Quantum dot inks, quantum dot light emitting devices, methods of making, display devices

Abstract

The application relates to a quantum dot ink, comprising an organic solvent and hydrophobic quantum dot material and polymer dopant dispersed in the organic solvent; the hydrophobic quantum dot material comprises quantum dots and hydrophobic ligands combined with the quantum dots, the hydrophobic ligands comprising a first polar group; the polymer dopant comprises at least one hydrophobic polymer, the molecular structure of the hydrophobic polymer comprising a second polar group; the binding capacity of the first polar group to the quantum dots is stronger than the binding capacity of the second polar group to the quantum dots. The quantum dot ink is beneficial to improving the efficiency of a light-emitting device.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a quantum dot ink, a quantum dot light-emitting device, a preparation method, and a display device. Background Technology

[0002] Self-emissive devices using inorganic quantum dots as electroluminescent materials possess advantages such as wide color gamut coverage, high color purity, ultra-thin and lightweight design, and flexibility, thus attracting widespread attention from academia and industry. The efficiency of quantum dot light-emitting devices satisfies the following formula:

[0003] EQE=η r χη PL η oc ,

[0004] Where, η r χ represents the efficiency of exciton generation by charge in the device, which is related to electrical balance; χ represents the proportion of excitons with spin quantum numbers that allow transitions, which is related to the properties of the material itself; η PL The quantum yield representing the radiative transition of a quantum dot; η oc This represents the external coupling efficiency for light extraction. Therefore, improving the quantum yield of radiative transitions in the quantum dot's emitting layer and the electrical balance within the device are effective ways to enhance device efficiency.

[0005] Common quantum dot light-emitting devices typically include a cathode, an anode, and an electron injection layer, an electron transport layer, and a quantum dot light-emitting layer disposed between the cathode and the anode. This device structure usually has two limitations: (1) electron injection and transport are more efficient than holes, and there is an order of magnitude difference between electrons and holes, resulting in poor charge balance in the device; (2) defects on the surface of the metal oxide nanocrystals used to fabricate the electron injection layer and the electron transport layer have a quenching effect on quantum dot excitons, resulting in a decrease in the quantum yield of radiative transitions. These are all key factors that affect the efficiency of light-emitting devices. If these two defects can be overcome, the efficiency of quantum dot light-emitting devices will be significantly improved. Solution method is a common method for fabricating functional layers of electroluminescent devices. In the process of fabricating functional layers using solution method, each functional ink is a key factor affecting the efficiency of the final light-emitting device. Therefore, research on quantum dot ink is particularly important in order to improve the efficiency of quantum dot light-emitting devices. Summary of the Invention

[0006] Therefore, it is necessary to provide a quantum dot ink, a quantum dot light-emitting device, a preparation method, and a display device that can improve device efficiency.

[0007] In a first aspect, this application provides a quantum dot ink, comprising:

[0008] Organic solvents, hydrophobic quantum dot materials, and polymer dopants;

[0009] The hydrophobic quantum dot material includes quantum dots and hydrophobic ligands bound to the quantum dots, wherein the hydrophobic ligands include a first polar group.

[0010] The polymer dopant includes at least one hydrophobic polymer, the molecular structure of which includes a second polar group;

[0011] The binding affinity of the first polar group to the quantum dot is stronger than that of the second polar group to the quantum dot.

[0012] In some embodiments, the hydrophobic ligand comprises a first nonpolar hydrophobic segment and a first polar group located at the end of the first nonpolar hydrophobic segment; and / or

[0013] The molecular structure of the hydrophobic polymer includes a main chain and side chains. The main chain includes non-conjugated polymer segments, and the side chains include a second nonpolar hydrophobic segment and a second polar group located at the end of the second nonpolar hydrophobic segment.

[0014] In some embodiments, the non-conjugated polymer segments comprise at least two elements selected from hydrogen, carbon, nitrogen, sulfur, oxygen, silicon, and selenium; and / or

[0015] The second nonpolar hydrophobic segment comprises an alkyl segment having 4 to 16 carbon atoms, or a combined segment formed by linking an alkyl segment and a substituted or unsubstituted aryl segment, wherein the total number of carbon atoms in the combined segment is 7 to 16, and in the substituted or unsubstituted aryl segment, the substituent is an alkyl segment having 1 to 10 carbon atoms; and / or

[0016] The second polar group includes one or more of phosphin, amino, and phosphoxy groups; and / or

[0017] The hydrophobic polymer has a molecular weight of 2 kDa to 200 kDa; and / or

[0018] The hydrophobic polymer exhibits no absorption in the wavelength range of 380 nm to 780 nm.

[0019] In some embodiments, the hydrophobic polymer comprises the structure shown in Formula I or Formula II:

[0020]

[0021] Where n1 and n2 represent the number of repeating units, 1≤n1≤1000, 1≤n2≤1000;

[0022] m1 represents an integer from 2 to 10, and m2 represents an integer from 2 to 10;

[0023] R is selected from H or CH3.

[0024] In some embodiments, the quantum dot has a core-shell structure; in the core-shell structure, the materials of the core layer and the shell layer are each independently selected from quantum dots of group II-VI compound semiconductors, quantum dots of group III-V compound semiconductors, quantum dots of group I-III-VI compound semiconductors, or perovskite quantum dots; the material of the core layer is selected from one or more of CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS, InP, InAs, InSb, GaAs, GaP, GaSb, HgTe, HgSe, HgS, CuInS, and CuInSe; and / or

[0025] The first nonpolar hydrophobic segment comprises aliphatic hydrocarbon or aryl nonpolar hydrophobic segments having 6 to 16 carbon atoms; and / or

[0026] The first polar group includes one or more of carboxyl, mercapto, phosphin, and amino groups.

[0027] In some embodiments, the material of the core layer is selected from one or more of CdSe and InP; and / or

[0028] The shell material is selected from one or more of CdS, ZnSe, and ZnS; and / or

[0029] The hydrophobic ligands include one or more of oleylamine, 1-dodecylthiol, oleic acid, octylamine, and octylthiol.

[0030] In some embodiments, the hydrophobic ligand in the hydrophobic quantum dot material contains 8% to 30% by mass; and / or

[0031] Based on the total weight of the quantum dot ink, the hydrophobic quantum dot material has a mass content of 1% to 20%, and the polymer dopant has a mass content of 0.03% to 0.2%; and / or

[0032] The mass ratio of the hydrophobic quantum dot material to the polymer dopant is (10–100):1; and / or

[0033] The organic solvent includes one or more of chain alkanes, cycloalkanes, haloalkanes, and aromatic compounds; and / or

[0034] The organic solvent has a melting point ≥25℃ and a boiling point of 100℃~300℃; and / or

[0035] The viscosity of the quantum dot ink is 2.5 cP to 10 cP; and / or

[0036] The surface tension of the quantum dot ink is 28 mN / m to 42 mN / m.

[0037] Secondly, this application provides a method for preparing quantum dot ink, comprising the following steps:

[0038] The organic solvent, hydrophobic quantum dot material, and polymer dopant are mixed.

[0039] The hydrophobic quantum dot material includes quantum dots and hydrophobic ligands bound to the quantum dots, wherein the hydrophobic ligands include a first polar group.

[0040] The polymer dopant includes at least one hydrophobic polymer, the molecular structure of which includes a second polar group;

[0041] The binding affinity of the first polar group to the quantum dot is stronger than that of the second polar group to the quantum dot.

[0042] In some implementations, the following steps are included:

[0043] The polymer dopant is mixed with the organic solvent in the first part to form a polymer dopant preparative solution;

[0044] The hydrophobic quantum dot material is mixed with the organic solvent described in the second part to form a quantum dot pre-suspension;

[0045] The polymer dopant preparation solution, the quantum dot preparation suspension, and the remaining portion of the organic solvent are mixed.

[0046] In some embodiments, the polymer dopant concentration in the polymer dopant preparation solution is 0.5% to 10% by mass; and / or

[0047] In the quantum dot pre-suspension, the mass concentration of the hydrophobic quantum dot material is 1.4% to 40%.

[0048] Thirdly, this application provides a quantum dot light-emitting device, comprising:

[0049] The cathode and anode are arranged opposite each other; and

[0050] A quantum dot light-emitting layer located between the cathode and the anode is prepared using the quantum dot ink described in the first aspect of this application or the quantum dot ink prepared using the method described in the second aspect of this application.

[0051] In some embodiments, the quantum dot light-emitting device further includes:

[0052] An electron injection layer and / or an electron transport layer are located between the cathode and the quantum dot light-emitting layer; the materials of the electron injection layer and the electron transport layer independently include one or more of doped or undoped zinc oxide, doped or undoped titanium dioxide, and doped or undoped tin dioxide, and the doping materials include one or more of magnesium, aluminum, and lithium;

[0053] The quantum dot luminescent layer has a self-assembled insulating dielectric layer formed at the interface with the electron injection layer and / or electron transport layer.

[0054] In some embodiments, the cathode material includes one or more of ITO, IZO, and IGZO; and / or

[0055] The anode material includes one or more of Ag, Mg, Au, and Al; and / or

[0056] The quantum dot light-emitting device further includes: a hole transport layer and / or a hole injection layer sequentially stacked between the quantum dot light-emitting layer and the anode; the material of the hole transport layer includes one or more of TCTA, CPB, NPB, and TPD; the material of the hole injection layer includes one or more of MoO3, WO3, HATCN, and F4-TCNQ.

[0057] Fourthly, this application provides a method for fabricating a quantum dot light-emitting device, comprising the following steps:

[0058] One of the cathode and anode is formed on the substrate;

[0059] Provide the quantum dot ink as described in the first aspect of this application or the quantum dot ink prepared by the method as described in the second aspect of this application, and use a solution method to fabricate a quantum dot light-emitting layer on the cathode or the anode;

[0060] The other of the cathode and the anode is formed on top of the quantum dot light-emitting layer.

[0061] In some implementations, the following steps are included:

[0062] The cathode is formed on the substrate;

[0063] An electron injection layer and / or an electron transport layer are formed on the cathode; the materials of the electron injection layer and the electron transport layer independently include one or more of doped or undoped zinc oxide, doped or undoped titanium dioxide, and doped or undoped tin dioxide, and the doping material includes one or more of magnesium, aluminum, and lithium;

[0064] The quantum dot light-emitting layer is formed on the electron injection layer or the electron transport layer, and a self-assembled insulating dielectric layer is formed at the interface between the quantum dot light-emitting layer and the electron injection layer or the electron transport layer.

[0065] The anode is formed on top of the quantum dot light-emitting layer.

[0066] Fifthly, this application also provides a display device, including a quantum dot light-emitting device as described in the third aspect of this application or a quantum dot light-emitting device fabricated by the method described in the fourth aspect of this application.

[0067] The quantum dot ink provided in this application contains polymer dopants, which exist in a dispersed form in the quantum dot ink. When a quantum dot light-emitting layer is formed using the above-mentioned quantum dot ink and a quantum dot light-emitting device is prepared, the efficiency of the quantum dot light-emitting device can be significantly improved. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the molecular structure of the hydrophobic polymer in some embodiments.

[0069] Figure 2 This is a schematic diagram of the structure of a quantum dot light-emitting device in some implementations.

[0070] Explanation of reference numerals in the attached figures:

[0071] 10: Hydrophobic polymer; 110: Non-conjugated polymer segment; 120: Second nonpolar hydrophobic segment; 130: Second polar group; 20: Quantum dot light-emitting device; 210: Substrate; 220: Cathode; 230: Electron transport layer; 240: Quantum dot light-emitting layer; 241: Self-assembled insulating layer; 250: Hole transport layer; 260: Hole injection layer; 270: Anode. Detailed Implementation

[0072] To facilitate understanding of the present invention, a more complete description of this application is provided below with reference to embodiments and accompanying drawings. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0074] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0075] In a first aspect, this application provides a quantum dot ink, comprising:

[0076] Organic solvents, hydrophobic quantum dot materials, and polymer dopants;

[0077] Hydrophobic quantum dot materials include quantum dots and hydrophobic ligands bound to the quantum dots, wherein the hydrophobic ligands include a first polar group;

[0078] The polymer dopant includes at least one hydrophobic polymer, the molecular structure of which includes a second polar group;

[0079] The binding affinity of the first polar group to the quantum dot is stronger than that of the second polar group to the quantum dot.

[0080] In some embodiments, the hydrophobic ligand includes a first nonpolar hydrophobic segment and a first polar group located at the end of the first nonpolar hydrophobic segment.

[0081] In some embodiments, the molecular structure of the hydrophobic polymer includes a main chain and side chains, the main chain including non-conjugated polymer segments, and the side chains including a second nonpolar hydrophobic segment and a second polar group located at the end of the second nonpolar hydrophobic segment.

[0082] Please see Figure 1 , Figure 1 The diagram shows a schematic of the structure of a hydrophobic polymer 10 in some embodiments, wherein the main chain includes a non-conjugated polymer chain segment 110, the side chain includes a second non-polar hydrophobic chain segment 120, and the end of the second non-polar hydrophobic chain segment 120 has a second polar group 130.

[0083] The quantum dot ink provided in this application contains polymer dopants, which exist in a dispersed form in the quantum dot ink. When a quantum dot light-emitting layer is formed using the above-mentioned quantum dot ink and a quantum dot light-emitting device is prepared, the efficiency of the quantum dot light-emitting device can be significantly improved.

[0084] In some embodiments, the non-conjugated polymer segments in the hydrophobic polymer contain at least two elements selected from hydrogen, carbon, nitrogen, sulfur, oxygen, silicon, and selenium. For example, the non-conjugated polymer segments are composed of both hydrogen and carbon.

[0085] In some embodiments, the second nonpolar hydrophobic segment in the hydrophobic polymer comprises an alkyl segment having 4 to 16 carbon atoms, or comprises a combined segment formed by linking an alkyl segment and a substituted or unsubstituted aryl segment, wherein the total number of carbon atoms in the combined segment is 7 to 16, and in the substituted or unsubstituted aryl segment, the substituent is an alkyl segment having 1 to 10 carbon atoms.

[0086] In some embodiments, the second polar group in the hydrophobic polymer includes one or more of phospho, amino, and phosphoxy groups.

[0087] In some embodiments, the molecular weight of the hydrophobic polymer is between 2 kDa and 200 kDa. It is understood that the molecular weight of the hydrophobic polymer can be, for example, but not limited to, 2 kDa, 10 kDa, 20 kDa, 50 kDa, 80 kDa, 100 kDa, 120 kDa, 150 kDa, 180 kDa, 200 kDa, etc. It is understood that the molecular weight of the hydrophobic polymer refers to the number-average molecular weight, obtained by gel permeation chromatography.

[0088] In some embodiments, the hydrophobic polymer exhibits no absorption in the wavelength range of 380 nm to 780 nm. The fact that the hydrophobic polymer does not absorb visible light prevents it from interfering with the normal emission of light from the emissive layer.

[0089] In some embodiments, the hydrophobic polymer comprises the structure shown in Formula I or Formula II:

[0090]

[0091] Where n1 and n2 represent the number of repeating units, 1≤n1≤1000, 1≤n2≤1000;

[0092] m1 represents an integer from 2 to 10, and m2 represents an integer from 2 to 10;

[0093] R is selected from H or CH3.

[0094] In some embodiments, the quantum dots have a core-shell structure. In the core-shell structure, the materials of the core layer and the shell layer are each independently selected from quantum dots of group II-VI compound semiconductors, group III-V compound semiconductors, group I-III-VI compound semiconductors, or perovskite quantum dots.

[0095] In some embodiments, the core layer material is selected from one or more of CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS, InP, InAs, InSb, GaAs, GaP, GaSb, HgTe, HgSe, HgS, CuInS, and CuInSe.

[0096] Furthermore, the core layer material is selected from one or more of CdSe and InP.

[0097] Furthermore, the shell material is selected from one or more of CdS, ZnSe, and ZnS.

[0098] In some embodiments, the first nonpolar hydrophobic segment of the hydrophobic ligand comprises aliphatic hydrocarbon or aryl nonpolar hydrophobic segments having 6 to 16 carbon atoms.

[0099] In some embodiments, the first polar group in the hydrophobic ligand includes one or more of carboxyl, mercapto, phosphin, and amino groups.

[0100] In this application, the binding ability of the first polar group to the quantum dot is stronger than that of the second polar group to the quantum dot. In some embodiments, the first polar group and the second polar group are selected as follows:

[0101] For example, if the first polar group includes a carboxyl or mercapto group, the second polar group may include one or more of a phosphino, amino, and phosphoxy group.

[0102] For example, if the first polar group includes a phosphine or an amino group, then the second polar group may include a phosphoxy group.

[0103] In some embodiments, the hydrophobic ligand includes one or more of oleylamine, 1-dodecylthiol, oleic acid, octylamine, and octylthiol.

[0104] In some embodiments, the mass content of the hydrophobic ligand in the hydrophobic quantum dot material is 8% to 30%.

[0105] In some embodiments, based on the total weight of the quantum dot ink, the mass content of the hydrophobic quantum dot material is 1% to 20%, and the mass content of the polymer dopant is 0.03% to 0.2%. It is understood that the mass content of the hydrophobic quantum dot material can be, for example, but not limited to, 1%, 3%, 4%, 5%, 6%, 8%, 10%, 12%, 14%, 15%, 17%, 19%, 20%, etc. It is understood that the mass content of the polymer dopant can be, for example, but not limited to, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, etc.

[0106] Furthermore, the mass ratio of hydrophobic quantum dot material to polymer dopant is (10–100):1. Understandably, the mass ratio of hydrophobic quantum dot material to polymer dopant can be, for example, but not limited to, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, etc.

[0107] In some embodiments, the organic solvent includes one or more of chain alkanes, cycloalkanes, haloalkanes, and aromatic compounds.

[0108] Furthermore, the organic solvent has a melting point ≥25℃ and a boiling point of 100℃~300℃.

[0109] Furthermore, the organic solvent includes one or more of xylene, phenylcyclohexane, and methyl benzoate.

[0110] In some embodiments, the viscosity of the quantum dot ink is 2.5 cP to 10 cP. It is understood that the viscosity of the quantum dot ink can be, for example, but not limited to, 2.5 cP, 4 cP, 5 cP, 7 cP, 8.5 cP, 10 cP, etc. It is understood that the viscosity of the quantum dot ink is obtained by measuring with a rotational viscometer.

[0111] In some embodiments, the surface tension of the quantum dot ink is between 28 mN / m and 42 mN / m. It is understood that the surface tension of the quantum dot ink can be, for example, but not limited to, 28 mN / m, 29 mN / m, 30 mN / m, 31 mN / m, 32 mN / m, 33 mN / m, 34 mN / m, 35 mN / m, 36 mN / m, 37 mN / m, 38 mN / m, 39 mN / m, 40 mN / m, 41 mN / m, 42 mN / m, etc. It is understood that the surface tension of the quantum dot ink is obtained by bubble-diffusing testing.

[0112] Secondly, this application provides a method for preparing quantum dot ink, comprising the following steps:

[0113] The organic solvent, hydrophobic quantum dot material, and polymer dopant are mixed.

[0114] The hydrophobic quantum dot material includes quantum dots and hydrophobic ligands bonded to the quantum dots, wherein the hydrophobic ligands include a first polar group; the polymer dopant includes at least one hydrophobic polymer, wherein the molecular structure of the hydrophobic polymer includes a second polar group; the binding ability of the first polar group to the quantum dots is stronger than the binding ability of the second polar group to the quantum dots.

[0115] In some embodiments, the preparation method of quantum dot ink includes the following steps:

[0116] The polymer dopant is mixed with the first organic solvent to form a polymer dopant preparative solution;

[0117] The hydrophobic quantum dot material is mixed with the second organic solvent to form a quantum dot pre-suspension;

[0118] Mix the polymer dopant preparation solution, the quantum dot preparation suspension, and the remaining organic solvent.

[0119] In some embodiments, the mass concentration of the polymer dopant in the polymer dopant preparation solution is 0.5% to 10%. It is understood that the mass concentration of the polymer dopant in the polymer dopant preparation solution can be, for example, but not limited to, 0.5%, 1.5%, 2%, 3.5%, 5%, 6.5%, 8%, 8.5%, 9%, 10%, etc.

[0120] In some embodiments, the mass concentration of the hydrophobic quantum dot material in the quantum dot preparation suspension is 1.4% to 40%. It is understood that the mass concentration of the hydrophobic quantum dot material in the quantum dot preparation suspension can be, for example, but not limited to, 1.4%, 5%, 8%, 10%, 15%, 18%, 20%, 24%, 26%, 28%, 30%, 32%, 34%, 38%, 40%, etc.

[0121] In some embodiments, the step of mixing the polymer dopant preparation solution, the quantum dot preparation suspension, and the remaining organic solvent includes:

[0122] The volume ratio of the polymer dopant preparation solution to the quantum dopant preparation suspension formed in any of the above embodiments is calculated based on the preset mass ratio of polymer dopant to hydrophobic quantum dot material.

[0123] The polymer dopant preparation solution and the quantum dot preparation suspension are mixed at the above volume ratio, and an appropriate amount of organic solvent is added according to the preset ink concentration. Understandably, the appropriate amount of organic solvent is the remaining organic solvent.

[0124] According to the method of this application, any mixing process can be carried out by means of stirring, oscillation and ultrasonic dispersion.

[0125] Understandably, during any mixing process, appropriate heating can be used to promote uniform mixing.

[0126] Understandably, any solution or suspension formed by a mixing process is characterized by clarity and homogeneity.

[0127] Understandably, the solution or suspension formed in any mixing process can be filtered to remove larger agglomerated particles before being used in subsequent processes. Further, for example, a polytetrafluoroethylene (PTFE) filter membrane with a pore size of 0.2–0.45 micrometers can be used for filtration.

[0128] The preparation method described in the second aspect of this application can prepare the quantum dot ink described in the first aspect of this application. Unless otherwise stated, the description of the polymer dopant, hydrophobic quantum dot material, and organic solvent in the second aspect of this application is as described in the first aspect of this application, and will not be repeated here.

[0129] Thirdly, this application provides a quantum dot light-emitting device, comprising:

[0130] The cathode and anode are arranged opposite each other; and

[0131] A quantum dot light-emitting layer located between the cathode and the anode is prepared using quantum dot ink from the first aspect of this application or quantum dot ink prepared using the method from the second aspect of this application.

[0132] The aforementioned quantum dot ink includes an organic solvent and hydrophobic quantum dots and polymer dopants dispersed in the organic solvent. The ink has suitable viscosity and surface tension, is easy to form a film, and the efficiency of the quantum dot light-emitting device can be significantly improved.

[0133] In some embodiments, the quantum dot light-emitting device further includes:

[0134] An electron injection layer and / or an electron transport layer are located between the cathode and the quantum dot light-emitting layer; the materials of the electron injection layer and the electron transport layer independently include one or more of doped or undoped zinc oxide, doped or undoped titanium dioxide, and doped or undoped tin dioxide, and the doping materials include one or more of magnesium, aluminum, and lithium.

[0135] The quantum dot luminescent layer has a self-assembled insulating dielectric layer formed at the interface with the electron injection layer and / or electron transport layer.

[0136] In this application, an electron injection layer and / or electron transport layer are disposed between the cathode and the quantum dot light-emitting layer in the quantum dot light-emitting device, which is more conducive to the transfer of electrons from the cathode to the quantum dot light-emitting layer. After the electron injection layer and / or electron transport layer are formed, the quantum dot light-emitting layer is fabricated using the quantum dot ink provided in this application. Since polymer dopants are dispersed in the quantum dot ink, the second polar groups of the polymer dopants have the ability to coordinate and bond with metal oxides such as zinc oxide, titanium oxide, and tin oxide, which are the materials used as the electron injection layer or electron transport layer. Therefore, through this coordination reaction, the polymer dopants can be attached to the surface of the electron injection layer or electron transport layer, which can passivate the surface defects of the metal oxide nanocrystals at the interface. Furthermore, the coordination reaction between the polymer dopant and metal oxides such as zinc oxide, titanium oxide, and tin oxide in the electron injection layer or electron transport layer produces a self-assembly effect, thereby forming a self-assembled monomolecular mesolayer at the interface between the quantum dot light-emitting layer and the electron injection layer or electron transport layer. Furthermore, the accumulation of nonpolar hydrophobic segments of the polymer dopant structure in the mesolayer makes the mesolayer insulating. Therefore, this monomolecular mesolayer can be called a self-assembled insulating mesolayer.

[0137] Previously, to address issues such as charge imbalance and exciton quenching, the conventional approach was to insert a thin, separately fabricated insulating layer between the electron injection layer and / or electron transport layer and the quantum dot emitting layer. However, the thickness of this traditional insulating layer significantly affects the electron density injected into the quantum dot emitting layer. Excessive thickness can even have a negative impact on the efficiency of the light-emitting device. Therefore, the thickness of the insulating layer plays a decisive role in device efficiency. This device structure requires extremely precise control over the insulating layer thickness, leading to significant limitations in device fabrication and a more complex manufacturing process.

[0138] In this application, during the process of coating quantum dot ink onto an electron injection layer or electron transport layer to form a quantum dot light-emitting layer, the second polar groups of the polymer dopant in the quantum dot ink coordinate with metal oxides such as zinc oxide, titanium oxide, and tin oxide in the electron injection layer or electron transport layer. This results in the formation of a self-assembled insulating dielectric layer at the interface between the quantum dot light-emitting layer and the electron injection layer or electron transport layer. This self-assembled insulating dielectric layer can suppress exciton quenching at the interface and weaken the electron injection effect, thereby improving the efficiency of the light-emitting device. Furthermore, the self-assembled insulating dielectric layer exhibits good film uniformity.

[0139] Uniformity is achieved, and the thickness can be controlled by adjusting the concentration of polymer dopants in the quantum dot ink and the coating volume. This allows for precise control of the thickness within a very thin range, minimizing the impact on device efficiency and simplifying the process.

[0140] It is simple to manufacture and has significant advantages in adjusting the charge balance in light-emitting devices, suppressing exciton quenching, and thus improving device efficiency.

[0141] In this application, the materials for the cathode and anode can be selected with reference to those used in existing electroluminescent devices.

[0142] In some embodiments, the cathode material includes one or more of ITO, IZO, and IGZO. In some embodiments, the anode material includes one or more of Ag, Mg, Au, and Al.

[0143] In some embodiments, the quantum dot light-emitting device further includes a hole transport layer and / or a hole injection layer sequentially stacked between the quantum dot light-emitting layer and the anode.

[0144] In this application, the materials of the hole transport layer and the hole injection layer can be referenced from those used in existing electroluminescent devices.

[0145] The selection is made accordingly. In some embodiments, the material of the hole transport layer includes one or more of TCTA, CPB, NPB, and 5TPD; the material of the hole injection layer includes MoO3, WO3, HATCN, and F4-TCNQ.

[0146] One or more of them.

[0147] In some implementations, the thickness of the assembled insulating layer is 1 nm to 3 nm.

[0148] In some implementations, the thickness of the quantum dot light-emitting layer is 10 nm to 50 nm.

[0149] In some embodiments, the thickness of the cathode is 20 nm to 200 nm.

[0150] In some embodiments, the thickness of the anode is 20 nm to 200 nm.

[0151] In some implementations, the thickness of the electron injection layer is 15 nm to 100 nm.

[0152] In some implementations, the thickness of the electron transport layer is 15 nm to 100 nm.

[0153] In some implementations, the thickness of the hole injection layer is 5 nm to 50 nm.

[0154] In some implementations, the thickness of the hole transport layer is 10 nm to 100 nm.

[0155] 5. In some embodiments, the quantum dot light-emitting device is an inverted electroluminescent device.

[0156] The quantum dot light-emitting device provided in this application can be either a top-emitting structure or a bottom-emitting structure.

[0157] In some implementations, such as Figure 2 As shown, the quantum dot light-emitting device 20 includes a cathode 220, an electron transport layer 230, a quantum dot light-emitting layer 240, a hole transport layer 250, a hole injection layer 260 and an anode 270 sequentially stacked on a substrate 210, wherein the quantum dot light-emitting layer 240 has a self-assembled insulating dielectric layer 241 formed at the interface with the electron transport layer 230.

[0158] Fourthly, this application provides a method for fabricating a quantum dot light-emitting device, comprising the following steps:

[0159] One of the cathode and anode is formed on the substrate;

[0160] Provide the quantum dot ink of the first aspect of this application or the quantum dot ink prepared by the method of the second aspect of this application, and use a solution method to fabricate a quantum dot light-emitting layer on the cathode or anode;

[0161] Another of the cathode and anode is formed on top of the quantum dot light-emitting layer.

[0162] In some embodiments, the fabrication method of a quantum dot light-emitting device includes the following steps:

[0163] A cathode is formed on the substrate;

[0164] An electron injection layer and / or an electron transport layer are formed on the cathode; the materials of the electron injection layer and the electron transport layer independently include one or more of doped or undoped zinc oxide, doped or undoped titanium dioxide and doped or undoped tin dioxide, and the doping materials include one or more of magnesium, aluminum and lithium.

[0165] A quantum dot light-emitting layer is formed on top of the electron injection layer or the electron transport layer, and a self-assembled insulating dielectric layer is formed at the interface between the quantum dot light-emitting layer and the electron injection layer or the electron transport layer.

[0166] An anode is formed on top of the quantum dot light-emitting layer.

[0167] In some embodiments, the method for fabricating a quantum dot light-emitting device further includes:

[0168] Prior to the anode formation step, a hole transport layer and / or a hole injection layer are formed on top of the quantum dot luminescent layer.

[0169] The aforementioned quantum dot ink contains polymer dopants. The binding affinity of the second polar group of the hydrophobic polymer in the polymer dopant to the quantum dots is weaker than or close to that of the first polar group in the original hydrophobic ligands of the quantum dots. Therefore, after the polymer dopant and the hydrophobic quantum dot material are mixed in a solvent, the polymer dopant will not undergo ligand exchange with the original hydrophobic ligands and will not alter the structure of the quantum dot material itself; it will only exist in a dispersed form in the ink. However, at the same time, the second polar group on the hydrophobic polymer molecular chain in the polymer dopant also has a certain ability to coordinate with metal oxides. Therefore, when the aforementioned quantum dot ink is used to form a quantum dot emitting layer on top of an electron injection layer or an electron transport layer using a solution method, in a wet film state, the second polar group of the hydrophobic polymer in the quantum dot ink will coordinate and bind with the metal oxides in the electron injection layer or electron transport layer and adhere to the surface of the electron injection layer or electron transport layer, resulting in self-assembly. This allows the quantum dot emitting layer to form a self-assembled insulating layer at the interface with the electron injection layer. The self-assembled insulating layer formed can passivate surface defects of metal oxide nanocrystals in the electron injection layer or electron transport layer, suppress exciton quenching at the interface, and reduce the effect of electron injection, thereby improving the efficiency of light-emitting devices.

[0170] In some implementations, such as Figure 2 As shown, the fabrication method of the quantum dot light-emitting device 20 includes the following steps:

[0171] A cathode 220 is formed on a substrate 210;

[0172] An electron transport layer 230 is formed on the cathode 220; the material of the electron transport layer includes one or more of doped or undoped zinc oxide, doped or undoped titanium dioxide, and doped or undoped tin dioxide, and the doping material includes one or more of magnesium, aluminum, and lithium.

[0173] A quantum dot light-emitting layer 240 is fabricated on the electron transport layer 230 using the quantum dot ink from the first aspect of this application or the quantum dot ink prepared according to the method in the second aspect of this application via a solution method.

[0174] A hole transport layer 250 is formed on top of the quantum dot light-emitting layer 240;

[0175] A hole injection layer 260 is formed on top of the hole transport layer 250;

[0176] An anode 270 is formed on top of the hole injection layer 260;

[0177] In this process, a self-assembled insulating dielectric layer 241 is formed at the interface between the quantum dot light-emitting layer 240 and the electron transport layer 230.

[0178] Understandably, solution coating refers to a method that uses ink to coat a wet film, then dries and heat-treats the wet film to form a functional layer film. In this application, the solution coating method can be, for example, but not limited to, spin coating, blade coating, and inkjet printing, etc.

[0179] In some embodiments, the steps of forming the electron injection layer and / or electron transport layer include: applying an electron injection layer or electron transport layer ink containing metal oxides onto the cathode by a solution method, followed by drying and annealing.

[0180] In some embodiments, the step of forming a quantum dot light-emitting layer over an electron injection layer or an electron transport layer includes:

[0181] Quantum dot ink is coated onto the electron injection layer or electron transport layer using a solution method to form a wet film. The film is then left to stand under normal pressure and then transferred to a reduced pressure environment to dry and form a thin film. Finally, the thin film is subjected to thermal annealing.

[0182] Furthermore, the standing time under normal pressure is 2 to 10 minutes.

[0183] Furthermore, the temperature for static placement under normal pressure is 10℃~35℃.

[0184] Furthermore, the conditions for hot annealing include a temperature of 50℃ to 120℃ and a time of 5 min to 30 min.

[0185] In this application, the method for forming the hole transport layer may include, but is not limited to, solution deposition or vacuum evaporation.

[0186] In this application, the method for forming the hole injection layer may include, but is not limited to, solution method or vacuum evaporation method.

[0187] In this application, the method for forming the anode may include, but is not limited to, vacuum evaporation or sputtering.

[0188] The fabrication method described in the fourth aspect of this application can be used to prepare the quantum dot light-emitting device described in the third aspect of this application. Unless otherwise stated, the descriptions of the materials of each functional layer are as described above.

[0189] Fifthly, this application also provides a display device, including a quantum dot light-emitting device as described in the third aspect of this application or a quantum dot light-emitting device fabricated by the method described in the fourth aspect of this application.

[0190] In this application, the display device may include, but is not limited to, any display screen with a device such as a mobile phone, tablet, computer, or television.

[0191] The following are specific examples.

[0192] Example 1

[0193] 1. Preparation of polymer dopants

[0194] The polymer dopant is a hydrophobic polymer P1 with the following structure:

[0195] Where n represents the number of repeating units in the polymer backbone.

[0196] The synthesis method of P1 is as follows:

[0197]

[0198] First, diethylphenylphosphine oxide (3 mmol, 546 mg) was dissolved in dry 1,4-dioxane (20 mL) under argon protection. A paraffin dispersion of Na (10 mmol, 10 mol / L, 1.0 mL) was then added using a syringe. The mixture was stirred at 60 °C for 24 h. Excess Na was removed by filtration, and then 1,6-dibromohexane (10 mmol, 1.62 mL) was added. Stirring continued at room temperature for 0.5 h. The reactants were filtered and concentrated under reduced pressure. Impurities were eluted with hexane using a silica gel column, followed by elution with methanol to obtain the crude product. Finally, the intermediate product M1386 mg (48% yield) was obtained by gel permeation chromatography (GPC) using chloroform as the solvent. 1 HNMR(400MHz, CDCl3): δ3.50(t,2H),1.97-1.76(m,2H),

[0199] 1.63-1.50(m,6H),1.44-1.17(m,6H),1.10-0.94(m,6H). 31 P NMR (162MHz, CDCl3): δ48.6.

[0200] Under argon protection, M1 (1 mmol, 268 mg), CuCl2 (0.03 mmol, 3 mol%, 4 mg), and benzonitrile (0.1 mmol, 10 mol%, 10.3 mg) were dissolved in dry tetrahydrofuran (1 mL). A tetrahydrofuran solution of 4-vinylphenyl magnesium bromide (1.2 mmol, 12 mol / L, 1.0 mL) was added dropwise to the reaction vessel over 5 minutes. After the addition was complete, the temperature was raised to 50 °C, and the reaction was stirred for 3 h. The reaction was then terminated with 1 N HCl aqueous solution (2.0 mL). The aqueous phase was extracted three times with diethyl ether, and the organic phases were combined, dried over MgSO4, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography to give monomer M2 239 mg, with a yield of 82%. 1HNMR(400MHz, CDCl3): δ7.60-7.48(m,2H),6.82-6.60(m,3H),5.63(m,1H),5.32(m,1H), 2.81(t,2H),1.80-1.67(m,2H),1.62-1.48(m,6H),1.37-1.15(m,6H),1.10-0.94(m,6H). 31 P NMR (162MHz, CDCl3): δ46.5.

[0201] Monomer M2 (0.3 mmol, 88 mg) was dissolved in dry toluene (10 mL) under argon protection, and 2,2'-azobisisobutyronitrile (AIBN) initiator (0.03 mmol, 4.9 mg) was added with stirring. Polymerization was initiated at 65 °C and terminated by adding ethanol after 24 h at room temperature. The reaction mixture was decanted into a large volume of ethanol solution to precipitate the polymer. The precipitate was collected and washed repeatedly with ethanol, and finally dried under vacuum to obtain 76 mg of polymer dopant P1, with a yield of 86%. Elemental analysis showed C 73.52, H 10.38, O 5.40, P 10.44. The number-average molecular weight was 20 kDa as determined by gel permeation chromatography.

[0202] 2. Preparation of hydrophobic quantum dot materials:

[0203] The red hydrophobic quantum dot material, consisting of an InP core, a ZnS shell, and an oleic acid ligand, was synthesized by the following method:

[0204] In(OAc)3 (1 mmol, 292 mg) and oleic acid (3 mmol, 847 mg) were dissolved in 1-octadecene (20 mL) and dried under vacuum at 120 °C for 1 h. Under argon protection, the temperature was raised to 280 °C, and a mixture of tris(trimethylsilyl)phosphine (TMS3P) (0.75 mmol, 236 mg) and tri-n-octylphosphine (TOP) (2 mL) was rapidly added. The reaction was continued for 20 min to form InP nanocrystals. The reactants were cooled to room temperature and precipitated in a large amount of acetone. After centrifugation, the supernatant was removed, and the precipitated InP was dispersed in toluene (10 mL).

[0205] Zn(OAc)₂ (1 mmol, 220 mg) and oleic acid (3 mmol, 847 mg) were dissolved in trioctylamine (15 mL) and dried under vacuum at 120 °C for 1 h. Under argon protection, the temperature was raised to 280 °C, and the above-mentioned InP toluene dispersion and dodecyl mercaptan (6 mmol, 1.21 g) were added. Stirring continued for 1 h to form InP / ZnS nanocrystals. After the reaction was complete, the reactants were cooled to room temperature, and a large amount of ethanol was added to precipitate the product. After centrifugation, the supernatant was removed, and the precipitate was dispersed in a small amount of toluene. The toluene dispersion was poured into a large amount of ethyl acetate for further precipitation. After centrifugation, the supernatant was removed, and the precipitate was vacuum dried and weighed to obtain 122 mg of InP / ZnS quantum dots with oleic acid ligands. The dried quantum dot solids were immediately used for ink preparation.

[0206] 3. Preparation of quantum dot ink

[0207] Formulation: By weight percentage, it comprises a mixed organic solvent consisting of 78.5% xylene and 20% phenylcyclohexane, 1.47% red hydrophobic quantum dot material, and 0.03% polymer dopant.

[0208] Preparation steps:

[0209] 1) Mix xylene and phenylcyclohexane (mass ratio 78.5:20) to obtain a mixed organic solvent;

[0210] 2) The polymer dopant is mixed with a portion of the mixed organic solvent to form a polymer dopant preparative solution; in the polymer dopant preparative solution, the mass concentration of the polymer dopant is 1%;

[0211] 3) The red hydrophobic quantum dot material was mixed with another part of the mixed organic solvent to form a quantum dot pre-suspension; the mass concentration of the red hydrophobic quantum dot material in the quantum dot pre-suspension was 3%;

[0212] 4) The polymer dopant preparation solution, quantum dot preparation suspension and mixed organic solvent are mixed in a mass ratio of 3:49:48 to form quantum dot ink.

[0213] 4. Fabrication of quantum dot light-emitting devices:

[0214] An electron transport layer with a thickness of 40 nm made of zinc oxide nanocrystals is formed by spin coating on a substrate with an ITO cathode with a thickness of 50 nm attached.

[0215] The quantum dot ink prepared in step 3 was spin-coated onto the electron transport layer to obtain a quantum dot wet film. The quantum dot wet film was placed at 25°C and normal pressure for 2 min, then placed at 10°C and 100 Pa for 10 min to dry it. Finally, it was thermally annealed at 100°C for 5 min to form a quantum dot light-emitting layer with a thickness of 25 nm.

[0216] A hole transport layer with a thickness of 30 nm made of TCTA is formed on top of the quantum dot light-emitting layer by vapor deposition.

[0217] A hole injection layer with a thickness of 10 nm made of MoO3 is formed on the hole transport layer by vapor deposition.

[0218] An anode with a thickness of 100 nm made of Ag is formed by vapor deposition on top of the hole injection layer.

[0219] Example 2

[0220] 1. Preparation of polymer dopants:

[0221] The polymer dopant is a hydrophobic polymer P2 with the following structure:

[0222]

[0223] Where n represents the number of repeating units in the polymer backbone.

[0224] The synthesis method of P2 is as follows:

[0225]

[0226] The structure of Boc is as follows:

[0227] First, the amino groups in the monomer M3 were protected. Monomer M3 (5 mmol, 1.067 g) was dissolved in THF (30 mL), and NaHCO3 (15 mmol, 1.35 g) and di-tert-butyl carbonate (Boc2O, 6 mmol, 1.31 g) were added in a single batch at 0 °C. The reaction mixture was stirred at 0 °C for 30 min, then brought to room temperature and stirred overnight. The resulting mixture was extracted three times with diethyl ether, and the combined organic phase solutions were dried over Na2SO4. After concentration under reduced pressure, recrystallization in a mixed solution of dichloromethane and ethanol yielded 1.14 g of amino-protected monomer M4, with a yield of 73%. 1HNMR(400MHz, CDCl3): δ 6.73(m,1H),6.41-6.23(m,2H),4.02(t,2H),3.24(t,2H), 2.03(s,3H),1.65-1.52(m, 4H), 1.47-1.22 (m,17H).

[0228] Monomer M4 (1 mmol, 313 mg) was dissolved in dry toluene (30 mL) under argon protection, and 2,2'-azobisisobutyronitrile (AIBN) initiator (0.1 mmol, 16.4 mg) was added with stirring. Polymerization was initiated at 65 °C and terminated by adding ethanol after 24 h at room temperature. The reaction mixture was decanted into a large volume of ethanol solution to precipitate the polymer. The precipitate was collected and washed repeatedly with ethanol, and finally dried under vacuum to obtain 260 mg of polymer precursor P0, with a yield of 82%. Elemental analysis showed C 64.81, H 10.44, N 4.46, O 20.32. Gel permeation chromatography determined the number-average molecular weight to be 15 kDa.

[0229] The polymer precursor P0 (0.5 mmol repeating unit, 156 mg) was dissolved in dry dichloromethane (1.0 mL), and trifluoroacetic acid (1.0 mL) was added. The mixture was stirred at room temperature for 1 h. The solvent and excess reactants were removed under reduced pressure, and the mixture was extracted with dichloromethane and saturated NaHCO3 solution. The organic phases were combined and concentrated under reduced pressure. The concentrated solution was poured into a large volume of ethanol solution to precipitate the product. The precipitate was collected and washed repeatedly with ethanol. Finally, it was dried under vacuum to obtain 98 mg of polymer dopant P2, with a yield of 93%. Elemental analysis showed C 66.95, H 11.66, N 6.49, O 14.90. The number-average molecular weight was 10 kDa as determined by gel permeation chromatography.

[0230] 2. Preparation of hydrophobic quantum dot materials:

[0231] Green hydrophobic quantum dot materials, consisting of a CdSe core, a ZnSe / ZnS bilayer shell, and a 1-dodecylthiol ligand, were synthesized by the following method:

[0232] First, tri-n-octylphosphine oxide (TOPO) (15 mL) was vacuum dried at 180 °C for 1 h, and then cooled to 120 °C. Under argon protection, a Se-based tri-n-octylphosphine TOP preparative solution (1 mmol / mL, 2 mL) was added, and the temperature was raised to 300 °C. Then, a Cd(OAc)₂ TOP preparative solution (0.2 mmol / mL, 2.5 mL) was rapidly added with rapid stirring. The reaction was then continued at 260 °C for 1 h to form CdSe nanocrystals.

[0233] The temperature of the above reactants was adjusted to 180℃, and a Zn(OAc)2 TOP preparative solution (0.4 mmol, 5 mL, vacuum dried at 130℃ for 1 h) was added dropwise over a 30-minute period with rapid stirring. Stirring was then continued for 1 h to form CdSe / ZnSe nanocrystals.

[0234] The temperature of the above reactants was adjusted to 90℃, and a TOP preparative solution of Zn(OAc)2 (0.4 mmol, 5 mL, vacuum dried at 130℃ for 1 h) was added. The temperature was raised to 180℃, and H2S (10 mL) was slowly added dropwise with rapid stirring, followed by continued stirring for 1 h to form CdSe / ZnSe / ZnS nanocrystals. After the reaction was complete, the temperature was lowered to 90℃, 15 mL of chloroform was added, and the mixture was poured into a large amount of methanol for precipitation. After centrifugation, the supernatant was removed, and the precipitate was dissolved in 15 mL of chloroform and poured into a large amount of ethyl acetate for further precipitation. After centrifugation, the supernatant was removed, and the precipitate of CdSe / ZnSe / ZnS quantum dots was dissolved in 15 mL of chloroform.

[0235] Finally, ligand exchange was performed on the quantum dots. 1-Dodecylthiol (5 mL) was added to a chloroform solution of CdSe / ZnSe / ZnS quantum dots, and the mixture was stirred at 50 °C for 24 h. The mixture was purified by precipitation twice in methanol, and the final precipitate was dried under vacuum and weighed to obtain 110 mg of CdSe / ZnSe / ZnS quantum dots with 1-dodecylthiol ligands. The dried quantum dot solid was immediately used for ink preparation.

[0236] 3. Preparation of quantum dot ink:

[0237] Formulation: By weight percentage, it comprises a mixed organic solvent consisting of 67% phenylcyclohexane and 30% methyl benzoate, 2.95% green hydrophobic quantum dot material, and 0.05% polymer dopant. Preparation steps:

[0238] 1) Mix phenylcyclohexane and methyl benzoate (mass ratio 67:30) to obtain a mixed organic solvent;

[0239] 2) The polymer dopant is mixed with a portion of the mixed organic solvent to form a polymer dopant preparative solution; in the polymer dopant preparative solution, the mass concentration of the polymer dopant is 2%;

[0240] 3) The green hydrophobic quantum dot material is mixed with another part of the mixed organic solvent to form a quantum dot pre-suspension; the mass concentration of the green hydrophobic quantum dot material in the quantum dot pre-suspension is 5%;

[0241] 4) The polymer dopant preparation solution, quantum dot preparation suspension and mixed organic solvent are mixed in a mass ratio of 2.5:59:38.5 to form quantum dot ink.

[0242] 4. Fabrication of quantum dot light-emitting devices:

[0243] An electron transport layer with a thickness of 40 nm made of zinc oxide nanocrystals is formed on a substrate with a cathode of 50 nm thickness attached by inkjet printing.

[0244] The quantum dot ink prepared in step 3 was used to inkjet print on the electron transport layer to obtain a quantum dot wet film. The quantum dot wet film was placed at 25°C and normal pressure for 5 min, then placed at 10°C and 1 Pa for 15 min to dry it. Finally, it was thermally annealed at 100°C for 10 min to form a quantum dot light-emitting layer with a thickness of 25 nm.

[0245] A hole transport layer with a thickness of 30 nm made of TCTA is formed on the quantum dot light-emitting layer by vapor deposition.

[0246] A hole injection layer with a thickness of 10 nm made of MoO3 is formed on the hole transport layer by vapor deposition.

[0247] An anode with a thickness of 100 nm made of Ag is formed by vapor deposition on top of the hole injection layer.

[0248] Example 3

[0249] 1. Preparation of polymer dopants:

[0250] Same as step 1 in Example 2.

[0251] 2. Preparation of hydrophobic quantum dot materials:

[0252] Same as step 2 in Example 2.

[0253] 3. Preparation of quantum dot ink:

[0254] Formulation: By weight percentage, it comprises a mixed organic solvent consisting of 67% phenylcyclohexane and 30% methyl benzoate, 2.8% green hydrophobic quantum dot material, and 0.2% polymer dopant.

[0255] Preparation steps:

[0256] 1) Mix phenylcyclohexane and methyl benzoate (mass ratio 67:30) to obtain a mixed organic solvent;

[0257] 2) The polymer dopant is mixed with a portion of the mixed organic solvent to form a polymer dopant preparative solution; in the polymer dopant preparative solution, the mass concentration of the polymer dopant is 2%;

[0258] 3) The green hydrophobic quantum dot material is mixed with another part of the mixed organic solvent to form a quantum dot pre-suspension; the mass concentration of the green hydrophobic quantum dot material in the quantum dot pre-suspension is 5%;

[0259] 4) The polymer dopant preparation solution, quantum dot preparation suspension and mixed organic solvent are mixed in a mass ratio of 10:56:34 to form quantum dot ink.

[0260] 4. Fabrication of quantum dot light-emitting devices:

[0261] Same as step 4 in Example 2.

[0262] Comparative Example 1

[0263] 1. Preparation of hydrophobic quantum dot materials:

[0264] Same as step 2 in Example 1.

[0265] 2. Preparation of quantum dot ink

[0266] Formulation: By mass percentage, it comprises a mixed organic solvent consisting of 78.5% xylene and 20% phenylcyclohexane, and 1.5% red hydrophobic quantum dot material. Preparation steps:

[0267] 1) Mix xylene and phenylcyclohexane (mass ratio 78.5:20) to obtain a mixed organic solvent;

[0268] 2) The red hydrophobic quantum dot material is mixed with a mixed organic solvent to form an ink; the mass concentration of the red hydrophobic quantum dot material in the ink is 1.5%.

[0269] 3. Fabrication of quantum dot light-emitting devices:

[0270] An electron transport layer with a thickness of 40 nm made of zinc oxide nanocrystals is formed by spin coating on a substrate with a cathode of 50 nm thickness attached to it.

[0271] The quantum dot ink prepared in step 2 was spin-coated onto the electron transport layer to obtain a quantum dot wet film. The quantum dot wet film was placed at 25°C and normal pressure for 2 min, then placed at 10°C and 100 Pa for 10 min to dry it. Finally, it was thermally annealed at 100°C for 5 min to form a quantum dot light-emitting layer with a thickness of 25 nm.

[0272] A hole transport layer with a thickness of 30 nm made of TCTA is formed on the quantum dot light-emitting layer by vapor deposition.

[0273] A hole injection layer with a thickness of 10 nm made of MoO3 is formed on the hole transport layer by vapor deposition.

[0274] An anode with a thickness of 100 nm made of Ag is formed by vapor deposition on top of the hole injection layer.

[0275] Comparative Example 2

[0276] 1. Preparation of hydrophobic quantum dot materials:

[0277] Same as step 2 in Example 2.

[0278] 2. Preparation of quantum dot ink:

[0279] Formulation: By weight percentage, it comprises a mixed organic solvent consisting of 67% phenylcyclohexane and 30% methyl benzoate, and 3% green hydrophobic quantum dot material.

[0280] Preparation steps:

[0281] 1) Mix phenylcyclohexane and methyl benzoate (mass ratio 67:30) to obtain a mixed organic solvent;

[0282] 2) The green hydrophobic quantum dot material is mixed with a mixed organic solvent to form an ink; the mass concentration of the green hydrophobic quantum dot material in the ink is 3%.

[0283] 3. Fabrication of quantum dot light-emitting devices:

[0284] An electron transport layer with a thickness of 40 nm made of zinc oxide nanocrystals is formed on a substrate with a cathode of 50 nm thickness attached by inkjet printing.

[0285] The quantum dot ink prepared in step 2 was used to inkjet print on the electron transport layer to obtain a quantum dot wet film. The quantum dot wet film was placed at 25°C and normal pressure for 5 min, then placed at 10°C and 1 Pa for 15 min to dry it. Finally, it was thermally annealed at 100°C for 10 min to form a quantum dot light-emitting layer with a thickness of 25 nm.

[0286] A hole transport layer with a thickness of 30 nm made of TCTA is formed on the quantum dot light-emitting layer by vapor deposition.

[0287] A hole injection layer with a thickness of 10 nm made of MoO3 is formed on the hole transport layer by vapor deposition.

[0288] An anode with a thickness of 100 nm made of Ag is formed by vapor deposition on top of the hole injection layer.

[0289] The viscosity and surface tension of the quantum dot inks prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested at 25°C. The maximum external quantum efficiency of the quantum dot light-emitting devices prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested using the integrating sphere method. The test results are shown in Table 1 below.

[0290] Table 1 Performance test results of quantum dot ink and light-emitting devices

[0291]

[0292] As can be seen from Table 1, the quantum dot inks prepared in Examples 1 to 3 have suitable viscosity and surface tension, and have good film-forming properties.

[0293] Compared to Comparative Example 1, the light-emitting device prepared in Example 1 has a higher maximum external quantum efficiency. Similarly, compared to Comparative Example 2, the light-emitting devices prepared in Examples 2 and 3 have higher maximum external quantum efficiencies. This demonstrates that the light-emitting device prepared using quantum dot ink containing polymer dopants as the quantum dot emitting layer exhibits higher efficiency. This is because the quantum dot ink can self-assemble with zinc oxide in the underlying electron transport layer, forming a thin self-assembled insulating layer between the electron transport layer and the quantum dot emitting layer. This self-assembled insulating layer can suppress exciton quenching at the interface between the electron transport layer and the quantum dot emitting layer, thereby increasing the quantum yield of exciton radiative transitions. Simultaneously, this self-assembled insulating layer can also reduce electron injection into the quantum dot emitting layer, promoting charge balance within the light-emitting device and improving its efficiency.

[0294] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0295] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A quantum dot light-emitting device, characterized in that, include: The cathode and anode are positioned opposite each other; as well as A quantum dot light-emitting layer located between the cathode and the anode, the quantum dot light-emitting layer being located between the cathode and the anode, the quantum dot light-emitting layer being fabricated using quantum dot ink; An electron injection layer and / or an electron transport layer located between the cathode and the quantum dot light-emitting layer; At least one of the electron injection layer and the electron transport layer comprises a metal oxide; The quantum dot light-emitting layer has a self-assembled insulating dielectric layer formed at the interface with the electron injection layer and / or the electron transport layer; The quantum dot ink comprises: an organic solvent, a hydrophobic quantum dot material, and a polymer dopant; The hydrophobic quantum dot material includes quantum dots and hydrophobic ligands bound to the quantum dots. The hydrophobic ligands include a first nonpolar hydrophobic segment and a first polar group located at the end of the first nonpolar hydrophobic segment. The first polar group includes one or more of carboxyl, mercapto, phosphin, and amine groups. The quantum dot has a core-shell structure; in the core-shell structure, the materials of the core layer and the shell layer are each independently selected from quantum dots of group II-VI compound semiconductors, quantum dots of group III-V compound semiconductors, quantum dots of group I-III-VI compound semiconductors, or perovskite quantum dots; the material of the core layer is selected from one or more of CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS, InP, InAs, InSb, GaAs, GaP, GaSb, HgTe, HgSe, HgS, CuInS, and CuInSe. The polymer dopant includes at least one hydrophobic polymer, the molecular structure of which includes a main chain and side chains. The main chain includes non-conjugated polymer segments, and the side chains include a second nonpolar hydrophobic segment and a second polar group located at the end of the second nonpolar hydrophobic segment. The second polar group includes one or more of phosphin, amino, and phosphoroxy groups. The hydrophobic polymer has no absorption in the wavelength range of 380 nm to 780 nm. The binding affinity of the first polar group to the quantum dot is stronger than that of the second polar group to the quantum dot. The mass ratio of the hydrophobic quantum dot material to the polymer dopant is (10~100):

1.

2. The quantum dot light-emitting device according to claim 1, characterized in that, The non-conjugated polymer segments contain at least two elements selected from hydrogen, carbon, nitrogen, sulfur, oxygen, silicon, and selenium; and / or The second nonpolar hydrophobic segment comprises an alkyl segment having 4 to 16 carbon atoms, or a combined segment formed by linking an alkyl segment and a substituted or unsubstituted aryl segment, wherein the total number of carbon atoms in the combined segment is 7 to 16, and in the substituted or unsubstituted aryl segment, the substituent is an alkyl segment having 1 to 10 carbon atoms; and / or The hydrophobic polymer has a molecular weight of 2kDa to 200kDa.

3. The quantum dot light-emitting device according to claim 1 or 2, characterized in that, The hydrophobic polymer comprises the structure shown in Formula I or Formula II: Formula I Formula II Where n1 and n2 represent the number of repeating units, 1≤n1≤1000, 1≤n2≤1000; m1 represents an integer from 2 to 10, and m2 represents an integer from 2 to 10; R is selected from H or CH3.

4. The quantum dot light-emitting device according to claim 1, characterized in that, The first nonpolar hydrophobic segment includes nonpolar hydrophobic segments of aliphatic hydrocarbon groups or aryl groups with 6 to 16 carbon atoms.

5. The quantum dot light-emitting device according to claim 4, characterized in that, The core layer material is selected from one or more of CdSe and InP; and / or The shell material is selected from one or more of CdS, ZnSe, and ZnS; and / or The hydrophobic ligands include one or more of oleylamine, 1-dodecylthiol, oleic acid, octylamine, and octylthiol.

6. The quantum dot light-emitting device according to any one of claims 1-2 and 4-5, characterized in that, In the hydrophobic quantum dot material, the mass content of the hydrophobic ligand is 8%~30%; and / or Based on the total weight of the quantum dot ink, the hydrophobic quantum dot material has a mass content of 1% to 20%, and the polymer dopant has a mass content of 0.03% to 0.2%; and / or The organic solvent includes one or more of chain alkanes, cycloalkanes, haloalkanes, and aromatic compounds; and / or The organic solvent has a melting point ≥25℃ and a boiling point of 100℃~300℃; and / or The viscosity of the quantum dot ink is 2.5 cP to 10 cP; and / or The surface tension of the quantum dot ink is 28 mN / m to 42 mN / m.

7. The quantum dot light-emitting device according to claim 1, characterized in that, The materials of the electron injection layer and the electron transport layer independently include one or more of doped or undoped zinc oxide, doped or undoped titanium dioxide, and doped or undoped tin dioxide, and the doping materials include one or more of magnesium, aluminum, and lithium.

8. The quantum dot light-emitting device according to any one of claims 1-2, 4-5 and 7, characterized in that, The cathode material includes one or more of ITO, IZO, and IGZO; and / or The anode material includes one or more of Ag, Mg, Au, and Al; and / or The quantum dot light-emitting device further includes: a hole transport layer and / or a hole injection layer sequentially stacked between the quantum dot light-emitting layer and the anode; the material of the hole transport layer includes one or more of TCTA, CPB, NPB, and TPD; the material of the hole injection layer includes one or more of MoO3, WO3, HATCN, and F4-TCNQ.

9. A method for fabricating a quantum dot light-emitting device, characterized in that, Includes the following steps: A cathode is formed on the substrate; An electron injection layer and / or an electron transport layer are formed on the cathode; at least one of the electron injection layer and the electron transport layer comprises a metal oxide; A quantum dot ink is provided, in which a quantum dot luminescent layer is formed on the electron injection layer or electron transport layer using a solution method, wherein the quantum dot luminescent layer forms a self-assembled insulating dielectric layer at the interface with the electron injection layer or electron transport layer. An anode is formed on the quantum dot light-emitting layer; The quantum dot ink is prepared using the following steps: The organic solvent, hydrophobic quantum dot material, and polymer dopant are mixed. The hydrophobic quantum dot material includes quantum dots and hydrophobic ligands bound to the quantum dots. The hydrophobic ligands include a first nonpolar hydrophobic segment and a first polar group located at the end of the first nonpolar hydrophobic segment. The first polar group includes one or more of carboxyl, thiol, phosphine, and amine groups. The quantum dot has a core-shell structure; in the core-shell structure, the materials of the core layer and the shell layer are each independently selected from quantum dots of group II-VI compound semiconductors, quantum dots of group III-V compound semiconductors, quantum dots of group I-III-VI compound semiconductors, or perovskite quantum dots; the material of the core layer is selected from one or more of CdTe, CdSe, CdS, ZnTe, ZnSe, ZnS, InP, InAs, InSb, GaAs, GaP, GaSb, HgTe, HgSe, HgS, CuInS, and CuInSe. The polymer dopant includes at least one hydrophobic polymer, the molecular structure of which includes a main chain and side chains. The main chain includes non-conjugated polymer segments, and the side chains include a second nonpolar hydrophobic segment and a second polar group located at the end of the second nonpolar hydrophobic segment. The second polar group includes one or more of phosphin, amino, and phosphoroxy groups. The hydrophobic polymer has no absorption in the wavelength range of 380 nm to 780 nm. The binding affinity of the first polar group to the quantum dot is stronger than that of the second polar group to the quantum dot. The mass ratio of the hydrophobic quantum dot material to the polymer dopant is (10~100):

1.

10. The method for fabricating a quantum dot light-emitting device according to claim 9, characterized in that, Includes the following steps: The polymer dopant is mixed with the organic solvent in the first part to form a polymer dopant preparative solution; The hydrophobic quantum dot material is mixed with the organic solvent described in the second part to form a quantum dot pre-suspension; The polymer dopant preparation solution, the quantum dot preparation suspension, and the remaining portion of the organic solvent are mixed.

11. The method for fabricating a quantum dot light-emitting device according to claim 10, characterized in that, In the polymer dopant preparation solution, the mass concentration of the polymer dopant is 0.5% to 10%; and / or In the quantum dot pre-suspension, the mass concentration of the hydrophobic quantum dot material is 1.4% to 40%.

12. A display device, characterized in that, This includes the quantum dot light-emitting device as described in any one of claims 1 to 8 or the quantum dot light-emitting device prepared by the method described in any one of claims 9 to 11.

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