Sol-gel-based porous Ti-doped tungsten oxide films for high-performance dual-band electrochromic smart windows

Dual-band electrochromic smart windows(DESWs)with independent control of the transmittance of near-infrared and visible light show great potential in the application of smart and energy-saving buildings.The current strategy for building DESWs is to screen materials for composite or prepare plasmonic nanocrystal films.These rigorous preparation processes seriously limit the further development of DESWs.Herein,we report a facile and effective sol-gel strategy using a foaming agent to achieve porous Ti-doped tungsten oxide film for the high performance of DESWs.The introduction of foaming agent polyvinylpyrrolidone during the film preparation can increase the specific surface area and free carrier concentration of the films and enhance their independent regulation ability of near-infrared electrochromism.As a result,the optimal film shows excellent dual-band electrochromic properties,including high optical modulation(84.9%at 633 nm and 90.3%at 1200 nm),high coloration efficiency(114.9 cm^(2) C^(-1) at 633 nm and 420.3 cm^(2) C^(-1) at 1200 nm),quick switching time,excellent bistability,and good cycle stability(the transmittance modulation losses at 633 and 1200 nm were 11%and 3.5%respectively after 1000 cycles).A demonstrated DESW fabricated by the sol-gel film showed effective management of heat and light of sunlight.This study represents a significant advance in the preparation of dual-band electrochromic films,which will shed new light on advancing electrochromic technology for future energy-saving smart buildings.

Novel self-assembled porous yolk-shell NiO nanospheres with excellent electrochromic performance for smart windows

With the rapid development of optoelectronics,electrochromic(EC)materials(ECMs)with the advan-tages of low power consumption,easy viewing,high contrast ratio,etc have attached more and more attention from the fields of smart windows,electronic billboards,emerging wearable and portable electronics,and other next-generation displays.Nickel oxide(NiO)is a promising candidate for high-performance ECMs because of its neutral-colored states and low cost.However,NiO-based ECMs still face the problem of slow switching speed due to their low electrical conductivity and small lattice spacing.Metal-organic frameworks(MOFs)are promising candidates to fabricate hollow and porous transition metal oxides(TMOs)with high ion transport efficiency,excellent specific capacitance,and electrochemical activities.In this work,porous yolk-shell NiO nanospheres(PYS-NiO NSs)were syn-thesized via a solvothermal and subsequent calcination process of Ni-MOF,which exhibited outstanding EC performance.Because the large specific surface areas and hollow porous nanostructures were conducive to ionic transport,PYS-NiO NSs exhibited a fast coloring/bleaching speed(3.6/3.9 s per one coloring/bleaching cycle)and excellent cycling stability(82%of capacity retention after 3000 cycles).These superior EC properties indicated that the PYS-NiO NSs was a promising candidate for high-performance EC devices.This work provides a new and feasible strategy for the efficient preparation of TMOs ECMs with good EC performance,especially fast switching speed.

Polyelectrolyte complex-based thermochromic hydrogels containing carbonized polymer dots for smart windows with fast response,excellent solar modulation ability,and high durability

Thermochromic smart windows have gained increasing popularity in light modulation and energy management in buildings.However,the fabrication of flexible thermochromic smart windows with high luminous transmittance(Tlum),tailorable critical temperature(τc),strong solar modulation ability(ΔTsol),and long-term durability remains a huge challenge.In this study,hydrogel-based thermochromic smart windows are fabricated by sandwiching thermochromic hydrogels of polyallylamine hydrochloride,polyacrylic acid,and carbonized polymer dots(CPDs)complexes between two pieces of transparent substrates.Benefiting from the incorporation of nanosized CPDs,the thermochromic hydrogel has an ultrahigh Tlum of~98.7%,a desirableτc of~24.2℃,aΔTsol of~89.3%and a rapid transition time of~3 s from opaque state to transparent state.Moreover,the thermochromic hydrogel exhibits excellent anti-freezing ability,tight adhesion toward various substrates,and excellent self-healing capability.The self-healing capability enables the fabrication of large-area smart windows by welding multiple hydrogel pieces.The smart windows retain their original thermochromic properties after being stored under ambient conditions for at least 147 days or undergoing 10,000 uninterrupted heating/cooling cycles.The model houses with smart windows can achieve a temperature reduction of 9.2℃,demonstrating the excellent indoor temperature modulation performance of the smart windows.

An overview and experimental analysis of WO_(3)/TiO_(2)composite with enhanced electrochromic properties for smart windows application

Internationally,standards for electrochromic(EC)requirements in smart window applications have been established,with ongoing global initiatives aimed at elevating them to highly advanced levels.This paper covers a comprehensive investigation of the structural,optical,morphological,and electrochemical properties of WO_(3)/TiO_(2)composite films.Simultaneously,an experimental analysis of WO_(3)/TiO_(2)was envisaged by a two-step process.Initially,WO_(3)thin films were hydrothermally deposited onto indium-doped tin oxide-coated glass substrates using an aqueous solution of Na_(2)WO_(4)·2H_(2)O at a pH value of 1.Subsequently,a layer of TiO_(2)was electrodeposited onto the WO_(3)thin films.X-ray diffraction analysis confirmed the successful formation of WO_(3)/TiO_(2)composite films,with the WO_(3)phase exhibiting a hexagonal tunnel structure.Scanning electron microscopy revealed the formation of porous nanorods(NRs)of WO_(3),uniformly coated with TiO_(2),resulting in a porous morphology of the WO./TiO_(2)samples.The EC performance of the WO_(3)/TiO_(2)films was thoroughly assessed through cyclic voltammetry and chronoamperometry measurements over a potential window ranging from-2.0 to+1.2 V(versus Ag/AgCl)in a 0.5 mol·L^(-1)LiClO_(4)-PC electrolyte.The WO_(3)/TiO_(2)composite films exhibited cathodic electrochromism,characterized by a reversible color change from dark blue to transparent.This improved EC performance in comparison to pure WO_(3)films is attributed to enhanced double ion/electron insertion and extraction efficiency.Furthermore,the WO_(3)/TiO_(2)composite films demonstrated excellent optical modulation properties,with a significant modulation at 633 nm(46.87%).The coloration efficiency reached a high value of 193.25 cm^(2)·C^(-1),indicating their potential for practical EC applications.Moreover,the WO_(3)/TiO_(2)composite films displayed exceptional EC stability,with no significant degradation observed over 2500 cyclic voltammetry cycles.This superior EC performance can be attributed to the synergistic effect between the hexagonal WO_(3)NRs and anatase TiO_(2).This study highlights the significance of the synthesis method and the unique structural characteristics of the composite in enhancing the EC performance.

Active and passive modulation of solar light transmittance in a uniquely multifunctional dual-band single molecule for smart window applications

Functional materials may change color by heat and electricity separately or simultaneously in smart windows.These materials have not only demonstrated remarkable potential in the modulation of solar radiation but are also leading to the development of indoor environments that are more comfortable and conducive to improving individuals'quality of life.Unfortunately,dual-responsive materials have not received ample research attention due to economic and technological challenges.As a consequence,the broader utilization of smart windows faces hindrances.To address this new generational multistimulus responsive chromic materials,our group has adopted a developmental strategy to create a poly(NIPAM)n-HV as a switchable material by anchoring active viologen(HV)onto a phase-changing poly(NIPAM)n-based smart material for better utility and activity.These constructed smart windows facilitate individualistic reversible switching,from a highly transparent state to an opaque state(thermochromic)and a red state(electrochromic),as well as facilitate a simultaneous dual-stimuli response reversible switching from a clear transparent state to a fully opaque(thermochromic)and orange(electrochromic)states.Absolute privacy can be attained in smart windows designed for exclusive settings by achieving zero transmittance.Each unique chromic mode operates independently and modulates visible and near-infrared(NIR)light in a distinct manner.Hence,these smart windows with thermal and electric dual-stimuli responsiveness demonstrate remarkable heat regulation capabilities,rendering them highly attractive for applications in building facades,energy harvesting,privacy protection,and color display.

Oxygen-deficient tungsten oxide nanoflowers for dynamically tunable near-infrared light transmittance of smart windows

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 longlasting challenge about how to achieve a low NIR transmittance during the past decades.In this work,we synthesize oxygendeficient tungsten oxide(WO_(3−x))nanoflowers(NFs)by a simple and efficient method that is facile for their mass production.The WO_(3−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 WO_(3−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 WO_(3−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).

Reversible Zn^(2+) Insertion in Tungsten Ion-Activated Titanium Dioxide Nanocrystals for Electrochromic Windows

Zinc-anode-based electrochromic devices(ZECDs) are emerging as the next-generation energy-e cient transparent electronics. We report anatase W-doped TiO_(2) nanocrystals(NCs) as a Zn^(2+) active electrochromic material. It demonstrates that the W doping in TiO_(2) highly reduces the Zn^(2+) intercalation energy,thus triggering the electrochromism. The prototype ZECDs based on W-doped TiO_(2) NCs deliver a high optical modulation(66% at 550 nm),fast spectral response times(9/2.7 s at 550 nm for coloration/bleaching),and good electrochemical stability(8.2% optical modulation loss after 1000 cycles).

3D printed hydrogel for soft thermo-responsive smart window

Smart windows with tunable optical properties that respond to external environments are being developed to reduce energy consumption in buildings.In the present study,we introduce a new type of 3D printed hydrogel with amazing flexibility and stretchability(as large as 1500%),as well as tunable optical performance controlled by surrounding temperatures.The hydrogel on a PDMS substrate shows transparent-opaque transition with high solar modulation(ΔT_(sol))up to 79.332% around its lower critical solution temperature(L_(CST))while maintaining a high luminous transmittance(T_(lum))of 85.847% at 20℃.In addition,selective transparent-opaque transition above LCST can be achieved by patterned hydrogels which are precisely fabricated via a projection micro-stereolithography based 3D printing technique.Our hydrogel promises great potential applications for the next generation of soft smart windows.

An Electrochromic Nickel Phosphate Film for Large-Area Smart Window with Ultra-Large Optical Modulation

Exploring materials with high electrochemical activity is of keen interest for electrochemistry-controlled optical and energy storage devices.However,it remains a great challenge for transition metal oxides to meet this feature due to their low electron conductivity and insufficient reaction sites.Here,we propose a type of transition metal phosphate(NiHPO_(4)·3H_(2)O,NHP)by a facile and scalable electrodeposition method,which can achieve the capability of efficient ion accommodation and injection/extraction for electrochromic energy storage applications.Specifically,the NHP film with an ultra-high transmittance(approach to 100%)achieves a large optical modulation(90.8%at 500 nm),high coloration efficiency(75.4 cm^(2)C^(-1)at 500 nm),and a high specific capacity of 47.8 mAh g^(-1)at 0.4 A g^(-1).Furthermore,the transformation mechanism of NHP upon electrochemical reaction is systematically elucidated using in situ and ex situ techniques.Ultimately,a large-area electrochromic smart window with 100 cm^(2)is constructed based on the NHP electrode,displaying superior electrochromic energy storage performance in regulating natural light and storing electrical charges.Our findings may open up new strategies for developing advanced electrochromic energy storage materials and smart windows.

Design of Intelligent Window Automatic Monitoring System Based on Microcontroller Control

To ensure the safety of residents’lives and property by using automatic opening and closing of ordinary windows,this article designs an intelligent window automatic monitoring system.The article proposes a software and hardware design scheme for the system,which comprises a microcontroller control module,temperature and humidity detection module,harmful gas detection module,rainfall detection module,human thermal radiation induction module,Organic Light-Emitting Diode(OLED)display module,stepper motor drive module,Wi-Fi communication module,etc.Users use this system to monitor environmental data such as temperature,humidity,rainfall,harmful gas concentrations,and human health.Users can control the opening and closing of windows through manual,microcontroller,and mobile application(app)remote methods,providing users with a more convenient,comfortable,and safe living environment.

Intelligent windows for electricity generation: A technologies review

Buildings are responsible for over 40% of total primary energy consumption in the US and EU and therefore improving building energy efficiency has significant potential for obtaining net-zero energy buildings reducing energy consumption. The concurrent demands of environmental comfort and the need to improve energy efficiency for both new and existing buildings have motivated research into finding solutions for the regulation of incoming solar radiation, as well as ensuring occupant thermal and visual comfort whilst generating energy onsite. Windows as building components offer the opportunity of addressing these issues in buildings. Building integration of photovoltaics permits building components such as semi-transparent façade, skylights and shading devices to be replaced with PV. Much progress has been made in photovoltaic material science, where smart window development has evolved in areas such as semi-transparent PV, electrochromic and thermochromic materials, luminescent solar concentrator and the integration of each of the latter technologies to buildings, specifically windows. This paper presents a review on intelligent window technologies that integrate renewable energy technologies with energy-saving strategies contributing potential solutions towards sustainable zero-energy buildings. This review is a comprehensive evaluation of intelligent windows focusing on state-of-the-art development in windows that can generate electricity and their electrical, thermal and optical characteristics. This review provides a summary of current work in intelligent window design for energy generation and gives recommendations for further research opportunities.

Smart window of large transparency-tuning capacity

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℃over 200 s,while the ambient temperature rises by 6℃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.

Triboelectric-optical responsive cholesteric liquid crystals for self-powered smart window,E-paper display and optical switch

Intelligent responsive devices are crucial for a variety of applications ranging from smart electronics to robotics.Electro-responsive cholesteric liquid crystals(CLC)have been widely applied in display panels,smart windows,and so on.In this work,we realize the mechanical stimuli-triggered optical responses of the CLC by integrating it with a triboelectric nanogenerator(TENG),which converts the mechanical motion into alternating current electricity and then tunes the different optical responses of the CLC.When the voltage applied on the CLC is relatively low(15–40 V),the TENG drives the switching between the bistable planar state and focal conic state of the CLC,which shows potential applications in selfpowered smart windows or E-paper displays.When the voltage supplied by the TENG is larger than60 V,a self-powered optical switch is demonstrated by utilizing the transformation between focal conic state and instantons homeotropic state of the CLC.This triboelectric-optical responsive device consumes no extra electric power and suggests a great potential for future smart electronics.

Recent progress in Prussian blue electrode for electrochromic devices

Great progress has been made in the electrochromic(EC)technology with potential applications in various fields.As one of the most promising EC materials,Prussian blue(PB)has attracted great attention due to its excellent EC performance,such as low cost,easy synthesis,rich color states,chemical stability,suitable redox potential,and fast color-switching kinetics.This review summarizes the recent progress in PB electrodes and devices,including several typical preparation techniques of PB electrodes,as well as the recent key strategies for enhancing EC performance of PB electrodes.Specifically,PB-based electrochromic devices(ECDs)have been widely used in various fields,such as smart windows,electrochromic energy storage devices(EESDs),wearable electronics,smart displays,military camouflage,and other fields.Several opportunities and obstacles are suggested for advancing the development of PB-based ECDs.This comprehensive review is expected to offer valuable insights for the design and fabrication of sophisticated PBbased ECDs,enabling their practical integration into realworld applications.

Electrochemically driven dynamic plasmonics

Dynamic plasmonics with the real-time active control capability of plasmonic resonances attracts much interest in the communities of physics,chemistry,and material science.Among versatile reconfigurable strategies for dynamic plasmonics,electrochemically driven strategies have garnered most of the attention.We summarize three primary strategies to enable electrochemically dynamic plasmonics,including structural transformation,carrier-density modulation,and electrochemically active surrounding-media manipulation.The reconfigurable microstructures,optical properties,and underlying physical mechanisms are discussed in detail.We also summarize the most promising applications of dynamic plasmonics,including smart windows,structural color displays,and chemical sensors.We suggest more research efforts toward the widespread applications of dynamic plasmonics.

Ultra-strong anti-freezing hydrogel-based smart window with wide geographical adaptability

Smart windows,capable of dynamically regulating indoor heat,offer a promising avenue for effectively reducing energy consumption.Hydrogel-based smart windows are excellent at thermal modulation and daylighting,but they are difficult to commercialize globally due to problems like winter ice formation,which can affect thermal insulation,daylighting,and structural integrity,as well as an impractical cloud point temperature(t_(cp)).To solve these issues,a ternary anti-freezing system consisting of ethylene glycol(EG),glycerol,and water is proposed.With the t_(cp)regulated at 31.6℃,the system strikes a balance between outstanding daylighting(91.89%)and solar modulation ability(78.32%).Furthermore,the system shows resilience even below-30.0℃and long-term stability,which qualifies it for use in densely populated regions even with severely cold weather.To further illustrate the distinct impacts of EG and glycerol,the optical characteristics and tcpof binary systems containing EG and water as well as glycerol and water were examined.The durability test includes severely cold temperature of-30.0℃ and solar exposure temperature of 60.0℃.This work would offer insights to advance the field's understanding of antifreezing capability modification in smart windows and advance the development of environmentally and energy-efficiently designed buildings.

CaF_(2):A novel electrolyte for all solid-state electrochromic devices

The energy consumption in building ventilation,air,and heating conditioning systems,accounts for about 25%of the overall energy consumption in modern society.Therefore,cutting carbon emissions and reducing energy consumption is a growing priority in building construction.Electrochromic devices(ECDs)are considered to be a highly promising energy-saving technology,due to their simple structure,active control,and low energy input characteristics.At present,Hþ,OH-and Liþare the main electrolyte ions used for ECDs.However,Hþand OH-based electrolytes have a high erosive effect on the material surface and have a relatively short lifetime.Liþ-based electrolytes are limited due to their high cost and safety concerns.In this study,inspired by prior research on Ca^(2+)þbatteries and supercapacitors,CaF_(2)films were prepared by electron beam evaporation as a Ca^(2+)þ-based electrolyte layer to construct ECDs.The structure,morphology,and optical properties of CaF_(2)films were characterized.ECDs with the structure of ITO(indium tin oxide)glass/WO3/CaF_(2)/NiO/ITO show short switching times(22.8 s for the coloring process,2.8 s for the bleaching process).Additionally,optical modulation of the ECDs is about 38.8%at 750 nm.These findings indicate that Ca^(2+)þbased ECDs have the potential to become a competitive and attractive choice for large-scale commercial smart windows.

Recent research progress on mixed valence state tungsten based materials

Synthesis and characterization of tungsten based mixed valence state nanoparticles and their novel applications are reviewed.The mixed valence state tungsten based homogeneous nanomaterials such as bronze structure M_(x)WO_(3)(M=Na^(+),K^(+),Rb^(+),Cs^(+),NH_(4)^(+),etc.)and tungsten sub-oxide W_(18)O_(49) possess excellent infrared(IR)light shielding property,implying their great potential applications on heat ray shielding and indoor energy saving effect in summer season.Also,some novel properties such as electric conductivity,bio thermal therapy function and electrochromic properties of mixed valence state tungsten based materials are introduced.The design of components,formation of composites and structure control of thin films are expected to realize the property enhancement and candidates for practice application as window materials.The multifunc-tionality of the mixed valence state based composites also implies great potential on novel applications of various building materials.

Finely Tuning the Lower Critical Solution Temperature of Ionogels by Regulating the Polarity of Polymer Networks and Ionic Liquids

Nonvolatile ionogels have recently emerged as promising soft electrolyte materials due to their high ionic conductivity and good durability.However,the compatibility between polymer networks and ionic liquids(ILs),which show significant influence on the physicochemical properties of the ionogels,has been rarely studied.Herein,we elucidate a lower critical solution temperature(LCST)-type phase behavior of ionogels composed of polyacrylates and hydrophobic 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ILs.We systematically study the structural effects of ILs and monomers on the LCST of ionogels.Our work illustrates that the LCST of ionogels is primarily determined by the polarity of polymer side chains and the alkyl chain on cations of ILs.The oriented solvation between polymers and ILs caused by hydrogen-bonding effects and van der Waals interactions may serve as the driving force for the LCST phase behavior in our system.Furthermore,by varying the mixing ratio of two structurally similar ILs in their blends,the LCST of ionogels can be tuned to exhibit a linear variation within a wide temperature range(from subzero to over 200℃).Finally,thermoresponsive ionogels with desired patterns are prepared using photomasks.These nonvolatile ionogels with tunable LCST enriched the functionality of state-of-the-art ionogels,which provides insight into the design and fabrication of smart and flexible electronic/optical devices.

Design and optimization of thermally responsive autonomous dynamic glazed attachment systems for building solar heat gain control

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.