Guofa Cai

Smart windows offer energy‐saving potential for buildings, while challenges remain in achieving multi‐band design across ultraviolet‐visible‐near infrared‐long wavelength infrared (UV–VIS‐NIR‐LWIR). Here we present a smart window integrating a thermochromic poly (EEEA‐co‐NIPAM) (PEN) hydrogel with an anti‐UV layer and an indium tin oxide layer, enabling dynamic VIS‐NIR solar modulation alongside UV shielding and low LWIR emissivity ( ɛ _LWIR ). Combined experimental and theoretical analyses reveal that 2‐(2‐ethoxyethoxy) ethyl acrylate (EEEA) comonomer strengthens the polymer network and forms favorable hydrogen‐bonding interactions with N‐isopropylacrylamide (NIPAM), promoting rapid dehydration‐driven chain collapse above a reduced lower critical solution temperature, and accelerating the optical response during heating. The produced window achieves a solar modulation (Δ Т _sol ) of 42.7%, nearly complete UV shielding ( T _UV = 0.1%), and low indoor‐facing ɛ _LWIR = 0.31, with stable performance after 100‐h UV exposure and 100 thermal cycles. Outdoor tests demonstrate a 7.7°C cooling effect compared with ordinary glass, while EnergyPlus simulations demonstrate up to 62.6% savings in building heating/cooling energy in Singapore, San Francisco, and Brisbane. This work provides an effective multiband strategy for smart windows together with an in‐depth understanding of thermochromic hydrogel, and is expected to inspire future efforts toward spectrally selective, energy‐efficient building glazing.

电致变色器件能够通过外加电场可逆调控其光学性质，发展具有可见光-近红外-中红外多波段协同或独立调控能力的新一代电致变色器件，以实现对太阳辐射热量与红外辐射特性的智能管理，已成为推动智能热管理技术与自适应伪装发展的重要方向。本综述系统梳理了多波段电致变色器件的研究进展，重点从材料创新与器件设计两个维度进行阐述。文章深入剖析了通过极化子吸收、局域表面等离子体共振与发射率调制分别实现可见光、近红外及中红外调控的机制；进而详细论述了从双波段同步/独立调控到三波段集成的先进器件设计，涵盖了单组分缺陷工程、异质结构筑、电解质工程及器件结构演化等多种创新方案；最后，本文分析了多波段电致变色器件在智能温控与自适应伪装中的应用潜力，并展望了其在光谱独立调控与循环稳定性、器件大面积制备等方面的未来发展方向。

Multivalent‐ion‐based electrochromic devices have attracted considerable attention for their excellent coloration efficiency and optical modulation. However, they remain limited by slow switching speeds and insufficient cycling stability due to the strong interactions between multivalent ions and host materials. To address this, we report a niobium tungsten titanium oxide metamaterial (Nb ₁₈ W ₈ Ti ₈ O ₈₅ , NbWTO) as a high‐performance Ca ²⁺ ‐based electrochromic material. The introduction of Ti expands the lattice channels and enhances the electrical conductivity, facilitating rapid Ca ²⁺ diffusion and improving structural robustness. By integrating NbWTO with a Ca ²⁺ /K ⁺ hybrid electrolyte and a Prussian Blue (PB) ion storage layer, we construct a device where Ca ²⁺ primarily drives the NbWTO coloration while K ⁺ enables fast and reversible PB redox. This ion division of labor, along with enhanced conductivity of NbWTO and well‐matched charge capacity between NbWTO and PB, yields exceptional performance: high optical modulation of 76.4% at 633 nm, sub‐second coloration time of 0.5 s, high coloration efficiency of 191.1 cm ² C ⁻¹ , and excellent cycling stability. Furthermore, a large‐area device (20 × 20 cm ² ) demonstrates scalability. This work provides a holistic design strategy integrating lattice engineering and dual ion synergy for advanced multivalent ion electrochromic devices.

Inkjet printing offers a promising non‐contact route toward high‐throughput, large‐area manufacturing of functional films for next‐generation optoelectronic devices. However, the broader adoption in continuous production lines is hindered by the coffee‐ring effect that compromises film uniformity. Additionally, existing printable inks rely predominantly on nanoscale particles (2 V ₆ O ₁₆ ·1.5H ₂ O (KVO) and a water/1,2‐propylene glycol (1,2‐PG) cosolvent system. The optimized ink exhibits excellent rheological properties for stable ejection, even with micron‐sized particles. Critically, the 1,2‐PG effectively inhibits the coffee‐ring effect by reducing the surface tension, allowing uniform deposition of large particles without the use of insulating surfactants. Therefore, a continuously patterned electrochromic film can be directly printed, which exhibits reversible multicolor transitions and remarkable cycling stability. Furthermore, we assembled a large‐scale electrochromic device (21.0 × 29.7 cm ² ) with a complex pattern based on the printed KVO film, which demonstrates uniform and reversible color changes across the active area. Our ink formulation offers a green, surfactant‐free alternative to traditional electrochromic inks and demonstrates that large‐sized functional particles can be uniformly printed via synergistic Marangoni flow and viscosity control, expanding the material scope for inkjet‐printed electrochromic devices.

Bistable electrochromic materials capable of retaining their optical states without sustained electrical power are critically important for energy‐saving technologies. Unfortunately, metal‐organic frameworks (MOFs) have remained largely underexplored for such applications, primarily due to the poor stability of radical intermediates involved in the EC processes. Herein, we propose a c‐axis‐dominated Ni‐based MOF film, denoted Ni‐BPA, fabricated via electrostatic spraying deposition, demonstrating remarkable bistable electrochromism with merely 8% transmittance loss after 12 h in the air (17% after 72 h). The film features reversible switching between a highly transparent and a neutral dark‐brown state, affording a large optical modulation of 78% at 490 nm and a high coloration efficiency of 88.57 cm ² C ⁻¹ . Notably, the colored patterns remain clearly visible for over 5 h in electrolyte and more than 24 h in air after powering off. Through in situ Raman and EPR spectroscopy, we identify the Ni ²⁺ /Ni ³⁺ redox couple as the central electrochromic mechanism. Further supported by DFT calculations, we elucidate that strong adsorption of hydroxide ions (−1.5 eV) plays a key role in stabilizing the colored state. This work establishes MOFs as promising platforms for bistable electrochromism, opening new pathways toward advanced energy‐efficient electronic devices.

Electrochromic devices are expected to operate reliably over a wide range of temperatures, requiring the electrolyte layer to maintain stability under varying environmental conditions. Herein, by introducing the neutral LiCl, we develop a temperature-adaptive hydrogel electrolyte with high ionic conductivity of 6 mS cm⁻¹ at −25 °C, 18 mS cm⁻¹ at RT and 24 mS cm⁻¹ at 80 °C and a transmittance of ∼96%. The electrochromic devices constructed by pairing the hydrogel with an inert Cu electrode and WO₃ thin films show a wide-temperature electrochromic response with amazing optical modulation (72.7% at −25 °C, 86% at RT, and 77% at 60 °C), fast coloring response times as low as 10.8 s at −25 °C, and superior cycling stability with 93.5% retention of their initial transmission modulation after 1000 cycles. This study provides a feasible strategy for developing cost-effective and safe electrochromic devices with super application potential.

Metal nanowire-based transparent electrodes have emerged as promising alternatives to conventional indium tin oxide (ITO) due to their excellent electrical conductivity and mechanical flexibility. However, weak adhesion between metal nanowires and conventional substrates results in poor mechanical stability. Moreover, random silver nanowire (Ag NW) nanostructures in conventional electrodes leads to high junction resistance and light scattering, reducing conductivity and transparency. Herein, we develop highly stable and flexible transparent electrodes by embedding micromesh-structured Ag NWs in hydroxyl-rich cellulose. Benefiting from strong coordination bonding between the Ag NWs and hydroxyethyl cellulose (HEC) and the embedded micromesh structure, the electrode displays superior photoelectric performance (5 Ω/sq at 83.5% transmittance) and robust mechanical stability (bending, twisting, folding, and peeling off). Furthermore, we assembled an electro- and thermo- dual responsive chromatic device, enabling rapid heat generation and multicolor switching. We believe that our work provides an innovative approach to fabricating high-performance electrodes for optoelectronic devices.

Electrochromic smart windows represent a promising technology for reducing building energy consumption through dynamic photo‐thermal regulation. However, scalable fabrication of high‐performance electrochromic films remains challenging. Herein, we pioneer slot‐die coating technique and aqueous inks for the high‐speed production (600 cm ² /min) of Wadsley‐Roth structure TiNb ₂ O ₇ films. Experimental and theoretical analyses reveal that the open crystallographic shear channels in TiNb ₂ O ₇ enable efficient ion transport with a low diffusion barrier of 0.22 eV, allowing it to achieve a high diffusion coefficient (6.34 × 10 ⁻¹⁰ cm ² /s), good uniformity, and 82.8% large optical modulation at 600 nm. We constructed a series of large‐scale electrochromic devices with a size up to 200 cm ² that demonstrate significant optical modulation (64.6%), rapid switching (23.4/12.4 s), and uniform coloration. We evaluated the photo‐thermal management performance of the device using a xenon lamp as a simulated solar source, achieving a notable temperature regulation of 18.8°C. To further validate its practical applicability, we conducted an outdoor test, demonstrating a temperature modulation of ∼5.0°C. Additionally, energy simulation analyses reveal that the device enables an energy saving of 155 MJ·m ⁻² . This work provides a scalable manufacturing strategy for high‐performance electrochromic devices, advancing the development of intelligent energy‐saving window technology.