Photovoltaic high-dispersion carbon quantum dot-based light conversion film and preparation method thereof

Abstract

The invention discloses a photovoltaic high-dispersion carbon quantum dot-based light conversion film and a preparation method thereof, and the preparation method comprises the following steps: dissolving ethylenediamine in a citric acid aqueous solution, adding ammonia water, uniformly stirring, adding a VAE emulsion, reacting, adding dodecyl ethyoxyl sulphobetaine, stirring and dispersing, filtering, washing, and drying to obtain the high-dispersion carbon quantum dot-based light conversion film. C / VAE composite particle dispersion solution is formed and atomized into fog drops, vacuum airflow drying is carried out, obtained carbon quantum dot / VAE composite powder and EVA or POE are stirred and mixed evenly, extrusion granulation is carried out through an extruder to obtain carbon quantum dot / VAE / EVA or carbon quantum dot / VAE / POE composite light conversion master batches, heating is carried out in a trough to form a molten state, the molten state flows to a base band to form a wet band, gradual curing and cooling are carried out in a drying chamber, and the light conversion material is obtained. And the cured and formed film is used together with the base band or is separated from the reel from the base band for later use. According to the invention, a novel process is adopted to prepare the photovoltaic carbon quantum dot-based light conversion film with high down-conversion property, high transparency, high stability and low cost, and the photovoltaic carbon quantum dot-based light conversion film is suitable for common crystalline silicon cells in the market, such as monocrystalline silicon cells, polycrystalline silicon cells, heterojunction cells and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of light conversion film preparation, and in particular to a highly dispersed carbon quantum dot-based light conversion film for photovoltaics and a preparation method thereof. Background Art

[0002] At present, more than 85% of the photovoltaic modules produced in the world each year are crystalline silicon photovoltaic modules. The reason why crystalline silicon photovoltaic modules can occupy the vast majority of the market share is determined by the long life, abundant sources and non-toxicity of this type of photovoltaic module. The cell efficiency of silicon-based solar cells is generally 15% to 20%, which is still a certain distance from the theoretical limit efficiency of 31% of Shockley-Queisser single-cell solar cells. This is because the current crystalline silicon solar cells mainly absorb light around 400 to 1100nm, and the quantum efficiency of light below 400nm (i.e., purple light and ultraviolet light) is very low. At the same time, single crystal silicon responds better to long wavelengths. Therefore, by making full use of solar energy below 400nm through reasonable means and converting it into long-wave light above 400nm, the photoelectric conversion efficiency of solar cells can be effectively improved. In addition, adding down-conversion luminescent materials to solar encapsulation films can also reduce the aging rate of encapsulation films in outdoor environments and increase the life of solar cell modules. In addition, the new generation of photovoltaic cells (such as heterojunctions, etc.) are very sensitive to ultraviolet light. Under the action of ultraviolet sunlight, the cells are damaged, thereby shortening their service life. In summary, the use of light conversion agent composite film in photovoltaic modules is expected to greatly improve the service life and light conversion efficiency of photovoltaic modules.

[0003] The core technology of photovoltaic photoconverter composite film lies in the synthesis and preparation of high-performance photoconverters and their uniform dispersion and compounding in the film. Currently, publicly reported photoconverters include metal oxide quantum dots, rare earth oxides, rare earth organic complexes, organic compounds and carbon quantum dots. Among them, metal oxide quantum dots and rare earth oxide photoconverters have stable structures and low prices, but narrow ultraviolet absorption wavelength ranges and low quantum efficiency; rare earth organic complexes and organic compounds have wide ultraviolet absorption ranges and high quantum efficiency, but low structural stability and high prices. Carbon quantum dots not only have good structural stability, but also have adjustable prices, ultraviolet absorption and quantum efficiency, making them the photoconverters with the most application prospects in the photovoltaic field.

[0004] At present, there have been many reports on the synthesis of carbon quantum dots, and there are related studies or literature reports on the application of carbon quantum dots in photovoltaic light conversion films. However, there are still the following difficulties for light conversion agents used in the photovoltaic field. Existing carbon quantum dots are still difficult to meet the requirements of wide ultraviolet absorption, non-absorption of visible light and high quantum efficiency at the same time; the existing carbon quantum dot preparation process involves steps such as synthesis, purification and collection, and each step is relatively complicated, which not only leads to a significant increase in cost, but also makes it difficult to prepare in large quantities; carbon quantum dots are small in size (a few nanometers) and are generally prepared in solvents. Due to the existence of nano-surface effects, carbon quantum dots are prone to form irreversible agglomerates during extraction and dispersion in the resin matrix, which not only leads to a decrease in luminescence performance, but also greatly reduces the transmittance of the film. In summary, carbon quantum dot-based light conversion films have not yet been commercialized, and the preparation of photovoltaic light conversion films with high down-conversion, high transparency, high stability and low cost is still one of the most challenging topics in this field.

[0005] Therefore, based on the above needs and problems, the present invention provides a highly dispersed carbon quantum dot-based light conversion film for photovoltaics and a preparation method thereof, and adopts a new process to prepare a highly convertible, highly transparent, highly stable, and low-cost carbon quantum dot-based light conversion film for photovoltaics, which can be applicable to common crystalline silicon cells on the market, such as single crystal silicon cells, polycrystalline silicon cells, and heterojunction cells. Summary of the invention

[0006] The purpose of the present invention is to provide a highly dispersed carbon quantum dot-based light conversion film for photovoltaics and a preparation method thereof, so as to fill the gap in the current technology.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaics comprises the following steps:

[0009] (1) Weighing citric acid and dissolving it in deionized water by ultrasonic to obtain a citric acid aqueous solution, measuring ethylenediamine and dissolving it in the citric acid aqueous solution, adding ammonia water and stirring evenly, adding VAE emulsion, stirring to form a uniform reaction precursor, transferring the reaction precursor to a reaction kettle, heating it in an oven and then cooling it, adding dodecylethoxysulfobetaine, stirring and dispersing it at room temperature, and coating the surface of VAE particles with carbon quantum dots to form a C / VAE composite particle dispersion solution;

[0010] (2) using an ejector to atomize the C / VAE composite particle dispersion solution obtained in step (1) into droplets, mixing with a countercurrent gas at -70°C for instant contact, achieving rapid freezing of individual particles, forming a fluidized state under the action of the -20°C gas for primary drying, and the particles that meet the requirements enter the secondary stage to achieve vacuum airflow drying at room temperature to obtain carbon quantum dot / VAE composite powder;

[0011] (3) the carbon quantum dot / VAE composite powder obtained in step (2) is mixed evenly with EVA or POE by a disperser, and then extruded and granulated by a twin-screw extruder to obtain a carbon quantum dot / VAE / EVA composite light-conversion masterbatch or a carbon quantum dot / VAE / POE composite light-conversion masterbatch;

[0012] (4) The composite light-converting masterbatch obtained in step (3) is heated in a material tank to form a molten state, which flows onto the base tape, and forms a wet tape through the relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a drying chamber, and the solidified film is removed from the reel together with the base tape or from the base tape for standby use.

[0013] Preferably, in step (1), the concentration of ethylenediamine is 0.2 mol / L to 0.8 mol / L; the concentration of aqueous ammonia is 0.8 mol / L to 3.2 mol / L, more preferably 0.8 mol / L, 1.6 mol / L, 3.2 mol / L; the viscosity of the VAE emulsion is in the range of 20% to 40%, and the diameter of the VAE emulsion is in the range of 300 nm to 1000 nm.

[0014] Preferably, in step (1), the heating condition in the oven is heating at 160° C. to 180° C. for 3 h to 4 h; and dodecyl ethoxy sulfobetaine is added and stirred and dispersed at room temperature for 1 h to 2 h.

[0015] Further preferably, in step (1), the heating condition in the oven is heating at 160-165° C. for 3 hours; and dodecylethoxysulfobetaine is added and stirred and dispersed at room temperature for 1 hour.

[0016] Preferably, in step (2), the carbon quantum dot content in the obtained carbon quantum dot / VAE composite powder is 1 wt% to 5 wt%.

[0017] Preferably, in step (3), the segmented temperature-controlled extrusion temperature of the twin-screw extruder is 80°C to 90°C, 100°C to 115°C, the main screw speed is 150 to 200 r / min, and the feeding screw speed is 5 to 8 r / min.

[0018] Preferably, in step (3), the carbon quantum dot content in the composite light conversion masterbatch is 0.1wt% to 0.5wt%.

[0019] Preferably, in step (4), the light conversion masterbatch is heated to 220°C to 240°C in a material tank; and is gradually solidified and cooled in a drying chamber at three stages of 110°C to 150°C, 70°C to 90°C, and 30°C to 50°C.

[0020] The present application also claims protection for a highly dispersed carbon quantum dot-based light conversion film for photovoltaics, which is prepared using the above-mentioned method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaics.

[0021] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0022] The highly dispersed carbon quantum dot-based photovoltaic light conversion film and the preparation method thereof provided by the present invention adopt a new process to prepare a high-conversion, high-transparency, high-stability, low-cost photovoltaic carbon quantum dot-based light conversion film, which can be applicable to common crystalline silicon cells on the market, such as single crystal silicon cells, polycrystalline silicon cells, and heterojunction cells. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, a specific implementation scheme is now described in detail.

[0024] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to the different requirements of specific use, and the implementation conditions not indicated are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0025] Example 1

[0026] This embodiment provides a method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaics, comprising the following steps:

[0027] (1) Weigh 2.5 g of citric acid and dissolve it in 5 mL of deionized water by ultrasonic to obtain a citric acid aqueous solution. Use a pipette to measure 125 μL of ethylenediamine (the concentration of ethylenediamine is 0.5 mol / L) and dissolve it in the citric acid aqueous solution. Add ammonia water (0.8 mol / L) and stir evenly. Add 33.5 g of VAE emulsion (the viscosity of the VAE emulsion is 30%, and the diameter of the VAE emulsion is in the size range of 500 nm) and stir to form a uniform reaction precursor. Transfer the reaction precursor to a reactor, heat it in an oven at 160° C. for 3 hours, and then cool it. Add 0.6 g of dodecylethoxysulfobetaine and stir and disperse it at room temperature for 1 hour. The carbon quantum dots coat the surface of the VAE particles to form a C / VAE composite particle dispersion solution.

[0028] (2) using an ejector to atomize the C / VAE composite particle dispersion solution obtained in step (1) into droplets, mixing with a countercurrent gas at -70°C for instant contact, achieving rapid freezing of individual particles, forming a fluidized state under the action of the -20°C gas for primary drying, and the particles that meet the requirements enter the secondary stage to achieve vacuum airflow drying at room temperature to obtain a carbon quantum dot / VAE composite powder, wherein the carbon quantum dot content is 5wt%;

[0029] (3) the carbon quantum dot / VAE composite powder obtained in step (2) is mixed evenly with EVA or POE by a disperser, and then extruded and granulated by a twin-screw extruder (the segmented temperature control extrusion temperature of the twin-screw extruder is 85° C., 110° C., the main screw speed is 180 r / min, and the feeding screw speed is 6 r / min) to obtain a carbon quantum dot / VAE / EVA composite light-conversion masterbatch or a carbon quantum dot / VAE / POE composite light-conversion masterbatch, wherein the carbon quantum dot content is 0.5wt%;

[0030] (4) The composite light-converting masterbatch obtained in step (3) is heated to 240° C. in a material tank to form a molten state, which is then flowed onto the base tape. A wet tape is formed by relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a three-stage drying chamber at 130° C., 80° C., and 40° C. The solidified film is removed from the reel together with the base tape or from the base tape for standby use.

[0031] Example 2

[0032] This embodiment provides a method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaics, comprising the following steps:

[0033] (1) Weigh 2.5 g of citric acid and dissolve it in 5 mL of deionized water by ultrasonic to obtain a citric acid aqueous solution. Use a pipette to measure 125 μL of ethylenediamine (the concentration of ethylenediamine is 0.5 mol / L) and dissolve it in the citric acid aqueous solution. Add ammonia water (1.6 mol / L) and stir evenly. Add 33.5 g of VAE emulsion (the viscosity of the VAE emulsion is 30%, and the diameter of the VAE emulsion is in the size range of 500 nm) and stir to form a uniform reaction precursor. Transfer the reaction precursor to a reactor, heat it in an oven at 160° C. for 3 hours, and then cool it. Add 0.6 g of dodecylethoxysulfobetaine and stir and disperse it at room temperature for 1 hour. The carbon quantum dots cover the surface of the VAE particles to form a C / VAE composite particle dispersion solution.

[0034] (2) using an ejector to atomize the C / VAE composite particle dispersion solution obtained in step (1) into droplets, mixing with a countercurrent gas at -70°C for instant contact, achieving rapid freezing of individual particles, forming a fluidized state under the action of the -20°C gas for primary drying, and the particles that meet the requirements enter the secondary stage to achieve vacuum airflow drying at room temperature to obtain a carbon quantum dot / VAE composite powder, wherein the carbon quantum dot content is 4wt%;

[0035] (3) The carbon quantum dot / VAE composite powder obtained in step (2) is mixed evenly with EVA or POE by a disperser, and then extruded and granulated by a twin-screw extruder (the segmented temperature control extrusion temperature of the twin-screw extruder is 85° C., 110° C., the main screw speed is 180 r / min, and the feeding screw speed is 6 r / min) to obtain a carbon quantum dot / VAE / EVA composite light-conversion masterbatch or a carbon quantum dot / VAE / POE composite light-conversion masterbatch, wherein the carbon quantum dot content is 0.45wt%;

[0036] (4) The composite light-converting masterbatch obtained in step (3) is heated to 240° C. in a material tank to form a molten state, which is then flowed onto the base tape. A wet tape is formed by relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a three-stage drying chamber at 130° C., 80° C., and 40° C. The solidified film is removed from the reel together with the base tape or from the base tape for standby use.

[0037] Example 3

[0038] This embodiment provides a method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaics, comprising the following steps:

[0039] (1) Weigh 2.5 g of citric acid and dissolve it in 5 mL of deionized water by ultrasonic to obtain a citric acid aqueous solution. Use a pipette to measure 125 μL of ethylenediamine (the concentration of ethylenediamine is 0.5 mol / L) and dissolve it in the citric acid aqueous solution. Add ammonia water (3.2 mol / L) and stir evenly. Add 33.5 g of VAE emulsion (the viscosity of the VAE emulsion is 30%, and the diameter of the VAE emulsion is in the size range of 500 nm) and stir to form a uniform reaction precursor. Transfer the reaction precursor to a reactor, heat it in an oven at 160° C. for 3 hours, and then cool it. Add 0.6 g of dodecylethoxysulfobetaine and stir and disperse it at room temperature for 1 hour. The carbon quantum dots cover the surface of the VAE particles to form a C / VAE composite particle dispersion solution.

[0040] (2) using an ejector to atomize the C / VAE composite particle dispersion obtained in step (1) into droplets, mixing with a countercurrent gas at -70°C for instant contact, achieving rapid freezing of individual particles, forming a fluidized state under the action of the -20°C gas for primary drying, and the particles that meet the requirements enter the secondary stage to achieve vacuum airflow drying at room temperature to obtain a carbon quantum dot / VAE composite powder, wherein the carbon quantum dot content is 4.5wt%;

[0041] (3) The carbon quantum dot / VAE composite powder obtained in step (2) is mixed evenly with EVA or POE by a disperser, and then extruded and granulated by a twin-screw extruder (the segmented temperature control extrusion temperature of the twin-screw extruder is 85° C., 110° C., the main screw speed is 180 r / min, and the feeding screw speed is 6 r / min) to obtain a carbon quantum dot / VAE / EVA composite light-conversion masterbatch or a carbon quantum dot / VAE / POE composite light-conversion masterbatch, wherein the carbon quantum dot content is 0.4wt%;

[0042] (4) The composite light-converting masterbatch obtained in step (3) is heated to 240° C. in a material tank to form a molten state, which is then flowed onto the base tape. A wet tape is formed by relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a three-stage drying chamber at 130° C., 80° C., and 40° C. The solidified film is removed from the reel together with the base tape or from the base tape for standby use.

[0043] Example 4

[0044] This embodiment is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0045] In this embodiment, the concentration of ethylenediamine in step (1) is 0.8 mol / L.

[0046] The carbon quantum dot content in the carbon quantum dot / VAE composite powder obtained in this embodiment is 4wt%; the carbon quantum dot content in the carbon quantum dot / VAE / EVA composite light conversion masterbatch or the carbon quantum dot / VAE / POE composite light conversion masterbatch is 0.4wt%.

[0047] Comparative Example 1

[0048] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0049] In this comparative example, the concentration of ethylenediamine in step (1) is 1.0 mol / L.

[0050] The carbon quantum dot content in the carbon quantum dot / VAE composite powder obtained in this comparative example is 2wt%; the carbon quantum dot content in the carbon quantum dot / VAE / EVA composite light conversion masterbatch or the carbon quantum dot / VAE / POE composite light conversion masterbatch is 0.25wt%.

[0051] Comparative Example 2

[0052] This comparative example is carried out on the basis of the above-mentioned embodiment 1, and the similarities with the above-mentioned embodiment are not repeated here.

[0053] In this comparative example, the concentration of aqueous ammonia in step (1) is 4.0 mol / L.

[0054] The carbon quantum dot content in the carbon quantum dot / VAE composite powder obtained in this comparative example is 2.5wt%; the carbon quantum dot content in the carbon quantum dot / VAE / EVA composite light-conversion masterbatch or the carbon quantum dot / VAE / POE composite light-conversion masterbatch is 0.28wt%.

[0055] Comparative Example 3

[0056] This comparative example is a commercially available product in the prior art.

[0057] The products of the above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] It can be seen from Table 1 that the photovoltaic carbon quantum dot-based light conversion film of the embodiment of the present invention has the advantages of high down-conversion, high transparency and high stability.

[0061] In summary, the highly dispersed carbon quantum dot-based light conversion film for photovoltaics and the preparation method thereof provided by the present invention adopt a new process to prepare a carbon quantum dot-based light conversion film for photovoltaics with high conversion, high transparency, high stability and low cost, which can be applicable to common crystalline silicon cells on the market, such as single crystal silicon cells, polycrystalline silicon cells, heterojunction cells, etc.

[0062] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use, characterized in that: The following steps are involved: (1) Weighing citric acid and dissolving it in deionized water by ultrasonic to obtain a citric acid aqueous solution, measuring ethylenediamine and dissolving it in the citric acid aqueous solution, adding ammonia water and stirring evenly, adding VAE emulsion, stirring to form a uniform reaction precursor, transferring the reaction precursor to a reaction kettle, heating it in an oven and then cooling it, adding dodecylethoxysulfobetaine, stirring and dispersing it at room temperature, and coating the surface of VAE particles with carbon quantum dots to form a C / VAE composite particle dispersion solution; (2) using an ejector to atomize the C / VAE composite particle dispersion solution obtained in step (1) into droplets, mixing with a countercurrent gas at -70°C for instant contact, achieving rapid freezing of individual particles, forming a fluidized state under the action of the -20°C gas for primary drying, and the particles that meet the requirements enter the secondary stage to achieve vacuum airflow drying at room temperature to obtain carbon quantum dot / VAE composite powder; (3) the carbon quantum dot / VAE composite powder obtained in step (2) is mixed evenly with EVA or POE by a disperser, and then extruded and granulated by a twin-screw extruder to obtain a carbon quantum dot / VAE / EVA composite light-conversion masterbatch or a carbon quantum dot / VAE / POE composite light-conversion masterbatch; (4) The composite light-converting masterbatch obtained in step (3) is heated in a material tank to form a molten state, which flows onto the base tape, and forms a wet tape through the relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a drying chamber, and the solidified film is removed from the reel together with the base tape or from the base tape for standby use.

2. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, characterized in that: In step (1), the concentration of ethylenediamine is 0.2 mol / L to 0.8 mol / L; the concentration of aqueous ammonia is 0.8 mol / L to 3.2 mol / L; the viscosity of the VAE emulsion is in the range of 20% to 40%, and the diameter of the VAE emulsion is in the range of 300 nm to 1000 nm.

3. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, characterized in that: In step (1), the heating condition in the oven is heating at 160° C. to 180° C. for 3 h to 4 h; and dodecyl ethoxy sulfobetaine is added and stirred and dispersed at room temperature for 1 h to 2 h.

4. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, characterized in that: In step (2), the carbon quantum dot content in the obtained carbon quantum dot / VAE composite powder is 1wt% to 5wt%.

5. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, characterized in that: In step (3), the segmented temperature-controlled extrusion temperature of the twin-screw extruder is 80°C to 90°C, 100°C to 115°C, the main screw speed is 150 to 200 r / min, and the feeding screw speed is 5 to 8 r / min.

6. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, characterized in that: In step (3), the carbon quantum dot content in the composite light conversion masterbatch is 0.1wt% to 0.5wt%.

7. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, characterized in that: In step (4), the light conversion masterbatch is heated to 220°C to 240°C in a material tank; and is gradually solidified and cooled in a drying chamber at three stages of 110°C to 150°C, 70°C to 90°C, and 30°C to 50°C.

8. A highly dispersed carbon quantum dot-based light conversion film for photovoltaics, characterized in that: The photoconversion film is prepared by the method for preparing a highly dispersed carbon quantum dot-based photoconversion film for photovoltaic use as described in any one of claims 1 to 7.

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