Multicolor carbon quantum dot with high fluorescence quantum yield, LED device based on carbon quantum dot, preparation method and application

Abstract

The invention discloses a preparation method and application of a multicolor LED device and a white light LED device based on multicolor carbon quantum dots with high fluorescence quantum yield. The method comprises the following steps: firstly synthesizing sky-blue light-emitting carbon quantum dots from citric acid, and then carrying out surface modification on the sky-blue light-emitting carbon quantum dots to obtain dark blue, sky-blue, green, yellow, orange, red and near-infrared light-emitting multicolor carbon quantum dots, and the light-emitting central wavelengths are respectively 400nm, 460nm, 535nm, 577nm, 640nm, 750nm and 880nm. The multi-color and white-light LED device is prepared by taking the multi-color carbon quantum dots as a light-emitting layer. The synthesis method is simple and convenient, the prepared carbon quantum dot is high in fluorescence quantum yield and low in cost and toxicity, the prepared multicolor and white light LED device is high in brightness, and the external quantum efficiency EQE can reach 2.42% to the maximum.

Description

Technical Field

[0001] The present invention belongs to the field of nanotechnology and relates to a multi-color carbon quantum dot with high fluorescence quantum yield, a multi-color LED device based on the carbon quantum dot, a white light LED device, a preparation method and an application thereof. Background Art

[0002] Carbon quantum dots (CDs) have attracted widespread attention due to their excellent photostability, small size, good biocompatibility, and tunable photoluminescence properties, making them attractive for applications in sensing, bioimaging, information encryption, and optoelectronic devices. Within carbon nanomaterial research, carbon-based, high-efficiency luminescent materials are not only the next technological frontier in optoelectronics but also offer an alternative to traditional semiconductor inorganic quantum dots (QDs). In the past few years, significant progress has been made in the design and synthesis of highly tunable bandgap fluorescent CQDs. Quantum yields (QYs) can be enhanced through various strategies, such as heteroatom doping, surface engineering, or separation and purification of passive products. Furthermore, CQDs have demonstrated widespread applications in optoelectronics. For example, the reported blue-to-red light-emitting diodes (LEDs) based on CQDs have laid a solid foundation for the development of novel CQD-based display technologies. However, despite intensive research on the electronic and optical properties of CQDs, effective wavelength control strategies for CQDs remain lacking, severely hindering the application of CQD-based LEDs in high-performance displays. Summary of the Invention

[0003] In order to address the deficiencies in the prior art, the present invention aims to provide a method for preparing multi-color carbon quantum dots with high fluorescence quantum yield, multi-color LED devices, and white light LED devices. The carbon quantum dots have high fluorescence quantum yield, low cost and toxicity, and the emission wavelength can be tuned to the entire visible spectrum and near-infrared band.

[0004] As used in the present invention, the term "carbon quantum dots" (CQDs), also known as carbon dots or carbon nanodots, are a class of zero-dimensional carbon nanomaterials with significant fluorescent properties. They are ultrafine, dispersed, quasi-spherical carbon nanoparticles with a size of less than 10 nm.

[0005] The present invention provides a method for preparing multi-color carbon quantum dots with high fluorescence quantum yield, comprising the following steps:

[0006] (1) Anhydrous citric acid is placed in a crucible and heated to react to obtain carbon quantum dot solids, which are then dispersed in a solvent to obtain a carbon quantum dot solution T-CQDs.

[0007] In step (1), the mass of the citric acid is 0.18-0.24 g; preferably, 0.2 g.

[0008] In step (1), the heating reaction time is 10-50 min; preferably, 20 min.

[0009] In step (1), the temperature of the heating reaction is 200-240°C; preferably, 200°C.

[0010] In step (1), the solvent is one or more of ethanol, methanol, etc.; preferably, it is ethanol.

[0011] In step (1), the volume of the solvent is 4-5 mL; preferably, 5 mL.

[0012] (2) T-CQDs were subjected to amide coupling reaction with 3,4,5,6-tetrafluorobenzene-1,2-diamine, 2-methoxyaniline, 4-bromo-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 4-fluoro-1-aminonaphthalene and 2,6-diaminoanthracene under the catalysis of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), respectively, to obtain the corresponding functionalized carbon quantum dots, which were recorded as TFOPD@T-CQDs, OAD@T-CQDs, BrOPD@T-CQDs, ClOPD@T-CQDs, FOPD@T-CQDs, FNA@T-CQDs and DEA@T-CQDs.

[0013] In step (2), the mass ratio of the T-CQDs to the 3,4,5,6-tetrafluorobenzene-1,2-diamine, the 2-methoxyaniline, the 4-bromo-o-phenylenediamine, the 4-chloro-o-phenylenediamine, the 4-fluoro-o-phenylenediamine, the 4-fluoro-1-aminonaphthalene and the 2,6-diaminoanthracene is 10:(15-20), preferably 10:15.

[0014] In step (2), the mass ratio of the T-CQDs to the catalyst EDC is 10:(60-80); preferably, 10:80.

[0015] In step (2), the mass ratio of the T-CQDs to the catalyst NHS is 10:(40-60); preferably, 10:60.

[0016] In step (2), the temperature of the amide coupling reaction is 25-35°C; preferably, 25°C.

[0017] In step (2), the amide coupling reaction time is 12-16 hours; preferably, 14 hours.

[0018] The present invention also proposes a multi-color carbon quantum dot with high fluorescence quantum yield prepared by the above method. The modified ligand small molecule has a clear structure, the fluorescence wavelength is adjustable in the range of 350nm-1000nm, and the quantum yield is as high as 79%.

[0019] The present invention also provides a method for preparing a multicolor LED device and a white light LED device based on the multicolor carbon quantum dots with high fluorescence quantum yield, comprising the following steps:

[0020] (a) Pre-purchased ITO conductive glass was treated with toluene, acetone, ethanol, water, ultrasound, and ozone in sequence as the substrate for the LED device.

[0021] In step (a), the specifications of the ITO conductive glass include 1cm×1cm, 1cm×2cm, 2cm×2cm, etc.; preferably, it is 2cm×2cm.

[0022] In step (a), the amount of the toluene, the acetone, the ethanol and the water is 15 ml.

[0023] In step (a), the ultrasonication time is 12-15 min; preferably, 15 min.

[0024] In step (a), the ozone treatment time is 15-30 minutes; preferably, 30 minutes.

[0025] (b) Spin-coating PEDOT:PSS on the ITO conductive glass treated in step (a), and annealing the resulting film to form a hole injection layer (HIL).

[0026] In step (b), the spin coating speed is 2000-2400 rpm; preferably, 2000 rpm.

[0027] In step (b), the spin coating time is 20-30 s; preferably, 30 s.

[0028] In step (b), the annealing temperature is 160-180°C; preferably, 160°C.

[0029] In step (b), the annealing time is 10-15 minutes; preferably, 10 minutes.

[0030] (c) mixing the above-mentioned one or more functionalized carbon quantum dot solutions with a poly(9-vinyl carbazole) (PVK (poly(N-vinyl carbazole))) solution, respectively, and spin-coating the mixture on the ITO conductive glass coated with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) prepared in step (b), and annealing the mixture to form a light-emitting film, i.e., a light-emitting layer of a multicolor and / or white light LED.

[0031] In step (c), the carbon quantum dot solution is an ethanol solution of the carbon quantum dots at a concentration of 4-8 mg / mL; preferably, 5 mg / mL.

[0032] In step (c), the PVK solution is a 9-12 mg / mL PVK solution in o-dichlorobenzene; preferably, 10 mg / mL.

[0033] In step (c), the mixing ratio of the carbon quantum dot solution and the PVK solution is 1:(1.8-2.2); preferably, 1:1.8.

[0034] In step (c), the spin coating speed is 2000-2400 rpm; preferably, 2000 rpm.

[0035] In step (c), the spin coating time is 20-30 s; preferably, 30 s.

[0036] In step (c), the annealing temperature is 100-150°C; preferably, 120°C.

[0037] In step (c), the annealing time is 10-15 minutes; preferably, 10 minutes.

[0038] The light-emitting layer 1 of the white light LED in step (c) is composed of dark blue and yellow carbon quantum dots (TFOPD@T-CQDs and ClOPD@T-CQDs) mixed in a ratio of 3:1; the light-emitting layer 2 of the white light LED is composed of dark blue, green and red carbon quantum dots (TFOPD@T-CQDs, BrOPD@T-CQDs and FNA@T-CQDs) mixed in a ratio of 3:2:1.

[0039] (d) depositing an electron transport layer and a cathode in sequence on the ITO conductive glass prepared in step (c) to obtain a white light or monochromatic LED.

[0040] In step (d), the electron transport layer material is 1,3,5-tris(phenyl-2-benzimidazole)-benzene (TPBI), and the cathode material is Al.

[0041] In step (d), the deposition pressure is (3-5)×10 -4 Pa; preferably, 4×10 -4 Pa.

[0042] In step (d), the operations are all carried out in a vacuum chamber, the electron transport layer material is 1,3,5-tris(phenyl-2-benzimidazole)-benzene (TPBI), and the cathode material is Al.

[0043] In step (d), the deposition pressure is 4×10 -4 Pa.

[0044] The present invention also provides a multi-color LED device and a white light LED device prepared by the above preparation method.

[0045] The present invention also provides a method for preparing the multi-color carbon quantum dots with high fluorescence quantum yield, the multi-color carbon quantum dots with high fluorescence quantum yield, a method for preparing a multi-color LED device and a white light LED device with monochromatic carbon quantum dots with high fluorescence quantum yield, and the application of the multi-color LED device and the white light LED device in photoelectric property testing.

[0046] In a specific embodiment, the method for preparing a multi-color LED device and a white light LED device with multi-color carbon quantum dots having high fluorescence quantum yield according to the present invention comprises the following steps:

[0047] (I) 0.2 g of anhydrous citric acid was placed in a crucible and heated at 200°C for 20 min to obtain carbon quantum dot solids, which were then dispersed in 5 mL of ethanol solution to obtain a carbon quantum dot solution as T-CQDs.

[0048] (II) 10 mg of T-CQDs were reacted with 15 mg of 3,4,5,6-tetrafluorobenzene-1,2-diamine, 2-methoxyaniline, 4-bromo-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 4-fluoro-1-aminonaphthalene and 2,6-diaminoanthracene, respectively, under the catalysis of 80 mg of EDC and 60 mg of NHS at 25°C for 14 h to obtain the corresponding carbon quantum dots, which were recorded as TFOPD@T-CQDs, OAD@T-CQDs, BrOPD@T-CQDs, ClOPD@T-CQDs, FOPD@T-CQDs, FNA@T-CQDs and DEA@T-CQDs, respectively.

[0049] (III) ITO conductive glass with a size of 2 cm × 2 cm was ultrasonically cleaned with toluene, acetone, ethanol, and water for 15 min, followed by ozone treatment for 30 min;

[0050] (IV) PEDOT:PSS was spin-coated on ITO conductive glass at 2000 rpm for 30 s and then annealed in an oven at 160 °C for 10 min to obtain a hole injection layer (HIL);

[0051] (V) A 5 mg / mL carbon quantum dot ethanol solution was mixed with a 10 mg / mL PVK (poly(N-vinylcarbazole)) o-dichlorobenzene solution in a ratio of 1:1.8, and the mixture was spin-coated on ITO conductive glass at a speed of 2000 rpm for 30 seconds, followed by annealing in an oven at 120°C for 10 minutes to form a light-emitting layer of a multicolor and / or white light LED, wherein the light-emitting layer 1 of the white light LED was composed of dark blue and yellow carbon quantum dots (TFOPD@T-CQDs and ClOPD@T-CQDs) mixed in a ratio of 3:1; and the light-emitting layer 2 of the white light LED was composed of dark blue, green, and red carbon quantum dots (TFOPD@T-CQDs, BrOPD@T-CQDs, and FNA@T-CQDs) mixed in a ratio of 3:2:1;

[0052] (VI) The ITO conductive glass coated with PEDOT:PSS and carbon quantum dot light-emitting layers was transferred to a vacuum chamber and then -4 Pa, and then sequentially deposited with 1,3,5-tris(phenyl-2-benzimidazole)-benzene (TPBI) and Al.

[0053] The present invention also provides a method for regulating the emission of carbon quantum dots using a surface ligand modification strategy. By modifying the carboxyl groups on the surface of the carbon quantum dots through an amide coupling reaction, the charge transfer process of the surface emission state is promoted, thereby changing the luminescence energy level and achieving regulation of the luminescence wavelength.

[0054] The method of the present invention for regulating the luminescence wavelength of carbon quantum dots is to modify 3,4,5,6-tetrafluorobenzene-1,2-diamine, 2-methoxyaniline, 4-bromo-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 4-fluoro-1-aminonaphthalene and 2,6-diaminoanthracene to the surface of carbon quantum dots respectively.

[0055] The present invention has the following beneficial effects: First, carbon quantum dots with carboxyl groups on their surfaces were synthesized to emit sky-blue light. These carbon quantum dots were then functionalized to produce deep-blue carbon quantum dots TFOPD@T-CQDs, sky-blue carbon quantum dots OAD@T-CQDs, green carbon quantum dots BrOPD@T-CQDs, yellow carbon quantum dots ClOPD@T-CQDs, orange carbon quantum dots FOPD@T-CQDs, red carbon quantum dots FNA@T-CQDs, and near-infrared quantum dots DEA@T-CQDs. The central emission wavelengths of these seven carbon quantum dots were tuned from the original 460 nm to 400 nm, 460 nm, 535 nm, 577 nm, 640 nm, 750 nm, and 880 nm, respectively. Seven corresponding monochromatic LEDs and two white-light LEDs were fabricated based on these multicolored carbon quantum dots. The synthesis method of the present invention is simple and convenient. The monochromatic LED and white light LED have very high brightness. The maximum brightness of the prepared multicolor LED devices is 8366 cd·m -2 , 1717cd·m -2 , 7311cd·m -2 , 6404cd·m -2 , 3763cd·m -2 , 4219cd·m -2 and 1.9WSr - 1 m -2 The maximum brightness of white LED is 15112cd·m -2 The multi-color LED prepared by the present invention has rich colors and high luminous brightness, and bright white light LED can be prepared based on the multi-color LED.

[0056] The maximum brightness of blue light LEDs based on carbon quantum dots reported so far is 5250 cd·m -2 The maximum brightness of yellow LED is 2784cd·m -2 The maximum brightness of the red LED point is 2344cd·m -2 , the maximum brightness of white LED is 5909cd·m -2 , the maximum external quantum efficiency is 0.87%. In comparison, the LED prepared by the present invention has rich and adjustable colors and high brightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments disclosed in the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments disclosed in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0058] Figure 1 This is a photograph of the multi-color carbon quantum dots prepared in Example 1 of the present invention under the excitation of a 365nm ultraviolet lamp.

[0059] Figure 2 1 is the normalized fluorescence spectrum of the multicolor carbon quantum dots prepared in Example 1 of the present invention.

[0060] Figure 3 This is a schematic diagram of the structure of the LED device prepared in Example 2 of the present invention.

[0061] Figure 4 The following are photos and electroluminescence spectra of a multi-color LED device prepared in Example 2 of the present invention.

[0062] Figure 5 This is the brightness-current-voltage characteristic curve of the multi-color LED device prepared in Example 2 of the present invention.

[0063] Figure 6 is the external quantum efficiency EQE value of the multi-color LED prepared in Example 2 of the present invention.

[0064] Figure 7 These are photos and electroluminescence spectra of the white light LED prepared in Example 2 of the present invention.

[0065] Figure 8 1 is the brightness-current-voltage characteristic curve and EQE value of the white light LED prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0066] The present invention is further described in detail with reference to the following specific examples and accompanying drawings. The processes, conditions, experimental methods, etc. for implementing the present invention, except for those specifically mentioned below, are common knowledge and common common sense in the art and are not particularly limited by the present invention.

[0067] Obviously, the described embodiments are only some of the embodiments disclosed in the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention, its application, or use. All other embodiments derived by persons of ordinary skill in the art based on the embodiments disclosed in the present invention without inventive effort are within the scope of protection disclosed in the present invention.

[0068] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0069] The present invention discloses a method for preparing a multicolor LED device based on monochromatic carbon quantum dots with high fluorescence quantum yield and a white light LED device and its application, belonging to the field of nanotechnology and display lighting. First, sky blue luminescent carbon quantum dots are synthesized by citric acid, and then the sky blue carbon quantum dots are surface modified to obtain multicolor carbon quantum dots emitting dark blue, sky blue, green, yellow, orange, red and near-infrared light, wherein the emission center wavelengths are 400nm, 460nm, 535nm, 577nm, 640nm, 750nm and 880nm respectively. Multicolor and white light LED devices are prepared using multicolor carbon quantum dots as the light-emitting layer. The synthesis method described in the present invention is simple and convenient, the prepared carbon quantum dots have high fluorescence quantum yield, low cost and toxicity, the prepared multicolor and white light LED devices have high brightness and the external quantum efficiency (EQE) can reach up to 2.42%.

[0070] Example 1 Preparation of multicolor carbon quantum dots with high fluorescence quantum yield

[0071] 0.2 g of anhydrous citric acid was placed in a crucible and heated at 200° C. for 20 min to obtain carbon quantum dots. The obtained carbon quantum dots were dispersed in 5 mL of ethanol to obtain a carbon quantum dot solution T-CQDs. 10 mg of T-CQDs were reacted with 15 mg of 3,4,5,6-tetrafluorobenzene-1,2-diamine, 2-methoxyaniline, 4-bromo-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 4-fluoro-1-aminonaphthalene and 2,6-diaminoanthracene under the catalysis of 80 mg EDC and 60 mg NHS at 25°C for 14 h to obtain the corresponding carbon quantum dots, which were recorded as TFOPD@T-CQDs, OAD@T-CQDs, BrOPD@T-CQDs, ClOPD@T-CQDs, FOPD@T-CQDs, FNA@T-CQDs and DEA@T-CQDs, respectively.

[0072] Figure 1 This is a photo of multi-color carbon quantum dots under 365nm ultraviolet light excitation. From the results, we can see that the carbon quantum dots are rich in color and high in brightness. Figure 2 It can be seen that the luminescence wavelength range of the functionalized carbon quantum dots is 300-1000nm, among which the luminescence center wavelengths of deep blue, sky blue, green, yellow, orange, red and near-infrared multi-color carbon quantum dots are 400nm, 460nm, 535nm, 577nm, 640nm, 750nm and 880nm respectively.

[0073] Example 2 Fabrication of multi-color and white light LED devices based on multi-color emission carbon quantum dots

[0074] First, the ITO conductive glass was ultrasonically cleaned with toluene, acetone, ethanol and water for 15 minutes and then ozone treated for 30 minutes to serve as the substrate for the LED device. Then, a PEDOT:PSS hole injection layer (HIL) was spin-coated on the ITO at 2000 rpm for 30 seconds and then annealed in an oven at 160°C for 10 minutes. 5 mg / mL of one or more carbon quantum dots in ethanol were mixed with 10 mg / mL of PVK (poly(N-vinyl The solution of carbonyl chloride (Cd) and dapoxetine (Dcd) in an o-dichlorobenzene solution was mixed in a ratio of 1:1.8, and the mixture was spin-coated on ITO glass at a speed of 2000 rpm for 30 seconds, and then annealed in an oven at 120°C for 10 minutes to form the light-emitting layer of multi-color and / or white light LEDs, wherein the light-emitting layer 1 of the white light LED was composed of a mixture of dark blue and yellow carbon quantum dots in a ratio of 3:1; the light-emitting layer 2 of the white light LED was composed of a mixture of dark blue, green and red carbon quantum dots in a ratio of 3:2:1; finally, the ITO coated with the PEDOT:PSS and carbon quantum dot light-emitting layers was transferred to a vacuum chamber, and then heated in a 4×10 -4 Pa pressure, 1,3,5-tris (phenyl-2-benzimidazole) - benzene (TPBI) and Al were deposited in sequence to obtain an electroluminescent LED based on carbon quantum dots. The structure of the electroluminescent LED device is shown in FIG. Figure 3 As shown. Figure 4 AG, respectively, are the electroluminescence spectra of deep blue, sky blue, green, yellow, orange, red and near-infrared LEDs. The emission centers of the electroluminescence spectra are 402nm, 465nm, 535nm, 580nm, 635nm, 750nm and 880nm, which are consistent with the center positions of the fluorescence emission peaks. The inset is the corresponding LED photo. Figure 5 It can be seen that the maximum irradiance of near-infrared LED is 1.9WSr -1 m -2 The maximum brightness of the multi-color LED devices is 8366 cd·m -2 、1717cd·m -2 、7311cd·m -2 、6404cd·m -2 、3763cd·m -2 、4219cd·m -2 .Depend on Figure 6 It can be seen that the EQE values ​​of the LEDs are 1.88%, 0.39%, 1.74%, 1.34%, 1.43%, 1.34% and 0.62%, respectively, corresponding to deep blue, sky blue, green, yellow, orange, red and near-infrared LEDs. The electroluminescence spectra and photos of the white light LEDs prepared by mixing multi-color carbon dots are shown in Figure 2. Figure 7As shown in the figure, the spectra of the two white light LEDs cover the wavelength range of visible light, between 400nm-900nm. The spectral difference between WLED1 and WLED2 leads to different color temperatures, so the color temperature of the white light LED can be adjusted by adjusting the ratio of different carbon quantum dots. Figure 8 It can be seen that the maximum EQE value of white light LED is 2.42%, and the maximum brightness is 13143cd·m -2 .

[0075] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0076] As used in the present invention, the term "comprising" is an open expression, that is, including the contents specified in the present invention, but not excluding other aspects.

[0077] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0078] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the appended claims.

Claims

1. A method for preparing multi-color carbon quantum dots with high fluorescence quantum yield, characterized in that: The method comprises the following steps: (1) Anhydrous citric acid is placed in a crucible, heated for reaction, and the resulting solid is dispersed in a solvent to obtain a carbon quantum dot solution T-CQDs; (2) The T-CQDs were subjected to amide coupling reaction with 3,4,5,6-tetrafluorobenzene-1,2-diamine, 2-methoxyaniline, 4-bromo-o-phenylenediamine, 4-chloro-o-phenylenediamine, 4-fluoro-o-phenylenediamine, 4-fluoro-1-aminonaphthalene and 2,6-diaminoanthracene under the catalysis of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to obtain the corresponding carbon quantum dots, which were respectively recorded as TFOPD@T-CQDs, OAD@T-CQDs, BrOPD@T-CQDs, ClOPD@T-CQDs, FOPD@T-CQDs, FNA@T-CQDs and DEA@T-CQDs.

2. The preparation method according to claim 1, wherein In the step (1), the mass of the citric acid is 0.18-0.24 g; and / or the solvent is one or both of ethanol and methanol; and / or the volume of the solvent is 4-5 mL; and / or the temperature of the heating reaction is 200-240° C.; and / or the time of the heating reaction is 10-50 min.

3. The preparation method according to claim 1, wherein In the step (2), the mass ratio of the T-CQDs to the 3,4,5,6-tetrafluorobenzene-1,2-diamine, the 2-methoxyaniline, the 4-bromo-o-phenylenediamine, the 4-chloro-o-phenylenediamine, the 4-fluoro-o-phenylenediamine, the 4-fluoro-1-aminonaphthalene and the 2,6-diaminoanthracene is 10:(15-20); And / or, the mass ratio of the T-CQDs to the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is 10:(60-80); and / or, the mass ratio of the T-CQDs to the N-hydroxysuccinimide is 10:(40-60); and / or, the temperature of the amide coupling reaction is 25-35°C; and / or, the time of the amide coupling reaction is 12-16h.

4. The multicolor carbon quantum dots with high fluorescence quantum yield prepared by the method according to any one of claims 1 to 3, characterized in that: The ligand small molecule modified on the surface of the multi-color carbon quantum dots has a clear structure, a fluorescence wavelength control range of 350nm-1000nm, and a quantum yield of 79%.

5. A method for preparing a multi-color LED device and a white light LED device based on the multi-color carbon quantum dots with high fluorescence quantum yield as claimed in claim 4, characterized in that: The method comprises the following steps: (a) Pre-purchased ITO conductive glass was ultrasonically cleaned with toluene, acetone, ethanol, and water in sequence and then treated with ozone. (b) spin coating poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) on the ITO conductive glass treated in step (a) and then annealing to form a hole injection layer; (c) mixing one or more multicolor carbon quantum dot solutions and poly(9-vinylcarbazole) solutions on the ITO conductive glass prepared in step (b), and then annealing to form a light-emitting layer of a multicolor and / or white light LED; wherein the light-emitting layer 1 of the white light LED is composed of TFOPD@T-CQDs and ClOPD@T-CQDs carbon quantum dots mixed in a ratio of 3:1; and the light-emitting layer 2 of the white light LED is composed of TFOPD@T-CQDs, BrOPD@T-CQDs and FNA@T-CQDs carbon quantum dots mixed in a ratio of 3:2:1; (d) The ITO conductive glass prepared in step (c) is sequentially deposited with 1,3,5-tris(phenyl-2-benzimidazole)-benzene and Al.

6. The preparation method according to claim 5, wherein In the step (a), the specifications of the ITO conductive glass include 1cm×1cm, 1cm×2cm, and 2cm×2cm; the ultrasonic cleaning time is 12-15 minutes; the ozone treatment time is 15-30 minutes; and the amount of toluene, acetone, ethanol, and water used is 15 ml.

7. The preparation method according to claim 5, wherein In the step (b), the spin coating speed is 2000-2400 rpm; the spin coating time is 20-30 s; the annealing temperature is 160-180° C.; and the annealing time is 10-15 min.

8. The preparation method according to claim 5, wherein In the step (c), the poly(9-vinylcarbazole) solution is a 9-12 mg / mL poly(9-vinylcarbazole) o-dichlorobenzene solution; the carbon quantum dot solution is a 4-8 mg / mL carbon quantum dot ethanol solution; the mixing ratio of the carbon quantum dot solution to the PVK solution is 1:(1.8-2.2); the spin coating speed is 2000-2400 rpm; the spin coating time is 20-30 s; the annealing temperature is 100-150° C.; the annealing time is 10-15 min; and / or, In the step (d), the deposition conditions are (3-5)×10 -4 Pa.

9. A multicolor LED device and a white light LED device comprising multicolor carbon quantum dots prepared by the preparation method according to any one of claims 5 to 9.

10. A method for preparing multicolor carbon quantum dots with high fluorescence quantum yield according to any one of claims 1 to 3, a method for preparing multicolor carbon quantum dots with high fluorescence quantum yield according to claim 4, a method for preparing a multicolor LED device and a white light LED device with single-color carbon quantum dots with high fluorescence quantum yield according to claims 5 to 8, and the use of the multicolor LED device and the white light LED device according to claim 9 in photoelectric property testing.

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