CN114839760A - Light valve and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of light valves, in particular to a light valve and a preparation method thereof. The invention provides a scheme for preparing the light valve by using bismuth oxyhalide nanosheets, particularly BiOF nanosheets and BiOBr nanosheets as suspended particles, develops the new application of the bismuth oxyhalide nanosheets and expands the optional range of the SPD light valve. The light valve and the suspended particle bismuth oxyhalide nanosheet thereof provided by the invention can be prepared by adopting a conventional method, have simple process and are suitable for production and popularization; the prepared light valve has stable performance and good environmental adaptability, the visible light transmittance is about 5 percent in a closed state, the visible light transmittance is 25 to 32 percent in an open state, and the effect of regulating the luminous flux is good.

Description

A kind of light valve and preparation method thereof

technical field

The invention relates to the technical field of light valves, in particular to a light valve and a preparation method thereof.

Background technique

The light valve is a device that can adjust the light flux, and the research on the light valve has been carried out for half a century. According to different dimming principles, light valves are usually divided into three categories: polymer dispersed liquid crystal (PDLC), electrochemichromic device (EC) and suspended particle device (SPD). This is achieved by sandwiching electroactive components between transparent electrodes. In an electrochromic device, the electro-active component is a chemical substance that can undergo a redox reaction in the electromagnetic field applied by the two transparent electrodes, that is, the electrochromic material gains and loses electronic color change; in a liquid crystal device, the electro-active component The active component is a liquid crystal molecule, and the luminous flux is controlled by applying an electromagnetic field to the two transparent electrodes to change the crystal structure; in the suspended particle device, the electroactive component is a suspended particle, and the motion of the suspended particle is changed by applying an electromagnetic field to the two transparent electrodes. The orientation is rearranged to realize the regulation of the luminous flux.

Among the above-mentioned types of light valves, suspended particle devices are favored by more researchers because of their excellent weather resistance, rich colors, and high transparency controllability. In general, the SPD light valve consists of two layers of transparent electrodes and a dimming layer sandwiched between the two layers of transparent electrodes. Generally, the dimming layer contains an insulating liquid-phase organic polymer, and is suspended in the polymer. of suspended particles with an internal dipole moment. When the external voltage is not turned on, these suspended particles do random Brownian motion, the overall light transmittance is poor, and the light valve is in an opaque state; when the external voltage is turned on, under the action of an applied electric field, the suspended particles move along the The direction of the electric field is oriented and arranged in a straight line, so that the incident light can partially or almost completely pass through the light valve, so as to achieve the purpose of dimming. Today's Boeing 787 aircraft windows, high-end car windows and showcases in some museums all use this technology, and with further research on light valves at home and abroad, this technology will increasingly enter the public's field of vision among.

However, the suspended particles currently used in SPD light valves are mainly nanorods. The preparation technology of suspended particles based on the morphology of nanorods is relatively mature, but the types of materials are limited, and the synthesis technology of suspended particle nanorods is favored by the United States, Israel, etc. China's technological monopoly has caused some domestic high-tech enterprises to struggle in the process of research and development, which has greatly restricted the commercial and civil process of light valve products in China. The most widely used suspended particles in the prior art are Herapathite nanorods whose chemical formula is 4C ₂₀ H ₂₄ N ₂ O ₂ ·3H ₂ SO ₄ ·2HI·I ₄ ·6H ₂ O. It can be seen from the chemical composition that quinine iodosulfate is unstable in many organic and inorganic solvents, and its thermal stability is also poor due to the presence of iodine element. This not only makes the fabrication of the suspension medium in the SPD difficult, but also greatly restricts the environmental tolerance of the SPD. Although scholars have tried to improve the stability of suspended particles by replacing iodine with other halogens, the existence of organic components in the product makes this method not fundamentally solved.

Therefore, it is very important for those skilled in the art to develop a new type of suspended particle application to obtain an SPD light valve device with more stable performance.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a light valve and a preparation method thereof. The SPD light valve with good stability is prepared by using bismuth oxyhalide nanosheets with suitable internal dipole moment as suspended particles.

A first aspect of the present invention provides a light valve, the light valve includes two layers of transparent electrodes and a light adjustment layer sandwiched between the two layers of transparent electrodes, the light adjustment layer includes a suspension, and the suspension is uniform The bismuth oxyhalide nanosheet suspended particles are dispersed, and the chemical formula of the bismuth oxyhalide is BiOX, wherein X is selected from at least one of F, Cl, Br, and I.

Preferably, the bismuth oxyhalide is selected from one of BiOF and BiOBr.

The molecule is electrically neutral, but due to different spatial configurations, the positive and negative charge centers may or may not overlap. The former is called a non-polar molecule, and the latter is called a polar molecule. The product of the distance r between the negative charge centers and the charge center q is called the dipole moment μ=r×q, and the molecular polarity can be measured by the dipole moment μ. The larger the dipole moment, the higher the molecular polarity. bigger. Bismuth oxyhalide is easy to crystallize into tetragonal nanosheets under liquid phase conditions. The nanosheets have layered properties, that is, atoms are arranged in long-range order on the (001) crystal plane (along the a/b axis) to form a layer of nanosheets. . Due to the large difference in electron cloud density between anions and cations in the bismuth oxyhalide nanosheets, and the long-range stacking of atoms on the nanosheets, the material has a strong dipole moment in the a/b crystal orientation. Under the action of an external electric field, the bismuth oxyhalide nanosheets themselves are polarized, and the random Brownian motion is reversed and becomes aligned along the a/b axis (that is, the nanosheets are perpendicular to the electric field), so that visible light can pass through, To achieve the purpose of regulating visible light throughput.

In some of these embodiments, the bismuth oxyhalide nanosheets have a planar size of less than 4 μm and a thickness of less than 300 nm.

Preferably, the plane size of the bismuth oxyhalide nanosheet is less than 1 μm, and the thickness is less than 50 nm.

In some of these embodiments, the mass fraction of bismuth oxyhalide nanosheets in the suspension is 0.05-4.0%.

Preferably, the mass fraction of bismuth oxyhalide nanosheets in the suspension is 0.1-2.0%.

There are many factors that affect the flipping of suspended particles in the electric field. Since the suspended particles in the SPD light valve are solid particles, the coordination between the dipole size of the suspended particles and the particle size is very important. When the particle size is too large, the moment action it receives in the electric field is not enough to support the flipping of the particle, so that the control of the luminous flux cannot be achieved; while when the particle size is too small, the rate of change of the luminous flux between the open and closed states of the light valve is based on As well as the requirement for the darkness of the closed light valve, the required concentration of suspended particles will be greatly increased.

In a second aspect, the present invention also provides a method for preparing the above-mentioned light valve, comprising the following steps: uniformly mixing the bismuth oxyhalide nanosheets with a suspension medium to obtain a suspension, adding spacer balls to the suspension, and then mixing the spacer balls The suspension is encapsulated between two layers of transparent electrodes, that is, the target device is obtained.

In some of the embodiments, the bismuth oxyhalide nanosheets are prepared by a wet chemical method, and the wet chemical method is a hydrothermal method, a precipitation method, a microwave method or an interface method. The bismuth oxyhalide nanosheets in the present invention can also be prepared by other wet chemical methods, which are not limited in the present invention. In addition, when the present invention adopts the wet chemical method to prepare the bismuth oxyhalide nanosheets, the bismuth source can be selected from at least one of hydrated or non-hydrated salts such as bismuth nitrate, bismuth chloride, and bismuth sulfate.

In some of these embodiments, the suspending medium is selected from at least one of siloxane, acrylic, and alkylene oxide monomers or polymers.

Preferably, the suspending medium is an acrylic polymer.

In some of these embodiments, the viscosity of the suspension medium is less than 2000 cp.

The suspension medium can maintain the suspended state of the suspended particles in the suspension. When the viscosity of the suspension medium is appropriate, it can ensure that the bismuth oxyhalide nanosheets are evenly distributed in the suspension, so as to ensure uniform light transmission of the obtained light valve and ensure that the light valve is uniform in the electric field. Under the action, the nanosheets can be freely flipped in the suspension to realize the dimming effect; however, when the viscosity of the suspension is too large, the flipping of the nanosheets is limited, so that the device cannot exhibit the dimming effect.

In some of these embodiments, the spacer balls are 10-200 μm in size.

In some embodiments, the transparent electrode is selected from at least one of ITO conductive glass, ITO conductive film, nano Ag wire conductive film, nano Cu wire conductive film, PEDOT conductive film, graphene conductive film, and carbon nanotube conductive film A sort of.

In a third aspect, the present invention also provides an application of a bismuth oxyhalide nanosheet in a light valve.

The inventors of the present invention use nanosheets with an internal dipole moment as suspended particles, and under the action of an electric field, the nanosheets are flipped to be parallel to the electric field lines, thereby realizing the control of visible light transmittance. In the present invention, the bismuth oxyhalide nanosheets exhibit excellent shading effect in the initial state of the device, and its mass fraction in the suspension is only 0.1-2.0%, which is significantly less than at least 2-10% when the nanorods are used as suspended particles At the same time, the reduction of particle content can effectively avoid the occurrence of agglomeration, and further ensure the uniformity of particle dispersion in the suspension, thereby ensuring the uniformity of light shading and light transmission of the device.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention proposes a scheme for preparing light valves by using bismuth oxyhalide nanosheets, especially BiOF nanosheets and BiOBr nanosheets as suspended particles, which opens up new uses of bismuth oxyhalide nanosheets and expands the performance of SPD light valves. Optional range. The visible light transmittance of the light valve provided by the invention is about 5% in the closed state, and the visible light transmittance is 25-32% in the open state, and the effect of adjusting the luminous flux is good.

(2) The present invention utilizes the bismuth oxyhalide nanosheets with internal dipole moment to flip in the electric field for directional distribution, so as to realize the control of visible light transmittance. distribution, the absorption and reflection of visible light are large, and the light transmittance of the light valve is low; after electrification, the bismuth oxyhalide nanosheets are perpendicular to the electrodes due to their own dipole moment flipping under the action of the electric field and directional arrangement, resulting in the light valve The device is transformed from a light-shielding state to a light-passing state. Since the bismuth oxyhalide nanosheets are all inorganic materials, the physical and chemical properties are relatively stable, and the SPD light valve prepared by using the bismuth oxyhalide nanosheets as suspended particles has stable performance and good environmental adaptability.

(3) The suspended particle bismuth oxyhalide nanosheets used in the present invention can be prepared by conventional wet chemical methods, and the reaction mode, reaction raw materials and reaction conditions are less restricted, and the source of raw materials is expanded. At the same time, the light valve can be prepared by conventional methods. By selecting the appropriate size, mass fraction and suspension medium viscosity of bismuth oxyhalide nanosheets, a light valve device with good performance is obtained. The preparation process is simple and suitable for production and promotion.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the drawings that are required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a schematic structural diagram of a light valve of the present invention;

Fig. 2 is the SEM characterization diagram of BiOF nanosheets in the inventor's Example 1;

3 is a comparison diagram of the transmittance of the light valve based on BiOF nanosheets to 200-800nm wavelength light after applying a voltage of 200V in Example 1 of the inventor;

Fig. 4 is the SEM characterization diagram of BiOBr nanosheets in the inventor's example 2;

5 is a comparison diagram of the transmittance of the light valve based on BiOBr nanosheets to 200-800nm wavelength light after applying a voltage of 200V in Example 2 of the inventor;

6 is a comparison diagram of the transmittance of the light valve based on BiOF nanosheet in the inventor’s comparative example 1 to 200-800nm wavelength light after applying a voltage of 200V;

7 is a comparison diagram of the transmittance of the light valve based on BiOF nanosheets to 200-800nm wavelength light after applying a voltage of 200V in Comparative Example 2 of the inventor;

In the figure: 100, light valve; 101, transparent electrode; 102, dimming layer; 103, suspension; 104, suspension medium; 105, bismuth oxyhalide nanosheet suspended particles.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

FIG. 1 schematically shows the light valve 100 of the present invention, wherein the light valve 100 includes two layers of transparent electrodes 101 and a light adjustment layer 102 sandwiched between the two layers of transparent electrodes. The light adjustment layer 102 A suspension 103 is included, and the suspension 103 includes a suspension medium 104 and bismuth oxyhalide nanosheet suspended particles 105 uniformly dispersed in the suspension medium 104 . In the absence of an external electric field, that is, the light valve 100 is in an off state, at this time, the bismuth oxyhalide nanosheet suspended particles 105 in the suspension medium 104 are in random positions due to random Brownian motion, and incident into the The light beam in the light valve 100 is absorbed/scattered, the overall light transmittance is poor, and the light valve is in an opaque state. When an electric field is applied to it, that is, the light valve 100 is in an on state, and the suspended particles 105 of the two-dimensional bismuth oxyhalide nanosheets in the dimming layer 102 are polarized under the action of the electric field, and transformed from random Brownian motion It is in the state of being oriented and arranged along the direction of the electric field lines, so that the light beams can pass through the light valve 100, and the light valve is relatively transparent. In this way, the motion state of the suspended particles of the bismuth oxyhalide nanosheets is controlled by closing the electric field, and the purpose of controlling the luminous flux for dimming is realized.

More specifically, the chemical formula of the bismuth oxyhalide is BiOX, wherein X is selected from at least one of F, Cl, Br, and I; preferably, the bismuth oxyhalide is selected from one of BiOF and BiOBr.

Moreover, the plane size of the bismuth oxyhalide nanosheet is less than 4 μm and the thickness is less than 300nm, preferably, the plane size of the bismuth oxyhalide nanosheet is less than 1 μm and the thickness is less than 50nm.

Further, the mass fraction of bismuth oxyhalide nanosheets in the suspension is 0.05-4.0%; preferably, the mass fraction of bismuth oxyhalide nanosheets in the suspension is 0.1-2.0%.

Meanwhile, the selection of the bismuth source may include, but is not limited to, at least one of hydrated and/or non-hydrated salts such as bismuth nitrate, bismuth chloride, bismuth sulfate, and bismuth chlorate.

Meanwhile, the transparent electrode is selected from one of ITO conductive glass, ITO conductive film, nano Ag wire conductive film, nano Cu wire conductive film, PEDOT conductive film, graphene conductive film, and carbon nanotube conductive film.

The present invention will now be described in more detail with reference to the following examples.

Example 1

1) Preparation of BiOF nanosheets

Dissolve 1 mmol of hydrated bismuth nitrate (Bi(NO ₃ ) ₃ ·5H ₂ O) in 60 mL of ethylene glycol, and slowly drop 10 mL of 0.1 mol/L NH ₄ F solution into it while stirring; The pH of the obtained mixed liquid was adjusted to 10, and after stirring for 30 min, the obtained liquid was transferred to a hydrothermal kettle, and then placed in a constant temperature drying oven at 200 ° C for 24 h; after the reaction liquid was cooled to room temperature, a 1000 r/min The obtained product was centrifuged at a rotating speed, and then the upper layer of turbid liquid was taken and continued to be centrifuged at 5000 r/min, and then dried to obtain BiOF nanosheets, as shown in FIG. 2 .

The SEM characterization results show that the plane size of the prepared BiOF nanosheets is below 3 μm and the thickness is below 300 nm.

2) Preparation of suspensions containing BiOF nanosheets

In a 250ml two-necked flask, 24g of lauryl methacrylate, 0.6g of hydroxypropyl methacrylate and 30g of toluene were uniformly mixed, and 2g of hexanethiol was added to the resulting mixed solution; The toluene solution was uniformly mixed with the above organic mixed solution, and under the protection of N ₂ , the polymerization reaction was carried out at 60 °C for 18 h to obtain a suspension medium with a viscosity of 1600 cp; 0.2 g of BiOF nanosheets were weighed and mixed in 19.8 g of all In the suspension medium, the mixed suspension medium was ultrasonically stirred for 10 min, and centrifuged for 2 min at a rotational speed of 2000 r/min to remove the incompletely dispersed particles in the lower layer to obtain a suspension containing BiOF nanosheets. The mass fraction of BiOF nanosheets is 1.0%.

3) Preparation of Light Valves Containing BiOF Nanosheets

Add spacer balls with a mass fraction of 3‰ and a diameter of 100μm to the obtained suspension, stir evenly; then take an appropriate amount of the suspension mixed with spacer balls, coat it between two layers of ITO conductive film, and use insulating glue to encapsulate the conductive film. Around the film, a simple SPD light valve was obtained.

As shown in Figure 3, the light valve transmits only 6% of light in the wavelength range of 200-800nm in the "OFF" state, and after applying 200V to it, that is, in the "ON" state, its The transmittance to light is increased to about 25%.

Example 2

1) Preparation of BiOBr nanosheets

Dissolve 2 mmol of hydrated bismuth nitrate (Bi(NO ₃ ) ₃ ·5H ₂ O) in 100 mL of ethylene glycol to obtain a clear solution, which is then heated to 160° C.; 6 mmol of NaOH is added to the above solution and stirred for 10 min to obtain light yellow suspension, and then 2mmol of tetrabutylammonium bromide powder was added to the suspension; the resulting mixture was stirred at 160°C, and after being reacted for 12h, slowly cooled to room temperature, then centrifuged, and then dried , BiOBr nanosheets were obtained, as shown in Figure 4.

SEM characterization results show that the plane size of the prepared BiOBr nanosheets is below 2 μm and the thickness is below 100 nm.

2) Preparation of suspensions containing BiOBr nanosheets

In a 250ml two-necked flask, 24.4g of lauryl methacrylate, 0.6g of hydroxypropyl methacrylate and 30g of toluene were uniformly mixed, and 3g of hexanethiol was added to the resulting mixed solution; 10g of toluene solution was uniformly mixed with the above-mentioned organic mixed solution, and under the protection of _N2 , polymerized at 60°C for 12h to obtain a suspension medium, the viscosity of which was 1300cp; 0.1g of BiOBr nanosheets were weighed and mixed in 19.9g In the suspension medium, the mixed suspension medium was ultrasonically stirred for 10 min, and centrifuged for 2 min at a rotational speed of 2000 r/min to remove the incompletely dispersed particles in the lower layer to obtain a suspension containing BiOBr nanosheets. The mass fraction of BiOBr nanosheets in the solution was 0.5%.

3) Preparation of light valve containing BiOBr nanosheets

Add spacer balls with a mass fraction of 3‰ and a diameter of 100μm to the obtained suspension, stir evenly; then take an appropriate amount of the suspension mixed with spacer balls, coat it between two layers of ITO conductive film, and use insulating glue to encapsulate the conductive film. Around the film, a simple SPD light valve was obtained.

As shown in Figure 5, the light valve transmits only 5% of light in the wavelength range of 200-800 nm in the "OFF" state, and after applying a voltage of 200V to it, that is, in the "ON" state, its The transmittance to light increases to about 32%.

Comparative Example 1

This comparative example includes most of the operation steps of Example 1, except that the mass fraction of BiOF nanosheets in the suspension is different. The specific preparation method is as follows:

1) Preparation of BiOF nanosheets

Dissolve 1 mmol of hydrated bismuth nitrate (Bi(NO ₃ ) ₃ ·5H ₂ O) in 60 mL of ethylene glycol, and slowly drop 10 mL of 0.1 mol/L NH ₄ F solution into it while stirring; The pH of the obtained mixed liquid was adjusted to 10, and after stirring for 30 min, the obtained liquid was transferred to a hydrothermal kettle, and then placed in a constant temperature drying oven at 200 ° C for 24 h; after the reaction liquid was cooled to room temperature, a 1000 r/min The obtained product was centrifuged at a rotating speed, and then the upper layer of turbid liquid was taken and continued to be centrifuged at 5000 r/min, and then dried to obtain BiOF nanosheets, as shown in FIG. 2 .

The SEM characterization results show that the plane size of the prepared BiOF nanosheets is below 3 μm and the thickness is below 300 nm.

2) Preparation of suspensions containing BiOF nanosheets

In a 250ml two-necked flask, 24g of lauryl methacrylate, 0.6g of hydroxypropyl methacrylate and 30g of toluene were uniformly mixed, and 2g of hexanethiol was added to the resulting mixed solution; The toluene solution was uniformly mixed with the above organic mixed solution, and under the protection of N ₂ , the polymerization reaction was carried out at 60 °C for 18 h to obtain a suspension medium with a viscosity of 1600 cp; 1 g of BiOF nanosheets were weighed and mixed with 19 g of the suspension In the medium, the mixed suspension medium was ultrasonically stirred for 10 min, and centrifuged for 2 min at a rotational speed of 2000 r/min to remove the incompletely dispersed particles in the lower layer to obtain a suspension containing BiOF nanosheets. The mass fraction of nanosheets is 5%.

3) Preparation of Light Valves Containing BiOF Nanosheets

Add spacer balls with a mass fraction of 3‰ and a diameter of 100μm to the obtained suspension, stir evenly; then take an appropriate amount of the suspension mixed with spacer balls, coat it between two layers of ITO conductive film, and use insulating glue to encapsulate the conductive film. Around the film, a simple SPD light valve was obtained.

As shown in Fig. 6, the light valve has a transmittance of 6% to light in the wavelength range of 200-800nm in the "OFF" state, and after applying a voltage of 200V to it, that is, in the "ON" state, its light The transmittance does not change significantly.

Comparative Example 2

This comparative example includes most of the operating steps of Example 1, except that the viscosity of the suspending medium is different. The specific preparation method is as follows:

1) Preparation of BiOF nanosheets

Dissolve 1 mmol of hydrated bismuth nitrate (Bi(NO ₃ ) ₃ ·5H ₂ O) in 60 mL of ethylene glycol, and slowly drop 10 mL of 0.1 mol/L NH ₄ F solution into it while stirring; The pH of the obtained mixed liquid was adjusted to 10, and after stirring for 30 min, the obtained liquid was transferred to a hydrothermal kettle, and then placed in a constant temperature drying oven at 200 ° C for 24 h; after the reaction liquid was cooled to room temperature, a 1000 r/min The obtained product was centrifuged at a rotating speed, and then the upper layer of turbid liquid was taken and continued to be centrifuged at 5000 r/min, and then dried to obtain BiOF nanosheets, as shown in FIG. 2 .

The SEM characterization results show that the plane size of the prepared BiOF nanosheets is below 3 μm and the thickness is below 300 nm.

2) Preparation of suspensions containing BiOF nanosheets

In a 250ml two-necked flask, 24g of lauryl methacrylate, 0.6g of hydroxypropyl methacrylate and 30g of toluene were uniformly mixed, and 0.5g of hexanethiol was added to the resulting mixed solution; 10g of toluene solution was uniformly mixed with the above-mentioned organic mixed solution, and under the protection of _N2 , polymerized at 60°C for 18h to obtain a suspension medium, the viscosity of which was 2500cp; 0.2g of BiOF nanosheets were weighed and mixed in 19.8g In the suspension medium, the mixed suspension medium was ultrasonically stirred for 10 minutes, and centrifuged for 2 minutes at a rotational speed of 2000 r/min to remove the incompletely dispersed particles in the lower layer to obtain a suspension containing BiOF nanosheets. The mass fraction of BiOF nanosheets in the liquid is 1%.

3) Preparation of Light Valves Containing BiOF Nanosheets

Add spacer balls with a mass fraction of 3‰ and a diameter of 100μm to the obtained suspension, stir evenly; then take an appropriate amount of the suspension mixed with spacer balls, coat it between two layers of ITO conductive film, and use insulating glue to encapsulate the conductive film. Around the film, a simple SPD light valve was obtained.

As shown in FIG. 7 , the light valve transmits only 6% of light in the wavelength range of 200-800 nm in the “OFF” state. After applying a voltage of 200V to it, that is, in the “ON” state, The transmittance of light only rises to 8%.

Embodiments 1-2 are light valves prepared by using BiOF nanosheets and BiOBr nanosheets as suspended particles respectively. The visible light transmittance is 5% in the closed state, and the visible light transmittance is 25-32% in the open state. The effect of adjusting the luminous flux is good. The light valve devices prepared in Comparative Example 1 and Comparative Example 2 have little change in visible light transmittance in the closed state and open state, and the luminous flux adjustment effect is poor. Among them, the mass fraction of BiOF nanosheets in the suspension of Comparative Example 1 is relatively high, which on the one hand leads to the waste of raw materials. The transmission of visible light; the viscosity of the suspension medium in the suspension of Comparative Example 2 is high, which is also not conducive to the inversion of the suspended particles of the nanosheets, and at the same time will cause the uneven distribution of BiOF nanosheets in the suspension medium, which will affect the light transmission of the light valve. uniformity.

To sum up, the light valve provided by the present invention has a visible light transmittance of about 5% in the closed state, and a visible light transmittance of 25-32% in the open state, which has a good effect of adjusting the luminous flux, and opens up a new field of bismuth oxyhalide nanosheets. It also expands the optional range of SPD light valve, and has good promotion and application value.

The present invention has been further described above with the help of specific embodiments, but it should be understood that the specific description herein should not be construed as a limitation on the spirit and scope of the present invention. Various modifications made in the embodiments all belong to the protection scope of the present invention.

Claims (10)

1. A light valve, characterized in that it comprises two layers of transparent electrodes and a light-adjusting layer sandwiched between the two layers of transparent electrodes, wherein the light-adjusting layer comprises a suspension in which oxyhalide is uniformly dispersed Suspended particles of bismuth nanosheets. 2 . The light valve according to claim 1 , wherein the plane size of the bismuth oxyhalide nanosheets is less than 4 μm, and the thickness is less than 300 nm. 3 . 3 . The light valve according to claim 1 , wherein the mass fraction of the bismuth oxyhalide nanosheets in the suspension is 0.05-4.0%. 4 . 4. A method for preparing a light valve as claimed in any one of claims 1 to 3, characterized in that it comprises the following steps: uniformly mixing the bismuth oxyhalide nanosheets with a suspending medium to obtain a suspension, and adding to the suspension spacer balls, and then encapsulate the suspension mixed with spacer balls between two layers of transparent electrodes to obtain the target device. 5 . The method for preparing a light valve according to claim 4 , wherein the bismuth oxyhalide nanosheets are prepared by a wet chemical method, and the wet chemical method is a hydrothermal method, a precipitation method, a microwave method or an interface method. 6 . Law. 6 . The method for preparing a light valve according to claim 4 , wherein the suspending medium is selected from at least one of siloxane, acrylic acid, and alkylene oxide monomers or polymers. 7 . 7 . The method for preparing a light valve according to claim 6 , wherein the viscosity of the suspension medium is less than 2000cp. 8 . 8 . The method for manufacturing a light valve according to claim 4 , wherein the size of the spacer ball is 10-200 μm. 9 . 9. The method for preparing a light valve according to claim 4, wherein the transparent electrode is selected from the group consisting of ITO conductive glass, ITO conductive film, nano-Ag wire conductive film, nano-Cu wire conductive film, PEDOT conductive film, graphite At least one of olefin conductive film and carbon nanotube conductive film. 10. Application of bismuth oxyhalide nanosheets in light valves.

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