user‐friendly design, prioritizing visual comfort, sustainability, and a tailored user experience. [ABSTRACT FROM AUTHOR]

Due to the ability to switch between transparent and light scattering states, polymer dispersed liquid crystals (PDLC) and polymer stabilised cholesteric liquid crystals (PSCLC) are widely used in smart windows and flexible displays. A novel double-layer optical switch fabricated from a PDLC-PVA-PSCLC structure has been developed in this study, and the optimal formulation of each layer of the structure was investigated. In addition, the effect of adding (spin-coating) nanoparticles on overall switch performance was investigated. The double-layer switch under optimal conditions achieved 89.1% UV shielding, which also possessed excellent layer-by-layer driving performance and was able to modulate the UV shielding rate according to the voltage, with a tunable range of 74.83%-94.33%. Consequently, this optical device holds great promise for significant improvement and application in smart windows and flexible displays. [ABSTRACT FROM AUTHOR]

Smart windows are crucial to dynamic control over light transmission to fulfill various demands in energy saving, privacy, and information display; however, most present technologies still perform a single function (often tint or haze adjustment) and require continuous electricity for operation. In this study, novel self‐assembled ionic liquid crystals (ILCs) doped with negative cholesteric liquid crystals (CLCs) to offer electrically switchable and stable scattering‐mode light modulators are presented. The novel smectic A phase based on the ILCs exhibits high solubility in the adopted nematics, enhancing the LC device's performance in several ways, including improved homogeneity, stable alignment quality, prolonged stability, and simplified fabrication. The LC device can potentially offer a dynamically rapid switching function between stable transparent (imperfect fingerprint textures) states and stable scattering (focal conic textures with small domains) states by using external stimuli and highly maintained multistable states for prolonged periods, even when the external stimuli are removed. The LC device also offers polarization‐independent scattering and transparent‐mode LC light modulators, low operating voltage, excellent contrast, and broad viewing angles. Its versatility and outstanding field‐off stability make it ideal for various applications such as smart lighting, building climate control, energy‐saving displays, and augmented reality (AR) glasses. [ABSTRACT FROM AUTHOR]

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

One of the remarkable choices for active smart window technology is adopting a metal active layer via reversible metal electrodeposition (RME). As the metal layer efficiently blocks the solar energy gain, even a hundred-nanometer-thick scale, RME-based smart window has great attention. Recent developments are mainly focused on the various cases of electrolyte components and composition meeting technological standards. As metal nanostructures formed through the RME process involve plasmonic phenomena, advanced analysis, including plasmonic optics, which is beyond Beer–Lambert's law, should be considered. However, as there is a lack of debates on the plasmonic optics applied to RME smart window technology, as research is mainly conducted through an exhaustive process. In this paper, in order to provide insight into the RME-based smart window development and alleviate the unclear part of plasmonic optics applied to the field, finite-difference time-domain electromagnetic simulations are conducted. In total, two extremely low-quality (Cr) and high-quality (Mg) plasmonic materials based on a nanoparticle array are considered as a metal medium. In addition, optical effects caused by the metal active layer, electrolyte, and nanoparticle embedment are investigated in detail. Overall simulations suggest that the effective refractive index is a decisive factor in the performance of RME-based smart windows. [ABSTRACT FROM AUTHOR]

Abstract The emergence of smart windows has been a pivotal innovation in the field of energy efficiency and carbon emission reduction, sparking considerable interest worldwide. This review consolidates the latest research developments in inorganic‐based photochromic materials for smart windows applications, encompassing the design of device architectures, and their implementation in enhancing energy conservation, augmenting comfort levels, and optimizing indoor environmental control. Finally, this review culminates in an insightful analysis of the challenges and constraints in the existing research landscapes, which illuminates guidance for the directions and perspectives of future research.

In this work, we conduct a detailed study to understand the photoelectrochromic properties of Al-Pt co-doped tungsten oxide (WO3). Similarly, we support the photoelectrochromic findings with material characterization, providing additional understanding of the photoelectrochromic performance exhibited by the prepared samples. Additionally, we discuss the effects of Al and Pt doping on photoelectrochromic performance in detail, with a focus on X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with EDS, X-ray photoelectron spectroscopy (XPS), and optical transmittance. XRD peaks confirm the presence of hexagonally-structured WO3 in the prepared samples with a polycrystalline nature, and a similar observation is confirmed via TEM analysis. Surface characterizations conducted through SEM and EDS analyses unveil the morphologies and particle sizes. Optical studies show a bandgap of 1.88 eV and 1.95 eV for Al doped and Al-Pt co-doped WO3, indicating bandgap shrinkage in comparison to the optical bandgap of WO3 of 2.36 eV. The Al-Pt co-doping results in a significant enhancement in photoelectrochromic performance, attaining an optical modulation of 43.61 % at 550 nm and consequently 85 % of the initial transmittance recovered after 2 h of bleaching in the dark. This is an improvement in comparison to the Al doped sample which attains a coloration depth of 43.15 % at 550 nm with only 75 % of the original transmittance being recovered after 2 h under dark conditions.

Metallo‐supramolecular polymers (MSPs) show reversible electrochromic (EC) properties by electrochemical redox of metal ions included in the polymers. This presentation introduces recent three research achievements on EC devices (ECDs) using MSPs: (1) fabrication of highly durable ECDs with cycle stability more than 100,000 times, (2) a new electro‐polymerization method of a thin MSP layer on an ITO‐coated glass or PET‐film, and (3) rewritable multicolor EC paper using MSPs. [ABSTRACT FROM AUTHOR]

This review focuses on the development and advancements in angular-selective smart windows, with particular emphasis on static windows utilizing guest–host liquid crystal (GHLC) systems. Angular-selective windows are designed to adjust their transmittance based on the angle of incident light, offering enhanced energy efficiency and visual comfort in both architectural and automotive applications. By leveraging the anisotropic absorption properties of dichroic dyes, GHLC-based windows can selectively block oblique sunlight while preserving clear visibility from normal viewing angles. Various liquid crystal (LC) alignment configurations, including vertically aligned, homogeneously aligned, hybrid aligned, uniformly lying helix, and twisted aligned LC cells, have been investigated to optimize light control for different installation angles, such as for automotive windshields and building windows. These advancements have demonstrated significant improvements in energy conservation and occupant comfort by reducing cooling demands and regulating sunlight penetration. This review summarizes key findings from recent studies, addresses the limitations of current technologies, and outlines potential future directions for further advancements in smart window technology.

A dual-band electrochromic supercapacitor device (DESCD) can be driven by an external power supply to modulate solar radiation, which is a promising energy-saving strategy and has broad application prospects in smart windows. However, traditional power supplies, such as batteries, supercapacitors, etc., usually face limited lifetimes and potential environmental issues. Hence, we propose a self-powered DESCD based on TiO2/WO3 dual-band electrochromic material and a ternary dielectric rotating triboelectric nanogenerator (TDR-TENG). The TDR-TENG can convert mechanical energy from the environment into electrical energy to obtain a high output of 840 V, 23.9 µA, and 327 nC. The as-prepared TDR-TENG can drive the TiO2/WO3 film to store energy with a high dual-band modulation amplitude of 41.6% in the visible (VIS) region and 84% in the near-infrared (NIR) region, decreasing the indoor–outdoor light–heat interaction and thereby reducing the building energy consumption. The self-powered DESCD demonstrated in this study has multiple functions of energy harvesting, energy storage, and energy saving, providing a promising strategy for the development of self-powered smart windows. [ABSTRACT FROM AUTHOR]

Thermochromic energy efficient windows dynamically regulate building energy exchange by changing their optical transmittance. Recently, thermochromic materials with different chromic mechanisms are developed to fulfill smart window demands. Advanced fabrication technologies for smart windows also lead to building energy efficiency optimization. In this Perspective, representative mechanisms and performances of promising thermochromic systems, including vanadium dioxide, hydrogels, perovskites, ionic liquids, and liquid crystals, are discussed. Furthermore, the emerging technology of radiative cooling is emphasized for future building energy saving. Building temperature regulation and energy saving based on smart windows will make great impacts on the global low carbon economy. [ABSTRACT FROM AUTHOR]

Cholesteric liquid crystals (CLCs) exhibit selective reflection due to their self-assembled helical superstructures. Reconfigurable templates can achieve integration functions via inducing processes of molecular assemblies. Here we demonstrate temperature self-adaptive and color-adjustable smart windows using CLCs, which are fabricated via the templating method and exhibit simultaneous reflections in the visible and infrared spectra. Reflection bands formed by the refilled CLC materials can be adjusted reversibly both upon thermal and electrical actuation. In CLC with adjustable reflection in the infrared, the central wavelength of the infrared reflection band can be adjusted from 950 nm to 1305 nm via temperature, and from 1150 nm to 950 nm via electric field. A temperature variation of 10.3 °C within 55 s was induced by the single-layer templated CLC cell, and a comfortable temperature range could be effectively maintained by the CLC cell in a varied environment. In CLC with dynamic color in the visible spectrum, color shifts from 530 nm to 650 nm tuned by temperature and from 530 nm to 440 nm adjusted by electric field were obtained. Temperature-responsive reflection in the infrared spectrum contributes to automatic thermal management, and electric-field-induced band shift in the visible spectrum enables active dynamic color adjustment. The presented templated CLC smart windows show considerable potential in energy conservation and biological clock regulation fields. [ABSTRACT FROM AUTHOR]

A freeze-resistant PNIPAM-based smart window with simultaneous regulation of solar and thermal radiation, which further improves the energy efficiency of the window and broadens its application range, showing good potential for reducing building energy consumption. [Display omitted] Adaptive regulation of solar and thermal radiation by windows in diverse (hot and cold) climates is essential to reduce building energy consumption. However, conventional hydrogel-based thermochromic smart windows lack thermal radiation regulation, and have difficulty to combine high solar regulation with excellent freezing resistance. It is challenging to integrate the above performance into one hydrogel-based thermochromic window. Here, we firstly prepared poly(N-isopropylacrylamide- co -N, N-dimethylacrylamide)/ethylene glycol (PNDE) hydrogels with tunable and excellent freezing resistance (below −100 °C) by adding the anti-freezing agent ethylene glycol, and assembled PNDE hydrogels, polyvinylidene fluoride and polymethyl methacrylate-silver nanowires panels into a freezing-resistant smart window with solar and thermal radiation regulation (STR). PNDE hydrogels had an excellent thermochromic performance with luminous transmittance (T lum) of 89.3 %, solar regulation performance (Δ T sol) of 80.7 % and tunable phase change temperature (τ c , 22–44 °C). The assembled STR window showed high T lum of 68.2 %, high Δ T sol of 62.6 %, suitable τ c of ∼30 °C and freezing resistance to low temperature of −27 °C. Moreover, the different thermal emissivity (0.94 and 0.68) of the two sides of the STR window gave it the ability of radiative cooling in hot climates and warm-keeping in cold climates. Compared to the conventional thermochromic windows, the STR window promotes heat dissipation in hot conditions while reduces heat loss in cold conditions and is applicable to diverse climates, which is a promising energy-saving device for reducing building energy consumption. [ABSTRACT FROM AUTHOR]

We demonstrate using a diffractive smart window with homogeneous-aligned (HA) liquid crystals (LCs) owing to the large spatial phase difference in all directions in the opaque state. The proposed grating cell had a high haze value (88.57%), which was 1.16 times higher than the previously reported vertically aligned (VA) grating cells because the proposed grating cell had a higher twist angle than what the VA grating cell had. Our proposed HA grating cell can be used in various smart window applications. [ABSTRACT FROM AUTHOR]

In this work, vanadium pentoxide (V2O5) and titanium-modified V2O5 thin films were synthesized using the sol-gel spin coating route. The effect of Ti-doping concentration on the electrochromic optical properties and atomic/electronic structures of V2O5 smart thin films is examined. As the doping concentration of Ti increases, the surface roughness of the films is reduced. The structure of the films is analyzed using X-ray diffraction (XRD) and Raman spectroscopy, while the electrochromic modulation of atomic and electronic structures is elucidated through Raman and X-ray absorption spectroscopy (XAS) conducted during lithiation and delithiation. The XRD patterns demonstrate that an increase in Ti concentration leads to a more amorphous structure of the films and a shift of the main diffraction peak to a lower angle, attributable to the enlarged spacing between the stacking layers resulting from the incorporation of Ti ions. Soft X-ray absorption spectroscopy (XAS) and in situ hard XAS of the V L-edge, the O K-edge, and the V K-edge revealed a reduction in the charge state of V and local atomic structural symmetry modification upon lithated coloration and delithiated bleaching process. The critical insights provided by in situ XAS provides reveal that a small amount of Ti has the ability to modify the interlayer distance and local atomic structure of V2O5, thereby improving its electrochromic switching rate and stability when utilized in smart windows.

We demonstrate using a diffractive smart window with homogeneous-aligned (HA) liquid crystals (LCs) owing to the large spatial phase difference in all directions in the opaque state. The proposed grating cell had a high haze value (88.57%), which was 1.16 times higher than the previously reported vertically aligned (VA) grating cells because the proposed grating cell had a higher twist angle than what the VA grating cell had. Our proposed HA grating cell can be used in various smart window applications.

Thermochromic smart windows realize an intelligent response to changes in environmental temperature through reversible physical phase transitions. They complete a real-time adjustment of solar transmittance, create a livable indoor temperature for humans, and reduce the energy consumption of buildings. Nevertheless, conventional materials that are used to prepare thermochromic smart windows face challenges, including fixed transition temperatures, limited solar modulation capabilities, and inadequate mechanical properties. In this study, a novel thermochromic hydrogel was synthesized from 2-hydroxy-3-butoxypropyl hydroxyethyl celluloses (HBPEC) and poly(N-isopropylacrylamide) (PNIPAM) by using a simple one-step low-temperature polymerization method. The HBPEC/PNIPAM hydrogel demonstrates a wide response temperature (24.1–33.2 °C), high light transmittance (Tlum = 87.5%), excellent solar modulation (ΔTsol = 71.2%), and robust mechanical properties. HBPEC is a functional material that can be used to adjust the lower critical solution temperature (LCST) of the smart window over a wide range by changing the degree of substitution (DS) of the butoxy group in its structure. In addition, the use of HBPEC effectively improves the light transmittance and mechanical properties of the hydrogels. After 100 heating and cooling cycles, the hydrogel still has excellent stability. Furthermore, indoor simulation experiments show that HBPEC/PNIPAM hydrogel smart windows have better indoor temperature regulation capabilities than traditional windows, making these smart windows potential candidates for energy-saving building materials.

Indium tin oxide (ITO) nanocrystals with different shapes and sizes were synthesized by one-pot method, and ITO nanocrystal films were prepared by spin-coating process. The near-infrared spectrum regulation properties of the films prepared by ITO nanocrystals with different morphologies and sizes were studied. The results show that the visible light transmittance of ITO nanocrystal film is 89.2%, and the resistivity is 54 Ω·cm after 5 spin coatings. The films prepared by uniform spherical ITO nanocrystals with an average diameter of (6.88±1.53) nm exhibit the best near-infrared spectrum regulation ability. After applying a voltage of ±2.5 V, the spectrum regulation at 2000 nm is 39.3%, and the optical density change is 0.43. The ITO nanocrystal film maintains high visible light transmittance before and after electrochromism. The electrochromism of ITO nanocrystals is caused by change of frequency and intensity of localized surface plasmon resonance(LSPR) caused by electron injection/extraction, and its electrochromic process is realized by capacitor charging and discharging.

Wrinkling phenomena has attracted wide attention owing to its applications in anticounterfeiting patterns, smart windows, flexible devices, and sensors, and the dynamic morphological transformations of wrinkle structure extend the application in dynamic displays, patterning, and surface wetting. However, developing simple and effective wrinkle morphology transformation strategies to design smart windows with good repeatability and stable properties presents ongoing challenges. In this paper, morphology transition of the wrinkle structure is presented to develop potential applications in smart window and pattern fabrication. At first, a nanoscale wrinkled structure was fabricated by immersing an ionic liquid mixed solution with poly-(vinylidene fluoride)-hexafluoropropylene over a colloidal assembly based on the mismatch modulus between the surface layer and the interior during solvent evaporation. The wrinkle structure can be erased to form a pattern by inkjet printing based on the ink-induced dispersion of the ionic liquid. Interestingly, the wrinkled and erased structures have completely opposite optical reversible responsiveness to humidity changes, which forms the basis of a smart window. This wrinkled structure shows promising applications in anticounterfeit patterning, smart windows, and antiglare materials, which provides guidelines for the development of wrinkled-based optic materials and devices. [ABSTRACT FROM AUTHOR]

Windows are one of the least energy-efficient components of a building. It allows energy to escape, leading to high cooling demand in summer and energy loss in winter. Sunlight and temperature in the building also affect people's health, comfort, and even productivity. As a result, controlling the heat and light entering the building dynamically is critical for improving the comfort of building occupants and reducing energy consumption. In this work, we develop a tunable smart window based on transparent dielectric elastomer actuators (DEAs) as an alternative solution to sunlight and temperature control. The transparency-tuning is achieved by creating wrinkles in a soft elastomer film made of waterborne polyurethane (WPU). The actuation mechanism is based on highly transparent dielectric elastomer actuators that use all solid-state stretchable transparent conductive polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)/(PEDOT:PSS/WPU) as compliant electrodes. The modulation range of the smart tunable window with direct viewing is achieved to be 35% to 90%, which is one of the largest among existing tunable windows. At the low-transparency state, the window can also effectively block the heat and decrease the temperature rise to 2°C over 200 s, while the ambient temperature rises by 6°C with direct sunlight. We anticipate that this transparency-tuning mechanism is potentially useful for privacy protection, smart glass, projector screens, displays, and camouflage. The heat isolation feature also has the potential to reduce carbon emissions and improve the sustainability of buildings and greenhouses. [ABSTRACT FROM AUTHOR]

Electrochromic smart windows have attracted much attention in energy-saving buildings because of their ability to selectively modulate visible (VIS) and near-infrared (NIR) light transmittance. As is known, the NIR region accounts for about 50% of the total solar radiation. Therefore, reducing the NIR transmittance of windows will play a crucial role in reducing the energy consumption of buildings. However, for most of the reported electrochromic materials (ECMs)-based windows, it remains a long-lasting challenge about how to achieve a low NIR transmittance during the past decades. In this work, we synthesize oxygen-deficient tungsten oxide (WO3−x) nanoflowers (NFs) by a simple and efficient method that is facile for their mass production. The WO3−x NFs exhibit low NIR transmittance of only 4.11%, 0.60%, and 0.19% at 1200, 1600, and 1800 nm, respectively, due to the localized surface plasmon resonance (LSPR) effect. Besides, the WO3−x NFs exhibit an excellent dual-band modulating ability for both VIS and NIR light. They are able to operate in three distinct modes, including a bright mode, a cool mode, and a dark mode. Moreover, the WO3−x NFs exhibit a fast bleaching/coloring time (1.54/6.67 s), and excellent cycling stability (97.75% of capacity retention after 4000 s). [ABSTRACT FROM AUTHOR]

Windows, as transparent intermediaries between the indoors and outdoors, have a significant impact on building energy consumption and indoor visual and thermal comfort. With the recent development of dynamic window structures, especially various attachment technologies, the thermal, visual, and energy performances of windows have been significantly improved. In this research, a new dynamic transparent louver structure sandwiched within conventional double-pane windows is proposed, designed, optimized, and examined in terms of energy savings in different climates. The uniqueness of the proposed design is that it autonomously responds to the seasonal needs prompted by solar heat gain through the use of thermally deflected bimetallic elements. Moreover, by integrating spectral selective louvers into the system design, the dynamic structure enables strong solar infrared modulation with a little visible variation. The optical and thermal properties of the dynamic glazing structure support about 30% and 16% seasonal variations in solar heat gains and visible transmittance, respectively. Furthermore, the potential energy savings were explored via parametric energy simulations, which showed significant potential for heating and cooling energy savings. This proposed design demonstrates a simple smart dynamic glazing structure driven by seasonal temperature differences, with significant solar heat control capabilities and minor effects on the visible or visual quality of the glazing system. [ABSTRACT FROM AUTHOR]

This paper describes the deposition of Nb doped vanadium dioxide (VO2) films on a glass substrate by metal organic decomposition (MOD) and their thermochromic properties. The difference in thermochromic properties of VO2 thin films on a glass substrate was investigated with and without a buffer layer of Hf0.5Zr0.5O2 (HZO). The phase transition temperature of VO2 thin film successfully reduced from 83°C to 43°C on a glass substrate with a buffer layer of HZO. Without a buffer layer of HZO, the thermochromic properties of VO2 thin films deteriorated comparing with a buffer layer of HZO. HZO buffer layer effectively suppresses the miniaturization of VO2 crystallite size of thin film due to Nb doping. Moreover, it would block out the diffusion of Al, Na, and Ca impurity ions from a glass substrate and the partial oxidation of VO2 thin films judging from XPS O1s spectra and XPS depth profile analysis. We conclude that the insertion of the HZO buffer layer is a useful technique for controlling the transition temperature of VO2 for the smart window applications by MOD. [ABSTRACT FROM AUTHOR]

We report the use of four-layer graphene (4LG) as a highly reliable transparent conductive electrode (TCE) for polymer-dispersed liquid crystal (PDLC)-based smart window devices. The adhesion between 4LG and the substrate was successfully improved through a water-induced interface-cleaning (WIIC) process. We compared the performance of a device with a WIIC-processed 4LG electrode with that of devices with a conventional indium tin oxide (ITO) electrode and a 4LG electrode without a WIIC. With the application of the WIIC process, the PDLC smart window with a 4LG electrode exhibited reduced turn-on voltage and haze compared to 4LG without the WIIC process and characteristics comparable to those of the ITO electrode. The WIIC-processed 4LG electrode demonstrated enhanced electrical properties and better optical performance, leading to improved device efficiency and reliability. Furthermore, our study revealed that the WIIC process not only improved the adhesion between 4LG and the substrate but also enhanced the compatibility and interfacial interactions, resulting in the superior performance of the smart window device. These findings suggest that 4LG with WIIC holds great promise as a transparent conductive electrode for flexible smart windows, offering a cost-effective and efficient alternative to conventional ITO electrodes. [ABSTRACT FROM AUTHOR]