
==== Front
Light Sci Appl
Light Sci Appl
Light, Science & Applications
2095-5545
2047-7538
Nature Publishing Group UK London

39294120
1560
10.1038/s41377-024-01560-9
Review Article
Phase-change VO2-based thermochromic smart windows
http://orcid.org/0000-0002-9400-8630
Jiang Cancheng 1
http://orcid.org/0009-0001-6253-1590
He Lanyue 1
Xuan Qingdong 2
http://orcid.org/0000-0003-2863-7698
Liao Yuan 1
http://orcid.org/0000-0001-9904-7914
Dai Jian-Guo 3
http://orcid.org/0000-0002-8963-0193
Lei Dangyuan dangylei@cityu.edu.hk

1
1 grid.35030.35 0000 0004 1792 6846 Department of Materials Science and Engineering, Centre for Functional Photonics, and Hong Kong Branch of National Precious Metals Material Engineering Research Centre, City University of Hong Kong, Kowloon, Hong Kong 999077 China
2 https://ror.org/02czkny70 grid.256896.6 0000 0001 0395 8562 Department of Refrigeration and Cryogenics Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009 China
3 grid.35030.35 0000 0004 1792 6846 Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077 China
18 9 2024
18 9 2024
2024
13 25514 11 2023
30 6 2024
31 7 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by/4.0/ Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Thermochromic coatings hold promise in reducing building energy consumption by dynamically regulating the heat gain of windows, which are often regarded as less energy-efficient components, across different seasons. Vanadium dioxide (VO2) stands out as a versatile thermochromic material for smart windows owing to its reversible metal-to-insulator transition (MIT) alongside correlated structural and optical properties. In this review, we delve into recent advancements in the phase-change VO2-based thermochromic coatings for smart windows, spanning from the macroscopic crystal level to the microscopic structural level (including elemental doping and micro/nano-engineering), as well as advances in controllable fabrication. It is notable that hybridizing functional elements/materials (e.g., W, Mo/SiO2, TiN) with VO2 in delicate structural designs (e.g., core-shell, optical cavity) brings new degrees of freedom for controlling the thermochromic properties, including the MIT temperature, luminous transmittance, solar-energy modulation ability and building-relevant multi-functionality. Additionally, we provide an overview of alternative chromogenic materials that could potentially complement or surpass the intrinsic limitations of VO2. By examining the landscape of emerging materials, we aim to broaden the scope of possibilities for smart window technologies. We also offer insights into the current challenges and prospects of VO2-based thermochromic smart windows, presenting a roadmap for advancing this field towards enhanced energy efficiency and sustainable building design. In summary, this review innovatively categorizes doping strategies and corresponding effects of VO2, underscores their crucial NIR-energy modulation ability for smart windows, pioneers a theoretical analysis of inverse core-shell structures, prioritizes practical engineering strategies for solar modulation in VO2 films, and summarizes complementary chromogenic materials, thus ultimately advancing VO2-based smart window technologies with a fresh perspective.

This review encapsulates the attributes of phase-change-VO2-based smart windows, highlighting their adaptive radiative cooling mechanisms, large modulation of both solar energy and thermal radiation, and methods for controlling phase-transition temperatures.

Subject terms

Nanoparticles
Photonic devices
https://doi.org/10.13039/501100002920 Research Grants Council, University Grants Committee (RGC, UGC) C5051-22GF Lei Dangyuan https://doi.org/10.13039/100007567 City University of Hong Kong (CityU) 9667246 Lei Dangyuan https://doi.org/10.13039/501100003452 Innovation and Technology Commission (ITF) MHP/162/22 Lei Dangyuan issue-copyright-statement© Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), CAS 2024
==== Body
pmcIntroduction

The escalating demand for energy consumption and the resultant emission of CO2 have been intensifying the global-warming problem, emphasizing the pressing imperative for energy conservation. Reports indicate that residential buildings are responsible for nearly 30% to 40% of the world’s primary energy consumption1. Hence, there is a significant imperative to enhance the energy efficiency of buildings. Among all building components, windows are frequently identified as less energy-efficient and requiring greater maintenance2, making smart windows an attractive research topic in optics, materials science, and building science. Windows play a crucial role in providing thermal, light, and acoustic comfort3, facilitating vision, air ventilation, photo-protection4, prevention of skin cancer5, and even influencing biopsychological effects6. The design of smart windows should take these aspects into consideration. Sunlight interacts with windows through transmission, reflection, or absorption, depending on their spectral properties in the ultraviolet (UV), visible, and near-infrared (NIR) regions. Consistently high transmittance in the visible spectrum is essential to meet lighting requirements. Indeed, a smart switch alternating between high and low transmittance in the UV and NIR spectral bands is desirable to minimize cooling loads during hot seasons and maximize heat gain during cold seasons. Thermochromic smart windows adjust radiation in invisible spectra according to surrounding temperatures, paving the way for highly efficient windows in the next generation of energy-conscious architectures.

Currently, commonly utilized thermochromic materials encompass vanadium dioxide, perovskite7, organic liquid crystal8, as well as mechano-thermo-chromic materials such as supersaturated salt hydrate crystal9. While supersaturated salt hydrates offer rapid and reversible phase transitions for smart window applications9, VO2 stands out for its sharp and abrupt change in transparency at a specific temperature, providing precise and consistent performance without the need for mechanical triggers or complex electro-thermal systems. VO2 is notable for the reversible temperature-dependent dielectric constants, exhibiting significant disparities between their metallic and insulating states. Rutile VO2(R) undergoes a reversible first-order MIT to monoclinic VO2(M) at a relatively moderate phase transition temperature (Tc, 68 °C). The structure and optical properties can mutate before and after Tc10–13, which makes VO2 an ideal thermochromic material for smart windows over the years.

Here, we provide an overview of phase-change VO2-based thermochromic coatings for smart windows, drawing on the latest research and structured according to the logic depicted in Fig. 1. Firstly, the spectral transmittance modulation resulting from the MIT of VO2 in crystalline structures is introduced, as illustrated in Fig. 1a. Further exploration is undertaken into the effects of the MIT on the thermodynamic, electrical, and optical properties of VO2, elucidated through band structures depicted in Fig. 1b. Secondly, elemental doping is introduced as Fig. 1c illustrates, considering the difference between the actual temperature and Tc. Thirdly, we discuss the micro/nano-engineering (Fig. 1d) in the categories including hybridization, core-shell micro/nanostructure, and multilayer films design, emphasizing on the structural effects for further improving the spectral modulation ability. Next, we review fabrication methods of VO2-based thermochromic films/coatings, with a specific focus on multi-functionalities, such as stability and emissivity, and the capability of controllable large-scale manufacturing, as depicted in Figs. 1e-1f. Additionally, we briefly introduce and discuss other promising chromogenic materials that can potentially be integrated with VO2 for smart windows to overcome their intrinsic limitations. Finally, outlooks and perspectives are addressed regarding current challenges and further advancements of VO2-based thermochromic smart windows.Fig. 1 Overview of the VO2-based thermochromic coatings for smart windows.

a Typical optical properties of VO2 thin films in visible and NIR regions and corresponding crystal structures: the monoclinic (M) insulating phase at low temperature and rutile (R) metallic phase at high temperature168. b Simplified band structures of VO2(M) and VO2(R) described by molecular orbital diagrams169. c The effect of elemental doping on the thermochromism of VO229,40,170. d Micro/nano-engineering towards performance enhancement of VO2-based thermochromic coatings48,70,171. e Multifunctional VO2-based micro/nano-structures with stability54, emissivity71, etc. f Controllable fabrication methods of VO2-based thermochromic films/coatings172. Figures reproduced with permission from: (b), Whittaker et al.169, American Chemical Society

This review distinguishes itself from previous works through the following unique contributions:We provide a comprehensive categorization of VO2 doping strategies, shedding light on the doping mechanism, and emphasizing the crucial NIR-energy modulation capability (ΔTNIR) for smart window applications.

We pioneer a theoretical analysis of inverse core-shell structures featuring VO2 as the shell material, delving into their potential for enhancing solar modulation and offering novel insights for future research.

We prioritize practical engineering strategies to boost the solar-energy modulation capabilities of VO2 films, moving beyond mere descriptions of various VO2 nanostructures.

We offer a comprehensive summary of other chromogenic materials that can complement VO2 to enhance smart window functionality, providing a broader perspective than previous studies.

These elements inject a fresh perspective into VO2-based smart window technologies and are critical for further advancing the field.

Temperature-triggered phase change for solar modulation

The MIT in VO2 is thermally induced, with concomitant alterations in the entropy and heat capacity of the material. In 1971, Dr. John B. Goodenough delineated molecular orbital diagrams grounded in crystal-field theory, as depicted in Fig. 1b14. Simply, there is a π bond and a π* anti-bond between the V4+ and O2- orbitals in VO2(R). Meanwhile, a d// nonbond is formed between nearby V4+ orbitals along the crystallographic c axis, which partially overlaps with the unfilled π* band. Metallic characteristics arise from the overlap between π* and d// bonds, at which the Fermi level falls, leading to the VO2(R) with high electron mobility. As the temperature decreases, lattice distortion enhances the π overlap between the V4+ and O2- orbitals, elevating the energy level of the π* anti-bond. Concurrently, the interaction between V-V pairs induces the splitting of the d// bonds into d//-bonding and anti-bonding components, resulting in a band gap of ~0.7 eV between the π* and d//-bonding levels.

The presence of a band gap, resulting from the split between the π* and d//-bonding levels, gives rise to insulating properties in VO2(M). This band gap acts as a barrier to electron mobility, thereby leading to the manifestation of insulating behavior. While there may be variations between this theoretical proposal and experimental observations, it nonetheless offers valuable insights into the fundamental nature of the MIT in VO2. The fluctuation in electron mobility during the MIT enables switchable electrical conductivity, a characteristic that finds application in diverse fields such as tunable polarization converters15,16. In metallic VO2(R), the dielectric constant is considerably lower compared to insulating VO2(M). This discrepancy arises primarily because the presence of free electrons in VO2(R) allows them to screen the electric field effectively, diminishing the polarization of its lattice structure induced by external electric fields. As a result, the dielectric constant in metallic VO2(R) is notably reduced in comparison to its insulating counterpart. As depicted in Fig. 1a, VO2 exhibits a monoclinic structure characterized by high transparency to visible and near-infrared (NIR) light below its phase transition temperature (Tc). Conversely, upon transitioning to the rutile structure (R) above Tc, the material maintains nearly consistent visible light transmittance but experiences a significant reduction in NIR transmittance17–20. To evaluate the optical performance of a VO2-based thermochromic smart window, the luminous transmittance (Tlum, 380–780 nm), the solar-energy modulation ability (ΔTsol, 300–2500 nm) and the NIR-energy modulation ability (ΔTNIR, 780–2500 nm) are calculated as follow:1 Tlum/sol/NIR=∫Φlum/sol/NIR(λ)T(λ)dλ∫Φlum/sol/NIR(λ)dλ

2 ΔTsol=Tsol,c−Tsol,h

3 ΔTNIR=TNIR,c−TNIR,h

where Φlum(λ) is the standard luminous efficiency function of human photosensitive vision21–23, Φsol/NIR(λ) is the solar/NIR irradiance spectrum at air mass 1.5 (corresponding to the sun standing 37° above the horizon)24, T(λ) and Tlum/sol/NIR denote the spectral transmittance at wavelength λ and luminous/solar/NIR transmittance, respectively. The subscripts lum/sol/NIR and c/h represent the wavelength range (visible/whole solar spectrum/NIR) for integration and thermal states (low temperature/high temperature), respectively.

It’s noteworthy that Tlum differs from visible solar transmittance (Tvis)25, which considers the relative spectral distribution of illuminant D6526. For VO2-based smart windows, ΔTNIR is approximately double ΔTsol, as noticeable spectral transmittance changes occur in NIR bands (~52% of total solar irradiance) before and after MIT. Both high Tlum and ΔTsol/NIR are crucial: the former signifies better lighting savings, while the latter determines the energy-saving performance of VO2-based smart windows. However, constrained by the intrinsic MIT, VO2-based smart windows face obstacles such as high transition temperature (68 °C), low luminous transmittance (Tlum < 60%), and weak solar-energy modulation (ΔTsol < 15%). Extensive efforts have been dedicated to addressing these challenges and advancing VO2-based smart windows for practical applications.

Elemental doping for tailoring the phase-transition temperature

As mentioned above, the primary challenge faced by VO2-based smart windows in practical applications is the significantly higher MIT compared to the normal operating temperature of conventional windows. To address this issue, researchers commonly employ elemental doping as the primary strategy to modulate Tc and optical properties of VO2. The effects of some doping elements are summarized in Table 1.Table 1 Elemental doping effects on the thermochromic performance of VO2-based films

Doping strategies (chemical formula)	Dopant(s)	Doping level (at%)	Tlum (%)	ΔTsol (%)	ΔTNIR (%)	dTc/dx (°C/at%)	Tc (K)	Ref.	
Carrier concentration increase	Interstitial site (VAxO2)	H	3	-	-	-	−38	227	29,30	
Li	3	-	-	-	−43	212	31,32	
Na	3	-	-	-	−49	293.15	31,33	
B	6	54.3	12.5	27.8	−63.3	301.25	34,35	
Substitutional site (V1-xAxO2/V1-x-yAxByO2)	W	2	50.7	8	18.2	−20	301	36,37	
Mo	3	34.5	1.1	2.5	−9.33	313.01	132,133	
Nb	2.5	38.8	2.6	6.6	−8.4	320	134,135	
Sr + W	11.9 + 0.9	61.8	5.2	10	-	-	136,137	
Zr + W	4.2 + 2.1	60.7	10.6	22.7	−21.1	-	138,139	
Mo + W	7 + 8	55	-	-	−6.47 to 6.7	-	140,141	
Sn + W	1.9 + 1.6	41.1	13.4	25.7	-	-	142,143	
Structural distortion (VAxO2/V1-xAxO2)	Sb	7	-	-	-	−11.7	259.1	40,144	
Be	3	-	-	-	−58	-	41,145	
Cr	3	22.4	7.4	19.1	0.69	343.07	146,147	
Ru	2.32	-	-	-	−10.5	316.64	148,149	
“-” means data unavailable

The fundamental role of dopants is to lower the energy barrier, thereby reducing the MIT temperature, as the electronic phase transition in VO2 nearly coincides with the structural phase transition27,28. Correspondingly, the selection of the elemental doping is commonly based on two key factors: (1) Increasing the carrier concentration to accelerate the electronic phase transition: Dopants are selected to either donate additional electrons (n-type doping) or create spaces for electrons through the formation of vacancies (p-type doping). This tactic increases the mobile charge carrier density within the VO2 lattice, thereby amplifying the likelihood of electronic excitations that can precipitate the phase transition. By bolstering the number of available charge carriers, the dopants accelerate the electronic phase transition. This acceleration is due to the heightened probability of electronic interactions that can drive the system across the phase boundary, effectively diminishing the energy threshold for the MIT; (2) Introducing distortion into the atomic structure to assist the structural phase transition: The second prong of the doping strategy involves the deliberate introduction of atomic-scale distortions. These distortions arise from the mismatch between the dopants and the host VO2 lattice in terms of size or valence, leading to localized strain. Such strain can perturb the equilibrium of interatomic forces within the crystal, thus lowering the energy required for the structural reconfiguration that accompanies the MIT. The dopants act as a catalyst for structural changes by stabilizing the high-temperature metallic phase, which is characterized by a distinct arrangement of V-V dimers. This stabilization aids in the rapid reorganization of the vanadium and oxygen atoms, facilitating the transition from the insulating to the metallic state.

Regarding the increase in carrier concentration, researchers have pursued two primary doping strategies: a) insert smaller-sized doping atoms (Fig. 1c, left) such as H29,30, Li31,32, Na31,33, and B34,35 into the interstitial sites of VO2; b) substitute the V sites with high-valance elements (Fig. 1c, mid) such as W36,37, Mo38, Nb39. These strategies aim to enhance the concentration of mobile charge carriers within VO2 crystals, thus lowering Tc. For instance, when smaller dopant atoms are inserted into the interstitial sites of VO2 lattice, they introduce additional electrons, thereby increasing the carrier concentration within VO2 crystals. Similarly, by substituting vanadium sites with high-valence elements, these elements can inject partial electrons into the valence band of VO2. For example, by substituting vanadium atoms in VO2, tungsten atoms can inject electrons into the valence band of VO2, effectively lowering Tc, typically by 20–26 K/at%.

On the other hand, to address structural distortion, researchers have also employed methods such as adjusting the V-V distances in VO2 or modifying lattice parameters by a dopant (Sb40, Be41, etc.). Through these measures, researchers can effectively modulate the crystal structure of VO2, thereby affecting its transition temperature Tc. For example, by adjusting the distances between vanadium atoms in VO2 crystals or by modifying lattice parameters, the structure of VO2 crystals can be altered to facilitate phase transition. These adjustments and distortions in structure can effectively reduce the transition temperature Tc of VO2, making it more suitable for applications such as smart windows.

In conclusion, elemental doping serves as an effective method for modulating the critical transition temperature of VO2-based smart windows, with selection based on precise control of carrier concentration and structural distortion. This strategy provides crucial technical support for enhancing the performance and applicability of VO2-based smart windows in practical applications. In future research, a deeper understanding of the doping mechanism and various influencing factors in the doping process will be essential.

While doping strategies have been successful in modulating the transition temperature (Tc), the environmental stability and long-term performance impact of doped elements must be considered. Greater emphasis should be placed on the selection of dopants and the optimization of doping levels in future research to ensure more stable and efficient thermochromic smart windows.

Micro/nano-engineering for Improving the solar-energy modulation ability

In addition to lowering Tc, elevating Tlum and ΔTsol is also important for smart window applications42. Micro/nano-engineering strategies through either micro- or macro-structural/materials modification have been proposed and investigated widely43. According to the modification principles, the reported micro/nano-engineering strategies can be classified into three categories: 1) hybridization that incorporates other materials/structures with individual VO2 materials, 2) core-shell micro/nano-structures that modulate the Mie/plasmonic resonant responses of spherical VO2 nanoparticles (NPs) as either core or shell, and 3) multilayer films that integrate other flat layers for enhanced optical resonances as well as multifunctionality.

VO2-based hybridized thin films

In efforts to improve the thermochromic properties of VO2-based thin films, researchers often encounter a trade-off between ΔTsol and Tlum when using thick layers of continuous VO2 film. To address this challenge, hybridization with other inorganic and/or organic materials has emerged as a viable strategy to optimize both Tlum and ΔTsol simultaneously. This hybridization approach may affect the MIT and hysteresis-loop width of VO2 by inducing strains, while also modulating optical constants such as Tlum and color44. Furthermore, the introduction of functional materials like TiO245 and ZrO246 can add multifunctionality to the composite films, offering benefits such as self-cleaning and mechanical reinforcement. Researchers have explored various strategies to improve the optical performance of VO2-based thin films. Li et al. theoretically investigated the optical performance of VO2 NPs matrix composites and yielded much higher Tlum and ΔTsol than pure VO2 thin films by calculations based on effective medium theory47. Liang et al. further introduced SiO2 microparticles in the W-doped VO2/PVP composites for Tlum improvement. The single layer of randomly dispersed SiO2 microspheres in the film provided optical pathways for sunlight, which offset the decrease of Tlum caused by the strong absorption of visible light by high volume concentration of W-VO2 NPs (Fig. 2a). Experimental results revealed that W-doped VO2/SiO2/PVP composite films enable high Tlum of 65% without sacrificing too much ΔTsol (12.6%)48, which also proved the validity of the structure in the previous study by Li et al.47. Hao et al. proposed an alternative strategy that utilize plasmonic response to balance Tlum and ΔTsol. A plasmonic array of TiN NPs was fabricated underneath the VO2 thin film as Fig. 2b exhibits and endowed ΔTsol of 10.8% and Tlum of 51%, respectively49. TiN NPs can efficiently absorb NIR radiation to provide local heating and accelerate the MIT in VO2. Additionally, the VO2 film can also be patterned for performance improvement. Cao et al. synthesized periodical and spherical cavity-structured VO2/SiO2 composite films through a polystyrene template and annealing process as illustrated in Fig. 2c. Under the photonics crystal structure of the patterned VO2 composite film, balanced thermochromic properties can be obtained as ΔTsol of 8.4% and Tlum of 55.6%50. Inorganic VO2 could also be integrated with organic materials to enhance the thermochromic properties. For instance, He et al. presented a dynamically regulated system based on W-VO2/PAM-PNIPAM hydrogel films, which was developed into smart windows (ΔTsol 46.3% and Tlum 72%)51. As illustrated in Fig. 2d, the PVP-modified monoclinic W-VO2 was dispersed in the PNIPAM microgel, where the PAM hydrogel with high Tlum serves as a skeleton, holding and keeping water molecules, PNIPAM microgel and surface-modified W-VO2 inside. Upon heating, the intramolecular and intermolecular hydrophobicity of PNIPAM is enhanced, leading to the discharge of water molecules from the chemical framework of PNIPAM and generating phase separation interfaces. These interfaces can strongly scatter the incident solar irradiance when the W-VO2 undergoes the MIT and hence dramatically enhance the NIR light reflectivity simultaneously.Fig. 2 Thermochromic performance of VO2-based hybridized thin films.

a Schematic diagrams of a W-VO2/SiO2/PVP composite film48. b Temperature-dependent optical properties of a VO2/TiN composite film49. c Schematics of fabrication process of a micro-structured VO2/SiO2 ordered composite film50. d Schematics of temperature-controlled structural changes of a W-VO2/PAM-PNIPAM hydrogel film51

VO2-based core-shell micro/nano-structures

In addition to hybridization methods, core-shell approaches have emerged as an efficacious strategy for enhancing the thermochromic properties and functionalities of VO2-based films52. These core-shell nanostructures can be broadly categorized into bilayer and trilayer configurations based on the number of layers, wherein VO2 is encapsulated within dielectric shells such as SiO2, TiO2, SnO2, ZnO, Al2O353, or metallic shells like Au and Ag. For instance, Pi et al. prepared thermochromic and hydrophobic core-shell VO2@SiO2 (VSQ) NPs with tetraethoxysilane (TEOS) and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP) as depicted in Fig. 3a54. The ΔTsol reaches up to 15.4% while the Tlum remains as high as 51.5% owing to localized surface plasmon resonance (LSPR)55. Furthermore, the SiO2 shell efficiently shields VO2 from oxidation, enhancing its durability, while DMOAP modification imparts additional functionalities including anti-agglomeration, surface hydrophobicity, and self-cleaning, as illustrated in Fig. 3b54. Lu et al. synthesized VO2@SiO2@Au trilayer core-shell nanoparticles to harness LSPR and enhance optical tunability, as depicted in Fig. 3c56. By modulating the material composition and particle sizes of the outer metallic shell, the resonance peak could be tuned across a wide spectral range, offering customizable colorful appearances for the films, as shown in Fig. 3d. Since VO2 can transition between dielectric and metallic states, it can be employed as either the inner or outer layer of core-shell structures. Yao et al. fabricated SiO2@TiO2@VO2 inverted trilayer core-shell NPs via controlled interfacial engineering, as depicted in Fig. 3e. The Tlum of the resultant coating reached a remarkable 74%. Additionally, as Fig. 3f illustrates, since TiO2 was partially exposed rather than completely covered by VO2, the coating facilitated the integration of thermochromism from the outer VO2 layer, photocatalytic self-cleaning capability from the middle TiO2 layer, and antireflective properties from the internal SiO2 hollow nanospheres57.Fig. 3 Thermochromic performance of VO2-based core-shell micro/nanostructures.

a Synthesis procedures of VSQ core-shell NPs54. b Low water adhesion and self-cleaning performance of a VSQ-coated surface54. c Synthesis procedures of VO2@SiO2@Au trilayer core-shell NPs56. d Different colors of VO2-based trilayer core-shell NPs-based films. From left to right: a VO2@SiO2@Ag NPs-based film (V), a plain VO2 film (I), VO2@SiO2@Au films grew in different content of HAuCl4 (II-IV)56. e Synthesis procedures of SiO2@TiO2@VO2 inverted trilayer core-shell NPs57. f SEM micrographs of (f1) a SiO2 hollow nanosphere-based coating, (f2) a SiO2@TiO2 coating, and (f3) a SiO2@TiO2@VO2 coating, respectively57

The spectral transmittances of typical bilayer and trilayer VO2-based core-shell structures are shown in Fig. 4a, b, demonstrating a notable enhancement in Tlum. Additionally, Fig. 4c, d illustrates the durability and coloration of these core-shell configurations, providing detailed insights into their multifunctional capabilities. Specifically, Fig. 4c showcases the VSQ coating’s ability to enhance the stability and longevity of VO2 by providing a protective SiO2 shell, preventing oxidation, incorporating hydrophobic modification for self-cleaning, and maintaining structural integrity through robust adhesion. This innovative approach collectively improves environmental and mechanical durability, addressing crucial challenges faced by VO2-based thermochromic coatings55. Moreover, in Fig. 4d, the tunable SPR properties of Au nanoparticles are highlighted, demonstrating their potential to modify the color of solutions and, by extension, the color of VO2-based thermochromic smart films57. Lu et al.‘s work illustrates how controlling the size of the Au nanoparticles enables the tailoring of film color from brick red to purple and blue. This advancement represents a significant stride in the development of smart window technologies, offering versatile solutions for enhancing the aesthetic appeal and functionality of VO2-based coatings. The thermochromic behavior of VO2-based core-shell structures is intricately linked to the properties of the core/shell materials and their respective sizes, which govern the dielectric environment surrounding VO254. To systematically investigate the optical performance of the thermochromic films, Xie et al. performed theoretical calculations based on the effective medium theory coupled with the transfer matrix method. Their findings, showcased in Fig. 4e–f, suggest that for films composed of VO2 core-shell nanoparticles, selecting a low absorption shell material (e.g., ZnO or Cr2O3) with a refractive index (RI) ranging from 1.6 to 2.3, and maintaining a relative shell thickness between 0.1 and 0.3, is crucial for preserving a high sol-gel transition temperature difference (ΔTsol)53. Here, the relative shell thickness (α) is defined as the ratio of the shell thickness to the core radius (α = tshell /Rcore). In Fig. 4e, dashed lines represent the solar modulation capability of VO2 nanoparticle, while solid orange lines represent VO2@shell structures with varying shell materials. Analysis indicates that VO2-based core-shell structures outperform VO2 nanoparticles when the shell refractive index falls within 1.6 to 2.3, yielding performance enhancement. Similarly, in Fig. 4f, for VO2@ZnO or VO2@Cr2O3 structures, superior performance of VO2-based core-shell structures is observed with shell thickness between 0.1 and 0.3, demonstrating performance improvement. Table 2 has been included, detailing the distinct performance and characteristics of VO2-based core-shell micro/nanostructures with various dielectric and metallic shell materials.Fig. 4 Optical and thermal performance of VO2-based films and coatings.

a–c Transmittance spectra of a VO2 and VO2@ZnO films at 20 and 80 °C173, b VO2 and SiO2@TiO2@VO2 coatings at 20 and 100 °C57, and c VSQ coatings treated at 60 °C and 90% RH for different periods54. d Absorption spectra of different solutions56. e, f ΔTsol of VO2 core-shell NPs-based films, as a function of e shell refractive index and f relative shell thickness53. g, h ΔTsol of VO2 inverted core-shell NPs-based films, as a function of g core refractive index and h relative shell thickness, the performance of the plain VO2 film was shown by the dashed lines. Figures reproduced with permission from: a, Chen et al.58, American Chemical Society

Table 2 Performance comparison of different VO2 core-shell structures

No.	Core Material	Shell Material	Tlum (%)	ΔTsol (%)	Characteristics/Performance	Ref.	
1	VO2	SiO2	51.5	15.4	High weatherability, high ΔTsol and Tlum	55	
2	VO2	SiO2@ Au	-	7.52	Trilayer core-shell structure, high optical tunability	57	
3	SiO2	Au@ VO2	74	12	Inverted trilayer core-shell structure, high thermochromism benefiting from partially exposed TiO2	58	
4	VO2	ZnO	-	-	Low absorption shell material, high ΔTsol	54	
5	VO2	Cr2O3	-	-	Low absorption shell material, high ΔTsol	54	
6	VO2	SiO2	51.5	15.4	Metallic shell, high LSPR effect	56	
7	VO2	Ag	-	-	Metallic shell, high LSPR effect	56	
“-” means data unavailable

However, the scarcity of investigations into the optical characteristics of inverted core-shell structures, where VO2 serves as the shell material, underscores a critical gap in our current understanding. To address this gap, we conducted theoretical analyses utilizing the Mie theory coupled with the Monte Carlo method. Our research specifically targeted inverted VO2 core-shell nanoparticles incorporating core materials such as SiO2, ZnO, Cr2O3, and TiO2.

Upon scrutinizing Fig. 4e, g, a notable trend emerged: the inverted structures consistently displayed superior solar modulation capability across all material combinations compared to their conventional counterparts. Furthermore, it was observed that the ΔTsol of these films could be further enhanced by integrating low-absorption core materials, like SiO2, characterized by a low refractive index and a relative shell thickness exceeding 1.1, as shown in Fig. 4g, h. These results reveal that the inversion of the core-shell structure leads to enhancements in Mie scattering effects, suggesting that inverted structures hold greater potential for solar modulation capabilities compared to ordinary structures.

Multilayer films design with photonic cavity

In general, there are mainly two forms of thermochromic coatings based on VO2: flexible foils and multilayered films. Flexible foils involve dispersing VO2-based nanoparticles in a polymer host matrix such as PU, PVP, and PMMA, and then combining them with a flexible substrate. On the other hand, multilayered films are typically fabricated on glass using direct deposition methods such as physical vapor deposition (PVD) and chemical vapor deposition (CVD). Since the absorption of VO2 is mainly in the 250–700 nm wavelength range, the Tlum of single-layer VO2 films is generally restricted. Additionally, due to its transmittance switches primarily in the NIR region, which accounts for about 43% of solar energy in the solar spectrum, leading to limited solar modulation (ΔTsol), often remaining below 10%. Multilayer films design is an effective solution towards this perplexity. To address these limitations, multilayer film designs have emerged as effective solutions. These films not only allow for the design of solar transmittance but also enable the tailoring of NIR emissivity58. Moreover, the integration of different layers makes it easier to achieve multifunctionality compared to single-layer films.

Antireflection (AR) is a noteworthy function that has been demonstrated as a viable method to enhance the low luminous transmittance (Tlum) of VO2-based films without compromising their thermochromic properties. Additionally, neat VO2 is prone to oxidation to V2O5 in air and exhibits poor acid resistance, leading to environmental instability that limits its practical application as a thermochromic coating in smart windows59. Incorporating VO2 films with other layers can introduce practical functions such as antioxidizability60, hydrophobicity61, and photocatalysis62. For instance, Zheng et al. designed a TiO2/VO2/TiO2 multilayer film (with ΔTsol of 10.2% and Tlum of 30.1%), which exhibited at least three functions: antifogging/self-cleaning, thermochromic, and antireflective properties. These properties were respectively attributed to the top TiO2(A), the middle VO2(M), and the bottom TiO2(R) layers, as illustrated in Fig. 5a63. However, as for the antireflection coatings (ARCs), most researchers focused on increasing luminous transmittance (Tlum) at the expense of sacrificing solar modulation (ΔTsol). This trade-off is a significant challenge as ΔTsol is a determinant factor for energy-saving applications and can hinder the translation of these technologies from the laboratory to the market. To address this challenge, variable ARC/VO2 multilayer film designs, as illustrated in Fig. 5b and c, have emerged. For example, Liu et al. utilized a novel RI-tunable (1.47–1.92 at λ = 550 nm) nano sol-gel-based ARC/VO2 bilayer (Fig. 4b) with a ΔTsol of 18.9% and Tlum of 44% to enhance the antireflective effect at lower temperatures. This approach aims to maximize ΔTsol for various VO2 nanosubstrates64. Xu et al. fabricated a VO2/Movable ARC bilayer controlled by dual modes using magnetron sputtering, as illustrated in Fig. 5c. This approach significantly improved the thermochromic properties, with a ΔTsol of 18.2% and Tlum of 42.5%. Moreover, it enabled the two-phase smart regulation of eco-friendly H2O through the conversion of liquid and gaseous states. This bilayer system can passively modulate according to the variation in temperature difference between indoor and outdoor environments. Additionally, it can actively control the amount of solvent by detecting the temperature difference and humidity between the insulating glass, thereby adjusting the thickness of the ARC65.Fig. 5 Multilayer design to enhance the thermochromism and multifunctionality of VO2-based thin films.

a Schematic diagrams of a TiO2/VO2/TiO2 double-layer AR design63. b A RI-tunable ARC/VO2 bilayer64. c A VO2/movable ARC bilayer sandwiched between two quartz glass65. d A multilayer system as a RCRT window70. e Estimated energy-saving map of multilayer VO2-based thermochromic smart window. f A tunable Fabry-Pérot cavity based TARC design71. g A VO2-PDMS-driven radiative cooling coating77. Figures reproduced with permission from: (c), Xu et al.66, American Chemical Society

Thermal emissivity (εT) holds equal importance alongside ΔTsol and Tlum for VO2-based smart windows. It has been leveraged in numerous thermal management and energy-saving applications66–69 and has recently garnered attention in the context of smart windows, particularly in combination with the concept of radiative cooling70–72. Radiative cooling harnesses the infrared atmospheric transparent window to dissipate heat and effectively cools terrestrial objects through thermal radiation73–75.

In comparison to traditional smart windows, which primarily focus on modulating incoming solar energy, high thermal emissivity (εT) for radiative cooling offers an additional channel for dissipating excessive thermal energy generated by solar heating. According to Kirchhoff’s thermal law, the absorptivity of an object is equal to its emissivity in thermal equilibrium conditions. And the transmittance of glasses can be ignored when the wavelength is longer than 4.5 μm. Commonly, εT is calculated by weighting the film reflectance with the black-body emission spectrum from 4.5 to 25 µm as follow:4 εT=∑4.525GTλEλΔλ≈1−∑4.525GTλRλΔλ

where GT(λ) is the normalized relative spectral distribution of black-body radiation at temperature T (T is chosen to be 20 °C according to CNS GB/T 1895.2–2002). E(λ) refers to the spectral emittance, i.e., the fraction of the black-body radiation. R(λ) refers to the reflectance in the region (4.5-25 µm).

A high value of εT indicates an intensive energy exchange between the window surface and its ambience through thermal radiation and absorption76. Wang et al. developed a passive radiative cooling regulating thermochromic (RCRT) smart window (ΔTsol 17% and Tlum 32.2%) with tunable long-wave infrared (LWIR) emissivity (εLWIR) based on a W-doped VO2-PMMA/spacer/low-E stack using spin coating, as illustrated in Fig. 5d. This configuration formed a Fabry-Pérot resonator, enabling the promotion of radiative cooling during warm weather (high εLWIR) or suppress it during cold weather (low εLWIR)70.

To further elucidate the energy-saving benefits of VO2-based smart windows, we calculated the annual total energy savings for model buildings equipped with multilayer VO2-based smart windows (ΔTsol = 10%, Δε = 0.5). Figure 5e illustrates the total energy saved annually in various cities across China. From the energy-saving map, it is evident that cities in southern regions exhibit more pronounced energy-saving effects compared to those in northern regions, primarily due to the hotter climate. For instance, the average annual energy savings in Hong Kong amount to 80.16 kWh/m2, whereas in Jilin, it is only 45.12 kWh/m2. This analysis underscores that the installation of VO2-based smart windows in buildings leads to reduced energy consumption, yielding significant energy-saving benefits.

It is worth noting that achieving dynamic modulation of emissivity can be challenging when incorporating low-E coatings (such as ITO) due to their strong NIR blocking properties, which can lead to relatively low values of ΔTsol. The simultaneous modulation of the spectral performance in both the NIR and long-wave infrared (LWIR) regions remains a question to be addressed in future research.

Additionally, Tang et al. introduced a WxV1-xO2-based temperature-adaptive radiative coating (TARC), as shown in Fig. 5e, to achieve strong sky-window radiative cooling at high temperatures and solar heating or warm-keeping at low temperatures. This was made possible by amplified radiative absorption facilitated by the designed Fabry-Pérot resonance with adjacent WxV1-xO2 blocks, as well as the bottom Ag layer within the ¼-wavelength cavity71. Furthermore, Liu et al. presented a VO2-PDMS-driven intelligent radiative cooling coating with both automatic cooling switching and continuous adjustment of thermal comfort, as illustrated in Fig. 5f77. The polydimethylsiloxane (PDMS) substrate could be stretched to modulate the radiative cooling power according to our desired cooling temperature. Adjusting the VO2-PDMS coatings through stretching modifies the filling ratio, consequently influencing the dielectric characteristics of the stacked nano-grating structure. This alteration impacts surface waves at the interfaces, resulting in modifications to the spectral performance of the coatings.

Micro/nano-engineering, offering new degrees of freedom in the design and manufacturing of VO2-based thermochromic materials, also presents challenges regarding manufacturing complexity and cost control. It is suggested that future efforts should be directed towards streamlining the manufacturing process and reducing costs, without compromising or enhancing material performance.

To develop high-performance and cost-effective VO2-based smart windows, researchers must gain a deep understanding and precise control of the doping mechanisms, utilize micro/nano-engineering techniques to optimize optical properties, and balance Tc with optical characteristics. By employing precise doping strategies and micro/nano-engineering techniques, Tlum and ΔTsol can be optimized. Additionally, simplifying the manufacturing process to reduce costs is essential to ensure the product’s performance and economic viability in practical applications.

Methods

Preparation of VO2 nanoparticles

High-quality VO2 NPs with narrow distribution and uniform morphology are undoubtedly conducive to fabricate ideal thermochromic films. Recently, several methods have been reported to prepare definitive VO2 particles, as shown in Table 3. For instance, solid-phase reaction methods offer low-cost and large-scale production but may involve toxic reactants and impurities, while gas-phase reaction methods provide morphological control but are often constrained by conditional reactions and equipment complexity.Table 3 Summary of the preparation methods of VO2 particles

Reaction environment	Method	Pros	Cons	Particle size	Particle shape	Ref.	
Solid phase reaction	Thermal reduction	Low-cost, large-scale	Toxicity of reactant, conditional reaction, impurities	Micro	Rhombohedral	150,151	
Pyrolysis	Mild reaction, controllable composition, less impurities	CO2 emission, large particle size	Nano	Rod	152,153	
Ball-milling	Large-scale, modifiable	Introducing impurities	Nano	Irregular	154,155	
Gas phase reaction	Physical vapor deposition	Morphological control	Conditional reaction	Micro/nano	Rod	156,157	
Chemical vapor deposition	High crystallinity, uniform	Small-scale, substrate-dependent	Nano	Wire	158,159	
Liquid phase reaction	Sol-gel method	Low-cost, facile	Shrinkage upon drying	Nano	Spherical	160,161	
Hydrothermal method	Low-cost, high crystallinity	Conditional reaction	Nano	Snowflake	162,163	
Seeded growth	Controllable crystal growth	Pressure requirement	Nano	Star	164,165	
Solution combustion	Low-cost, time-saving, controllable composition	Small-scale, uneven grainsize	Micro/nano	Irregular	166,167	

CVD and PVD methods are typically constrained by expensive and intricate equipment, often resulting in low yield. The hydrothermal method usually necessitates precise control over temperature and atmosphere, while ball-milling and thermal reduction methods are prone to introducing impurities. In contrast, the pyrolysis process offers advantages such as mild reaction conditions, controllable product composition, and minimal impurity introduction, making it conducive to large-scale production. Recent advancements, such as the combination of solvent-thermal and pyrolysis processes, have led to the synthesis of purer VO2 powder with high crystallinity. Hua et al. employed a combination of solvent-thermal and pyrolysis processes to synthesize purer VO2 powder under mild air conditions. Through manual grinding and etching processes, they obtained innovative VO2(M) nanoparticles with high crystallinity55. The equations for the aforementioned processes are as follows:5 NH4VO3+C2H6O2→N2+VO(OCH2CH2O)

6 VOOCH2CH2O+O2→VO2+H2O+CO2

The preparation of VO2 nanoparticles is a critical step in the development of VO2-based thermochromic smart windows. While various methods have been explored, each with its own set of advantages and limitations, the pyrolysis process stands out for its mild reaction conditions and minimal impurity introduction, which are particularly beneficial for large-scale production.

Fabrication of VO2-based thermochromic films

Thus far, a multitude of methods have been devised to produce high-quality VO2 films with outstanding thermochromic properties78–80. These methods can be broadly categorized into chemical and physical techniques. Among them, CVD stands out as a commonly employed fabrication method for VO2 thin films, owing to its merits of high deposition rate, uniform structure, excellent adhesion, and scalability. In the CVD process, a precursor containing metal ions is dissolved in a solvent and then transported by an inert carrier gas to the deposition reactor, where the chemical reaction occurs, as illustrated in Fig. 6a. For instance, electric-field assisted chemical vapor deposition (EACVD)78 and low temperature chemical vapor deposition (LTCVD)80 have been developed to enhance thermochromic properties and facilitate low-cost production.Fig. 6 Fabrication methods for VO2-based thermochromic thin films.

a Chemical vapor deposition (CVD)174. b Physical vapor deposition (PVD)175. c Electrospinning89. d Spin coating176. e Film casting177. f 3D printing178

Guo et al. prepared thermochromic VO2 thin films (ΔTsol 9.7% and Tlum 52.3%) by LTCVD at a lower Tc. This reduction in Tc was attributed to the combined effects of strain and the presence of oxygen vacancies in the films during annealing. However, there has been limited emphasis on comparatively large-scale production, and the precursors commonly used as vanadium sources in the CVD process are typically toxic and environmentally unfriendly, such as VCl481, VO(acac)282, VO(OC3H7)383, etc. PVD is an extensively researched technique for depositing high-quality VO2 thin films, particularly for applications like smart windows, due to its ability to produce highly homogeneous products, good repeatability, and potential for large-scale production. Examples include magnetron sputtering (MS)63,84 and pulsed laser deposition (PLD)85, etc.

As illustrated in Fig. 6b, MS is a vacuum process used to deposit thin films on substrates by applying a high voltage across a low-pressure gas (usually argon) to create a “plasma”. Energized plasma ions strike the target and cause atoms from that target to be ejected with enough energy to travel to and bond with the substrate. While PVD methods offer superior quality and crystallinity in the fabrication of VO2 thin films compared to other techniques, the complexity and expense of the equipment, along with high maintenance costs, severely limit their practical widespread application in smart windows86. Furthermore, persisting issues include poor antioxidizability and weatherability87. Hence, there is a demand for facile, low-cost, eco-friendly, scalable, and high-quality fabrication methods for VO2-based thin films.

Electrospinning is a technique wherein a high electric field is directly applied to obtain fibers with diameters ranging from nanometers to micrometers88. This process typically comprises four components: a high-voltage power supply, a syringe pump, a spinneret, and a collector, as illustrated in Fig. 6c89. It is commonly employed in the fabrication of organic-inorganic film materials90.

In comparison with existing methods, the electrospinning technique is straightforward, mature, versatile, economical, and efficient for preparing continuous nanofibers with high porosity. These fibers have been proven to possess exceptional optical properties suitable for radiative-cooling applications91. Li et al. utilized electrospinning to prepare W-doped VO2/PVP composite fiber mats and identified two modes of the multiple scattering-absorbing process when light was absorbed by the fiber mats92. Due to the constitution of the fibers in the electrospun film, internal scattering is one of the reasons of low Tlum for electrospun thermochromic films. Therefore, proper Tlum-enhanced techniques are necessary. Lu et al. firstly fabricated PMMA-VO2 transparent composite smart film (ΔTsol 6.9% and Tlum 21%) with antioxidizability and super-hydrophobicity by electrospinning method, attributed to the gathered VO2 embedded in the fiber and aligned along the fiber axis. Subsequent heat treatment process significantly enhanced its Tlum87.

Spin coating is a solution-based technique employed to deposit uniform thin films onto flat substrates. Typically, a small amount of coating material is applied to the center of the substrate, which is then rotated at high speed to spread the coating material through centrifugal force, as illustrated in Fig. 6d. Zhao et al. synthesized W-VO2 thermochromic films (ΔTsol 8.8% and Tlum 41.5%) on an amorphous glass substrate using a simple spin coating method, which is economical, straightforward, and practical. However, high-speed spinning becomes challenging as the substrate size increases, making film thinning difficult. Additionally, the material efficiency of spin coating is relatively low93, which limits its application for large-scale production.

In film casting, a solution (referred to as “dope”) of a polymer in a solvent is prepared and then applied to a moving substrate belt with a smooth surface94. The wet film levels on the belt before entering the drying zone, where the solvent is completely removed to form a solid layer. Subsequently, the dry film is peeled from the belt, which then cycles back to the coating station, as depicted in Fig. 6e.

Gao et al. were the first to prepare transparent and flexible VSQ composite foils using an all-solution casting process. These foils exhibited a UV-shielding property and excellent thermochromic properties (ΔTsol 15.5% and Tlum 41%)95. In addition to wet coating with a solution, hot-melt casting is another method utilized for film deposition. A formulation is cast into a film from either hot melt or solution without solvent. The casting process offers several advantages over other methods, including simplicity of mold, low cost, absence of residual stresses, and suitability for low-production applications. It provides superior optical characteristics with a high degree of flatness compared to flat-sheet extrusion. However, casted parts may exhibit significant shrinkage post-solidification.

3D printing, or additive manufacturing, is a process for creating three-dimensional solid objects from a digital file. It encompasses various techniques, such as direct ink writing (DIW), stereolithography (SLA), selective laser melting (SLM)/selective laser sintering (SLS), and inject printing, among others. For example, one method involves selectively depositing droplets of printing materials to form the desired structure, utilizing an X-Y-Z three-axis motion platform, spray heads, and auxiliary curing devices96,97, as depicted in Fig. 6f. During the printing process, the fluid is ejected from the nozzle. With the movement of the platform, the ejected droplets are accurately deposited on the printing platform, and then solidified and formed at room temperature and atmospheric pressure. This method is low-cost, fast, efficient, flexible and suitable for the roll-to-roll process of complex structures, especially for materials that are difficult to form continuous wires.

However, there are limitations in printing height and mechanical properties of products. Ji et al. reported a straightforward large-scale fabrication of uniform VO2 thermochromic films using the inkjet printing technique (ΔTsol: 32.4%). Large area VO2 films (560 cm2) could be obtained with excellent uniformity, with the difference in NIR transmittance of regions on the film being within 0.3%98.

The fabrication of VO2-based thermochromic films is a multifaceted process with a variety of techniques offering different benefits. CVD and PVD are recognized for their high-quality film production, yet their scalability and environmental impact present challenges. Electrospinning and spin coating provide more accessible and cost-effective alternatives, with the potential for large-scale production.

Despite the success of existing fabrication methods at the laboratory scale, challenges remain in scaling up production and ensuring environmental adaptability. Future research is recommended to focus on the development of scalable, environmentally friendly, and cost-effective fabrication techniques. Additionally, it should explore new materials and structural designs to further enhance the performance and stability of VO2-based thermochromic films.

Other chromogenic materials

Despite significant efforts to enhance the optical responses of VO2-based thermochromic films, the overall Tlum and ΔTsol remain constrained due to the intrinsic absorption of VO2. In the following section, we delve into a variety of alternative chromogenic materials that exhibit significant optical property changes, which are extensively utilized to modulate solar radiation. The potential for synergistic integration of these materials with VO2 will be explored, with the aim of further refining spectral transmittance. Prominent among these are electro-, gaso-, mechano-, photochromic materials, each of which is activated by specific stimuli such as an electric field, gas exchange, mechanical stress, and light exposure. These smart chromogenic technologies each bring a unique set of advantages and challenges, and they are the focus of continuous innovation to improve their functionality and efficiency. The characteristics of various chromogenic materials are summarized in Table 4.Table 4 Characteristics of different chromogenic materials

Chromogenic material type	Characteristics	Fabrication methods	Cost	Pros	Cons	Ref.	
Electrochromic (TiO2, etc.)	Reversibly changing optical properties under electric field	Electrochemical deposition, solution immersion, etc.	Variable	Easy operation, IoT integration, adjustable color, excellent performance in reversible color change	Poor UV durability for polymer-based EC materials, low coloration efficiency, cycling stability issues, indoor-use restriction	101	
Gasochromic (WO3, etc.)	Displaying color change in response to chemical change or reaction	Sol-gel method, chemical vapor deposition, etc.	Low	Depth and switching speed controllable by film thickness and gas concentration, easy configuration and cost efficiency, high light transmittance	Requiring hydrogen and oxygen providing system	105,106	
Mechanochromic (PVA, PDMS, DABBF, etc.)	Responding to mechanical stimuli and changes in surface morphologies and internal structures	Mechanical processing, embossing, etc.	Low to moderate	Simple, eco-friendly, responsive	Biaxial strain and area expansion from stretching, short fatigue life of cracks under high strength mechanical loading cycles	109	
Photochromic (fulgide, diarylethene, spiropyran, TiO2, etc.)	Reversible transformation when exposed to specific wavelengths of light	Solution processing, electrochemical polymerization, etc.	Variable	Structural diversity, photochromic reversibility, processibility	Ineffective initial color restoration under UV illumination, limited photochromic library	121	
Thermochromic (VO2, perovskites, hydrogels, etc.)	Changing optical properties based on temperature	physical vapor deposition, chemical vapor deposition, sol-gel method, etc.	Low	Suitable for passive light modulation	Requirements for specific spectral characteristics	48	

Electrochromic (EC) materials could reversibly change the optical properties under the influence of electric field, including inorganic metal oxides (TiO299, etc.), organic polymers (propylenedioxythiophene100, etc.), inorganic-organic hybrids: coordination complex101, prussian blue102, liquid crystal (Fig. 7a)8, etc. EC applications are composed of EC material, electrolyte, ion storage layer, etc. and sandwiched by two transparent conductive electrodes103. The advantages of electrochromic (EC) materials include easy operation through a control system and integration into the Internet of Things (IoT). However, challenges such as poor UV durability (especially for polymer-based EC materials), coloration efficiency, cycling stability, and indoor-use restrictions remain to be addressed in the future. Sang et al. proposed a smart window (ΔTsol: 32.4% and Tlum: 0.4–40%) with a dual-band modulation function based on a simple three-layer structure of liquid crystal, VO2 and Al-doped ZnO, which can modulate the visible light actively by an external electric field and NIR light passively by temperature104.Fig. 7 Schematic illustrations of chromogenic materials undergoing various stimuli.

a Liquid-crystal-clad fibers by applying or removing a voltage at 25 °C179. b The adsorption/desorption of water molecules induced WO3 gasochromism180. c Mechanically triggered establishment of equilibrium between pale yellow DABBF and blue radicals181. d Reversible structural transformations of spiropyran under UV/visible light irradiation116. e Phase transitions of perovskites by heating or moisture7. Figures reproduced with permission from: (c), K. et al.116, American Chemical Society

Gasochromic (GC) materials are a type of thermochromics displaying a color change responding to a chemical change or reaction105,106. WO3 is a well-known example of GC materials. In a double-glazed structure, the internal surfaces coated with a WO3 film exhibit reversible light transmittance switching when alternately exposed to diluted hydrogen and oxygen gases, as illustrated in Fig. 7b. One advantage of GC materials, such as WO3, is that the depth and switching speed of color change can be controlled by adjusting the film thickness and the concentration of hydrogen and oxygen gases. Due to their straightforward and cost-effective layer configuration, as well as high light transmittance, WO3-based GC devices have garnered significant attention since the beginning of the 21st century107,108. However, a major limitation of these devices is the requirement for a system to provide hydrogen and oxygen gases.

Mechanochromic (MC) materials respond to mechanical stimuli which can deform and reconstruct the surface morphologies or internal structures with a change of their optical properties109, like polyvinyl alcohol (PVA)/PDMS110, diarylbibenzofuranone (DABBF) (Fig. 7c), etc. The MC applications are facile, eco-friendly, and responsive. The main obstacles to their commercialization include the significant applied biaxial strain and area expansion resulting from stretching, as well as the improvement of the fatigue life of cracks under high strength mechanical loading cycles without incurring catastrophic structural damage111,112. Ke et al. presented a bio-inspired thermo-mechanochromic dual-mode VO2/PVA/PDMS window (ΔTsol: 11.5% and Tlum: 17–60%), to respectively control the scattering for privacy and the absorbance for energy-efficiency, which are attributed to the controllable broadband diffraction via the dynamic wrinkles and VO2 NPs based on LSPR113.

Photochromic (PC) materials undergo reversible transformation when exposed to specific wavelengths of light, which could be roughly divided into organic and inorganic PC materials. Common examples include fulgide114, diarylethene115, spiropyran116 (as depicted in Fig. 7d), TiO2117, etc. Compared to inorganic counterparts, organic PC materials possess great advantage in structural diversity, photochromic reversibility, and processibility118,119. However, simply removing the UV is not sufficient to restore most organic PC materials to their initial color (except for naphthopyran)119,120, and more basic research is needed to enrich the library of photochromism. Sang et al. fabricated a novel VO2/spiropyran composite film (ΔTsol 23.6% and Tlum 31.55–48.6%), which could simultaneously modulate UV, visible, and NIR light with obvious color change from yellow to pink reversibly121.

Thermochromic materials enable a change in optical properties based on the temperature122, which is suitable for passive light modulation. In addition to VO248, perovskites (Fig. 7e)123 and hydrogels51 are also very representative. They have their own spectral characteristics towards application scenarios in demand.

The exploration of alternative chromogenic materials offers a promising avenue for addressing the limitations of VO2-based thermochromic coatings. These aforementioned materials demonstrate significant changes in optical properties and are widely utilized in solar radiation modulation. Integrating these materials with VO2 has the potential to further enhance functionality in smart windows. Each of these chromogenic technologies presents unique advantages and challenges, spurring continuous innovation to enhance their efficiency and performance. Through synergistic integration, these materials can enable smart windows to achieve improved optical responses and multifunctionality, thus facilitating their broader adoption in energy-efficient building applications.

Conclusion and outlook

Here, we present a comprehensive review on the VO2-based thermochromic coatings for smart windows. With the inspiring MIT transition, VO2 serves as a promising material for spectral transmittance modulation. Given the limitations of pristine VO2, such as its high transition temperature, low luminous transmittance, and weak solar-energy modulation ability, a variety of research approaches have been proposed, spanning from the crystal level to the structural level, including elemental doping and micro-nano structural engineering. Based on the latest researches, we discuss the principles and results of micro/nano-engineering in detail by categories including hybridization, core-shell structures and multilayer film design. Moreover, we summarize the fabrication methods of VO2 NPs and VO2-based thermochromic films. We also provide discussions on other chromogenic materials, which can be integrated for thermochromic smart windows as an alternative strategy to surpass the intrinsic limitation of VO2. Besides the above conclusions and summarizations, outlooks and prospects are discussed as follows, which aim to inspire more innovative progress and accelerate the development of this research field from the lab to the industry.

VO2-based thermochromic smart windows represent an important technology for increasing indoor comfort and reducing energy consumption in the building. Hence, this hotspot is promising and competitive. Some problems still need to be addressed to further widen their practical applications.Idealizing the optical responses including Tlum, ΔTsol and ΔTNIR. To facilitate the commercialization of VO2-based radiative cooling coatings, ideally ΔTsol and ΔTNIR should be respectively increased to 57% and 100% with high Tlum. This is where researchers had made efforts upon micro/nano-engineering. Further investigations on micro/nano-engineering should be revealed with more complex core-shell micro/nanostructures, higher order optical resonances and combining with other chromogenic materials discussed in Other Chromogenic Materials.

Continuous and various color changes. Color preference is tightly related to local customs with high versatility. For instance, a colorless coating or coloration with light blue/green is acceptable in China124. While gold or violet is more attractive in some areas of Southeastern Asia or Arabia125. More sophisticated core-shell or multilayer structure design can help us to achieve this goal.

Stability and lifetime. Vanadium is multivalent transition element, which reveals +3, +4, +5, and mixed valences. VO2(M) tends to be oxidized to V2O5 or their hydroxides, especially in a humid environment. This instability leads to low lifetime in practical applications. Therefore, the antioxidizability and hydrophobicity of VO2-based thermochromic films are worthy of our attention. VO2-based core-shell micro/nano-structure design might already enhance the antioxidizability to some extent, while affect the luminous transmittance of thermochromic films. Introducing hydrophobic groups on the surface of films to trap water molecules by grafting, etc. chemical modification means126 and protective film fabrication methods, i.e., electrospinning127 would be bright solutions.

Superior fabrication techniques for VO2-based thermochromic coatings need to be of large-scale, low-cost, high-quality, high efficiency, and eco-friendly, etc.

Broadening the multifunctionality of smart windows, e.g., introducing flexibility and foldability, integration of solar cells for electricity generation, integrated display for interactivity, etc.

Exploiting VO2 in advanced applications for radiative cooling128, warming129, and camouflage130,131: The potential of VO2 extends beyond smart windows into the realms of radiative cooling, warming, and camouflage technologies. The thermochromic nature of VO2 allows for the development of coatings that can dynamically regulate heat exchange with the environment, making them ideal candidates for applications where temperature control and thermal management are critical. For radiative cooling, VO2 coatings could automatically adjust their thermal emissivity to reflect more solar energy and emit more thermal radiation, thereby reducing the need for artificial cooling systems. In the context of warming, VO2 could be engineered to absorb more solar energy while reducing thermal radiation loss, providing an energy-efficient approach to heating. Moreover, in the field of camouflage, VO2-based coatings could change their thermal signature in response to environmental conditions, making objects less detectable by infrared sensors. The challenge lies in tailoring the phase transition temperature of VO2 to operate effectively under varying conditions and integrating these coatings into practical systems while maintaining their optical and thermal performance. Future research should focus on the scalable production of VO2 coatings with tailored properties, their integration with other advanced materials for enhanced performance, and the development of dynamic control systems for responsive thermal management.

To further elucidate the challenges and corresponding solution paths in the development of VO2-based thermochromic smart windows, we have prepared a summary, as depicted in Fig. 8. This figure provides readers with a clear visualization of the strategies proposed to address the challenges identified in this review, facilitating a deeper understanding of the research landscape and potential avenues for future exploration.Fig. 8 Challenges in the development of VO2-based thermochromic smart windows

Acknowledgements

C.J. and L.H. thanks Chunlei Su for checking the fabrication methods presented in the manuscript and Yang Fu and Shixuan Zhao for their guidance on core-shell structure simulations. D.L. thanks Tao Wang, Ying Liu, and Yanbo Fang for their proof reading of the manuscript.

Author contributions

C.J. and L.H. wrote the manuscript. D.L. supervised the project and revised the manuscript. All authors participated in the discussions.

Funding

We acknowledge the financial support by the City University of Hong Kong through an ARG project (9667246), the Innovation and Technology Commission of Hong Kong through a Mainland-Hong Kong Joint Funding Scheme grant (MHP/162/22), and the Research Grants Council of Hong Kong through a Collaborative Research Project Grant (C5050-22GF).

Conflict of interest

The authors declare no competing interests.

These authors contributed equally: Cancheng Jiang, Lanyue He
==== Refs
References

1. Ramesh T Prakash R Shukla KK Life cycle energy analysis of buildings: an overview Energy Build 2010 42 1592 1600 10.1016/j.enbuild.2010.05.007
Ramesh, T., Prakash, R. & Shukla, K. K. Life cycle energy analysis of buildings: an overview. Energy Build 42, 1592–1600 (2010).
2. Baetens R Jelle BP Gustavsen A Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review Sol. Energy Mater. Sol. Cells 2010 94 87 105 10.1016/j.solmat.2009.08.021
Baetens, R., Jelle, B. P. & Gustavsen, A. Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review. Sol. Energy Mater. Sol. Cells 94, 87–105 (2010).
3. Park HK Kim H Acoustic insulation performance of improved airtight windows Constr. Build. Mater. 2015 93 542 550 10.1016/j.conbuildmat.2015.05.058
Park, H. K. & Kim, H. Acoustic insulation performance of improved airtight windows. Constr. Build. Mater. 93, 542–550 (2015).
4. Tuchinda C Srivannaboon S Lim HW Photoprotection by window glass, automobile glass, and sunglasses J. Am. Acad. Dermatol. 2006 54 845 854 10.1016/j.jaad.2005.11.1082 16635665
Tuchinda, C., Srivannaboon, S. & Lim, H. W. Photoprotection by window glass, automobile glass, and sunglasses. J. Am. Acad. Dermatol. 54, 845–854 (2006).16635665
5. Edlich R Use of UV-protective windows and window films to aid in the prevention of skin cancer J. Long-Term Eff. Med. Implants 2004 14 15 10.1615/JLongTermEffMedImplants.v14.i5.70
Edlich, R. et al. Use of UV-protective windows and window films to aid in the prevention of skin cancer. J. Long-Term Eff. Med. Implants 14, 15 (2004).
6. Chabane, I. J. & Bensalem, R. In The 23rd Conference on Passive and Low Energy Architecture. (Geneva, Switzerland, 2006).
7. Lin J Thermochromic halide perovskite solar cells Nat. Mater. 2018 17 261 267 10.1038/s41563-017-0006-0 29358645
Lin, J. et al. Thermochromic halide perovskite solar cells. Nat. Mater. 17, 261–267 (2018).29358645
8. Heo J Huh J-W Yoon T-H Fast-switching initially-transparent liquid crystal light shutter with crossed patterned electrodes AIP Adv. 2015 5 047118 10.1063/1.4918277
Heo, J., Huh, J.-W. & Yoon, T.-H. Fast-switching initially-transparent liquid crystal light shutter with crossed patterned electrodes. AIP Adv. 5, 047118 (2015).
9. Kwon, J. et al. In Emerging Liquid Crystal Technologies XV. (SPIE, 2020).
10. Lei DY Optically-triggered nanoscale memory effect in a hybrid plasmonic-phase changing nanostructure ACS Photonics 2015 2 1306 1313 10.1021/acsphotonics.5b00249
Lei, D. Y. et al. Optically-triggered nanoscale memory effect in a hybrid plasmonic-phase changing nanostructure. ACS Photonics 2, 1306–1313 (2015).
11. Liang J Hou L Li J Frequency tunable perfect absorber in visible and near-infrared regimes based on VO 2 phase transition using planar layered thin films JOSA B 2016 33 1075 1080 10.1364/JOSAB.33.001075
Liang, J., Hou, L. & Li, J. Frequency tunable perfect absorber in visible and near-infrared regimes based on VO 2 phase transition using planar layered thin films. JOSA B 33, 1075–1080 (2016).
12. Liang J Zhao Y Zhu K Guo J Zhou L Synthesis and room temperature NO2 gas sensitivity of vanadium dioxide nanowire structures by chemical vapor deposition Thin Solid Films 2019 669 537 543 10.1016/j.tsf.2018.11.046
Liang, J., Zhao, Y., Zhu, K., Guo, J. & Zhou, L. Synthesis and room temperature NO2 gas sensitivity of vanadium dioxide nanowire structures by chemical vapor deposition. Thin Solid Films 669, 537–543 (2019).
13. Yang Z Ko C Ramanathan S Oxide electronics utilizing ultrafast metal-insulator transitions Annu. Rev. Mater. Res. 2011 41 337 367 10.1146/annurev-matsci-062910-100347
Yang, Z., Ko, C. & Ramanathan, S. Oxide electronics utilizing ultrafast metal-insulator transitions. Annu. Rev. Mater. Res. 41, 337–367 (2011).
14. Goodenough JB The two components of the crystallographic transition in VO2 J. Solid State Chem. 1971 3 490 500 10.1016/0022-4596(71)90091-0
Goodenough, J. B. The two components of the crystallographic transition in VO2. J. Solid State Chem. 3, 490–500 (1971).
15. Yu F-y A terahertz tunable metamaterial reflective polarization converter based on vanadium oxide film Plasmonics 2022 17 823 829 10.1007/s11468-021-01590-8
Yu, F.-y et al. A terahertz tunable metamaterial reflective polarization converter based on vanadium oxide film. Plasmonics 17, 823–829 (2022).
16. Yu F-y Zhu J-b Shen X-b Tunable and reflective polarization converter based on single-layer vanadium dioxide-integrated metasurface in terahertz region Opt. Mater. 2022 123 111745 10.1016/j.optmat.2021.111745
Yu, F.-y, Zhu, J.-b. & Shen, X.-b Tunable and reflective polarization converter based on single-layer vanadium dioxide-integrated metasurface in terahertz region. Opt. Mater. 123, 111745 (2022).
17. Liu M Dual-phase transformation: Spontaneous self-template surface-patterning strategy for ultra-transparent VO2 solar modulating coatings Acs Nano 2017 11 407 415 10.1021/acsnano.6b06152 28009507
Liu, M. et al. Dual-phase transformation: Spontaneous self-template surface-patterning strategy for ultra-transparent VO2 solar modulating coatings. Acs Nano 11, 407–415 (2017).28009507
18. Cui Y Thermochromic VO2 for energy-efficient smart windows Joule 2018 2 1707 1746 10.1016/j.joule.2018.06.018
Cui, Y. et al. Thermochromic VO2 for energy-efficient smart windows. Joule 2, 1707–1746 (2018).
19. Son SB Youn JW Kim K-S Kim DU Optical properties of periodic micropatterned VO2 thermochromic films prepared by thermal and intense pulsed light sintering Mater. Des. 2019 182 107970 10.1016/j.matdes.2019.107970
Son, S. B., Youn, J. W., Kim, K.-S. & Kim, D. U. Optical properties of periodic micropatterned VO2 thermochromic films prepared by thermal and intense pulsed light sintering. Mater. Des. 182, 107970 (2019).
20. Liang J Song X Li J Lan K Li P A visible-near infrared wavelength-tunable metamaterial absorber based on the structure of Au triangle arrays embedded in VO2 thin film J. Alloy. Compd. 2017 708 999 1007 10.1016/j.jallcom.2017.03.110
Liang, J., Song, X., Li, J., Lan, K. & Li, P. A visible-near infrared wavelength-tunable metamaterial absorber based on the structure of Au triangle arrays embedded in VO2 thin film. J. Alloy. Compd. 708, 999–1007 (2017).
21. Wyszecki, G. & Stiles, W. S. Color Science. 982 (John Wiley & Sons, New York, 1982).
22. Jelle BP Solar radiation glazing factors for window panes, glass structures and electrochromic windows in buildings—Measurement and calculation Sol. Energy Mater. Sol. Cells 2013 116 291 323 10.1016/j.solmat.2013.04.032
Jelle, B. P. Solar radiation glazing factors for window panes, glass structures and electrochromic windows in buildings—Measurement and calculation. Sol. Energy Mater. Sol. Cells 116, 291–323 (2013).
23. Wyszecki, G. & Stiles, W. S. Color science: concepts and methods, quantitative data and formulae Vol. 40. (John Wiley & Sons, 2000)
24. ASTM, Standard Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface. (ASTM G173-03, https://www.astm.org/g0173-03r20.html. Accessed 2020).
25. ISO 9050. Glass in building-determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors. (ISO, Geneva, Switzerland, 2003(E)).
26. ISO 10526. CIE standard illuminants for calorimetry. (ISO, Geneva, Switzerland, 1999(E).
27. Yuan X Zhang W Zhang P Hole-lattice coupling and photoinduced insulator-metal transition in VO 2 Phys. Rev. B 2013 88 035119 10.1103/PhysRevB.88.035119
Yuan, X., Zhang, W. & Zhang, P. Hole-lattice coupling and photoinduced insulator-metal transition in VO 2. Phys. Rev. B 88, 035119 (2013).
28. Yuan X Zhang Y Abtew TA Zhang P Zhang W VO 2: Orbital competition, magnetism, and phase stability Phys. Rev. B 2012 86 235103 10.1103/PhysRevB.86.235103
Yuan, X., Zhang, Y., Abtew, T. A., Zhang, P. & Zhang, W. VO 2: Orbital competition, magnetism, and phase stability. Phys. Rev. B 86, 235103 (2012).
29. Cui Y Shi S Chen L Luo H Gao Y Hydrogen-doping induced reduction in the phase transition temperature of VO 2: a first-principles study Phys. Chem. Chem. Phys. 2015 17 20998 21004 10.1039/C5CP03267A 26214593
Cui, Y., Shi, S., Chen, L., Luo, H. & Gao, Y. Hydrogen-doping induced reduction in the phase transition temperature of VO 2: a first-principles study. Phys. Chem. Chem. Phys. 17, 20998–21004 (2015).26214593
30. Fan L A facile strategy to realize rapid and heavily hydrogen-doped VO2 and study of hydrogen ion diffusion behavior J. Phys. Chem. C. 2022 126 5004 5013 10.1021/acs.jpcc.1c09722
Fan, L. et al. A facile strategy to realize rapid and heavily hydrogen-doped VO2 and study of hydrogen ion diffusion behavior. J. Phys. Chem. C. 126, 5004–5013 (2022).
31. Cui Y Wang Y Liu B Luo H Gao Y First-principles study on the phase transition temperature of X-doped (X= Li, Na or K) VO 2 RSC Adv. 2016 6 64394 64399 10.1039/C6RA10221B
Cui, Y., Wang, Y., Liu, B., Luo, H. & Gao, Y. First-principles study on the phase transition temperature of X-doped (X= Li, Na or K) VO 2. RSC Adv. 6, 64394–64399 (2016).
32. Chen Y Electric-field control of Li-doping induced phase transition in VO2 film with crystal facet-dependence Nano Energy 2018 51 300 307 10.1016/j.nanoen.2018.06.070
Chen, Y. et al. Electric-field control of Li-doping induced phase transition in VO2 film with crystal facet-dependence. Nano Energy 51, 300–307 (2018).
33. Top I The effect of alkali metal (Na, K) doping on thermochromic properties of VO2 films MRS Adv. 2018 3 1863 1869 10.1557/adv.2018.70
Top, I. et al. The effect of alkali metal (Na, K) doping on thermochromic properties of VO2 films. MRS Adv. 3, 1863–1869 (2018).
34. Zhou Q Boron doped M-phase VO2 nanoparticles with low metal-insulator phase transition temperature for smart windows Ceram. Int. 2020 46 4786 4794 10.1016/j.ceramint.2019.10.211
Zhou, Q. et al. Boron doped M-phase VO2 nanoparticles with low metal-insulator phase transition temperature for smart windows. Ceram. Int. 46, 4786–4794 (2020).
35. Hajlaoui T Metal–insulator transition temperature of boron-doped VO2 thin films grown by reactive pulsed laser deposition Scr. Materialia 2020 177 32 37 10.1016/j.scriptamat.2019.09.019
Hajlaoui, T. et al. Metal–insulator transition temperature of boron-doped VO2 thin films grown by reactive pulsed laser deposition. Scr. Materialia 177, 32–37 (2020).
36. Hu L Porous W-doped VO2 films with simultaneously enhanced visible transparency and thermochromic properties J. Sol.-Gel Sci. Technol. 2016 77 85 93 10.1007/s10971-015-3832-z
Hu, L. et al. Porous W-doped VO2 films with simultaneously enhanced visible transparency and thermochromic properties. J. Sol.-Gel Sci. Technol. 77, 85–93 (2016).
37. Bleu Y Towards Room Temperature Phase Transition of W-Doped VO2 Thin Films Deposited by Pulsed Laser Deposition: Thermochromic, Surface, and Structural Analysis Materials 2023 16 461 10.3390/ma16010461 36614799
Bleu, Y. et al. Towards Room Temperature Phase Transition of W-Doped VO2 Thin Films Deposited by Pulsed Laser Deposition: Thermochromic, Surface, and Structural Analysis. Materials 16, 461 (2023).36614799
38. Mai L Hu B Hu T Chen W Gu E Electrical property of Mo-doped VO2 nanowire array film by melting− quenching sol− gel method J. Phys. Chem. B 2006 110 19083 19086 10.1021/jp0642701 17004750
Mai, L., Hu, B., Hu, T., Chen, W. & Gu, E. Electrical property of Mo-doped VO2 nanowire array film by melting− quenching sol− gel method. J. Phys. Chem. B 110, 19083–19086 (2006).17004750
39. Piccirillo C Binions R Parkin IP Nb-Doped VO2 Thin Films Prepared by Aerosol-Assisted Chemical Vapour Deposition Eur. J. lnorg. Chem. 2007 25 4050 4055 10.1002/ejic.200700284
Piccirillo, C., Binions, R. & Parkin, I. P. Nb-Doped VO2 Thin Films Prepared by Aerosol-Assisted Chemical Vapour Deposition. Eur. J. lnorg. Chem. 25, 4050–4055 (2007).
40. Cui Y Cao C Chen Z Luo H Gao Y Atomic and electronic structures of thermochromic VO2 with Sb-doping Computational Mater. Sci. 2017 130 103 108 10.1016/j.commatsci.2017.01.016
Cui, Y., Cao, C., Chen, Z., Luo, H. & Gao, Y. Atomic and electronic structures of thermochromic VO2 with Sb-doping. Computational Mater. Sci. 130, 103–108 (2017).
41. Zhang J He H Xie Y Pan B Giant reduction of the phase transition temperature for beryllium doped VO 2 Phys. Chem. Chem. Phys. 2013 15 4687 4690 10.1039/c3cp44476g 23423531
Zhang, J., He, H., Xie, Y. & Pan, B. Giant reduction of the phase transition temperature for beryllium doped VO 2. Phys. Chem. Chem. Phys. 15, 4687–4690 (2013).23423531
42. Shao Z Tri-band electrochromic smart window for energy savings in buildings Nat. Sustain. 2024 7 796 803 10.1038/s41893-024-01349-z
Shao, Z. et al. Tri-band electrochromic smart window for energy savings in buildings. Nat. Sustain. 7, 796–803 (2024).
43. Appavoo K Role of defects in the phase transition of VO2 nanoparticles probed by plasmon resonance spectroscopy Nano Lett. 2012 12 780 786 10.1021/nl203782y 22273268
Appavoo, K. et al. Role of defects in the phase transition of VO2 nanoparticles probed by plasmon resonance spectroscopy. Nano Lett. 12, 780–786 (2012).22273268
44. Lazarovits B Kim K Haule K Kotliar G Effects of strain on the electronic structure of VO 2 Phys. Rev. B 2010 81 115117 10.1103/PhysRevB.81.115117
Lazarovits, B., Kim, K., Haule, K. & Kotliar, G. Effects of strain on the electronic structure of VO 2. Phys. Rev. B 81, 115117 (2010).
45. Chen Z Cao C Chen S Luo H Gao Y Crystallised mesoporous TiO 2 (A)–VO 2 (M/R) nanocomposite films with self-cleaning and excellent thermochromic properties J. Mater. Chem. A 2014 2 11874 11884 10.1039/C4TA01585A
Chen, Z., Cao, C., Chen, S., Luo, H. & Gao, Y. Crystallised mesoporous TiO 2 (A)–VO 2 (M/R) nanocomposite films with self-cleaning and excellent thermochromic properties. J. Mater. Chem. A 2, 11874–11884 (2014).
46. Du J Formation and metal-to-insulator transition properties of VO2–ZrV2O7 composite films by polymer-assisted deposition Sol. energy Mater. Sol. cells 2011 95 1604 1609 10.1016/j.solmat.2011.01.009
Du, J. et al. Formation and metal-to-insulator transition properties of VO2–ZrV2O7 composite films by polymer-assisted deposition. Sol. energy Mater. Sol. cells 95, 1604–1609 (2011).
47. Li S-Y Niklasson GA Granqvist C-G Nanothermochromics: Calculations for VO 2 nanoparticles in dielectric hosts show much improved luminous transmittance and solar energy transmittance modulation J. Appl. Phys. 2010 108 063525 10.1063/1.3487980
Li, S.-Y., Niklasson, G. A. & Granqvist, C.-G. Nanothermochromics: Calculations for VO 2 nanoparticles in dielectric hosts show much improved luminous transmittance and solar energy transmittance modulation. J. Appl. Phys. 108, 063525 (2010).
48. Liang J Wang S Lei D Wang Z Li X Enhanced visible and tunable infrared transmittance of W-doped VO2/SiO2/PVP composite films for smart windows Optical Mater. 2021 121 111485 10.1016/j.optmat.2021.111485
Liang, J., Wang, S., Lei, D., Wang, Z. & Li, X. Enhanced visible and tunable infrared transmittance of W-doped VO2/SiO2/PVP composite films for smart windows. Optical Mater. 121, 111485 (2021).
49. Hao Q VO2/TiN plasmonic thermochromic smart coatings for room‐temperature applications Adv. Mater. 2018 30 1705421 10.1002/adma.201705421
Hao, Q. et al. VO2/TiN plasmonic thermochromic smart coatings for room‐temperature applications. Adv. Mater. 30, 1705421 (2018).
50. Cao Z Tunable simultaneously visible-light and near-infrared transmittance for VO2/SiO2 composite films to enhance thermochromic properties Mater. Lett. 2017 209 609 612 10.1016/j.matlet.2017.08.113
Cao, Z. et al. Tunable simultaneously visible-light and near-infrared transmittance for VO2/SiO2 composite films to enhance thermochromic properties. Mater. Lett. 209, 609–612 (2017).
51. He Q PAM-PNIPAM/W-doped VO2 thermochromic hydrogel film with high solar modulation capability for smart windows deployment Optical Mater. 2019 97 109367 10.1016/j.optmat.2019.109367
He, Q. et al. PAM-PNIPAM/W-doped VO2 thermochromic hydrogel film with high solar modulation capability for smart windows deployment. Optical Mater. 97, 109367 (2019).
52. Liang J Periodic Arrays of 3D AuNP‐Capped VO2 Shells and Their Temperature‐Tunable SERS Performance Adv. Optical Mater. 2022 10 2102615 10.1002/adom.202102615
Liang, J. et al. Periodic Arrays of 3D AuNP‐Capped VO2 Shells and Their Temperature‐Tunable SERS Performance. Adv. Optical Mater. 10, 2102615 (2022).
53. Xie Y Influence of shell materials on the optical performance of VO2 core–shell nanoparticle–based thermochromic films Mater. Today Nano 2021 13 100102 10.1016/j.mtnano.2020.100102
Xie, Y. et al. Influence of shell materials on the optical performance of VO2 core–shell nanoparticle–based thermochromic films. Mater. Today Nano 13, 100102 (2021).
54. Pi J Superhydrophobic and thermochromic VO2-Based composite coatings for energy-saving smart windows Compos. Commun. 2022 32 101167 10.1016/j.coco.2022.101167
Pi, J. et al. Superhydrophobic and thermochromic VO2-Based composite coatings for energy-saving smart windows. Compos. Commun. 32, 101167 (2022).
55. Zhou Y Surface plasmon resonance induced excellent solar control for VO 2@ SiO 2 nanorods-based thermochromic foils Nanoscale 2013 5 9208 9213 10.1039/c3nr02221h 23934483
Zhou, Y. et al. Surface plasmon resonance induced excellent solar control for VO 2@ SiO 2 nanorods-based thermochromic foils. Nanoscale 5, 9208–9213 (2013).23934483
56. Lu X A novel method to modify the color of VO 2-based thermochromic smart films by solution-processed VO 2@ SiO 2@ Au core–shell nanoparticles RSC Adv. 2016 6 47249 47257 10.1039/C6RA07594K
Lu, X. et al. A novel method to modify the color of VO 2-based thermochromic smart films by solution-processed VO 2@ SiO 2@ Au core–shell nanoparticles. RSC Adv. 6, 47249–47257 (2016).
57. Yao L Three‐layered hollow nanospheres based coatings with ultrahigh‐performance of energy‐saving, antireflection, and self‐cleaning for smart windows Small 2018 14 1801661 10.1002/smll.201801661
Yao, L. et al. Three‐layered hollow nanospheres based coatings with ultrahigh‐performance of energy‐saving, antireflection, and self‐cleaning for smart windows. Small 14, 1801661 (2018).
58. Lee M Photonic structures in radiative cooling Light Sci. Appl. 2023 12 134 10.1038/s41377-023-01119-0 37264035
Lee, M. et al. Photonic structures in radiative cooling. Light Sci. Appl. 12, 134 (2023).37264035
59. Parker J Raman scattering from VO 2 single crystals: A study of the effects of surface oxidation Phys. Rev. B 1990 42 3164 10.1103/PhysRevB.42.3164
Parker, J. Raman scattering from VO 2 single crystals: A study of the effects of surface oxidation. Phys. Rev. B 42, 3164 (1990).
60. Zhan Y The growth mechanism of VO2 multilayer thin films with high thermochromic performance prepared by RTA in air Surf. Interfaces 2017 9 173 181 10.1016/j.surfin.2017.09.002
Zhan, Y. et al. The growth mechanism of VO2 multilayer thin films with high thermochromic performance prepared by RTA in air. Surf. Interfaces 9, 173–181 (2017).
61. Liu H SnO2/VO2/SnO2 tri-layer thermochromic films with high luminous transmittance, remarkable solar modulation ability and excellent hydrophobicity grown on glass substrates Infrared Phys. Technol. 2021 113 103648 10.1016/j.infrared.2021.103648
Liu, H. et al. SnO2/VO2/SnO2 tri-layer thermochromic films with high luminous transmittance, remarkable solar modulation ability and excellent hydrophobicity grown on glass substrates. Infrared Phys. Technol. 113, 103648 (2021).
62. Ji Y Mattsson A Niklasson GA Granqvist CG Österlund L Synergistic TiO2/VO2 window coating with thermochromism, enhanced luminous transmittance, and photocatalytic activity Joule 2019 3 2457 2471 10.1016/j.joule.2019.06.024
Ji, Y., Mattsson, A., Niklasson, G. A., Granqvist, C. G. & Österlund, L. Synergistic TiO2/VO2 window coating with thermochromism, enhanced luminous transmittance, and photocatalytic activity. Joule 3, 2457–2471 (2019).
63. Zheng J Bao S Jin P TiO2 (R)/VO2 (M)/TiO2 (A) multilayer film as smart window: Combination of energy-saving, antifogging and self-cleaning functions Nano Energy 2015 11 136 145 10.1016/j.nanoen.2014.09.023
Zheng, J., Bao, S. & Jin, P. TiO2 (R)/VO2 (M)/TiO2 (A) multilayer film as smart window: Combination of energy-saving, antifogging and self-cleaning functions. Nano Energy 11, 136–145 (2015).
64. Liu C Index-tunable anti-reflection coatings: Maximizing solar modulation ability for vanadium dioxide-based smart thermochromic glazing J. Alloy. Compd. 2018 731 1197 1207 10.1016/j.jallcom.2017.10.045
Liu, C. et al. Index-tunable anti-reflection coatings: Maximizing solar modulation ability for vanadium dioxide-based smart thermochromic glazing. J. Alloy. Compd. 731, 1197–1207 (2018).
65. Xu F Highly enhanced thermochromic performance of VO2 film using “movable” antireflective coatings ACS Appl. Mater. interfaces 2019 11 4712 4718 10.1021/acsami.8b20794 30672290
Xu, F. et al. Highly enhanced thermochromic performance of VO2 film using “movable” antireflective coatings. ACS Appl. Mater. interfaces 11, 4712–4718 (2019).30672290
66. Li J Ultrathin, soft, radiative cooling interfaces for advanced thermal management in skin electronics Sci. Adv. 2023 9 eadg1837 10.1126/sciadv.adg1837 37027471
Li, J. et al. Ultrathin, soft, radiative cooling interfaces for advanced thermal management in skin electronics. Sci. Adv. 9, eadg1837 (2023).37027471
67. An Y Fu Y Dai J-G Yin X Lei D Switchable radiative cooling technologies for smart thermal management Cell Rep. Phys. Sci. 2022 3 101098 10.1016/j.xcrp.2022.101098
An, Y., Fu, Y., Dai, J.-G., Yin, X. & Lei, D. Switchable radiative cooling technologies for smart thermal management. Cell Rep. Phys. Sci. 3, 101098 (2022).
68. Ma X Fluorescence‐Enabled Colored Bilayer Subambient Radiative Cooling Coatings Adv. Opt. Mater. 2024 11 2303296 10.1002/adom.202303296
Ma, X. et al. Fluorescence‐Enabled Colored Bilayer Subambient Radiative Cooling Coatings. Adv. Opt. Mater. 11, 2303296 (2024).
69. Fu Y An Y Xu Y Dai JG Lei D Polymer coating with gradient‐dispersed dielectric nanoparticles for enhanced daytime radiative cooling EcoMat 2022 4 e12169 10.1002/eom2.12169
Fu, Y., An, Y., Xu, Y., Dai, J. G. & Lei, D. Polymer coating with gradient‐dispersed dielectric nanoparticles for enhanced daytime radiative cooling. EcoMat 4, e12169 (2022).
70. Wang S Scalable thermochromic smart windows with passive radiative cooling regulation Science 2021 374 1501 1504 10.1126/science.abg0291 34914526
Wang, S. et al. Scalable thermochromic smart windows with passive radiative cooling regulation. Science 374, 1501–1504 (2021).34914526
71. Tang K Temperature-adaptive radiative coating for all-season household thermal regulation Science 2021 374 1504 1509 10.1126/science.abf7136 34914515
Tang, K. et al. Temperature-adaptive radiative coating for all-season household thermal regulation. Science 374, 1504–1509 (2021).34914515
72. Lang F Wang H Zhang S Liu J Yan H Review on variable emissivity materials and devices based on smart chromism Int. J. Thermophys. 2018 39 1 20 10.1007/s10765-017-2329-0
Lang, F., Wang, H., Zhang, S., Liu, J. & Yan, H. Review on variable emissivity materials and devices based on smart chromism. Int. J. Thermophys. 39, 1–20 (2018).
73. Xue X Creating an eco‐friendly building coating with smart subambient radiative cooling Adv. Mater. 2020 32 1906751 10.1002/adma.201906751
Xue, X. et al. Creating an eco‐friendly building coating with smart subambient radiative cooling. Adv. Mater. 32, 1906751 (2020).
74. Ma X Effects of Stokes shift and Purcell enhancement on fluorescence-assisted radiative cooling J. Mater. Chem. A 2022 10 19635 19640 10.1039/D2TA02259A
Ma, X. et al. Effects of Stokes shift and Purcell enhancement on fluorescence-assisted radiative cooling. J. Mater. Chem. A 10, 19635–19640 (2022).
75. Yang N Fu Y Xue X Lei D Dai JG Geopolymer‐based sub‐ambient daytime radiative cooling coating EcoMat 2023 5 e12284 10.1002/eom2.12284
Yang, N., Fu, Y., Xue, X., Lei, D. & Dai, J. G. Geopolymer‐based sub‐ambient daytime radiative cooling coating. EcoMat 5, e12284 (2023).
76. Zhu Y Color-preserving passive radiative cooling for an actively temperature-regulated enclosure Light Sci. Appl. 2022 11 122 10.1038/s41377-022-00810-y 35508472
Zhu, Y. et al. Color-preserving passive radiative cooling for an actively temperature-regulated enclosure. Light Sci. Appl. 11, 122 (2022).35508472
77. Liu Y Intelligent regulation of VO2-PDMS-driven radiative cooling Appl. Phys. Lett. 2022 120 171704 10.1063/5.0089353
Liu, Y. et al. Intelligent regulation of VO2-PDMS-driven radiative cooling. Appl. Phys. Lett. 120, 171704 (2022).
78. Warwick ME Binions R Electric field assisted aerosol assisted chemical vapor deposition of nanostructured metal oxide thin films Surf. Coat. Technol. 2013 230 28 32 10.1016/j.surfcoat.2013.06.005
Warwick, M. E. & Binions, R. Electric field assisted aerosol assisted chemical vapor deposition of nanostructured metal oxide thin films. Surf. Coat. Technol. 230, 28–32 (2013).
79. Ligmajer F Epitaxial VO2 nanostructures: a route to large-scale, switchable dielectric metasurfaces ACS photonics 2018 5 2561 2567 10.1021/acsphotonics.7b01384
Ligmajer, F. et al. Epitaxial VO2 nanostructures: a route to large-scale, switchable dielectric metasurfaces. ACS photonics 5, 2561–2567 (2018).
80. Guo B Low temperature fabrication of thermochromic VO 2 thin films by low-pressure chemical vapor deposition RSC Adv. 2017 7 10798 10805 10.1039/C6RA25071H
Guo, B. et al. Low temperature fabrication of thermochromic VO 2 thin films by low-pressure chemical vapor deposition. RSC Adv. 7, 10798–10805 (2017).
81. Gaskell JM Optimised atmospheric pressure CVD of monoclinic VO2 thin films with picosecond phase transition Surf. Coat. Technol. 2016 287 160 165 10.1016/j.surfcoat.2015.12.090
Gaskell, J. M. et al. Optimised atmospheric pressure CVD of monoclinic VO2 thin films with picosecond phase transition. Surf. Coat. Technol. 287, 160–165 (2016).
82. Yin H Yu K Song C Wang Z Zhu Z Low-temperature CVD synthesis of patterned core–shell VO 2@ ZnO nanotetrapods and enhanced temperature-dependent field-emission properties Nanoscale 2014 6 11820 11827 10.1039/C4NR02661F 25163668
Yin, H., Yu, K., Song, C., Wang, Z. & Zhu, Z. Low-temperature CVD synthesis of patterned core–shell VO 2@ ZnO nanotetrapods and enhanced temperature-dependent field-emission properties. Nanoscale 6, 11820–11827 (2014).25163668
83. Vernardou D Louloudakis D Spanakis E Katsarakis N Koudoumas E Thermochromic amorphous VO2 coatings grown by APCVD using a single-precursor Sol. energy Mater. Sol. cells 2014 128 36 40 10.1016/j.solmat.2014.04.033
Vernardou, D., Louloudakis, D., Spanakis, E., Katsarakis, N. & Koudoumas, E. Thermochromic amorphous VO2 coatings grown by APCVD using a single-precursor. Sol. energy Mater. Sol. cells 128, 36–40 (2014).
84. Zhan Y Enhanced thermal stability and thermochromic properties of VOx-based thin films by room-temperature magnetron sputtering Sol. Energy Mater. Sol. Cells 2018 174 102 111 10.1016/j.solmat.2017.08.030
Zhan, Y. et al. Enhanced thermal stability and thermochromic properties of VOx-based thin films by room-temperature magnetron sputtering. Sol. Energy Mater. Sol. Cells 174, 102–111 (2018).
85. Chang T Flexible VO2 thermochromic films with narrow hysteresis loops Sol. Energy Mater. Sol. Cells 2021 219 110799 10.1016/j.solmat.2020.110799
Chang, T. et al. Flexible VO2 thermochromic films with narrow hysteresis loops. Sol. Energy Mater. Sol. Cells 219, 110799 (2021).
86. Manning TD Parkin IP Blackman C Qureshi U APCVD of thermochromic vanadium dioxide thin films—solid solutions V 2− x M x O 2 (M= Mo, Nb) or composites VO 2: SnO 2 J. Mater. Chem. 2005 15 4560 4566 10.1039/b510552h
Manning, T. D., Parkin, I. P., Blackman, C. & Qureshi, U. APCVD of thermochromic vanadium dioxide thin films—solid solutions V 2− x M x O 2 (M= Mo, Nb) or composites VO 2: SnO 2. J. Mater. Chem. 15, 4560–4566 (2005).
87. Lu Y Transparent optically vanadium dioxide thermochromic smart film fabricated via electrospinning technique Appl. Surf. Sci. 2017 425 233 240 10.1016/j.apsusc.2017.07.035
Lu, Y. et al. Transparent optically vanadium dioxide thermochromic smart film fabricated via electrospinning technique. Appl. Surf. Sci. 425, 233–240 (2017).
88. He X Electrospun quantum dots/polymer composite porous fibers for turn-on fluorescent detection of lactate dehydrogenase J. Mater. Chem. 2012 22 18471 18478 10.1039/c2jm33078d
He, X. et al. Electrospun quantum dots/polymer composite porous fibers for turn-on fluorescent detection of lactate dehydrogenase. J. Mater. Chem. 22, 18471–18478 (2012).
89. Tebyetekerwa M Xu Z Yang S Ramakrishna S Electrospun nanofibers-based face masks, Advanced Fiber Materials 2020 2 161 166
Tebyetekerwa, M., Xu, Z., Yang, S. & Ramakrishna, S. Electrospun nanofibers-based face masks, Advanced Fiber. Materials 2, 161–166 (2020).
90. Tang K Self-reduced VO/VOx/carbon nanofiber composite as binder-free electrode for supercapacitors Electrochim. Acta 2016 209 709 718 10.1016/j.electacta.2016.05.051
Tang, K. et al. Self-reduced VO/VOx/carbon nanofiber composite as binder-free electrode for supercapacitors. Electrochim. Acta 209, 709–718 (2016).
91. Shi NN Nanostructured fibers as a versatile photonic platform: radiative cooling and waveguiding through transverse Anderson localization Light Sci. Appl. 2018 7 37 10.1038/s41377-018-0033-x 30839604
Shi, N. N. et al. Nanostructured fibers as a versatile photonic platform: radiative cooling and waveguiding through transverse Anderson localization. Light Sci. Appl. 7, 37 (2018).30839604
92. Li S Functional fiber mats with tunable diffuse reflectance composed of electrospun VO2/PVP composite fibers ACS Appl. Mater. Interfaces 2014 6 9 13 10.1021/am405006g 24344924
Li, S. et al. Functional fiber mats with tunable diffuse reflectance composed of electrospun VO2/PVP composite fibers. ACS Appl. Mater. Interfaces 6, 9–13 (2014).24344924
93. Yilbas, B. S., Al-Sharafi, A. & Ali, H. In Self-Cleaning of Surfaces and Water Droplet Mobility. (eds Yilbas, B. S., Al-Sharafi, A., and Ali, H) 45-98 (Elsevier, 2019)
94. Narukawa Y. & Scriven, L. In 12th International Coating Science and Technology Symposium (ISCST, Rochester, New York, USA, 2004).
95. Gao Y Enhanced chemical stability of VO 2 nanoparticles by the formation of SiO 2/VO 2 core/shell structures and the application to transparent and flexible VO 2-based composite foils with excellent thermochromic properties for solar heat control Energy Environ. Sci. 2012 5 6104 6110 10.1039/c2ee02803d
Gao, Y. et al. Enhanced chemical stability of VO 2 nanoparticles by the formation of SiO 2/VO 2 core/shell structures and the application to transparent and flexible VO 2-based composite foils with excellent thermochromic properties for solar heat control. Energy Environ. Sci. 5, 6104–6110 (2012).
96. Truby RL Lewis JA Printing soft matter in three dimensions Nature 2016 540 371 378 10.1038/nature21003 27974748
Truby, R. L. & Lewis, J. A. Printing soft matter in three dimensions. Nature 540, 371–378 (2016).27974748
97. Castro JO Ramesan S Rezk AR Yeo LY Continuous tuneable droplet ejection via pulsed surface acoustic wave jetting Soft Matter 2018 14 5721 5727 10.1039/C7SM02534C 29845144
Castro, J. O., Ramesan, S., Rezk, A. R. & Yeo, L. Y. Continuous tuneable droplet ejection via pulsed surface acoustic wave jetting. Soft Matter 14, 5721–5727 (2018).29845144
98. Ji H Liu D Cheng H Tao Y Large area infrared thermochromic VO2 nanoparticle films prepared by inkjet printing technology Sol. Energy Mater. Sol. Cells 2019 194 235 243 10.1016/j.solmat.2019.02.028
Ji, H., Liu, D., Cheng, H. & Tao, Y. Large area infrared thermochromic VO2 nanoparticle films prepared by inkjet printing technology. Sol. Energy Mater. Sol. Cells 194, 235–243 (2019).
99. Patil RA Devan RS Liou Y Ma Y-R Efficient electrochromic smart windows of one-dimensional pure brookite TiO2 nanoneedles Sol. Energy Mater. Sol. Cells 2016 147 240 245 10.1016/j.solmat.2015.12.024
Patil, R. A., Devan, R. S., Liou, Y. & Ma, Y.-R. Efficient electrochromic smart windows of one-dimensional pure brookite TiO2 nanoneedles. Sol. Energy Mater. Sol. Cells 147, 240–245 (2016).
100. Kerszulis JA Amb CM Dyer AL Reynolds JR Follow the yellow brick road: structural optimization of vibrant yellow-to-transmissive electrochromic conjugated polymers Macromolecules 2014 47 5462 5469 10.1021/ma501080u
Kerszulis, J. A., Amb, C. M., Dyer, A. L. & Reynolds, J. R. Follow the yellow brick road: structural optimization of vibrant yellow-to-transmissive electrochromic conjugated polymers. Macromolecules 47, 5462–5469 (2014).
101. Bera MK Mori T Yoshida T Ariga K Higuchi M Construction of coordination nanosheets based on Tris (2, 2′-bipyridine)–Iron (Fe2+) complexes as potential electrochromic materials ACS Appl. Mater. interfaces 2019 11 11893 11903 10.1021/acsami.8b22568 30817110
Bera, M. K., Mori, T., Yoshida, T., Ariga, K. & Higuchi, M. Construction of coordination nanosheets based on Tris (2, 2′-bipyridine)–Iron (Fe2+) complexes as potential electrochromic materials. ACS Appl. Mater. interfaces 11, 11893–11903 (2019).30817110
102. Qian J Ma D Xu Z Li D Wang J Electrochromic properties of hydrothermally grown Prussian blue film and device Sol. Energy Mater. Sol. Cells 2018 177 9 14 10.1016/j.solmat.2017.08.016
Qian, J., Ma, D., Xu, Z., Li, D. & Wang, J. Electrochromic properties of hydrothermally grown Prussian blue film and device. Sol. Energy Mater. Sol. Cells 177, 9–14 (2018).
103. Rosseinsky, D.R., Monk, P.M. & Mortimer, R. J. Electrochromic materials and devices (John Wiley & Sons, 2015).
104. Sang J Smart Windows with a VO2 Thin Film as a Conductive Layer for Efficient and Independent Dual-Band Modulation, ACS Appl. Electron Mater 2021 3 4882 4890
Sang, J. et al. Smart Windows with a VO2 Thin Film as a Conductive Layer for Efficient and Independent Dual-Band Modulation, ACS Appl. Electron. Mater 3, 4882–4890 (2021).
105. Benson, D. K. et al. In Advanced Sensors and Monitors for Process Industries and the Environment. (SPIE, 1999).
106. Korman, V. In Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, (SPIE, 2006).
107. Georg A Graf W Neumann R Wittwer V Mechanism of the gasochromic coloration of porous WO3 films Solid State Ion. 2000 127 319 328 10.1016/S0167-2738(99)00273-8
Georg, A., Graf, W., Neumann, R. & Wittwer, V. Mechanism of the gasochromic coloration of porous WO3 films. Solid State Ion. 127, 319–328 (2000).
108. Georg A Graf W Neumann R Wittwer V Stability of gasochromic WO3 films Sol. Energy Mater. Sol. Cells 2000 63 165 176 10.1016/S0927-0248(00)00006-4
Georg, A., Graf, W., Neumann, R. & Wittwer, V. Stability of gasochromic WO3 films. Sol. Energy Mater. Sol. Cells 63, 165–176 (2000).
109. Calvino C Neumann L Weder C Schrettl S Approaches to polymeric mechanochromic materials J. Polym. Sci. Part A: Polym. Chem. 2017 55 640 652 10.1002/pola.28445
Calvino, C., Neumann, L., Weder, C. & Schrettl, S. Approaches to polymeric mechanochromic materials. J. Polym. Sci. Part A: Polym. Chem. 55, 640–652 (2017).
110. Jiang B Liu L Gao Z Wang W A general and robust strategy for fabricating mechanoresponsive surface wrinkles with dynamic switchable transmittance Adv. Optical Mater. 2018 6 1800195 10.1002/adom.201800195
Jiang, B., Liu, L., Gao, Z. & Wang, W. A general and robust strategy for fabricating mechanoresponsive surface wrinkles with dynamic switchable transmittance. Adv. Optical Mater. 6, 1800195 (2018).
111. Shrestha M Asundi A Lau G-K Smart window based on electric unfolding of microwrinkled TiO2 nanometric films Acs Photonics 2018 5 3255 3262 10.1021/acsphotonics.8b00486
Shrestha, M., Asundi, A. & Lau, G.-K. Smart window based on electric unfolding of microwrinkled TiO2 nanometric films. Acs Photonics 5, 3255–3262 (2018).
112. Ke Y Smart windows: electro‐, thermo‐, mechano‐, photochromics, and beyond, Advanced Energy Materials 2019 9 1902066
Ke, Y. et al. Smart windows: electro‐, thermo‐, mechano‐, photochromics, and beyond, Advanced Energy. Materials 9, 1902066 (2019).
113. Ke Y Cephalopod-inspired versatile design based on plasmonic VO2 nanoparticle for energy-efficient mechano-thermochromic windows Nano Energy 2020 73 104785 10.1016/j.nanoen.2020.104785
Ke, Y. et al. Cephalopod-inspired versatile design based on plasmonic VO2 nanoparticle for energy-efficient mechano-thermochromic windows. Nano Energy 73, 104785 (2020).
114. Harada J Taira M Ogawa K Photochromism of Fulgide Crystals: From Lattice-Controlled Product Accumulation to Phase Separation Cryst. Growth Des. 2017 17 2682 2687 10.1021/acs.cgd.7b00182
Harada, J., Taira, M. & Ogawa, K. Photochromism of Fulgide Crystals: From Lattice-Controlled Product Accumulation to Phase Separation. Cryst. Growth Des. 17, 2682–2687 (2017).
115. Irie M Fukaminato T Matsuda K Kobatake S Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators Chem. Rev. 2014 114 12174 12277 10.1021/cr500249p 25514509
Irie, M., Fukaminato, T., Matsuda, K. & Kobatake, S. Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators. Chem. Rev. 114, 12174–12277 (2014).25514509
116. Xia H Xie K Zou G Advances in spiropyrans/spirooxazines and applications based on fluorescence resonance energy transfer (FRET) with fluorescent materials Molecules 2017 22 2236 10.3390/molecules22122236 29258220
Xia, H., Xie, K. & Zou, G. Advances in spiropyrans/spirooxazines and applications based on fluorescence resonance energy transfer (FRET) with fluorescent materials. Molecules 22, 2236 (2017).29258220
117. Schrauben JN Titanium and zinc oxide nanoparticles are proton-coupled electron transfer agents Science 2012 336 1298 1301 10.1126/science.1220234 22679095
Schrauben, J. N. et al. Titanium and zinc oxide nanoparticles are proton-coupled electron transfer agents. Science 336, 1298–1301 (2012).22679095
118. Sato O Optically switchable molecular solids: photoinduced spin-crossover, photochromism, and photoinduced magnetization Acc. Chem. Res. 2003 36 692 700 10.1021/ar020242z 12974652
Sato, O. Optically switchable molecular solids: photoinduced spin-crossover, photochromism, and photoinduced magnetization. Acc. Chem. Res. 36, 692–700 (2003).12974652
119. Pardo R Zayat M Levy D Photochromic organic–inorganic hybrid materials Chem. Soc. Rev. 2011 40 672 687 10.1039/c0cs00065e 21229130
Pardo, R., Zayat, M. & Levy, D. Photochromic organic–inorganic hybrid materials. Chem. Soc. Rev. 40, 672–687 (2011).21229130
120. Minkin VI Photo-, thermo-, solvato-, and electrochromic spiroheterocyclic compounds Chem. Rev. 2004 104 2751 2776 10.1021/cr020088u 15137806
Minkin, V. I. Photo-, thermo-, solvato-, and electrochromic spiroheterocyclic compounds. Chem. Rev. 104, 2751–2776 (2004).15137806
121. Zhao X VO2-based composite films with exemplary thermochromic and photochromic performance J. Appl. Phys. 2020 128 185107 10.1063/5.0015382
Zhao, X. et al. VO2-based composite films with exemplary thermochromic and photochromic performance. J. Appl. Phys. 128, 185107 (2020).
122. Fu, F. & Hu, L. In Advanced High Strength Natural Fibre Composites in Construction, (eds Fan, M., and Fu, F.) 405–423 (Woodhead Publishing, 2017)
123. Zhang Y Perovskite thermochromic smart window: Advanced optical properties and low transition temperature Appl. Energy 2019 254 113690 10.1016/j.apenergy.2019.113690
Zhang, Y. et al. Perovskite thermochromic smart window: Advanced optical properties and low transition temperature. Appl. Energy 254, 113690 (2019).
124. Saito M A cross-cultural study on color preference in three asian cities comparison between Tokyo, Taipei and Tianjin Jpn. Psychol. Res. 1994 36 219 232 10.4992/psycholres1954.36.219
Saito, M. A cross-cultural study on color preference in three asian cities comparison between Tokyo, Taipei and Tianjin. Jpn. Psychol. Res. 36, 219–232 (1994).
125. Mofarah MY Tahmtan ZS Dadashi MT Banihashemian SH How color affects marketing, Arab. J. Bus Manag. Rev. (Oman Chap.) 2013 34 1 9
Mofarah, M. Y., Tahmtan, Z. S., Dadashi, M. T. & Banihashemian, S. H. How color affects marketing, Arab. J. Bus. Manag. Rev. (Oman Chap.) 34, 1–9 (2013).
126. Lu C Nanoparticle-free and self-healing amphiphobic membrane for anti-surfactant-wetting membrane distillation J. Environ. Sci. 2021 100 298 305 10.1016/j.jes.2020.04.044
Lu, C. et al. Nanoparticle-free and self-healing amphiphobic membrane for anti-surfactant-wetting membrane distillation. J. Environ. Sci. 100, 298–305 (2021).
127. Su C Robust superhydrophobic membrane for membrane distillation with excellent scaling resistance Environ. Sci. Technol. 2019 53 11801 11809 10.1021/acs.est.9b04362 31535854
Su, C. et al. Robust superhydrophobic membrane for membrane distillation with excellent scaling resistance. Environ. Sci. Technol. 53, 11801–11809 (2019).31535854
128. Lin K-T Highly efficient flexible structured metasurface by roll-to-roll printing for diurnal radiative cooling eLight 2023 3 22 10.1186/s43593-023-00053-3
Lin, K.-T. et al. Highly efficient flexible structured metasurface by roll-to-roll printing for diurnal radiative cooling. eLight 3, 22 (2023).
129. Zhu Y Night-time radiative warming using the atmosphere Light Sci. Appl. 2023 12 268 10.1038/s41377-023-01315-y 37949868
Zhu, Y. et al. Night-time radiative warming using the atmosphere. Light Sci. Appl. 12, 268 (2023).37949868
130. Qin B Zhu Y Zhou Y Qiu M Li Q Whole-infrared-band camouflage with dual-band radiative heat dissipation Light Sci. Appl. 2023 12 246 10.1038/s41377-023-01287-z 37794015
Qin, B., Zhu, Y., Zhou, Y., Qiu, M. & Li, Q. Whole-infrared-band camouflage with dual-band radiative heat dissipation. Light Sci. Appl. 12, 246 (2023).37794015
131. Liao Y Fan YL Lei DY Thermally tunable binary-phase VO2 metasurfaces for switchable holography and digital encryption Nanophotonics 2024 13 1109 1117 10.1515/nanoph-2023-0824
Liao, Y., Fan, Y. L. & Lei, D. Y. Thermally tunable binary-phase VO2 metasurfaces for switchable holography and digital encryption. Nanophotonics 13, 1109–1117 (2024).
132. Pei R The valence conversion mechanism for Mo‐doped VO2 films with enhanced thermochromic properties Z. Anorg. Allg. Chem. 2022 648 e202200132 10.1002/zaac.202200132
Pei, R. et al. The valence conversion mechanism for Mo‐doped VO2 films with enhanced thermochromic properties. Z. Anorg. Allg. Chem. 648, e202200132 (2022).
133. Wu J Regulation of phase transition temperature and preparation for doping-VO2 smart thermal control films J. Appl. Phys. 2022 131 085101 10.1063/5.0054066
Wu, J. et al. Regulation of phase transition temperature and preparation for doping-VO2 smart thermal control films. J. Appl. Phys. 131, 085101 (2022).
134. Ersundu AE Çelikbilek Ersundu M Doğan E Güven MB A comparative investigation on thermal, structural and optical properties of W and Nb-doped VO2-based thermochromic thin films Thin Solid Films 2020 700 137919 10.1016/j.tsf.2020.137919
Ersundu, A. E., Çelikbilek Ersundu, M., Doğan, E. & Güven, M. B. A comparative investigation on thermal, structural and optical properties of W and Nb-doped VO2-based thermochromic thin films. Thin Solid Films 700, 137919 (2020).
135. Zhao C Nb-doped VO2 single crystal microtube arrays Vacuum 2022 203 111309 10.1016/j.vacuum.2022.111309
Zhao, C. et al. Nb-doped VO2 single crystal microtube arrays. Vacuum 203, 111309 (2022).
136. Dietrich MK Kuhl F Polity A Klar PJ Optimizing thermochromic VO2 by co-doping with W and Sr for smart window applications Appl. Phys. Lett. 2017 110 141907 10.1063/1.4979700
Dietrich, M. K., Kuhl, F., Polity, A. & Klar, P. J. Optimizing thermochromic VO2 by co-doping with W and Sr for smart window applications. Appl. Phys. Lett. 110, 141907 (2017).
137. Kuhl F Embedding Quaternary V1–x–ySrxWyO2 into Multilayer Systems to Enhance Its Thermochromic Properties for Smart Glass Applications ACS Appl. Electron. Mater. 2022 4 513 520 10.1021/acsaelm.1c01115
Kuhl, F. et al. Embedding Quaternary V1–x–ySrxWyO2 into Multilayer Systems to Enhance Its Thermochromic Properties for Smart Glass Applications. ACS Appl. Electron. Mater. 4, 513–520 (2022).
138. Guo H Wang Y Jain A Fu H Chen F Preparation of W/Zr co-doped VO2 with improved microstructural and thermochromic properties J. Alloy. Compd. 2021 878 160352 10.1016/j.jallcom.2021.160352
Guo, H., Wang, Y., Jain, A., Fu, H. & Chen, F. Preparation of W/Zr co-doped VO2 with improved microstructural and thermochromic properties. J. Alloy. Compd. 878, 160352 (2021).
139. Haji HF Zr and W Co-doped VO2 thin films with improved luminous transmittance and transition temperature J. Mater. Sci.: Mater. Electron. 2023 34 2006
Haji, H. F. et al. Zr and W Co-doped VO2 thin films with improved luminous transmittance and transition temperature. J. Mater. Sci.: Mater. Electron. 34, 2006 (2023).
140. Lv W Huang D Chen Y Qiu Q Luo Z Synthesis and characterization of Mo–W co-doped VO2 (R) nano-powders by the microwave-assisted hydrothermal method Ceram. Int. 2014 40 12661 12668 10.1016/j.ceramint.2014.04.113
Lv, W., Huang, D., Chen, Y., Qiu, Q. & Luo, Z. Synthesis and characterization of Mo–W co-doped VO2 (R) nano-powders by the microwave-assisted hydrothermal method. Ceram. Int. 40, 12661–12668 (2014).
141. Jiazhen Y Yue Z Wanxia H Mingjin T Effect of Mo-W Co-doping on semiconductor-metal phase transition temperature of vanadium dioxide film Thin Solid Films 2008 516 8554 8558 10.1016/j.tsf.2008.05.021
Jiazhen, Y., Yue, Z., Wanxia, H. & Mingjin, T. Effect of Mo-W Co-doping on semiconductor-metal phase transition temperature of vanadium dioxide film. Thin Solid Films 516, 8554–8558 (2008).
142. Zhao Z Sn–W Co-doping Improves Thermochromic Performance of VO2 Films for Smart Windows ACS Appl. Energy Mater. 2020 3 9972 9979 10.1021/acsaem.0c01651
Zhao, Z. et al. Sn–W Co-doping Improves Thermochromic Performance of VO2 Films for Smart Windows. ACS Appl. Energy Mater. 3, 9972–9979 (2020).
143. Li P Enhancing thermochromic properties of VO2 amorphous films on glass substrates by Sn-W co-doping Infrared Phys. Technol. 2023 134 104871 10.1016/j.infrared.2023.104871
Li, P. et al. Enhancing thermochromic properties of VO2 amorphous films on glass substrates by Sn-W co-doping. Infrared Phys. Technol. 134, 104871 (2023).
144. Gao Y Phase and shape controlled VO 2 nanostructures by antimony doping Energy Environ. Sci. 2012 5 8708 8715 10.1039/c2ee22290f
Gao, Y. et al. Phase and shape controlled VO 2 nanostructures by antimony doping. Energy Environ. Sci. 5, 8708–8715 (2012).
145. Cui Y First-principles study of phase-transition temperature and optical properties of alkaline earth metal (Be, Mg, Ca, Sr or Ba)-doped VO2 Ceram. Int. 2018 44 20814 20820 10.1016/j.ceramint.2018.08.084
Cui, Y. et al. First-principles study of phase-transition temperature and optical properties of alkaline earth metal (Be, Mg, Ca, Sr or Ba)-doped VO2. Ceram. Int. 44, 20814–20820 (2018).
146. Zou Z Thermochromic, threshold switching, and optical properties of Cr-doped VO2 thin films, J. Alloy. Compd. 2019 806 310 315 10.1016/j.jallcom.2019.07.264
Zou, Z. et al. Thermochromic, threshold switching, and optical properties of Cr-doped VO2. thin films, J. Alloy. Compd. 806, 310–315 (2019).
147. Suleiman AO Mansouri S Margot J Chaker M Tuning VO2 phase stability by a combined effect of Cr doping and oxygen pressure Appl. Surf. Sci. 2022 571 151267 10.1016/j.apsusc.2021.151267
Suleiman, A. O., Mansouri, S., Margot, J. & Chaker, M. Tuning VO2 phase stability by a combined effect of Cr doping and oxygen pressure. Appl. Surf. Sci. 571, 151267 (2022).
148. Gu D Zheng H Ma Y Xu S Zhou X A highly-efficient approach for reducing phase transition temperature of VO2 polycrystalline thin films through Ru4+-doping J. Alloy. Compd. 2019 790 602 609 10.1016/j.jallcom.2019.03.214
Gu, D., Zheng, H., Ma, Y., Xu, S. & Zhou, X. A highly-efficient approach for reducing phase transition temperature of VO2 polycrystalline thin films through Ru4+-doping. J. Alloy. Compd. 790, 602–609 (2019).
149. GGui, X. & Cava, R. J. Metal-insulator transition and anomalous lattice parameters changes in Ru-doped ${\mathrm{VO}}_{2}$. Phys. Rev. Mater. 6, 075005 (2022).
150. Qi J Ning G Lin Y Synthesis, characterization, and thermodynamic parameters of vanadium dioxide Mater. Res. Bull. 2008 43 2300 2307 10.1016/j.materresbull.2007.08.016
Qi, J., Ning, G. & Lin, Y. Synthesis, characterization, and thermodynamic parameters of vanadium dioxide. Mater. Res. Bull. 43, 2300–2307 (2008).
151. Ye J Preparation, characterization and properties of thermochromic tungsten-doped vanadium dioxide by thermal reduction and annealing J. Alloy. Compd. 2010 504 503 507 10.1016/j.jallcom.2010.05.152
Ye, J. et al. Preparation, characterization and properties of thermochromic tungsten-doped vanadium dioxide by thermal reduction and annealing. J. Alloy. Compd. 504, 503–507 (2010).
152. Zhang H A cost-effective method to fabricate VO2 (M) nanoparticles and films with excellent thermochromic properties J. Alloy. Compd. 2015 636 106 112 10.1016/j.jallcom.2015.01.277
Zhang, H. et al. A cost-effective method to fabricate VO2 (M) nanoparticles and films with excellent thermochromic properties. J. Alloy. Compd. 636, 106–112 (2015).
153. Jung D Kim U Cho W Fabrication of pure monoclinic VO2 nanoporous nanorods via a mild pyrolysis process Ceram. Int. 2018 44 6973 6979 10.1016/j.ceramint.2018.01.130
Jung, D., Kim, U. & Cho, W. Fabrication of pure monoclinic VO2 nanoporous nanorods via a mild pyrolysis process. Ceram. Int. 44, 6973–6979 (2018).
154. Billik P Synthesis and transport properties of nanostructured VO2 by mechanochemical processing Meas. Sci. Rev. 2011 11 29 10.2478/v10048-011-0001-6
Billik, P. et al. Synthesis and transport properties of nanostructured VO2 by mechanochemical processing. Meas. Sci. Rev. 11, 29 (2011).
155. Wang C One-step ball milling synthesis of VO2 (M) nanoparticles with exemplary thermochromic performance SN Appl. Sci. 2021 3 436 10.1007/s42452-021-04154-x
Wang, C. et al. One-step ball milling synthesis of VO2 (M) nanoparticles with exemplary thermochromic performance. SN Appl. Sci. 3, 436 (2021).
156. Rama N Ramachandra Rao MS Synthesis and study of electrical and magnetic properties of vanadium oxide micro and nanosized rods grown using pulsed laser deposition technique Solid State Commun. 2010 150 1041 1044 10.1016/j.ssc.2010.01.049
Rama, N. & Ramachandra Rao, M. S. Synthesis and study of electrical and magnetic properties of vanadium oxide micro and nanosized rods grown using pulsed laser deposition technique. Solid State Commun. 150, 1041–1044 (2010).
157. Florian Aguilar, C. A. Fabricación de películas delgadas de óxido de vandio por el método sputtering como material temocrómico, (2015).
158. Kim MH Growth of Metal Oxide Nanowires from Supercooled Liquid Nanodroplets Nano Lett. 2009 9 4138 4146 10.1021/nl902357q 19780585
Kim, M. H. et al. Growth of Metal Oxide Nanowires from Supercooled Liquid Nanodroplets. Nano Lett. 9, 4138–4146 (2009).19780585
159. Devthade V Lee S Synthesis of vanadium dioxide thin films and nanostructures J. Appl. Phys. 2020 128 231101 10.1063/5.0027690
Devthade, V. & Lee, S. Synthesis of vanadium dioxide thin films and nanostructures. J. Appl. Phys. 128, 231101 (2020).
160. Li Y Jiang P Xiang W Ran F Cao W A novel inorganic precipitation–peptization method for VO2 sol and VO2 nanoparticles preparation: Synthesis, characterization and mechanism J. colloid interface Sci. 2016 462 42 47 10.1016/j.jcis.2015.09.056 26433476
Li, Y., Jiang, P., Xiang, W., Ran, F. & Cao, W. A novel inorganic precipitation–peptization method for VO2 sol and VO2 nanoparticles preparation: Synthesis, characterization and mechanism. J. colloid interface Sci. 462, 42–47 (2016).26433476
161. Chen H-K Hung H-C Yang TCK Wang S-F The preparation and characterization of transparent nano-sized thermochromic VO2–SiO2 films from the sol–gel process J. Non-Crystalline Solids 2004 347 138 143 10.1016/j.jnoncrysol.2004.07.065
Chen, H.-K., Hung, H.-C., Yang, T. C. K. & Wang, S.-F. The preparation and characterization of transparent nano-sized thermochromic VO2–SiO2 films from the sol–gel process. J. Non-Crystalline Solids 347, 138–143 (2004).
162. Cao C Gao Y Luo H Pure single-crystal rutile vanadium dioxide powders: Synthesis, mechanism and phase-transformation property, The J. Phys. Chem. C. 2008 112 18810 18814 10.1021/jp8073688
Cao, C., Gao, Y. & Luo, H. Pure single-crystal rutile vanadium dioxide powders: Synthesis, mechanism and phase-transformation property, The. J. Phys. Chem. C. 112, 18810–18814 (2008).
163. Pham V-H Microstructure and luminescence of VO2 (B) nanoparticle synthesis by hydrothermal method Green. Process. Synth. 2019 8 802 807 10.1515/gps-2019-0049
Pham, V.-H. et al. Microstructure and luminescence of VO2 (B) nanoparticle synthesis by hydrothermal method. Green. Process. Synth. 8, 802–807 (2019).
164. Whittaker L Velazquez JM Banerjee S A VO-seeded approach for the growth of star-shaped VO 2 and V 2 O 5 nanocrystals: facile synthesis, structural characterization, and elucidation of electronic structure CrystEngComm 2011 13 5328 5336 10.1039/c0ce00832j
Whittaker, L., Velazquez, J. M. & Banerjee, S. A VO-seeded approach for the growth of star-shaped VO 2 and V 2 O 5 nanocrystals: facile synthesis, structural characterization, and elucidation of electronic structure. CrystEngComm 13, 5328–5336 (2011).
165. Zhong L TiO 2 seed-assisted growth of VO 2 (M) films and thermochromic performance CrystEngComm. 2016 18 7140 7146 10.1039/C6CE01658H
Zhong, L. et al. TiO 2 seed-assisted growth of VO 2 (M) films and thermochromic performance. CrystEngComm. 18, 7140–7146 (2016).
166. Wu H Direct synthesis of vanadium oxide nanopowders by the combustion approach Chem. Phys. Lett. 2018 706 7 13 10.1016/j.cplett.2018.05.064
Wu, H. et al. Direct synthesis of vanadium oxide nanopowders by the combustion approach. Chem. Phys. Lett. 706, 7–13 (2018).
167. Cao Z A simple and low-cost combustion method to prepare monoclinic VO2 with superior thermochromic properties Sci. Rep. 2016 6 39154 10.1038/srep39154 27976748
Cao, Z. et al. A simple and low-cost combustion method to prepare monoclinic VO2 with superior thermochromic properties. Sci. Rep. 6, 39154 (2016).27976748
168. Cao, X., Jin, P. & Luo, H. In Nanotechnology in Eco-Efficient Construction. 503–524 (Elsevier, 2019)
169. Whittaker L Patridge CJ Banerjee S Microscopic and nanoscale perspective of the metal− insulator phase transitions of VO2: some new twists to an old tale J. Phys. Chem. Lett. 2011 2 745 758 10.1021/jz101640n
Whittaker, L., Patridge, C. J. & Banerjee, S. Microscopic and nanoscale perspective of the metal− insulator phase transitions of VO2: some new twists to an old tale. J. Phys. Chem. Lett. 2, 745–758 (2011).
170. He X Orbital change manipulation metal–insulator transition temperature in W-doped VO 2 Phys. Chem. Chem. Phys. 2015 17 11638 11646 10.1039/C4CP04889J 25866849
He, X. et al. Orbital change manipulation metal–insulator transition temperature in W-doped VO 2. Phys. Chem. Chem. Phys. 17, 11638–11646 (2015).25866849
171. Ji H Liu D Zhang C Cheng H VO2/ZnS core-shell nanoparticle for the adaptive infrared camouflage application with modified color and enhanced oxidation resistance Sol. Energy Mater. Sol. Cells 2018 176 1 8 10.1016/j.solmat.2017.11.037
Ji, H., Liu, D., Zhang, C. & Cheng, H. VO2/ZnS core-shell nanoparticle for the adaptive infrared camouflage application with modified color and enhanced oxidation resistance. Sol. Energy Mater. Sol. Cells 176, 1–8 (2018).
172. Kim Y High-throughput roll-to-roll fabrication of flexible thermochromic coatings for smart windows with vo 2 nanoparticles J. Mater. Chem. C. 2018 6 3451 3458 10.1039/C7TC05876D
Kim, Y. et al. High-throughput roll-to-roll fabrication of flexible thermochromic coatings for smart windows with vo 2 nanoparticles. J. Mater. Chem. C. 6, 3451–3458 (2018).
173. Chen Y High performance and enhanced durability of thermochromic films using VO2@ ZnO core–shell nanoparticles ACS Appl. Mater. interfaces 2017 9 27784 27791 10.1021/acsami.7b08889 28758388
Chen, Y. et al. High performance and enhanced durability of thermochromic films using VO2@ ZnO core–shell nanoparticles. ACS Appl. Mater. interfaces 9, 27784–27791 (2017).28758388
174. Zhang Q Sando D Nagarajan V Chemical route derived bismuth ferrite thin films and nanomaterials J. Mater. Chem. C. 2016 4 4092 4124 10.1039/C6TC00243A
Zhang, Q., Sando, D. & Nagarajan, V. Chemical route derived bismuth ferrite thin films and nanomaterials. J. Mater. Chem. C. 4, 4092–4124 (2016).
175. Pujahari, R. In Energy Materials. 27–60 (Elsevier, 2021)
176. SpinCoater, WHAT IS SPIN COATING? https://www.spincoater.com/what-is-spin-coating.php. Accessed 2019).
177. Siemann, U. In Scattering methods and the properties of polymer materials. 1–14 (Springer, 2005)
178. Jabari E 2D printing of graphene: a review 2D Mater. 2019 6 042004 10.1088/2053-1583/ab29b2
Jabari, E. et al. 2D printing of graphene: a review. 2D Mater. 6, 042004 (2019).
179. Sheng M Wang W Li L Zhang L Fu S All-in-one wearable electronics design: Smart electrochromic liquid-crystal-clad fibers without external electrodes Colloids Surf. A: Physicochemical Eng. Asp. 2021 630 127535 10.1016/j.colsurfa.2021.127535
Sheng, M., Wang, W., Li, L., Zhang, L. & Fu, S. All-in-one wearable electronics design: Smart electrochromic liquid-crystal-clad fibers without external electrodes. Colloids Surf. A: Physicochemical Eng. Asp. 630, 127535 (2021).
180. Gao C A review on WO3 gasochromic film: Mechanism, preparation and properties Int. J. Hydrogen Energy 2022 48 2442 2465 10.1016/j.ijhydene.2022.10.100
Gao, C. et al. A review on WO3 gasochromic film: Mechanism, preparation and properties. Int. J. Hydrogen Energy 48, 2442–2465 (2022).
181. Imato K Mechanochromic dynamic covalent elastomers: quantitative stress evaluation and autonomous recovery ACS Macro Lett. 2015 4 1307 1311 10.1021/acsmacrolett.5b00717 35614834
Imato, K. et al. Mechanochromic dynamic covalent elastomers: quantitative stress evaluation and autonomous recovery. ACS Macro Lett. 4, 1307–1311 (2015).35614834
