An optical polymer, method of use, battery sheet, photovoltaic module and photovoltaic system

Abstract

The application is suitable for the technical field of photovoltaic modules, and provides an optical polymer, an application method, a cell, a photovoltaic module and a photovoltaic system.The optical polymer comprises, by weight, 20-50 parts of a photocuring oligomer, 30-60 parts of a photocuring monomer, 20-70 parts of high-refractive nanoparticles, 0.5-10 parts of a nanodispersion agent, 1-10 parts of a photoinitiator system and 0.1-5 parts of an auxiliary agent.The viscosity of the optical polymer is 8-25 mPa·s at a temperature of 40-60 degrees Celsius, and the refractive index of a cured film formed after curing of the optical polymer is 1.60-1.75 at a wavelength of 600 nm.Due to the synergistic effect of the specific sulfur-containing or high-refractive monomer and the surface-modified nanoparticles used in the optical polymer, the refractive index of the cured film formed after curing is 1.60-1.75 under irradiation at a wavelength of 600 nm, thus effectively matching the refractive index difference between the encapsulation adhesive film and the cell antireflection film, reducing the interface reflection loss, optimizing the light transmission, reducing the reflection loss at the interface between the encapsulation adhesive film and the cell antireflection film, and thus improving the efficiency of the photovoltaic module.

Description

Technical Field This invention belongs to the field of photovoltaic module technology, and particularly relates to an optical polymer, application method, solar cell, photovoltaic module and photovoltaic system. Background Technology In the field of photovoltaic technology, the photoelectric conversion efficiency of solar modules is a core performance indicator, and optical loss during light transmission is one of the key factors restricting efficiency improvement. In the existing encapsulation structure of solar modules, light needs to pass through glass and encapsulation film (such as EVA and POE) in sequence before reaching the solar cell. The refractive index of the encapsulation film is usually about 1.48, while the refractive index of the silicon nitride antireflective film on the light-receiving surface of the solar cell is as high as 1.9-2.0, and there is a significant difference in refractive index between the two.

[0003] In existing technologies, optical loss is mainly reduced by optimizing the encapsulation film formulation, improving the anti-reflective film preparation process, or adjusting the component encapsulation structure. For example, some solutions attempt to develop high-refractive-index encapsulation films to narrow the refractive index difference with the anti-reflective film, while others optimize the optical matching effect by increasing the number of anti-reflective film layers.

[0004] However, adopting the above-mentioned solutions leads to problems such as high material costs and insufficient weather resistance in the development of high-refractive-index encapsulating films, making it difficult to meet the cost-effectiveness requirements for large-scale mass production. Multilayer anti-reflective coating processes increase the complexity and production cost of battery cell fabrication and significantly impact production efficiency. More importantly, to achieve a high refractive index (n>1.6), a large amount of inorganic nanoparticles (such as zirconium dioxide) are usually added to the polymer, which causes a sharp increase in system viscosity, making it unsuitable for the rheological requirements of non-contact digital printing (typically requiring viscosity <20 cP). Existing high-refractive-index coatings are mostly high-viscosity pastes that can only be applied via screen printing. Furthermore, as battery cell technology moves towards thinner wafers (such as HJT, TOPCon, and BC batteries), traditional contact coating printing processes (such as screen printing and wheel coating) are prone to causing microcracks or fragmentation of the battery cells. Therefore, there is an urgent need for a material and supporting method that can achieve both high refractive index and low viscosity while meeting the requirements of non-contact precision coating printing (such as non-contact digital printing). Summary of the Invention

[0005] The present invention provides an optical polymer, an application method, a solar cell, a photovoltaic module, and a photovoltaic system, which aims to solve the technical problem that existing high-refractive-index optical materials for solar cells are difficult to apply to non-contact digital printing processes.

[0006] The present invention is implemented as follows: an optical polymer suitable for non-contact digital printing of photovoltaic cells. The optical polymer comprises, by weight, 20-50 parts of photocurable oligomer, 30-60 parts of photocurable monomer, 20-70 parts of high refractive index nanoparticles, 0.5-10 parts of nano-dispersant, 1-10 parts of photoinitiator system, and 0.1-5 parts of additives. The optical polymer has a viscosity of 8-25 mPa·s at a temperature of 40-60 degrees Celsius, and the refractive index of the cured film formed after curing is 1.60-1.75 at a wavelength of 600 nm.

[0007] Furthermore, the photocurable oligomer comprises polyurethane acrylate, epoxy acrylate, or polyester acrylate, or a combination thereof, and the ratio of the photocurable monomers is configured to adjust the viscosity of the optical polymer to meet the requirements of non-contact digital printing; the photocurable monomers are selected from at least one of sulfur-containing acrylate monomers, o-phenylphenoxyethyl acrylate (OPPEA), 2-phenylphenol acrylate, or bisphenol A epoxy acrylate, to provide a high refractive index at low viscosity at at least one of sulfur-containing acrylate monomers, o-phenylphenoxyethyl acrylate (OPPEA), 2-phenylphenol acrylate, or bisphenol A epoxy acrylate; The high-refractive-index nanoparticles include one or more of the following: nano-zirconia, nano-hafnium oxide, nano-titanium dioxide, nano-zinc sulfide, or nano-zinc sulfide, which have been modified with a surface silane coupling agent or the nano-dispersant, and have a particle size of 10-50 nm; the nano-dispersant includes a copolymer dispersant containing acidic groups, wherein the acidic groups are selected from phosphate ester groups, carboxyl groups, or sulfonic acid groups; The photoinitiator system is a combination of acylphosphine oxide photoinitiators and α-hydroxyketone photoinitiators; The additives include silane coupling agents, leveling agents, and defoamers.

[0008] A method for applying an optical polymer, the method comprising: The optical polymer described in any of the above items is coated and printed onto the light-receiving surface of the battery cell using non-contact digital printing technology; The solar cell coated with the printed optical polymer is pre-cured to allow the optical polymer to be in a semi-cured state for pinning and shaping. The pre-cured battery cell is then subjected to primary curing to fully crosslink the optical polymer.

[0009] Furthermore, the optical polymer is coated onto the light-receiving surface of the battery cell using a single or multiple non-contact digital printing technique, and the optical polymer forms a cured film with a thickness of 3-20 μm on the battery cell.

[0010] Furthermore, when the battery cell is pre-cured, a low-intensity ultraviolet light source is used to irradiate the battery cell. The irradiation intensity is 50-300mW / cm², the irradiation time is 0.2-2 seconds, and the cumulative irradiation energy is 10-600mJ / cm². During the primary curing of the solar cells, the solar cells are irradiated with a high-intensity UV lamp with an irradiation intensity greater than 800mW / cm² and a cumulative irradiation energy of 800-3000mJ / cm².

[0011] Furthermore, before coating and printing the optical polymer, the optical polymer is heated to 40-60 degrees Celsius to maintain its viscosity in the range of 8-25 mPa·s.

[0012] Furthermore, before coating and printing the optical polymer according to any one of claims 1-2 onto the light-receiving surface of the solar cell, the method further includes: The light-receiving surface of the solar cell is subjected to surface energy modification treatment, which includes at least one of plasma treatment, corona treatment, flame treatment, or solvent cleaning, so that the surface energy of the solar cell surface is sufficient to meet the wetting requirements.

[0013] A battery cell, wherein the light-receiving surface of the battery cell is covered with a cured film formed by curing the optical polymer described in any one of the above claims.

[0014] A photovoltaic module includes a first light-transmitting substrate, a first encapsulating film, a battery string, a second encapsulating film, and a second encapsulating substrate arranged sequentially along the light incident direction, wherein the battery string is composed of a plurality of the aforementioned battery cells.

[0015] A photovoltaic system comprising the photovoltaic modules described above.

[0016] The beneficial effects achieved by this invention are as follows: due to the use of low-viscosity, high-refractive-index monomers and specific nano-dispersion technology in the optical polymer, the high-load nanoparticle system maintains the low viscosity characteristics required for inkjet printing, while the cured film formed after curing has a refractive index of 1.60-1.75 under 600nm wavelength irradiation. This effectively matches the refractive index difference between the encapsulation film and the battery antireflection film, reduces interface reflection loss, and has the advantages of providing a cured film with a specific refractive index, optimizing light transmission, reducing reflection loss at the interface between the encapsulation film and the battery antireflection film, thereby improving the efficiency of photovoltaic modules. Attached Figure Description

[0017] Figure 1 This is an exploded view of the photovoltaic module provided in an embodiment of the present invention; Figure 2 This is a schematic flowchart of the application method of the optical polymer provided in the embodiments of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] In existing technologies, optical losses are mainly reduced by optimizing the encapsulating film formulation, improving the anti-reflective film preparation process, or adjusting the module encapsulation structure. For example, some solutions attempt to develop high-refractive-index encapsulating films to narrow the refractive index difference with the anti-reflective film, while others optimize the optical matching effect by increasing the number of anti-reflective film layers. However, adopting these solutions leads to problems such as high material costs and insufficient weather resistance in the development of high-refractive-index encapsulating films, making it difficult to meet the cost-effectiveness requirements for large-scale mass production. Multilayer anti-reflective film processes increase the complexity and production cost of solar cells and have a significant impact on production efficiency. More importantly, existing technologies lack a solution specifically for precise optical matching between the encapsulating film and the solar cell anti-reflective film interface, failing to fundamentally solve the 2%–4% optical reflection loss problem at this interface, while also making it difficult to meet the core needs of the photovoltaic industry for high-throughput, low-cost, and simplified production processes. The cured film formed by the curing of the optical polymer has a refractive index of 1.60-1.75 under 600nm wavelength irradiation. This effectively matches the refractive index difference between the encapsulation film and the antireflective film of the battery, reducing interface reflection loss. It has the advantage of being able to provide a cured film with a specific refractive index, optimizing light transmission, reducing reflection loss at the interface between the encapsulation film and the antireflective film of the battery, thereby improving the efficiency of photovoltaic modules.

[0020] Example 1 Please see Figures 1 to 2 The present invention is implemented as follows: an optical polymer, the cured film 3002 formed after curing has a refractive index of 1.60-1.75 under irradiation at a wavelength of 600nm.

[0021] Optical polymer refers to a material system used to form optically cured film 3002. In this embodiment, cured film 3002 refers to the liquid film state of the optical polymer before it is cured after being sprayed onto the surface of the substrate. Its components are designed to exhibit specific optical properties after curing. In this embodiment, the optical polymer is a material system in which the refractive index is controlled at a specific wavelength.

[0022] Curing refers to the process by which optical polymers undergo a chemical reaction under specific conditions (such as light, heating, etc.) to transform from a liquid or semi-solid state into a solid state with stable physicochemical properties.

[0023] Cured film 3002 refers to a thin film formed on the surface of a substrate after the optical polymer is cured. This film has specific optical functions. Specifically, it is a solid film with a stable three-dimensional cross-linked network formed on the surface of the substrate.

[0024] The refractive index is the ratio of the sine of the incident angle to the sine of the refraction angle when light is refracted at the interface between two media. It is a physical quantity that measures the optical density of a material.

[0025] A wavelength of 600 nm refers to a specific wavelength in the visible light region of the electromagnetic spectrum, and is often used to evaluate the optical properties of materials under specific lighting conditions.

[0026] Specifically, optical polymers can be composed of multiple components, such as one or more resins, one or more active monomers, one or more additives, and one or more initiators. These components are prepared into a uniform liquid or slurry form by mixing, grinding, dispersing, etc., to facilitate subsequent coating and printing operations.

[0027] Furthermore, after curing, the optical polymer forms a cured film 3002 with specific optical properties on the surface of the substrate. The curing process can be achieved in various ways, such as by ultraviolet light irradiation, electron beam irradiation or thermal curing. During the curing process, the reactive components in the optical polymer undergo cross-linking reaction, thereby forming a stable polymer network structure, which endows the cured film 3002 with the required mechanical strength and optical properties.

[0028] Specifically, the refractive index of the cured film 3002 is 1.60-1.75 under irradiation at a wavelength of 600 nm. To achieve this specific refractive index range, the formulation of the optical polymer needs to be carefully designed. For example, the refractive index of the final cured film 3002 can be controlled by selecting matrix materials with different refractive indices for mixing, or by adjusting the proportions of the components in the optical polymer. In practical applications, the refractive index of the cured film 3002 at a wavelength of 600 nm is mainly measured using an ellipsometer to verify whether its refractive index meets the requirements. For example, various optical polymers with different formulations can be prepared, cured separately, and their refractive indices measured to screen out the formulation that meets the refractive index range of 1.60-1.75.

[0029] Furthermore, since the cured film 3002 formed after curing has a refractive index of 1.60-1.75 at a wavelength of 600nm, the cured film 3002 can effectively fill the refractive index difference between the encapsulating film and the antireflective film of the solar cell 3001 in the solar module, thereby significantly reducing the reflection loss of light at the interface. This improves the light transmission efficiency and thus enhances the photoelectric conversion efficiency of the solar module. At the same time, it provides the photovoltaic industry with a cost-effective and simplified solution.

[0030] It should be noted that, in this embodiment, by setting the curing film 3002, the light interface reflection loss in the photovoltaic module 10 can be reduced by more than 50%, and the photovoltaic module 10 can be given a power gain of 0.1% to 0.3%. In addition, the curing film 3002 also has excellent adhesion and weather resistance, and can provide mechanical protection for the light-receiving surface of the attached solar cell 3001. The structure is simple and easy to implement.

[0031] Preferably, in this embodiment of the invention, the optimal refractive index of the cured film 3002 after the optical polymer is cured is 1.65-1.7. Of course, in other embodiments, other refractive indices can also be used. The specific design can be based on the actual situation and is not limited here.

[0032] It should be noted that in other embodiments, the refractive index can be between 1.60 and 1.75. This range is based on experimental results of balancing the loading of high-refractive-index nanoparticles with polymer viscosity. If the refractive index is below 1.60, the optical gain is not significant; if it is above 1.75, extremely high nanoparticle loading is usually required, which would lead to a sharp increase in viscosity and fail to meet the requirements of non-contact digital printing.

[0033] Example 2 Furthermore, the optical polymer comprises, by weight: 20-50 parts of photocurable oligomer, 30-60 parts of photocurable monomer, 20-70 parts of high refractive index nanoparticles, 0.5-10 parts of nano-dispersant, 1-10 parts of photoinitiator system, and 0.1-5 parts of additives.

[0034] Specifically, the photocurable oligomer, as the main film-forming substance of the optical polymer, has a content range of 20-50 parts. It is intended to provide the basic framework and mechanical properties of the cured film 3002. This range ensures sufficient film-forming substance to form a continuous cured film 3002 with good mechanical strength, while avoiding excessive viscosity of the optical polymer due to excessive oligomer content, which would affect subsequent coating and printing operations, or insufficient performance of the cured film 3002 due to insufficient content.

[0035] The photocurable monomer, acting as an active diluent, is present in a concentration of 30-60 parts. It is used to adjust the viscosity of the optical polymer, ensuring a low viscosity of 8-25 mPa·s at inkjet temperatures of 40-60 degrees Celsius. This results in good rheological properties and flowability, providing excellent non-contact digital printing jet stability during coating and printing. It also promotes the curing reaction of the oligomer, influencing the crosslinking density and hardness of the cured film 3002. This formulation range ensures sufficient crosslinking density while maintaining good flowability of the optical polymer, contributing to the formation of a uniform and stable cured film 3002. Specifically, to maintain low viscosity while introducing a large number of high-refractive-index nanoparticles, the photocurable monomer preferably comprises a high-refractive-index, low-viscosity monomer, such as o-phenylphenoxyethyl acrylate (OPPEA) or 2-phenylphenol acrylate. These monomers themselves have a high refractive index (typically n>1.55), effectively diluting the oligomer and high-solids-content nano-pigment without sacrificing, or even increasing, the overall refractive index.

[0036] The content of high-refractive-index nanoparticles ranges from 20 to 70 parts. Their main function is to significantly increase the refractive index of the cured film 3002 after curing, while maintaining the transparency of the cured film 3002. The nano-sized particles help reduce light scattering and ensure the optical clarity of the cured film 3002. This content range allows for precise adjustment of the refractive index of the cured film 3002 to the target range without sacrificing transparency and processability. If the content is too low, the increase in refractive index will not be significant; if the content is too high, it may lead to difficulties in nanoparticle dispersion, excessively high optical polymer viscosity causing inkjet head clogging, and decreased transparency of the cured film or cured film 3002. The content of nano-dispersant ranges from 0.5 to 10 parts, which is crucial for achieving stable dispersion of high-loading nanoparticles in organic resins. In this embodiment, a block copolymer containing acidic groups (such as phosphate ester groups or carboxyl groups) is preferably used as a dispersant. These acidic groups can form strong chemical bonds with the metal hydroxyl groups on the surface of nanoparticles (such as zirconium oxide), while the solvated segments of the copolymer extend into the monomers and oligomers to provide steric hindrance, thereby effectively preventing nanoparticle aggregation and significantly reducing the viscosity of the system. This allows the optical polymer to maintain a low viscosity (<25 cP) suitable for inkjet printing, even at high nanoparticle loadings (such as 50-70 parts).

[0037] The content range of the photoinitiator system is 1-10 parts. Its function is to absorb light energy of a specific wavelength, generate active free radicals or cations, thereby initiating a photocuring reaction, which enables the oligomer and monomer to crosslink and cure rapidly. This content range ensures sufficient photoinitiation efficiency, enabling the optical polymer to achieve rapid surface shaping in the pre-curing stage after non-contact digital printing, and to cure rapidly under the light conditions in the main curing stage, forming a stable cured film 3002 structure. At the same time, it avoids problems such as yellowing of the cured film 3002 or incomplete curing that may be caused by excessive initiator.

[0038] The content of the additive ranges from 0.1 to 5 parts. It is used to improve the processing performance of optical polymers, the quality of cured film 3002 and long-term stability. For example, the additive can improve the leveling and defoaming properties of optical polymers and enhance the adhesion between cured film 3002 and substrate. A small amount of additive can play a significant role, while avoiding the negative impact of excessive additive on optical or curing performance.

[0039] In this embodiment, by strictly controlling the weights of the photocurable oligomer, photocurable monomer, high-refractive-index nanoparticles, nano-dispersant, photoinitiator system, and additives, the refractive index of the cured film 3002 after the optical polymer is cured can be precisely controlled, stabilizing it within the range of 1.60-1.75, thereby meeting specific optical performance requirements. Simultaneously, this formulation optimizes the rheological properties of the optical polymer, ensuring good flowability and spreadability during the coating and printing process, effectively avoiding defects in the cured film 3002, and improving the uniformity and efficiency of coating and printing. Furthermore, an appropriate amount of photoinitiator system ensures efficient and thorough curing, resulting in a cured film 3002 with excellent optical properties and mechanical stability. This significantly improves the implementation effect and reliability of the overall technical solution, solving the problem that limiting only the refractive index makes it difficult to guarantee overall performance and process stability.

[0040] Example 3 Furthermore, the photocurable oligomer includes polyurethane acrylate, epoxy acrylate, or polyester acrylate, or combinations thereof, and the ratio of the photocurable monomers is configured to adjust the viscosity of the optical polymer to meet the requirements of non-contact digital printing; the photocurable monomers are selected from at least one of sulfur-containing acrylate monomers, o-phenylphenoxyethyl acrylate (OPPEA), 2-phenylphenol acrylate, or bisphenol A epoxy acrylate to provide a high refractive index at low viscosity at at least one of sulfur-containing acrylate monomers, o-phenylphenoxyethyl acrylate (OPPEA), 2-phenylphenol acrylate, or bisphenol A epoxy acrylate; High refractive index nanoparticles include one or more of the following: nano-zirconia, nano-hafnium oxide, nano-titanium dioxide, nano-zinc sulfide, or nano-zinc sulfide, which have been surface-modified with a silane coupling agent or a nano-dispersant, and have a particle size of 10-50 nm; the nano-dispersant includes copolymer dispersants containing acidic groups, wherein the acidic groups are selected from phosphate ester groups, carboxyl groups, or sulfonic acid groups; The photoinitiator system is a combination of acylphosphine oxide photoinitiators and α-hydroxy ketone photoinitiators; Additives include silane coupling agents, leveling agents, and defoamers.

[0041] In this embodiment, polyurethane acrylate typically provides excellent flexibility and abrasion resistance; epoxy acrylate has good hardness and chemical resistance; and polyester acrylate combines good flexibility and cost-effectiveness. By selecting one or more of polyurethane acrylate, epoxy acrylate, or polyester acrylate and strictly controlling their molecular weight, adjustments can be made according to the required overall performance of the cured film 3002 and the viscosity requirements of non-contact digital printing to meet the needs of different application scenarios.

[0042] Preferably, o-phenylphenoxyethyl acrylate (OPPEA) is selected as the main monomer. OPPEA not only has extremely low viscosity (<10 cP), but also has a high refractive index (n≈1.57) due to the presence of two benzene rings in its molecular structure. When combined with high-refractive-index nanoparticles, compared to using ordinary monomers (such as IBOA, n≈1.47), a higher final refractive index can be obtained with the same nanoparticle loading, or the amount of nanoparticles can be reduced to achieve the same target refractive index, thereby improving the rheological properties and stability of the system. Nano-zirconia, nano-hafnium oxide, and nano-titanium dioxide or nano-zinc sulfide are all common high-refractive-index inorganic materials that can significantly improve the overall refractive index of the cured film 3002. To ensure good dispersion of nanoparticles in the organic matrix, avoid agglomeration, and maintain the optical transparency of the cured film 3002, these nanoparticles need to be surface-modified with a silane coupling agent or the aforementioned nano-dispersant to enhance their compatibility with the organic resin. Controlling the particle size within the range of 10-50 nm can effectively reduce light scattering, ensure excellent transparency of the cured film 3002, and prevent nanoparticle sedimentation, thereby improving the storage stability of the optical polymer. In other embodiments, the particle size can also be other values. For example, in one example, the particle size is controlled at 20-60 nm; in another embodiment, the particle size is controlled at 30-60 nm. The specific design can be tailored to the actual situation and is not limited here.

[0043] Employing a composite initiator system, particularly the combination of TPO and 1173, enables more efficient and thorough curing. TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) is a highly efficient pyrolysis initiator with excellent absorption in the UV-A band, suitable for deep curing. 1173 (2-hydroxy-2-methyl-1-phenylpropane-1-one) is a highly efficient free radical initiator with excellent absorption in the UV-C and UV-B bands, suitable for surface curing. The synergistic effect of both ensures rapid and uniform curing of optical polymers under varying thicknesses and light sources, improving curing efficiency and the performance of the cured film. TPO's long-wavelength absorption characteristics make it particularly suitable for pre-curing (pinning) processes under LED light sources, facilitating rapid droplet shape locking.

[0044] Silane coupling agents enhance the interfacial bonding between high-refractive-index nanoparticles and the organic matrix, improving the adhesion, mechanical strength, and water resistance of the cured film 3002, while also contributing to the dispersion stability of the nanoparticles. Leveling agents improve the leveling properties of the cured film 3002, eliminating surface defects such as brush marks and sagging, resulting in a smooth and uniform surface. Defoamers effectively suppress and eliminate bubbles generated during the preparation and coating / printing process of the optical polymer, preventing pinholes and bubbles from appearing in the cured film 3002 after curing, thus ensuring the optical uniformity and integrity of the cured film 3002.

[0045] 1173 (2-hydroxy-2-methyl-1-phenylpropiophenone) is a commonly used free radical photoinitiator widely applied in ultraviolet (UV) curing systems. Its main function is to undergo homolytic cleavage upon absorbing UV light, generating highly reactive free radicals that initiate the polymerization of unsaturated monomers or oligomers such as acrylates, enabling rapid curing of coatings, inks, adhesives, or photovoltaic encapsulation materials. 1173 possesses advantages such as moderate absorption wavelength (main peak approximately 240–330 nm), high initiation efficiency, low yellowing, and good compatibility with various resins. In UV curing processes such as antireflective coatings for photovoltaic modules and encapsulation films, it is often used to promote the formation of cross-linked networks, improving the adhesion, hardness, and durability of the coating. At room temperature, it is a colorless to slightly yellow transparent liquid; at low temperatures, it can crystallize.

[0046] This setup, through the careful selection of specific types of photocurable oligomers and monomers, provides a stable film-forming framework and adjustable viscosity for the optical polymer, ensuring excellent processing performance and post-curing mechanical properties. Simultaneously, the introduction of high-refractive-index nanoparticles of a specific particle size, modified with a surface silane coupling agent or the aforementioned nano-dispersant, effectively enhances the refractive index of the cured film 3002 while maintaining excellent optical transparency. The addition of the nano-dispersant solves the problem of a sharp increase in viscosity caused by high-concentration nanoparticles, enabling low-viscosity inkjet printing with high solids content. The use of a composite photoinitiator system significantly improves curing efficiency and depth, ensuring rapid and thorough curing of the cured film 3002. Furthermore, the addition of various additives further optimizes the rheological properties, adhesion, and surface quality of the cured film 3002, effectively avoiding defects such as bubbles, sagging, or over-spreading.

[0047] Example 4 Please see Figure 1 and Figure 2 An application method for an optical polymer, the application method comprising: Step S10: Apply any of the above-mentioned optical polymers to the light-receiving surface of the solar cell 1003 using non-contact digital printing technology; Step S20: Pre-curing the solar cell 3001 coated with the printed optical polymer to make the optical polymer in a semi-cured state for pinning and shaping; Step S30: Perform primary curing on the pre-cured battery cell 3001 to fully crosslink the optical polymer.

[0048] In this embodiment, by combining the coating and printing process of optical polymer with step-by-step curing technology, the optical polymer is first pre-cured to form a stable intermediate layer on the surface of the battery cell 3001, and then the main curing is used to complete the cross-linking, thereby accurately constructing an optical transition layer with a refractive index matching at the interface between the encapsulation film and the battery anti-reflection film.

[0049] In this way, by utilizing the refractive index characteristics of 1.60-1.75 after the optical polymer is cured, the gradient difference between the encapsulation film (refractive index of about 1.48) and the antireflective film (refractive index of 1.9-2.0) is effectively reduced.

[0050] Because the pre-curing process controls the optical polymer to be shaped but not completely cross-linked, it avoids uneven thickness or interface defects caused by fluidity during the coating and printing process. The main curing ensures that the cured film 3002 is fully cured to achieve stable optical performance. At the same time, the application of the optical polymer in this embodiment not only eliminates optical reflection loss at the interface and significantly improves light transmission efficiency, but also avoids the material cost problems of developing high refractive index encapsulating films and the complexity of multilayer antireflective film processes. While ensuring improved photoelectric conversion efficiency, it simplifies the production process, meets the core needs of the photovoltaic industry for high-throughput and low-cost manufacturing, and is easy to operate, which is beneficial to users.

[0051] Example 5 Furthermore, the optical polymer is coated onto the light-receiving surface of the solar cell 3001 using a single or multiple non-contact digital printing technique, forming a cured film 3002 with a thickness of 3-20 μm on the solar cell 3001.

[0052] Specifically, non-contact digital printing technology is a non-contact digital precision coating printing method. Non-contact digital printing technology can achieve precise control over the coating printing area, coating printing thickness, and coating printing pattern, ensuring that the thickness deviation of the cured film 3002 after curing is less than ±0.5%, avoiding material overflow or unevenness that may occur in traditional coating printing methods.

[0053] Furthermore, in the use of inkjet technology, non-contact digital printing systems typically include one or more inkjet heads, each of which integrates multiple micro-nozzles. By precisely controlling the switching frequency, jet voltage, and jet time of the nozzles, the size and jet volume of the droplets can be adjusted. At the same time, by adjusting the relative movement speed and printing path between the inkjet head and the battery cell 3001, uniform coverage of the entire surface of the battery cell 3001 or patterned coating printing of specific areas can be achieved.

[0054] In this embodiment, by employing non-contact digital printing technology, an optical polymer can be precisely formed on the battery cell 3001 into a cured film 3002 with a thickness of 3-20 μm. The thickness range of the cured film 3002 is optimized to ensure that the cured film 3002 provides the best optical performance, such as achieving a refractive index of 1.60-1.75 at a wavelength of 600 nm, while ensuring the mechanical strength and adhesion of the cured film 3002. The precise control of the thickness of the cured film 3002 is achieved by comprehensively adjusting the non-contact digital printing system, such as adjusting the inkjet head's ejection frequency, ejection volume, printing speed, and number of print passes. In addition, the rheological properties of the optical polymer itself, such as viscosity and surface tension, must also be matched with the printing process to ensure that the droplets can be stably ejected and spread into a uniform cured film 3002.

[0055] Thus, by employing non-contact digital printing technology to coat optical polymers, precise control over the thickness of the cured film 3002 can be achieved. This ensures the formation of a uniformly thick cured film 3002 on the surface of the solar cell 3001, within the range of 1-50 μm. This high-precision coating printing method significantly reduces material waste, lowers production costs, and improves production efficiency. More importantly, the precise thickness of the cured film 3002 lays the foundation for subsequent curing to form a cured film 3002 with stable optical properties (such as a refractive index of 1.60-1.75 at a wavelength of 600 nm). This effectively improves the light capture efficiency and photoelectric conversion performance of the solar cell 3001. Furthermore, as a non-contact process, non-contact digital printing avoids the risk of mechanical damage to the surface of the solar cell 3001, further ensuring product quality and reliability.

[0056] In this embodiment, non-contact digital printing technology is used to coat and print the optical polymer onto the light-receiving surface of the battery cell 3001. Of course, in other embodiments, non-non-contact digital printing technology can also be used to coat and print the optical polymer onto the light-receiving surface of the battery cell 3001. For example, in one embodiment, electrohydrodynamic non-contact digital printing technology is used; in another example, aerosol non-contact digital printing technology is used; and in yet another example, valve-type non-contact digital printing technology is used. The specific method can be considered according to the actual situation and is not limited here.

[0057] In this embodiment, the thickness of the cured film 3002 is 5-15 μm. In other embodiments, other thicknesses may also be used, depending on the specific circumstances, and are not limited here.

[0058] Example 6 Furthermore, when the solar cell 3001 is pre-cured, a low-intensity ultraviolet light source is used to irradiate the solar cell 3001. The irradiation intensity is 50-300mW / cm², the irradiation time is 0.2-2 seconds, and the cumulative irradiation energy is 10-600mJ / cm². When the solar cell 3001 is undergoing primary curing, a high-intensity UV lamp is used to irradiate the solar cell 3001. The irradiation intensity is greater than 800mW / cm², and the cumulative irradiation energy is 800-3000mJ / cm².

[0059] Specifically, in the pre-curing stage, a low-intensity ultraviolet light source is used for irradiation. Due to its narrow spectrum, low heat, long lifespan and high energy efficiency, the ultraviolet light source is particularly suitable for the preliminary curing of heat-sensitive substrates. By controlling the irradiation energy within the above range, it can be ensured that the optical polymer on the surface of the solar cell 3001 quickly reaches a surface-dry state, that is, a high-viscosity gel-like film is formed, thereby pre-setting the curing film 3002, preventing it from flowing or deforming, and preparing it for subsequent main curing. At the same time, it avoids the internal stress of the curing film 3002 or damage to the solar cell 3001 that may be caused by excessive energy input.

[0060] Furthermore, in the main curing stage, a high-intensity UV lamp source is used to irradiate the pre-cured solar cell 3001. This high-intensity UV lamp source provides a wider spectrum or higher intensity ultraviolet light to achieve rapid and thorough curing of the optical polymer. The irradiation energy is set within the range of 800-5000 mJ / cm² to provide sufficient energy to promote the full cross-linking and polymerization of the photocurable oligomers and monomers in the optical polymer, forming a dense, uniform cured film 3002 with excellent mechanical and optical properties. This energy range ensures that the cured film 3002 meets its designed requirements for optical refractive index, hardness, adhesion, and weather resistance.

[0061] By employing the aforementioned phased and differentiated curing method—first using LED ultraviolet light source for pre-curing to achieve rapid shaping, and then using high-intensity UV lamps for main curing to ensure complete polymerization—the problem of balancing efficiency and quality that may exist with traditional single curing methods is effectively solved. Low-power pre-curing avoids potential damage to the solar cell 3001 due to initial overheating and provides a stable initial morphology for the cured film 3002, significantly improving production efficiency and yield. High-power main curing ensures that the optical polymer can form a cured film 3002 with stable optical properties and excellent physicochemical properties, thereby fully leveraging its anti-reflection and anti-reflection effects and ultimately improving the electrical performance of the solar cell 3001. Through the refined curing energy control in this embodiment, the application of the optical polymer on the solar cell 3001 is more reliable and efficient, ensuring the long-term stability and high-performance of the final photovoltaic module 10.

[0062] Furthermore, after the main curing of the solar cell 3001, the conversion rate of the C=C double bond can be monitored by infrared spectroscopy (FTIR) to ensure that the conversion rate after main curing is greater than 95%, so as to guarantee the long-term reliability of the cured film 3002.

[0063] Example 7 Furthermore, when the solar cell 3001 is pre-cured, the duration of ultraviolet light irradiation on the solar cell 3001 is controlled between 0.2 and 5 seconds.

[0064] Due to the use of photocurable oligomers with high photosensitivity and fast polymerization rates (such as one or more of polyurethane acrylate, epoxy acrylate, or polyester acrylate) and photocurable monomers (such as one or more of sulfur-containing acrylate monomers or OPPEA), and in conjunction with a highly efficient composite photoinitiator system (such as a combination of TPO and 1173), it is possible to ensure rapid initiation of polymerization reactions under extremely short ultraviolet light irradiation, so that the optical polymer can be rapidly transformed from a liquid or semi-liquid state into a gel or solid state with a certain shape and strength.

[0065] Therefore, when the solar cell 3001 is pre-cured, the irradiation time of the ultraviolet lamp is controlled within a short period of time, which can significantly shorten the process time of the pre-curing stage, improve the operating efficiency and capacity of the production line, reduce the consumption of unit products, and avoid the internal stress accumulation or surface over-curing of the cured film 3002 that may be caused by prolonged irradiation. This lays a solid foundation for the full curing of the subsequent main curing stage and the excellent optical properties (such as high refractive index and uniformity) of the final cured film 3002, and ultimately helps to improve the electrical performance of the solar cell 3001.

[0066] It is understood that in other embodiments, the irradiation time of the ultraviolet lamp may also be less than other values. For example, in one example, the irradiation time of the ultraviolet lamp is 0.5 seconds; in another example, the irradiation time of the ultraviolet lamp is 1 second; and in yet another example, the irradiation time of the ultraviolet lamp is 1.5 seconds. The specific duration can be designed according to the actual material selection and is not limited here.

[0067] It should be noted that, in order to prepare a thicker cured film 3002, for example, a cured film 3002 thickness of 35μm, two non-contact digital printing processes can be used. The first printing is for 18μm, followed by a 2-second pre-curing, and then a second printing is for 19μm, followed by another 2-second pre-curing, and then the main curing. This layered printing method can effectively prevent thick film flow and improve the uniformity of film thickness.

[0068] Example 8 Furthermore, before coating the optical polymer, the optical polymer described above is coated and printed onto the light-receiving surface of the solar cell 3001, with the coating and printing temperature of the optical polymer between 40 and 60 degrees Celsius and the viscosity of the optical polymer being 8-25 mPa·s.

[0069] The coating and printing temperature refers to the temperature at which the optical polymer is applied to the surface of the solar cell 3001. By setting the temperature range, the rheological properties of the optical polymer can be controlled and optimized, so that the optical polymer maintains a stable viscosity during the coating and printing process, thereby ensuring the uniformity and consistency of the cured film 3002.

[0070] By controlling the coating printing temperature between 40-60℃ and using specific nano-dispersants in the formulation, the surface tension and shear viscosity of the optical polymer can be effectively reduced, improving its wettability on the surface of the battery cell 3001 and helping to eliminate bubbles and reduce the generation of defects in the cured film 3002. Specific implementation methods may include heating the optical polymer storage container, controlling the temperature of the coating printing equipment (such as the printhead or doctor blade), or setting a constant temperature device in the coating printing environment.

[0071] The viscosity of an optical polymer is a physical quantity that measures its flow resistance. Controlling the viscosity of the optical polymer within the range of 8-25 mPa·s is crucial for achieving accurate and uniform coating and printing. Within this viscosity range, the optical polymer will not be difficult to spread or form a thick cured film 3002 due to excessive viscosity, nor will it flow excessively, form an excessively thin cured film 3002, or cause sagging due to excessive viscosity. Specifically, viscosity can be adjusted by changing the component ratio of the optical polymer, selecting oligomers and monomers of different molecular weights, adding highly efficient viscosity-reducing dispersants and low-viscosity monomers (such as OPPEA), or by precisely controlling the coating and printing temperature.

[0072] In this embodiment, when the optical polymer is coated and printed onto the light-receiving surface of the solar cell 3001, the coating and printing temperature of the optical polymer is precisely controlled between 40 and 60 degrees Celsius, and its viscosity is maintained within the optimized range of 8-20 mPa·s. Through precise control of the rheological parameters, the optical polymer is ensured to have ideal flowability and wettability during the coating and printing process, thereby effectively avoiding problems such as uneven thickness of the cured film 3002, surface defects (such as streaks, bubbles, or orange peel texture), and sagging. Finally, a highly uniform, flat, and defect-free optical cured film 3002 is formed on the surface of the solar cell 3001. This is crucial for maximizing light transmittance and reducing reflection loss, thereby significantly improving the photoelectric conversion efficiency and overall performance of the solar cell 3001.

[0073] Example 9 Please see Figure 1 and Figure 2 Furthermore, before coating the optical polymer of any of the above-mentioned components onto the light-receiving surface of the solar cell 3001, the process further includes: The light-receiving surface of the solar cell 3001 undergoes surface energy modification treatment to increase its surface energy. Specifically, the surface energy modification treatment includes at least one of plasma cleaning, corona treatment, or solvent cleaning. Specifically, since the antireflective coating (such as SiNX) on the surface of the photovoltaic cell 3001 typically has low surface energy, direct non-contact digital printing may result in poor ink wetting, pinholes, or insufficient adhesion. By bombarding the surface of the solar cell 3001 with atmospheric pressure plasma or corona treatment, organic contaminants on the surface can be removed and polar groups (such as -OH, -COOH) can be introduced, thereby significantly increasing the surface wetting tension (e.g., to above 40 dyne / cm), ensuring that optical polymer droplets can rapidly spread and form a continuous and uniform liquid film upon contact with the solar cell 3001.

[0074] Blow air onto the light-receiving surface of the solar cell 3001 to dry it.

[0075] In other words, before coating the optical polymer, the light-receiving surface of the battery cell 3001 is pretreated. The pretreatment step includes spraying a mixture of isopropanol and deionized water onto the light-receiving surface of the battery cell 3001 using high-pressure atomization. The high-pressure atomization technology can uniformly spray the mixture of isopropanol and deionized water onto the surface of the battery cell 3001 in the form of extremely fine droplets, thereby maximizing the contact area between the cleaning agent and surface contaminants and improving cleaning efficiency.

[0076] Specifically, isopropanol, as an excellent organic solvent, can effectively dissolve organic contaminants such as oil and fingerprints that may exist on the surface of the 3001 solar cell. Deionized water is used to clean the inorganic matter and isopropanol residues on the surface, ensuring that there are no ion residues on the surface and avoiding the introduction of new sources of contamination. The mixed use of isopropanol and deionized water can take into account the removal of both organic and inorganic contaminants and help to adjust the hydrophilicity or hydrophobicity of the surface of the 3001 solar cell, making its surface more suitable for the wetting and spreading of subsequent optical polymers. For example, the mixing ratio of isopropanol and deionized water can be adjusted according to the specific contamination of the surface of the 3001 solar cell to achieve the best cleaning effect.

[0077] Subsequently, the light-receiving surface of the battery cell 3001 after spray cleaning is dried by blowing air. The purpose of this step is to quickly and thoroughly remove the residual isopropanol and deionized water mixture on the surface of the battery cell 3001, and to avoid leaving watermarks, spots or residues during the natural drying process. Clean compressed air or nitrogen is usually used for blowing. By controlling the blowing pressure, flow rate and blowing time, it is ensured that the surface of the battery cell 3001 reaches a completely dry and residue-free state in a short time. Thorough drying is the key to ensuring the quality of the subsequent curing film 3002. It avoids defects in the curing film 3002 caused by solvent residue and provides an ideal clean and dry substrate for the uniform coating and printing of optical polymers.

[0078] Example 10 Please see Figure 1 and Figure 2 A solar cell 3001, wherein the light-receiving surface of the solar cell 3001 is covered with any of the aforementioned optical polymers.

[0079] A photovoltaic module 10 includes a first light-transmitting substrate 100, a first encapsulating film 200, a battery string 300, a second encapsulating film 500, and a backsheet or a second sealing film substrate 600 arranged sequentially along the light incident direction. The battery string 300 is composed of a plurality of the aforementioned battery cells 3001.

[0080] The light-receiving surface of the solar cell 3001 refers to the side in which the light is incident.

[0081] In this embodiment, the photovoltaic module 10 constructs a cured film 3002 formed of an optical polymer with a gradually changing refractive index on the light-receiving surface of the solar cell 3001. This not only solves the problem of interfacial optical loss but also simplifies the production process. With this setup, there is no need to modify the basic structure of the existing encapsulation film or antireflective film. It can be implemented simply by adding a coating and printing step in the preparation of the solar cell 3001, which significantly reduces the cost of technical transformation. At the same time, the optimized formulation of the optical polymer takes into account both material stability and process adaptability, ensuring uniform film formation under coating and printing temperatures of 40-60℃ and viscosity conditions of 8-25 mPa·s. This meets the requirements of high throughput and low cost for large-scale mass production. In other words, the photovoltaic module 10 in this embodiment effectively improves the light transmission efficiency without increasing the complexity of production, providing a practical solution for improving the efficiency of the photovoltaic module 10.

[0082] Specifically, the following examples illustrate the testing standards and effects of embodiments of the present invention.

[0083] Testing standards: Solar cell 3001: All solar cells used are commercially available N-type BC solar cells 3001 (light-receiving surface SiN). x Antireflection coating, n≈1.92600nm).

[0084] Component fabrication: The processed 3001 solar cells are encapsulated into a single laminate (glass / EVA / 3001 solar cell / backsheet), with EVA film (n≈1.48).

[0085] Electrical performance testing: The output light intensity of the component was tested using an AAA-grade solar simulator under standard test conditions (STC).

[0086] The comparisons of Examples 1-3 and Comparative Examples 1-3 demonstrate that simply using resin (Comparative Example 3) cannot achieve high refractive index matching, while introducing a high loading of nano-zirconia (Example 1) can significantly improve the refractive index. In particular, Examples 2 and 3, by introducing a special low-viscosity, high-refractive-index monomer (OPPEA) and a highly efficient nano-dispersant, successfully achieved a low viscosity (22 cP) suitable for inkjet printing even with an extremely high nanoparticle loading (60 parts), and broke through the refractive index to 1.71, thus obtaining the highest power gain (+0.82%). This verifies the key role of dispersants and special monomers in resolving the contradiction between "high refractive index and low viscosity". Example 4 demonstrates that surface energy modification treatment (such as plasma treatment) helps to further improve the wettability and film uniformity of the optical polymer, with a slight increase in power gain compared to the untreated group (Example 1) (+0.45% vs +0.42%), verifying the positive effect of the pretreatment steps in the claims. Example 5 demonstrates that extremely high light intensity combined with low total energy (mJ) enables rapid curing, meeting the cycle time requirements of high-speed inkjet production lines, while maintaining excellent optical properties.

[0087] Example 5 demonstrates that even at lower curing energies, the initiator system of this invention can achieve full curing and bring about considerable performance improvements, showcasing its broad process window.

[0088] A photovoltaic system includes the photovoltaic module 10 described above.

[0089] The beneficial effects achieved by this invention are as follows: due to the use of low-viscosity, high-refractive-index monomers and specific nano-dispersion technology in the optical polymer, the high-load nanoparticle system maintains the low viscosity characteristics required for inkjet printing. The cured film 3002 formed after curing has a refractive index of 1.60-1.75 under 600nm wavelength irradiation. Furthermore, combined with non-contact digital printing technology, it achieves precise coating printing at the micron level. This effectively matches the refractive index difference between the encapsulation film and the battery antireflective film, reducing interface reflection loss. It has the advantage of providing a cured film 3002 with a specific refractive index, optimizing light transmission, reducing reflection loss at the interface between the encapsulation film and the battery antireflective film, thereby improving the efficiency of the photovoltaic module 10.

[0090] It is understood that those skilled in the art can combine various implementation methods in the above embodiments under the guidance of the above examples to obtain technical solutions with multiple implementation methods.

[0091] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An optical polymer suitable for contactless digital printing of photovoltaic cells, characterized in that, The optical polymer comprises, by weight: 20-50 parts of photocurable oligomer, 30-60 parts of photocurable monomer, 20-70 parts of high refractive index nanoparticles, 0.5-10 parts of nano-dispersant, 1-10 parts of photoinitiator system, and 0.1-5 parts of additives. The optical polymer has a viscosity of 8-25 mPa·s at a temperature of 40-60 degrees Celsius, and the cured film formed after curing has a refractive index of 1.60-1.75 at a wavelength of 600 nm.

2. The optical polymer as claimed in claim 1, characterized in that, The photocurable oligomer comprises polyurethane acrylate, epoxy acrylate, or polyester acrylate, or a combination thereof, and the ratio of the photocurable monomers is configured to adjust the viscosity of the optical polymer to meet the requirements of non-contact digital printing; the photocurable monomers are selected from at least one of sulfur-containing acrylate monomers, o-phenylphenoxyethyl acrylate (OPPEA), 2-phenylphenol acrylate, or bisphenol A epoxy acrylate, to provide a high refractive index at low viscosity at at least one of sulfur-containing acrylate monomers, o-phenylphenoxyethyl acrylate (OPPEA), 2-phenylphenol acrylate, or bisphenol A epoxy acrylate; The high-refractive-index nanoparticles include one or more of the following: nano-zirconia, nano-hafnium oxide, nano-titanium dioxide, nano-zinc sulfide, or nano-zinc sulfide, which have been modified with a surface silane coupling agent or the nano-dispersant, and have a particle size of 10-50 nm; the nano-dispersant includes a copolymer dispersant containing acidic groups, wherein the acidic groups are selected from phosphate ester groups, carboxyl groups, or sulfonic acid groups; The photoinitiator system is a combination of acylphosphine oxide photoinitiators and α-hydroxyketone photoinitiators; The additives include silane coupling agents, leveling agents, and defoamers.

3. A method for applying an optical polymer, characterized in that, The application method includes: The optical polymer described in any one of claims 1-2 is coated and printed onto the light-receiving surface of the battery cell using non-contact digital printing technology; The solar cell coated with the printed optical polymer is pre-cured to allow the optical polymer to be in a semi-cured state for pinning and shaping; The pre-cured battery cell is then subjected to primary curing to fully crosslink the optical polymer.

4. The method of applying the optical polymer as described in claim 3, characterized in that, The optical polymer is applied to the light-receiving surface of the solar cell using one or more non-contact digital printing processes, forming a cured film with a thickness of 3-20 μm on the solar cell.

5. The method of applying the optical polymer as described in claim 3, characterized in that, When the battery cell is pre-cured, a low-intensity ultraviolet light source is used to irradiate the battery cell. The irradiation intensity is 50-300mW / cm², the irradiation time is 0.2-2 seconds, and the cumulative irradiation energy is 10-600mJ / cm². During the primary curing of the solar cells, the solar cells are irradiated with a high-intensity UV lamp with an irradiation intensity greater than 800mW / cm² and a cumulative irradiation energy of 800-3000mJ / cm².

6. The method of applying the optical polymer as described in claim 3, characterized in that, Before coating the optical polymer, the optical polymer is heated to 40-60 degrees Celsius to keep its viscosity in the range of 8-25 mPa·s.

7. The method of applying the optical polymer as described in claim 3, characterized in that, Before coating and printing the optical polymer according to any one of claims 1-2 onto the light-receiving surface of the solar cell, the method further includes: The light-receiving surface of the solar cell is subjected to surface energy modification treatment, which includes at least one of plasma treatment, corona treatment, flame treatment, or solvent cleaning, so that the surface energy of the solar cell surface is sufficient to meet the wetting requirements.

8. A battery cell, characterized in that, The light-receiving surface of the battery cell is covered with a cured film formed by curing the optical polymer as described in any one of claims 1-2.

9. A photovoltaic module, characterized in that, It includes a first light-transmitting substrate, a first adhesive film, a battery string, a second adhesive film, and a second sealing substrate arranged sequentially along the light incident direction, wherein the battery string is composed of a plurality of battery cells as described in claim 8.

10. A photovoltaic system, characterized in that, Includes the photovoltaic module described in claim 9 above.

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