Energy-Efficient Smart Window Based on Thermochromic Hydrogel with Ultrahigh Visible Transparency and Unprecedented Infrared Transmittance Modulation

Abstract Both high visible transparency and strong solar modulating ability are highly required for energy-saving smart windows, but conventional responsive materials usually have low transparency and narrow solar transmittance range. Herein, we report a significant advance toward the design and fabrication of responsive smart windows by trapping novel V0.8W0.2O2@SiO2 doped poly(N-isopropyl acrylamide) (PNIPAm) thermochromic liquid hydrogel within two glass panels. The smart window is highly transparent to allow solar transmittance at low temperatures, while turns opaque automatically to cut off solar energy gain when exposed in sunlight. With a remarkably low content (1.0wt‰) of dopant, V0.8W0.2O2@SiO2/PNIPAm (VSP) hydrogels exhibit ultrahigh luminous transmittance Tlum of 92.48% and solar modulation ∆Tsol of 77.20%. The superior performance is mainly attributed to that V0.8W0.2O2@SiO2 doping induces PNIPAm particles’ size reduction and internal structure change. W-doping decreases the phase transition temperature (Tc) of VO2 from 68 ºC to ~30 ºC (close to the Tc of PNIPAm), contributing to an unprecedented infrared transmittance modulation. Especially, the smart window shows excellent energy-saving during daytime outdoor demonstrations where practically achievable cooling temperature reaches up to 15.1 ºC. In addition, the smart window exhibits outstanding stability, as embodied by unchanged optical performance even after 100 transparency-opaqueness reversible cycles. This new type of thermochromic hydrogel offering unique advantages of shape-independence, scalability together with soundproof functionality promises potential applications in energy-saving buildings and greenhouses.

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Energy-Efficient Smart Window Based on Thermochromic Microgel with Ultrahigh Visible Transparency and Infrared Transmittance Modulation

Journal of Materials Chemistry A ◽

10.1039/d1ta03917b ◽

2021 ◽

Author(s):

Rong Zhang ◽

Bo Xiang ◽

Yuchun Shen ◽

Liru Xia ◽

Lei Xu ◽

...

Keyword(s):

Energy Saving ◽

Energy Efficient ◽

Smart Window ◽

Smart Windows ◽

Responsive Materials ◽

Infrared Transmittance

Both high visible transparency and strong solar modulating ability are highly required for energy-saving smart windows, but conventional responsive materials usually have low transparency and narrow solar transmittance range. Herein,...

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Thermochromic Hydrogels with Dynamic Solar Modulation and Regulatable Critical Response Temperature for Energy‐Saving Smart Windows

Advanced Functional Materials ◽

10.1002/adfm.202109597 ◽

2021 ◽

pp. 2109597

Author(s):

Gang Xu ◽

Huan Xia ◽

Pengyu Chen ◽

Wei She ◽

Hanning Zhang ◽

...

Keyword(s):

Energy Saving ◽

Solar Modulation ◽

Smart Windows ◽

Critical Response

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A Dual-Responsive Nanocomposite toward Climate-Adaptable Solar Modulation for Energy-Saving Smart Windows

ACS Applied Materials & Interfaces ◽

10.1021/acsami.6b15065 ◽

2017 ◽

Vol 9 (7) ◽

pp. 6054-6063 ◽

Cited By ~ 42

Author(s):

Heng Yeong Lee ◽

Yufeng Cai ◽

Shuguang Bi ◽

Yen Nan Liang ◽

Yujie Song ◽

...

Keyword(s):

Energy Saving ◽

Solar Modulation ◽

Smart Windows ◽

Dual Responsive

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Recent Advances in Fabrication of Flexible, Thermochromic Vanadium Dioxide Films for Smart Windows

Nanomaterials ◽

10.3390/nano11102674 ◽

2021 ◽

Vol 11 (10) ◽

pp. 2674

Author(s):

Jongbae Kim ◽

Taejong Paik

Keyword(s):

Thin Films ◽

Energy Saving ◽

Near Infrared ◽

Solar Spectrum ◽

Smart Windows ◽

Space Group ◽

Practical Applications ◽

Flexible Polymer ◽

Recent Advances ◽

Potential Applications

Monoclinic-phase VO2 (VO2(M)) has been extensively studied for use in energy-saving smart windows owing to its reversible insulator–metal transition property. At the critical temperature (Tc = 68 °C), the insulating VO2(M) (space group P21/c) is transformed into metallic rutile VO2 (VO2(R) space group P42/mnm). VO2(M) exhibits high transmittance in the near-infrared (NIR) wavelength; however, the NIR transmittance decreases significantly after phase transition into VO2(R) at a higher Tc, which obstructs the infrared radiation in the solar spectrum and aids in managing the indoor temperature without requiring an external power supply. Recently, the fabrication of flexible thermochromic VO2(M) thin films has also attracted considerable attention. These flexible films exhibit considerable potential for practical applications because they can be promptly applied to windows in existing buildings and easily integrated into curved surfaces, such as windshields and other automotive windows. Furthermore, flexible VO2(M) thin films fabricated on microscales are potentially applicable in optical actuators and switches. However, most of the existing fabrication methods of phase-pure VO2(M) thin films involve chamber-based deposition, which typically require a high-temperature deposition or calcination process. In this case, flexible polymer substrates cannot be used owing to the low-thermal-resistance condition in the process, which limits the utilization of flexible smart windows in several emerging applications. In this review, we focus on recent advances in the fabrication methods of flexible thermochromic VO2(M) thin films using vacuum deposition methods and solution-based processes and discuss the optical properties of these flexible VO2(M) thin films for potential applications in energy-saving smart windows and several other emerging technologies.

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Designable Phase Transition Temperature of VO2 Co-Doped with Nb and W Elements for Smart Window Application

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2019.16618 ◽

2019 ◽

Vol 19 (11) ◽

pp. 7185-7191

Author(s):

Hee Jung Kim ◽

Dong Kyu Roh ◽

Jung Whan Yoo ◽

Dae-Sung Kim

Keyword(s):

Phase Transition ◽

Transition Temperature ◽

Phase Transition Temperature ◽

Solar Modulation ◽

Smart Window ◽

Smart Windows ◽

Co Doping ◽

Window Applications ◽

Nb Dopant ◽

Co Doped

Monoclinic vanadium dioxide (VO2 (M)) particles co-doped with niobium and tungsten, with potential application in smart windows, were synthesized by hydrolysis and subsequent thermal decomposition of vanadyl sulfate. All the doped VO2 particles exhibited a monoclinic crystalline phase and the critical phase transition temperature (Tc) of VO2 (M) was adjusted by Nb and W co-doping. The Tc of Nb-doped VO2 (M) decreased at a rate of approximately 10 °C/at% Nb dopant, and the transition temperature could also be accurately controlled to room temperature (about 27 °C) by co-doping with Nb and W. A film prepared using co-doped VO2 (M) particles showed a solar modulation ability of ~18% and a luminous transmittance of 40%, indicating that the co-doped VO2 (M) particles represent suitable candidates for smart window applications.

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Gate-controlled VO2 phase transition for high-performance smart windows

Science Advances ◽

10.1126/sciadv.aav6815 ◽

2019 ◽

Vol 5 (3) ◽

pp. eaav6815 ◽

Cited By ~ 38

Author(s):

Shi Chen ◽

Zhaowu Wang ◽

Hui Ren ◽

Yuliang Chen ◽

Wensheng Yan ◽

...

Keyword(s):

Phase Transition ◽

Solar Energy ◽

Energy Saving ◽

High Performance ◽

Light Transmittance ◽

Energy Regulation ◽

Practical Application ◽

Theoretical Limit ◽

Smart Windows ◽

Infrared Transmittance

Vanadium dioxide (VO2) is a promising material for developing energy-saving “smart windows,” owing to its infrared thermochromism induced by metal-insulator transition (MIT). However, its practical application is greatly limited by its relatively high critical temperature (~68°C), low luminous transmittance (<60%), and poor solar energy regulation ability (<15%). Here, we developed a reversible and nonvolatile electric field control of the MIT of a monoclinic VO2 film. With a solid electrolyte layer assisting gating treatment, we modulated the insertion/extraction of hydrogen into/from the VO2 lattice at room temperature, causing tristate phase transitions that enable control of light transmittance. The dramatic increase in visible/infrared transmittance due to the phase transition from the metallic (lightly H-doped) to the insulating (heavily H-doped) phase results in an increased solar energy regulation ability up to 26.5%, while maintaining 70.8% visible luminous transmittance. These results break all previous records and exceed the theoretical limit for traditional VO2 smart windows, making them ready for energy-saving utilization.

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Tailoring Broad-Band-Absorbed Thermoplasmonic 1D Nanochains for Smart Windows with Adaptive Solar Modulation

ACS Applied Materials & Interfaces ◽

10.1021/acsami.0c21584 ◽

2021 ◽

Vol 13 (4) ◽

pp. 5634-5644

Author(s):

Min Guo ◽

Qiaoqi Yu ◽

Xingchi Wang ◽

Wanxuan Xu ◽

Yi Wei ◽

...

Keyword(s):

Broad Band ◽

Solar Modulation ◽

Smart Windows

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High-Efficiency Responsive Smart Windows Fabricated by Carbon Nanotubes Modified by Liquid Crystalline Polymers

Crystals ◽

10.3390/cryst11040440 ◽

2021 ◽

Vol 11 (4) ◽

pp. 440

Author(s):

Yuan Deng ◽

Shi-Qin Li ◽

Qian Yang ◽

Zhi-Wang Luo ◽

He-Lou Xie

Keyword(s):

Carbon Nanotubes ◽

Liquid Crystalline ◽

Near Infrared ◽

High Efficiency ◽

Polymer Brush ◽

Light Transmittance ◽

Smart Window ◽

Vertical Orientation ◽

Smart Windows ◽

Conversion Materials

Smart windows can dynamically and adaptively adjust the light transmittance in non-energy or low-energy ways to maintain a comfortable ambient temperature, which are conducive to efficient use of energy. This work proposes a liquid crystal (LC) smart window with highly efficient near-infrared (NIR) response using carbon nanotubes grafted by biphenyl LC polymer brush (CNT-PDB) as the orientation layer. The resultant CNT-PDB polymer brush can provide the vertical orientation of LC molecules to maintain the initial transparency. At the same time, the smart window shows a rapid response to NIR light, which can quickly adjust the light transmittance to prevent sunlight from entering the room. Different from common doping systems, this method avoids the problem of poor compatibility between the LC host and photothermal conversion materials, which is beneficial for improving the durability of the device.

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Full-frame and high-contrast smart windows from halide-exchanged perovskites

Nature Communications ◽

10.1038/s41467-021-23701-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

You Liu ◽

Jungan Wang ◽

Fangfang Wang ◽

Zhengchun Cheng ◽

Yinyu Fang ◽

...

Keyword(s):

Contrast Ratio ◽

High Contrast ◽

Smart Window ◽

Frame Size ◽

Smart Windows ◽

Ideal Solutions ◽

Ion Gel ◽

And Control ◽

Colour Rendering ◽

Perovskite Photovoltaic

AbstractWindow glazing plays an essential role to modulate indoor light and heat transmission, which is a prospect to save the energy cost in buildings. The latest photovoltachromic technology has been regarded as one of the most ideal solutions, however, to achieve full-frame size (100% active area) and high-contrast ratio (>30% variable in visible wavelength) for smart window applicability is still a challenge. Here we report a photovoltachromic device combining full-transparent perovskite photovoltaic and ion-gel based electrochromic components in a vertical tandem architecture without any intermediated electrode. Most importantly, by accurately adjusting the halide-exchanging period, this photovoltachromic module can realize a high pristine transmittance up to 76%. Moreover, it possesses excellent colour-rendering index to 96, wide contrast ratio (>30%) on average visible transmittance (400-780 nm), and a self-adaptable transmittance adjustment and control indoor brightness and temperature automatically depending on different solar irradiances.

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