Preparation of a carbon quantum dot grafted polymer material and its application in photovoltaic films

Abstract

The present invention discloses the preparation of a carbon quantum dot grafted polymer material and its application in photovoltaic adhesive films. By grafting a polymer material onto the surface of carbon quantum dots, the present invention more effectively disperses the carbon quantum dots evenly than other methods, improves quantum yield, and exhibits excellent and stable fluorescence properties, emitting bright blue light when excited by ultraviolet light. The material is added to photovoltaic adhesive films as a light conversion agent, absorbing ultraviolet light to protect solar cells and releasing visible light for absorption by solar cells, thereby improving their efficiency. The carbon quantum dot grafted polymer material of the present invention exhibits significant advantages in terms of light conversion efficiency, light stability, and processing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of light conversion materials, and particularly relates to the preparation of a carbon quantum dot grafted polymer material and its application in photovoltaic adhesive films. Background Art

[0002] Solar cells can utilize sunlight with wavelengths between 300nm and 1100nm. However, ultraviolet light (220-400nm) is harmful to solar cells, accelerating their aging and reducing their conversion efficiency. To improve the performance and lifespan of solar cell modules, photovoltaic films are used to encapsulate the cells. Photovoltaic resin is the most widely used film material for solar cells. However, because resin films block ultraviolet light, the ultraviolet rays in sunlight cannot be utilized by the cells, resulting in low photoelectric conversion efficiency. Therefore, by adding photoconversion materials to the films, they absorb ultraviolet light and convert it into visible light, thereby extending the lifespan of solar panels and compensating for the reduced photoelectric conversion efficiency caused by UV light blocking.

[0003] Carbon dots (CDs) generally refer to carbon or graphene quantum dots (CQDs or GQDs, respectively), carbon nanodots, or polymer dots. Due to their high luminescence efficiency, excellent stability, and optical stability, the design and synthesis of CDs have been extensively studied. In recent years, CDs have developed rapidly. Utilizing the properties of fluorescence, room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) have led to significant progress in many fields, including chemistry, physics, biology, and the environment. However, traditional CD preparation methods suffer from drawbacks such as low fluorescence quantum yield (QY), low visible light utilization, and short emission wavelength, which significantly limit their applications.

[0004] In order to improve the performance of carbon quantum dots and expand their scope of application, it is necessary to add other functional groups to them. Many methods, including chemical or physical adsorption of preformed polymers, have been used to functionalize these inorganic nanoparticles to improve their dispersibility and processability. Among these methods, surface grafting of nanoparticles is one of the most popular methods. In this method, the surface of the nanoparticles is usually modified with functional groups, and then these functional groups are connected to polymerization media, such as initiators, comonomers or chain transfer agents. Carbon quantum dots are modified by surface-initiated polymerization because there are many active groups on the surface of carbon quantum dots, such as carboxyl and hydroxyl groups, which can be modified by surface-initiated polymerization. The carbon quantum dot grafted polymer material of the present invention is added as a light conversion agent to a photovoltaic film as a light conversion material, which can absorb ultraviolet light to protect solar cells and release visible light for absorption by solar cells, thereby improving their efficiency. Summary of the Invention

[0005] Based on this, the present invention provides a method for preparing a carbon quantum dot-grafted polymer material and its application in photovoltaic adhesive films. The carbon quantum dot-grafted polymer material exhibits high quantum efficiency as a light-conversion material. Its application in photovoltaic adhesive films can improve the light-conversion efficiency of solar cells. The carbon quantum dots have the advantages of simple preparation and inexpensive raw materials.

[0006] The method for preparing the carbon quantum dot grafted polymer material of the present invention comprises the following steps:

[0007] Step 1: Preparation of carbon quantum dots

[0008] The carbon source and the surface passivating agent are added into the reactor, ultrasonically mixed, heated for reaction, and naturally cooled to room temperature. A solvent is added to the reaction product, the precipitate is collected by centrifugation, and the carbon quantum dot product is obtained after drying.

[0009] Step 2: Preparation of vinyl monomers

[0010] p-Hydroxycinnamic acid, ethylenediamine and N,N-dimethylformamide were used as raw materials and mixed uniformly in a flask for reaction. Acetic anhydride was then added dropwise, and the mixture was extracted with ethyl acetate. The mixture was washed and dried to prepare 4-acetoxystyrene.

[0011] Step 3: Preparation of carbon quantum dot grafted polymer materials

[0012] The carbon quantum dots, toluene and 4-acetoxystyrene obtained in step 1 are placed in a flask, and azobisisobutyronitrile is used as an initiator. The reaction is heated in an oil bath under a nitrogen atmosphere. The obtained mixture is diluted with tetrahydrofuran, and then the excess tetrahydrofuran is removed by rotary evaporation. A solvent is added to obtain a precipitate, which is filtered and dried to obtain a carbon quantum dot grafted polymer material.

[0013] The carbon source is an amino acid compound containing a carboxyl group or a hydroxyl group, and is selected from one of amino acid compounds such as 1,5-diaminonaphthalene, aspartic acid, arginine, glutamine, and lysine.

[0014] The surface passivator is an amine compound containing nitrogen, selected from diethylenetriamine, N-(3-(trimethoxysilyl)propyl)ethylenediamine, diethylenetriaminepentaacetic acid, ethylenediamine, branched polyethylenediamine, N,N-dimethyl-p-phenylenediamine and other amine compounds.

[0015] In step 1, the mass ratio of carbon source to surface passivator is 1:(0.5-1.5), ultrasonic treatment is performed for 5-10 minutes, and the reaction is performed at 150-250°C for 1-3 hours. Acetone is added to the resulting product, centrifuged at 12,000 rpm, and the precipitate is dried at 60-100°C for 6-8 hours.

[0016] In step 2, the addition ratio of p-hydroxycinnamic acid, ethylenediamine, and N,N-dimethylformamide is 1 g: (0.1-0.5) mL: (5-10) mL, and the mixture is heated at 150°C for 3 h. After cooling, 1-2 mL of acetic anhydride is added and the mixture is reacted for 1 h. The mixture is extracted with ethyl acetate, and the organic layer is washed 1-3 times with deionized water, filtered, and dried at 80-100°C for 6-8 h.

[0017] In step 3, the addition ratio of carbon quantum dots, toluene, 4-acetoxystyrene, and azobisisobutyronitrile is 0.1 g: (1-10) mL: (0.1-1) mL: (0.01-0.05) g, the reaction is carried out at 100-150 ° C for 3-6 hours, and the rotary evaporation is carried out at 70 ° C. The solvent added is methanol, and the carbon quantum dot grafted polymer material is obtained by drying at 70 ° C.

[0018] Application of the carbon quantum dot grafted polymer material of the present invention in the preparation of photovoltaic adhesive films.

[0019] Specifically, during the preparation process of the photovoltaic film, the carbon quantum dot grafted polymer material is added as a light conversion material to the photovoltaic film system, and then applied to photovoltaic devices or solar cells.

[0020] The specific steps are as follows:

[0021] The carbon quantum dot grafted polymer material and EVA or POE particles are mixed and re-granulated, and then heated, melted and mixed evenly through a twin-screw extruder, extruded into long strips, formed through cold water, and pelletized by a pelletizer. The obtained granular material is cast through a casting machine to prepare a film.

[0022] The added mass of the carbon quantum dot grafted polymer material is 0.01%-0.1% of the mass of the EVA or POE particles.

[0023] Compared with the prior art, the beneficial technical effects achieved by the present invention are as follows:

[0024] The raw materials used in the present method are inexpensive, readily available, non-toxic, and odorless. The carbon quantum dots produced have a high fluorescence quantum yield and good experimental reproducibility. The prepared carbon quantum dot-grafted polymer material exhibits good dispersion and agglomeration resistance, facilitating subsequent application in photovoltaic films.

[0025] 2. By grafting polymer materials onto the surface of carbon quantum dots, the carbon quantum dots are more effectively dispersed and evenly distributed than other methods, increasing quantum yield and exhibiting excellent and stable fluorescence properties. When excited by ultraviolet light, they can emit bright blue light. When added to photovoltaic films as a light conversion material, they absorb ultraviolet light to protect solar cells and release visible light for absorption by solar cells, thereby improving their efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 These are transmission electron micrographs of CD-1(a) and CD-2(b).

[0027] Figure 2 It is the infrared spectrum of CD-1 and CD-2.

[0028] Figure 3 This is the X-ray photoelectron spectrum of CD-2.

[0029] Figure 4 These are the ultraviolet spectrum and fluorescence spectrum of CD-2.

[0030] Figure 5 This is the fluorescence quantum efficiency diagram of CD-2. DETAILED DESCRIPTION

[0031] The technical solutions of the present invention are described clearly and completely below. It is obvious that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example 1:

[0032] 1. Preparation of Carbon Quantum Dots: 1.5 g of 1,5-diaminonaphthalene and 1.07 ml of diethylenetriamine were mixed and sonicated for 10 minutes. The mixture was then refluxed under condensation at 200°C in an oil bath for 1 hour and allowed to cool naturally to room temperature. 20 ml of acetone was added to the resulting product, and the mixture was centrifuged at 12,000 rpm for 10 minutes. The precipitate was collected and dried at 80°C for 6 hours to obtain product CD-1. The fluorescence quantum yield was 31.3%.

[0033] 2. Preparation of vinyl monomer: 1 g of p-hydroxycinnamic acid, 0.5 mL of ethylenediamine, and 6 mL of N,N-dimethylformamide were mixed in a flask and reacted uniformly at 150°C for 3 h. Then, 1 mL of acetic anhydride was added dropwise, and the mixture was extracted with ethyl acetate. The mixture was washed with deionized water three times, filtered, and dried at 80°C for 6 h to obtain 4-acetoxystyrene.

[0034] 3. Preparation of Carbon Quantum Dot Grafted Polymer Material: 0.1 g CD-1, 5 ml toluene, 0.5 ml 4-acetoxystyrene, and 0.02 g azobisisobutyronitrile were mixed and heated in an oil bath at 150°C under a nitrogen atmosphere for 3 h. Excess tetrahydrofuran solution was removed by rotary evaporation at 70°C. Methanol was added to obtain a precipitate, which was filtered and dried at 70°C to obtain product CD-2. The fluorescence quantum yield was 35.8%.

[0035] Depend on Figure 1 (a) It can be seen that the size of a single carbon quantum dot CD-1 is about 3-5 nm. Figure 1(b) It can be seen that due to the shielding effect of the grafted polymer chain, the diameter of CD-2 is about 5-10 nm compared with CD-1, which is larger in size and more uniformly dispersed.

[0036] Figure 2 It can be seen that CD-2 has a higher peak at 1700 cm-1 than CD-1. -1 、1450 cm -1 and 700cm -1 There are bands at these locations, which correspond to the benzene ring of 4-acetoxystyrene. Figure 1 , indicating that carbon quantum dot grafted polymer materials have been successfully synthesized.

[0037] Figure 3 X-ray photoelectron spectroscopy analysis of carbon quantum dot grafted polymer materials showed that peaks of C, N and O elements were observed, with a content ratio of C:N:O=63.67:5.9:30.43.

[0038] according to Figure 4 and Figure 5 CD-2 exhibits excellent absorption within the 200-400nm wavelength range. When excited by ultraviolet light, the material exhibits strong fluorescence beyond the 400-600nm wavelength range. CD-2 can be excited and fluoresce both in solution and as a solid film, demonstrating excellent processability and dispersibility, allowing for easy fabrication into fluorescent plastic films and fibers. The photoconversion material exhibits a high quantum efficiency, reaching 35.8% at the optimal excitation wavelength of 360nm. Example 2:

[0039] 1. Preparation of Carbon Quantum Dots: 1.5 g of aspartic acid and 1.07 mL of diethylenetriamine were mixed and sonicated for 10 minutes. The mixture was then refluxed under condensation at 200°C in an oil bath for 1 hour and allowed to cool naturally to room temperature. 20 mL of acetone was added to the resulting product, and the mixture was centrifuged at 12,000 rpm for 10 minutes. The precipitate was collected and dried at 80°C for 6 hours to obtain the product. The fluorescence quantum yield was 25.3%.

[0040] Steps 2 and 3 refer to Example 1. The fluorescence quantum yield was 28.12%. Example 3:

[0041] Steps 1 and 2 are the same as those in Example 1.

[0042] 3. Preparation of Carbon Quantum Dot Grafted Polymer Material: 0.1 g CD-1, 5 ml toluene, 0.1 ml 4-acetoxystyrene, and 0.02 g azobisisobutyronitrile were mixed and heated in an oil bath at 150°C under a nitrogen atmosphere for 3 h. Excess tetrahydrofuran solution was removed by rotary evaporation at 70°C. Methanol was added to obtain a precipitate, which was filtered and dried at 70°C to obtain the product. The fluorescence quantum yield was 32.75%. Example 4:

[0043] Steps 1 and 2 are the same as those in Example 1.

[0044] Preparation of carbon quantum dot-grafted polymer: 0.1 g CD-1, 5 ml toluene, 1 ml 4-acetoxystyrene, and 0.02 g azobisisobutyronitrile were mixed and heated in an oil bath at 150°C under a nitrogen atmosphere for 3 h. Excess tetrahydrofuran was removed by rotary evaporation at 70°C, and methanol was added to obtain a precipitate. The precipitate was filtered and dried at 70°C to obtain the product. The fluorescence quantum yield was 30.8%. Example 5:

[0045] Steps 1 and 2 are the same as those in Example 1.

[0046] 3. Preparation of Carbon Quantum Dot Grafted Polymer Material: 0.1 g CD-1, 5 ml toluene, 0.5 ml 4-acetoxystyrene, and 0.01 g azobisisobutyronitrile were mixed and heated in an oil bath at 150°C under a nitrogen atmosphere for 3 h. Excess tetrahydrofuran solution was removed by rotary evaporation at 70°C. Methanol was added to obtain a precipitate, which was filtered and dried at 70°C to obtain the product. The fluorescence quantum yield was 32.15%. Example 6:

[0047] Steps 1 and 2 are the same as those in Example 1.

[0048] 3. Preparation of Carbon Quantum Dot Grafted Polymer Material: 0.1 g CD-1, 5 ml toluene, 0.5 ml 4-acetoxystyrene, and 0.05 g azobisisobutyronitrile were mixed and heated in an oil bath at 150°C under a nitrogen atmosphere for 3 h. Excess tetrahydrofuran solution was removed by rotary evaporation at 70°C. Methanol was added to obtain a precipitate, which was filtered and dried at 70°C to obtain the product. The fluorescence quantum yield was 33.68%.

[0049]

[0050] Application Example: Preparation Method of Photovoltaic Adhesive Film Containing Carbon Quantum Dot Grafted Polymer Material

[0051] The synthesized carbon quantum dot grafted polymer material and EVA particles are mixed, wherein the mass ratio of the light conversion material is 0.05%, and then added into a twin-screw extruder. The mixture is melted and mixed evenly by heating, extruded into long strips, and formed into pellets by a pelletizer after water cooling in a cold water tank. The mixed material is passed through a casting machine to obtain a film.

[0052] Test method: Module power was tested according to the method specified in IEC61215. Specific test data is shown in the table below.

[0053]

[0054] In summary, when preparing the carbon dot grafted polymer material in Example 1, the appropriate ratio of 4-acetoxystyrene and initiator results in a high quantum yield and good dispersibility, which can be applied to photovoltaic films as a photoconversion material and, to a certain extent, can improve the photoconversion efficiency of solar cells. Changing the carbon source for preparing carbon dots in Example 2, changing the ratio of 4-acetoxystyrene in Examples 3 and 4, and changing the ratio of initiators in Examples 5 and 6 all affect the quantum yield of the photoconversion material and result in lower dispersibility and photoconversion efficiency when applied to photovoltaic films. The photoconversion material of the present invention can absorb ultraviolet light to protect solar cells while emitting light with a wavelength of 400-600nm for use by solar cells, thereby improving the photoconversion efficiency of solar cells.

Claims

1. A method for preparing a carbon quantum dot grafted polymer material, characterized in that The steps include: Step 1: Preparation of carbon quantum dots The carbon source and the surface passivating agent are added to the reactor, ultrasonically mixed, heated for reaction, and naturally cooled to room temperature. A solvent is added to the reaction product, and the precipitate is collected by centrifugation and dried to obtain a carbon quantum dot product. Step 2: Preparation of vinyl monomers p-Hydroxycinnamic acid, ethylenediamine and N,N-dimethylformamide were mixed and reacted in a flask as raw materials, and then acetic anhydride was added dropwise, extracted with ethyl acetate, washed and dried to prepare 4-acetoxystyrene; Step 3: Preparation of carbon quantum dot grafted polymer materials The carbon quantum dots obtained in step 1, toluene and 4-acetoxystyrene are placed in a flask, azobisisobutyronitrile is used as an initiator, and the mixture is heated to react under a nitrogen atmosphere. The obtained mixture is diluted with tetrahydrofuran, and the excess tetrahydrofuran is removed by rotary evaporation. A solvent is added to obtain a precipitate, which is filtered and dried to obtain a carbon quantum dot grafted polymer material; The carbon source is selected from one of 1,5-diaminonaphthalene, aspartic acid, arginine, glutamine, and lysine; In step 2, the addition ratio of p-hydroxycinnamic acid, ethylenediamine, and N,N-dimethylformamide is 1 g: (0.1-0.5) mL: (5-10) mL.

2. The preparation method according to claim 1, wherein: The surface passivator is an amine compound containing nitrogen, selected from diethylenetriamine, N-(3-(trimethoxysilyl)propyl)ethylenediamine, diethylenetriaminepentaacetic acid, ethylenediamine, branched polyethylenediamine, and N,N-dimethyl-p-phenylenediamine.

3. The preparation method according to claim 1, wherein: In step 1, the reaction temperature is 150-250° C., and the reaction time is 1-3 h.

4. The preparation method according to claim 1, wherein: In step 2, p-hydroxycinnamic acid, ethylenediamine and N,N-dimethylformamide are mixed as raw materials in a flask, reacted at 150° C. for 3 h, and then acetic anhydride is added dropwise to continue the reaction for 1 h.

5. The preparation method according to claim 1, wherein: In step 3, the addition ratio of carbon quantum dots, toluene, 4-acetoxystyrene, and azobisisobutyronitrile is 0.1 g: (1-10) mL: (0.1-1) mL: (0.01-0.05) g.

6. The preparation method according to claim 1, wherein: In step 3, the reaction temperature is 100-150° C., and the reaction time is 3-6 h.

7. Use of the carbon quantum dot grafted polymer material prepared by the preparation method according to any one of claims 1 to 6 as a light conversion material in the preparation of photovoltaic films.

8. The use of claim 7 in preparing a photovoltaic film, characterized in that: The carbon quantum dot grafted polymer material and EVA or POE particles are mixed and re-granulated, heated and melted by a twin-screw extruder to mix uniformly, extruded and shaped, pelletized by a pelletizer, and the obtained granular material is cast by a casting machine to prepare a film.

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