Light-conversion polyvinyl acetal film, preparation method and photovoltaic module thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly discloses a light-conversion polyvinyl acetal film which comprises a double-layer structure and sequentially comprises a first-layer film and a second-layer film, and the first-layer film and the second-layer film are obtained by plasticizing and co-extruding a first-layer film mixture and a second-layer film mixture respectively. The invention provides a light-conversion polyvinyl acetal film which comprises a double-layer structure and sequentially comprises a first-layer film and a second-layer film, and the first-layer film and the second-layer film are respectively obtained by plasticizing and co-extruding a first-layer film mixture and a second-layer film mixture, the first-layer film mixture and the second-layer film mixture respectively contain a low-content light conversion agent A and a low-content light conversion agent B, and the first-layer film and the second-layer film have different functions due to different types of the light conversion agent A and the light conversion agent B; finally, the light-conversion polyvinyl acetal film with the advantages of low ultraviolet leakage, high ultraviolet conversion, low cost and the like is obtained.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a light-converting polyvinyl alcohol acetal film, its preparation method, and its photovoltaic module. Background Technology

[0002] With increasing environmental awareness, photovoltaic (PV) new energy, which is more economical, environmentally friendly, and sustainable, is booming. PV modules mainly consist of glass substrates, photovoltaic films, and battery chips. Among them, heterojunction (HJT) cells are seeing a continuously increasing share of PV cells due to their mature technology and lower equipment costs.

[0003] However, the surface of HJT cells contains an amorphous silicon layer (a-Si) with a large number of Si-H bonds, which is susceptible to damage from ultraviolet (UV) radiation, resulting in internal structural defects and ultimately causing power degradation of the module. While UV-blocking films can protect heterojunction cells by shielding them from UV radiation, they cannot effectively utilize the high-energy UV radiation, leading to significant waste of UV energy.

[0004] Light-conversion film is a novel technology specifically developed for high-transparency photocells (HJTs). By adding wavelength conversion materials (light-converting agents) to a high-transparency encapsulating film, it converts high-frequency ultraviolet light (280-380nm) into usable visible light, thereby increasing the power generation of the module. Therefore, light-conversion film possesses the performance of UV-blocking films while also offering power output capabilities comparable to high-transparency films.

[0005] Traditional light-conversion films are mainly made of EVA, POE, and EPE. However, with the continuous development of building-integrated photovoltaics (BIPV), the adhesion, water vapor resistance, and impact resistance of EVA, POE, and EPE films are no longer sufficient to meet the requirements. Furthermore, relevant policies explicitly require that the protective film used in BIPV must be polyvinyl butyral (PVB) film. Therefore, how to enable PVB film to also possess light-conversion functionality while maintaining conventional adhesion, water vapor resistance, and impact resistance has become a key challenge in the development of this product.

[0006] Chinese invention patent CN114058271A discloses a film with different UV absorption bands, which contains 0.05% added per 100 parts of base resin. 2 parts UV absorber and 0.05 Two parts of UV light conversion agent, this type of film has a UV band (280) The transmittance at 380nm was 7.02. 13.55%, a considerable portion of UV radiation still passes through the encapsulant film to reach the solar cell. This unabsorbed or unconverted UV radiation will cause UV degradation in HJT cells, thus accelerating module power decay. Chinese invention patent CN118027854A discloses a light-converting PVB encapsulant film for photovoltaic encapsulation, its preparation method, and its application. While it achieves an increase in photovoltaic module power, it adds 1% more UV radiation per 100 parts of base resin. Ten parts of light-converting agent. While the addition of a large amount of light-converting agent improves the power output of photovoltaic modules to some extent, the significant increase in cost makes it difficult to widely use light-converting PVB films in photovoltaic modules. Chinese invention patent CN118460123A discloses a UV-transmitting PVB composite film, its preparation method, and its application. By spraying an ultra-thin UV conversion layer between an EVA film and a PVB film, ultraviolet light is efficiently converted into photovoltaic-usable light; and by adding a UV absorber to the PVB film, unconverted ultraviolet light is absorbed, preventing damage to the solar cells. While this patent prevents UV damage to the solar cells through the combination of a UV conversion layer and a cutoff layer, it is difficult to achieve a high degree of UV conversion.

[0007] Currently, the cost of light conversion agents with low UV leakage and high UV conversion is generally high. To achieve low-cost light conversion films, the amount of light conversion agent used must be reduced. However, as the amount of light conversion agent used decreases, some UV leakage is likely to occur, ultimately affecting the stability of photovoltaic modules. How to develop light conversion films with low UV leakage and high UV conversion at low cost has always been a challenge for industrialization.

[0008] In summary, existing light conversion films are prone to ultraviolet leakage when the amount of light conversion agent used is low, which ultimately affects the stability of photovoltaic modules. Summary of the Invention

[0009] This invention provides a light-converting polyvinyl acetal film, which can solve the problem in the prior art where light-converting films are prone to ultraviolet leakage when the amount of light-converting agent used is low, ultimately affecting the stability of photovoltaic modules.

[0010] In a first aspect, the present invention provides a light-converting polyvinyl acetal film, comprising a double-layer structure, comprising a first film and a second film in sequence, wherein the first film and the second film are obtained by plasticizing and co-extruding the first film mixture and the second film mixture, respectively; The first layer film mixture comprises the following raw materials in parts by weight: 70-80 parts of polyvinyl acetal resin, 20-30 parts of plasticizer, 0.1-0.8 parts of antioxidant, and 0.01-0.1 parts of light conversion agent A; The second layer film mixture comprises the following raw materials in parts by weight: 70-80 parts of polyvinyl acetal resin, 20-30 parts of plasticizer, 0.1-0.8 parts of antioxidant, 0.1-0.2 parts of light conversion agent B, and 0.1-0.5 parts of light conversion agent cosolvent B.

[0011] Furthermore, the thickness ratio of the first thin film to the second thin film is 1:3 to 3:1.

[0012] Furthermore, the thickness of the light-converting polyvinyl acetal film is 0.18–1.52 mm; The transmittance of the light-converting polyvinyl acetal film for ultraviolet light with a wavelength less than 380 nm is no greater than 0.01%. The visible light transmittance of the light-converting polyvinyl alcohol acetal film is ≥90%.

[0013] Furthermore, the fluorescence quantum efficiency of the first thin film is ≥90%, and the transmittance of the first thin film for ultraviolet light with a wavelength less than 380nm is not greater than 20%. The fluorescence quantum efficiency of the second thin film is ≥40%, and the transmittance of the second thin film for ultraviolet light with a wavelength less than 380nm is not greater than 0.1%.

[0014] The light-converting polyvinyl acetal film provided by the present invention comprises a double-layer structure, consisting of a first film and a second film, wherein the first film and the second film are obtained by plasticizing and co-extruding the first film mixture and the second film mixture, respectively. The fluorescence quantum efficiency of the first film is ≥90%, and the fluorescence quantum efficiency of the second film is ≥40%, which makes the functions of the first film and the second film different, that is, the light-converting polyvinyl acetal film with advantages such as low ultraviolet leakage, high ultraviolet conversion and low cost is finally obtained.

[0015] Furthermore, the light-converting agent A is a light-converting agent containing a long-chain alkyl group in its molecule.

[0016] Furthermore, the light-converting agent A is any one or more of rare earth organic light-converting agents and organic fluorescent pigments, mixed in any proportion; The light conversion agent B is any one or more of rare earth inorganic light conversion agents and perovskite quantum dots, mixed in any proportion. The light-converting agent co-solvent B is any one or more of silane coupling agents and ester organic compounds, mixed in any proportion.

[0017] Furthermore, the silane coupling agent is any one or more of vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, and 3-mercaptopropyltrimethoxysilane, mixed in any proportion; The ester organic compound is any one or more of pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetraacrylate ethoxylate, pentaerythritol tetraacrylate propoxylate, and trihydroxypropane triacrylate, mixed in any proportion.

[0018] Further, the hydroxyl value of the polyvinyl acetal resin in the first and second film mixtures is 16.5% to 21.0%, and / or the acetoxyl content of the polyvinyl acetal resin in the first and second film mixtures is 0.5% to 2.0%.

[0019] Secondly, the present invention provides a method for preparing a light-converting polyvinyl acetal film, the method comprising the following steps: S1. According to the formula of the first layer film mixture, weigh out polyvinyl acetal resin, plasticizer, antioxidant and light conversion agent A, add light conversion agent A and antioxidant to plasticizer, heat to dissolve completely, and prepare plasticized mixture A. S2. According to the formula of the second layer film mixture, weigh out polyvinyl acetal resin, plasticizer, antioxidant, light conversion agent B, and light conversion agent cosolvent B. Heat and mix light conversion agent B and light conversion agent cosolvent B to prepare light conversion dispersion B. Dissolve light conversion dispersion B and antioxidant in plasticizer to prepare plasticized mixture B. S3. Plasticize the plasticized mixture A and the polyvinyl acetal resin provided in step S1 through a first extruder, and plasticize the plasticized mixture B and the polyvinyl acetal resin provided in step S2 through a second extruder, and then form them through a multi-layer co-extrusion die to obtain a bright polyvinyl acetal film.

[0020] Furthermore, in step S3, the plasticizing temperature is 110–220°C, and the die head temperature is 130–200°C.

[0021] Thirdly, the present invention also provides a photovoltaic module, comprising a glass substrate, a first photovoltaic film, a battery chip, a second photovoltaic film, and a glass substrate stacked sequentially, wherein the first photovoltaic film is the light-converting polyvinyl acetal film provided in the embodiment of the first aspect of the present invention.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a light-converting polyvinyl alcohol acetal film, which includes a double-layer structure, comprising a first film and a second film in sequence. The first film and the second film are obtained by plasticizing and co-extruding the first film mixture and the second film mixture, respectively. The first film mixture and the second film mixture contain low contents of light-converting agent A and light-converting agent B, respectively. Due to the different types of light-converting agent A and light-converting agent B, the first film and the second film have different functions, ultimately obtaining a light-converting polyvinyl alcohol acetal film with advantages such as low UV leakage, high UV conversion, and low cost.

[0023] 2. In this invention, a light-converting agent co-solvent B is introduced into the second layer film mixture. Since conventional light-converting agents are powder particles of varying sizes, and polyvinyl acetal resin is also a non-uniform powder particle, their compatibility is poor. Simply blending the light-converting agent with polyvinyl acetal resin will make it difficult to ensure the uniformity of the mixture, thus affecting the function of the light-converting agent and ultimately impacting the product performance of the light-converting film. By selecting a suitable light-converting agent co-solvent, the light-converting agent can be effectively dissolved and dispersed, obtaining a uniform light-converting dispersion, thereby improving the interfacial properties of the light-converting agent in the matrix resin. Adding the light-converting dispersion to the plasticizer further achieves effective dispersion, promoting its light-converting effect. Finally, through high-speed shearing and mixing in an extruder, the polyvinyl acetal resin and the plasticizer containing the light-converting agent can be uniformly mixed to obtain a high-performance light-converting film.

[0024] 3. In this invention, a double-layer film combination technology is adopted to precisely control the formulation and performance parameters of each film layer, ensuring the quality of the prepared light-converting polyvinyl acetal film. At the same time, since the amount of light-converting agent added in each film layer is low (for example, in the first film mixture, the amount of light-converting agent A added is only 0.01 to 0.1 parts; in the second film mixture, the amount of light-converting agent B added is only 0.1 to 0.2 parts), a significant reduction in production costs is achieved, bringing unprecedented economic benefits and enhanced competitiveness to the photovoltaic industry. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of the light-converting polyvinyl acetal film provided by the present invention; Figure 2 This is a schematic diagram of the structure of the photovoltaic module provided by the present invention.

[0026] Explanation of reference numerals in the attached figures: 1. First thin film; 2. Second thin film; 3. First glass substrate; 4. First photovoltaic film; 5. Battery chip; 6. Second photovoltaic film; 7. Second glass substrate. Detailed Implementation

[0027] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0028] Firstly, such as Figure 1 As shown, the present invention provides a light-converting polyvinyl acetal film, which includes a double-layer structure, comprising a first film 1 and a second film 2 in sequence. The first film 1 and the second film 2 are obtained by plasticizing and co-extruding the first film mixture and the second film mixture, respectively. The thickness of the light-converting polyvinyl acetal film is 0.18–1.52 mm. The thickness ratio of the first thin film 1 to the second thin film 2 is 1:3 to 3:1. The first layer film mixture comprises the following raw materials in parts by weight: 70-80 parts polyvinyl acetal resin, 20-30 parts plasticizer, 0.1-0.8 parts antioxidant, and 0.01-0.1 parts light conversion agent A; The second layer film mixture includes the following raw materials in parts by weight: 70-80 parts of polyvinyl acetal resin, 20-30 parts of plasticizer, 0.1-0.8 parts of antioxidant, 0.1-0.2 parts of light conversion agent B, and 0.1-0.5 parts of light conversion agent cosolvent B.

[0029] Specifically, the transmittance of the light-converting polyvinyl alcohol acetal film for ultraviolet light with a wavelength less than 380nm is no greater than 0.01%, that is, the ultraviolet light transmittance (<380nm) of the light-converting polyvinyl alcohol acetal film is ≤0.01%; the visible light transmittance of the light-converting polyvinyl alcohol acetal film is ≥90%. The transmittance of the first thin film for ultraviolet light with wavelengths less than 380 nm is no greater than 20%, that is, the ultraviolet light transmittance (<380 nm) of the first thin film is ≤20%; the fluorescence quantum efficiency of the first thin film is ≥90%. The transmittance of the second thin film for ultraviolet light with wavelengths less than 380 nm is no greater than 0.1%, that is, the ultraviolet light transmittance (<380 nm) of the second thin film is ≤0.1%; the fluorescence quantum efficiency of the second thin film is ≥40%. In addition, the excitation wavelength of the first thin film is 350±30nm and the emission wavelength is 430±20nm; The excitation wavelength of the second thin film is 350±30nm, and the emission wavelength is 430±20nm. In this light-converting polyvinyl acetal film, a film with high ultraviolet light conversion capability (i.e., the first thin film) is used as the outer layer structure to first achieve the conversion and utilization of most ultraviolet light; then a film with low ultraviolet leakage and low ultraviolet light conversion capability (i.e., the second thin film) is used as the inner layer structure to achieve the reconversion and utilization of the trace amount of ultraviolet light leaked from the first thin film, thereby ensuring almost zero ultraviolet light leakage. By combining outer and inner structures with different functions, a light-converting polyvinyl alcohol acetal film with advantages such as low UV leakage, high UV conversion, and low cost is obtained. The final photovoltaic film product has a UV transmittance (380nm) ≤0.01% and a visible light transmittance ≥90%. The prepared light-converting polyvinyl alcohol acetal film is tested and found to have a tensile strength ≥25MPa and an elongation at break ≥210%. When applied to photovoltaic modules, the power of the photovoltaic modules can be increased by 1.5% or more. This light-converting polyvinyl acetal film has precise ultraviolet absorption performance and will not absorb visible light above 380nm, which can be effectively absorbed and converted by batteries; at the same time, it can accurately convert the absorbed ultraviolet light into blue light, which is easily absorbed and converted by heterojunction batteries. Furthermore, in the first layer of film mixture, the light-converting agent A is a light-converting agent containing long-chain alkyl groups in its molecule; specifically, the light-converting agent A is any one or more of rare earth organic light-converting agents and organic fluorescent pigments mixed in any proportion; The rare earth organic light-converting agent is a rare earth organic light-converting agent containing long-chain alkyl groups in its molecule. The number of long-chain alkyl groups in the rare earth organic light-converting agent is at least one. The long-chain alkyl group in the rare earth organic light-converting agent is preferably a C9-25 long-chain alkyl group. The organic fluorescent pigment is an organic fluorescent pigment containing long-chain alkyl groups in its molecule, wherein the number of long-chain alkyl groups is at least one; in the rare earth organic light-converting agent, the long-chain alkyl group is preferably a C9-25 long-chain alkyl group; More specifically, the chemical structure of the light-converting agent A includes, but is not limited to, (as shown in structures 1-4):

[0030] Among them, R1~R 10 Each can be independently a hydrogen atom or a C9 atom. C25 long-chain alkyl group, and R1~R 10 At least one of the groups is C9. C25 straight-chain or branched alkyl

[0031] Because the light-converting agent A contains a certain proportion of long-chain alkyl groups and is liquid at room temperature, it has good solubility and dispersibility in plasticizers and does not require the addition of any dispersants (i.e., light-converting agent co-solvents); and the light-converting agent A has high fluorescence quantum efficiency (fluorescence quantum efficiency ≥90%), but there is a certain amount of ultraviolet leakage. Conversion agent B is a low fluorescence quantum efficiency (fluorescence quantum efficiency ≥ 40%), high ultraviolet absorption conversion agent. Specifically, conversion agent B is L... Si :Ce BaM A Eu 、(Sr,Ca Si Eu (Sr, Ba)Li2[Be4O6]:Eu 2+ (Zn, Mg) E Cl、CsPbC C AgInC C NaInC Mix any one or more of rare earth inorganic light-converting agents or perovskite quantum dots in any proportion; The fluorescence quantum efficiency of transducer A is greater than that of transducer B. More specifically, the light-converting agent co-solvent B is any one or more of silane coupling agents and ester organic compounds mixed in any proportion; The silane coupling agent is any one or more of vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, and 3-mercaptopropyltrimethoxysilane, mixed in any proportion; The ester organic compounds are any one or more of pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetraacrylate ethoxylate, pentaerythritol tetraacrylate propoxylate, and trihydroxypropane triacrylate, mixed in any proportion; In both the first and second film mixtures, the plasticizers are independently selected from any one or more of the following: triethylene glycol diisooctanoate, dioctyl phthalate, dioctyl sebate, tetraethylene glycol di-n-heptyl phthalate, dimethyl phthalate, dioctyl adipate, and dibutyl sebacate, mixed in any proportion.

[0032] In addition, the hydroxyl value of the polyvinyl acetal resin in the first and second film mixtures is 16.5% to 21.0%. The acetoxy group content of polyvinyl acetal resin in the first and second film mixtures is 0.5% to 2.0%.

[0033] Secondly, the present invention provides a method for preparing a light-converting polyvinyl acetal film, the method comprising the following steps: S1. According to the formula of the first layer film mixture, weigh out polyvinyl acetal resin, plasticizer, antioxidant and light conversion agent A, add light conversion agent A and antioxidant to plasticizer, heat to dissolve completely, and prepare plasticized mixture A. S2. According to the formula of the second layer film mixture, weigh out polyvinyl acetal resin, plasticizer, antioxidant, light conversion agent B, and light conversion agent cosolvent B. Heat and mix light conversion agent B and light conversion agent cosolvent B to prepare light conversion dispersion B. Dissolve light conversion dispersion B and antioxidant in plasticizer to prepare plasticized mixture B. S3. Plasticize the plasticized mixture A and the polyvinyl acetal resin provided in step S1 through a first extruder, and plasticize the plasticized mixture B and the polyvinyl acetal resin provided in step S2 through a second extruder, and then form them through a multi-layer co-extrusion die to obtain a bright polyvinyl acetal film.

[0034] In step S3, the plasticizing temperature is 110–220°C and the die head temperature is 130–200°C.

[0035] Thirdly, the present invention provides a photovoltaic module, comprising a first glass substrate 3, a first photovoltaic film 4, a battery chip 5, a second photovoltaic film 6, and a second glass substrate 7 stacked sequentially, wherein the first photovoltaic film 4 is a light-converting polyvinyl acetal film provided in the embodiment of the first aspect of the present invention. Specifically, such as Figure 2 As shown, the first photovoltaic film 4 adopts a light-converting polyvinyl acetal film provided by the first aspect of the present invention, which includes a double-layer structure, comprising a first thin film and a second thin film in sequence. The first thin film of the first photovoltaic film 4 is in close contact with the first glass substrate 3, and the second thin film is in close contact with the battery chip 5. The second photovoltaic film 6 adopts a light-converting polyvinyl acetal film provided in the first aspect of the present invention, which includes a double-layer structure, comprising a first thin film and a second thin film in sequence. The first thin film of the second photovoltaic film 6 is in close contact with the second glass substrate 7, and the second thin film is in close contact with the battery chip 5.

[0036] Example 1

[0037] This embodiment provides a method for preparing a light-converting polyvinyl acetal film, including the following steps: S1. According to the raw material formula of the first layer film mixture, weigh out 75 parts of polyvinyl acetal resin, 25 parts of plasticizer, 0.4 parts of antioxidant, and 0.05 parts of light conversion agent A. Add light conversion agent A (mainly composed of structure 1, where R1 is a C18 straight-chain alkyl substituted compound, R2-R...) 10 (Independent hydrogen) was added to the plasticizer triethylene glycol diisooctanoate (3G8), and stirred for 20 minutes to obtain plasticized mixture A. The above plasticized mixture A and polyvinyl acetal resin were simultaneously added to an extruder with a plasticizing temperature of 180°C for plasticizing; S2. According to the raw material formula of the second layer film mixture, weigh out 75 parts of polyvinyl acetal resin, 25 parts of plasticizer, 0.4 parts of antioxidant, and light conversion agent B (L). Si :Ce 0.1 parts of lanthanum oxide and cerium oxide co-solvent B were added to the plasticizer triethylene glycol triacrylate (3G8) and stirred for 20 minutes at 50°C to obtain a light-converting dispersion. The dispersion was then added to the plasticizer triethylene glycol diisooctanoate (3G8) and stirred for 20 minutes to obtain plasticized mixture B. Plasticized mixture B and polyvinyl acetal resin were simultaneously added to an extruder at a plasticizing temperature of 180°C for plasticizing. S3. The plasticized melt from step S1 and the plasticized melt from step S2 are passed through the flow channel of the distributor to form a two-layer structure. The melt is extruded through the die at a temperature of 180°C. The thickness ratio of the first film and the second film is controlled to be 1:1, and the overall film thickness is 0.76 mm, thus obtaining the light-converting polyvinyl acetal film.

[0038] Example 2

[0039] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that the amount of light-converting agent A added to the first layer film mixture is different in this embodiment. Specifically: The amount of light-converting agent A added to the first layer of film mixture was changed from 0.05 parts to 0.1 parts; the remaining raw materials, parameters and preparation process were the same as in Example 1.

[0040] Example 3

[0041] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that the amount of light-converting agent B added to the second layer film mixture is different in this embodiment. Specifically: The amount of light-converting agent B added to the second layer film mixture was changed from 0.1 parts to 0.2 parts; the remaining raw materials, parameters and preparation process were the same as in Example 1.

[0042] Example 4

[0043] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Embodiment 1 is that in this embodiment, the amount of light-converting agent co-solvent B added in the second layer film mixture is 0.1 parts; the remaining raw materials, parameters and preparation process are the same as in Embodiment 1.

[0044] Example 5

[0045] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that in this embodiment, the amount of light-converting agent A added in the first layer film mixture is 0.01 parts; the amount of light-converting agent B added in the second layer film mixture is 0.15 parts, and the amount of light-converting agent co-solvent B added is 0.5 parts; the remaining raw materials, parameters and preparation process are the same as in Embodiment 1.

[0046] Example 6

[0047] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that the thickness ratio of the first film layer and the second film layer is changed from 1:1 to 3:1 in this embodiment; the other raw materials, parameters and preparation process are the same as in Embodiment 1.

[0048] Example 7

[0049] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Embodiment 1 is that the thickness ratio of the first film layer and the second film layer is changed from 1:1 to 1:3 in this embodiment; the other raw materials, parameters and preparation process are the same as in Embodiment 1.

[0050] Example 8

[0051] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that in this embodiment, the thickness ratio of the first film layer and the second film layer is changed from 1:1 to 2:1; the remaining raw materials, parameters and preparation process are the same as in Embodiment 1.

[0052] Example 9

[0053] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that the overall film thickness is changed from 0.76 mm to 1.12 mm, while the other raw materials, parameters and preparation process are the same as in Embodiment 1.

[0054] Example 10

[0055] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that the overall film thickness is changed from 0.76 mm to 0.18 mm in this embodiment; the other raw materials, parameters and preparation process are the same as in Embodiment 1.

[0056] Example 11

[0057] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Embodiment 1 is that the overall film thickness is changed from 0.76 mm to 1.52 mm in this embodiment; the other raw materials, parameters and preparation process are the same as in Embodiment 1.

[0058] Example 12

[0059] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Embodiment 1 is that, in this embodiment, the amount of plasticizer added in the first layer film mixture is changed from 25 parts to 30 parts, the amount of polyvinyl alcohol resin added is changed from 75 parts to 70 parts, and the amount of antioxidant added is 0.1 parts; in the second layer film mixture, the amount of plasticizer added is changed from 25 parts to 20 parts, the amount of polyvinyl alcohol resin added is changed from 75 parts to 80 parts, and the amount of antioxidant added is 0.8 parts; the remaining raw materials, parameters, and preparation process are the same as in Embodiment 1.

[0060] Example 13

[0061] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Embodiment 1 is that, in this embodiment, the amount of plasticizer added in the first layer film mixture is changed from 25 parts to 20 parts, the amount of polyvinyl alcohol resin added is changed from 75 parts to 80 parts, and the amount of antioxidant added is 0.8 parts; in the second layer film mixture, the amount of plasticizer added is changed from 25 parts to 30 parts, the amount of polyvinyl alcohol resin added is changed from 75 parts to 70 parts, and the amount of antioxidant added is 0.1 parts; the remaining raw materials, parameters, and preparation process are the same as in Embodiment 1.

[0062] Example 14

[0063] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Embodiment 1 is that in this embodiment, the light-converting agent A adopts structure 2 (where R1, R3-R7 are hydrogen, and R2 is a C18 straight-chain alkyl substituted); the other raw materials, parameters and preparation process are the same as in Embodiment 1.

[0064] Example 15

[0065] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Example 1 is that in this embodiment, the light-converting agent A adopts structure 3 (where R2-R8 are hydrogen and R1 is a C18 straight-chain alkyl substituted); the other raw materials, parameters and preparation process are the same as in Example 1.

[0066] Example 16

[0067] This embodiment provides a method for preparing a light-converting polyvinyl alcohol acetal film. The difference from Embodiment 1 is that in this embodiment, the light-converting agent A adopts structure 4 (where R1, R3-R7 are hydrogen, and R2 is a C18 straight-chain alkyl substituted); the other raw materials, parameters and preparation process are the same as in Embodiment 1.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. The difference from Example 1 is that no light-converting agent was added to the first and second film layers; the remaining raw materials, parameters, and preparation process are the same as in Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. The difference from Example 1 is that no light-converting agent B is added to the second film layer; the other raw materials, parameters and preparation process are the same as in Example 1.

[0072] Comparative Example 3

[0073] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. The difference from Example 1 is that no light-converting agent A is added to the first film layer; the other raw materials, parameters and preparation process are the same as in Example 1.

[0074] Comparative Example 4

[0075] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. Compared with Example 1, the difference is that 0.05 parts of light-converting agent A added to the first film layer are replaced with 0.05 parts of ultraviolet absorber 326, and 0.1 parts of light-converting agent B added to the second film layer are replaced with 0.1 parts of ultraviolet absorber 326; the remaining raw materials, parameters and preparation process are the same as in Example 1.

[0076] Comparative Example 5

[0077] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. Compared with Example 1, the difference is that 0.05 parts of light-converting agent A are still added to the first film layer, and 0.1 parts of light-converting agent B added to the second film layer are replaced with 0.1 parts of ultraviolet absorber 326; the remaining raw materials, parameters and preparation process are the same as in Example 1.

[0078] Comparative Example 6

[0079] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. Compared with Example 1, the difference is that 0.05 parts of light-converting agent A in the first film layer is replaced with 0.05 parts of ultraviolet absorber 326, and 0.1 parts of light-converting agent B is still added to the second film layer; the remaining raw materials, parameters and preparation process are the same as in Example 1.

[0080] Comparative Example 7

[0081] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. Compared with Example 1, the difference is that 0.05 parts of light-converting agent A are still added to the first film layer, and 0.1 parts of light-converting agent B in the second film layer are replaced with 0.1 parts of light-converting agent A. That is, the same type of light-converting agent is added to the first and second films. The remaining raw materials, parameters and preparation process are the same as in Example 1.

[0082] Comparative Example 8

[0083] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. Compared with Example 1, the difference is that, firstly, 0.05 parts of light-converting agent A and 0.1 parts of light-converting agent B are thoroughly mixed to obtain a mixed light-converting agent. The mixed light-converting agent is then divided into two parts, namely mixed light-converting agent A and mixed light-converting agent B, wherein the mass ratio of mixed light-converting agent A to mixed light-converting agent B is 1:1. Then, mixed light-converting agent A and mixed light-converting agent B are added to the first layer and the second layer film, respectively. The remaining raw materials, parameters, and preparation process are the same as in Example 1.

[0084] Comparative Example 9

[0085] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. The difference from Example 1 is that the 0.05 parts of light-converting agent A added to the first film layer are not added to the plasticizer first, but are directly blended with the polyvinyl acetal resin first, and then plasticized together with the plasticizer in the extruder to form a film; the other raw materials, parameters and preparation process are the same as in Example 1.

[0086] Comparative Example 10

[0087] This comparative example provides a method for preparing a light-converting polyvinyl acetal film. Compared with Example 1, the difference is that the 0.1 part of light-converting agent B added to the second film layer is not first added to the light-converting agent co-solvent pentylenetetroxide triacrylate. Instead, the light-converting agent B and the light-converting agent co-solvent pentylenetetroxide triacrylate are directly blended with the polyvinyl acetal resin first, and then plasticized together with the plasticizer in an extruder to form a film. The other raw materials, parameters and preparation process are the same as in Example 1.

[0088] Comparative Example 11

[0089] This embodiment provides a method for preparing a light-converting polyvinyl acetal film. The difference from Embodiment 1 is that in this embodiment, the light-converting agent A adopts structure 1 (wherein, R1 – R...). 10 All materials are hydrogen, with no long-chain alkyl substitutions); the remaining raw materials, parameters, and preparation process are the same as in Example 1.

[0090] Specifically, the amount of raw materials added in the above embodiments and comparative examples is shown in Table 1: Table 1

[0091] Note 1. Thickness refers to the overall thickness of the prepared light-converting polyvinyl acetal film; 2. Thickness ratio refers to the ratio of the thickness of the first film and the second film in the prepared light-converting polyvinyl acetal film; 3. In Examples 14, 15, and 16, the chemical structures of the light-converting agent A are structure 2, structure 3, and structure 4, respectively. When structure 2 is used in the light-converting agent A in Example 14, R1 and R3-R7 are hydrogen, and R2 is a C18 straight-chain alkyl substituted agent. When structure 3 is used in the light-converting agent A in Example 15, R2-R8 are hydrogen, and R1 is a C18 straight-chain alkyl substituted agent. When structure 4 is used in the light-converting agent A in Example 16, R1 and R3-R7 are hydrogen, and R2 is a C18 straight-chain alkyl substituted agent.

[0092] 4. In Comparative Example 11, the chemical structure of the light-converting agent A is structure 1; wherein, R1-R 10 All are hydrogen, with no long-chain alkyl substitutions.

[0093] Performance testing

[0094] The excitation and emission spectra, fluorescence quantum efficiency, transmittance, tensile strength and elongation at break, and power of the first and second thin films prepared in Examples 1-16 and Comparative Examples 1-11, as well as the final photovoltaic film, were measured. The measurement methods are as follows: (1) Excitation and emission spectrum test: Place the product to be tested in a fluorescence spectrometer, use 350nm as the excitation wavelength, and scan the emission spectrum range of 400-800nm; use 420nm as the emission wavelength and scan the excitation spectrum range of 250-400nm; (2) Fluorescence quantum efficiency test: The quantum efficiency of the product under test was measured by the integrating sphere of the FLS1000 spectrometer. With 350 nm as the excitation wavelength and a blank quartz cell as a reference, the background signal in the range of 340–750 nm was scanned. An appropriate amount of the product under test was placed in the quartz sample cell, and the absorption and emission signals of the product were scanned. The spectra of the two scans were processed. The difference in the area of ​​the spectral integrated peak in the range of 340–360 nm was the absorption value of the excitation light, and the difference in the area of ​​the spectral integrated peak in the range of 500–750 nm was the emission intensity value. The ratio between the emission intensity value and the absorption value is the photoluminescence quantum efficiency. (3) Light transmittance test: According to the GB / T 2410—2008 light transmittance test standard, the light transmittance of the first layer, the second layer of film and the final photovoltaic film were tested; (4) Tensile strength and elongation at break test: according to the test requirements of national standard GB / T 1040.3-2006; (5) Component power: The test standard is based on IEC61215.

[0095] The relevant performance test results of the first thin film are shown in Table 2: Table 2

[0096] The relevant performance test results of the second thin film are shown in Table 3: Table 3

[0097] The relevant performance test results of photovoltaic films and photovoltaic modules are shown in Table 4: Table 4

[0098] Note: Ultraviolet (UV) light transmittance is an important indicator for evaluating UV leakage in film. Therefore, the lower the UV transmittance value, the better the film's UV absorption capacity. The maximum excitation wavelength is a crucial criterion for evaluating which type of light a film absorbs. The most destructive ultraviolet (UV) wavelength for heterojunction solar cells is in the 280-380 nm range, especially around 360-375 nm. This UV light has energy comparable to that of a silicon-hydrogen bond (Si-H bond), effectively disrupting Si-H bonds and ultimately damaging the heterojunction solar cell's performance. Therefore, the closer the maximum excitation wavelength of the light-converting film is to 360-376 nm, the better its absorption effect on the most destructive UV light. The maximum emission wavelength is an important criterion for evaluating what kind of light the film converts absorbed ultraviolet light into. Blue light's energy is well-matched to the bandgap of heterojunction solar cells, allowing for better absorption and utilization, thus improving the cell's photoelectric conversion efficiency. Compared to other wavelengths, blue light is absorbed and converted more effectively in the cell, increasing its power generation. Therefore, the closer the maximum emission wavelength of the light conversion film is to blue light (400-450nm), the more easily the converted light is absorbed and converted by the heterojunction solar cell. Fluorescence quantum efficiency is one of the core performance indicators of light conversion film products, directly determining the product's effectiveness in practical applications. Its value is directly related to the energy utilization efficiency of the product in the light conversion process. The higher the quantum efficiency, the stronger the ability of the light conversion film to convert ultraviolet light into blue light; Tensile strength and elongation at break are important indicators for evaluating the mechanical properties of light-converting films. The higher the tensile strength and elongation at break, the better the mechanical properties of the light-converting film.

[0099] Based on the data in Tables 2-4, it can be seen that Examples 1-16 adopted a film layer combination approach and effectively controlled the structural formulation of each film layer, enabling the final photovoltaic film product to maintain good performance: the film's ultraviolet light transmittance is below 0.01%, visible light transmittance is above 92%, tensile strength is ≥25.0 MPa, and elongation at break is ≥210; corresponding to a photovoltaic module power increase of ≥1.50%. Based on Comparative Examples 1-3, specifically, in Comparative Example 1, no light-converting agent was added to either of the two thin-film structures; in Comparative Example 2, no light-converting agent B was added to the second thin film; and in Comparative Example 3, no light-converting agent A was added to the first thin film. As can be seen from the test results in Tables 1-3, compared to Example 1, Comparative Example 1 cannot improve the power of the photovoltaic module. In Comparative Example 2, because no light-converting agent was added to the second thin film, the ultraviolet light leaking from the first thin film could not be effectively absorbed again, resulting in significant ultraviolet leakage in the final photovoltaic film, which damages the performance of the photovoltaic module during long-term service. In Comparative Example 3, because no light-converting agent was added to the first thin film, a large amount of ultraviolet light could not be efficiently converted into blue light, ultimately failing to significantly increase the power of the photovoltaic module.

[0100] Based on the data from Example 1, and as can be seen from Comparative Examples 4, 5, and 6, replacing the light-converting agent with an ultraviolet absorber will affect the power of the photovoltaic module to some extent.

[0101] As can be seen from Comparative Example 7 and Example 2, when the low-performance light conversion agent B is replaced with the high-performance light conversion agent A (by increasing the amount of light conversion agent A added), the efficiency of photovoltaic modules can be significantly improved. However, the preparation cost of high-performance light conversion agents is generally high. As the amount of light conversion agent A used increases, the cost of the product also increases, which will be detrimental to industrial production.

[0102] As can be seen from Comparative Examples 8, 9, and 10, the co-solvent for the light conversion agent is one of the keys to fully realizing the performance of the light conversion agent. Without the addition of the light conversion agent, the performance of the corresponding product will be affected to a certain extent.

[0103] As can be seen from Comparative Example 11 and Example 1, the long-chain alkyl structure in the light-converting agent has a significant impact on its performance; the light-converting agent with the long-chain alkyl structure can be uniformly mixed with the fat-soluble plasticizer, thereby being uniformly dispersed in the resin matrix, so that the light-converting film has a high efficiency of ultraviolet absorption and conversion capability.

[0104] As can be seen from the above analysis, the films obtained in Examples 1-16 have better overall performance while controlling costs. Therefore, this invention can simultaneously achieve low UV leakage, high UV conversion, and low cost in photovoltaic films. As can be seen from the data in Table 4, the prepared photovoltaic film not only achieved low ultraviolet leakage and high ultraviolet conversion, but also improved the power of the photovoltaic module.

[0105] Furthermore, according to current market prices, high-performance light conversion agents are generally expensive, while low-performance light conversion agents are significantly cheaper. This invention, through the synergistic effect of different functional layer light conversion films, achieves a significant reduction in the amount of light conversion agent added while ensuring high product performance.

[0106] Therefore, based on the above content and the data in Table 4, the light-converting polyvinyl acetal film prepared by the present invention not only ensures the high performance of the product, but also achieves the goal of significantly reducing production costs.

[0107] This invention provides a light-converting polyvinyl acetal film, employing a double-layer film combination technology to precisely control the formulation and performance parameters of each film layer, ensuring the quality of the prepared light-converting polyvinyl acetal film. Simultaneously, because the amount of light-converting agent added in each film layer is low—for example, in the first film mixture, the amount of light-converting agent A is only 0.01–0.1 parts, meaning the maximum mass percentage of light-converting agent A in the first film mixture is approximately 0.1‰; and in the second film mixture, the amount of light-converting agent B is only 0.1–0.2 parts, meaning the second film mixture… In this material, the maximum mass percentage of light-converting agent B is approximately 0.2‰. Compared to Chinese invention patent CN118027854A, which adds 1-10 parts of light-converting agent per 100 parts of base resin and also includes other additives (such as silane coupling agents and ultraviolet absorbers), the light-converting polyvinyl acetal film provided by this invention significantly reduces the content of light-converting agent. This not only achieves low ultraviolet leakage and high ultraviolet conversion in photovoltaic films, thereby increasing the power of photovoltaic modules, but also significantly reduces production costs, bringing unprecedented economic benefits and enhanced competitiveness to the photovoltaic industry.

[0108] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A light-converting polyvinyl acetal film, characterized in that, It includes a double-layer structure, consisting of a first film and a second film, wherein the first film and the second film are obtained by plasticizing and co-extruding the first film mixture and the second film mixture, respectively; The first layer film mixture comprises the following raw materials in parts by weight: 70-80 parts of polyvinyl acetal resin, 20-30 parts of plasticizer, 0.1-0.8 parts of antioxidant, and 0.01-0.1 parts of light conversion agent A; The second layer film mixture comprises the following raw materials in parts by weight: 70-80 parts of polyvinyl acetal resin, 20-30 parts of plasticizer, 0.1-0.8 parts of antioxidant, 0.1-0.2 parts of light conversion agent B, and 0.1-0.5 parts of light conversion agent cosolvent B.

2. The light-converting polyvinyl acetal film according to claim 1, characterized in that, The thickness ratio of the first thin film to the second thin film is 1:3 to 3:

1.

3. The light-converting polyvinyl acetal film according to claim 1, characterized in that, The thickness of the light-converting polyvinyl alcohol acetal film is 0.18–1.52 mm; The transmittance of the light-converting polyvinyl acetal film for ultraviolet light with a wavelength less than 380 nm is no greater than 0.01%. The visible light transmittance of the light-converting polyvinyl alcohol acetal film is ≥90%.

4. The light-converting polyvinyl acetal film according to claim 1, characterized in that, The fluorescence quantum efficiency of the first thin film is ≥90%, and the transmittance of the first thin film for ultraviolet light with a wavelength less than 380nm is not greater than 20%. The fluorescence quantum efficiency of the second thin film is ≥40%, and the transmittance of the second thin film for ultraviolet light with a wavelength less than 380nm is not greater than 0.1%.

5. The light-converting polyvinyl acetal film according to claim 1, characterized in that, The light-converting agent A is a light-converting agent containing long-chain alkyl groups in its molecule.

6. The light-converting polyvinyl acetal film according to claim 1, characterized in that, The light-converting agent A is any one or more of rare earth organic light-converting agents and organic fluorescent pigments, mixed in any proportion. The light conversion agent B is any one or more of rare earth inorganic light conversion agents and perovskite quantum dots, mixed in any proportion. The light-converting agent co-solvent B is any one or more of silane coupling agents and ester organic compounds, mixed in any proportion.

7. The light-converting polyvinyl acetal film according to claim 1, characterized in that, The hydroxyl value of the polyvinyl acetal resin in the first and second film mixtures is 16.5% to 21.0%, and / or the acetoxy content of the polyvinyl acetal resin in the first and second film mixtures is 0.5% to 2.0%.

8. A method for preparing a light-converting polyvinyl acetal film according to any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: S1. According to the formula of the first layer film mixture, weigh out polyvinyl acetal resin, plasticizer, antioxidant and light conversion agent A, add light conversion agent A and antioxidant to plasticizer, heat to dissolve completely, and prepare plasticized mixture A. S2. According to the formula of the second layer film mixture, weigh out polyvinyl acetal resin, plasticizer, antioxidant, light conversion agent B, and light conversion agent cosolvent B. Heat and mix light conversion agent B and light conversion agent cosolvent B to prepare light conversion dispersion B. Dissolve light conversion dispersion B and antioxidant in plasticizer to prepare plasticized mixture B. S3. Plasticize the plasticized mixture A and the polyvinyl acetal resin provided in step S1 through a first extruder, and plasticize the plasticized mixture B and the polyvinyl acetal resin provided in step S2 through a second extruder, and then form them through a multi-layer co-extrusion die to obtain a bright polyvinyl acetal film.

9. The method for preparing a light-converting polyvinyl acetal film according to claim 8, characterized in that, In step S3, the plasticizing temperature is 110–220°C and the die head temperature is 130–200°C.

10. A photovoltaic module, comprising a glass substrate, a first photovoltaic film, a battery chip, a second photovoltaic film, and a glass substrate stacked sequentially, characterized in that, The first photovoltaic film is the light-converting polyvinyl acetal film according to any one of claims 1 to 7.

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