Quantum dot composite material, preparation method thereof and quantum dot light emitting diode

Abstract

The application relates to the technical field of display, and provides a quantum dot composite material and a quantum dot light emitting diode. The quantum dot composite material comprises quantum dots and perylene acid ester, and the perylene acid ester is combined on the surface of the quantum dots. The quantum dot composite material provided by the application can effectively improve the light emitting efficiency of quantum dot material, improve the light emitting performance of the quantum dot material, and promote the application of the quantum dot material in the QLED field.

Description

Technical Field

[0001] This application belongs to the field of display technology, and particularly relates to a quantum dot composite material and its preparation method, as well as a quantum dot light-emitting diode. Background Technology

[0002] LCD displays, as the mainstream display technology today, not only require backlights but also suffer from numerous limitations such as high power consumption, complex structure and manufacturing processes, and high costs. Using quantum dots instead of traditional phosphors significantly improves the color gamut of the display. The application of quantum dots in backlight modules shows that displays using quantum dots as the luminescent material can increase the NTSC color gamut from 72% to 110%. However, when quantum dots are no longer reliant on backlight technology and instead utilize active matrix quantum dot light-emitting diode (QLED) display devices, compared to traditional backlit LCDs, self-emissive QLEDs offer superior display performance in scenarios such as black levels and high brightness, lower power consumption, a wider temperature range, and can be used to fabricate displays with an NTSC color gamut as high as 130%.

[0003] Quantum dots possess excellent optical properties, including continuously tunable emission peaks across the entire spectrum, high color purity, and good stability, making them a superior luminescent and optoelectronic material. Quantum dot displays utilize the unique properties of quantum dots to achieve high-performance, low-cost display technology. Their color gamut can reach approximately 130% of the NTSC color gamut, exceeding the coverage of traditional display technologies, showcasing exceptional image quality and displaying more natural and original colors. However, the long oleic acid carbon chains coating the surface of quantum dots form a potential barrier that hinders the movement of charge carriers, resulting in low charge carrier transport capacity within the device and limiting its application in optoelectronic devices.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] The purpose of this application is to provide a quantum dot composite material and its preparation method, as well as a quantum dot light-emitting diode, which aims to solve the problem that in existing quantum dot light-emitting diodes, the long-chain oily ligands on the surface of quantum dots hinder the movement of charge carriers, resulting in low charge carrier transport capacity in the device and affecting the luminous efficiency of the quantum dot light-emitting diode.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0007] A first aspect of this application provides a quantum dot composite material comprising quantum dots and a perylene ester, wherein the perylene ester is bonded to the surface of the quantum dots.

[0008] A second aspect of this application provides a method for preparing quantum dot composite materials, comprising the following steps:

[0009] Obtain a quantum dot solution with surface-bound modified ligands;

[0010] Perylene ester was added to the quantum dot solution and heated to react, so that the perylene ester was bound to the surface of the quantum dots to obtain a quantum dot composite material.

[0011] A third aspect of this application provides a quantum dot light-emitting diode, including a quantum dot light-emitting layer; wherein the material of the quantum dot light-emitting layer is the quantum dot composite material described in the first aspect or the quantum dot composite material prepared by the method described in the second aspect.

[0012] The quantum dot composite material provided in this application has perylene esters bonded to the surface of the quantum dots. When this composite material is used as a quantum dot luminescent layer material in QLEDs, under the influence of an electric field, the perylene esters in the quantum dot luminescent layer alternately generate anionic and cationic free radical intermediates. When the anionic and cationic free radical intermediates react with each other, excited-state perylene esters are generated. Subsequently, the excited-state perylene esters transition back to the ground state, transferring energy to the quantum dots covalently bonded to the perylene esters, thus exciting the quantum dots and causing them to emit fluorescence, effectively improving the luminescence efficiency of the quantum dot material. Simultaneously, the various groups contained in the perylene esters, such as benzene rings, carboxyl groups, and amino groups, contain lone pairs of electrons, which readily form delocalized large π bonds. This facilitates the transfer of more or more electrons into the quantum dots during electroluminescence, preventing a decrease in luminescence due to a mismatch between hole and electron injection during electroluminescence. In summary, the quantum dot composite material provided in this application can effectively improve the luminescence efficiency and performance of quantum dot materials, promoting their application in the QLED field.

[0013] The method for preparing quantum dot composite materials provided in this application involves reacting a quantum dot solution with modified ligands with perylene ester to obtain quantum dots with perylene ester bound to their surface. This improves the luminescence efficiency and performance of the quantum dot material, promoting its application in the QLED field. The method is simple to operate, requires no stringent conditions, and is conducive to large-scale production.

[0014] The quantum dot light-emitting diode (LED) provided in this application uses perylene ester-bonded quantum dots as the surface material for the quantum dot light-emitting layer. When the LED operates, the quantum dot light-emitting layer transfers energy through the perylene ester to the covalently bonded quantum dots, exciting them and causing them to emit fluorescence, effectively improving the luminous efficiency of the quantum dot material. Furthermore, the structural characteristics of perylene ester itself make it easy to form delocalized large π bonds, which facilitates the transfer of more or more electrons into the quantum dots during electroluminescence, avoiding the reduction in luminescence caused by the mismatch between hole and electron injection during electroluminescence. In summary, the quantum dot LED provided in this application improves the luminous efficiency of the device. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the preparation of quantum dot composite materials provided in the embodiments of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of a quantum dot light-emitting diode provided in an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of a positive quantum dot light-emitting diode including a substrate and an electron transport layer provided in an embodiment of the present invention;

[0018] Figure 4 This is a schematic diagram of the structure of an inverted quantum dot light-emitting diode including a substrate and an electron transport layer, provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] The term "LCD" is an abbreviation for "Liquid Crystal Display," which refers to a liquid crystal display.

[0021] The term "NTSC" is an abbreviation for "National Television Standards Committee," which refers to the (United States) National Television Standards Committee.

[0022] The term "QLED" is an abbreviation for "Quantum Dot Light Emitting Diode," which refers to a quantum dot light-emitting diode.

[0023] On one hand, embodiments of this application provide a quantum dot composite material, comprising quantum dots and perylene ester, wherein the perylene ester is bonded to the surface of the quantum dots.

[0024] In this embodiment, quantum dots are the main body of the composite material. When the quantum dot composite material is used as the quantum dot light-emitting layer of a quantum dot light-emitting diode, the quantum dots in the composite material serve as the light-emitting body, while perylene ester is used to improve the light-emitting performance of the quantum dots. Specifically, perylene ester is used to improve the light-emitting efficiency of the quantum dots.

[0025] Quantum dots include the quantum dot body, and the type of quantum dot body is not strictly limited; any quantum dot can be selected as the light-emitting layer material for QLED quantum dots. In some embodiments, the quantum dot body is selected from CdSe, ZnSe, PbSe, CdTe, InP, GaN, GaP, AlP, InN, ZnTe, InAs, GaAs, CaF2, and Cd. 1-x Zn x S, Cd 1-x Zn x Se、CdSeyS 1-y 、PbSeyS 1-y ZnXCd 1-X Te, CdS / ZnS, Cd 1-x Zn x S / ZnS, Cd 1-x Zn x Se / ZnSe, CdSe 1-x S x / CdSe y S 1-y / CdS、CdSe / Cd 1-x Zn x Se / CdyZn 1-y Se / ZnSe, Cd 1-x Zn x Se / CdyZn 1-y Se / ZnSe, CdS / Cd 1-x Zn x S / Cd y Zn 1-y S / ZnS, NaYF4, NaCdF4, Cd 1-x ZnxSeyS 1-y CdSe / ZnS, Cd 1-x Zn x Se / ZnS, CdSe / CdS / ZnS, CdSe / ZnSe / ZnS, Cd 1-x Zn x Se / Cd y Zn 1-yThe material may be selected from at least one of S / ZnS and InP / ZnS, but is not limited thereto. The values ​​of x and y satisfy: 0 < x < 1, 0 < y < 1.

[0026] The surface of the quantum dot contains modified ligands, which coat the surface of the quantum dot bulk. Perylene esters are bound to the surface of the quantum dot through the modified ligands. In other words, the modified ligands act as a bridge connecting the perylene esters and the quantum dot bulk.

[0027] The modifying ligands on the quantum dot surface are organic compounds. In some embodiments, the modifying ligands contain a first active group and a second active group. The first active group is used to bind to the quantum dot bulk, and the second active group is used to bind to the perylene ester. In this case, the quantum dot composite material achieves the binding of the perylene ester to the quantum dots through the modifying ligands, thereby enabling the perylene ester to enhance the luminescence efficiency of the quantum dots. The first active group can be selected from functional groups that bind to metal elements on the quantum dot surface, such as thiol groups or carboxyl groups.

[0028] Considering that when the first active group is selected from groups other than thiol, the second active group may participate in the binding with the metal elements on the quantum dot surface, thus limiting the selection of the second active group, in some embodiments, the first active group of the modified ligand is a thiol, and the second active group is selected from at least one of hydroxyl, carboxyl, and amino groups. Compared with other groups, thiol has a stronger coordination ability with the metal elements on the quantum dot surface. In this case, the thiol forms a coordination bond with the quantum dot, resulting in a surface-modified quantum dot; while the hydroxyl, carboxyl, amino, or other groups at the other end of the modified ligand connect with the perylene ester surface groups, realizing the binding of the perylene ester on the quantum dot. Exemplarily, the modified ligand is selected from at least one of mercaptoacetic acid, mercaptoethanol, mercaptoethylamine, and mercaptopropionic acid, but is not limited thereto.

[0029] In some embodiments, the volume ratio of the quantum dot bulk to the modified ligand is (30–50):1. In this case, the modified ligand is bound to the quantum dot bulk in an appropriate amount, while the perylene ester is bound to the quantum dot through the modified ligand, thereby obtaining an appropriate amount of perylene ester. If the amount of modified ligand is too small, the modified ligand cannot adequately encapsulate the quantum dot bulk; if the amount of modified ligand is too large, it will reduce the luminescence efficiency of the quantum dot.

[0030] In this embodiment, perylene ester is bonded to the surface of the quantum dots to improve their luminescence efficiency. In some embodiments, the perylene ester has the structure shown in Formula 1 below:

[0031]

[0032] In Formula 1, R1, R2, R3, and R4 are each independently selected from saturated alkane groups, and R5, R6, R7, R8, R9, and R6 are selected from saturated alkane groups. 10R 11 and R 12 Each component is independently selected from one of the following: hydrogen atom, halogen atom, carboxyl group, hydroxyl group, or amino group. In this case, under the influence of an electric field, perylene esters alternately generate anionic and cationic free radical intermediates. When these intermediates react, an excited-state perylene ester is formed. Subsequently, the excited-state perylene ester transitions back to the ground state, transferring energy to the quantum dot covalently bonded to it, thus exciting the quantum dot and causing it to emit fluorescence, effectively improving the luminescence efficiency of the quantum dot material. Simultaneously, the various groups contained in the perylene ester, such as benzene rings, carboxyl groups, and amino groups, contain lone pairs of electrons, readily forming delocalized large π bonds. This facilitates the transfer of more or more electrons into the quantum dot during electroluminescence, preventing a decrease in luminescence due to a mismatch between hole and electron injection during electroluminescence.

[0033] In some embodiments, the perylene ester is selected from at least one of ethyl 3,4,9,10-perylenetetracarboxylate, octyl 3,4,9,10-perylenetetracarboxylate, hexadecyl 3,4,9,10-perylenetetracarboxylate, ethyl 1,7-dibromo-3,4,9,10-perylenetetracarboxylate, n-pentyl 1-carboxy-3,4,9,10-perylenetetracarboxylate, n-hexyl 1-amino-3,4,9,10-perylenetetracarboxylate, and ethyl 1,7-dihydroxy-3,4,9,10-perylenetetracarboxylate. This class of perylene esters can improve the luminescence efficiency of quantum dot materials by transferring their own energy to the quantum dot; and they can also improve the problem of reduced luminescence caused by the mismatch between hole and electron injection during electroluminescence through the delocalized large π bonds formed by their own structure.

[0034] In some embodiments, the molar ratio of quantum dots to perylene ester is 1:(0.1–0.3). In this case, the surface of the quantum dots is coated with an appropriate amount of perylene ester, thereby effectively improving the luminous efficiency of the quantum dots through the two effects mentioned above. When the molar ratio of quantum dots to perylene ester is less than 1:0.1, the amount of perylene ester composited with the quantum dots is small, and its effect on improving the carrier efficiency of the quantum dots is not significant; while when the molar ratio of quantum dots to perylene ester is greater than 1:0.3, the content of perylene ester bound to the surface of the quantum dots is too large, resulting in poor dispersion of the quantum dot composite material in the solvent, high film roughness after film formation, and affecting the performance of QLED devices.

[0035] The quantum dot composite material provided in this application embodiment can be prepared by the following method or by other methods.

[0036] Secondly, such as Figure 1 As shown in the figure, this application provides a method for preparing quantum dot composite materials, including the following steps:

[0037] S01. Obtain a quantum dot solution with surface-bound modified ligands;

[0038] S02. Perylene ester is added to a quantum dot solution and heated to react, so that the perylene ester binds to the surface of the quantum dots to obtain a quantum dot composite material.

[0039] The method for preparing quantum dot composite materials provided in this application involves reacting a quantum dot solution with modified ligands with perylene ester to obtain quantum dots with perylene ester bound to their surface. This improves the luminescence efficiency and performance of the quantum dot material, promoting its application in the QLED field. This method is simple to operate, requires no stringent conditions, and is conducive to large-scale production.

[0040] In step S01 above, the quantum dot solution with surface-modified ligands refers to a solution formed by dispersing quantum dots with surface-modified ligands in an organic solvent. The quantum dots with surface-modified ligands refer to quantum dots with modified ligands bound to their surface.

[0041] In some embodiments, the preparation method of the quantum dot solution with modified ligands bound to its surface is as follows:

[0042] S011. Prepare the initial quantum dot colloidal solution;

[0043] S012. The initial quantum dot colloidal solution is heated in an inert atmosphere, and a modifying ligand is added to bind the modifying ligand to the surface of the initial quantum dots, thereby obtaining a quantum dot solution with the modifying ligand bound to its surface.

[0044] In step S011 above, the initial quantum dot colloidal solution refers to a solution obtained by dispersing initial quantum dots in an organic solvent. The initial quantum dots can be quantum dots obtained through synthesis or quantum dots with initial ligands bound to their surfaces, and the initial ligands are typically ligands introduced during the quantum dot synthesis process.

[0045] In some embodiments, the method for preparing the initial quantum dot colloidal solution is as follows: the initial quantum dots are dispersed in an organic solvent A in a certain proportion to obtain the initial quantum dot colloidal solution.

[0046] There are no strict restrictions on the type of initial quantum dot; any quantum dot can be selected as the material for the QLED quantum dot emitting layer. For example, the initial quantum dot can be the quantum dot body described above.

[0047] Organic solvent A is used to disperse the initial quantum dots. In some embodiments, organic solvent A is selected from high-boiling-point alkenes and alkanes; for example, organic solvent A is at least one of 1-octadecene (ODE), 1-hexadecene, and 1-eicosene.

[0048] In some embodiments, the concentration of the initial quantum dot colloidal solution is 20–50 mg / mL. In this case, the initial quantum dots are less prone to aggregation in the solvent, resulting in better dispersion and thus optimal contact area during the ligand exchange reaction. If the concentration of the initial quantum dot colloidal solution is too low, the initial quantum dots are too widely dispersed in organic solvent A, leading to excessive interparticle spacing and excessive grafting of modified ligands in the following steps, ultimately affecting the luminescent properties of the quantum dots. If the concentration of the initial quantum dot colloidal solution is too high, the initial quantum dots are prone to agglomeration, failing to form a good contact environment with the modified ligands added in the following steps.

[0049] In step S012 above, the initial quantum dot colloidal solution is heated in an inert atmosphere. The inert atmosphere provides safe reaction conditions, preventing the introduction of other side reactions under heating conditions after the addition of modified ligands. For example, the inert atmosphere includes, but is not limited to, an argon atmosphere.

[0050] In the step of heating the initial quantum dot colloidal solution, the heating temperature is 200℃~250℃. If the temperature is too low, the reaction rate is low, and the ligand exchange reaction may be incomplete; if the temperature is too high, the modified ligands are easily vaporized upon addition, reducing the contact probability on the initial quantum dots and thus reducing the binding rate.

[0051] After heat treatment, a modified ligand is added to initiate the reaction. It should be understood that the reaction temperature is the same as the temperature of the aforementioned heat treatment. Under high temperature conditions, the modified ligand coats the surface of the quantum dots. In some embodiments, the modified ligand contains a first active group and a second active group. Under high temperature conditions, the first active group forms a coordination bond with the quantum dots, and the modified ligand coats the surface of the quantum dots, forming a surface-modified quantum dot colloidal solution. In some embodiments, the first active group is a thiol group, and the second active group is selected from at least one of hydroxyl, carboxyl, and amino groups. Exemplarily, the modified ligand is selected from at least one of mercaptoacetic acid, mercaptoethanol, mercaptoethylamine, and mercaptopropionic acid, but is not limited thereto.

[0052] In some embodiments, in the step of heating the initial quantum dot colloidal solution in an inert atmosphere and adding the modified ligand, the volume ratio of the initial quantum dots to the modified ligand is (30-50):1.

[0053] In some embodiments, after heating the initial quantum dot colloidal solution in an inert atmosphere and adding the modified ligand, the reaction time is 0.5 hours to 1 hour. If the reaction time is short, the binding of the modified ligand to the initial quantum dots is incomplete; if the reaction time is long, the chemical reaction efficiency is low.

[0054] In step S02 above, perylene ester is added to the quantum dot solution, and the perylene ester is bonded to the surface of the quantum dots through a heating reaction to obtain a quantum dot composite material. Thus, perylene ester improves the luminescence efficiency of the quantum dots. The types and mechanisms of action of perylene ester are as described above.

[0055] In some embodiments, as described above, in the reaction system obtained by adding perylene ester to the quantum dot solution, the molar ratio of quantum dots to perylene ester is 1:(0.1 to 0.3).

[0056] In some embodiments, during the heating reaction that binds perylene esters to the surface of quantum dots, the heating temperature is 200°C to 250°C, and the reaction time is 0.5 hours to 1 hour. If the reaction temperature is low and / or the reaction time is short, the reaction rate is low, and the reaction of perylene esters binding to the surface of quantum dots is incomplete; if the reaction temperature is high, the reaction is unstable; if the reaction time is long, the chemical reaction efficiency is low.

[0057] In some embodiments, after the heating reaction is complete, the process further includes: cooling the reaction solution to room temperature, precipitating and washing the quantum dots, and then dispersing them in organic solvent B to form a dispersion solution for storage. In some embodiments, ethyl acetate, ethanol, and acetone are used for stepwise precipitation and washing to collect the quantum dot composite material. In some embodiments, organic solvent B is selected from nonpolar solvents such as n-hexane, n-octane, n-decane, chloroform, and ODE (octadecene), which have good dispersibility for quantum dot composite materials.

[0058] Thirdly, embodiments of this application provide a quantum dot light-emitting diode, including an anode and a cathode disposed opposite to each other, and a quantum dot light-emitting layer disposed between the anode and the cathode; wherein the material of the quantum dot light-emitting layer is the quantum dot composite material described above.

[0059] In this embodiment, the material of the quantum dot light-emitting layer is the quantum dot composite material described above. Specifically, the quantum dot composite material includes quantum dots and perylene ester, wherein the perylene ester is bonded to the surface of the quantum dots. The composition of the quantum dot composite material, the selection of perylene ester, the bonding between perylene ester and quantum dots, and the molar ratio of perylene ester to quantum dots are described above.

[0060] In some embodiments, the surface of the quantum dot contains a modified ligand, which coats the surface of the quantum dot bulk, and the perylene ester is bound to the surface of the quantum dot via the modified ligand. In some embodiments, the modified ligand contains a first active group and a second active group, the first active group being used to bind to the quantum dot bulk, and the second active group being used to bind to the perylene ester. In some embodiments, the first active group of the modified ligand is a thiol group, and the second active group is selected from at least one of hydroxyl, carboxyl, and amino groups. Exemplarily, the modified ligand is selected from at least one of mercaptoacetic acid, mercaptoethanol, mercaptoethylamine, and mercaptopropionic acid, but is not limited thereto. In some embodiments, the initial volume ratio of the modified ligand to the modified ligand is (30-50):1.

[0061] In some embodiments, such as Figure 2 As shown, the quantum dot light-emitting diode includes an anode 10 and a cathode 60 disposed opposite to each other, and a quantum dot light-emitting layer 40 disposed between the cathode 60 and the anode 10.

[0062] In some embodiments, the light-emitting diode further includes an electronic functional layer disposed between the anode 10 and the quantum dot light-emitting layer 40. The electronic functional layer includes at least one of an electron transport layer, an electron injection layer, and a hole blocking layer. In some embodiments, the quantum dot light-emitting diode further includes an electron transport layer and an electron injection layer disposed between the cathode 60 and the quantum dot light-emitting layer 40.

[0063] In some embodiments, the light-emitting diode further includes a hole functional layer disposed between the anode 10 and the quantum dot light-emitting layer 40. The hole functional layer includes at least one of a hole transport layer, a hole injection layer, and an electron blocking layer. In some embodiments, the quantum dot light-emitting diode further includes a hole injection layer and a hole transport layer disposed between the cathode 60 and the quantum dot light-emitting layer 40.

[0064] In the above embodiments, the light-emitting diode may further include a substrate, with the anode 10 or the cathode 60 disposed on the substrate.

[0065] The light-emitting diodes provided in the embodiments of this application are classified as follows: Figure 3 The positive light-emitting diode shown and as Figure 4 The image shows an inverted light-emitting diode. In this image, 100 represents the substrate, 20 represents the hole injection layer, 30 represents the hole transport layer, and 50 represents the electron transport layer.

[0066] In the above embodiments, the substrate can be a rigid substrate or a flexible substrate, specifically glass, silicon wafers, etc.

[0067] The anode can use common anode materials and thicknesses, which are not limited in this application embodiment. For example, the anode material can be indium tin oxide (ITO), indium zinc oxide (IZO), etc. The cathode can use common cathode materials and thicknesses, which are not limited in this application embodiment. For example, the cathode material can be Al, Ag, etc., and the cathode thickness is 70-100 nm. The hole injection layer material can be made of conventional hole injection materials in the art, such as PEODT:PSS, HATCN, etc. The thickness of the hole injection layer is 30 nm-100 nm. In some embodiments, the hole transport layer 30 material can be selected from conventional hole transport materials. For example, the hole transport layer 30 material includes 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))](TFB), etc. The thickness of the hole transport layer is 30 nm-100 nm. The electron transport layer can be made of conventional electron transport materials in the art, including but not limited to ZnO, TiO2, etc. The thickness of the electron transport layer is 30nm-100nm.

[0068] The following description is based on specific embodiments.

[0069] Example 1

[0070] A method for preparing a quantum dot composite material, comprising:

[0071] (1) Add an appropriate amount of CdS / ZnS to 20 ml of ODE to form a quantum dot colloidal solution with a total concentration of 20 mg / mL. Then, heat the solution to 200 °C in an argon atmosphere, and then inject mercaptoacetic acid (volume ratio, quantum dots: mercaptoacetic acid = 50:1). Keep the solution at this temperature for 30 min to form a mercaptoacetic acid-modified quantum dot solution.

[0072] (2) An appropriate amount of 3,4,9,10-perylenetetracarboxylic acid n-butyl ester was added to the above quantum dot solution (molar ratio, quantum dots:perylene ester = 1:0.1), and the mixture was stirred at 200℃ for 30 min. After the reaction was completed, the reaction solution was cooled to room temperature, and then precipitated and washed stepwise with ethyl acetate + ethanol and acetone + ethanol. The precipitate was then redispersed in n-hexane to prepare the 3,4,9,10-perylenetetracarboxylic acid n-butyl ester-CdS / ZnS quantum dot composite material.

[0073] Example 2

[0074] A method for preparing a quantum dot composite material, comprising:

[0075] (1) Add an appropriate amount of Cd1-xZnxS to 20 ml of 1-hexadecene to form a quantum dot colloidal solution with a total concentration of 30 mg / mL. Then, heat the solution to 200 °C in an argon atmosphere, and then inject mercaptoethanol (volume ratio, quantum dots: mercaptoethanol = 40:1). Keep the solution at this temperature for 30 min to form a mercaptoethanol-modified quantum dot solution.

[0076] (2) 1-Carboxy-3,4,9,10-perylenetetracarboxylic acid n-pentyl ester was added to the above quantum dot solution (molar ratio, quantum dots:perylene ester = 1:0.2), and the mixture was stirred at 200℃ for 1 h. After the reaction was completed, the reaction solution was cooled to room temperature, and then precipitated stepwise with ethyl acetate + ethanol and acetone + ethanol and washed. The precipitate was then redispersed in n-octane to prepare the 1-carboxy-3,4,9,10-perylenetetracarboxylic acid n-pentyl ester-quantum dot composite material.

[0077] Example 3

[0078] A method for preparing a quantum dot composite material, comprising:

[0079] (1) Add an appropriate amount of Cd1-xZnxS / ZnS to 20 ml of 1-eicosene to form a quantum dot colloidal solution with a total concentration of 50 mg / mL. Then, heat the solution to 200 °C in an argon atmosphere, and then inject mercaptoethylamine (volume ratio, quantum dots: mercaptoethylamine = 30:1). Keep the solution at this temperature for 30 min to form a mercaptoethylamine-modified quantum dot solution.

[0080] (2) Ethyl 1,7-dihydroxy-3,4,9,10-perylenetetracarboxylate was added to the quantum dot solution above (molar ratio, quantum dots:perylene ester = 1:0.3), and the mixture was stirred at 250 °C for 1 h. After the reaction was completed, the reaction solution was cooled to room temperature, and then precipitated and washed stepwise with ethyl acetate + ethanol and acetone + ethanol. The precipitate was then redispersed in n-hexane to prepare the ethyl 1,7-dihydroxy-3,4,9,10-perylenetetracarboxylate-Cd1-xZnxS / ZnS quantum dot composite material.

[0081] Example 4

[0082] A quantum dot light-emitting diode (LED) includes a stacked structure of an anode and a cathode disposed opposite to each other, a quantum dot light-emitting layer disposed between the anode and the cathode, an electron transport layer disposed between the cathode and the quantum dot light-emitting layer, and a hole transport layer disposed between the anode and the quantum dot light-emitting layer, wherein the anode is disposed on a substrate. The substrate is made of glass, the anode is made of ITO, the hole transport layer is made of TFB with a thickness of 40 nm, the electron transport layer is made of ZnO with a thickness of 50 nm, the quantum dot material is 3,4,9,10-perylenetetracarboxylate-CdS / ZnS quantum dot composite material with a thickness of 30 nm, and the cathode is made of Al with a thickness of 80 nm.

[0083] The method for fabricating the quantum dot light-emitting diode includes the following steps:

[0084] An ITO substrate is provided, and a hole transport layer is fabricated on the ITO substrate;

[0085] A quantum dot luminescent layer is deposited on the hole transport layer. The quantum dot luminescent layer is the 3,4,9,10-perylenetetracarboxylate-CdS / ZnS quantum dot composite material obtained in the method described in Example 1.

[0086] An electron transport layer is fabricated on the quantum dot light-emitting layer;

[0087] A cathode is fabricated on the electron transport layer.

[0088] Example 5

[0089] A quantum dot light-emitting diode, which differs from Example 4 in that the quantum dot material is the 1-carboxy-3,4,9,10-perylenetetracarboxylic acid n-pentyl ester-quantum dot composite material provided in Example 2.

[0090] Example 6

[0091] A quantum dot light-emitting diode, differing from Example 4 in that the quantum dot material is ethyl 1,7-dihydroxy-3,4,9,10-perylenetetracarboxylate-Cd provided in Example 3. 1-x Zn x S / ZnS quantum dot composite material.

[0092] Example 7

[0093] A quantum dot light-emitting diode (LED) includes a stacked structure of an anode and a cathode disposed opposite to each other, a quantum dot light-emitting layer disposed between the anode and the cathode, an electron transport layer disposed between the cathode and the quantum dot light-emitting layer, a hole transport layer disposed between the anode and the quantum dot light-emitting layer, and the cathode being disposed on a substrate. The substrate is made of glass, the cathode is made of ITO, the hole transport layer is made of TFB with a thickness of 40 nm, the electron transport layer is made of ZnO with a thickness of 50 nm, the quantum dot material is 3,4,9,10-perylenetetracarboxylate-CdS / ZnS quantum dot composite material with a thickness of 30 nm, and the anode is made of Al with a thickness of 80 nm.

[0094] The method for fabricating the quantum dot light-emitting diode includes the following steps:

[0095] A cathode substrate is provided, and an electron transport layer is fabricated on the cathode substrate;

[0096] A quantum dot luminescent layer was prepared on the electron transport layer. The quantum dot luminescent layer was the 3,4,9,10-perylenetetracarboxylate-CdS / ZnS quantum dot composite material obtained by the method described in Example 1.

[0097] A hole transport layer is fabricated on a quantum dot luminescent layer;

[0098] An anode is fabricated on the hole transport layer.

[0099] Example 8

[0100] A quantum dot light-emitting diode, which differs from Example 7 in that the quantum dot material provided in Example 2 is a 1-carboxyl-3,4,9,10-perylenetetracarboxylic acid n-pentyl ester-quantum dot composite material.

[0101] Example 9

[0102] A quantum dot light-emitting diode, differing from Example 7 in that the quantum dot material is ethyl 1,7-dihydroxy-3,4,9,10-perylenetetracarboxylate-Cd provided in Example 3. 1-x Zn x S / ZnS quantum dot composite material.

[0103] Comparative Example 1

[0104] A quantum dot light-emitting diode, which differs from Example 7 in that the quantum dot material is CdS / ZnS quantum dots.

[0105] Comparative Example 2

[0106] A quantum dot light-emitting diode, differing from Example 7 in that the quantum dot material is Cd. 1-xZn x S-quantum dots.

[0107] Comparative Example 3

[0108] A quantum dot light-emitting diode, differing from Example 7 in that the quantum dot material is Cd. 1-x Zn x S / ZnS quantum dots.

[0109] The quantum dot light-emitting diodes prepared in Examples 4-9 and Comparative Examples 1-3 were subjected to performance tests. The test indicators and test methods are as follows:

[0110] (1) External quantum efficiency (EQE): Measured using an EQE optical testing instrument.

[0111] Note: The external quantum efficiency test refers to the QLED device described above, i.e., anode / hole transport film / quantum dot / electron transport film / cathode, or cathode / electron transport film / quantum dot / hole transport film / anode. The test results are shown in Table 1 below:

[0112] Table 1

[0113] Project Group External quantum efficiency (EQE) / (%) Comparative Example 1 3.48 Comparative Example 2 3.12 Comparative Example 3 4.69 Example 4 9.78 Example 5 8.64 Example 6 7.51 Example 7 8.38 Example 8 6.94 Example 9 5.22

[0114] As can be seen from Table 1 above, the external quantum efficiency of the quantum dot light-emitting diodes (the quantum dot material is perylene ester-quantum dot composite material) provided in Examples 4-9 of the present invention is significantly higher than that of the quantum dot light-emitting diodes without composite quantum dot material in Comparative Examples 1-3. This indicates that the quantum dot light-emitting diodes obtained by adding perylene ester to quantum dots as the quantum dot light-emitting layer material have better luminous efficiency.

[0115] It is worth noting that the specific embodiments provided in this invention all use blue quantum dots (CdS / ZnS, Cd... 1-x Zn x S, Cd 1-x Zn x S / ZnS) is used as the light-emitting layer material because the blue light-emitting system is a widely used system (in addition, the fabrication of light-emitting diodes based on blue quantum dots is relatively difficult, so it is more valuable for reference), but it does not mean that this invention is only used for the blue light-emitting system.

[0116] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A quantum dot composite material, characterized in that, The invention comprises quantum dots and a perylene ester, wherein the perylene ester is bound to the surface of the quantum dots, wherein the surface of the quantum dots contains a modified ligand, and the perylene ester is bound to the surface of the quantum dots through the modified ligand, and the perylene ester has the structure shown in Formula 1 below: Formula 1 In Formula 1, R1, R2, R3, and R4 are each independently selected from saturated alkane groups, and R5, R6, R7, R8, R9, and R6 are selected from saturated alkane groups. 10 R 11 and R 12 Each is independently selected from one of the following: hydrogen atom, halogen atom, carboxyl group, hydroxyl group, and amino group.

2. The quantum dot composite material as described in claim 1, characterized in that, The perylene ester is selected from at least one of 3,4,9,10-perylenetetracarboxylate, octyl perylenetetracarboxylate, hexadecyl perylenetetracarboxylate, 1,7-dibromo-3,4,9,10-perylenetetracarboxylate, 1-carboxyl-3,4,9,10-perylenetetracarboxylate n-pentyl ester, 1-amino-3,4,9,10-perylenetetracarboxylate n-hexyl ester, and 1,7-dihydroxy-3,4,9,10-perylenetetracarboxylate.

3. The quantum dot composite material as described in claim 1, characterized in that, The molar ratio of the quantum dots to the perylene ester is 1:(0.1~0.3).

4. The quantum dot composite material according to any one of claims 1 to 3, characterized in that, The modified ligand contains a first active group and a second active group, wherein the first active group is used to bind to the quantum dot bulk and the second active group is used to bind to the perylene ester.

5. The quantum dot composite material as described in claim 4, characterized in that, The first active group is a thiol group, and the second active group is selected from at least one of hydroxyl, carboxyl, and amino groups.

6. The quantum dot composite material as described in claim 4, characterized in that, The modified ligand is selected from at least one of thioglycolic acid, mercaptoethanol, mercaptoethylamine, and mercaptopropionic acid; and / or The volume ratio of the quantum dot to the modified ligand is (30~50):

1.

7. A method for preparing a quantum dot composite material, characterized in that, Includes the following steps: Obtain a quantum dot solution with surface-bound modified ligands; Perylene ester was added to the quantum dot solution and heated to react, so that the perylene ester was bound to the surface of the quantum dots through the modified ligand, thus obtaining a quantum dot composite material. The perylene ester has the structure shown in Formula 1: Formula 1 In Formula 1, R1, R2, R3, and R4 are each independently selected from saturated alkane groups, and R5, R6, R7, R8, R9, and R6 are selected from saturated alkane groups. 10 R 11 and R 12 Each is independently selected from one of the following: hydrogen atom, halogen atom, carboxyl group, hydroxyl group, and amino group.

8. The method for preparing quantum dot composite materials as described in claim 7, characterized in that, In the reaction system obtained by adding perylene ester to the quantum dot solution, the molar ratio of quantum dots to perylene ester is 1:(0.1~0.3); and / or The heating reaction is carried out at a temperature of 200℃ to 250℃ for a time of 0.5 hours to 1 hour.

9. The method for preparing the quantum dot composite material according to any one of claims 7 or 8, characterized in that, The preparation method of the quantum dot solution with modified ligands bound to its surface is as follows: Prepare the initial quantum dot colloidal solution; The initial quantum dot colloidal solution was heated in an inert atmosphere, and a modifying ligand was added to bind the modifying ligand to the surface of the initial quantum dots, resulting in a quantum dot solution with the modifying ligand bound to the surface.

10. The method for preparing the quantum dot composite material as described in claim 9, characterized in that, The initial quantum dot colloidal solution has a concentration of 20–50 mg / mL; and / or In the step of heating the initial quantum dot colloidal solution in an inert atmosphere and adding the modifying ligand, the volume ratio of the initial quantum dots to the modifying ligand is (30~50):1; and / or The heat treatment temperature is 200℃~250℃; and / or The initial quantum dot colloidal solution was heated in an inert atmosphere, and after the addition of the modified ligand, the reaction time was 0.5 hours to 1 hour.

11. A quantum dot light-emitting diode, characterized in that, It includes a quantum dot light-emitting layer; wherein the material of the quantum dot light-emitting layer is the quantum dot composite material according to any one of claims 1 to 6 or the quantum dot composite material prepared by the method according to any one of claims 7 to 10.

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