Quantum dot light emitting device and display panel containing same

Abstract

The present disclosure provides a quantum dot light-emitting device and a display panel comprising the same. The quantum dot light-emitting device comprises a substrate having a first electrode layer, an array of red quantum dot layers, an array of green quantum dot layers and an array of blue quantum dot layers arranged at intervals on the first electrode layer, and a protective quantum dot layer. The protective quantum dot layer comprises a first part and a second part. The first part is located on the array of red quantum dot layers, the array of green quantum dot layers and the array of blue quantum dot layers. The second part is located between the array of red quantum dot layers, the array of green quantum dot layers and the array of blue quantum dot layers so that there is no gap between each array of quantum dot layers. 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 array of blue quantum dot layers. The quantum dot light-emitting device further comprises a second electrode layer. The quantum dot light-emitting device has substantially no problem of leakage current by providing the protective quantum dot layer. The quantum dots in the protective quantum dot layer do not emit light under the condition of power-on, which does not affect the final light spectrum.

Description

TECHNICAL FIELD

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

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

[0003] The most commonly used photolithography QLED at present is the quantum dot ligand photocrosslinking method, but after the preparation of the quantum dot layer by photolithography, the gap between different quantum dot layers is filled by the electron transport layer, which results in a large QLED device leakage current due to the direct contact between the hole transport layer. SUMMARY

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

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

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

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

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

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

[0010] Optionally, the preparation method of a 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 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 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 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-repeatedly selected from the red quantum dot layer array, the green quantum dot layer array, and the 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 to cross-link each protective quantum dot 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, disposing a first quantum dot solution on the substrate, the first quantum dot solution containing a photoinitiator; disposing a first mask 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, cross-linking each first quantum dot to obtain a first quantum dot layer array; disposing 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 relates to a quantum dot layer array; a second mask is set 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, and 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 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 quantum dot layer is exposed and then developed, and each first protective quantum dot is cross-linked to obtain a first protective quantum dot layer. The two quantum dots are 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 treated, and the second protective quantum dot layer to be treated at least covers the second quantum dot layer array; a fourth mask is set above the substrate, and the second protective quantum dot layer to be treated is exposed and then developed, and each protective quantum dot is cross-linked to obtain a second protective quantum dot layer, 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 part of the second protective quantum dot layer is located in the fourth mask. all sides of the two quantum dot layer arrays to obtain a second intermediate device; a third quantum dot solution is disposed on the second intermediate device, the third quantum dot solution containing 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 each third quantum dot is cross-linked to obtain a third quantum dot layer array; a third protective quantum dot solution is disposed on the exposed surface of the substrate, the third protective quantum dot solution containing a photoinitiator, the solvent in the third protective quantum dot solution is dried 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 plate is arranged above the substrate, and a third protective quantum dot layer to be processed is exposed and developed after the exposure treatment, so as to cross-link each protective quantum dot, thereby obtaining the third protective quantum dot layer, a first part of the third protective quantum dot layer is located above and covers the third quantum dot layer array, and a second part of the third protective quantum dot layer is located on all sides of the third quantum dot layer array, thereby obtaining the quantum dot light-emitting device.

[0012] Optionally, the drying manner is heating drying, or the setting manner of the quantum dot solution is a spin coating process and natural drying in the spin coating process.

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

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

[0015] By using the technical solution described above, the quantum dot light-emitting device provides a protective quantum dot layer, so that there is basically no problem of leakage current, and the quantum dots in the protective quantum dot layer do not emit light under the condition of power supply, which does not affect the final light spectrum. BRIEF DESCRIPTION OF DRAWINGS

[0016] The drawings accompanying the specification of the present application serve to provide a further understanding of the present disclosure, and the illustrative embodiments of the present disclosure and their descriptions serve to explain the present disclosure, and do not constitute an improper limitation on the present disclosure. In the drawings:

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

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

[0019] Figure 3 FIG. 3 is a partial flow schematic diagram of a preparation method of a quantum dot light-emitting device according to an embodiment of the present disclosure.

[0020] Figure 4 FIG. 4 is a partial flow schematic diagram of a preparation method of a quantum dot light-emitting device according to another embodiment of the present disclosure.

[0021] Reference 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 part of protective quantum dot layer; 42, second part of protective quantum dot layer; 5, electron functional layer; 6, second electrode layer. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed description is illustrative only and is intended to provide further description of the present application. 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.

[0023] According to a first aspect of the present disclosure, a quantum dot light-emitting device is provided, which comprises 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 a protective quantum dot layer, the protective quantum dot layer comprising a first part and a second part, the first part being 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 being 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, the band gap width of the protective quantum dots in the protective quantum dot layer being greater than the band gap width of the blue quantum dots in the blue quantum dot layer array; the quantum dot light-emitting device further comprises a second electrode layer.

[0024] The existing photolithography method obtains a plurality of quantum dot layer arrays, and gaps exist between different quantum dot layer arrays for preventing color bleeding. The use of the protective quantum dot layer described above can solve the problem of very large leakage current of a QLED device caused by the direct contact of the functional layer (such as an electron transport layer) on the quantum dot layer with the functional layer (a hole transport layer) below the quantum dot layer after the gaps are filled by the functional layer. The quantum dots in the protective quantum dot layer do not emit light under the condition of power supply, and do not affect the final light spectrum.

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

[0026] The substrate described above is a TFT substrate, and the light emission of each quantum dot layer can be independently controlled. The quantum dot layers inside each quantum dot layer array have intervals or do not have 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, or 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) having a thickness of less than 200 nm is disposed on the hole-functional layer.

[0029] In some embodiments, an electronic functional layer is provided 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 arranged 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) arranged on the hole functional layer, a protective quantum dot layer composed of a first part and a 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 hole injection barrier is larger than the electron injection barrier, 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 significantly 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 various colors, and reference may be made to pixel arrangement designs in the art.

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

[0035] In some embodiments, as 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 used 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, 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, cross-linking each second quantum dot to obtain a second quantum dot layer array; setting A third quantum dot solution, 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-repeatedly selected from the red quantum dot layer array, the green quantum dot layer array, and the 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 a benzophenone structure, an azide structure, or a diazo structure.

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

[0038] The above-mentioned development process 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 quantum dot solutions can be placed by spin coating, full-surface coating, or full-surface printing. Each (first, second, third, and protective) quantum dot solution includes quantum dots and one or more solvents, additives, etc., which facilitates uniform placement of the quantum dot solution.

[0040] In some embodiments, where the protective quantum dots are cross-linked, the polarity of the protective quantum dot solution is the same or opposite, preferably opposite, to the polarity of the first, second, and third quantum dot solutions, reducing damage to the underlying quantum dot layer by the solvent of the protective quantum dot solution during a similar elution process.

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

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

[0043] In some embodiments, as Figure 4As shown in FIG1 (a schematic diagram of the preparation process of the other two quantum dot layers is omitted, and the red quantum dot is used as the first quantum dot as an example), 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, and the first quantum dot solution contains 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, 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 first protective quantum dot solution on the exposed surface of the substrate, and the first protective quantum dot solution contains a photoinitiator, and 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, a first portion of the first protective quantum dot layer is located directly above and covers the first quantum dot layer array, and a second portion 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 to expose the second quantum dot layer. 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 set 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 treated, and the second protective quantum dot layer to be treated at least covers the second quantum dot layer array; a fourth mask is set above the substrate, and the second protective quantum dot layer to be treated 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 located directly above the second quantum dot layer array. The second portion 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 disposed on the second intermediate device, the third quantum dot solution containing 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 each third quantum dot is cross-linked to obtain a third quantum dot layer array; a third protective quantum dot solution is disposed on the exposed surface of the substrate, the third protective quantum dot solution containing 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, wherein the third protective quantum dot layer to be processed at least covers the third quantum dot layer array;A sixth mask is placed above the substrate, and the third protective quantum dot layer to be processed is exposed and then developed. The protective quantum dots are cross-linked to obtain a third protective quantum dot layer. The first portion of the third protective quantum dot layer is located directly above and covers the third quantum dot layer array, and the second portion 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 presence 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 and second quantum dots. In addition, the above method can solve the problem of final spectral impurity caused by quantum dots of other luminescent colors remaining 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 a benzophenone structure, an azide structure, or a diazo structure.

[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 a polar solvent as a developer can better protect the quantum dot material to which the developer is applied. When the quantum dots are polar materials, the use of a non-polar solvent as a developer can better protect the quantum dot material 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, second, and third quantum dot solutions are all lipophilic. In this case, each protective quantum dot solution is hydrophilic, and the solvent of the protective quantum dot solution, such as an alcohol, can better protect the first, second, or third quantum dot layer formed on the substrate. If the quantum dot surface has a lipophilic ligand, such as an alkane chain-containing compound such as oleate, the solvent of the first, second, or third quantum dot solution can be a lipophilic solvent such as an alkane, alkene, or benzene.

[0051] According to a second aspect of the present disclosure, a display panel is provided, comprising a quantum dot light-emitting device prepared by any 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 min respectively, and then the liquid attached to the ITO surface was blown dry with N2, and the impurities on the ITO surface were removed by oxygen plasma treatment for 10 min to obtain 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 was completed, it was annealed at 150°C in air for 30 minutes, and then 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 was formed. Then, a chlorobenzene solution of poly((9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butylphenyl)diphenylamine))(TFB)) (concentration of 8 mg / ml) was spin-coated on the PEDOT:PSS layer at a speed of 2000 rpm for 45 seconds. After the spin coating was completed, 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 speed of 2000 rpm and a spin-coating time of 45 s.

[0057] (4) Exposure and development 1: Use mask 1 for UV 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), the rotation speed is 2000 rpm, and the spin coating time is 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 elute 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, containing an appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a speed of 2000 rpm and a spin-coating time of 45 s.

[0061] (8) Exposure and development 3: Use mask 3 for UV 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 elute 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, containing an appropriate amount of photoinitiator (azide compound), solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a speed of 2000 rpm and a spin-coating time of 45 s.

[0065] (12) Exposure and development 5: Use mask 5 for UV exposure, and then use 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 elute the protective quantum dot material in the non-exposed area.

[0068] (15) Preparation of zinc oxide nanocrystalline film: spin coating zinc oxide nanocrystalline alcohol solution on the light-emitting layer at a speed of 2500 rpm for 50 s. After spin coating, annealing treatment 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 evaporation chamber, and a cathode silver electrode is evaporated to a thickness of 100 nm.

[0070] Example 2

[0071]

Preparation of three-color lithography QLED light-emitting devices

[0072] (1) Cleaning treatment of anode ITO (indium tin oxide) with a thickness of 180 nm: ultrasonic cleaning treatment with ethanol, deionized water and acetone for 10 min, respectively, then blowing the liquid adhered to the ITO surface with N2, and treating with oxygen plasma for 10 min to remove the impurities on the ITO surface, to obtain clean ITO transparent conductive glass.

[0073] (2) Preparation of hole injection layer and hole transport layer: spin-coating PEDOT:PSS (poly (p-phenylene vinylene sulfonic acid) solution) on the clean ITO transparent conductive glass in air environment at a rotation speed of 4000 rpm for 50 s, and then annealing at 150°C in air for 30 min, and then transferring it to a nitrogen environment glove box, and annealing at 130°C for 20 min, to finally form a PEDOT:PSS layer on the ITO surface, i.e. to form a hole injection layer; then spin-coating 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) on the PEDOT:PSS layer at a rotation speed of 2000 rpm for 45 s, and then annealing at 150°C in the glove box for 30 min to form a TFB hole transport layer.

[0074] (3) Preparation of red light-emitting layer: spin-coating 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 for 45 s.

[0075] (4) Exposure and development 1: using mask plate 1, ultraviolet exposure, and then using 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-coating green quantum dot ink (quantum dots are CdZnS / ZnS, cadmium oleate ligand, emission wavelength is 520 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 for 45 s.

[0077] (6) Exposure and development 2: using mask plate 2, ultraviolet exposure, and then using non-polar solvent n-octane to elute the quantum dot material in the non-exposed area.

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

[0079] (8) Exposure and development 3: use mask plate 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 a protective quantum dot solution (quantum dots are small-size ZnS, containing a certain amount of photoinitiator (azide compound), solvent is an alcohol polar solvent, concentration is 20 mg / mL), the rotation speed is 2000 rpm, and the spin-coating time is 45 s.

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

[0082] (11) Fabrication of zinc oxide nanocrystal thin film: spin-coat zinc oxide nanocrystal alcohol solution on the light emitting layer at a rotation speed of 2500 rpm, the spin-coating time is 50 s, and after the spin-coating, perform annealing treatment at 120°C in a glove box for 30 min, so as to form a zinc oxide nanocrystal thin film on the surface of the light emitting layer.

[0083] (12) Fabrication of electrode: place the device prepared in step (12) in a vacuum evaporation chamber, and evaporate a silver cathode electrode with a thickness of 100 nm.

[0084] Example 3

[0085] The difference between Example 3 and Example 1 is that a non-polar solvent n-octane is used to elute the protective quantum dot material in the non-exposed area in (10).

[0086] Example 4

[0087] The difference between Example 4 and Example 2 is that there is no photoinitiator in the protective quantum dot solution in (9), and there is no step (10), and the protective quantum dots are not cross-linked.

[0088] Comparative Example 1

[0089] The difference between Comparative Example 1 and Example 2 is that there is no protective quantum dot layer and the corresponding preparation process.

[0090] Comparative Example 2

[0091] The difference between Comparative Example 2 and Example 2 is that the protective quantum dots are CdSe, and the band gap is smaller than that of the blue quantum dots.

[0092] The following tests were performed on each of the prepared QLED devices: the current density-voltage curve of the quantum dot light-emitting device was determined using a Keithley 2400, and the luminance of the quantum dot light-emitting device was determined 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 according to the determined current density and luminance, and the results are shown in Table 1. The external quantum efficiency represents the ratio between the number of photons emitted by the light-emitting device in the observation direction and the number of electrons injected into the device, and is an important parameter for characterizing the light-emitting efficiency of the light-emitting device. The higher the external quantum efficiency, the higher the light-emitting efficiency of the device.

[0093] The light-emitting performance of each of the examples and comparative examples is shown in Table 1.

[0094] Table 1

[0095]

[0096] In contrast to Example 1, the use of a narrow-bandgap protective QD layer (Comparative Example 2) resulted in a significant decrease in the red light-emitting performance of the QLED to 7.5%. This is mainly because the narrow-bandgap protective QD layer not only does not reduce the injection of electrons, but also causes holes to be injected from the QD layer to the protective QD layer, resulting in light emission from the protective QD layer (20% of the light emission from the protective QD layer, Table 1), which affects the red light-emitting performance of the device.

[0097] Conventional photolithographic QLEDs are usually prepared in the order of photolithographic red QD-photolithographic green QD-photolithographic blue QD, so the red QD is usually washed off three times using a developer. The inventors found in experiments that the more times the washing is performed, the worse the performance of the QLED. Using the preparation process of conventional three-color QLEDs, the surface of the red QD is spin-coated with green QD and blue QD, and the surface of the green QD is spin-coated with blue QD. The surface washing process is usually difficult to completely remove, and the QD can easily penetrate into the light-emitting QD (the solvents of the red, green and blue quantum dot solutions are the same or similar), resulting in impure red and green light-emitting spectra (the impurity light accounts for 6% and 3%, respectively, in Comparative Example 1). However, as in Example 1, after the protective QD layer is prepared using a protective QD solution having a different polarity from the quantum dot layer, the subsequent QD solution does not wet the surface of the protective QD layer, and the washing is very good, which can completely solve the problem of residual other light-emitting QD (the impurity light accounts for 0% in Example 1). Further, filling the protective QD between the QD layers can effectively solve the problem of current leakage, which is manifested by a significant decrease in the current from 3.6 x 10 -1 mA / cm 2 (Comparative Example 1) to 1.2-1.5 x 10 -3 mA / cm 2 (Examples 1-4).

[0098] The solvent of the protective QDs If a non-polar solvent is used (Example 3), the spin-coating of the protective QD solution is equivalent to a single elution of the red, green and blue QDs, so the overall performance will be lower than that of Example 1.

[0099] The protective QD photolithography or not (Example 2 and Example 4) has little effect on the overall performance, which can be reasonably explained that the light does not affect the size, energy level and charge transport performance of the QDs.

[0100] The above only describes the preferred embodiments of the present disclosure and is not intended to limit the present disclosure. Those skilled in the art can make various modifications and changes to the present disclosure. 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, 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, 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, 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 provided 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 provided on the hole functional layer.

4. The quantum dot light-emitting device according to claim 1, characterized in that An electronic functional layer is provided 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 having a first electrode layer, disposing 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, disposing a first mask 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; disposing 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, disposing a second mask 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; disposing 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 method for preparing the quantum dot light-emitting device includes: providing a substrate having a first electrode layer, disposing a first quantum dot solution on the substrate, the first quantum dot solution containing a photoinitiator; disposing a first mask 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, so that each first quantum dot is cross-linked to obtain a first quantum dot layer array; disposing 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 covers the first quantum dot layer array; a second mask is placed 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, a first portion of the first protective quantum dot layer is located and covers directly above the first quantum dot layer array, and a second portion of the first protective quantum dot layer is located on all sides of the first quantum dot layer array, thereby obtaining a first intermediate device; a second quantum dot solution is placed on the first intermediate device, the second quantum dot solution containing a photoinitiator; so that the second quantum dot solution The solvent is dried to obtain a second quantum dot layer, a third mask is placed 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 placed 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 placed 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 a first portion of the second protective quantum dot layer is located directly above and covers the second quantum dot layer array, and a 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, and the third quantum dot layer is exposed and then developed, thereby cross-linking the third quantum dots to obtain a third quantum dot layer array;A third protective quantum dot solution containing a photoinitiator is disposed on the exposed surface of the substrate, and the solvent in the third protective quantum dot solution is dried 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. A sixth mask is disposed above the substrate, and the third protective quantum dot layer to be processed is exposed and then developed to crosslink the protective quantum dots to obtain a third protective quantum dot layer, wherein a first portion of the third protective quantum dot layer is located directly above and covers the third quantum dot layer array, and a second portion of the third protective quantum dot layer is located on all sides of the third quantum dot layer array, thereby obtaining the quantum dot light-emitting device.

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 carried out 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 the quantum dot light-emitting device according to any one of claims 1 to 8.

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