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Smart window is an attractive option for efficient heat management to minimize energy consumption and improve indoor living comfort owing to their optical properties of adjusting sunlight. To effectively improve the sunlight modulation and heat management capability of smart windows, here, we propose a co-assembly strategy to fabricate the electrochromic and thermochromic smart windows with tunable components and ordered structures for the dynamic regulation of solar radiation. Firstly, to enhance both illumination and cooling efficiency in electrochromic windows, the aspect ratio and mixed type of Au nanorods are tuned to selectively absorb the near-infrared wavelength range of 760 to 1360 nm. Furthermore, when assembled with electrochromic W 18 O 49 nanowires in the colored state, the Au nanorods exhibit a synergistic effect, resulting in a 90% reduction of near-infrared light and a corresponding 5 °C cooling effect under 1-sun irradiation. Secondly, to extend the fixed response temperature value to a wider range of 30–50 °C in thermochromic windows, the doping amount and mixed type of W-VO 2 nanowires are carefully regulated. Last but not the least, the ordered assembly structure of the nanowires can greatly reduce the level of haze and enhance visibility in the windows. Smart windows offer more efficient sunlight modulation and heat management. Here, the authors propose a co-assembly strategy to produce smart windows that combine electrochromic and thermochromic functions with tunable components and ordered structures for dynamic solar radiation regulation.

Electrochromic devices can modulate their light absorption under a small driving voltage, but the requirement for external electrical supplies causes response-lag. To address this problem, self-powered electrochromic devices have been studied recently. However, insensitivity to the surrounding light and unsatisfactory stability of electrochromic devices have hindered their critical applications. Herein, novel perovskite solar cell-powered all-in-one gel electrochromic devices have been assembled and studied in order to achieve automatic light adjustment. Two alkynyl-containing viologen derivatives are synthesized as electrochromic materials, the devices with very high stability (up to 70000 cycles) serves as the energy storage and smart window, while the perovskite solar cell with power-conversion-efficiency up to 18.3% serves as the light detector and power harvester. The combined devices can automatically switch between bleached and colored state to adjust light absorption with variable surrounding light intensity in real-time swiftly, which establish significant potentials for applications as modern all-day intelligent windows. The requirement for external electric supplies has significantly limited the application of electrochromic devices in modulating light absorption as smart windows. Here, the authors report automatic switching perovskite solar cells-powered all-in-one gel electrochromic device in response to surrounding light intensity in real-time.

Mo-doped WO 3 (Mo@WO 3 ) thin film electrode was prepared through the hydrothermal method with convenient and inexpensive steps. The microstructure and characterization of Mo@WO 3 thin film were studied through SEM, XRD, and EDS. The Cyclic voltammetry, Chronocoulometry, Transmission spectrum, and Optical transmittance response were studied by electrochemical workstation and optical fiber spectrometer. The results show that compared with single WO 3 film, Mo@WO 3 thin film improves the electrochromic properties, which provides a novel idea for electrochromic smart windows.

Electrochromic (EC) devices represent an emerging energy-saving technology, exhibiting the capability to dynamically modulate light and heat transmittance. Despite their promising potential, the commercialization of EC devices faces substantial impediments such as high cost, intricate fabrication process, and low optical contrast inherent in conventional EC materials relying on the ion insertion/extraction mechanism. In this study, we introduce an innovative “electrode-free” electrochromic (EC) device, termed the EECD, which lacks an EC-layer on the electrodes during device assembling and in the bleached state. This device features a simplified fabrication process and delivers superior optical modulation. It achieves a high optical contrast ranging from 68-85% across the visible spectrum and boasts a rapid response time, reaching 90% coloring in just 17 seconds. In addition, EECD exhibits stable cycling for over 10,000 cycles without noticeable degradation and maintains functionality across a broad temperature range (0 °C to 50 °C). Furthermore, the fabricated large-area devices (40 cm × 40 cm) demonstrate excellent tinting uniformity, suggesting excellent scalability of this approach. Our study establishes a paradigmatic breakthrough for EC smart windows. Cheng Yang and co-workers develop an “electrode-free” electrochromic window, featuring a simplified fabrication process and delivering superior optical modulation capability.

Transition metal oxides (TMOs) are promising electrochromic (EC) materials for applications such as smart windows and displays, yet the challenge still exists to achieve good flexibility, high coloration efficiency and fast response simultaneously. MXenes (e.g. Ti 3 C 2 T x ) and their derived TMOs (e.g. 2D TiO 2 ) are good candidates for high-performance and flexible EC devices because of their 2D nature and the possibility of assembling them into loosely networked structures. Here we demonstrate flexible, fast, and high-coloration-efficiency EC devices based on self-assembled 2D TiO 2 /Ti 3 C 2 T x heterostructures, with the Ti 3 C 2 T x layer as the transparent electrode, and the 2D TiO 2 layer as the EC layer. Benefiting from the well-balanced porosity and connectivity of these assembled nanometer-thick heterostructures, they present fast and efficient ion and electron transport, as well as superior mechanical and electrochemical stability. We further demonstrate large-area flexible devices which could potentially be integrated onto curved and flexible surfaces for future ubiquitous electronics. Though two-dimensional (2D) nanocomposite materials have been attractive for flexible electrochromic (EC) devices, achieving both high performance and durability remains a challenge. Here, the authors report high-performance, environmentally stable 2D MXene/transition metal oxide-based EC devices.

Thermochromic perovskite smart windows (TPWs) are a cutting-edge energy-efficient window technology. However, like most perovskite-based devices, humidity-related degradation limits their widespread application. Herein, inspired by the structure of medical masks, a unique triple-layer thermochromic perovskite window (MTPW) that enable sufficient water vapor transmission to trigger the thermochromism but effectively repel detrimental water and moisture to extend its lifespan is developed. The MTPW demonstrates superhydrophobicity and maintains a solar modulation ability above 20% during a 45-day aging test, with a decay rate 37 times lower than that of a pristine TPW. It can also immobilize lead ions and significantly reduce lead leakage by 66 times. Furthermore, a significant haze reduction from 90% to 30% is achieved, overcoming the blurriness problem of TPWs. Benefiting from the improved optical performance, extended lifespan, suppressed lead leakage, and facile fabrication, the MTPW pushes forward the wide applications of smart windows in green buildings. Thermochromic perovskite smart windows require humidity for operation, but too much can lead to degradation. Tso and coworkers demonstrate a mask-inspired system for humidity regulation, to extend lifespan and minimize optical haze.

Existing circularly polarized luminescence materials can hardly satisfy the requirements of both large luminescence dissymmetry factor and high luminescent quantum yield, which hinders their practical applications. Here, we present a soft photonic crystal film embedded with chiral nanopores that possesses excellent circularly polarized luminescence performance with a high luminescence dissymmetry factor as well as a large luminescent quantum yield when loaded with various luminescent dyes. Benefitting from the retention of chiral nanopores imprinted from a chiral liquid crystal arrangement, the chiral soft photonic crystal film can not only endow dyes with chiral properties, but also effectively avoid severe aggregation of guest dye molecules. More importantly, the soft photonic crystal film can be recycled many times by loading and eluting guest dye molecules while retaining good stability as well as circularly polarized luminescence performance, enabling various applications, including smart windows, multi-color circularly polarized luminescence and anticounterfeiting. Circularly polarized luminescence materials having simultaneously high dissymmetry factor and high luminescent quantum yield are desirable to improve applicability. Here, the authors report a soft photonic crystal film with chiral nanopores fulfilling these requirements when loaded with luminescent dyes.

All-solid-state electrochromic devices can be used to create smart windows that regulate the transmittance of solar radiation by applying a voltage. However, the devices suffer from a limited ion diffusion speed, which leads to slow colouration and bleaching processes. Here we report fast-switching electrochromic devices that are based on an all-solid-state tandem structure and use protons as the diffusing species. We use tungsten trioxide (WO 3 ) as the electrochromic material, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the solid-state proton source. This structure exhibits a low contrast ratio (that is, the difference between on and off transmittance); however, we add a solid polymeric electrolyte layer on top of PEDOT:PSS, which provides sodium ions to PEDOT:PSS and pumps protons to the WO 3 layer through ion exchange. The resulting electrochromic devices exhibit high contrast ratios (more than 90% at 650 nm), fast responses (colouration to 90% in 0.7 s and bleaching to 65% in 0.9 s and 90% in 7.1 s), good colouration efficiency (109 cm 2  C −1 at 670 nm) and excellent cycling stability (less than 10% degradation of contrast ratio after 3,000 cycles). We also fabricate large-area (30 × 40 cm 2 ) and flexible devices, illustrating the scaling potential of the approach. Solid-state tandem structures that use protons as the diffusing species can be used to create electrochromic devices that exhibit high contrast ratios, fast responses, good colouration efficiency and excellent cycling stability.

Living matter has the ability to perceive multiple stimuli and respond accordingly. However, the integration of multiple stimuli-responsiveness in artificial materials usually causes mutual interference, which makes artificial materials work improperly. Herein, we design composite gels with organic‒inorganic semi-interpenetrating network structures, which are orthogonally responsive to light and magnetic fields. The composite gels are prepared by the co-assembly of a photoswitchable organogelator (Azo-Ch) and superparamagnetic inorganic nanoparticles (Fe 3 O 4 @SiO 2 ). Azo-Ch assembles into an organogel network, which shows photoinduced reversible sol-gel transitions. In gel or sol state, Fe 3 O 4 @SiO 2 nanoparticles reversibly form photonic nanochains via magnetic control. Light and magnetic fields can orthogonally control the composite gel because Azo-Ch and Fe 3 O 4 @SiO 2 form a unique semi-interpenetrating network, which allows them to work independently. The orthogonal photo- and magnetic-responsiveness enables the fabrication of smart windows, anti-counterfeiting labels, and reconfigurable materials using the composite gel. Our work presents a method to design orthogonally stimuli-responsive materials. The integration of multiple stimuli-responsiveness in artificial materials usually causes mutual interference, which makes artificial materials work improperly. Here, the authors design composite gels with organic‒inorganic semi-interpenetrating network structures, which are orthogonally responsive to light and magnetic fields.

Thermochromic window develops as a competitive solution for carbon emissions due to comprehensive advantages of its passivity and effective utilization of energy. How to further enhance the solar modulation ( △ T sol ) of thermochromic windows while ensuring high luminous transmittance ( T lum ) becomes the latest challenge to touch the limit of energy efficiency. Here, we show a smart window combining mechanochromism with thermochromism by self-rolling of vanadium dioxide (VO 2 ) nanomembranes to enhance multi-level solar modulation. The mechanochromism is introduced by the temperature-controlled regulation of curvature of rolled-up smart window, which benefits from effective strain adjustment in VO 2 nanomembranes upon the phase transition. Under geometry design and optimization, the rolled-up smart window with high △ T sol and T lum is achieved for the modulation of indoor temperature self-adapted to seasons and climate. Furthermore, such rolled-up smart window enables high infrared reflectance after triggered phase transition and acts as a smart lens protective cover for strong radiation. This work supports the feasibility of self-rolling technology in smart windows and lens protection, which promises broad interest and practical applications of self-adapting devices and systems for smart building, intelligent sensors and actuators with the perspective of energy efficiency. In this work, authors demonstrate a smart window combining mechanochromism with thermochromism by self-rolling of VO 2 nanomembranes to modulate in-door temperature self-adapted to seasons and climate with high efficiency.