A bifunctional rare earth light conversion spray paint, a preparation method and application thereof

Abstract

The present application belongs to the field of agricultural light complementation photovoltaic technology and functional coating, and particularly relates to a dual-functional rare earth light conversion spraying coating, a preparation method and application thereof; the spraying coating comprises, in terms of mass fraction, 0.5-1 part of rare earth down-conversion material, 8-15 parts of film-forming resin, 0.05-0.5 part of silane coupling agent and 70-90 parts of dilution solvent; wherein the mass ratio of the film-forming resin to the rare earth down-conversion material is (8-15):1; the prepared spraying coating is directly sprayed on a light-transmitting photovoltaic panel assembly to simultaneously achieve the promotion of light-electricity conversion efficiency of the light-transmitting photovoltaic panel and the promotion of crop growth in the greenhouse, and is suitable for the modification of existing photovoltaic greenhouses.

Description

Technical Field

[0001] This invention relates to the intersection of agricultural photovoltaic technology and functional coatings, specifically to a dual-functional rare earth light-converting spray coating and its preparation method and application. Background Technology

[0002] Photovoltaic greenhouses, which integrate agriculture and solar power, are an important business model for realizing three-dimensional land use and balancing clean energy production with agricultural planting. They have seen rapid adoption in my country in recent years. Currently, photovoltaic greenhouses commonly use translucent photovoltaic modules (double-glass crystalline silicon translucent modules, semi-transparent thin-film modules, etc.) as roof covering materials. However, their operation faces two major industry pain points: Imbalance in the utilization of spectral resources: The spectral response of crystalline silicon photovoltaic cells is concentrated in the 400~1100nm visible-near infrared band. Photons in the 300~400nm ultraviolet band cannot be effectively converted into electrical energy, and long-term ultraviolet irradiation will accelerate the aging of the module encapsulation materials. At the same time, after ultraviolet light in this band passes through the module and enters the greenhouse, not only is the photosynthetic utilization efficiency extremely low, but it is also easy to burn the tender tissues of crops and inhibit crop growth. It belongs to the "double useless" waste band of power generation and planting.

[0003] The conflict between power generation and planting: Photovoltaic power generation will consume some of the photosynthetically active radiation (PAR), resulting in insufficient light for crops in greenhouses, and a decline in yield and quality; existing technical solutions mostly make trade-offs between light transmittance and power generation efficiency, and cannot realize the value-added utilization of spectral resources.

[0004] To address the aforementioned problems, existing technologies have significant limitations: (1) Agricultural light-converting greenhouse film only acts on the inner covering layer of the greenhouse, only optimizes the light quality of crops, does not involve the improvement of photovoltaic power generation efficiency, and cannot directly act on the surface of photovoltaic modules; (2) Conventional photovoltaic light conversion coatings only aim to increase power generation efficiency, and their emission spectrum only matches the response of photovoltaic cells. They do not consider the impact of transmitted light on crop growth and cannot meet the dual needs of agricultural photovoltaic complementary scenarios. (3) Existing light conversion technologies mostly employ processes such as film blending and in-situ glass doping, which are only suitable for the production of new modules and cannot be used for low-cost retrofitting of existing photovoltaic greenhouse modules, resulting in strong limitations in engineering applications.

[0005] Therefore, developing a dual-function light-converting material that can be directly sprayed onto the surface of a light-transmitting photovoltaic panel and simultaneously achieves both power generation efficiency enhancement and crop growth promotion is an urgent need for the upgrading of the photovoltaic greenhouse industry. Summary of the Invention

[0006] To address the shortcomings in the background technology, this invention provides a dual-function rare earth light-converting spray coating, its preparation method, and its application. By directly spraying the prepared coating onto a light-transmitting photovoltaic panel, the photoelectric conversion efficiency of the light-transmitting photovoltaic panel is simultaneously improved, and the growth of crops inside the greenhouse is promoted, making it suitable for the renovation of existing photovoltaic greenhouses.

[0007] To achieve the above objectives, the present invention provides a dual-function rare earth light-conversion spray coating, wherein the spray coating comprises, by weight parts: 0.5 to 1 part of rare earth down-conversion material, 8 to 15 parts of film-forming resin, 0.05 to 0.5 parts of silane coupling agent, and 70 to 90 parts of diluting solvent; wherein the mass ratio of the film-forming resin to the rare earth down-conversion material is (8 to 15): 1.

[0008] Preferably, the chemical composition of the rare earth down-conversion material is (Eu... 0.1 Ce 0.001 La 0.899 (TTA)3(Phen), where TTA is 2-thiophenecarboxyltrifluoroacetone and Phen is 1,10-phenanthroline.

[0009] Preferably, the film-forming resin is a thermoplastic methacrylate resin containing acidic functional groups, with a visible light transmittance ≥90% and a refractive index that matches the refractive index of the rare earth downconverting material. The silane coupling agent is a copolymer dispersant or a polyphosphate dispersant containing acidic groups. Its alkoxy end is used to form a covalent bond with the hydroxyl group on the surface of the rare earth downconversion light-converting material, and its organic long chain end is used to mutually dissolve and entangle with the chain segments of the film-forming resin to form a three-dimensional steric hindrance layer on the surface of the rare earth downconversion light-converting material. The diluent is ethyl acetate.

[0010] A second aspect of the present invention provides a method for preparing a bifunctional rare earth light-converting spray coating, the method comprising: S1. Dissolve the film-forming resin in a diluent to obtain a resin varnish; S2. Take a portion of the resin varnish, add rare earth low-conversion material and silane coupling agent in sequence, and disperse by ultrasonication to obtain a high-conversion concentrated slurry; S3. Add the light-converting concentrated slurry to the remaining resin varnish, stir for 25 min to 35 min, and filter through a 200-mesh filter to obtain the dual-function rare earth light-converting spray coating.

[0011] Preferably, in step S2, the ultrasonic dispersion process is accompanied by magnetic stirring, and the ultrasonic dispersion time is 15 min to 30 min.

[0012] A third aspect of the present invention provides a method for preparing a bifunctional rare-earth light-converting coating, the method comprising: The light-facing surface of the pretreated transparent photovoltaic panel substrate is treated with a silane coupling agent primer, so that the alkoxy end of the silane coupling agent forms a Si-O-Si covalent bond with the silanol group on the surface of the transparent photovoltaic panel. The above-mentioned dual-functional rare earth light-converting spray coating is uniformly sprayed onto the surface of the light-transmitting photovoltaic panel substrate that has been primed, and the light-converting coating is obtained after curing into a film.

[0013] Preferably, the spraying is performed in 2 to 3 coats, with a 5-minute interval between each coat; the curing is performed by drying at room temperature for 48 hours.

[0014] Preferably, the thickness of the light-converting coating is 40μm~50μm.

[0015] The fourth aspect of this invention provides the application of the above-mentioned dual-functional rare earth light-converting spray coating in agricultural photovoltaic integration. The dual-functional rare earth light-converting spray coating is sprayed on the light-facing surface of photovoltaic glass. The rare earth down-conversion light-converting material converts ultraviolet light into 612 nm characteristic red light. The 612 nm red light matches the spectral response of silicon-based photovoltaic cells and the spectrum required for plant photosynthesis, thereby unifying the dual functions of increasing the power generation efficiency of photovoltaic modules and promoting the growth of crops under the photovoltaic panels.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention concentrates the emission spectrum in the characteristic red light region of 612nm. This wavelength is located in the peak region of the spectral response of silicon-based photovoltaic cells and the red light absorption peak region of plant chlorophyll. It is highly matched with the spectrum required for plant photosynthesis. In the agricultural-photovoltaic complementary mode of planting crops under photovoltaic panels, the coating of this invention converts harmful ultraviolet rays into red light, while taking into account the power generation benefits of photovoltaic modules and the growth needs of crops, thus solving the contradiction of competing for light in traditional photovoltaic agriculture. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention, wherein: Figure 1 This is the emission spectrum of the coating provided in Embodiment 1 of the present invention under 300 nm excitation.

[0018] Figure 2 These are the solar power meter test data fitting curves provided in Embodiment 1, Comparative Example 1, and Comparative Examples 3-4 of the present invention.

[0019] Figure 3 This is a bar chart comparing the plant height, stem diameter, leaf area, and chlorophyll content of the crop in Example 1 of this invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0021] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the specification and in the relevant art, and shall not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein.

[0022] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This invention addresses the current conflict between photovoltaic cells and solar energy competition for light in agriculture. To achieve the increased utilization of spectral resources, it provides a dual-functional rare earth light-conversion spray coating, which comprises, by mass: 0.5-1 parts rare earth light-conversion material, 8-15 parts film-forming resin, 0.05-0.5 parts silane coupling agent, and 70-90 parts diluent. More preferably, the spray coating comprises, by weight: 1 part rare earth down-conversion material, 10 parts film-forming resin, 0.1 part silane coupling agent, and 80 parts diluent; The preferred mass ratio of the film-forming resin to the rare-earth lower-conversion material is (8~15):1, for example, 8:1, 9:1, 10:1, 12:1, 14:1, or 15:1; the chemical composition of the rare-earth lower-conversion material is (Eu... 0.1 Ce 0.001 La 0.899 (TTA)3 (Phen); The film-forming resin is a thermoplastic methacrylic resin containing acidic functional groups, with a visible light transmittance of ≥90% and a refractive index that matches that of rare earth downconverting materials. In some embodiments of the present invention, the film-forming resin is preferably methyl methacrylate / n-butyl methacrylate resin with a molecular weight of 68,000 g / mol, an acid value of 7.5 mg KOH / g, and a glass transition temperature of 58°C.

[0024] Silane coupling agents are copolymer dispersants or polyphosphate dispersants containing acidic groups. Their alkoxy ends are used to form covalent bonds with the hydroxyl groups on the surface of rare earth downconversion light-converting materials, and their organic long chain ends are used to intersolublely entangle with the chain segments of the film-forming resin, forming a three-dimensional steric hindrance layer on the surface of rare earth downconversion light-converting materials. In some embodiments of the present invention, the silane coupling agent preferably is BYK-111 (chemical composition: copolymer solution containing acidic groups) to improve the dispersibility of the light-converting material in the resin.

[0025] The diluent is ethyl acetate.

[0026] Among them, rare earth downconversion materials (Eu) 0.1 Ce 0.001 La 0.899 The preparation process of (TTA)3(Phen) is as follows: Lanthanum salt, cerium salt, europium salt, 2-thiophenecarboxyltrifluoroacetone, and 1,10-phenanthroline are weighed according to the composition ratio, wherein the molar ratio of 2-thiophenecarboxyltrifluoroacetone to the total amount of rare earth ions is 3:1, and the molar ratio of 1,10-phenanthroline to the total amount of rare earth ions is 1:1; 2-thiophenecarboxyltrifluoroacetone and 1,10-phenanthroline are dissolved in anhydrous ethanol and stirred until completely dissolved to obtain a ligand solution; lanthanum salt, cerium salt, and europium salt are dissolved in anhydrous ethanol and stirred... The mixture was dissolved completely to obtain a mixed rare earth salt solution. Under stirring conditions (stirring rate of 600 rpm), the mixed rare earth salt solution was slowly added dropwise to the ligand solution (dropping rate of 1-3 drops / second), while adjusting the pH to 6.5-7.5 with an alkaline solution. The reaction temperature was controlled at 20℃, and the reaction time was 40 minutes. After the reaction, the resulting precipitate was filtered and washed 2-4 times successively with anhydrous ethanol and anhydrous diethyl ether, and then dried in a vacuum drying oven at 40℃ for 12 hours to obtain the rare earth downconversion material (Eu). 0.1 Ce 0.001 La 0.899 (TTA)3(Phen).

[0027] The preparation method of the above-mentioned dual-functional rare earth light-converting spray coating includes: S1. Dissolve the acrylic resin in a diluent and stir at medium speed until the resin is completely dissolved to obtain a uniform and transparent resin varnish. S2. Take a portion of the resin varnish, add rare earth low-conversion material powder and silane coupling agent in sequence, and premix with magnetic stirring combined with ultrasonic dispersion for 15 min to 30 min to obtain a highly dispersible high-conversion concentrated slurry; the parameters of the ultrasonic dispersion process are: ultrasonic frequency of 20 to 40 kHz and ultrasonic power of 100 to 300 W. S3. Add the concentrated slurry to the remaining resin varnish and stir for 25-35 minutes to ensure that the functional powder is evenly dispersed in the resin matrix. Filter through a 200-mesh filter to remove trace powder agglomerates and mechanical impurities, and obtain a dual-function rare earth light-converting spray coating that can be directly used for spraying.

[0028] The prepared bifunctional rare earth light-converting coating is sprayed onto the light-facing surface of a light-transmitting photovoltaic panel (a double-glass crystalline silicon light-transmitting module for photovoltaic greenhouses) to form a bifunctional rare earth light-converting coating. The specific process is as follows: First, pre-treat the light-transmitting photovoltaic panel by cleaning the surface of the panel with anhydrous ethanol to remove dust and oil, ensuring the surface is dry and clean. A silane coupling agent primer was applied to the surface of the pretreated transparent photovoltaic panel. A 1% silane coupling agent ethanol solution was sprayed on the surface and dried at room temperature for 15 minutes to allow the silane coupling agent to form Si-O-Si covalent bonds with the silanol groups on the surface of the transparent photovoltaic panel. The above-mentioned dual-functional rare earth light-converting coating is uniformly sprayed onto the surface of a translucent photovoltaic panel substrate that has undergone primer treatment. Two to three coats are applied, with a 5-minute interval between each coat. After curing (drying at room temperature for 48 hours), a uniform and transparent light-converting coating is obtained. The thickness of the resulting light-converting coating is preferably 40 μm to 50 μm. The silane coupling agent in the primer and the cured coating of the dual-functional rare earth light-converting coating form a gradient interface structure of glass-primer coupling agent-coating resin through molecular entanglement and chemical bonding. One end of the primer silane forms a Si-O-Si covalent bond with the silanol groups on the photovoltaic glass surface, while the other end extends towards the coating side, forming molecular entanglement and chemical bonding with the acrylic resin and silane coupling agent in the coating. This eliminates the weak interface layer between the coating and the glass, significantly improving adhesion and water and weather resistance, while reducing reflection loss caused by interfacial air gaps.

[0029] In some embodiments of the present invention, the strategy of using the rare earth light-converting spray coating to form a coating on the surface of a light-transmitting photovoltaic panel to achieve the enhanced utilization of spectral resources is as follows: the rare earth light-converting material (Eu) used is... 0.1 Ce 0.001 La 0.899(TTA)3 (Phen) efficiently converts ultraviolet light into characteristic red light at 612nm. This wavelength is located in both the spectral response peak region of silicon-based photovoltaic cells and the red light absorption peak region of plant chlorophyll a / b, unifying the dual functions from the perspective of light source. Combined with thermoplastic acrylic resin, its visible light region is highly transparent and its refractive index is similar to that of the rare earth downconversion material (Eu) used. 0.1 Ce 0.001 La 0.899 The difference between (TTA)3 and (Phen) is extremely small, ensuring that 612nm red light can be emitted from the coating with maximum transmittance, so that it can be efficiently utilized by photovoltaic cells and plant leaves respectively. The silane coupling agent used is BYK-111. After the alkoxy end of the silane is hydrolyzed, it forms a covalent bond with the hydroxyl group on the surface of the light-converting material. The organic long chain end is mutually soluble and entangled with the acrylic resin chain segment, forming a three-dimensional steric hindrance layer on the powder surface, preventing particle agglomeration and sedimentation, while improving the interfacial compatibility between the powder and the resin, reducing interfacial light scattering, so that more effective red light can penetrate. The 612nm red light increases the photocurrent of silicon-based cells, achieving efficiency enhancement, and at the same time promotes plant photosynthesis, achieving growth promotion. In the scenario of agricultural photovoltaic complementarity, the coating can take into account both the power conversion efficiency and the crop growth needs, effectively solving the contradiction of light competition in the traditional photovoltaic industry.

[0030] The present invention will be further described below through specific embodiments.

[0031] Example 1 The spray coating used in this embodiment comprises, by weight: 1 part rare earth down-conversion material (Eu). 0.1 Ce 0.001 La 0.899 (TTA)3(Phen), 10 parts methyl methacrylate / n-butyl methacrylate resin, 0.1 parts silane coupling agent (BYK-111), 80 parts ethyl acetate.

[0032] The process of forming a coating on the surface of a light-transmitting photovoltaic panel in this embodiment is as follows: S1. Dissolve methyl methacrylate / n-butyl methacrylate resin in ethyl acetate solvent and stir at medium speed until the resin is completely dissolved to obtain a uniform and transparent resin varnish. S2. Take a portion of the resin varnish and add rare earth down-conversion material (Eu) sequentially. 0.1 Ce 0.001 La 0.899 (TTA)3 (Phen) powder and silane coupling agent BYK-111 were premixed with magnetic stirring and ultrasonically dispersed for 30 min to obtain a highly dispersible, light-converting concentrated slurry; the parameters of the ultrasonic dispersion process were: ultrasonic frequency of 30 kHz and ultrasonic power of 180 W. S3. Add the concentrated slurry to the remaining resin varnish and stir for 30 minutes to ensure that the functional powder is evenly dispersed in the resin matrix. Filter through a 200-mesh filter to remove trace powder agglomerates and mechanical impurities, and obtain a dual-function rare earth light-converting spray coating that can be directly used for spraying.

[0033] S4. Pre-treat the light-transmitting photovoltaic panel by cleaning the surface of the panel with anhydrous ethanol to remove dust and oil, ensuring the surface is dry and clean. S5. Apply silane coupling agent BYK-111 as a primer to the light-facing surface of the pretreated photovoltaic panel, spray with 1% silane coupling agent ethanol solution, and dry at room temperature for 15 minutes. S6. Apply three coats of coating evenly to the surface of the light-transmitting photovoltaic panel substrate after primer treatment, with a 5-minute interval between each coat. After drying at room temperature for 48 hours, a uniform and transparent light-converting coating with a thickness of 50 μm is obtained.

[0034] Example 2 The spray coating used in this embodiment comprises, by weight: 0.6 parts of rare earth down-conversion material (Eu). 0.1 Ce 0.001 La 0.899 (TTA)3 (Phen), 9 parts methyl methacrylate / n-butyl methacrylate resin, 0.1 parts silane coupling agent (BYK-111), 80 parts ethyl acetate.

[0035] The process of forming a coating on the surface of a light-transmitting photovoltaic panel in this embodiment is as follows: S1. Dissolve methyl methacrylate / n-butyl methacrylate resin in ethyl acetate solvent and stir at medium speed until the resin is completely dissolved to obtain a uniform and transparent resin varnish. S2. Take a portion of the resin varnish and add rare earth down-conversion material (Eu) sequentially. 0.1 Ce 0.001 La 0.899 (TTA)3 (Phen) powder and silane coupling agent BYK-111 were premixed with magnetic stirring and ultrasonically dispersed for 30 min to obtain a highly dispersible, light-converting concentrated slurry; the parameters of the ultrasonic dispersion process were: ultrasonic frequency of 30 kHz and ultrasonic power of 180 W. S3. Add the concentrated slurry to the remaining resin varnish and stir for 30 minutes to ensure that the functional powder is evenly dispersed in the resin matrix. Filter through a 200-mesh filter to remove trace powder agglomerates and mechanical impurities, and obtain a dual-function rare earth light-converting spray coating that can be directly used for spraying.

[0036] S4. Pre-treat the light-transmitting photovoltaic panel by cleaning the surface of the panel with anhydrous ethanol to remove dust and oil, ensuring the surface is dry and clean. S5. Apply silane coupling agent BYK-111 as a primer to the light-facing surface of the pretreated photovoltaic panel, spray with 1% silane coupling agent ethanol solution, and dry at room temperature for 15 minutes. S6. Apply three coats of coating evenly to the surface of the light-transmitting photovoltaic panel substrate after primer treatment, with a 5-minute interval between each coat. After drying at room temperature for 48 hours, a uniform and transparent light-converting coating with a thickness of 40 μm is obtained.

[0037] Comparative Example 1 The preparation of the spray coating is the same as in Example 1, except that the coating is sprayed onto the back side of the light-transmitting photovoltaic panel.

[0038] Comparative Example 2 The coating was prepared in the same manner as in Example 1, except that the spray coating consisted of the following components by mass: 10 parts methyl methacrylate / n-butyl methacrylate resin, 0.1 parts silane coupling agent (BYK-111), and 80 parts ethyl acetate.

[0039] Comparative Example 3 The preparation of the coating is the same as in Example 1, except that the sprayed coating comprises, by mass, 1.5 parts of rare earth down-conversion material (Eu). 0.1 Ce 0.001 La 0.899 (TTA)3(Phen), 12 parts methyl methacrylate / n-butyl methacrylate resin, 0.1 parts silane coupling agent (BYK-111), 80 parts ethyl acetate.

[0040] Comparative Example 4 The preparation of the spray coating is the same as in Example 1, except that step S5, the silane coupling agent primer treatment, is omitted, and the coating is directly sprayed onto the photovoltaic glass surface.

[0041] Test case The photovoltaic modules with coatings in Examples 1-2 and Comparative Examples 1-4 were tested for photovoltaic conversion efficiency under standard test conditions. The growth of alfalfa under a photovoltaic greenhouse for 35 days was also tested. The test results are shown in Table 1. The control group was the substrate without coating.

[0042] Table 1 ; The test method in the table above is as follows: Photovoltaic conversion efficiency was measured directly on the other side of the photovoltaic glass under natural sunlight using a solar power meter (SM206plus).

[0043] The plant height of the crop was measured using a ruler, starting from the interface between the crop roots and the soil and ending at the top of the plant. In each sample, multiple representative plants were randomly selected for repeated measurements. All measurements were then summed and their arithmetic mean was calculated as the final result.

[0044] During the measurement of crop stem diameter, vernier calipers are used to measure the diameter of the stem at the base of the plant. It is ensured that the measurement position of all samples is consistent. The measurement is carried out at a fixed height above the base. Each stem is measured several times at the same position, and the average value of the multiple measurements is taken as the data of the stem diameter.

[0045] Leaf area measurement of crops is carried out using a leaf area meter to accurately measure the area of ​​functional leaves. When the leaf size is smaller than the measurement range of the leaf area meter, the graph paper method is used. The leaf is laid flat on the graph paper, its outer edge outline is traced, and the number of complete squares and edge squares covered within the outline are counted to calculate the leaf area value.

[0046] The chlorophyll content of crops was measured on functional leaves using a SPAD-502 chlorophyll meter. Multiple readings were taken from different locations on the same leaf, and the average value was taken as the SPAD value of the leaf.

[0047] Figure 1 The coating of Example 1 exhibits the strongest characteristic red light emission under 300nm ultraviolet light excitation. It can be seen that the coating has obvious emission peaks near 594nm, 612nm and 695nm, effectively converting ultraviolet light into 612nm characteristic red light.

[0048] Based on the data in Table 1, Figure 2 Solar power meter test data fitting curve and Figure 3It can be seen that, under standard test conditions, Example 1 showed a relative improvement of ≥5% in the photoelectric conversion efficiency of the transparent photovoltaic panel. This was verified through a 35-day planting trial, showing that compared to the control group, the crop height, stem diameter, leaf area, and chlorophyll content increased by 54.5%, 24.4%, and 16.7%, respectively. Compared to the control group, the light conversion efficiency was 12.6%, significantly promoting crop vegetative growth and photosynthetic physiological efficiency. However, in Comparative Example 1, where the coating was sprayed onto the back side of a translucent photovoltaic panel, although it had a light conversion function, the back side could not receive the ultraviolet components in the incident sunlight. The ultraviolet light was absorbed or reflected by the photovoltaic panel itself, and only a small amount of transmitted light was observed on the back side. The light conversion material was almost ineffective, and the coating on the back side increased absorption loss in the light path, resulting in a decrease in photoelectric conversion efficiency compared to the control group. Crop growth was also inhibited due to reduced light. In Example 2, with a rare earth element content of 0.5 parts of light conversion material, the photoelectric conversion efficiency, crop height, stem diameter, leaf area, and chlorophyll content were improved compared to the control group, but the improvement was smaller than in Example 3. In Comparative Example 3, with a rare earth element content of 1.5 parts of light conversion material, the excessive nanoparticles were difficult to disperse fully, inducing a concentration quenching effect and exacerbating the coating light... Scattering loss and optical loss exceeded the light conversion gain, resulting in a decrease in the output efficiency of photovoltaic devices. The photoelectric conversion efficiency, crop height, stem diameter, leaf area, and chlorophyll content were lower than those of the control group. Comparative Example 2 did not contain rare earth light conversion materials, so the coating did not have light conversion capabilities. The coating itself introduced a slight Fresnel reflection loss. Since the resin refractive index was close to that of glass and the coating was extremely thin, it had almost no impact on the photoelectric conversion efficiency and crop growth. Therefore, the indicators of Comparative Example 2 were basically the same as those of the control group (approximately 0% difference). Comparative Example 4 lacked a silane coupling agent primer, so the coating and the transparent photovoltaic panel lacked Si-O-Si covalent bond chemical anchoring. It relied solely on physical adhesion, which had a certain light conversion effect, but the adhesion was poor. At the same time, there was an air gap at the interface between the coating and the glass, which increased the Fresnel reflection loss. Therefore, the power generation efficiency and crop indicators of Comparative Example 4 were slightly improved compared to the control group, but far inferior to those of Example 1.

[0049] The embodiments given above are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions or substitutions made by those skilled in the art based on the technical features of the present invention are within the protection scope of the present invention.

Claims

1. A dual-functional rare earth light-converting spray coating, characterized in that, The spray coating comprises, by weight parts: 0.5 to 1 part rare earth down-conversion material, 8 to 15 parts film-forming resin, 0.05 to 0.5 parts silane coupling agent, and 70 to 90 parts diluent; wherein the mass ratio of the film-forming resin to the rare earth down-conversion material is (8 to 15):

1.

2. The dual-functional rare earth light-converting spray coating according to claim 1, characterized in that, The chemical composition of the rare earth down-conversion material is (Eu) 0.1 Ce 0.001 La 0.899 (TTA)3(Phen).

3. The dual-functional rare earth light-converting spray coating according to claim 1, characterized in that, The film-forming resin is a thermoplastic methacrylate resin containing acidic functional groups, with a visible light transmittance ≥90% and a refractive index that matches that of the rare earth downconverting material. The silane coupling agent is a copolymer dispersant or a polyphosphate dispersant containing acidic groups. Its alkoxy end is used to form a covalent bond with the hydroxyl group on the surface of the rare earth downconversion light-converting material, and its organic long chain end is used to mutually dissolve and entangle with the chain segments of the film-forming resin to form a three-dimensional steric hindrance layer on the surface of the rare earth downconversion light-converting material. The diluent is ethyl acetate.

4. The preparation method of a bifunctional rare earth light-converting spray coating as described in any one of claims 1 to 3, characterized in that, The preparation method of the coating includes: S1. Dissolve the film-forming resin in a diluent to obtain a resin varnish; S2. Take a portion of the resin varnish, add rare earth low-conversion material and silane coupling agent in sequence, and disperse by ultrasonication to obtain a high-conversion concentrated slurry; S3. Add the light-converting concentrated slurry to the remaining resin varnish, stir for 25 min to 35 min, and filter through a 200-mesh filter to obtain the dual-function rare earth light-converting spray coating.

5. The preparation method of a dual-functional rare earth light-converting spray coating according to claim 4, characterized in that, In step S2, the ultrasonic dispersion process is accompanied by magnetic stirring, and the ultrasonic dispersion time is 15 min to 30 min.

6. A method for preparing a bifunctional rare earth light-conversion coating, characterized in that, The method for preparing the coating includes: The light-facing surface of the pretreated transparent photovoltaic panel substrate is treated with a silane coupling agent primer, so that the alkoxy end of the silane coupling agent forms a Si-O-Si covalent bond with the silanol group on the surface of the transparent photovoltaic panel. A dual-functional rare earth light-converting spray coating as described in any one of claims 1 to 3 is uniformly sprayed onto the surface of a light-transmitting photovoltaic panel substrate that has undergone primer treatment, and the light-converting coating is obtained after curing into a film.

7. The method for preparing a bifunctional rare earth light-conversion coating according to claim 6, characterized in that, The spraying process involves 2-3 coats, with a 5-minute interval between each coat; the curing process involves drying at room temperature for 48 hours.

8. The method for preparing a bifunctional rare earth light-conversion coating according to claim 6, characterized in that, The thickness of the light-converting coating is 40μm~50μm.

9. The application of the bifunctional rare earth light-converting spray coating as described in any one of claims 1 to 3 or the bifunctional rare earth light-converting coating prepared by the method described in claim 6 in agricultural-photovoltaic complementary systems, characterized in that, The dual-function rare earth light-converting coating is sprayed onto the light-facing surface of the photovoltaic glass. The rare earth down-conversion light-converting material converts ultraviolet light into 612 nm characteristic red light. The 612 nm red light matches the spectral response of silicon-based photovoltaic cells and the spectrum required for plant photosynthesis, thus unifying the dual functions of increasing photovoltaic module power generation efficiency and promoting crop growth under the photovoltaic panel.

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