Blue, green, red three primary color fluorescent carbon dots with high fluorescence quantum yield and application thereof

Abstract

The present application relates to a kind of blue, green, red three primary color fluorescent carbon dots based on high fluorescence quantum yield, it is with phytic acid and o-phenylenediamine as raw material, by regulating the ratio of phytic acid and o-phenylenediamine, using solvothermal method to obtain the three primary color fluorescent carbon dots with different luminescence colors.The carbon dots of the present application show very strong fluorescence characteristics in solution, and the blue, green and red fluorescence quantum yields can reach 19.2%, 68.68% and 60.28% respectively.The three primary color fluorescent carbon dot films prepared by blending them with polymers can be used in light emitting diodes and fluorescent solar concentrators.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent carbon nanomaterials technology, and relates to a blue, green and red fluorescent carbon dot with high fluorescence quantum yield, its preparation method and application. Background Technology

[0002] Carbon dots are a new type of zero-dimensional fluorescent carbon nanomaterial. Based on the properties of carbon materials and the abundance of functional groups on their surface, they have advantages such as excellent optical properties, tunable emission color, low toxicity, and good photostability. They are mainly used in cell imaging, anti-counterfeiting, ion detection, optical devices and other fields.

[0003] Currently, the main method for preparing carbon dots is a bottom-up approach, using small molecules as raw materials and employing a solvothermal method to carbonize them under high temperature and high pressure. However, this method can only produce fluorescent carbon dots of a single color under most conditions, and the quantum yield is relatively low.

[0004] In recent years, Xiong Huanming's research group has used column chromatography to purify and separate carbon dots synthesized from o-phenylenediamine and urea (Ding H, Yu SB, Wei JS, et al. Full-Color Light-Emitting Carbon Dots with a Surface-State-Controlled Luminescence Mechanism[J]. ACS Nano (2016, 10: 484-491.), obtained full-spectrum luminescent carbon dots with a quantum yield of up to 24%; furthermore, their research group also used o-phenylenediamine and L-glutamic acid as raw materials (Ding H, Wei J, Zhang P, et al. Solvent-Controlled Synthesis of Highly Luminescent Carbon Dots with a Wide Color Gamut and Narrowed Emission Peak Widths[J]. Small (2018, 14: 1800612.), by controlling the solvent, full-spectrum emission from blue to near-infrared was achieved, with a quantum yield of up to 54%.

[0005] Wang L, Li W, Yin L, et al. Full-color fluorescent carbon quantum dots[J]. Science Advances(2020, 6: eabb6772.) Using o-phenylenediamine and weak acid as raw materials, by changing the type of weak acid and the ratio of weak acid to o-phenylenediamine, a full-spectrum luminescent carbon dot with a quantum yield of up to 72% was synthesized.

[0006] However, the luminescence of most carbon dots is controlled by their surface or core states, which places high demands on the selection of raw materials, solvents, and temperature control in carbon dot synthesis. The ability to prepare multicolor luminescent carbon dots with high fluorescence quantum yield by simply adjusting the proportions of raw materials is of great value for improving the optical properties of carbon dots and promoting their industrial application in optical devices.

[0007] Furthermore, current fluorescent solar concentrators not only exhibit low absorption efficiency and high reabsorption, but the commonly used quantum dot materials such as CdSe, CdS, and PbS are also prone to degradation, raising environmental and health concerns due to their toxicity. In contrast, carbon dots possess numerous advantages, including high stability, high absorption efficiency, and a large Stokes shift, making their application in fluorescent solar concentrators a promising prospect. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing blue, green, and red fluorescent carbon dots with high fluorescence quantum yield and their preparation method, for application in light-emitting diodes and fluorescent solar concentrators.

[0009] The blue, green, and red fluorescent carbon dots based on high fluorescence quantum yield described in this invention are prepared by dispersing phytic acid and o-phenylenediamine in a solvent and carrying out a solvothermal reaction, and by controlling the ratio of raw materials to obtain blue, green, and red carbon dots with high fluorescence quantum yield.

[0010] Specifically, blue carbon dots can be prepared when the mass ratio of phytic acid to o-phenylenediamine is (8-20):1; green carbon dots can be prepared when the mass ratio of phytic acid to o-phenylenediamine is (2-5):1; and red carbon dots can be prepared when the mass ratio of phytic acid to o-phenylenediamine is (0.1-1):1.

[0011] More specifically, the solvent is at least one selected from water, ethanol, methanol, N,N-dimethylformamide, dimethyl sulfoxide, and dichloromethane.

[0012] The present invention also provides a specific method for preparing the three primary color fluorescent carbon dots, which involves dispersing phytic acid and o-phenylenediamine in different mass ratios in a solvent, placing them in a closed high-pressure reactor, heating to 180-250°C for a solvothermal reaction, filtering out the reaction product, and drying it to obtain blue, green, and red primary color carbon dots with high fluorescence quantum yield.

[0013] Furthermore, the solvothermal reaction time is preferably 10 to 34 hours.

[0014] This invention selects phytic acid and o-phenylenediamine in different mass ratios as raw materials and prepares blue, green and red fluorescent carbon dots with quantum yields of 19.2%, 68.68% and 60.29% respectively by a one-step solvothermal method. Among them, the blue carbon dots exhibit excitation-dependent characteristics in solution, while the green and red carbon dots exhibit excitation-independent characteristics in solution.

[0015] The present invention further provides the application of the blue, green, and red primary color fluorescent carbon dots in the fabrication of light-emitting diode devices.

[0016] Specifically, a solid-state luminescent three-primary-color carbon dot / polymer film is prepared by mixing the blue, green, and red primary-color fluorescent carbon dots with a polymer solution. This film is then used as a fluorescent material and assembled with chips of different excitation wavelengths to prepare a multicolor light-emitting diode.

[0017] More specifically, the polymer solution is a solution obtained by dissolving at least one of polyvinylpyrrolidone, polyvinyl alcohol, polymethyl methacrylate or polysiloxane in its soluble organic solvent.

[0018] Among the chips with different excitation wavelengths, the excitation wavelength can be any one of 360nm, 380nm, 400nm, 420nm, 440nm, and 460nm.

[0019] Based on the excitation-dependent characteristics of blue carbon dots, the emission color of blue carbon dots varies when chips with different excitation wavelengths are used. For example, when using a chip with an excitation wavelength of 360nm, the emission corresponds to 430nm; correspondingly, chips with excitation wavelengths of 380nm, 400nm, 420nm, 440nm, and 460nm correspond to emission at 450nm, 465nm, 490nm, 520nm, and 540nm, respectively.

[0020] Furthermore, due to the significant excitation-dependent characteristics of the blue carbon dots, it is possible to fabricate white LED devices using them. This invention, by controlling the proportion of blue carbon dots in the solid-state luminescent three-primary-color carbon dot / polymer film, enables its emission spectrum to cover the entire visible light region. This allows for the fabrication not only of pure-color blue LED devices but also of cool white LEDs, standard white LEDs, and warm white LEDs.

[0021] Based on the independent excitation characteristics of green and red carbon dots, the emitted color is the same when using chips with different excitation wavelengths. Specifically, the green carbon dots emit 500nm green light, and the red carbon dots emit 600nm red light. Therefore, this invention preferably uses a conventional 360nm ultraviolet chip to fabricate green and red LED devices.

[0022] Furthermore, the present invention also provides the application of the blue, green, and red primary color fluorescent carbon dots in the preparation of multicolor fluorescent solar concentrators.

[0023] Specifically, a fluorescent solar concentrator is prepared by mixing the blue, green, and red primary color fluorescent carbon dots with a polymer solution to obtain a mixed solution, coating it on a glass surface, and coupling it with a solar cell.

[0024] More specifically, the polymer solution is a solution obtained by dissolving at least one of polyvinylpyrrolidone, polyvinyl alcohol, polymethyl methacrylate or polysiloxane in its soluble organic solvent.

[0025] The fluorescent solar concentrator prepared by this invention has a solar absorption efficiency of up to 23.3%, and its large Stokes shift can also reduce the reabsorption efficiency of the fluorescent solar concentrator. Finally, the photoelectric conversion efficiency of the single-sided coupled silicon-based solar cell prepared by the fluorescent solar concentrator can reach 0.3%.

[0026] However, due to the significant excitation-dependent characteristics of blue carbon dots, a large amount of reabsorption occurs, resulting in very low photoelectric conversion efficiency of fluorescent solar concentrators made from blue carbon dots. Attached Figure Description

[0027] Figure 1 This is a transmission electron microscope image of the blue carbon dots prepared in Example 1.

[0028] Figure 2 This is the fluorescence spectrum of the blue carbon dots in Example 1.

[0029] Figure 3 This is the emission spectrum of the cold white LED device prepared in Example 2.

[0030] Figure 4 This is the color coordinate diagram of the cool white LED device in Example 2.

[0031] Figure 5 This is the emission spectrum of the standard white LED device prepared in Example 3.

[0032] Figure 6 This is the color coordinate diagram of the standard white LED device in Example 3.

[0033] Figure 7 This is the emission spectrum of the warm white LED device prepared in Example 4.

[0034] Figure 8 This is the color coordinate diagram of the warm white LED device in Example 4.

[0035] Figure 9This is the emission spectrum of the blue LED device prepared in Example 5.

[0036] Figure 10 This is the absorption efficiency spectrum of the blue solar concentrator prepared in Example 6.

[0037] Figure 11 This is a transmission electron microscope image of the green carbon dots prepared in Example 7.

[0038] Figure 12 This is the fluorescence spectrum of the green carbon dots in Example 7.

[0039] Figure 13 This is the emission spectrum of the green LED device prepared in Example 8.

[0040] Figure 14 This is the absorption efficiency spectrum of the green solar concentrator prepared in Example 9.

[0041] Figure 15 This is a transmission electron microscope image of the red carbon dots prepared in Example 10.

[0042] Figure 16 This is the fluorescence spectrum of the red carbon dots in Example 11.

[0043] Figure 17 This is the emission spectrum of the red LED device prepared in Example 12.

[0044] Figure 18 This is the absorption efficiency spectrum of the red solar concentrator prepared in Example 13. Implementation

[0045] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, so that those skilled in the art can better understand and utilize the present invention, and are not intended to limit the scope of protection of the present invention.

[0046] Unless otherwise specified, the production processes, experimental methods, or testing methods involved in the embodiments and comparative examples of this invention are all conventional methods in the prior art, and their names and / or abbreviations are all conventional names in the art, which are very clear and distinct in the relevant application fields. Those skilled in the art can understand the conventional process steps based on the names and apply the corresponding equipment, and implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0047] The various instruments, equipment, raw materials or reagents used in the embodiments of this invention are not subject to any special restrictions on their source. They are all conventional products that can be purchased through regular commercial channels and can be prepared according to conventional methods known to those skilled in the art. Example

[0048] Example 1

[0049] Weigh 2500 mg of phytic acid and 180 mg of o-phenylenediamine, add them to 20 mL of ethanol, place them in a polytetrafluoroethylene-lined stainless steel autoclave, and solvothermal treat them at 230 °C for 22 h. After the reaction is complete, allow them to cool naturally to room temperature in air to obtain the crude product of carbon dot solution.

[0050] The crude carbon dot solution was filtered using a 0.22 μm syringe filter. The filtrate was then rotary evaporated and vacuum dried to obtain solid blue carbon dots.

[0051] The blue carbon dots prepared above were dissolved in DMSO solution to obtain a blue carbon dot solution, and its physical properties and luminescence performance were characterized.

[0052] from Figure 1 The transmission electron microscopy (TEM) images show that the blue carbon dots are spherical in shape, without obvious aggregation, and have a narrow particle size distribution range with an average particle size of 5.79 nm.

[0053] Figure 2 The fluorescence spectrum of the blue carbon dot solution is shown. When the carbon dot solution is excited with different excitation wavelengths, the emission peak position of the carbon dot solution is different, indicating that the blue carbon dot solution has an excitation-dependent characteristic. Its optimal excitation wavelength is located at 360 nm, and the optimal emission wavelength under 360 nm excitation light is 430 nm.

[0054] By detecting the number of photons emitted by the carbon dot solution and the number of photons absorbed by the 360nm excitation light, the quantum yield of the blue carbon dots was calculated to be 19.2%.

[0055] Example 2

[0056] Weigh 5 mg of the blue carbon dots prepared in Example 1, dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution, and stir at 500 r / min for 5 min to obtain a mixed solution of blue carbon dots / polyvinylpyrrolidone complex.

[0057] Take 30 μL of the mixed solution and drop it onto the LED lamp cap. Dry it and then repeat the dropping process until a total of 90 μL is added. After complete drying, a blue carbon dot / polyvinylpyrrolidone composite fluorescent film is obtained.

[0058] A lamp cap with the fluorescent film is placed on an LED chip with an excitation wavelength of 360nm to assemble a cool white LED device.

[0059] Figure 3 The emission spectrum of the above-mentioned cold white LED device is given. When excited by a 360nm excitation chip, its emission spectrum covers most of the visible light region.

[0060] The CIE coordinates of the device can be calculated from the above emission spectrum as (0.332, 0.340), with a color temperature of 5493K, belonging to cool white light. Figure 4 As shown. Comparative calculations show that this device has a high color rendering index of 98.

[0061] Example 3

[0062] Weigh 6 mg of the blue carbon dots prepared in Example 1 and dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution. Stir at 500 r / min for 5 min to obtain a mixed solution of blue carbon dots / polyvinylpyrrolidone complex.

[0063] Take 30 μL of the mixed solution and drop it onto the LED lamp cap. Dry it and then repeat the dropping process until a total of 90 μL is added. After complete drying, a blue carbon dot / polyvinylpyrrolidone composite fluorescent film is obtained.

[0064] A lamp cap with the fluorescent film is placed on an LED chip with an excitation wavelength of 360nm to assemble a standard white LED device.

[0065] Figure 5 In the emission spectrum diagram of the aforementioned standard white LED device, excited by a 360nm excitation chip, its emission spectrum covers most of the visible light region. The calculated CIE coordinates of the device are (0.359, 0.364), with a color temperature of 4548K, classifying it as standard white light, and a color rendering index of 97. Figure 6 As shown.

[0066] Example 4

[0067] Weigh 10 mg of the blue carbon dots prepared in Example 1, dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution, and stir at 500 r / min for 5 min to obtain a mixed solution of blue carbon dots / polyvinylpyrrolidone complex.

[0068] Take 30 μL of the mixed solution and drop it onto the LED lamp cap. Dry it and then repeat the dropping process until a total of 90 μL is added. After complete drying, a blue carbon dot / polyvinylpyrrolidone composite fluorescent film is obtained.

[0069] A lamp cap with the fluorescent film is placed on an LED chip with an excitation wavelength of 360nm to assemble a warm white LED device.

[0070] Figure 7 In the aforementioned warm white LED device emission spectrum diagram, excited by a 360nm excitation chip, its emission spectrum covers most of the visible light region. The calculated CIE coordinates of the device are (0.427, 0.388), with a color temperature of 3033K, classifying it as warm white light, and a color rendering index of 97. Figure 8 As shown.

[0071] Example 5

[0072] Weigh 0.5 mg of the blue carbon dots prepared in Example 1, dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution, and stir at 500 r / min for 5 min to obtain a mixed solution of blue carbon dots / polyvinylpyrrolidone composite.

[0073] Take 30 μL of the mixed solution and drop it onto the LED lamp cap. Dry it and then repeat the dropping process until a total of 90 μL is added. After complete drying, a blue carbon dot / polyvinylpyrrolidone composite fluorescent film is obtained.

[0074] A lamp cap with the fluorescent film is placed over an LED chip with an excitation wavelength of 360nm to assemble a blue LED device. Figure 9 The emission spectrum of the device shows that it emits blue light.

[0075] Example 6

[0076] Weigh 5 mg of the blue carbon dots prepared in Example 1, dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution, and stir at 500 r / min for 5 min to obtain a mixed solution of blue carbon dots / polyvinylpyrrolidone complex.

[0077] Take 3 mL of the mixed solution and drop it onto the surface of a 5 cm × 5 cm ultra-white glass. Dry it in the air and couple a solar cell onto the side of the ultra-white glass to obtain a blue solar concentrator.

[0078] Figure 10 The absorption efficiency spectrum of the prepared blue solar concentrator is given. In the figure, the red line represents the absorption spectrum of the carbon dot polymer material, and the light blue background is the solar spectrum. The blue curve is obtained by multiplying the two curves, and then the integral is compared with the integral area of ​​the solar spectrum. The ratio is taken as the absorption efficiency of the material, which is 2.4%.

[0079] Example 7

[0080] Weigh 540 mg of phytic acid and 180 mg of o-phenylenediamine, add them to 20 mL of ethanol, place them in a polytetrafluoroethylene-lined stainless steel autoclave, and solvothermal treat them at 230 °C for 22 h. After the reaction is complete, allow them to cool naturally to room temperature in air to obtain the crude product of carbon dot solution.

[0081] The crude carbon dot solution was filtered using a 0.22 μm syringe filter. The filtrate was then rotary evaporated and vacuum dried to obtain solid green carbon dots.

[0082] The green carbon dots prepared above were dissolved in DMSO solution to obtain a green carbon dot solution, and its physical properties and luminescence performance were characterized.

[0083] Figure 11 In the transmission electron microscopy (TEM) morphology image, the green carbon dots are spherical in shape, without obvious aggregation, with a narrow particle size distribution range and an average particle size of 4.69 nm.

[0084] Figure 12 In the fluorescence spectrum, the emission peak position of the green carbon dot solution was the same when excited with different excitation wavelengths, indicating that the green carbon dot solution has the characteristic of independent excitation. Its optimal excitation wavelength is at 380 nm, and the optimal emission wavelength under 380 nm excitation light is 500 nm, with a quantum yield of 68.68%.

[0085] Example 8

[0086] Weigh 5 mg of the green carbon dots prepared in Example 7 and dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution. Stir at 500 r / min for 5 min to obtain a mixed solution of green carbon dots / polyvinylpyrrolidone complex.

[0087] Take 30 μL of the mixed solution and drop it onto the LED lamp cap. Dry it and then repeat the dropping process until a total of 90 μL is added. After complete drying, a green carbon dot / polyvinylpyrrolidone composite fluorescent film is obtained.

[0088] A lamp cap with the fluorescent film is placed over an LED chip with an excitation wavelength of 360nm to assemble a green LED device. Figure 13 The emission spectrum of the device shows that it emits green light.

[0089] Example 9

[0090] Weigh 5 mg of the green carbon dots prepared in Example 7 and dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution. Stir at 500 r / min for 5 min to obtain a mixed solution of green carbon dots / polyvinylpyrrolidone complex.

[0091] Take 3 mL of the mixed solution and drop it onto the surface of a 5 cm × 5 cm ultra-white glass. Dry it in the air and couple a solar cell onto the side of the ultra-white glass to obtain a green solar concentrator.

[0092] Figure 14 In the absorption efficiency spectrum of the green solar concentrator, the absorption spectrum of the carbon dot polymer material was integrated with the solar spectrum, and then the ratio of the integral of the solar spectrum was obtained to obtain the absorption efficiency of the material as 6.3%.

[0093] Example 10

[0094] Weigh 60 mg of phytic acid and 180 mg of o-phenylenediamine, add them to 20 mL of ethanol, place them in a polytetrafluoroethylene-lined stainless steel autoclave, and solvothermal treat them at 230 °C for 22 h. After the reaction is complete, allow them to cool naturally to room temperature in air to obtain the crude product of carbon dot solution.

[0095] The crude carbon dot solution was filtered through a 0.22 μm syringe filter. The filtrate was evaporated to remove some of the solvent and then added dropwise to 100 mL of water to obtain a turbid liquid. The solution was centrifuged at 10,000 rpm for 10 min, and the process was repeated twice. After discarding the supernatant, the solution was dried to obtain a black powder with reddish carbon dots.

[0096] The red carbon dots prepared above were dissolved in DMSO solution to obtain a red carbon dot solution, and its physical properties and luminescence performance were characterized.

[0097] Figure 15 In the transmission electron microscopy (TEM) image of the red carbon dot solution, the red carbon dots are spherical in shape, without obvious aggregation, with a narrow particle size distribution range and an average particle size of 7.65 nm.

[0098] Figure 16 The image shows the fluorescence spectrum of the red carbon dot solution. When the carbon dot solution is excited with different excitation wavelengths, the emission peak position is the same, indicating that the red carbon dot solution has the characteristic of independent excitation. The optimal excitation wavelength is at 520 nm, and the optimal emission wavelength under 520 nm excitation light is 593 nm, with a quantum yield of 60.29%.

[0099] Example 11

[0100] Weigh 5 mg of the red carbon dots prepared in Example 10, dissolve them in 10 mL of a 120 mg / mL polyvinylpyrrolidone ethanol solution, and stir at 500 r / min for 5 min to obtain a mixed solution of red carbon dots / polyvinylpyrrolidone complex.

[0101] Take 30 μL of the mixed solution and drop it onto the LED lamp cap. Dry it and then repeat the dropping process until a total of 90 μL is added. After complete drying, a red carbon dot / polyvinylpyrrolidone composite fluorescent film is obtained.

[0102] A lamp cap with the fluorescent film is placed over an LED chip with an excitation wavelength of 360nm to assemble a red LED device. Figure 17 The emission spectrum of the device shows that it emits red light.

[0103] Example 12

[0104] Weigh 5 mg of the red carbon dots prepared in Example 7 and dissolve them in 10 mL of a 120 mg / mL polymethyl methacrylate (DMF) solution. Stir at 500 rpm for 5 min to obtain a mixed solution of red carbon dots / polymethyl methacrylate composite.

[0105] Take 3 mL of the mixed solution and drop it onto the surface of a 5 cm × 5 cm ultra-white glass. Dry it in the air and couple a solar cell onto the side of the ultra-white glass to obtain a red solar concentrator.

[0106] Figure 18 In the absorption efficiency spectrum of the red solar concentrator, the absorption spectrum of the carbon dot polymer material was integrated with the solar spectrum, and the ratio of the integral of the carbon dot polymer material with the solar spectrum was used to obtain the material absorption efficiency of 23.3%.

[0107] The above embodiments of the present invention do not describe all details exhaustively, nor do they limit the present invention to the embodiments described above. Various changes, modifications, substitutions, and variations made by those skilled in the art to these embodiments without departing from the principles and spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A type of blue, green, and red fluorescent carbon dots with high fluorescence quantum yield is prepared by using phytic acid and o-phenylenediamine as the sole carbon and nitrogen source precursors, dispersed in ethanol for a solvothermal reaction, and controlling the mass ratio of the carbon and nitrogen sources to obtain blue, green, and red carbon dots with high fluorescence quantum yield, wherein: Blue light carbon dots were obtained when the mass ratio of phytic acid to o-phenylenediamine was (8-20):

1. The blue light carbon dots exhibited excitation-dependent characteristics in solution. Green carbon dots were obtained when the mass ratio of phytic acid to o-phenylenediamine was (2-5):

1. These green carbon dots exhibited excitation-independent properties in solution. When the mass ratio of phytic acid to o-phenylenediamine is (0.1-1):1, red-light carbon dots are obtained, which exhibit excitation-independent characteristics in solution; The quantum yields of the blue, green, and red carbon dots reached 19.2%, 68.68%, and 60.28%, respectively.

2. The method for preparing blue, green, and red primary color fluorescent carbon dots according to claim 1 involves dispersing phytic acid and o-phenylenediamine in ethanol at different mass ratios and carrying out a solvothermal reaction at 180–250°C to prepare blue, green, and red primary color carbon dots with high fluorescence quantum yield.

3. The method for preparing blue, green, and red primary color fluorescent carbon dots according to claim 2, characterized in that: The solvothermal reaction time is 10–34 h.

4. The application of the blue, green, and red primary color fluorescent carbon dots as described in claim 1 in the fabrication of light-emitting diode devices.

5. The application according to claim 4 is to prepare a solid-state light-emitting three-primary-color carbon dot / polymer film by mixing the blue, green, and red primary-color fluorescent carbon dots with a polymer solution, and assemble it with a 360nm excitation wavelength ultraviolet chip as a fluorescent material to prepare a multicolor light-emitting diode.

6. The application according to claim 4 is to prepare a solid luminescent carbon dot / polymer film by mixing the blue carbon dots with a polymer solution, and assemble it as a fluorescent material with an ultraviolet chip with an excitation wavelength of 360nm. By adjusting the proportion of blue carbon dots, the emission spectrum of the film covers the entire visible light region, and cool white light, standard white light, or warm white light-emitting diodes are prepared respectively.

7. The application of the blue, green, and red primary color fluorescent carbon dots as described in claim 1 in the preparation of multicolor fluorescent solar concentrators.

8. The application according to claim 7 is to prepare a fluorescent solar concentrator by mixing the blue, green and red primary color fluorescent carbon dots with a polymer solution to obtain a mixed solution, coating it on a glass surface and coupling it with a solar cell.

9. The application according to claim 5, 6 or 8, characterized in that: The polymer solution is a solution obtained by dissolving at least one of polyvinylpyrrolidone, polyvinyl alcohol, polymethyl methacrylate or polysiloxane in its soluble organic solvent.

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