Composite material and preparation thereof

Abstract

A composite material comprising: a first layer of thermochromic perovskite; a second layer of an anti-reflective material comprising an organic or inorganic polymer deposited on the first layer; and a third layer of hydrophobic material deposited on the second layer. A method for preparing the composite material is also presented.

Description

Technical Field

[0001] The present invention relates to a composite material, such as particularly, but not exclusively, a thermochromic composite material comprising a thermochromic perovskite and a layer of material arranged to protect the thermochromic perovskite from contact with excess water; and a method for preparing the composite material. Background Art

[0002] As a result of rapid urbanization, modern buildings are responsible for more than 40% of global primary energy consumption, thus contributing to more than 30% of urban greenhouse gas emissions. With stricter aesthetic requirements for buildings, extremely high window-to-wall ratios have become a feature of modern architecture. However, the high transmittance that cannot be changed under strong sunlight and the high U-value of glass make windows the main source of heat loss / gain in all building envelopes. Therefore, energy-saving smart windows with dynamically adjustable solar transmittance have attracted increasing attention recently to balance the goal of less energy consumption and the aesthetic demand for more glass windows.

[0003] Thermochromic smart windows are one of the most widely studied smart windows, which usually use the thermochromism of metal halide perovskites to manage the energy use and temperature of buildings. The color conversion of thermochromic perovskites (T-perovskites) usually depends on the dissociation of H2O from the T-perovskite layer and the recombination to the T-perovskite layer, such as through the following chemical reaction:

[0004]

[0005] Where MA is CH3NH3 + , and X is a halide anion. That is, on the one hand, water is essential for inducing the thermochromic effect of T-perovskite. On the other hand, water can degrade / corrode T-perovskite, especially when T-perovskite is continuously subjected to a high humidity environment or water droplets. In particular, excess water may cause ultra-high light fog and blurred vision through T-perovskite windows, since the presence of excess MAX will affect the crystallization process during color conversion. In addition, excess water can also act as a solvent to dissolve the lead content in T-perovskite during the thermochromic process, resulting in lead leakage, threatening the environment and public health.

[0006] Although there are reports on circumventing the above problems, these methods usually cause another problem or have to sacrifice the optical and conversion properties of T-perovskites. For example, a common way to protect T-perovskites may be to seal them in double-glazed windows. However, this method requires sealed packaging, which makes the assembly of the window difficult and there is a risk of leakage in long-term use. Alternatively, the T-perovskite can be protected by covering it with a protective layer, however this method may result in insufficient water vapor supplied to the T-perovskite to achieve color conversion. In another method, it can reduce the size of the T-perovskite to 2D. However, 2D T-perovskites generally suffer from high T c (>60℃) and long transition time (t>6 hours), which is similar to its T c Their 3D counterparts with t values ​​close to room temperature and t values ​​of only a few minutes are essentially incomparable. Therefore, the development of durable and waterproof T-perovskite windows with excellent optical and transition properties remains a challenge.

[0007] The present invention seeks to obviate or at least mitigate this disadvantage by providing a new or otherwise improved composite material, in particular, a composite material comprising a thermochromic perovskite and a layer of material arranged to protect the thermochromic perovskite from excessive water contact in window applications. Summary of the invention

[0008] In a first aspect of the present invention, a composite material is provided, comprising: a first layer of a thermochromic perovskite; a second layer of an antireflective material comprising an organic or inorganic polymer deposited on the first layer; and a third layer of a hydrophobic material deposited on the second layer.

[0009] In an optional embodiment, the first layer comprises a substrate made of glass or PET on which a thermochromic perovskite layer is deposited. Optionally, the thermochromic perovskite comprises a halide perovskite-based compound having the general formula A4BX6·2H2O, wherein A is a monovalent organic cation, B is a divalent cation, and X is one or more of a halide. Optionally, A4BX6·2H2O reversibly changes to ABX3 in response to a change in temperature. Optionally, A is selected from CH3NH3 + and CH(NH2)2 + Any one of; B is selected from Pb 2+ Sn 2+ ,Ge 2+ Mg 2+ and Ca 2+ Any one of; and X is selected from I - Br - , Cl - and any combination thereof.

[0010] In an optional embodiment, the halide perovskite-based compound has the general formula (CH3NH3)4PbI 6-x- y Br x Cl y 2H2O, wherein x and y are each 0 or a positive integer, and x+y≤6.

[0011] In one embodiment of the present invention, the halide perovskite-based compound is (CH3NH3)4PbI 6- y Cl y · 2H2O, wherein y is 0 to 6. Optionally, the thermochromic perovskite layer has a thickness of 1.6 μm.

[0012] Optionally, the anti-reflective material has a refractive index between air and thermochromic perovskite. Optionally, the anti-reflective material comprises any one of the following: epoxy resin, poly(methyl methacrylate), polyvinyl pyrrolidone, poly(vinyl alcohol), polydimethylsiloxane, poly(acrylic acid), poly(acrylamide), poly(aniline), poly(ethylene oxide), poly(N-acryloxysuccinimide), poly(N-isopropylacrylamide), poly(N-isopropylmethacrylamide), poly(N-vinylcaprolactam), poly(N-vinylpyrrolidone), poly(methacrylic acid), poly(styrenesulfonic acid), polyurethane, poly(propylene oxide), perhydropolysilazane, or a combination thereof.

[0013] In one embodiment of the present invention, the anti-reflective material is perhydropolysilazane. Optionally, the perhydropolysilazane is in the form of a SiO x / SiON x In the form of a homogeneous inorganic membrane.

[0014] Optionally, the hydrophobic material comprises a super hydrophobic layer. In one embodiment of the present invention, the super hydrophobic layer comprises a layer of a fluorinated nano coating. Optionally, the layer of the fluorinated nano coating is any one of fluorinated SiO2, fluorinated TiO2 and fluorinated ZnO.

[0015] In a second aspect of the present invention, a method for preparing a composite material according to the first aspect is provided, the method comprising the following steps: coating a thermochromic perovskite on a substrate made of glass or PET to form a first layer; coating an anti-reflective material on the first layer to form a second layer; and coating silica-based nanoparticles on the second layer to form a third layer.

[0016] Optionally, the thermochromic perovskite is subjected to annealing after it is coated on the substrate to form the first layer.

[0017] In one embodiment of the present invention, the thermochromic perovskite is (CH3NH3)4PbI 6-y Cl y · A 2H2O based halide perovskite precursor, wherein y is 0 to 6, prepared by mixing CH3NH3I and PbCl2 at a molar ratio of about 6.5: 1. Optionally, annealed at about 100°C for about 1 hour.

[0018] Optionally, the antireflective material comprises a homogeneous inorganic material that is solidified by spin coating or doctor blade coating on the first layer followed by curing.

[0019] In one embodiment of the present invention, the homogeneous inorganic material is prepared from perhydropolysilazane dissolved in dibutyl ether.

[0020] Optionally, the first layer, the second layer and the third layer are formed by a solution-based coating method. In an optional embodiment, the first layer and the second layer are formed by spin coating. In another optional embodiment, the third layer is formed by ultrasonic spraying.

[0021] In one embodiment of the present invention, the silicon dioxide-based nanoparticles are SiO2 nanoparticles, such as fluorinated SiO2 nanoparticles, which are deposited on the second layer by ultrasonic spraying by simultaneously applying a solution of SiO2 nanoparticles and atomizing a solvent in the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

[0023] Figure 1 is a schematic diagram illustrating a composite material according to one embodiment of the present invention;

[0024] Figure 2 Transmittance spectra from FDTD simulations and experiments are shown to verify the FDTD model. This figure also shows that the transmittance of the PHPS-coated T-perovskite window (PTPW) is higher than that of the pristine T-perovskite window (TPW) in both simulation and experimental results;

[0025] Figure 3 is a schematic diagram illustrating the fabrication process of the mask-inspired thermochromic perovskite smart window (MTPW);

[0026] Figure 4A is a cross-sectional SEM image of T-perovskite coated on glass;

[0027] Figure 4B is a cross-sectional SEM image of PHPS coated on T-perovskite;

[0028] Figure 5 shows the EDS analysis of the PHPS membrane;

[0029] Figure 6 shows the FTIR spectrum of PHPS during the curing process;

[0030] Figure 7 Photographs of the MTPW in its cold and hot states are shown;

[0031] Figure 8 H-MAIPbI 3-x Cl x (MA4PbI of the present invention 6-x Cl x 2H2O or (CH3NH3)4PbI 6-y Cl y ·The complex refractive index of 2H2O) in cold and hot states;

[0032] Fig. 9 is a schematic diagram illustrating light transmission through a rough surface;

[0033] Fig. 10A is a schematic diagram illustrating vacuum assisted deposition of a coating;

[0034] Fig. 10B Shows an SEM image of SiO2 sputtered on T-perovskite (left) and a photograph of T-perovskite after magnetron sputtering (right);

[0035] Fig.11 The transmittance spectra of glass and PHPS-coated glass are shown, which show the high transparency of the PHPS coating. The thickness of the PHPS coating is about 1.8 μm;

[0036] Fig.12 is a schematic diagram illustrating solution-based coating;

[0037] Fig.13 The contact angle of PHPS coated on glass is shown;

[0038] Fig.14 The transmittance spectra of TPW and MTPW, and the AM1.5G solar spectrum are shown;

[0039] Fig.15 is a schematic diagram illustrating specular transmitted light and diffuse transmitted light;

[0040] Fig.16 Photos of TPW and MTPW are shown, comparing their optical haze;

[0041] Fig.17The optical haze of TPW, PTPW and MTPW in the wavelength range of 300-800 nm is shown;

[0042] Fig.18 SEM images, 3D optical surface profiles, and roughness of pristine TPW, PTPW, and MTPW are shown;

[0043] Fig.19 is a schematic diagram illustrating the propagation of light through a rough surface;

[0044] Fig. 20 is a schematic diagram illustrating the FDTD model used to simulate light transmission, reflection, and propagation direction;

[0045] Fig.21 The light propagation process at the air / window interface of an ideal smooth TPW, a rough TPW, and a PTPW is shown;

[0046] Fig. 22 The stimulated reflectivity of TPW and PTPW is shown;

[0047] Fig.23 The angular distribution of scattered light in the transmission and reflection fields of the TPW is shown;

[0048] Fig.24 The angular distribution of scattered light in the transmission and reflection fields of the PTPW is shown;

[0049] Fig.25 shows the FDTD simulation model used to calculate the scattering efficiency of SiO2 nanoparticles;

[0050] Fig.26 The scattering efficiency of SiO2 nanoparticles of different sizes is shown;

[0051] Fig. 27 is the TEM image of SiO2 nanoparticles in the top layer of MTPW;

[0052] Fig.28 A comparison of the transmittance spectra of PTPW and MTPW is shown to verify that SiO2 nanoparticles do not impair transparency;

[0053] Fig.29 The transmittance of MTPW and TPW at 550 nm versus temperature is shown, which shows the transition process when the temperature changes;

[0054] Fig.30 The transition times of MTPW and original TPW are shown;

[0055] Fig.31A Images showing time-dependent contact angle measurements of TPW, PTPW, and MTPW;

[0056] Fig.31B is a graph of contact angle versus time showing superhydrophobic, hydrophobic, and hydrophilic regions, and the corresponding Fig.31A Time-dependent contact angle measurement results of TPW, PTPW and MTPW.

[0057] Fig.32 is an image showing that the surface of the original TPW is rapidly damaged by a water droplet dropped thereon;

[0058] Fig.33 The SEM top views of the surface morphologies obtained by spraying SiO2 nanoparticles at different cycles and their corresponding contact angles are shown;

[0059] Fig.34 The relationship between the water contact angle of MTPW and the spraying cycle of SiO2 nanoparticles during the manufacturing process is shown;

[0060] Fig.35 The superhydrophobicity of MTPW is shown. In both cold and hot states, the falling water droplets are ejected from MTPW.

[0061] Fig.36A The optical performance (τ lum,热 , τ lum,冷 and Δτ sol );

[0062] Fig.36B The optical performance (τ lum,热 , τ lum,冷 and Δτ sol );

[0063] Fig.37A The optical properties (τ lum,热 , τ lum,冷 and Δτ sol );

[0064] Fig.37B The optical performance (τ lum,热 , τ lum,冷 and Δτ sol );

[0065] Fig.38A shows the Δτ of TPW and MTPW in the surrounding environment sol The decay rate of

[0066] Fig.38BThe Δτ of TPW and MTPW in a wet heat environment is shown sol The decay rate of

[0067] Fig.39A The immersion of the original TPW and MTPW in water is shown;

[0068] Fig.39B The XRD pattern of the pristine T-perovskite film immersed in water is shown. The main peaks observed are consistent with those of PbI2;

[0069] Fig.39C Shows the corresponding Fig.39A Pb concentrations in immersion water of original TPW and MTPW;

[0070] Fig.40A shows photographs of the flexible MTPW film in cold and hot states;

[0071] Fig.40B It is a photo of commercial energy-saving window film;

[0072] Fig.40C The transmittance spectra of commercial window films and MTPW films are shown;

[0073] Fig.41 is a schematic diagram illustrating the locations of New York, Philadelphia, Washington, Atlanta, and Orlando and the building models used in the EnergyPlus simulation;

[0074] Fig.42 is a table summarizing the information of the building used in the EnergyPlus simulation;

[0075] Fig.43 is a schematic diagram illustrating the window structures (ordinary windows, commercial window films attached to windows, and MTPW window films attached to windows) in the EnergyPlus simulation;

[0076] Fig.44 is a table summarizing the optical information of the windows used in the EnergyPlus simulation;

[0077] Fig.45 is a table summarizing climate information for U.S. cities used in EnergyPlus simulations;

[0078] Fig.46 Shows the energy savings gained over a year by using MTPW and commercial window films compared to normal windows;

[0079] Fig.47 Shows the energy consumption of buildings in New York using conventional windows, MTPW films, and commercial window films;

[0080] Fig.48 shows monthly energy consumption and savings for Philadelphia;

[0081] Fig.49 Shows the energy consumption when using regular windows, MTPW film, and commercial window film in Philadelphia;

[0082] Fig.50 shows the energy consumption when using conventional windows, MTPW film, and commercial window film in Orlando; and

[0083] Fig.51 Monthly energy consumption and savings for Orlando are shown. DETAILED DESCRIPTION

[0084] As used herein, the forms "a", "an" and "the" are intended to include both the singular and the plural forms, unless the context clearly indicates otherwise.

[0085] The words "example" or "exemplary" used in the present invention are intended to serve as examples, instances or illustrations. Any aspect or design described as "exemplary" in this disclosure is not necessarily to be construed as being more preferred or advantageous than other aspects or designs. On the contrary, the use of the words "example" or "exemplary" is intended to present concepts in a concrete way. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise indicated or clear from the context, "X employs A or B" is intended to mean any natural inclusive arrangement in the natural inclusive arrangement. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" is satisfied under any of the aforementioned examples.

[0086] Without intending to be limited by theory, the inventors through their own research, trials and experiments have designed a composite material, particularly a thermochromic composite material, which has significant haze reduction, enhanced durability / lifetime under ambient humidity conditions (e.g., at ambient temperature with about 60% humidity) and reduced lead leakage. The thermochromic composite material is designed in the following manner: a material layer comprising an anti-reflective material and a hydrophobic material is employed on the thermochromic perovskite, which will reduce light scattering on the surface of the thermochromic perovskite and / or reduce the rate of water vapor / moisture transport to the thermochromic perovskite, thereby providing enhanced specular transmittance and durability against water / humidity related degradation.

[0087] refer to Figure 1, an exemplary embodiment of a composite material according to the present invention is provided. As shown in the figure, a composite material 100 is provided, in particular, a thermochromic composite material 100 comprising the following: a first layer 102 of thermochromic perovskite; a second layer 104 of an antireflective material comprising an organic or inorganic polymer deposited on the first layer; and a third layer 106 of a hydrophobic material deposited on the second layer.

[0088] The first layer may include a substrate 108 on which the thermochromic perovskite layer may be deposited. The material of the substrate may be selected according to actual needs. For example, in one embodiment, the substrate 108 may be a rigid substrate, such as a glass substrate. In another embodiment, the substrate 108 may be a flexible substrate, such as a polyimide or polyethylene terephthalate (PET) substrate.

[0089] Thermochromic perovskites may include halide perovskite-based compounds having the general formula A4BX6·2H2O, wherein A is a monovalent organic cation, B is a divalent cation, and X is one or more of the halides. The term "thermochromic perovskite" generally indicates that the perovskite is arranged to undergo a chemical and / or phase change / transformation in response to an external temperature change (particularly to a degree exceeding or below the critical transition temperature of the perovskite). In particular, such a chemical and / or phase change / transformation will be accompanied by at least a change in, for example, luminous transmittance, color, etc. For example, in this embodiment, the halide perovskite-based compound A4BX6·2H2O can be reversibly changed to ABX3 in response to a temperature change, such as by a hydration-dehydration process. This change in chemical composition can cause the thermochromic perovskite to change from a transparent state to a colored state.

[0090] In one embodiment, the halide perovskite-based compound having the general formula A4BX6·2H2O may be wherein A is selected from CH3NH3 + (MA) and CH(NH2)2 + (FA) any one; B is selected from Pb 2+ Sn 2+ ,Ge 2+ Mg 2+ and Ca 2+ Any one of; and X is selected from I - Br - , Cl - and any combination thereof. In an exemplary embodiment, the halide perovskite-based compound may have the general formula (CH3NH3)4PbI 6-x-y Br x Cl y2H2O, wherein x and y are each 0 or a positive integer, and x+y≤6. That is, x and y can each be 0 to 6, wherein x+y≤6. In a specific embodiment, the halide perovskite-based compound can be (CH3NH3)4PbI 6-y Cl y 2H2O, wherein y is 0 to 6.

[0091] It should be understood that the thickness of the thermochromic perovskite layer can affect the optical properties of the composite material, such as luminous transmittance. In one embodiment, the thermochromic perovskite layer can have a thickness of about 1.4 μm to about 1.8 μm, about 1.4 μm to about 1.7 μm, about 1.5 μm to about 1.7 μm, about 1.6 μm to about 1.8 μm, or about 1.6 μm to about 1.7 μm. Preferably, the thermochromic perovskite layer can have a thickness of about 1.6 μm.

[0092] As described above, the second layer 104 of anti-reflective material may include an organic or inorganic polymer deposited on the first layer 102. As used herein, the term "anti-reflective material" generally describes a material, particularly a polymer, more particularly an organic and / or inorganic polymer, that is arranged to reduce reflection and / or light scattering from the surface of the thermochromic perovskite layer. In particular, the anti-reflective material may be arranged to reduce reflection by, for example, providing a substantially smooth surface on the thermochromic perovskite layer and / or having a refractive index (n) that matches the air-thermochromic perovskite layer interface. In an example embodiment, the anti-reflective material may have an R of about 55 nm. a The phrase "matching" generally means that the refractive index of the anti-reflective material can be close to or between air (n≈1) and thermochromic perovskite (n≈2). In an example embodiment, the anti-reflective material can have a refractive index between air and thermochromic perovskite, which thus improves the tolerance of the light propagation path to surface roughness, thereby reducing light scattering at the thermochromic perovskite surface boundary. Preferably, the refractive index of the anti-reflective material can be about 1.5 to about 1.55.

[0093] The anti-reflective material may include any of the following: epoxy resin, poly(methyl methacrylate), polyvinyl pyrrolidone, poly(vinyl alcohol), polydimethylsiloxane, poly(acrylic acid), poly(acrylamide), poly(aniline), poly(ethylene oxide), poly(N-acryloxysuccinimide), poly(N-isopropylacrylamide), poly(N-isopropylmethacrylamide), poly(N-vinylcaprolactam), poly(N-vinylpyrrolidone), poly(methacrylic acid), poly(styrenesulfonic acid), polyurethane, poly(propylene oxide), perhydropolysilazane, or a combination thereof.

[0094] In one embodiment, the antireflective material may be perhydropolysilazane (PHPS). The term "perhydropolysilazane", "polyperhydrosilazane" or "inorganic polysilazane" generally refers to a polymer in which silicon atoms and nitrogen atoms alternately form a basic skeleton. In particular, perhydropolysilazane may be in the form of a SiO x / SiON x In the form of a homogeneous inorganic film. SiO x / SiON x The film can have a refractive index substantially similar to that of ordinary SiO2 (n≈1.5). In addition, it is believed that SiO formed by PHPS x / SiON x The film will be superior to ordinary SiO2, because the deposition of ordinary SiO2 films usually relies on high vacuum clean room coating methods such as chemical vapor deposition and physical vapor deposition. These methods require expensive deposition equipment and can only deposit conformal layers on rough surfaces, which is considered to be unhelpful for smooth surfaces, especially those of thermochromic perovskites with multiple valleys. In contrast, PHPS can be deposited by solution-based coating processes such as spin coating and spray coating, which is considered to be effective in reducing the roughness of thermochromic perovskite surfaces. A detailed comparison will be disclosed in the later part of this disclosure.

[0095] The third layer 106 of hydrophobic material can include a super-hydrophobic layer. As used herein, the phrase "super-hydrophobic" refers to a material or surface of such material having a water drop contact angle of about 150° or greater, such as about 150° to about 200°, about 150° to about 190°, about 155° to about 190°, about 155° to about 180°, about 155° to about 170°, about 155° to about 165°. In one embodiment, the super-hydrophobic layer can have a water contact angle of about 160°. Preferably, the super-hydrophobic layer can include a layer of a fluorinated nano-coating, such as any one of fluorinated SiO2, fluorinated TiO2, and fluorinated ZnO coatings. In a specific embodiment, the super-hydrophobic layer can include a layer of a fluorinated SiO2 coating.

[0096] Without wishing to be bound by theory, the inventors have devised that by employing a second layer of anti-reflective material as described herein and a third layer of hydrophobic material on a first layer of thermochromic perovskite, the thermochromic perovskite will be protected from bulk water such as water droplets, but a preferred amount of water vapor or moisture will be allowed to contact the thermochromic perovskite by reducing the transport rate of water vapor / moisture. Thus, water vapor / moisture can support thermochromism (i.e., the hydration-dehydration process of the thermochromic perovskite as described herein) but trigger water / humidity-related degradation as described herein to a minimum extent. Thus, it is believed that the durability of the composite material described herein will be enhanced compared to a typical thermochromic perovskite material. For example, in a specific embodiment, the composite material described herein can maintain greater than 20% of the solar regulation capacity during a 45-day aging test, and its decay rate is 37 times lower than the decay rate of the original thermochromic perovskite material. The detailed properties of the composite material according to this specific embodiment will be disclosed in the later part of this disclosure.

[0097] A method for preparing a composite material as described herein will now be disclosed. The method may begin with a step of coating a thermochromic perovskite on a substrate made of glass or PET to form a first layer. In particular, the coating step may be a solution-based coating method involving spin coating or blade coating a layer of a thermochromic perovskite precursor onto a substrate. In particular, the thermochromic perovskite precursor may be prepared by mixing AX and BX2 in a molar ratio of about 4:1 to about 7:1 in a solvent such as dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), followed by stirring at a temperature of about 50°C to about 60°C for about 1 hour, wherein A is a monovalent organic cation, B is a divalent cation, and X is one or more of the halides as defined herein.

[0098] The thermochromic perovskite is (CH3NH3)4PbI 6-y Cl y ·2H2O (wherein y is defined as 0 to 6 as described herein), its precursor can be prepared by mixing CH3NH3I and PbCl2 in a molar ratio of about 6.5:1 in DMF. The mixture can then be stirred at a temperature of about 50°C for about 1 hour. Thereafter, (CH3NH3)4PbI 6-y Cl y · 2H2O halide perovskite-based precursors were spin-coated onto glass or PET substrates at a spin speed of about 2000 rpm for about 1 hour.

[0099] Optionally, the substrate may be cleaned with a suitable reagent or solvent (such as detergent, ethanol, deionized water, etc.) and / or with a plasma cleaner.

[0100] After coating the thermochromic perovskite onto the substrate, the thermochromic perovskite may be subjected to annealing. In particular, the annealing step may facilitate the removal (evaporation) of residual solvent of the precursor. In the above embodiment where the solvent is DMF, the annealing process may be performed at about 100° C. for about 1 hour.

[0101] The next step of the method may be to coat the anti-reflective material on the first layer to form a second layer. In particular, the coating step may be a solution-based coating method that involves spin coating or scraping a layer of anti-reflective material onto the substrate. The anti-reflective material may comprise a homogeneous inorganic material that is solidified by curing after spin coating or scraping on the first layer. For example, in an embodiment where the anti-reflective material is perhydropolysilazane, the homogeneous inorganic material may be formed by dissolving perhydropolysilazane (such as in an amount of 20 wt.%) in a solvent (such as dibutyl ether) to form a precursor solution. The precursor solution may then be spin coated or scraped onto the first layer of the thermochromic perovskite. Thereafter, the coated precursor solution may be cured by curing the precursor solution at a temperature of about 100° C. for about 2 hours. Thus, SiO may be formed on the first layer of the thermochromic perovskite. x / SiON x A homogeneous inorganic material layer.

[0102] The method can finally proceed to the step of coating silica-based nanoparticles on the second layer to form a third layer. Similar to the previous two coating steps described above, the coating step of the silica-based nanoparticles is a solution-based coating method, but preferably ultrasonic spraying. It is believed that the ultrasonic spraying method is advantageous in the following aspects: 1) spraying can produce large-area thin films with excellent uniformity compared to other coating methods (such as spin coating and dip coating); and 2) while coating the silica-based nanoparticle solution, the ultrasonic machine can atomize the solvent in the silica-based nanoparticle solution, thereby minimizing damage to the thermochromic perovskite caused by any functional groups of the solvent (e.g., -OH groups of ethanol).

[0103] For example, in the embodiment where the silicon dioxide-based nanoparticles can be SiO2 nanoparticles, particularly fluorinated SiO2 nanoparticles, the nanoparticles can be deposited on the second layer by applying a solution of SiO2 nanoparticles, such as an ethanol solution of SiO2 nanoparticles, by using an ultrasonic sprayer. In particular, the ultrasonic sprayer can simultaneously atomize the solvent in the SiO2 nanoparticle solution when applying the solution. Optionally or additionally, the sample stage of the machine on which the composite material comprising the first layer and the second layer as described above is placed can be set to a preferred temperature to further promote the evaporation of the solvent on the second layer. It should be understood that the preferred temperature can vary depending on the solvent used in the SiO2 nanoparticle solution. For example, in the embodiment where the solvent is ethanol, the temperature of the sample stage can be about 50°C to about 60°C.

[0104] Hereinafter, the present invention is described in more detail by way of examples, but the present invention is not limited thereto.

[0105] Example

[0106] Materials and Chemicals

[0107] CH3NH3I (MAI, 99.5%) was provided by Xi'an Polymer Light Technology Corp. PbCl2 (99%) was purchased from Sigma-Aldrich Dimethylformamide (DMF, ≥99.5%) was purchased from Alfa Aesar PHPS was provided by Iota Silicone Oil Fluorinated SiO2 nanoparticles / ethanol solution was provided by Solmont Tech

[0108] Methods and characterization

[0109] Characterization and Measurement

[0110] The FTIR spectrum of PHPS was obtained by PerkinElmer Spectrum 3. SEM images and energy dispersive X-ray spectroscopy (EDS) images of the samples were obtained by FEI Quanta 450. Transmission electron microscopy (TEM, 2010F, Jeol) was used to characterize the size of SiO2 nanoparticles.

[0111] The transmittance spectra were obtained by UV-Vis-NIR spectrophotometer from 300 nm to 2500 nm (Lambda 1050, Perkin Elmer equipped with a 150 mm integrating sphere detector). A custom-made temperature controller (including a heater, a T-type thermocouple and a temperature controller) was connected to the window sample to control the temperature while measuring the transmittance in cold (25°C) and hot (60°C) states.

[0112] The luminous transmittance (τ) of each window is calculated by lum ):

[0113]

[0114] To quantify the amount of visible light transmitted, τ(λ) is the transmittance of the window at wavelength λ. y(λ) is the photopic luminous efficiency of the human eye as defined by the CIE (International Commission on Illumination) standard.

[0115] The total solar transmittance is defined as the transmittance AM 1.5 (λ) is the AM1.5G solar irradiance spectrum). Δτ sol It is calculated as follows:

[0116]

[0117] According to ASTM D1003 “Standard Method for Haze and Luminous Transmittance of Transparent Plastics”, the haze is calculated as

[0118]

[0119] Where T1 is the incident light, T2 is the total light transmitted by the sample, T3 is the light scattered by the device, and T4 is the light scattered by the sample and the device. The roughness of the samples was measured by 3D surface metrology (Bruker NPFLEX).

[0120] In order to measure the transition temperature T of T-perovskite c The samples were heated and cooled on a high-precision temperature-controlled hot plate (CHEMAT 4AH) between room temperature and 60°C at intervals of 2°C. For each temperature set point, the sample was kept on the hot plate for 5 minutes to ensure color stability. At the same time, the transmittance at 550nm was measured by a lens transmissometer (SDR8508). T was then calculated by plotting the first derivative of the transmittance with respect to temperature as a function of temperature. c , where T c is the minimum point of the first-order derivative. The transition time is measured by observing the coloration and fading of the smart window during heating and cooling at the corresponding transition temperature points.

[0121] Water CA and sliding angle measurements were performed by a static CA instrument (BiolinTheta), and 4 μL of water was dropped on each test surface. For durability testing, the original T-perovskite window (TPW) and the mask-inspired thermochromic perovskite smart window (MTPW) were placed in an enthalpy test chamber, and the conditions of the enthalpy test chamber were set to 23°C / 60%RH and 35°C / 80%RH to simulate the ambient environment and humid and hot environment, respectively. The samples were heated and cooled once a day. Under hot conditions, the samples were kept at the transition point to simulate their coloring state in actual conditions. The transmittance of the samples in cold and hot states was measured to judge the stability of the T-perovskite.

[0122] For the Pb leakage test, the Pb concentration in the contaminated water was detected by an ICP-MS instrument (PerkinElmer 2000). For the FDTD simulation, PHPS and H-MAPbI were measured by a polarization ellipsometry instrument (JA Woollam RC2). 3-x Cl x (MA=CH3NH3 + ) in the cold and hot states. In order to obtain the reflection and transmission spectra of the window in the wavelength range of 0.3μm–2.5μm in the FDTD simulation (Lumerical software), a plane wave was placed on top as a light source. 3-x Cl x The PHPS and TPW layers are created based on the roughness measured by 3D surface metrology. The boundary condition along the z direction is defined as a perfectly matched layer (PML), while symmetric boundary conditions are applied in the x and y directions. To verify the accuracy of the FDTD model, the simulated transmittance of TPW and PTPW is compared with the experimental results, and Figure 2 As shown in Figure 2, their similar transmittance spectra prove the reliability of the FDTD model. In addition, the scattering cross section of a single SiO2 nanoparticle is simulated to calculate its scattering efficiency. A total field scattered field (TFSF) source is used as the incident light, and the boundary conditions along the x, y, and z directions are all defined as PML. The mesh size is 0.5 nm. The output of the FDTD simulation is the scattering cross section (C sca ), and the scattering efficiency coefficient (Q sca ) is C sca Normalized to

[0123]

[0124] where πr 2 is the geometric cross-sectional area of ​​the scattering particle.

[0125] Example 1

[0126] Fabrication of mask-inspired thermochromic perovskite smart windows (MTPWs)

[0127] The synthesis scheme of MTPW is Figure 3 As shown in the figure, the manufacturing is carried out by a full solution-based coating method.

[0128] Specifically, the glass substrate was cleaned with detergent, ethanol, and deionized (DI) water in an ultrasonic bath for 15 min and then dried with N2. The glass substrate was further cleaned in a plasma cleaner (FARI GD-5) for 200 s. 3-x Cl x Precursor (MA = CH3NH3 + ) was synthesized by mixing MAI (CH3NH3I) and PbCl2 in a molar ratio of 6.5:1 in DMF solvent, followed by stirring at 50°C for 1 hour. H-MAPbI was coated with a spin coater (Laurell H6-23) at 2000 rpm. 3-x Cl x The precursor was spin-coated on glass for 15 seconds and subsequently annealed at 100 °C for 1 hour to evaporate the residual DMF, resulting in a 1.6 μm thick T-perovskite film ( Figure 4A ). The samples obtained at this stage are called T-perovskite windows (TPW).

[0129] Then, a 20 wt % PHPS solution in dibutyl ether (a non-toxic and non-polar solvent with a low dielectric constant of 3.1) was spin-coated on the T-perovskite layer at 500 rpm for 15 s, and the sample was cured at 100 °C for 2 h in air ( Figure 4B ). The moisture and oxygen in the air cause the Si–N bonds in PHPS to break, and PHPS is gradually converted into a homogeneous SiO x / SiON x ( Figure 5 ).like Figure 6 As shown in the figure, as the curing time increases from 1 hour to 3 hours, the corresponding NH (3400cm -1 )、Si-H(2150cm -1 ) and Si-N (830cm -1 ) The Fourier transform infrared (FTIR) peak of stretching vibration decreases, and the peak near 1050cm -1 The Si-O peak increases. The samples obtained at this stage are called PHPS-coated T-perovskite windows (PTPW).

[0130] Then, the sample was moved to an ultrasonic sprayer (UC 330, Siansonic Technology) to coat the SiO2 nanoparticles. It is believed that the ultrasonic spraying method is advantageous in the following aspects: 1) spraying can produce large-area thin films with excellent uniformity compared to other coating methods (such as spin coating and dip coating); and 2) the ultrasonic machine can atomize the ethanol solvent of the SiO2 nanoparticle solution, thereby minimizing the damage of the -OH group to the T-perovskite.

[0131] Specifically, super-hydrophobic SiO2 nanoparticles were coated using an ultrasonic spray system (UC 330, Siansonic Technology) equipped with a 45kHz frequency nozzle (Z402, Siansonic Technology). The sample was placed on the vacuum table of the spray machine, perpendicular to the nozzle. In particular, the vacuum table was set to 50°C to further accelerate the evaporation of ethanol on the perovskite surface. The concentration of the SiO2 dispersion was 1wt.%. The details of the spraying parameters, including flow rate, forming air pressure, the distance between the nozzle tip and the substrate, nozzle speed, path width, number of layers, table temperature, and ultrasonic power, are as follows.

[0132] parameter: value: Flow rate 0.1ml / min Forming air pressure 0.015MPa Distance between nozzle and sample 50.0mm Nozzle speed 100mm / s Path Width 4mm Number of runs 5 / 10 / 15 / 20 / 25 / 50 / 100 / 150 Base temperature 50℃ Ultrasonic power 3.0W

[0133] The thickness of each layer was controlled by spray deposition layer by layer. The layers were deposited in an alternating zigzag path with a gap of 4 mm to cover the entire surface. The sample obtained at this stage is called MTPW.

[0134] Example 2

[0135] Characterization of MTPW

[0136] Similar to medical masks, MTPW also consists of three layers ( Figure 1 ). The bottom layer is a T-perovskite film deposited on a glass substrate. In order to protect the T-perovskite and maintain high window transparency, a transparent protective buffer layer is used to control the amount of water vapor on the T-perovskite, and the top layer is a superhydrophobic layer to effectively repel liquid water droplets. In this way, the T-perovskite window is like wearing a mask, which allows the window to "breathe" the right amount of water vapor to trigger thermochromism, but blocks excess water vapor and water droplets, thereby improving its durability. Photos of MTPW as shown Figure 7 It is highly transparent in the cold state and turns reddish brown in the hot state, and this thermochromic effect is found to be reversible.

[0137] As shown in the figure, hydrated MAPbI 3-x Cl x (H-MAPbI of the present invention 3-x Cl x or MA4PbI6-x Cl x 2H2O or (CH3NH3)4PbI 6-y Cl y ·2H2O) due to its large Δτ sol (>20%), low T c T-perovskite was selected due to its low temperature (<45°C) and short t (<2 min).

[0138] It is believed that the protective buffer layer should be selected according to the following criteria: 1) the layer must be highly transparent; 2) the material should be stable and resistant to harsh environments; and 3) the protective buffer layer should have an n between perovskite and air to minimize surface reflections.

[0139] Based on the above criteria, SiO2 was selected as the protective buffer layer, which is an inorganic oxide with a refractive index (n) of about 1.5 (refer to H-MAPbI 3-x Cl x Perovskites, which have n≈2.0 at visible wavelengths in the cold state and even higher in the hot state, Figure 8 ). At the same time, it should be understood that T-perovskite may have a rough surface that affects the light propagation path, thereby causing diffuse transmission and thus high haze ( Fig. 9 ). Therefore, in addition to the above three criteria, the ability of SiO2 to form a smooth surface on T-perovskite should also be considered.

[0140] Typical SiO2 coating relies on high vacuum cleanroom coating methods such as chemical vapor deposition and physical vapor deposition. However, these methods require expensive deposition equipment and are only suitable for depositing conformal layers on rough surfaces, which does not help fill valleys to form smooth surfaces ( Fig. 10A and 10B ).like Fig. 10B As shown on the left, the rough surface means that the sputtering method cannot improve the surface morphology. Fig. 10B As shown on the right, there are non-fading brown spots on the T-perovskite surface, which indicates that the high-energy plasma may damage the T-perovskite during the sputtering process.

[0141] Therefore, the inventors designed to use solution-processed perhydropolysilazane (PHPS) to prepare the silicon oxide layer for MTPW.

[0142] PHPS is a silicone (SiH2-NH) composed of silicon atoms and nitrogen atoms in its skeleton. When annealed in air, PHPS solidifies to produce a homogeneous inorganic SiO x / SiON xThe film exhibits better barrier properties and lower sensitivity than polymers in harsh environments. The transmittance of PHPS-coated glass was found to be about 90%, which is almost as high as that of bare glass because its n = 1.55 is comparable to that of glass ( Figure 8 and Fig.11 PHPS solutions can be easily deposited using solution-based methods such as spin coating and spray coating to smooth the roughness of the T-perovskite surface ( Fig.12 ).

[0143] It is worth noting that perovskite-based devices usually rely heavily on antisolvent crystallization methods to achieve high-quality films. However, it is believed that this method has not been successfully applied to T-perovskite. In addition, common antisolvents are toxic, and dripping antisolvents requires a lot of operating experience. Compared with the antisolvent method, smooth T-perovskite windows can be easily achieved by depositing a layer of PHPS in this study without any toxic chemical treatment or cumbersome operating techniques, which is more environmentally friendly and convenient. These advantages of PHPS not only protect T-perovskite from excessive water vapor, but also improve its optical transmittance.

[0144] Meanwhile, considering that the T-perovskite window may be exposed to a large volume of water or have water droplets accumulated on its surface in practical applications, it is understandable that the water contact angle of PHPS alone is only about 99° ( Fig.13 ), which indicates that it is not superhydrophobic) may not protect the T-perovskite window from damage under continued water penetration. Therefore, the inventors designed that, similar to the hydrophobic spunbond fabric in masks that block body fluids, a superhydrophobic fluorinated nano-silica layer was applied on top of the MTPW to give it excellent water repellency.

[0145] Example 3

[0146] Optical properties of MTPW

[0147] The transmittance spectra of MTPW and TPW are shown in Fig.14 In the cold state, MTPW exhibits 83.4% of τ lum and 30.4% in the hot state, where Δτ sol is 24.4%, while TPW's τ lum In the cold state and hot state, they are 78.2% and 28.8%, respectively, where Δτ sol is 25.4%. It is worth noting that the τ of MTPW lum,冷 and τ lum,热 Both are higher than TPW because less light scattering occurs at the surface and therefore the amount of haze is reduced.

[0148] Optical haze is an important parameter of windows, which can be defined as the ratio of diffuse transmittance to the total transmittance including specular and diffuse parts ( Fig.15 ). A low haze window will provide a clear view, while a high haze window will blur the view by distorting the light, although the total transmittance remains high. Although the original TPW has a lower τ compared to other solution-based smart windows, lum and Δτ sol has advantages in all aspects (for example, for VO2 thermochromic windows, τ lum and Δτ sol Typically about 50% and about 10%, respectively), but the high haze of TPW windows has been ignored in most studies. Fig.16 As shown in Figure 2, the pavilion 10 m away from the TPW cannot be seen, while the pavilion can be clearly observed through the MTPW. Optical measurements also confirmed that the light haze of the TPW was as high as 90%, while the light haze of the PTPW and MTPW was significantly reduced to as low as 20% and 30%, respectively ( Fig.17 ).

[0149] To explain this phenomenon, the surface morphology of TPW, PTPW, and MTPW was characterized ( Fig.18 TPW has a rough and uneven surface ( Fig.18 , Image 1), which is attributed to the excess MAI in the perovskite precursor, which affects the crystallization process. The 3D morphology quantitatively determined by surface profilometry shows that the roughness of the TPW surface is Ra = 208 nm ( Fig.18 , Image 2). However, after coating with PHPS, the surface of PTPW is quite flat, as shown in Fig.18 , as shown in Image 3, and Ra is significantly reduced to 55nm ( Fig.18 , Image 4). Based on this observation, the enhanced optical performance of MTPW can be quantitatively explained as follows: Fig.19 The light path on the T-perovskite surface is shown. Along the plane wave propagation path, different parts of the wavefront encounter rough surfaces at different heights. Therefore, the scattered components have a phase difference. With respect to the components transmitted from point A of the rough surface and the flat surface at the average height [h], the phase difference is:

[0150]

[0151]

[0152] Δh=h A -[h],(c)

[0153] where k is the wave number in vacuum, Δh is the height variation around the mean of the rough surface height [h], and n is the refractive index of the medium. According to the Rayleigh roughness criterion, the standard deviation of the phase difference should be less than π / 2 to ensure constructive interference (i.e., specular transmission). In this case, the surface can be considered to be slightly rough or even flat. To satisfy the Rayleigh roughness criterion, based on equations (a)-(c), the following must hold:

[0154]

[0155] Equation (d) shows that when the refractive index of the two media is relatively close, the tolerance to RMS is greater, and vice versa. When light encounters peaks and valleys, the rough surface of TPW and the large refractive index difference between air (n≈1.0) and T-perovskite (n≈2.0) both cause strong scattering, resulting in high light haze and reduced specular transmittance. Compared with air, the n value of PHPS is relatively close to that of perovskite. Therefore, using PHPS on the top can improve the tolerance of the light propagation path to surface roughness (Equation (d)), thereby reducing light scattering at the boundary of the T-perovskite surface. In addition, the n value of PHPS is between that of air and T-perovskite, and it can also act as an anti-reflection layer to improve the total transmittance.

[0156] To verify the above explanation, we performed finite-difference time-domain (FDTD) simulations to analyze the light propagation through different surfaces. The model established by FDTD software is as follows: Fig. 20 Ellipsometer measurements of PHPS and T-perovskite (H-MAPbI 3-x Cl x ) in the cold and hot states, such as Figure 8 shown. Fig.21 The light propagation process at the air / window interface of an ideal smooth TPW, a rough TPW, and a PTPW is shown.

[0157] For an ideal TPW, the direction of light propagating along the normal direction does not change at the air / window interface ( Fig.21 , Image 1), resulting in high specular transmittance and low haze. However, if the TPW surface is rough (the roughness data of TPW is taken from Fig.18 , Image 2), the light propagation path will be significantly changed at the air / TPW interface due to strong scattering ( Fig.21 , Image 2), resulting in increased diffuse reflection and transmission. PHPS is deposited on a rough TPW surface (the roughness data of PHPS is taken from Fig.18 , Image 4), most of the light maintains its original path along the normal direction, and the scattering at the T-perovskite surface is significantly suppressed compared to the rough TPW ( Fig.21 , Image 3). When comparing Fig.21 Image 2 and Fig.21 When looking at Image 3, it is noted that the reflected field intensity above the air / window surface is reduced after the PHPS coating. The simulated reflectance spectra further demonstrate that the reflectance on the TPW is reduced from 11.8% to 6.8% ( Fig. 22 ). This desired reduction in reflectivity is caused by the anti-reflection effect of the PHPS layer, which results in τ lum Increase( Figure 2 ).

[0158] In addition, the angular distribution of scattered light in the reflected and transmitted fields for the rough TPW and smooth PTPW was extracted from the FDTD simulations based on the bidirectional scattering distribution function (BSDF). The BSDF can characterize the light scattering at the surface in a radiometric manner as a function of the angular position of the incident and scattered beams. The scattered light distribution in the transmitted and reflected fields of the rough TPW surface is shown in Figure 2 over a wide angular range ( Fig.23 ), resulting in a blurred visual effect. In contrast, for the PTPW surface, both the transmitted and reflected light are concentrated in a smaller angle range ( Fig.24 ), resulting in a clearer view. In summary, it is believed that the top PHPS layer benefits the optical performance of the TPW in two ways: by significantly reducing haze by smoothing the originally rough surface, and by improving overall transparency through anti-reflection effects.

[0159] The top layer of MTPW is a super-hydrophobic layer of nanoparticles for water repellency. SiO2 is believed to have the lowest refractive index in the visible range of 1.45 among nanoparticles in the art, so it was chosen to minimize light scattering. In addition, according to Mie scattering theory, particle size also affects scattering efficiency (Q s ). Using FDTD simulation, the Q of SiO2 nanospheres s Calculated as a function of particle size across the solar spectrum ( Fig.25 ). Fig.26 Display, Q s As the diameter decreases, Q s is very small, indicating limited impact on the optical properties. Therefore, SiO2 nanoparticles with a diameter of 20 nm were selected for the fabrication of MTPWs (Figure S27). Fig.28 As shown in Figure 2, the transmittance spectrum of MTPW is almost the same as that of PTPW without SiO2 nanoparticles. The haze increases only slightly due to the increase in roughness ( Fig.17 , Fig.18 , Images 5 and 6).

[0160] Example 4

[0161] The transformative nature of MPTW

[0162] For thermochromic smart windows, it should be understood that in addition to its excellent optical properties, it is also necessary to include a low transition temperature (T c ) and short transition time (t). Therefore, the transition properties of MTPW were investigated. In particular, the c,h ) and cooling (T c,c ) process of PHPS layer and SiO2 nanoparticles on H-MAPbI 3-x Cl x The relatively low T of perovskite c impact.

[0163] like Fig.29 As shown in Figure 2, the temperature-dependent transformation processes of TPW and MTPW are almost the same. c,h and T c,c The calculated values ​​are 43.2℃ and 35.6℃, respectively, while the calculated values ​​of MTPW are 43.4℃ and 35.9℃, respectively, which means that the coating has a significant effect on T c No effect. In addition, Fig.30 As shown, the original TPW completes its color transformation within 65 s and 120 s during heating and cooling, respectively. For MTPW, due to the water vapor transport rate limited by the PHPS and SiO2 nanoparticle layers, the transformation time during heating and cooling is inevitably extended to 120 s and 300 s, respectively, which is still considered acceptable for practical applications.

[0164] Example 5

[0165] Superhydrophobicity and long-term stability of MTPW

[0166] The wettability of pristine TPW and PTPW was compared and the results are shown in Fig.31A and 31B As shown in the figure, the pristine TPW is hydrophilic with an initial contact angle (CA) of 21.2°, and the T-perovskite film is immediately damaged by a water droplet ( Fig.32 ). The CA decayed to 12.4° within 1 second and could not be measured by the CA meter after 3 seconds, indicating severe corrosion by water. PTPW exhibited a higher CA of 98.4°, but the CA quickly decreased to 54.1° after 9 minutes. The hydrophobicity of TPW and PTPW was poor and could not effectively repel water on the window surface. Therefore, the superhydrophobic feature of T-perovskite smart windows should be achieved to physically block harmful moisture and water.

[0167] As described above, superhydrophobic SiO2 nanoparticles with a diameter of 20 nm were coated on the PHPS layer. Fig.33The surface SEM images of SiO2 nanoparticles for different spin coating cycle numbers are shown. As the number of spray coating cycles increases, the packing density of SiO2 nanoparticles increases, and when the number of cycles exceeds 25, the surface is almost completely covered by SiO2 nanoparticles. Fig.34 The effect of the number of spraying cycles on the CA is shown, where an increasing trend from 115.3° in 5 cycles to 160.8° in 50 cycles is observed. After 50 cycles, the CA is almost unchanged or even slightly decreased. This can be attributed to the fully covered SiO2 nanoparticles, which leads to an increase in the area of ​​the liquid-solid contact interface, resulting in higher surface adhesion. In addition, the sliding angle of the MTPW is only 5.7° in 50 cycles, which is beneficial for windows. Therefore, the optimal SiO2 spraying schedule is recommended to be 50 cycles. After the deposition of SiO2 nanoparticles, the MTPW exhibits superhydrophobicity with a stable CA above 160° ( Fig.31A When a dyed droplet was dropped on the surface of MTPW, the droplet spread into a compressed disk shape and popped off the surface, implying an outstanding superhydrophobicity ( Fig.35 ). This excellent superhydrophobic property enables MTPW to effectively repel water and effectively prevent T-perovskite from being degraded by large volume water. In addition, a water jet test was performed to test the waterproof ability of MTPW. MTPW was placed under a faucet and rinsed with high-speed water (flow rate: about 4.7m / s). T-perovskite still exists, and it can still exhibit reversible color conversion ability during heating and cooling, which proves the excellent waterproofness of MTPW (data not shown).

[0168] The durability of MTPW was studied by evaluating its optical stability. Specifically, the long-term optical performance of MTPW was examined by humidity resistance tests at different relative humidity (RH) levels. The experiments were performed in an environmental test chamber to precisely control the environmental conditions.

[0169] like Fig.36A and 36B As shown, during the aging test at 60% RH, all characteristics of TPW, including τ lum,冷 , τ lum,热 and Δτ sol , showing an obvious decay trend. In particular, τ lum,热 A significant increase from 28.8% to 68.8% occurred within five days, leading to a sol The drastic decrease from 23.1% to 4.8% indicates the loss of thermochromism. In sharp contrast, the MTPW maintains stable optical properties over 40 days, and Δτ solThe significantly enhanced durability is attributed to the strong protection of PHPS and SiO2 superhydrophobic layers, which protect the T-perovskite film from the continuous penetration of large amounts of water vapor. Fig.37A ), TPW degrades rapidly after only half a day, where τ lum,热 increased to 54.6% and Δτ sol Even though high humidity also affects MTPW, after 20 days of aging test, MTPW still remains relatively stable τ lum,冷 and τ lum , 热 and an acceptable Δτ of about 20% sol ( Fig.37B ). By comparing Δτ sol The decay rate ( Fig.38A and 38B ), it was found that the lifetime of MTPW was significantly extended by 37 times in normal ambient environment and by 98 times in humid environment compared with that of pristine TPW, which makes it reliable for practical applications.

[0170] Due to the water vulnerability of T-perovskite films, the Pb leakage problem has attracted much attention. During the thermochromic process, T-perovskite undergoes a water-induced phase transition from MAPbX3 in the hot state to MA4PbX6·2H2O in the cold state with a size reduction. The formed low-dimensional dihydrated perovskite is further decomposed as shown in the following equation:

[0171]

[0172] The existence of strong hydrogen bonds between water molecules and toxic PbX2 results in a high solubility constant (K sp = About 10 -8 ), which causes serious Pb leakage, thus threatening the environment and human health. In order to check the Pb leakage problem, both the original TPW and MTPW were immersed in deionized water. Fig.39A As shown, the original TPW immediately changes color to yellow in only 1 second, which means Pb leakage. Fig.39B The X-ray diffraction (XRD) pattern of the yellow film shown proves that the T-perovskite film decomposes into PbI2. In contrast, the MTPW remains transparent for up to 5 minutes under water. In addition, the color still changes upon heating, indicating that the T-perovskite is well preserved and the thermochromic effect is maintained. To further estimate the Pb in contaminated water 2+ The amount of ions was measured by inductively coupled plasma-mass spectrometry (ICP-MS), as Fig.39C As shown. Pb of original TPW 2+The concentration reached 4.023 mg / L within 30 min, which is 66 times that of MTPW (0.061 mg / L). These results strongly prove that superhydrophobic MTPW is able to immobilize Pb 2+ And reduce Pb leakage, thus making MTPW more environmentally friendly.

[0173] Example 6

[0174] Application of MTPW

[0175] Compared with the original TPW, MTPW exhibits better moisture and water resistance with less lead leakage. In addition, the all-solution-based manufacturing process that does not require any additional toxic antisolvents offers potential for the scalability of MTPW. These advantages enable MTPW to be directly manufactured as a flexible window film without the need for sealing, which is more convenient and cost-effective for practical applications and installations. Here, a highly flexible MTPW film ( Fig.40A ).

[0176] Compared with the widely used Fig.40B Compared to commercial energy-saving window films that can block part of the visible and near-infrared light to constantly reduce indoor solar heat gain even in cold weather, the solar transmittance of the MTPW film of the present invention is dynamically adjusted with temperature changes, which maintains useful solar heat gain in cold weather / seasons but reduces harmful solar heat gain in hot weather / seasons ( Fig.40C ). Therefore, MTPW is expected to have better year-round energy-saving capabilities than traditional energy-saving window films.

[0177] To compare energy performance, commercial window films and MTPW films were used in five cities in the United States. Fig.40A and 40B ) conducted EnergyPlus modeling of commercial buildings ( Fig.41 ). Basic building information is listed in Fig.42 The normal windows, windows with commercial films, and windows with MTPW films used in the simulations are shown in the table and calculated by the WINDOW algorithm developed by the Lawrence Berkeley National Laboratory ( Fig.43 )'s optical information ( Fig.44 ). Climate information for each city is listed in Fig.45 shown in the table.

[0178] Overall, EnergyPlus modeling of typical U.S. cities demonstrates that the use of MTPW membranes shows higher energy savings potential than commercial membranes, especially in northern regions where buildings also have high heating demands in winter ( Fig.46 and 47) (For example, the use of conventional window films results in only a 0.4% energy saving in Philadelphia, and even more in annual energy consumption (about 1.9%) in New York).

[0179] In particular, in Philadelphia, for example, heating energy consumption in buildings with traditional window films is much higher than in buildings with regular windows, especially during the winter months of November to March ( Fig.48 ), which ultimately offsets the cooling energy saved on hot days ( Fig.49 ). In contrast, due to the intelligent thermally responsive color switching capability, MTPW maintains high solar heat gain in cold weather but low solar transmittance in hot weather. As a result, heating demand does not change significantly when using MTPW films compared to heating demand when using normal windows in winter, while cooling demand drops dramatically during the transition season and in the summer months of April to October ( Fig.48 ), which shows the advantage of intelligent optical adjustment function. For hot areas (such as Orlando), windows with MTPW and commercial window films show better energy saving ability than normal windows ( Fig.50 and 51 ), and MTPW windows exhibit better performance due to lower solar transmittance.

[0180] In conclusion, the above results indicate that MTPW window films are promising in reducing HVAC energy consumption throughout the year and their application as smart energy-saving window films is promising.

[0181] The present invention is presented by way of example only, and various other modifications and / or alterations to the described embodiments may be made by those skilled in the art without departing from the scope of the present invention as specified in the appended claims.

Claims

1. A composite material comprising: The first layer of thermochromic perovskite; a second layer of antireflective material comprising an organic or inorganic polymer deposited on the first layer; and A third layer of hydrophobic material is deposited on the second layer.

2. The composite material of claim 1, wherein the first layer comprises a substrate made of glass or PET on which the thermochromic perovskite layer is deposited.

3. The composite material of claim 1, wherein the thermochromic perovskite comprises a halide perovskite-based compound having the general formula A4BX6·2H2O, wherein A is a monovalent organic cation, B is a divalent cation, and X is one or more of a halide.

4. The composite material of claim 3, wherein A4BX6·2H2O reversibly changes to ABX3 in response to temperature changes.

5. The composite material as claimed in claim 4, wherein A is selected from CH3NH3 + and CH(NH2)2 + Any one of; B is selected from Pb 2+ 、 Sn 2+ ,Ge 2+ Mg 2+ and Ca 2+ Any one of; and X is selected from I - Br - , Cl - and any combination thereof.

6. The composite material of claim 5, wherein the halide perovskite-based compound has the general formula (CH3NH3)4PbI 6-x-y Br x Cl y 2H2O, wherein x and y are each 0 or a positive integer, and x+y≤6.

7. The composite material of claim 6, wherein the halide perovskite-based compound is (CH3NH3)4PbI 6-y Cl y 2H2O, wherein y is 0 to 6.

8. The composite material of claim 2, wherein the thermochromic perovskite layer has a thickness of 1.6 μm.

9. The composite material of claim 1, wherein the antireflective material has a refractive index between air and the thermochromic perovskite.

10. The composite material of claim 9, wherein the antireflective material comprises any one of the following: epoxy resin, poly(methyl methacrylate), polyvinyl pyrrolidone, poly(vinyl alcohol), polydimethylsiloxane, poly(acrylic acid), poly(acrylamide), poly(aniline), poly(ethylene oxide), poly(N-acryloxysuccinimide), poly(N-isopropylacrylamide), poly(N-isopropylmethacrylamide), poly(N-vinylcaprolactam), poly(N-vinylpyrrolidone), poly(methacrylic acid), poly(styrenesulfonic acid), polyurethane, poly(propylene oxide), perhydropolysilazane, or a combination thereof.

11. The composite material of claim 10, wherein the antireflective material is perhydropolysilazane.

12. The composite material according to claim 11, wherein the perhydropolysilazane is in the form of SiO x / SiON x In the form of a homogeneous inorganic membrane.

13. The composite material of claim 1, wherein the hydrophobic material comprises a superhydrophobic layer.

14. The composite material of claim 13, wherein the superhydrophobic layer comprises a layer of fluorinated nanocoating.

15. The composite material of claim 14, wherein the layer of the fluorinated nanocoating is any one of fluorinated SiO2, fluorinated TiO2, and fluorinated ZnO.

16. A method for preparing the composite material according to claim 1, comprising the following steps: The thermochromic perovskite is coated on a substrate made of glass or PET to form a first layer; coating an anti-reflective material on the first layer to form a second layer; as well as Silica-based nanoparticles are coated on the second layer to form a third layer.

17. The method of claim 16, wherein the thermochromic perovskite is subjected to annealing after it is coated on the substrate to form the first layer.

18. The method of claim 17, wherein the thermochromic perovskite is (CH3NH3)4PbI 6-y Cl y · 2H2O-based halide perovskite precursors, where y is 0 to 6, prepared by mixing CH3NH3I and PbCl2 in a molar ratio of about 6.5:

1.

19. The method of claim 17, wherein the annealing is performed at 100°C for 1 hour.

20. The method of claim 16, wherein the antireflective material comprises a homogeneous inorganic material solidified by spin coating or doctor blade coating on the first layer followed by curing.

21. The method of claim 20, wherein the homogeneous inorganic material is prepared from perhydropolysilazane dissolved in dibutyl ether.

22. The method of claim 16, wherein the first layer, the second layer, and the third layer are formed by a solution-based coating process.

23. The method of claim 22, wherein the first layer and the second layer are formed by spin coating.

24. The method of claim 23, wherein the third layer is formed by ultrasonic spraying.

25. The method of claim 24, wherein the silicon dioxide-based nanoparticles are SiO2 nanoparticles, which are deposited on the second layer by simultaneously applying a solution of the SiO2 nanoparticles and atomizing a solvent in the solution by ultrasonic spraying.

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