Quantum dot light-emitting device and display panel comprising same

Abstract

The invention provides a quantum dot light-emitting device and a display panel comprising the same. The quantum dot light-emitting device comprises a substrate with a first electrode layer, and a red quantum dot layer array, a green quantum dot layer array and a blue quantum dot layer array which are arranged on the first electrode layer at intervals, and further comprises a protective quantum dot layer which comprises a first part and a second part, the first part is located on the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array, and the second part is located among the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array, so that no gap exists between the quantum dot layer arrays; the band gap width of the protective quantum dots in the protective quantum dot layer is greater than that of the blue quantum dots in the blue quantum dot layer array; the quantum dot light-emitting device further comprises a second electrode layer. According to the quantum dot light-emitting device, the protective quantum dot layer is provided, the problem of current leakage basically does not exist, the quantum dots in the protective quantum dot layer do not emit light under the power-on condition, and the final light-emitting spectrum is not affected.

Description

Technical Field

[0001] The present disclosure relates to the technical field of quantum dot synthesis, and in particular to a quantum dot light-emitting device and a display panel containing the same. Background Art

[0002] Quantum dot light-emitting diodes (QLEDs) are known as the next generation of new display technology due to their advantages such as high color purity, low power consumption and simple process. At present, there are two main QLED preparation processes: printed QLED and photolithography QLED. Compared with printed QLED, the resolution of photolithography QLED can reach more than 4000PPi, so its application field is wider, including mobile phones / micro displays (VR&AR), etc.

[0003] The most widely used method for photolithography QLED is the photocross-linking of quantum dot ligands. However, after the preparation of the quantum dot layer is completed by photolithography, the gaps between different quantum dot layers are filled by the electron transport layer and then directly contacted with the hole transport layer, resulting in a very large leakage current of the QLED device. Summary of the invention

[0004] The purpose of the present disclosure is to provide a quantum dot light-emitting device and a display panel containing the same, so as to solve the leakage current problem of photolithography QLED devices.

[0005] According to a first aspect of the present disclosure, a quantum dot light-emitting device is provided, which includes a substrate having a first electrode layer, a red quantum dot layer array, a green quantum dot layer array and a blue quantum dot layer array arranged at intervals on the first electrode layer, the quantum dot light-emitting device also includes a protective quantum dot layer, the protective quantum dot layer includes a first part and a second part, the first part is located above the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array, and the second part is located between the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array so that there is no gap between the quantum dot layer arrays, and the band gap width of the protective quantum dots in the protective quantum dot layer is greater than the band gap width of the blue quantum dots in the blue quantum dot layer array; the quantum dot light-emitting device also includes a second electrode layer.

[0006] Optionally, the thickness of the protective quantum dot layer of the first portion is 5-200 nm, and the thickness of the protective quantum dot layer of the second portion is 5-200 nm.

[0007] Optionally, a hole functional layer is disposed on the first electrode layer, and a red quantum dot layer array, a green quantum dot layer array and a blue quantum dot layer array are disposed on the hole functional layer.

[0008] Optionally, an electronic functional layer is disposed on the protective quantum dot layer, and the thickness of the electronic functional layer is greater than the thickness of the protective quantum dot layer.

[0009] Optionally, the spacing distance between each quantum dot layer array is 1-5 microns.

[0010] Optionally, the preparation method of the quantum dot light-emitting device includes: providing a substrate having a first electrode layer, setting a first quantum dot solution on the exposed surface of the substrate, the first quantum dot solution containing a photoinitiator; drying the solvent in the first quantum dot solution to obtain a first quantum dot layer, setting a first mask template above the substrate, exposing the first quantum dot layer and then developing it, cross-linking each first quantum dot to obtain a first quantum dot layer array; setting a second quantum dot solution on the exposed surface of the substrate, the second quantum dot solution containing a photoinitiator, drying the solvent in the second quantum dot solution to obtain a second quantum dot layer, setting a second mask template above the substrate, exposing the second quantum dot layer and then developing it, cross-linking each second quantum dot to obtain a second quantum dot layer array; setting a third quantum dot solution on the exposed surface of the substrate, the third quantum dot solution containing a photoinitiator An initiator is used to dry the solvent in the third quantum dot solution to obtain a third quantum dot layer, a third mask is set above the substrate, the third quantum dot layer is exposed and then developed, and each third quantum dot is cross-linked to obtain a third quantum dot layer array; there is a gap between the first quantum dot layer array, the second quantum dot layer array, and the third quantum dot layer array; the first quantum dot layer array, the second quantum dot layer array, and the third quantum dot layer array are non-repeatedly selected from a red quantum dot layer array, a green quantum dot layer array, and a blue quantum dot layer array; a protective quantum dot solution is set on the exposed surface of the substrate and dried to obtain a protective quantum dot layer; or a protective quantum dot solution is set on the exposed surface of the substrate and dried, and the wet film layer formed by the protective quantum dot solution is exposed and developed, so that each protective quantum dot is cross-linked to obtain a protective quantum dot layer.

[0011] Optionally, the preparation method of the quantum dot light-emitting device includes: providing a substrate having a first electrode layer, setting a first quantum dot solution on the substrate, the first quantum dot solution containing a photoinitiator; setting a first mask above the substrate to dry the solvent in the first quantum dot solution to obtain a first quantum dot layer, performing an exposure treatment on the first quantum dot layer and then developing it, cross-linking each first quantum dot to obtain a first quantum dot layer array; setting a first protective quantum dot solution on the exposed surface of the substrate, the first protective quantum dot solution containing a photoinitiator, drying the solvent in the first protective quantum dot solution to obtain a first protective quantum dot layer to be processed, the first protective quantum dot layer to be processed at least covering the first The invention discloses a quantum dot layer array; a second mask is arranged above the substrate, and the first protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a first protective quantum dot layer, wherein the first part of the first protective quantum dot layer is located directly above and covers the first quantum dot layer array, and the second part of the first protective quantum dot layer is located on all sides of the first quantum dot layer array, and a first intermediate device is obtained; a second quantum dot solution is arranged on the first intermediate device, and the second quantum dot solution contains a photoinitiator; the solvent in the second quantum dot solution is dried to obtain a second quantum dot layer, a third mask is arranged above the substrate, and the second quantum dot layer is exposed and then developed, and each first The two quantum dots are cross-linked to obtain a second quantum dot layer array; a second protective quantum dot solution is arranged on the exposed surface of the substrate, the second protective quantum dot solution contains a photoinitiator, and the solvent in the second protective quantum dot solution is dried to obtain a second protective quantum dot layer to be processed, and the second protective quantum dot layer to be processed at least covers the second quantum dot layer array; a fourth mask is arranged above the substrate, and the second protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a second protective quantum dot layer, wherein the first part of the second protective quantum dot layer is located directly above and covers the second quantum dot layer array, and the second part of the second protective quantum dot layer is located above the fourth mask. The method comprises: placing a third quantum dot solution on the second intermediate device, wherein the third quantum dot solution contains a photoinitiator; drying the solvent in the third quantum dot solution to obtain a third quantum dot layer; placing a fifth mask above the substrate, performing an exposure treatment on the third quantum dot layer, and then developing the third quantum dot layer, so that each third quantum dot is cross-linked to obtain a third quantum dot layer array; placing a third protective quantum dot solution on the exposed surface of the substrate, wherein the third protective quantum dot solution contains a photoinitiator, drying the solvent in the third protective quantum dot solution to obtain a third protective quantum dot layer to be processed, wherein the third protective quantum dot layer to be processed at least covers the third quantum dot layer array;The sixth mask is arranged above the substrate, and the third protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a third protective quantum dot layer, wherein the first part of the third protective quantum dot layer is located directly above and covers the third quantum dot layer array, and the second part of the third protective quantum dot layer is located on all sides of the third quantum dot layer array, and a quantum dot light-emitting device is obtained. ;

[0012] Optionally, the drying method is heating drying, or when the quantum dot solution is provided, the method is a spin coating process and the solution is dried naturally during the spin coating process.

[0013] Optionally, the first quantum dot solution, the second quantum dot solution and the third quantum dot solution are all lipophilic, and each protective quantum dot solution is hydrophilic.

[0014] According to a second aspect of the present disclosure, a display panel is provided, comprising any one of the above-mentioned quantum dot light-emitting devices.

[0015] By applying the above technical solution, the quantum dot light-emitting device basically has no leakage current problem by providing a protective quantum dot layer, and the quantum dots in the protective quantum dot layer do not emit light when powered on, which does not affect the final light output spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting part of the present application are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings:

[0017] Figure 1 A schematic diagram of the structure of a quantum dot light-emitting device according to an embodiment of the present disclosure.

[0018] Figure 2 This is a schematic diagram of the structure of a quantum dot light-emitting device according to another embodiment of the present disclosure.

[0019] Figure 3 A partial schematic diagram of a method for preparing a quantum dot light-emitting device according to an embodiment of the present disclosure.

[0020] Figure 4 A partial schematic diagram of a method for preparing a quantum dot light-emitting device according to an embodiment of the present disclosure.

[0021] Figure numerals: 1, first electrode layer; 2, hole functional layer; 3, quantum dot layer array; 3', R / G / B quantum dot layer to be processed; 31', red quantum dot layer to be processed; 31, red quantum dot layer array; 32, green quantum dot layer array; 33, blue quantum dot layer array; 4', protective quantum dot layer to be processed; 41, first partial protective quantum dot layer; 42, second partial protective quantum dot layer; 5, electronic functional layer; 6, second electrode layer. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0023] According to a first aspect of the present disclosure, a quantum dot light-emitting device is provided, which includes a substrate having a first electrode layer, a red quantum dot layer array, a green quantum dot layer array and a blue quantum dot layer array arranged at intervals on the first electrode layer, the quantum dot light-emitting device also includes a protective quantum dot layer, the protective quantum dot layer includes a first part and a second part, the first part is located above the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array, and the second part is located between the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array so that there is no gap between the quantum dot layer arrays, and the band gap width of the protective quantum dots in the protective quantum dot layer is greater than the band gap width of the blue quantum dots in the blue quantum dot layer array; the quantum dot light-emitting device also includes a second electrode layer.

[0024] After obtaining multiple quantum dot layer arrays using the existing photolithography method, there are gaps between different quantum dot layer arrays to prevent cross-coloring. The use of the above-mentioned protective quantum dot layer can solve the problem of very large leakage current of QLED devices caused by direct contact between the functional layer (hole transport layer) on the quantum dot layer and the functional layer (hole transport layer) under the quantum dot layer after filling the gap. The quantum dots in the protective quantum dot layer do not emit light when powered on, and do not affect the final light spectrum.

[0025] The type of protective quantum dots (QD) is not limited as long as it meets the above-mentioned band gap width requirements, and it can be ZnS, CdSe, CdS, CdZnS, CdZnSeS, ZnTe, PbS, etc.

[0026] The substrate is a TFT substrate, which can independently control the light emission of each quantum dot layer. The quantum dot layers inside each quantum dot layer array have intervals or no intervals.

[0027] In some embodiments, the thickness of the first portion of the protective quantum dot layer is 5-200 nm, and the thickness of the second portion of the protective quantum dot layer is 5-200 nm.

[0028] In some embodiments, a hole functional layer is disposed on the first electrode layer, and a red quantum dot layer array, a green quantum dot layer array, and a blue quantum dot layer array are disposed on the hole functional layer. The hole functional layer can be a hole injection layer, a hole transport layer, a hole blocking layer, and a combination thereof. In some embodiments, the hole injection layer is PEDOT:PSS, and the hole transport layer is TFB. In some embodiments, an isolation structure (bank) with a thickness of less than 200 nm is disposed on the hole functional layer.

[0029] In some embodiments, an electronic functional layer is disposed on the protective quantum dot layer, including but not limited to an electron injection layer, an electron transport layer, and an electron blocking layer. In some embodiments, the electron transport layer is zinc magnesium oxide nanocrystals or zinc oxide nanocrystals or doped zinc oxide nanocrystals. In some embodiments, the thickness of the electronic functional layer is greater than the thickness of the protective quantum dot layer, such as Figure 1 shown.

[0030] like Figure 1 As shown, the quantum dot light emitting device includes a hole functional layer disposed on the first electrode layer, a red quantum dot layer array (R), a green quantum dot layer array (G) and a blue quantum dot layer array (B) disposed on the hole functional layer, a protective quantum dot layer composed of the first part and the second part, an electronic functional layer located on the quantum dot layer and a second electrode layer. Figure 2 As shown, the peripheries of the red quantum dot layer array, the green quantum dot layer array, and the blue quantum dot layer array correspond to protective quantum dot layers made of different materials. In other embodiments, the peripheries of the red quantum dot layer array, the green quantum dot layer array, and the blue quantum dot layer array are made of the same material. Figure 1 shown.

[0031] In traditional QLED devices, the injection barrier of holes is larger than that of electrons, resulting in an unbalanced injection of holes and electrons. The use of wide-bandgap protective quantum dots can effectively reduce the injection of electrons, thereby improving the electron-hole injection balance in QLED devices, thereby greatly improving the luminous efficiency of QLEDs.

[0032] In some embodiments, the first electrode layer is ITO and the second electrode layer is silver.

[0033] There is no limitation on the shape and arrangement of the quantum dot layer arrays of different colors, and reference may be made to the pixel arrangement design in the art.

[0034] In some embodiments, the spacing distance between each quantum dot layer array is 1-5 microns.

[0035] In some embodiments, Figure 3 As shown (the schematic diagram of the preparation process of the other two quantum dot layers is omitted, and the red quantum dots are taken as the first quantum dots as an example), the preparation method of the quantum dot light-emitting device includes: providing a substrate with a first electrode layer, setting a first quantum dot solution on the exposed surface of the substrate, and the first quantum dot solution contains a photoinitiator; drying the solvent in the first quantum dot solution to obtain a first quantum dot layer, setting a first mask template above the substrate, exposing the first quantum dot layer and then developing it, and cross-linking each first quantum dot to obtain a first quantum dot layer array; setting a second quantum dot solution on the exposed surface of the substrate, and the second quantum dot solution contains a photoinitiator, drying the solvent in the second quantum dot solution to obtain a second quantum dot layer, setting a second mask template above the substrate, exposing the second quantum dot layer and then developing it, and cross-linking each second quantum dot to obtain a second quantum dot layer array; setting A third quantum dot solution, wherein the third quantum dot solution contains a photoinitiator, so that the solvent in the third quantum dot solution is dried to obtain a third quantum dot layer, a third mask is set above the substrate, the third quantum dot layer is exposed and then developed, and each third quantum dot is cross-linked to obtain a third quantum dot layer array; there are gaps between the first quantum dot layer array, the second quantum dot layer array, and the third quantum dot layer array; the first quantum dot layer array, the second quantum dot layer array, and the third quantum dot layer array are non-repetitively selected from a red quantum dot layer array, a green quantum dot layer array, and a blue quantum dot layer array; a protective quantum dot solution is set on the exposed surface of the substrate and dried to obtain a protective quantum dot layer; or a protective quantum dot solution is set on the exposed surface of the substrate and dried, and the wet film layer formed by the protective quantum dot solution is exposed and developed, so that each protective quantum dot is cross-linked to obtain a protective quantum dot layer.

[0036] The photoinitiators in each quantum dot solution are the same or different. The photoinitiator can be selected from compounds containing benzophenone structure, azide structure or diazo structure.

[0037] The above exposure process may refer to the prior art, such as i-line or g-line exposure, with an exposure time of 3s-30s.

[0038] The above-mentioned development treatment can refer to the existing technology, such as immersing the semi-finished device in a developer for 1-3 minutes and then baking, or spray developing for 1-3 minutes and then baking.

[0039] The method of setting each quantum dot solution can be spin coating or full-surface coating or full-surface printing. Each (first, second, third, protective) quantum dot solution includes quantum dots and one or more solvents, additives, etc., which is conducive to the uniform setting of the quantum dot solution.

[0040] In some embodiments, when the protective quantum dots are cross-linked with each other, the polarity of the protective quantum dot solution is the same as or opposite to the polarity of the first, second, and third quantum dot solutions, preferably opposite, to reduce the damage of the solvent of the protective quantum dot solution to the underlying quantum dot layer caused by similar elution processes.

[0041] In some embodiments, when the protective quantum dots are not cross-linked, the polarity of the protective quantum dot solution is opposite to that of the first, second, and third quantum dot solutions, thereby reducing the dissolution or damage of the solvent of the protective quantum dot solution to the underlying quantum dot layer.

[0042] In some embodiments, the first quantum dot solution is red quantum dots, the second quantum dot solution is green quantum dots, and the third quantum dot solution is blue quantum dot solution. This preparation order reduces elution damage to blue quantum dots.

[0043] In some embodiments, Figure 4As shown in the figure (the schematic diagram of the preparation process of the other two quantum dot layers is omitted, and the red quantum dots are taken as the first quantum dots as an example), the preparation method of the quantum dot light-emitting device includes: providing a substrate with a first electrode layer, setting a first quantum dot solution on the substrate, and the first quantum dot solution contains a photoinitiator; setting a first mask template above the substrate to dry the solvent in the first quantum dot solution to obtain a first quantum dot layer, exposing the first quantum dot layer and then developing it, and cross-linking each first quantum dot to obtain a first quantum dot layer array; setting a first protective quantum dot solution on the exposed surface of the substrate, and the first protective quantum dot solution contains a photoinitiator, so that the solvent in the first protective quantum dot solution is dried to obtain a first protective layer to be treated. The first protective quantum dot layer to be processed at least covers the first quantum dot layer array; the second mask is set above the substrate, the first protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a first protective quantum dot layer, the first part of the first protective quantum dot layer is located and covers the first quantum dot layer array, and the second part of the first protective quantum dot layer is located on all sides of the first quantum dot layer array to obtain a first intermediate device; a second quantum dot solution is set on the first intermediate device, and the second quantum dot solution contains a photoinitiator; the solvent in the second quantum dot solution is dried to obtain a second quantum dot layer, and a third mask is set above the substrate, and the second protective quantum dot layer is cross-linked to obtain a first intermediate device; The quantum dot layer is exposed and then developed, and each second quantum dot is cross-linked to obtain a second quantum dot layer array; a second protective quantum dot solution is arranged on the exposed surface of the substrate, and the second protective quantum dot solution contains a photoinitiator, so that the solvent in the second protective quantum dot solution is dried to obtain a second protective quantum dot layer to be processed, and the second protective quantum dot layer to be processed at least covers the second quantum dot layer array; a fourth mask is arranged above the substrate, and the second protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a second protective quantum dot layer, and the first part of the second protective quantum dot layer is located and covers directly above the second quantum dot layer array, and the second protective quantum dot layer is directly above the second quantum dot layer array. The second part of the layer is located on all sides of the second quantum dot layer array to obtain a second intermediate device; a third quantum dot solution is arranged on the second intermediate device, and the third quantum dot solution contains a photoinitiator; the solvent in the third quantum dot solution is dried to obtain a third quantum dot layer, a fifth mask is arranged above the substrate, the third quantum dot layer is exposed and then developed, and each third quantum dot is cross-linked to obtain a third quantum dot layer array; a third protective quantum dot solution is arranged on the exposed surface of the substrate, and the third protective quantum dot solution contains a photoinitiator, and the solvent in the third protective quantum dot solution is dried to obtain a third protective quantum dot layer to be processed, and the third protective quantum dot layer to be processed at least covers the third quantum dot layer array;The sixth mask is set above the substrate, and the third protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a third protective quantum dot layer, and the first part of the third protective quantum dot layer is located directly above and covers the third quantum dot layer array, and the second part of the third protective quantum dot layer is located on all sides of the third quantum dot layer array, thereby obtaining a quantum dot light-emitting device. The first, second and third protective quantum dot layers fill the gaps between the first, second and third quantum dot layer arrays. Due to the existence of the protective quantum dot layer, each quantum dot layer array is protected when the next quantum dot layer array is prepared, thereby avoiding the performance degradation caused by multiple elutions of the first quantum dot and the second quantum dot. In addition, the above method can solve the problem of the final spectrum impurity caused by the residual quantum dots of other luminescent colors on the surface of a quantum dot layer. ;

[0044] In some embodiments, the first protective quantum dot solution, the second protective quantum dot solution, and the third protective quantum dot solution are the same, which reduces the complexity of configuring different solutions.

[0045] In some embodiments, the photoinitiators of each protected quantum dot solution are the same or different. The photoinitiator can be selected from compounds containing benzophenone structures, azide structures or diazo structures.

[0046] In some embodiments, the protective quantum dots in the first protective quantum dot solution, the second protective quantum dot solution, and the third protective quantum dot solution are different, which increases the charge injection balance adjustment space for different quantum dot layer arrays.

[0047] In some embodiments, the first quantum dot solution is red quantum dots, the second quantum dot solution is green quantum dots, and the third quantum dot solution is blue quantum dot solution, so as to reduce elution damage to the blue quantum dots.

[0048] In some embodiments, the drying method is heat drying, or the method of setting the quantum dot solution is a spin coating process and natural drying during the spin coating process. In some embodiments, the heat drying process is 50-100° C. and the time is 10-60 minutes.

[0049] In some embodiments, the developer (or eluent) used for development is a non-polar solvent or a polar solvent. In some embodiments, when the quantum dots are non-polar materials, the use of polar solvents as the developer can better protect the quantum dot materials to which the developer is applied. When the quantum dots are polar materials, the use of non-polar solvents as the developer can better protect the quantum dot materials to which the developer is applied. In some embodiments, the developer used for development is an alkaline aqueous solution, which is more environmentally friendly than alkane organic solvents, such as KOH or TMAH. The mass fraction of the alkaline substance in the developer can be 0.01%-0.1% KOH or 1%-5% TMAH. In some embodiments, the developer used for development is a non-polar solvent, such as octane, toluene, etc.

[0050] In some embodiments, the first quantum dot solution, the second quantum dot solution, and the third quantum dot solution are all lipophilic, and each protective quantum dot solution is hydrophilic. The solvent of the protective quantum dot solution is, for example, alcohol, etc., so as to better protect the first or second or third quantum dot layer formed on the substrate. If the surface of the quantum dot is a lipophilic ligand, such as a compound containing an alkane chain such as oleate, the solvent of the first, second or third quantum dot solution is a lipophilic solvent such as alkane, alkene or benzene.

[0051] According to a second aspect of the present disclosure, a display panel is provided, wherein the display panel comprises a quantum dot light-emitting device prepared by any one of the above-mentioned preparation methods. The display panel has good light-emitting performance.

[0052] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0053] Example 1

[0054] (1) The anode ITO (indium tin oxide) with a thickness of 180 nm was cleaned by ultrasonic cleaning with ethanol, deionized water and acetone for 10 minutes respectively, and then the liquid attached to the ITO surface was blown dry with N2, and then treated with oxygen plasma for 10 minutes to remove impurities on the ITO surface, thereby obtaining a clean ITO transparent conductive glass.

[0055] (2) Preparation of hole injection layer and hole transport layer: In an air environment, PEDOT:PSS (poly(p-styrene sulfonic acid solution)) was spin-coated on a clean ITO transparent conductive glass at a speed of 4000 rpm for 50 seconds. After the spin coating, it was annealed at 150°C in air for 30 minutes. Then it was transferred to a glove box in a nitrogen environment and annealed at 130°C for 20 minutes to finally form a PEDOT:PSS layer on the ITO surface, i.e., a hole injection layer. Then, a chlorobenzene solution (concentration of 8 mg / ml) of poly((9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butylphenyl)diphenylamine))(TFB)) was spin-coated on the PEDOT:PSS layer at a speed of 2000 rpm for 45 seconds. After the spin coating, it was annealed at 150°C in a glove box for 30 minutes to form a TFB hole transport layer.

[0056] (3) Preparation of red light-emitting layer: Spin-coat red quantum dot ink (quantum dots are CdSe / CdS, cadmium oleate ligand, emission wavelength is 620 nm, containing an appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0057] (4) Exposure and development 1: Use mask 1, ultraviolet exposure, and then use non-polar solvent n-octane to elute the quantum dot material in the non-exposed area.

[0058] (5) Protective QD layer: Continue to spin-coat the protective quantum dot solution (the quantum dots are small-sized ZnS, containing an appropriate amount of photoinitiator (azide compound), the solvent is an alcohol polar solvent, and the concentration is 20 mg / mL) at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0059] (6) Exposure and development 2: Use mask 2 (the exposure area is larger than mask 1), ultraviolet exposure, and then use polar solvents such as water or alcohol to wash away the protective quantum dot material in the non-exposed area.

[0060] (7) Preparation of green light-emitting layer: spin-coat green quantum dot ink (quantum dots are CdZnS / ZnS, cadmium oleate ligand, emission wavelength is 520 nm, contains appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0061] (8) Exposure and development 3: Use mask 3, ultraviolet exposure, and then use non-polar solvent n-octane to elute the quantum dot material in the non-exposed area.

[0062] (9) Protective QD layer: Continue to spin-coat the protective quantum dot solution (the band gap of the quantum dots is larger than that of the luminescent QDs, such as small-sized ZnS, containing an appropriate amount of photoinitiator (azide compound), the solvent is an alcohol polar solvent, and the concentration is 20 mg / mL), the rotation speed is 2000 rpm, and the spin coating time is 45 s.

[0063] (10) Exposure and development 2: Use mask 4 (the exposure area is larger than mask 3), ultraviolet exposure, and then use polar solvents such as water or alcohol to wash away the protective quantum dot material in the non-exposed area.

[0064] (11) Preparation of blue light-emitting layer: spin-coat blue quantum dot ink (quantum dots are CdZnS / ZnSeS, cadmium oleate ligand, emission wavelength is 460 nm, contains appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0065] (12) Exposure and development 5: Use a mask 5, ultraviolet exposure, and then use a non-polar solvent n-octane to elute the quantum dot material in the non-exposed area.

[0066] (13) Protective QD layer: Continue to spin-coat the protective quantum dot solvent (the quantum dots are small-sized ZnS, containing an appropriate amount of photoinitiator (azide compound), the solvent is an alcohol polar solvent, and the concentration is 20 mg / mL), the rotation speed is 2000 rpm, and the spin coating time is 45 s.

[0067] (14) Exposure and development 6: Use mask 6 (the exposure area is larger than mask 5), ultraviolet exposure, and then use polar solvent alcohol to wash away the protective quantum dot material in the non-exposed area.

[0068] (15) Preparation of zinc oxide nanocrystalline film: spin coating a zinc oxide nanocrystalline alcohol solution on the light-emitting layer at a rotation speed of 2500 rpm for 50 s. After spin coating, annealing was performed at 120 °C in a glove box for 30 min to finally form a zinc oxide nanocrystalline film on the surface of the light-emitting layer.

[0069] (16) Electrode preparation: The device obtained in step (15) is placed in a vacuum deposition chamber and a cathode silver electrode is deposited to a thickness of 100 nm.

[0070] Example 2

[0071]

Preparation of three-color lithography QLED light-emitting devices

[0072] (1) The anode ITO (indium tin oxide) with a thickness of 180 nm was cleaned by ultrasonic cleaning with ethanol, deionized water and acetone for 10 minutes respectively, and then the liquid attached to the ITO surface was blown dry with N2, and then treated with oxygen plasma for 10 minutes to remove impurities on the ITO surface, thereby obtaining a clean ITO transparent conductive glass.

[0073] (2) Preparation of hole injection layer and hole transport layer: In an air environment, PEDOT:PSS (poly(p-styrene sulfonic acid solution)) was spin-coated on a clean ITO transparent conductive glass at a speed of 4000 rpm for 50 seconds. After the spin coating, it was annealed at 150°C in air for 30 minutes. Then it was transferred to a glove box in a nitrogen environment and annealed at 130°C for 20 minutes to finally form a PEDOT:PSS layer on the ITO surface, i.e., a hole injection layer. Then, a chlorobenzene solution (concentration of 8 mg / ml) of poly((9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butylphenyl)diphenylamine))(TFB)) was spin-coated on the PEDOT:PSS layer at a speed of 2000 rpm for 45 seconds. After the spin coating, it was annealed at 150°C in a glove box for 30 minutes to form a TFB hole transport layer.

[0074] (3) Preparation of red light-emitting layer: Spin-coat red quantum dot ink (quantum dots are CdSe / CdS, cadmium oleate ligand, emission wavelength is 620 nm, containing an appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0075] (4) Exposure and development 1: Use mask 1, ultraviolet exposure, and then use non-polar solvent n-octane to elute the quantum dot material in the non-exposed area.

[0076] (5) Preparation of green light-emitting layer: spin-coat green quantum dot ink (quantum dots are CdZnS / ZnS, cadmium oleate ligand, emission wavelength is 520 nm, contains appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0077] (6) Exposure and development 2: Use mask 2 for UV exposure, and then use non-polar solvent n-octane to wash away the quantum dot material in the non-exposed area.

[0078] (7) Preparation of blue light-emitting layer: spin-coat blue quantum dot ink (quantum dots are CdZnS / ZnSeS, cadmium oleate ligand, emission wavelength is 460nm~470nm, containing appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45s.

[0079] (8) Exposure and development 3: Use a mask 3, ultraviolet exposure, and then use a non-polar solvent such as n-octane to elute the quantum dot material in the non-exposed area.

[0080] (9) Protective QD layer: Continue to spin-coat the protective quantum dot solution (the quantum dots are small-sized ZnS, containing an appropriate amount of photoinitiator (azide compound), the solvent is an alcohol polar solvent, and the concentration is 20 mg / mL) at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0081] (10) Exposure and development 6: Use mask 6 (the exposure area is larger than mask 5), ultraviolet exposure, and then use polar solvent alcohol to wash away the protective quantum dot material in the non-exposed area.

[0082] (11) Preparation of zinc oxide nanocrystalline film: spin coating a zinc oxide nanocrystalline alcohol solution on the light-emitting layer at a rotation speed of 2500 rpm for 50 s. After spin coating, annealing was performed at 120°C in a glove box for 30 min to finally form a zinc oxide nanocrystalline film on the surface of the light-emitting layer.

[0083] (12) Electrode preparation: The device obtained in step (12) is placed in a vacuum deposition chamber, and a cathode silver electrode is deposited to a thickness of 100 nm.

[0084] Example 3

[0085] The difference from Example 1 is that in (10), a non-polar solvent n-octane is used to elute the protective quantum dot material in the non-exposed area.

[0086] Example 4

[0087] The difference from Example 2 is that there is no photoinitiator in the protective quantum dot solution in (9), there is no step (10), and the protective quantum dots are not cross-linked.

[0088] Comparative Example 1

[0089] The difference from Example 2 is that there is no protective quantum dot layer and the corresponding preparation process.

[0090] Comparative Example 2

[0091] The difference from Example 2 is that the protective quantum dots are CdSe, which has a smaller band gap than the blue quantum dots.

[0092] The following tests were performed on each QLED device: the current density-voltage curve of the quantum dot light-emitting device was measured using Keithley 2400, and the brightness of the quantum dot light-emitting device was measured using an integrating sphere (FOIS-1) combined with an Ocean Optics spectrometer (QE-pro). The external quantum efficiency of the quantum dot light-emitting device was calculated based on the measured current density and brightness, and the results are recorded in Table 1. The external quantum efficiency represents the ratio between the number of photons emitted by the light-emitting device and the number of electrons injected into the device in the observation direction, and is an important parameter for characterizing the luminous efficiency of the light-emitting device. The higher the external quantum efficiency, the higher the luminous efficiency of the device.

[0093] The luminous properties of various embodiments and comparative examples are shown in Table 1.

[0094] Table 1

[0095]

[0096] The use of a narrow bandgap protective QD layer (Comparative Example 2) is completely opposite to Example 1, and the red light emitting performance of the QLED is greatly reduced to 7.5%. This is mainly because the narrow bandgap protective QD layer not only does not reduce the injection of electrons, but instead causes holes to be injected from the QD layer to the protective QD layer, causing the protective QD layer to emit light (Table 1 - the protective QD layer accounts for 20% of the light emission), affecting the red light emitting performance of the device.

[0097] Conventional photolithography QLED is usually carried out in the manner of photolithography red QD-photolithography green QD-photolithography blue QD, so the red QD is usually eluted three times with a developer. The inventors found in the experiment that the more times the elution is done, the worse the QLED performance. Using the conventional three-color QLED preparation process, green QD and blue QD will be spin-coated on the surface of the red QD, and blue QD will be spin-coated on the surface of the green QD. The surface elution process is usually difficult to completely remove, and QD is easy to penetrate into the interior of the luminescent QD (the solvents of the red, green and blue quantum dot solutions are the same or similar), which manifests as impure red and green luminescence spectra (the proportion of stray light in Comparative Example 1 is 6% and 3%, respectively). As in Example 1, after preparing a protective quantum dot layer using a protective QD solution with a solvent of different polarity from the quantum dot layer, the subsequent QD solution does not infiltrate the surface of the protective QD layer, and the elution is very good, which can completely solve the residual problem of other luminescent QDs (the proportion of stray light in Example 1 is 0%). Furthermore, filling protective QDs between QD layers can effectively solve the leakage problem. Specifically, the current of QLED device decreases from 3.6×10 -1 mA / cm 2 (Comparative Example 1) dropped significantly to 1.2-1.5×10 -3 mA / cm 2 (Examples 1-4).

[0098] If a non-polar solvent is used as the solvent for the protective QD (Example 3), spin coating the protective QD solution is equivalent to eluting the red, green and blue QDs once, so the overall performance will be reduced compared to Example 1.

[0099] Whether or not the protective QDs are photolithographically fabricated (Examples 2 and 4) has little effect on the overall performance, which can be reasonably explained by the fact that illumination does not affect the size, energy level and charge transport performance of the QDs.

[0100] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A quantum dot light-emitting device, characterized in that: The quantum dot light-emitting device includes a substrate having a first electrode layer, a red quantum dot layer array, a green quantum dot layer array and a blue quantum dot layer array arranged at intervals on the first electrode layer, and the quantum dot light-emitting device also includes a protective quantum dot layer, the protective quantum dot layer includes a first part and a second part, the first part is located above the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array, and the second part is located between the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array so that there is no gap between the quantum dot layer arrays, and the band gap width of the protective quantum dots in the protective quantum dot layer is greater than the band gap width of the blue quantum dots in the blue quantum dot layer array; the quantum dot light-emitting device also includes a second electrode layer.

2. The quantum dot light-emitting device according to claim 1, characterized in that: The thickness of the protective quantum dot layer of the first portion is 5-200 nm, and the thickness of the protective quantum dot layer of the second portion is 5-200 nm.

3. The quantum dot light-emitting device according to claim 1, characterized in that: A hole functional layer is disposed on the first electrode layer, and the red quantum dot layer array, the green quantum dot layer array and the blue quantum dot layer array are disposed on the hole functional layer.

4. The quantum dot light-emitting device according to claim 1, characterized in that: An electronic functional layer is disposed on the protective quantum dot layer, and the thickness of the electronic functional layer is greater than the thickness of the protective quantum dot layer.

5. The quantum dot light-emitting device according to claim 1, characterized in that: The spacing between each quantum dot layer array is 1-5 microns.

6. The quantum dot light emitting device according to claim 1, characterized in that: The preparation method of the quantum dot light-emitting device includes: providing a substrate with a first electrode layer, setting a first quantum dot solution on the exposed surface of the substrate, the first quantum dot solution containing a photoinitiator; drying the solvent in the first quantum dot solution to obtain a first quantum dot layer, setting a first mask template above the substrate, performing an exposure treatment on the first quantum dot layer and then developing it, cross-linking each first quantum dot to obtain a first quantum dot layer array; setting a second quantum dot solution on the exposed surface of the substrate, the second quantum dot solution containing a photoinitiator, drying the solvent in the second quantum dot solution to obtain a second quantum dot layer, setting a second mask template above the substrate, performing an exposure treatment on the second quantum dot layer and then developing it, cross-linking each second quantum dot to obtain a second quantum dot layer array; setting a third quantum dot solution on the exposed surface of the substrate, the third quantum dot solution containing a photoinitiator , so that the solvent in the third quantum dot solution is dried to obtain a third quantum dot layer, a third mask is set above the substrate, the third quantum dot layer is exposed and then developed, and each third quantum dot is cross-linked to obtain a third quantum dot layer array; there is a gap between the first quantum dot layer array, the second quantum dot layer array, and the third quantum dot layer array; the first quantum dot layer array, the second quantum dot layer array, and the third quantum dot layer array are non-repeatedly selected from a red quantum dot layer array, a green quantum dot layer array, and a blue quantum dot layer array; a protective quantum dot solution is set on the exposed surface of the substrate and dried to obtain the protective quantum dot layer; or a protective quantum dot solution is set on the exposed surface of the substrate and dried, and the wet film layer formed by the protective quantum dot solution is exposed and developed, so that each protective quantum dot is cross-linked to obtain the protective quantum dot layer.

7. The quantum dot light-emitting device according to claim 1, characterized in that: The preparation method of the quantum dot light-emitting device includes: providing a substrate with a first electrode layer, setting a first quantum dot solution on the substrate, the first quantum dot solution containing a photoinitiator; setting a first mask above the substrate to dry the solvent in the first quantum dot solution to obtain a first quantum dot layer, performing an exposure treatment on the first quantum dot layer and then developing it, cross-linking each first quantum dot to obtain a first quantum dot layer array; setting a first protective quantum dot solution on the exposed surface of the substrate, the first protective quantum dot solution containing a photoinitiator, drying the solvent in the first protective quantum dot solution to obtain a first protective quantum dot layer to be treated , the first protective quantum dot layer to be processed at least covers the first quantum dot layer array; a second mask is set above the substrate, the first protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a first protective quantum dot layer, the first part of the first protective quantum dot layer is located and covers the first quantum dot layer array directly above, and the second part of the first protective quantum dot layer is located on all sides of the first quantum dot layer array, to obtain a first intermediate device; a second quantum dot solution is set on the first intermediate device, and the second quantum dot solution contains a photoinitiator; so that the second quantum dot solution The solvent is dried to obtain a second quantum dot layer, a third mask is set above the substrate, the second quantum dot layer is exposed to light and then developed, and each second quantum dot is cross-linked to obtain a second quantum dot layer array; a second protective quantum dot solution is set on the exposed surface of the substrate, the second protective quantum dot solution contains a photoinitiator, and the solvent in the second protective quantum dot solution is dried to obtain a second protective quantum dot layer to be processed, and the second protective quantum dot layer to be processed at least covers the second quantum dot layer array; a fourth mask is set above the substrate, the second protective quantum dot layer to be processed is exposed to light and then developed, The protective quantum dots are cross-linked to obtain a second protective quantum dot layer, wherein the first portion of the second protective quantum dot layer is located directly above and covers the second quantum dot layer array, and the second portion of the second protective quantum dot layer is located on all sides of the second quantum dot layer array, thereby obtaining a second intermediate device; a third quantum dot solution is disposed on the second intermediate device, wherein the third quantum dot solution contains a photoinitiator; the solvent in the third quantum dot solution is dried to obtain a third quantum dot layer, a fifth mask is disposed above the substrate, the third quantum dot layer is exposed and then developed, and the third quantum dots are cross-linked to obtain a third quantum dot layer array;A third protective quantum dot solution is arranged on the exposed surface of the substrate, the third protective quantum dot solution contains a photoinitiator, and the solvent in the third protective quantum dot solution is dried to obtain a third protective quantum dot layer to be processed, and the third protective quantum dot layer to be processed at least covers the third quantum dot layer array; a sixth mask is arranged above the substrate, and the third protective quantum dot layer to be processed is exposed and then developed, and each protective quantum dot is cross-linked to obtain a third protective quantum dot layer, the first part of the third protective quantum dot layer is located and covers the third quantum dot layer array directly above, and the second part of the third protective quantum dot layer is located on all sides of the third quantum dot layer array, and the quantum dot light-emitting device is obtained. ; 8. The quantum dot light-emitting device according to claim 6 or 7, characterized in that: The drying method is heating drying, or the method of setting the quantum dot solution is a spin coating process and natural drying is performed during the spin coating process.

9. The quantum dot light-emitting device according to claim 6 or 7, characterized in that: The first quantum dot solution, the second quantum dot solution and the third quantum dot solution are all lipophilic, and each of the protective quantum dot solutions is hydrophilic.

10. A display panel, characterized in that: The display panel comprises any one of the quantum dot light-emitting devices according to claims 1 to 8.

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