Titanium dioxide coating as well as preparation method and application thereof

Abstract

The invention provides a titanium dioxide coating. The titanium dioxide coating is prepared from the following raw materials: 10-30 wt% of titanium dioxide, 10-30 wt% of a base material, 1-10 wt% of nano titanium dioxide, 1-10 wt% of a dispersant, 1-10 wt% of calcium titanate, 0-10 wt% of an auxiliary agent, 1-5 wt% of a pH regulator and 30-50 wt% of water. The invention further provides a preparation method of the titanium dioxide coating. The invention also provides a photovoltaic module. A coating layer formed by the titanium dioxide coating provided by the invention can form a titanium dioxide-based particle accumulation type diffuse reflection structure, so that the utilization effect of effective solar illumination at gaps of battery pieces can be enhanced, and the temperature coefficient of a photovoltaic module is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a titanium dioxide coating, a preparation method thereof, and an application thereof. Background Art

[0002] In the field of clean energy power generation, photovoltaic power generation is the power generation type with the greatest development potential and the lowest development ratio at present, and has great development potential. At present, the improvement of the efficiency of photovoltaic modules mainly focuses on the following aspects: 1) the improvement of the processing technology of battery chips; 2) the progress of the module packaging technology.

[0003] At the present stage, the processing technology of battery chips and the module packaging technology are becoming increasingly mature, and the performance optimization of photovoltaic modules often starts from the perspective of the structural design of module packaging. Research shows that sunlight passes through tempered glass and packaging materials (EVA or POE) and enters the gaps between the battery chips in the photovoltaic module and undergoes specular reflection. The sunlight is reflected outside the module or reaches the ground through the module. The gaps between the battery chips and between the battery chip strings occupy the effective light-receiving area of the photovoltaic cell module, but this gap cannot participate in energy conversion, resulting in the waste of the sunlight received by this part of the area and reducing the photoelectric conversion efficiency of the photovoltaic module. Therefore, how to make full use of the effective use area in the photovoltaic module and strengthen the utilization of the non-battery chip area in the photovoltaic module has become a top priority.

[0004] For the optimized utilization of the effective light-illuminated area of the gaps between the battery chips, currently, it mainly starts from two aspects: 1) the lamination and splicing technology of battery chips: Lamination and splicing are different from the way of using the light in the battery gaps in conventional modules. Splicing compresses or even overlaps the battery spacing to achieve the purpose of high-density and high-efficiency modules; lamination and splicing modules increase the arrangement density of battery chips in the unit light-receiving area by shortening the battery chip spacing to achieve high-density, high-power, and high-efficiency modules. However, reducing the battery chip spacing also abandons the light reflected by the gap light to the battery chips, and only generates electricity by the light irradiated on the battery chips, which results in the still not high enough photoelectric conversion efficiency of the lamination and splicing modules; 2) adding a diffuse reflection structure in the gaps between the battery chips of the photovoltaic module to make the sunlight irradiated on the battery gaps be secondarily reflected onto the battery chips through the diffuse reflection process, further enhancing the utilization of the gap light by the battery chips. Common diffuse reflection structures include: white high-reflection materials, white backsheets, and white encapsulant films or reflective films; the limitation of this solution is that the materials used to construct the diffuse reflection structure have a relatively low reflectivity to sunlight (the highest is about 85%), and there is still significant room for improvement; in addition, the high-reflection materials will also diffusely reflect the ultraviolet rays in the sunlight, and the diffusely reflected ultraviolet rays are incident on the battery chips or the backsheet, which will significantly affect the service life of the photovoltaic module. Therefore, the effective addition of a diffuse reflection structure in the gaps between the battery chips of the photovoltaic module is of great significance to the utilization efficiency of sunlight. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a titanium dioxide coating and a photovoltaic module. The photovoltaic module provided by the present application can effectively improve the utilization effect of effective sunlight at the gaps between the battery cells and reduce the temperature coefficient of the photovoltaic module.

[0006] In view of this, the present application provides a titanium dioxide coating, which is prepared from the following raw materials:

[0007]

[0008] Preferably, the titanium dioxide white pigment is selected from rutile-type nano-titanium dioxide and anatase-type nano-titanium dioxide with a mass ratio of (2-5):1, and the particle size is 10-20 nm.

[0009] Preferably, the base material is selected from one or more of polymer emulsions and water-soluble resins; the polymer emulsion is selected from one or more of styrene-acrylic copolymer emulsion, pure acrylate copolymer emulsion, and organosiloxane-acrylate copolymer emulsion, and the water-soluble resin is selected from one or more of polyvinyl alcohol, polyvinyl formal, and polyurethane prepolymer.

[0010] Preferably, the additives include defoamers, thickeners, leveling agents, film-forming aids, lithopone, and talcum powder.

[0011] Preferably, the defoamer is selected from a defoaming polymer and polysiloxane with a mass ratio of 1:(2-4), the dispersant is selected from sodium polyacrylate salt, the thickener is selected from anionic alkali-swellable polyacrylic acid, the leveling agent is selected from nonionic associative polyurethane, the film-forming aid is selected from diethylene glycol methyl ether, and the pH regulator is a sodium hydroxide solution with a pH value of 7.5-9.5.

[0012] The present application also provides a preparation method of the titanium dioxide coating, which includes the following steps:

[0013] Mix nano-titanium dioxide, titanium dioxide white pigment, and water according to the component ratio to obtain a mixed solution;

[0014] Add the base material, dispersant, calcium titanate, and additives to the mixed solution, and then add a pH regulator to adjust to alkaline to obtain the titanium dioxide coating.

[0015] Preferably, the nano-titanium dioxide and the titanium dioxide white pigment are ball-milled before preparing the mixed solution.

[0016] The present application also provides a photovoltaic module, which includes battery cells and pores between the battery cells. It is characterized in that the pores between the battery cells are coated with a coating having a particle-packed diffuse reflection structure, and the coating is formed by the titanium dioxide coating or the titanium dioxide coating prepared by the preparation method.

[0017] Preferably, the thickness of the coating is 80 - 150 μm.

[0018] Preferably, the porosity of the coating is 20 - 30%.

[0019] The present application provides a titanium dioxide coating, which is prepared from titanium dioxide white pigment, binder, nano-titanium dioxide, dispersant, calcium titanate, additives, pH regulator and water. The titanium dioxide coating provided by the present application can form a titanium dioxide-based particle-packed diffuse reflection structure.

[0020] The present application also provides a photovoltaic module, which includes solar cells and pores between the solar cells. The pores between the solar cells are coated with a coating having a particle-packed diffuse reflection structure, and the coating is formed from the above-mentioned titanium dioxide coating; the titanium dioxide-based particle-packed diffuse reflection structure follows the hexagonal closest packing configuration of the particles. The rich pore structure inside this structure provides a vast diffuse reflection interface for the sunlight incident on the photovoltaic module, enabling the sunlight to be re-incident into the interior of the solar cells after multiple diffuse reflections, enhancing the utilization effect of the photovoltaic module on the effective sunlight located at the gaps between the solar cells; the particle-packed diffuse reflection structure formed by the titanium dioxide coating can contribute to the effective reflection of the infrared band in the incident sunlight by the photovoltaic module, thereby reducing the operating temperature of the solar cells, that is, reducing the temperature coefficient of the photovoltaic module; nano-titanium dioxide can effectively absorb ultraviolet light in the sunlight, reducing the irradiation of ultraviolet light on the solar cells and the backsheet, and improving the service life of the photovoltaic module.

[0021] Furthermore, nano-titanium dioxide has excellent film-forming properties, a short normal-temperature curing time, and can form a smooth and flat film layer in a short period. It also has high chemical stability and thermal stability, with a service life of more than 20 years. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of the particle-packed diffuse reflection structure of the coating formed by the titanium dioxide coating of the present invention;

[0023] Figure 2 It is a schematic cross-sectional view of a photovoltaic module including a particle-packed diffuse reflection structure;

[0024] Figure 3 It is a schematic top view of a photovoltaic module including a particle-packed diffuse reflection structure;

[0025] Figure 4 It is a scanning electron microscope photograph of the film layer formed by the titanium dioxide coating. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0027] In view of the problem that the reflectivity of the diffuse reflection structure between solar cells in a photovoltaic module is still low in the prior art, the present application provides a titanium dioxide coating and a photovoltaic module. The coating formed by the titanium dioxide coating provided in the present application can form a titanium dioxide particulate accumulation type diffuse reflection structure, which can enhance the utilization effect of effective sunlight at the gap between solar cells and reduce the temperature coefficient of the photovoltaic module. Specifically, the embodiments of the present invention first disclose a titanium dioxide coating, which is prepared from the following raw materials:

[0028]

[0029] In the titanium dioxide coating provided in the present application, the titanium dioxide powder is specifically selected from rutile type nano-titanium dioxide and anatase type nano-titanium dioxide with a mass ratio of (2-5):1 and a particle size of 10-20 nm. More specifically, the titanium dioxide powder is selected from rutile type nano-titanium dioxide and anatase type nano-titanium dioxide with a mass ratio of (2.2-3.5):1. The content of the titanium dioxide powder is 10-30 wt%, specifically, the content of the titanium dioxide powder is 12-28 wt%, and more specifically, the content of the titanium dioxide powder is 15-20 wt%.

[0030] The base material is specifically selected from one or more of polymer emulsions and water-soluble resins. Specifically, the polymer emulsion is selected from one or more of styrene-acrylic copolymer emulsion, pure acrylate copolymer emulsion, and silicone-acrylate copolymer emulsion, and the water-soluble resin is selected from one or more of polyvinyl alcohol, polyvinyl formal, and polyurethane prepolymer. The content of the base material is 10-30 wt%, specifically, the content of the base material is 12-28 wt%, and more specifically, the content of the base material is 15-20 wt%.

[0031] The content of the nano-titanium dioxide is 1-10 wt%, specifically, the content of the nano-titanium dioxide is 2-8 wt%.

[0032] The dispersant is used to assist the uniform mixing of the nano-titanium dioxide and the base material, and its content is 1-10 wt%, specifically, the content of the dispersant is 3-7 wt%.

[0033] The content of the calcium titanate is 1-10 wt%, specifically, the content of the calcium titanate is 3-7 wt%.

[0034] The content of the auxiliary agent is 0-10 wt%, specifically, the content of the auxiliary agent is 2-8 wt%. The auxiliary agent may specifically include defoamer, thickener, leveling agent, film-forming auxiliary agent, lithopone and talcum powder. Among them, lithopone is used as a bonding auxiliary agent, and talcum powder can optimize the mechanical strength of the coating after film formation. The leveling agent promotes the formation of a flat, smooth and uniform coating film during the drying and film-forming process of the coating. The film-forming auxiliary agent can assist in film formation. The thickener can increase the viscosity of the coating, and the defoamer is used to reduce the surface tension and inhibit foam generation. More specifically, the content of the defoamer is 1-1.5 wt%, the content of the thickener is 1-1.5 wt%, the content of the leveling agent is 1-1.5 wt%, the content of the film-forming auxiliary agent is 1-1.5 wt%, the content of lithopone is 1-1.5 wt%, and the content of talcum powder is 1-1.5 wt%. The defoamer is specifically selected from a defoaming polymer and polysiloxane with a quantitative ratio of 1:(2-4). The dispersant is selected from sodium polyacrylate salt, the thickener is selected from anionic alkali-swellable polyacrylic acid, the leveling agent is selected from nonionic associative polyurethane, and the film-forming auxiliary agent is selected from diethylene glycol methyl ether.

[0035] The pH regulator adjusts the pH of the coating to alkaline, and it can specifically be selected from a sodium hydroxide solution with a pH value of 7.5-9.5. The content of the pH regulator is 1-5 wt%, specifically, the content of the pH regulator is 1-3 wt%.

[0036] The key component of the titanium dioxide coating provided by this application is titanium dioxide. During the drying and film-forming process, titanium dioxide particles will spontaneously deposit and form a particle accumulation structure.

[0037] This application also provides a preparation method of the titanium dioxide coating, including the following steps:

[0038] According to the component ratio, mix nano-titanium dioxide, titanium white powder and water to obtain a mixed solution;

[0039] Add the base material, dispersant, calcium titanate and auxiliary agent into the mixed solution, and then add a pH regulator to adjust to alkaline to obtain the titanium dioxide coating.

[0040] During the preparation process of the titanium dioxide coating, this application first mixes nano-titanium dioxide, titanium white powder and water to obtain a mixed solution. In the above process, before mixing with water, it also includes: ball-milling the nano-titanium dioxide and titanium white powder at a speed of 1000-1500 revolutions per minute for 20-30 min. The temperature of the mixing is 30-40 °C, and the time is 20-30 min.

[0041] This application then adds the base material, dispersant, calcium titanate and auxiliary agent into the above mixed solution, and stirs at 1000-1500 revolutions per minute at 30-50 °C for 30-60 min to obtain a mixture.

[0042] Finally, the obtained mixture above is adjusted to alkaline with a pH regulator to obtain a titanium dioxide coating.

[0043] This application also provides a photovoltaic module, which includes solar cells and pores between the solar cells. The pores between the solar cells are coated with a coating having a particulate-packed diffuse reflection structure, and the coating is formed from the titanium dioxide coating prepared above.

[0044] The schematic cross-sectional view of the photovoltaic module of this application is as Figure 2 shown. Among them, 1 is an aluminum alloy frame, 2 is tempered glass, 3 is encapsulation EVA film, 4 is a solar cell, 5 is encapsulation EVA film, 6 is tempered glass / backsheet, 7 is a particulate-packed diffuse reflection structure, where the particulate-packed diffuse reflection structure is the coating formed from the titanium dioxide coating. The particulate-packed diffuse reflection structure is specifically as Figure 1 shown; Figure 3 is the schematic top view of the solar cell module; The photovoltaic module provided by this application has the same structure as the photovoltaic module in the prior art, and the difference lies only in the setting of the coating in the pores between the solar cells. The titanium dioxide coating is coated in the pores between the solar cells, and this position can eliminate the influence of the titanium dioxide coating on the light-receiving area of the solar cell, and enhance the diffuse reflection process of visible light through the unique porous structure, thereby enhancing the absorption ability of the solar cell to visible light.

[0045] In the photovoltaic module, the thickness of the coating is 80 - 150 μm, and the porosity is 20 - 30%.

[0046] The coating formed by coating the titanium dioxide coating in the gaps between the solar cells of the photovoltaic module provided by this application can effectively scatter the infrared rays in the incident sunlight, reduce the absorption of infrared rays by the solar cell, thereby reducing the working temperature of the solar cell. In addition, the titanium dioxide coating structure can effectively reflect the ultraviolet rays in the incident sunlight, reduce the absorption of ultraviolet rays by the solar cell, thereby increasing the working life of the solar cell.

[0047] To further understand the present invention, the titanium dioxide coating and the photovoltaic module provided by the present invention will be described in detail below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0048] Example 1

[0049] By mass percentage, the titanium dioxide coating is prepared from the following components: deionized water 40%, titanium dioxide 20%, binder 20%, nano-titanium dioxide 5%, dispersant 4%, calcium titanate 4%, defoamer 1%, thickener 1%, leveling agent 1%, film-forming aid 1%, lithopone 1%, talc powder 1%, sodium hydroxide solution with pH of 8.0 1%;

[0050] Among them, the base material is a polyurethane prepolymer;

[0051] The titanium dioxide is a mixture of rutile-type nano-titanium dioxide and anatase-type nano-titanium dioxide, and the mass ratio of the two is 2.2:1; the particle size is a uniform particle size, about 10nm - 20nm;

[0052] The defoaming agent is a mixture of a foam-breaking polymer and polysiloxane, and the mass ratio of the two is 1:2;

[0053] The dispersant is sodium polyacrylate;

[0054] The thickening agent is an anionic alkali-swellable polyacrylic acid;

[0055] The leveling agent is a non-ionic associative polyurethane;

[0056] The film-forming aid is diethylene glycol methyl ether.

[0057] Preparation method of the titanium dioxide coating:

[0058] In a dust-free environment, the nano-titanium dioxide and titanium dioxide are placed in a ball mill and ball-milled at a rotation speed of 1200 revolutions per minute for 20 minutes. Deionized water is added to the mixed particles of the equidiameter and uniform mixture of nano-titanium dioxide and titanium dioxide, and stirred at a temperature of 35°C for 20 minutes to obtain a solution;

[0059] The base material, dispersant, calcium titanate, defoaming agent, leveling agent, film-forming aid, lithopone, and talc are respectively added to the mixed solution of titanium dioxide and titanium dioxide, and stirred at a rotation speed of 1000 revolutions per minute and a temperature of 35°C for 40 minutes;

[0060] The thickening agent is added to increase the Stormer viscosity of the slurry to about 100K, and a sodium hydroxide solution is added to make the pH of the slurry alkaline.

[0061] The titanium dioxide coating prepared above is used for Figure 2 the photovoltaic module shown, and the photovoltaic module is placed in an external environment (temperature: 32°C); in the photovoltaic module without the titanium dioxide inter-cell coating structure, the junction temperature of the crystalline silicon cell is 38.6°C. In contrast, in the photovoltaic module with the titanium dioxide inter-cell coating structure, the junction temperature of the crystalline silicon cell is 35.2°C.

[0062] Example 2

[0063] According to Figure 2 the structure shown, each part of the photovoltaic module is assembled to obtain a photovoltaic module, and the coating prepared in Example 1 is sprayed into the pores between the cells to form a titanium dioxide coating.

[0064] The titanium dioxide coating is prepared from the following components by mass percentage: deionized water 40%, titanium dioxide 20%, binder 20%, nano-titanium dioxide 5%, dispersant 4%, calcium titanate 4%, defoamer 1%, thickener 1%, leveling agent 1%, film-forming aid 1%, lithopone 1%, talc powder 1%, sodium hydroxide solution with pH of 8.0 1%;

[0065] Among them, the binder is a polyurethane prepolymer;

[0066] The titanium dioxide is a mixture of rutile nano-titanium dioxide and anatase nano-titanium dioxide, and the mass ratio of the two is 2.5:1; the particle size is a uniform particle size, about 10nm - 20nm;

[0067] The defoamer is a mixture of a foam-breaking polymer and polysiloxane, and the mass ratio of the two is 1:2;

[0068] The dispersant is sodium polyacrylate;

[0069] The thickener is an anionic alkali-swellable polyacrylic acid;

[0070] The leveling agent is a non-ionic associative polyurethane;

[0071] The film-forming aid is diethylene glycol methyl ether.

[0072] Preparation method of the titanium dioxide coating:

[0073] In a dust-free environment, the nano-titanium dioxide and titanium dioxide are placed in a ball mill and ball-milled at a speed of 1200 revolutions per minute for 25 minutes. Deionized water is added to the mixed particles of equidiameter and homogeneous mixing of nano-titanium dioxide and titanium dioxide, and stirred for 25 minutes at a temperature of 35°C to obtain a solution;

[0074] The binder, dispersant, calcium titanate, defoamer, leveling agent, film-forming aid, lithopone, and talc powder are respectively added to the mixed solution of titanium dioxide and titanium dioxide, and stirred at 1500 revolutions per minute and a temperature of 40°C for 50 minutes;

[0075] The thickener is added to increase the Stormer viscosity of the slurry to about 100K, and the sodium hydroxide solution is added to make the pH of the slurry alkaline.

[0076] The scanning electron microscope photograph of the film layer formed by applying the coating prepared in this example on a glass slide is as Figure 4 shown. The key component of the titanium dioxide coating is titanium dioxide. During the drying and film-forming process, the titanium dioxide particles will spontaneously deposit and form a particle accumulation structure.

[0077] The prepared titanium dioxide coating is used for Figure 2The photovoltaic module shown is placed in an external environment (temperature: 30 °C). In the photovoltaic module without the titanium dioxide inter-cell coating structure, the junction temperature of the crystalline silicon cell is 35.6 °C. In contrast, in the photovoltaic module with the titanium dioxide inter-cell coating structure, the junction temperature of the crystalline silicon cell is 32.8 °C.

[0078] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0079] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A titanium dioxide coating is prepared from the following raw materials:

2. The titanium dioxide coating according to claim 1, characterized in that, The titanium dioxide is selected from rutile-type nano-titanium dioxide and anatase-type nano-titanium dioxide with a mass ratio of (2-5):1, and the particle size is 10-20 nm.

3. The titanium dioxide coating according to claim 1, characterized in that, The base material is selected from one or more of polymer emulsions and water-soluble resins; the polymer emulsion is selected from one or more of styrene-acrylic copolymer emulsion, pure acrylate copolymer emulsion, and silicone-acrylate copolymer emulsion, and the water-soluble resin is selected from one or more of polyvinyl alcohol, polyvinyl formal, and polyurethane prepolymer.

4. The titanium dioxide coating according to claim 1, wherein, The additives include defoamers, thickeners, leveling agents, film-forming aids, lithopone, and talc powder.

5. The titanium dioxide coating according to claim 4, characterized in that, The defoamer is selected from a defoaming polymer and polysiloxane with a mass ratio of 1:(2-4), the dispersant is selected from sodium polyacrylate salt, the thickener is selected from anionic alkali-swellable polyacrylic acid, the leveling agent is selected from non-ionic associative polyurethane, the film-forming aid is selected from diethylene glycol methyl ether, and the pH regulator is a sodium hydroxide solution with a pH value of 7.5-9.

5.

6. The preparation method of the titanium dioxide coating according to claim 1, comprising the following steps: Mix nano-titanium dioxide, titanium dioxide, and water according to the component ratio to obtain a mixed solution; Add the base material, dispersant, calcium titanate, and additives to the mixed solution, and then add a pH regulator to adjust to alkaline to obtain the titanium dioxide coating.

7. The preparation method according to claim 6, characterized in that, The nano-titanium dioxide and the titanium dioxide are ball-milled before preparing the mixed solution.

8. A photovoltaic module, comprising solar cells and pores between the solar cells, characterized in that, The pores between the battery cells are coated with a coating having a particle-packed diffuse reflection structure, and the coating is formed by the titanium dioxide coating according to any one of claims 1-5 or the titanium dioxide coating prepared by the preparation method according to any one of claims 6-7.

9. The photovoltaic module according to claim 8, characterized in that, The thickness of the coating is 80-150 μm.

10. The photovoltaic module according to claim 8, characterized in that, The porosity of the coating is 20-30%.

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