A high-dispersed carbon quantum dot-based down-conversion film for photovoltaics and a preparation method thereof

Abstract

The application discloses a kind of high-dispersed carbon quantum dots-based light conversion film for photovoltaic and preparation method thereof, comprising: dissolving ethylenediamine in citric acid aqueous solution, adding ammonia water and stirring uniformly, adding VAE emulsion and stirring after reaction, adding dodecyl ethoxy sulfobetaine and stirring dispersion, forming C / VAE composite particle dispersion solution atomized into mist drop, vacuum air flow drying, the carbon quantum dots / VAE composite powder obtained is stirred and mixed uniformly with EVA or POE, extruding granulation through extruder to obtain carbon quantum dots / VAE / EVA or carbon quantum dots / VAE / POE composite light conversion master batch, heating in tank to form molten state flow to the upper part of base band to form wet band, gradually solidifying and cooling in drying chamber, and the solidified film is separated from the base band together or from the base band on reel for use.The application uses a new process to prepare high down-conversion, high transparency, high stability, low-cost carbon quantum dots-based light conversion film for photovoltaic, which is suitable for commonly used crystalline silicon cells on the market, such as single-crystal silicon cell, polycrystalline silicon cell, heterojunction cell, etc.

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] Currently, over 85% of photovoltaic modules produced worldwide annually are crystalline silicon modules. Crystalline silicon modules dominate the market due to their long lifespan, abundant availability, and non-toxicity. The efficiency of silicon-based solar cells generally ranges from 15% to 20%, still some distance from the theoretical efficiency limit of 31% for a single-cell Shockley-Queisser solar cell. This is because crystalline silicon solar cells currently primarily absorb light in the wavelength range of 400 to 1100 nm, and their quantum efficiency for light below 400 nm (i.e., violet and ultraviolet light) is very low. Furthermore, single-crystalline silicon exhibits a better response to longer wavelengths. Therefore, by rationally utilizing sunlight energy below 400 nm and converting it into longer-wavelength light above 400 nm, the photoelectric conversion efficiency of solar cells can be significantly improved. Furthermore, incorporating down-conversion luminescent materials into solar encapsulation films can reduce the film's aging rate in outdoor environments, thereby extending the lifespan of solar modules. Furthermore, new-generation photovoltaic cells (such as heterojunctions) are highly sensitive to ultraviolet light, which damages the cells and shortens 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 behind photovoltaic photoconverter composite films lies in the synthesis and preparation of high-performance photoconverters and their uniform dispersion and compounding within the film. Currently reported photoconverters include metal oxide quantum dots, rare earth oxides, rare earth organic complexes, organic compounds, and carbon quantum dots. Metal oxide quantum dots and rare earth oxide photoconverters offer stable structures and low cost, but suffer from a narrow UV absorption range and low quantum efficiency. Rare earth organic complexes and organic compounds offer a wide UV absorption range and high quantum efficiency, but suffer from low structural stability and high cost. Carbon quantum dots, on the other hand, offer not only excellent structural stability but also tunable cost, UV absorption, and quantum efficiency, making them the most promising photoconverters for photovoltaic applications.

[0004] At present, there have been many reports on the synthesis of carbon quantum dots, and related studies or literature have reported 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 resin matrix dispersion, 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 high-conversion, highly transparent, highly stable, 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 ultrasonication 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 obtain a uniform reaction precursor, transferring the reaction precursor to a reactor, heating it in an oven and then cooling it, adding dodecylethoxysulfobetaine, stirring and dispersing it at room temperature, and coating the surface of the 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 obtained in step (1) into droplets, mixing them with a countercurrent of -70°C gas for instant contact to achieve rapid freezing of individual particles, forming a fluidized state under the action of -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) mixing the carbon quantum dots / VAE composite powder obtained in step (2) with EVA or POE by stirring with a disperser, and then extruding and granulating by a twin-screw extruder to obtain carbon quantum dots / VAE / EVA composite light-conversion masterbatch or carbon quantum dots / VAE / POE composite light-conversion masterbatch;

[0012] (4) heating the composite light-conversion masterbatch obtained in step (3) in a trough to form a molten state, flowing onto a base tape, forming a wet tape by relative movement of a doctor blade and the base tape, gradually solidifying and cooling in a drying chamber, and the solidified film being separated from the base tape and wound on a reel.

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

[0014] Preferably, in step (1), the heating in the oven is at 160-180℃ for 3-4 h; and the addition of dodecyl ethyloxy sulfobetaine is stirred and dispersed at room temperature for 1-2 h.

[0015] Further preferably, in step (1), the heating in the oven is at 160-165℃ for 3 h; and the addition of dodecyl ethyloxy sulfobetaine is stirred and dispersed at room temperature for 1 h.

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

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

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

[0019] Preferably, in step (4), the light-conversion masterbatch is heated to 220-240℃ in the trough; and the drying chamber is gradually solidified and cooled at 110-150℃, 70-90℃ and 30-50℃.

[0020] The application also claims to protect a high-dispersion carbon quantum dot-based down light conversion film for photovoltaics, which is prepared by the above method.

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

[0022] The high-dispersion carbon quantum dot-based down light conversion film for photovoltaics and the preparation method thereof provided by the application adopt a new process to prepare a carbon quantum dot-based light conversion film for photovoltaics with high down-conversion, high transparency, high stability and low cost, which can be applied to common crystalline silicon cells on the market, such as monocrystalline silicon cells, polycrystalline silicon cells and heterojunction cells. DETAILED DESCRIPTION

[0023] In order to have a clearer understanding of the technical features, objectives and effects of the application, the specific implementation will be described in detail.

[0024] The application will be further described below in combination with examples, but the application is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to different requirements of specific use, and the implementation conditions mentioned are the conventional conditions in the industry. The technical features involved in each embodiment of the application can be combined with each other as long as there is no conflict.

[0025] Example 1

[0026] The embodiment provides a preparation method of a high-dispersion carbon quantum dot-based down light conversion film for photovoltaics, which comprises the following steps:

[0027] (1) 2.5 g of citric acid is weighed and ultrasonically dissolved in 5 mL of deionized water to obtain a citric acid aqueous solution, 125 microliters of ethylenediamine (the concentration of ethylenediamine is 0.5 mol / L) is taken by a pipette gun and dissolved in the citric acid aqueous solution, ammonia water (0.8 mol / L) is added and stirred uniformly, 33.5 g of VAE emulsion (the viscosity of the VAE emulsion is 30%, and the diameter of the VAE emulsion is 500 nm in size range) is added, and the reaction precursor is stirred uniformly, the reaction precursor is transferred to a reaction kettle, and after being heated at 160 DEG C in an oven for 3 hours, it is cooled, 0.6 g of dodecyl ethyloxy sulfobetaine is added, and stirred and dispersed at room temperature for 1 h, 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 obtained in step (1) into droplets, mixing and contacting the droplets with a countercurrent of -70°C gas instantaneously to achieve rapid freezing of the individual particles, forming a fluidized state under the action of -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 uniformly mixed 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 0.5 wt%;

[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 flows onto the base tape. A wet tape is formed by the relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a drying chamber at three stages of 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 use.

[0031] Example 2

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

[0033] (1) Weigh 2.5 g of citric acid and dissolve it in 5 mL of deionized water by ultrasonication 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. Carbon quantum dots coat 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 obtained in step (1) into droplets, mixing and contacting the droplets with a countercurrent of -70°C gas instantaneously to achieve rapid freezing of the individual particles, forming a fluidized state under the action of -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 wt%;

[0035] (3) The carbon quantum dot / VAE composite powder obtained in step (2) is uniformly mixed 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 0.45 wt%;

[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 flows onto the base tape. A wet tape is formed by the relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a drying chamber at three stages of 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 use.

[0037] Example 3

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

[0039] (1) Weigh 2.5 g of citric acid and dissolve it in 5 mL of deionized water by ultrasonication 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. Carbon quantum dots coat 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 and contacting the droplets with a countercurrent of -70°C gas instantaneously to achieve rapid freezing of the individual particles, forming a fluidized state under the action of -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 uniformly mixed 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 0.4 wt%;

[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 flows onto the base tape. A wet tape is formed by the relative movement of a scraper and the base tape. The wet tape is gradually solidified and cooled in a drying chamber at three stages of 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 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 4 wt %; 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 0.4 wt %.

[0047] Comparative Example 1

[0048] This comparative example is carried out on the basis of the above-mentioned Example 1, and the similarities with the above-mentioned Example 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 2 wt %; 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 0.25 wt %.

[0051] Comparative Example 2

[0052] The present comparative example was carried out on the basis of the above-mentioned Example 1, and the same parts as the above-mentioned example were not described.

[0053] In the present comparative example, the concentration of ammonia water in step (1) was 4.0 mol / L.

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

[0055] Comparative Example 3

[0056] The present comparative example was a commercially available product in the prior art.

[0057] The products of the above-mentioned examples and comparative examples were detected, and the detection results are shown in Table 1.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, the carbon quantum dot-based light-conversion film for photovoltaics of the present example has the advantages of high down-conversion, high transparency, and high stability.

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

[0062] The above-mentioned examples only express several embodiments of the present application, and the description is relatively specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the scope of protection of the present patent should be subject to the appended 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) Weigh citric acid and dissolve it in deionized water by ultrasonication to obtain a citric acid aqueous solution; weigh ethylenediamine and dissolve it in the citric acid aqueous solution; add ammonia water and stir evenly; add VAE emulsion and stir to obtain a uniform reaction precursor; transfer the reaction precursor to a reactor, heat it in an oven and then cool it; add dodecylethoxysulfobetaine and stir and disperse it at room temperature; carbon quantum dots coat the surface of VAE particles to form a C / VAE composite particle dispersion solution; (2) Atomizing the C / VAE composite particle dispersion obtained in step (1) into droplets by using an ejector, mixing and instantaneously contacting with a countercurrent gas at -70°C to achieve rapid freezing of individual particles, forming a fluidized state under the action of a -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 uniformly mixed 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 trough to form a molten state, which flows onto the base tape, and forms a wet tape through the relative movement of the 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 use.

2. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, wherein: In step (1), the concentration of ethylenediamine is 0.2 mol / L to 0.8 mol / L; the concentration of ammonia water 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, wherein: In step (1), the heating condition in the oven is heating at 160° C. to 180° C. for 3 h to 4 h; and dodecylethoxysulfobetaine 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, wherein: In step (2), the carbon quantum dot content in the obtained carbon quantum dot / VAE composite powder is 1 wt% to 5 wt%.

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

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

7. The method for preparing a highly dispersed carbon quantum dot-based light conversion film for photovoltaic use according to claim 1, wherein: In step (4), the light-converting masterbatch is heated to 220°C~240°C in a trough; and gradually solidified and cooled in a drying room through three stages of 110~150°C, 70~90°C, and 30~50°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 according to any one of claims 1 to 7.

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