Light-emitting device and preparation method therefor, and display apparatus

Abstract

Provided in the present disclosure are a light-emitting device and a preparation method therefor, and a display apparatus. The light-emitting device comprises: a first electrode; a quantum dots light-emitting layer; an electron transport layer, which is located on the side of the quantum dots light-emitting layer that is away from the first electrode; and a protective layer, which is located on the side of the quantum dots light-emitting layer that is away from the first electrode. The quantum dots light-emitting layer comprises organic acid groups, and the protective layer blocks the organic acid groups from coming into contact with the electron transport layer.

Description

Light-emitting device, manufacturing method thereof, and display device Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a light-emitting device and a method for manufacturing the same, and a display device including the light-emitting device. Background Art

[0002] Light emitting diodes (LEDs) emit light by releasing energy through the recombination of electrons and holes. Light emitting diodes include but are not limited to organic light emitting diodes (OLEDs) and quantum dot light emitting diodes (QLEDs). Quantum dots are a type of semiconductor nanomaterial that can bind excitons in three-dimensional space. Due to their excellent properties such as high quantum efficiency, narrow excitation spectrum, high photostability, long fluorescence lifetime, and good solution processing compatibility, they have great application potential in high-quality displays. Quantum dot light emitting diodes are devices that use quantum dots as light-emitting materials. Compared with organic light emitting diodes, they have outstanding advantages such as lower energy consumption, higher color purity, and a wider color gamut. Therefore, quantum dot light emitting technology has become the most promising next-generation self-luminous display technology.

[0003] Summary of the Invention

[0004] According to one aspect of the present disclosure, a light-emitting device is provided, comprising: a first electrode; a quantum dot light-emitting layer; an electron transport layer located on a side of the quantum dot light-emitting layer remote from the first electrode; and a protective layer located on a side of the quantum dot light-emitting layer remote from the first electrode. The quantum dot light-emitting layer comprises organic acid groups, and the protective layer blocks the organic acid groups from contacting the electron transport layer.

[0005] In some embodiments, the protective layer is at least located between the quantum dot light-emitting layer and the electron transport layer.

[0006] In some embodiments, the protection layer is further located in the electron transport layer.

[0007] In some embodiments, the protective layer is located on a side of the electron transport layer close to the quantum dot light-emitting layer, and the protective layer is in contact with the quantum dot light-emitting layer.

[0008] In some embodiments, the protective layer comprises an anti-contact layer or a salt layer.

[0009] In some embodiments, the salt layer comprises a carboxylate layer or a quaternary ammonium salt layer.

[0010] In some embodiments, the salt layer further includes unreacted base.

[0011] In some embodiments, the material of the anti-contact layer includes any one of a hydrophobic material, a silane coupling agent, and an epoxy resin.

[0012] In some embodiments, the salt layer is in physical contact with the electron transport layer.

[0013] In some embodiments, the salt layer is connected to the electron transport layer through a chemical bond.

[0014] In some embodiments, the electron transport layer includes a ZnO body and a first coordination group coordinated to the ZnO body, and the salt layer is connected to at least some of the first coordination groups through the chemical bond.

[0015] In some embodiments, the electron transport layer includes a first surface close to the quantum dot light-emitting layer and a second surface away from the quantum dot light-emitting layer, the salt layer is connected to the first coordination group at the first surface through the chemical bond, and the second surface includes a first ligand coordinated to the ZnO body, and the first ligand includes a basic group.

[0016] In some embodiments, the first ligand has the general chemical formula Wherein, the group R represents an alkyl chain, and the group X is selected from any one of the following:

[0017] In some embodiments, the protective layer includes a surfactant that wraps the electron transport layer.

[0018] In some embodiments, the electron transport layer includes zinc oxide nanoparticles, and the protective layer includes a surfactant, which wraps the zinc oxide nanoparticles.

[0019] In some embodiments, the surfactant has the general chemical formula A + B - , where A + represents cations, B - Indicates anion. B - Selected from halogen ions, hydroxide ions, PF6 - 、BF4 - Any of; and, A + The chemical formula is C n H 2n+1 N(C m H 2m+1 )3 or C n H 2n+1 N(C m H 2m+1)2(C m H 2m+1 )2NC n H 2n+1 , n is any positive integer between 8 and 20, and m is any positive number between 0 and 4.

[0020] In some embodiments, the quantum dot light-emitting layer includes a plurality of quantum dots, at least some of the plurality of quantum dots include a quantum dot body and a second ligand coordinated to the quantum dot body, and at least some of the second ligands are the organic acid groups.

[0021] In some embodiments, the organic acid group has the general chemical formula C n H 2n-1 COOH or C6H5-C n H 2n -COOH, n is a positive integer greater than or equal to 1.

[0022] In some embodiments, the light-emitting device further includes: a hole injection layer located between the first electrode and the quantum dot light-emitting layer; a hole transport layer located between the hole injection layer and the quantum dot light-emitting layer; and a second electrode located on the side of the electron transport layer away from the first electrode.

[0023] In some embodiments, the quantum dot light-emitting layer includes a plurality of quantum dots, at least some of the plurality of quantum dots include a quantum dot body and a plurality of second ligands coordinated on the quantum dot body, a portion of the plurality of second ligands are the organic acid groups, the quantum dot light-emitting layer includes a red quantum dot light-emitting layer configured to emit red light, a green quantum dot light-emitting layer configured to emit green light, and a blue quantum dot light-emitting layer configured to emit blue light, the red quantum dot light-emitting layer, the green quantum dot light-emitting layer, and the blue quantum dot light-emitting layer are separated from each other, and the molar ratio of the organic acid groups in the red quantum dot light-emitting layer to the plurality of second ligands in the red quantum dot light-emitting layer is less than the molar ratio of the organic acid groups in the green quantum dot light-emitting layer to the plurality of second ligands in the green quantum dot light-emitting layer, and the molar ratio of the organic acid groups in the green quantum dot light-emitting layer to the plurality of second ligands in the green quantum dot light-emitting layer is less than the molar ratio of the organic acid groups in the blue quantum dot light-emitting layer to the plurality of second ligands in the blue quantum dot light-emitting layer.

[0024] In some embodiments, the molar ratio of the organic acid groups in the red quantum dot light-emitting layer to the multiple second ligands in the red quantum dot light-emitting layer is 0.1% to 10%, the molar ratio of the organic acid groups in the green quantum dot light-emitting layer to the multiple second ligands in the green quantum dot light-emitting layer is 0.1% to 20%, and the molar ratio of the organic acid groups in the blue quantum dot light-emitting layer to the multiple second ligands in the blue quantum dot light-emitting layer is 0.1% to 60%.

[0025] In some embodiments, the protective layer is located between the quantum dot light-emitting layer and the electron transport layer, and the protective layer includes a first protective layer, a second protective layer, and a third protective layer. The orthographic projection of the first protective layer on the first electrode at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode, the orthographic projection of the second protective layer on the first electrode at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode, the orthographic projection of the third protective layer on the first electrode at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode, the thickness of the first protective layer is greater than the thickness of the second protective layer, and the thickness of the second protective layer is greater than the thickness of the third protective layer.

[0026] In some embodiments, the electron transport layer includes a hydrophobic material or an alkaline material, and the electron transport layer includes a first electron transport layer, a second electron transport layer, and a third electron transport layer. The orthographic projection of the first electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode, the orthographic projection of the second electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode, and the orthographic projection of the third electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode. The content of the hydrophobic material or alkaline material in the first electron transport layer is greater than the content of the hydrophobic material or alkaline material in the second electron transport layer, and the content of the hydrophobic material or alkaline material in the second electron transport layer is greater than the content of the hydrophobic material or alkaline material in the third electron transport layer.

[0027] In some embodiments, the protective layer includes a salt layer, and the protective layer includes a first protective layer, a second protective layer, and a third protective layer. The orthographic projection of the first protective layer on the first electrode at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode, the orthographic projection of the second protective layer on the first electrode at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode, and the orthographic projection of the third protective layer on the first electrode at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode. The amount of salt substance in the first protective layer is greater than the amount of salt substance in the second protective layer, and the amount of salt substance in the second protective layer is greater than the amount of salt substance in the third protective layer.

[0028] According to another aspect of the present disclosure, a display device is provided, which includes the light emitting device described in any one of the above embodiments.

[0029] According to another aspect of the present disclosure, a method for preparing a light-emitting device is provided, comprising: providing a first electrode; treating an intermediate layer or a quantum dot solution with an organic acid to form a quantum dot light-emitting layer comprising an organic acid group; forming an electron transport layer on a side of the quantum dot light-emitting layer away from the first electrode; and forming a protective layer on a side of the quantum dot light-emitting layer away from the first electrode, the protective layer blocking the organic acid group from contacting the electron transport layer.

[0030] In some embodiments, a protective layer is formed on a side of the quantum dot light-emitting layer away from the first electrode, comprising: treating the surface of the quantum dot light-emitting layer with saturated steam comprising an alkaline material, causing the alkaline material to undergo an acid-base neutralization reaction with excess organic acid groups on the surface of the quantum dot light-emitting layer to form a salt layer.

[0031] In some embodiments, a protective layer is formed on the side of the quantum dot light-emitting layer away from the first electrode, including: providing an anti-contact layer on the side of the quantum dot light-emitting layer away from the first electrode, the material of the anti-contact layer including any one of a hydrophobic material, a silane coupling agent, and an epoxy resin; or providing an alkaline layer on the side of the quantum dot light-emitting layer away from the first electrode, the alkaline layer undergoing an acid-base neutralization reaction with excess organic acid groups on the surface of the quantum dot light-emitting layer to form a salt layer.

[0032] In some embodiments, an electron transport layer is formed on the side of the quantum dot light-emitting layer away from the first electrode and a protective layer is formed on the side of the quantum dot light-emitting layer away from the first electrode, including: doping an alkaline material into an electron transport material to form a mixed material, depositing the mixed material on the side of the quantum dot light-emitting layer away from the first electrode to form the electron transport layer, and the alkaline material in the mixed material undergoes an acid-base neutralization reaction with excess organic acid groups on the surface of the quantum dot light-emitting layer to form a salt layer; or depositing an electron transport material having a first ligand including an alkaline group on the side of the quantum dot light-emitting layer away from the first electrode to form the electron transport layer, and the alkaline groups on the first ligand undergo an acid-base neutralization reaction with excess organic acid groups on the surface of the quantum dot light-emitting layer to form a salt layer.

[0033] In some embodiments, the electron transport layer includes a first electron transport layer, a second electron transport layer, and a third electron transport layer, the quantum dot light-emitting layer includes a red quantum dot light-emitting layer, a green quantum dot light-emitting layer, and a blue quantum dot light-emitting layer, the orthographic projection of the first electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode, the orthographic projection of the second electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode, and the orthographic projection of the third electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode. The alkaline material is doped into the electron transport material to form a mixed material, and the mixed material is deposited on the side of the quantum dot light-emitting layer away from the first electrode to form the electron transport layer, including: doping the alkaline material and the electron transport material in a first molar ratio, a second molar ratio, and a third molar ratio to form a first mixed material, a second mixed material, and a third mixed material, respectively, and depositing the first mixed material, the second mixed material, and the third mixed material on the side of the quantum dot light-emitting layer away from the first electrode to form the first electron transport layer, the second electron transport layer, and the third electron transport layer, wherein the first molar ratio is greater than the second molar ratio, and the second molar ratio is greater than the third molar ratio.

[0034] In some embodiments, an electron transport layer is formed on a side of the quantum dot light-emitting layer away from the first electrode, and a protective layer is formed on a side of the quantum dot light-emitting layer away from the first electrode, including: wrapping an electron transport material with a surfactant, and depositing the electron transport material wrapped with the surfactant on a side of the quantum dot light-emitting layer away from the first electrode to form the electron transport layer; or, forming a surfactant on a side of the quantum dot light-emitting layer away from the first electrode, forming the electron transport layer on a side of the surfactant away from the first electrode, and the protective layer includes the surfactant.

[0035] In some embodiments, the intermediate layer or quantum dot solution is treated with an organic acid, comprising: forming the intermediate layer on the first electrode, the intermediate layer comprising quantum dots, treating the intermediate layer with saturated steam comprising the organic acid to form the quantum dot light-emitting layer on the first electrode; or forming the intermediate layer on the first electrode, the intermediate layer comprising quantum dots, applying an organic acid solution to a side of the intermediate layer away from the first electrode so that the intermediate layer is soaked in the organic acid solution, and removing the organic acid solution to form the quantum dot light-emitting layer on the first electrode; or preparing the quantum dot solution, the quantum dots comprising a quantum dot body and a second ligand coordinated to the quantum dot body, replacing at least some of the multiple second ligands with the organic acid group by ligand exchange to form a treated quantum dot solution, and depositing the treated quantum dot solution on the first electrode to form the quantum dot light-emitting layer; or mixing the organic acid with the quantum dot solution, and depositing the mixed solution on the first electrode to form the quantum dot light-emitting layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Hereinafter, various exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, in which:

[0037] FIG1 shows the change in current efficiency of a quantum dot light-emitting diode device as the storage time increases;

[0038] FIG2 shows the change in current efficiency of a quantum dot light-emitting diode device as the number of tests increases;

[0039] FIG3 shows the change in current efficiency of a quantum dot light-emitting diode device when the encapsulation glue contains acrylic acid and when it does not contain acrylic acid;

[0040] FIG4 shows the morphology of a quantum dot light-emitting diode device treated with acrylic acid and the morphology of a quantum dot light-emitting diode device not treated with acrylic acid;

[0041] FIG5 is a schematic cross-sectional view showing a partial structure of a light emitting device according to an embodiment of the present disclosure;

[0042] FIG6 is a schematic cross-sectional view showing a partial structure of a light emitting device according to an embodiment of the present disclosure;

[0043] FIG7 shows the general chemical formula of the first ligand of ZnO according to an embodiment of the present disclosure;

[0044] FIG8 shows a molecular structure of the group X in the chemical formula of FIG7 ;

[0045] FIG9 shows another molecular structure of the group X in the chemical formula of FIG7 ;

[0046] FIG10 shows another molecular structure of the group X in the chemical formula of FIG7 ;

[0047] FIG11 shows another molecular structure of the group X in the chemical formula of FIG7 ;

[0048] FIG12 is a schematic cross-sectional view showing a partial structure of a light emitting device according to an embodiment of the present disclosure;

[0049] FIG13 is a schematic cross-sectional view showing a partial structure of a light emitting device according to an embodiment of the present disclosure;

[0050] FIG14 is a schematic cross-sectional view showing a partial structure of a light emitting device according to an embodiment of the present disclosure;

[0051] FIG15 shows the brightness change of a red quantum dot light-emitting diode device as the operating time increases;

[0052] FIG16 shows the brightness change of a green quantum dot light-emitting diode device as the operating time increases;

[0053] FIG17 shows the brightness change of a blue quantum dot light-emitting diode device as the operating time increases;

[0054] FIG18 is a schematic cross-sectional view showing a partial structure of a light emitting device according to an embodiment of the present disclosure;

[0055] FIG19 shows a block diagram of a display device according to an embodiment of the present disclosure; and

[0056] FIG20 shows a flow chart of a method for preparing a light-emitting device according to an embodiment of the present disclosure.

[0057] It should be understood that the accompanying drawings are merely schematic illustrations of exemplary embodiments of the present disclosure and are not intended to limit the present disclosure and are not necessarily drawn to scale. In addition, in the accompanying drawings, identical or similar components are indicated by identical or similar reference numerals. DETAILED DESCRIPTION

[0058] The following will clearly describe the technical solutions in the embodiments of the present disclosure in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present disclosure.

[0059] Before formally describing the technical solutions of the embodiments of the present disclosure, the following explanations and definitions are given for the terms used in the embodiments of the present disclosure to help those skilled in the art to more clearly understand the technical solutions of the embodiments of the present disclosure.

[0060] In this document, the term "patterning process" or "patterning" includes but is not limited to processes such as film deposition, exposure, and development. After the "patterning process" or "patterning", the "layer" contains at least one pattern.

[0061] As used herein, terms such as "A is chemically bonded to B" mean that A and B are bonded to each other via a chemical bond. For example, A may be chemically bonded to an atom on the surface of B or to a ligand of B; similarly, B may be chemically bonded to an atom on the surface of A or to a ligand of A.

[0062] As used herein, terms such as “A and B are in physical contact” mean that there is no chemical bond between A and B, and A and B are only in physical contact. Terms such as “A and B are in chemical contact” mean that A and B are bonded or connected to each other through a chemical bond.

[0063] Quantum dots (QDs), as a new type of luminescent material, offer advantages such as high light color purity, high quantum efficiency, adjustable light color, and long lifespan, making them a research hotspot for new LED luminescent materials. Consequently, quantum dot light-emitting diodes (QLEDs), which use quantum dot materials as the light-emitting layer, have become a major research focus for new display devices.

[0064] However, aging is a problem that QLED devices cannot avoid. At a fixed current density, with increasing storage time or the number of tests, the brightness of a QLED device will first increase and then decrease. The device efficiency will also increase and then decrease accordingly. This period of increasing device efficiency is generally referred to as positive aging.

[0065] For example, Figure 1 shows the forward aging process of a QLED device. Curve E1 represents a QLED device that has been stored for one week, curve E2 represents a QLED device that has been stored for longer than curve E1, and curve E3 represents a QLED device that has been stored for longer than curve E2. As can be seen from Figure 1, the current efficiency of the QLED device increases with increasing storage time, which is consistent with the forward aging process of the QLED device.

[0066] For another example, Figure 2 shows the forward aging process of another QLED device. Curve F1 represents the result of the first test of the current efficiency of the QLED device, curve F2 represents the result of the second test of the current efficiency of the same QLED device, curve F3 represents the result of the third test of the current efficiency of the same QLED device, curve F4 represents the result of the fourth test of the current efficiency of the same QLED device, curve F5 represents the result of the fifth test of the current efficiency of the same QLED device, and curve F6 represents the result of the sixth test of the current efficiency of the same QLED device. As can be seen from Figure 2, as the number of tests increases, the current efficiency of the QLED device also increases accordingly, which is consistent with the forward aging process of the QLED device.

[0067] In conventional QLED devices, acrylic acid is usually added to the encapsulation glue to accelerate the forward aging process of the QLED device, so that the QLED device can quickly reach maximum efficiency.

[0068] For example, Figure 3 shows the current efficiency of two different QLED devices. Curve G1 represents a QLED device with acrylic acid in the encapsulant, while curve G2 represents a QLED device without acrylic acid in the encapsulant. Both QLED devices have a positive structure, with the encapsulant located between the encapsulating glass and the substrate, and both quantum dot light-emitting layers are designed to emit red light. As can be seen from Figure 3, by adding acrylic acid to the encapsulant, the current efficiency of the QLED device can be significantly improved, accelerating the forward aging process of the QLED device.

[0069] Although the forward aging process of QLED devices can be accelerated by introducing acrylic acid into the encapsulant, this solution will degrade the morphology of the QLED device, which is not conducive to the life of the QLED device. Figure 4 shows the morphology of the two QLEDs in Figure 3. It can be seen from Figure 4 that when the encapsulant is not treated with acrylic acid, the morphology of the QLED device is intact, but after the encapsulant is treated with acrylic acid, the morphology of the QLED device is severely degraded. Studies have found that acrylic acid in the encapsulant will damage the electron transport layer in the QLED device, and this damage will cause the morphology of the electron transport layer to degrade, which in turn causes the morphology of the QLED device to degrade.

[0070] Therefore, when processing QLED devices, while ensuring accelerated forward aging, certain measures need to be taken to avoid damage to the electron transport layer during the processing, thereby avoiding affecting the morphology of the QLED device.

[0071] In view of this, some embodiments of the present disclosure provide a type of light-emitting device, which includes: a first electrode, a quantum dot light-emitting layer located on the first electrode and including an organic acid group, an electron transport layer located on the side of the quantum dot light-emitting layer away from the first electrode, and a protective layer located on the side of the quantum dot light-emitting layer away from the first electrode, wherein the protective layer blocks the organic acid groups of the quantum dot light-emitting layer from contacting the electron transport layer.

[0072] The quantum dot light-emitting layer is treated with an organic acid, which helps accelerate the positive aging process of the light-emitting device, thereby improving the current efficiency of the light-emitting device. However, if the organic acid comes into contact with the electron transport layer, it will destroy the morphology of the electron transport layer, thereby degrading the overall morphology of the light-emitting device. In the embodiment of the present disclosure, a protective layer is provided to block the organic acid groups on the quantum dot light-emitting layer from contacting the electron transport layer, thereby preventing the morphology of the electron transport layer from being destroyed. In this way, the positive aging process of the light-emitting device can be accelerated, and the morphology of the light-emitting device can be prevented from being damaged, thereby preventing the life of the light-emitting device from being affected.

[0073] The protective layer can take many forms, for example, by providing a hydrophobic layer between the quantum dot light-emitting layer and the electron transport layer, with the hydrophobic layer acting as a protective layer; or by applying an alkaline material above the quantum dot light-emitting layer and allowing the alkaline material to react with the organic acid groups to form a salt layer, with the salt layer acting as a protective layer; or by adding a hydrophobic material or an alkaline material inside the electron transport layer, allowing the alkaline material to react with the organic acid groups to form a salt layer, with the hydrophobic material or salt layer acting as a protective layer; or by wrapping the electron transport layer with a surfactant, with the surfactant acting as a protective layer, etc. Accordingly, the protective layer can be located between the quantum dot light-emitting layer and the electron transport layer, between the quantum dot light-emitting layer and the electron transport layer, or inside the electron transport layer, etc.

[0074] Below, several embodiments are used to describe different arrangements of the protective layer in the light-emitting device.

[0075] FIG5 shows a light-emitting device 100 according to an embodiment of the present disclosure, comprising: a first electrode 101; a quantum dot light-emitting layer 102 comprising organic acid groups; a protective layer 103 located on a side of the quantum dot light-emitting layer 102 remote from the first electrode 101; and an electron transport layer 104 located on a side of the protective layer 103 remote from the first electrode 101. The protective layer 103 is located between the quantum dot light-emitting layer 102 and the electron transport layer 104 and is used to prevent the organic acid groups of the quantum dot light-emitting layer 102 from contacting the electron transport layer 104.

[0076] During the preparation of the light-emitting device 100, an organic acid (e.g., an unsaturated organic acid) can be used to treat the quantum dot solution or the quantum dot light-emitting layer so that the formed quantum dot light-emitting layer 102 includes an organic acid group. After the organic acid treatment, a portion of the organic acid groups are chemically bonded to the surface of the quantum dots to passivate the defects on the surface of the quantum dots. This portion of the organic acid groups plays a positive role and can promote the positive aging process of the light-emitting device 100; another portion of the organic acid groups is not chemically bonded to the surface of the quantum dots and has no passivation effect on the surface defects of the quantum dots. This portion of the organic acid groups is called "excess organic acid groups" and it is necessary to use an alkaline material to neutralize these excess organic acid groups to form a salt layer, or use a hydrophobic material to block these excess organic acid groups to prevent them from contacting the electron transport layer 104. The organic acid can be any appropriate organic acid, for example, including but not limited to acrylic acid, Lewis acid, butyric acid, acetic acid, propionic acid, isobutyric acid, benzoic acid, methacrylic acid, 3-butenoic acid, etc. These organic acids have carboxylic acids, delocalized π bonds, or H ions, and can directly passivate the quantum dot light-emitting layer and its surface defects through coordination, inhibiting surface exciton quenching and increasing the exciton radiative recombination efficiency, thereby significantly improving the positive aging effect of the light-emitting device 100. Organic acid groups can be detected in the quantum dot light-emitting layer 102 through testing methods such as infrared, mass spectrometry, and nuclear magnetic resonance.

[0077] There are many ways to treat quantum dot solutions or quantum dot light-emitting layers with organic acids, including but not limited to treating the quantum dot light-emitting layer with steam containing organic acid, soaking the quantum dot light-emitting layer with a solvent containing organic acid, adding organic acid molecules to the ligands of the quantum dots, adding organic acid molecules to the solvent of the quantum dots, etc. Quantum dots include a quantum dot body and a plurality of second ligands coordinated to the quantum dot body. After the quantum dots are treated in the above manner, a portion of the multiple second ligands on each quantum dot body are replaced with organic acid groups, and the organic acid groups are connected to the quantum dot body through coordination bonds. Therefore, the portion of organic acid groups that are chemically connected to the surface of the quantum dot and are used to passivate the surface defects of the quantum dot can be regarded as the replaced ligands on the quantum dot body. In some embodiments, the quantum dot light-emitting layer 102 includes a plurality of quantum dots, and at least some of the plurality of quantum dots include a quantum dot body and a second ligand coordinated to the quantum dot body, and at least some of the second ligands are the above-mentioned organic acid groups, and the general chemical formula of the second ligand is C n H 2n-1 COOH (unsaturated fatty carboxylic acid) or C6H5-C n H 2n -COOH (aromatic carboxylic acid), n is a positive integer greater than or equal to 1. During the preparation process, a portion of the second ligand can be replaced with an organic acid group by ligand exchange, that is, the organic acid group serves as the second ligand of the quantum dot body. n H 2n-1 COOH or C6H5-C n H 2n The number of C atoms in the -COOH group can be, for example, less than or equal to 8. This results in a smaller main chain structure, which facilitates access to the quantum dot ligand gap, thereby passivating the quantum dot light-emitting layer 102 and its surface defects, thereby suppressing surface exciton quenching. These methods of treating quantum dots with organic acids will be described in detail later and will not be further elaborated here.

[0078] In some embodiments, the protective layer 103 includes a salt layer. When the protective layer 103 is a salt layer, it can be formed in the following manner: when preparing the light-emitting device 100, an alkaline material is applied to the surface of the quantum dot light-emitting layer 102 away from the first electrode 101, or the surface of the quantum dot light-emitting layer 102 away from the first electrode 101 is treated with saturated steam including an alkaline material. Those organic acid groups that have been chemically bonded to the surface of the quantum dot will not react with the alkaline material, while the excess organic acid groups in the quantum dot light-emitting layer 102 will react with the alkaline material to produce an acid-base neutralization reaction to form a salt layer, i.e., the protective layer 103. Exemplarily, the protective layer 103 can be a carboxylate layer or a quaternary ammonium salt layer, depending on the type of organic acid and alkaline material used. For example, the organic acid can be acrylic acid, Lewis acid (Lewis acid), butyric acid, acetic acid, propionic acid, isobutyric acid, benzoic acid, methacrylic acid, 3-butenoic acid, etc. as described above, and the alkaline material can be an organic base, a quaternary ammonium base, a Lewis base (Lewis base), a metal oxide, etc. If the organic acid is acrylic acid and the alkaline material is Mg(OH)2, Al(OH)3, MgO, Al2O3, etc., the salt formed by the neutralization reaction of the organic acid and the alkaline material can be magnesium acrylate or aluminum acrylate, etc. If the organic acid is acrylic acid and the alkaline material is a quaternary ammonium base, the salt formed by the neutralization reaction of the organic acid and the alkaline material can be a quaternary ammonium salt. The alkaline material is usually a weak alkaline material and basically does not chemically react with the quantum dot material and the electron transport material. Therefore, even if the alkaline material contacts the quantum dot light-emitting layer 102 and the electron transport layer 104, the alkaline material will not affect the performance of the quantum dot light-emitting layer 102 and the electron transport layer 104.

[0079] In some embodiments, in addition to the salt layer, the protective layer 103 may also include unreacted alkaline material. To prevent the organic acid groups on the quantum dot light-emitting layer 102 from affecting the electron transport layer 104, an excess amount of alkaline material is typically applied to the surface of the quantum dot light-emitting layer 102 to ensure that the excess organic acid groups are reacted and consumed.

[0080] When an alkaline material is applied to the surface of the quantum dot light-emitting layer 102 away from the first electrode 101 or the surface of the quantum dot light-emitting layer 102 away from the first electrode 101 is treated with saturated steam including an alkaline material, the salt layer generated by the neutralization reaction of the organic acid group and the alkaline material is only in physical contact with the electron transport layer 104 and has no chemical bond connection with the electron transport layer 104.

[0081] In alternative embodiments, the protective layer 103 is an anti-contact layer made of a material different from that of the salt layer. The anti-contact layer physically blocks the organic acid groups in the quantum dot light-emitting layer 102 from contacting the electron transport layer 104. Exemplary materials for the anti-contact layer include, but are not limited to, hydrophobic materials, silane coupling agents, and epoxy resins. For example, the hydrophobic material may be hexamethyldisilazane (HMDS).

[0082] FIG6 illustrates another light-emitting device 200 according to an embodiment of the present disclosure. Aside from the arrangement of the protective layer 203, the light-emitting device 200 has substantially the same structure as the light-emitting device 100, and thus, the same reference numerals are used to designate the same components. Therefore, the detailed roles and functions of the components in FIG6 with the same reference numerals as those in FIG5 can be found in the description of FIG5 and will not be repeated here. For the sake of brevity, only the differences between the light-emitting device 200 and the light-emitting device 100 will be described below.

[0083] As shown in FIG6 , the light-emitting device 200 includes: a first electrode 101; a quantum dot light-emitting layer 102 including organic acid groups and located on the first electrode 101; a protective layer 203 located on the side of the quantum dot light-emitting layer 102 away from the first electrode 101; and an electron transport layer 104 located on the side of the quantum dot light-emitting layer 102 away from the first electrode 101. Unlike the protective layer 103, the protective layer 203 is not only located between the quantum dot light-emitting layer 102 and the electron transport layer 104, but is also partially located within the electron transport layer 104. Furthermore, the protective layer 203 can also be located on the side of the electron transport layer 104 close to the quantum dot light-emitting layer 102, and the protective layer 203 is in contact with the quantum dot light-emitting layer 102.

[0084] The protective layer 203 may include a salt layer or an anti-contact layer.

[0085] When the protective layer 203 includes a salt layer, it can be formed in the following two ways:

[0086] In one way, when preparing the electron transport layer 104, an alkaline material is doped into the electron transport material (such as ZnO) to form a mixed material, and the mixed material is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101 to form the electron transport layer 104. At the same time, the alkaline material in the mixed material reacts with the excess organic acid groups on the surface of the quantum dot light-emitting layer 102 to form an acid-base neutralization reaction to form a salt layer. The salt layer serves as a protective layer 203. In addition to being located between the quantum dot light-emitting layer 102 and the electron transport layer 104, it also exists inside the electron transport layer 104. The term "doping" can be understood as mixing alkaline materials between the ZnO particles. Since alkaline materials are mixed in the electron transport material by doping, in this case, the generated salt layer is only in physical contact with the electron transport layer 104 and is not connected by chemical bonds.

[0087] In another embodiment, when preparing the electron transport layer 104, an electron transport material (e.g., ZnO) is first prepared. The electron transport material includes a ZnO body and a first ligand coordinated to the ZnO body, wherein the first ligand includes a basic group. The electron transport material is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101. At this time, the basic group on the first ligand reacts with the excess organic acid group on the surface of the quantum dot light-emitting layer 102 to form a salt layer, i.e., a protective layer 203. In addition to being located between the quantum dot light-emitting layer 102 and the electron transport layer 104, the protective layer 203 also exists within the electron transport layer 104. The resulting electron transport layer 104 includes a ZnO body and a first ligand coordinated to the ZnO body (the structure corresponding to the reaction between the basic group on the first ligand and the organic acid group). The salt layer (i.e., the protective layer 203) is connected to at least some of the first ligand groups via chemical bonds, i.e., the salt layer is chemically connected to the electron transport layer 104.

[0088] In some embodiments, the electron transport layer 104 includes a first surface close to the quantum dot light-emitting layer 102 and a second surface away from the quantum dot light-emitting layer 102, and the salt layer (i.e., the protective layer 203) is connected to the first coordination group at the first surface through a chemical bond. This is because, during the preparation stage, the basic group on the first ligand on the first surface of the electron transport layer 104 close to the quantum dot light-emitting layer 102 usually undergoes an acid-base neutralization reaction with the excess organic acid group on the quantum dot light-emitting layer 102 to form a salt layer. Therefore, the salt layer is usually connected to the first coordination group at the first surface. The basic group on the first ligand on the second surface of the electron transport layer 104 away from the quantum dot light-emitting layer 102 usually does not participate in the reaction. Therefore, the first ligand on the second surface is still connected to the basic group.

[0089] FIG7 shows the general chemical formula of the first ligand of ZnO, which is The first ligand can be, for example, an alcohol amine. In this general chemical formula, the group R represents an alkyl chain, and the group X can be the structure shown in FIG8 Alternatively, it may be the structure shown in FIG. 9 Alternatively, it may be the structure shown in FIG. 10 Alternatively, it may be the structure shown in FIG. 11

[0090] When the protective layer 203 includes an anti-contact layer, it can be doped with an anti-contact material in ZnO to form a mixed material when preparing the electron transport layer 104, and then the mixed material is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101 to form an electron transport layer 104 and an anti-contact layer (i.e., protective layer 203). In this case, the protective layer 203 is in physical contact with the electron transport layer 104. Alternatively, an anti-contact material can be first introduced into the ligand of ZnO, and then the ZnO including the anti-contact material is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101 to form an electron transport layer 104 and an anti-contact layer (i.e., protective layer 203). In this case, the protective layer 203 is connected to the electron transport layer 104 through a chemical bond, and the two are in chemical contact. As the protective layer 203, in addition to being located between the quantum dot light-emitting layer 102 and the electron transport layer 104, the anti-contact layer also exists inside the electron transport layer 104. The anti-contact layer can reduce or even prevent contact between excess organic acid groups on the quantum dot light-emitting layer 102 and ZnO, acting as a physical barrier. Materials for the anti-contact layer include, but are not limited to, hydrophobic materials, silane coupling agents, and epoxy resins. For example, amino or hydroxyl groups in the anti-contact layer material can bind to surface sites on ZnO or can be incorporated into ZnO ligands.

[0091] FIG12 illustrates another light-emitting device 300 according to an embodiment of the present disclosure. Aside from the material of the protective layer 303, the light-emitting device 300 has substantially the same structure as the light-emitting device 100, and thus, the same reference numerals are used to designate the same components. Therefore, the detailed roles and functions of the components in FIG12 with the same reference numerals as those in FIG5 can be found in the description of FIG5 and will not be repeated here. For the sake of brevity, only the differences between the light-emitting device 300 and the light-emitting device 100 will be described below.

[0092] As shown in Figure 12, the light-emitting device 300 includes: a first electrode 101, a quantum dot light-emitting layer 102 located on the first electrode 101 and including an organic acid group, a protective layer 303 located on the side of the quantum dot light-emitting layer 102 away from the first electrode 101, and an electron transport layer 104 located on the side of the protective layer 303 away from the first electrode 101.

[0093] Unlike the protective layer 103 of the light-emitting device 100, the material of the protective layer 303 is not a salt layer or an anti-contact layer, but includes a surfactant to protect the electron transport layer 104 from the influence of the excess organic acid groups on the quantum dot light-emitting layer 102. In some embodiments, the surfactant wraps the electron transport layer 104. Exemplarily, the preparation process corresponding to this embodiment may be to form a surfactant layer on the side of the quantum dot light-emitting layer 102 away from the first electrode 101, the surfactant layer serves as the protective layer 303, and then form the electron transport layer 104 on the side of the protective layer 303 away from the first electrode 101. In some alternative embodiments, the surfactant wraps the zinc oxide nanoparticles in the electron transport layer 104. Exemplarily, the preparation process corresponding to this embodiment may be to first mix the surfactant and the zinc oxide nanoparticles to form a mixed material, and then deposit the mixed material on the side of the quantum dot light-emitting layer 102 away from the first electrode 101 to form the protective layer 303 and the electron transport layer 104, and the protective layer 303 includes a surfactant. For example, the surfactant can physically wrap the electron transport layer 104 without any chemical bond between the surfactant and the ZnO in the electron transport layer 104. The surfactant can form a vesicle-like structure to wrap the ZnO in the electron transport layer 104. While protecting the ZnO from the effects of the organic acid groups, it can also increase the distance between the ZnO particles, reduce electron injection, and reduce conductivity, thereby facilitating charge balance.

[0094] In some embodiments, the chemical formula of the surfactant can be represented by A + B - , where A + represents cations, B - represents an anion. For example, B - Can be selected from halogen ions, hydroxide ions, PF6 - 、BF4 - Any of A + The chemical formula can be expressed as C n H 2n+1 N(C m H 2m+1 )3 or C n H 2n+1 N(C m H 2m+1 )2(C m H 2m+1 )2NC n H 2n+1 , where n is any positive integer between 8 and 20, and m is any positive number between 0 and 4. n H 2n+1 N(C m H 2m+1) 3 can be a cation of a quaternary ammonium salt or a cation of a quaternary ammonium base, which contains one nitrogen atom and is a single-center ion; C n H 2n+1 N(C m H 2m+1 )2(C m H 2m+1 )2NC n H 2n+1 It can be a quaternary ammonium salt or quaternary ammonium base cation, which contains two nitrogen atoms and is a double-center ion. Surfactant molecules are quaternary ammonium salts or quaternary ammonium base molecules containing non-polar long chain ends.

[0095] Figure 13 shows another light-emitting device 400 according to an embodiment of the present disclosure, which is a variation of light-emitting device 300. In light-emitting device 300, the surfactant, for example, only wraps around the electron transport layer 104 or the zinc oxide nanoparticles from below. In light-emitting device 400, surfactant 403 wraps around the electron transport layer 104 or the zinc oxide nanoparticles from all sides. This better protects the electron transport layer 104 from the effects of the organic acid groups, further increases the distance between the ZnO particles, reduces electron injection, and thus facilitates charge balance.

[0096] FIG14 shows a schematic diagram of a partial structure of a light-emitting device 500 according to an embodiment of the present disclosure. As shown in FIG14 , in addition to the first electrode 101, the quantum dot light-emitting layer 102, the protective layer 103, and the electron transport layer 104, the light-emitting device 500 may further include: a hole injection layer 105 located between the first electrode 101 and the quantum dot light-emitting layer 102, a hole transport layer 106 located between the hole injection layer 105 and the quantum dot light-emitting layer 102, and a second electrode 107 located on the side of the electron transport layer 104 away from the first electrode 101. The first electrode 101 may be an anode, and the second electrode 107 may be a cathode. In this case, the light-emitting device 500 is a positive structure. It should be noted that although the protective layer shown in FIG14 is the protective layer 103, this is only an example. The protective layer in the light-emitting device 500 may also be the protective layer 203 or the protective layer 303 described above.

[0097] For example, the material of the first electrode 101 includes but is not limited to ITO, FTO, conductive polymers, opaque Al, Ag and other metal electrodes, the material of the hole injection layer 105 includes but is not limited to PEDOT:PSS, MoOx, NiOx, WOx, VOx, etc., the material of the hole transport layer 106 includes but is not limited to TFB, polyTPD, PVK, etc., the material of the protective layer 103 includes but is not limited to salt layer, anti-contact layer, surfactant, etc., the material of the electron transport layer 104 includes but is not limited to ZnO, and the material of the second electrode 107 includes but is not limited to Al, Ag, IZO, etc.

[0098] In some alternative embodiments, the light-emitting device 500 may also be an inverted structure. In the case of an inverted structure, the light-emitting device 500 includes a cathode, an electron transport layer, (optionally) a protective layer, a quantum dot light-emitting layer, a hole transport layer, a hole injection layer, an anode, etc. stacked in sequence. In the case of an inverted structure, the electron transport layer and / or the quantum dot light-emitting layer and / or the interface between the two may be subjected to the aforementioned treatment. In some embodiments, a sputtering process may be used to form the electron transport layer. The electron transport layer formed by the sputtering process is relatively dense and has strong resistance to solvent erosion. In this case, the treatment of the electron transport layer may be omitted (for example, there is no need to introduce alkaline materials or hydrophobic materials into the electron transport layer). Instead, a quantum dot light-emitting layer is directly prepared on the electron transport layer, and the quantum dot light-emitting layer is treated with an organic acid.

[0099] For the three types of light-emitting devices, namely, light-emitting devices that emit red light (referred to as red light-emitting devices), light-emitting devices that emit green light (referred to as green light-emitting devices), and light-emitting devices that emit blue light (referred to as blue light-emitting devices), their forward aging performance is generally different, which is mainly due to the different colors of quantum dot light-emitting layers. Generally speaking, the forward aging degree of red light-emitting devices is more serious. As the working time increases, their brightness will generally be more than 30% higher than the initial brightness, even reaching between 200% and 300%; the forward aging degree of green light-emitting devices is relatively light. As the working time increases, their brightness will generally increase by 10% to 50%; blue light-emitting devices show less positive aging trend. As the working time increases, their brightness generally does not increase, but decreases, that is, enters the negative aging process. For example, Figure 15 shows the brightness change of a red light-emitting device. It can be seen that as the working time increases, the brightness of the red light-emitting device first increases and then decreases (the current density remains unchanged), and the brightness can be increased to 200% or even more. Figure 16 shows the brightness change of a green light-emitting device. It can be seen that as the operating time increases, the brightness of the green light-emitting device first increases and then decreases (the current density remains unchanged), and the brightness can be increased to about 120%. Figure 17 shows the brightness change of a blue light-emitting device. It can be seen that as the operating time increases, the brightness of the blue light-emitting device gradually decreases (the current density remains unchanged), that is, the blue light-emitting device does not show positive aging over time.

[0100] In order to avoid obvious differences in the forward aging phenomenon of quantum dot light-emitting layers of different colors, the red, green and blue quantum dot light-emitting layers can be treated with organic acids of different contents.

[0101] Referring back to FIG. 14 , the light-emitting device 500 includes a red quantum dot light-emitting layer configured to emit red light R, a green quantum dot light-emitting layer configured to emit green light G, and a blue quantum dot light-emitting layer configured to emit blue light B. The red quantum dot light-emitting layer, the green quantum dot light-emitting layer, and the blue quantum dot light-emitting layer are separated from each other. The red quantum dot light-emitting layer may correspond to a red sub-pixel, the green quantum dot light-emitting layer may correspond to a green sub-pixel, and the blue quantum dot light-emitting layer may correspond to a blue sub-pixel. The quantum dot light-emitting layer 102 includes a plurality of quantum dots, each of which includes a quantum dot body and a plurality of second ligands coordinated to the quantum dot body, and a portion of the plurality of second ligands are the aforementioned organic acid groups. The second ligands other than the organic acid groups in the second ligands may be ligands of various suitable materials. Among them, the molar ratio of the organic acid group on each quantum dot in the red quantum dot light-emitting layer to the multiple second ligands is less than the molar ratio of the organic acid group on each quantum dot in the green quantum dot light-emitting layer to the multiple second ligands, and the molar ratio of the organic acid group on each quantum dot in the green quantum dot light-emitting layer to the multiple second ligands is less than the molar ratio of the organic acid group on each quantum dot in the blue quantum dot light-emitting layer to the multiple second ligands.

[0102] As previously mentioned, due to the quantum dot light-emitting layer, the forward aging degree of red light-emitting devices is greater than that of green light-emitting devices, and greater than that of blue light-emitting devices. The addition of an organic acid to the quantum dot light-emitting layer accelerates forward aging. Since the red quantum dot light-emitting layer has the strongest forward aging effect, it requires the least amount of organic acid, while the blue quantum dot light-emitting layer has the weakest forward aging effect, so it requires the highest amount of organic acid. Assuming that each quantum dot initially contains X moles of secondary ligands, after the quantum dots are treated with organic acid, approximately Y1 moles of the X moles of secondary ligands on the red quantum dot are replaced with organic acid groups, approximately Y2 moles of the X moles of secondary ligands on the green quantum dot are replaced with organic acid groups, and approximately Y3 moles of the X moles of secondary ligands on the blue quantum dot are replaced with organic acid groups, where Y1, Y2, and Y3 are all less than X, and Y1 / X < Y2 / X < Y3 / X.

[0103] In some embodiments, in the red quantum dot light-emitting layer, the molar ratio of the organic acid group on each quantum dot to the multiple second ligands is 0.1% to 10%, for example, 0.1%, 5%, 10%, etc.; in the green quantum dot light-emitting layer, the molar ratio of the organic acid group on each quantum dot to the multiple second ligands is 0.1% to 20%, for example, 10%, 15%, 20%, etc.; in the blue quantum dot light-emitting layer, the molar ratio of the organic acid group on each quantum dot to the multiple second ligands is 0.1% to 60%, for example, 30%, 45%, 60%, etc. It should be noted that although there are overlapping parts in the molar ratios of 0.1% to 10%, 0.1% to 20%, and 0.1% to 60%, these are only the possible molar ratio ranges of the organic acid group and the second ligand of each quantum dot. When the red quantum dot light-emitting layer, the green quantum dot light-emitting layer, and the blue quantum dot light-emitting layer are present in the same light-emitting device, the respective molar ratios of the organic acid group and the corresponding second ligand must also satisfy that the molar ratio of the organic acid group on each quantum dot in the red quantum dot light-emitting layer to the multiple second ligands is less than the molar ratio of the organic acid group on each quantum dot in the green quantum dot light-emitting layer to the multiple second ligands, and the molar ratio of the organic acid group on each quantum dot in the green quantum dot light-emitting layer to the multiple second ligands is less than the molar ratio of the organic acid group on each quantum dot in the blue quantum dot light-emitting layer to the multiple second ligands.

[0104] It should be noted that the above-mentioned molar ratio relationship or numerical range can be obtained by thermogravimetric analysis (TGA) and gas chromatography-mass spectrometry. For example, for a quantum dot light-emitting layer, the TGA method can be first used to analyze a quantum dot light-emitting layer comprising inorganic substances and a plurality of organic substances to obtain a plurality of organic substances, and then gas chromatography can be used to obtain a target organic substance from the plurality of organic substances. Then, the target atom or target functional group and other components can be determined from the target organic substance using methods such as mass spectrometry or nuclear magnetic resonance, thereby obtaining the molar ratio of the organic acid group to the second ligand. Gas chromatography and mass spectrometry are generally collectively referred to as gas chromatography-mass spectrometry.

[0105] In some embodiments, as shown in Figure 14, the protective layer 103 is located between the quantum dot light-emitting layer 102 and the electron transport layer 104, and the protective layer includes a first protective layer 1031, a second protective layer 1032, and a third protective layer 1033. The orthographic projection of the first protective layer 1031 on the first electrode 101 at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode 101, the orthographic projection of the second protective layer 1032 on the first electrode 101 at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode 101, and the orthographic projection of the third protective layer 1033 on the first electrode 101 at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode 101. The thickness T1 of the first protective layer 1031 is greater than the thickness T2 of the second protective layer 1032, and the thickness T2 of the second protective layer 1032 is greater than the thickness T3 of the third protective layer 1033. The reason for this design is that, in addition to protecting the ZnO from corrosion by excess organic acid groups on the quantum dot light-emitting layer 102, the protective layer 103 also acts as an electron blocker. Since the degree of electron excess in the red, green, and blue sub-pixels is red sub-pixels > green sub-pixels > blue sub-pixels, the thickness T1 of the first protective layer 1031 corresponding to the red sub-pixel > the thickness T2 of the second protective layer 1032 corresponding to the green sub-pixel > the thickness T3 of the third protective layer 1033 corresponding to the blue sub-pixel can be achieved. In this way, the electron blocking effect of the first protective layer 1031 can be > the electron blocking effect of the second protective layer 1032 > the electron blocking effect of the third protective layer 1033. By controlling the thickness of the protective layer 103 at the interface between the quantum dot light-emitting layer 102 and the electron transport layer 104, the performance of the light-emitting device 500 can be maintained, and electron injection can even be reduced, thereby improving carrier balance.

[0106] In some embodiments, for the red sub-pixel, a protective layer 103 can be set at the interface between the quantum dot light-emitting layer 102 and the electron transport layer 104, and alkaline materials and / or hydrophobic materials can be added to the electron transport layer 104 to further enhance the electron blocking effect of the protective layer at the red sub-pixel.

[0107] FIG18 shows a schematic diagram of a partial structure of a light-emitting device 600 according to another embodiment of the present disclosure. Except for the electron transport layer 104 and the protective layer 203, the light-emitting device 600 has substantially the same structure as the light-emitting device 500, and therefore the same reference numerals are used to refer to the same components. Therefore, the detailed roles and functions of the components in FIG18 with the same reference numerals as FIG14 can be referred to in the description of FIG14 and will not be repeated here. For the sake of brevity, only the differences between the light-emitting device 600 and the light-emitting device 500 are described below.

[0108] As shown in FIG18 , the light-emitting device 600 includes a first electrode 101, a hole injection layer 105, a hole transport layer 106, a quantum dot light-emitting layer 102, a protective layer 203, an electron transport layer 104, and a second electrode 107. The protective layer 203 can be formed in the same manner as the protective layer 203 of the light-emitting device 200 described in FIG6 . The electron transport layer 104 includes a hydrophobic material or an alkaline material. The electron transport layer 104 includes a first electron transport layer 1041, a second electron transport layer 1042, and a third electron transport layer 1043. The protective layer 203 includes a first protective layer 2031, a second protective layer 2032, and a third protective layer 2033. The orthographic projections of the first electron transport layer 1041 and the first protective layer 2031 on the first electrode 101 at least partially overlap with the orthographic projections of the red quantum dot light-emitting layer on the first electrode 101, the orthographic projections of the second electron transport layer 1042 and the second protective layer 2032 on the first electrode 101 at least partially overlap with the orthographic projections of the green quantum dot light-emitting layer on the first electrode 101, and the orthographic projections of the third electron transport layer 1043 and the third protective layer 2033 on the first electrode 101 at least partially overlap with the orthographic projections of the blue quantum dot light-emitting layer on the first electrode 101.

[0109] In addition to controlling the thickness of the protective layer 103 at the interface between the quantum dot light-emitting layer 102 and the electron transport layer 104 as shown in Figure 14, in Figure 18, during the preparation stage, the purpose of enhancing the electron blocking effect can also be achieved by controlling the amount of alkaline material or hydrophobic material added to the electron transport layer 104. Specifically, by making the content of hydrophobic material or alkaline material in the first electron transport layer 1041 corresponding to the red sub-pixel > the content of hydrophobic material or alkaline material in the second electron transport layer 1042 corresponding to the green sub-pixel > the content of hydrophobic material or alkaline material in the third electron transport layer 1043 corresponding to the blue sub-pixel, the protective layer 203 formed in this way has the amount of hydrophobic material or salt substance in the first protective layer 2031 corresponding to the red sub-pixel > the amount of hydrophobic material or salt substance in the second protective layer 2032 corresponding to the green sub-pixel > the amount of hydrophobic material or salt substance in the third protective layer 2033 corresponding to the blue sub-pixel. In this way, the electron blocking effect of the first protective layer 2031 can be achieved > the electron blocking effect of the second protective layer 2032 can be achieved > the electron blocking effect of the third protective layer 2033.

[0110] The content of the hydrophobic material or alkaline material in the first electron transport layer 1041, the second electron transport layer 1042, and the third electron transport layer 1043 can be determined by elemental analysis, for example. The amount of the salt in the first protective layer 2031, the second protective layer 2032, and the third protective layer 2033 can also be determined by elemental analysis.

[0111] It should be noted that, in the absence of contradiction, the arrangement of the protective layer 103 and the electron transport layer 104 in the light-emitting device 500 and the arrangement of the protective layer 203 and the electron transport layer 104 in the light-emitting device 600 can be combined with each other.

[0112] The quantum dot light-emitting layer 102 in the light-emitting device described in various embodiments of the present disclosure may be any appropriate quantum dot, including but not limited to: any of group IIB-VIA quantum dots, group IIIA-VA quantum dots, group IVA-VIA quantum dots, core-shell quantum dots, and ABX3 type perovskite quantum dots. In the ABX3 type perovskite quantum dot, A is CH3NH3 + (methylamine), NH2CH=NH2(formamidine) and Cs + One or more of, B is Pb 2+ and Sn 2+ One or two of the following, X is Cl - Br - and I - One or more of the ABX3 type perovskite quantum dots include CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3PbI3, CsPbBr3, CsPbCl3 and CsPbI3.

[0113] Exemplarily, the IIB-VIA group quantum dots are selected from: binary compounds such as one or more of CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, and MgS; ternary compounds such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZn Te, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or mixtures thereof; and quaternary compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or mixtures thereof, but are not limited thereto.

[0114] The IIIA-VA group quantum dots are selected from: binary compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or mixtures thereof; ternary compounds such as GaNPs, GaNAs, GaNSb, GaPAs, GaPSb, AlNPs, AlNAs, AlNSb, AlPAs, AlPSb, InNPs, InNAs, InNSb, InPAs, InPSb, or mixtures thereof; and quaternary compounds such as GaAlNPs, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNPs, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNPs, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or mixtures thereof, but are not limited thereto.

[0115] Group IVA-VIA quantum dots are selected from, but are not limited to, binary compounds such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or mixtures thereof; ternary compounds such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or mixtures thereof; and quaternary compounds such as SnPbSSe, SnPbSeTe, SnPbSTe, or mixtures thereof. Group IVA-VIA quantum dots are selected, for example, from elemental (mono) semiconductors such as Si, Ge, or mixtures thereof; and binary semiconductor compounds such as SiC, SiGe, and mixtures thereof.

[0116] Core-shell quantum dots are structures where one material is the core and the other is the shell. For example, a CdS / ZnS quantum dot is a quantum dot where the core is CdS and the shell is ZnS.

[0117] In some other embodiments, the quantum dots may be other nanoscale materials, such as nanorods, nanosheets, etc. The components of other nanoscale materials may include at least one of CdS, CdSe, CdTe, ZnSe, InP, PbS, CuInS2, ZnO, CsPbCl3, CsPbBr3, CsPhI3, CdS / ZnS, CdSe / ZnS, ZnSe, InP / ZnS, PbS / ZnS, InAs, InGaAs, InGaN, GaNk, ZnTe, Si, Ge, and C.

[0118] For example, quantum dots can include cadmium-free (Cd) quantum dots. Cadmium-free quantum dots are quantum dots that do not include cadmium (Cd). Cadmium (Cd) can cause serious environmental / health problems, so non-cadmium-based quantum dots can be effectively used.

[0119] Figure 19 shows a block diagram of a display device 700 according to an embodiment of the present disclosure. The display device 700 includes a plurality of light-emitting devices. In some embodiments, each light-emitting device includes a quantum dot light-emitting layer that emits a single color of light. For example, some light-emitting devices include a red quantum dot light-emitting layer and are used to emit red light; some light-emitting devices include a green quantum dot light-emitting layer and are used to emit green light; and some light-emitting devices include a blue quantum dot light-emitting layer and are used to emit blue light. In some alternative embodiments, each light-emitting device includes a quantum dot light-emitting layer that emits light of different colors. For example, each light-emitting device includes a quantum dot light-emitting layer that emits three different colors of light: red, green, and blue. Of course, the display device 700 also includes other components not shown, for example, it may include a driving circuit for providing an electrical signal to the light-emitting device to drive the light-emitting device to emit light. The display device 700 may also include structures such as a circuit board and / or an integrated circuit (IC).

[0120] The display device 700 can be any product or component based on quantum dots for display, such as a mobile phone, a tablet computer, a television, a monitor, a laptop computer, a digital photo frame, or a navigator.

[0121] The display device 700 can have substantially the same technical effects as the light-emitting device described in the previous embodiment. Therefore, for the purpose of brevity, a repeated description will not be given here.

[0122] FIG20 shows a flow chart of a method 800 for preparing a light emitting device. As shown in FIG20 , the method 800 includes the following steps:

[0123] S801: providing a first electrode.

[0124] S802: treating the intermediate layer or the quantum dot solution with an organic acid to form a quantum dot light-emitting layer including organic acid groups on the first electrode.

[0125] The "intermediate layer" here refers to a film layer in a certain state before the final formation of the quantum dot light-emitting layer 102, in the form of a "layer." The "quantum dot solution" refers to a solution containing quantum dots, which is used to form the quantum dot light-emitting layer.

[0126] S803: forming an electron transport layer on a side of the quantum dot light-emitting layer away from the first electrode.

[0127] S804: forming a protective layer on a side of the quantum dot light-emitting layer away from the first electrode, wherein the protective layer blocks the organic acid groups on the quantum dot light-emitting layer from contacting with the electron transport layer.

[0128] In method 800, a protective layer is formed to block the organic acid groups on the quantum dot light-emitting layer from contacting the electron transport layer, thereby preventing damage to the electron transport layer's morphology. This accelerates the positive aging process of the light-emitting device while preventing damage to the device's morphology and thus reducing its lifespan.

[0129] Below, several embodiments or examples are used to describe different methods for preparing light-emitting devices in more detail.

[0130] Method 1

[0131] First, a first electrode 101 is deposited on a substrate. The substrate may be made of glass or flexible PET, for example. The first electrode 101 may be made of transparent ITO, FTO, a conductive polymer, or an opaque metal electrode such as Al or Ag.

[0132] Then, a hole injection layer 105 is deposited on the first electrode 101 by spin coating or magnetron sputtering. The material of the hole injection layer 105 includes, but is not limited to, PEDOT:PSS, MoOx, NiOx, WOx, VOx, etc. Exemplarily, the thickness of the hole injection layer 105 can be between 20 and 100 nm.

[0133] Then, a hole transport layer 106 is deposited on the side of the hole injection layer 105 away from the first electrode 101. The material of the hole transport layer 106 includes but is not limited to TFB, polyTPD, PVK and the like.

[0134] Afterwards, a red quantum dot intermediate layer is deposited on the side of the hole transport layer 106 away from the first electrode 101, and then the red quantum dot intermediate layer is treated with saturated steam including an organic acid. The treatment time is a first time length, and the first time length can be, for example, 0 to 10 minutes. In the saturated steam atmosphere including an organic acid, the proportion of organic acid can be 1% to 100%. The organic acid can be an unsaturated organic acid, including but not limited to acrylic acid, Lewis acid, butyric acid, acetic acid, propionic acid, isobutyric acid, benzoic acid, methacrylic acid, 3-butenoic acid, etc. After treatment with an organic acid, organic acid groups can be detected in the red quantum dot light-emitting layer by testing methods such as infrared, mass spectrometry, and nuclear magnetic resonance. Exemplarily, the red quantum dot intermediate layer can be cross-linked and developed to form a pattern, and then the patterned layer can be treated with saturated steam including an organic acid; or the red quantum dot intermediate layer can be treated with saturated steam including an organic acid first, and then cross-linked and developed to form a pattern. When the red quantum dot light emitting layer is patterned, the hole transport layer 106 below is also patterned, so that only the patterned hole transport layer 106 remains at the red sub-pixel. In some embodiments, the thickness of the red quantum dot light emitting layer is 20-50 nm.

[0135] Then, a hole transport layer is deposited.

[0136] Next, a green quantum dot intermediate layer is deposited and treated with saturated vapor containing an organic acid for a second duration, which can be, for example, 0 to 30 minutes. By patterning the green quantum dot intermediate layer and the hole transport layer, a stacked hole transport layer pattern and a green quantum dot light-emitting layer can be formed within the green sub-pixel. In some embodiments, the green quantum dot light-emitting layer has a thickness of 20 to 50 nm.

[0137] Afterwards, a hole transport layer is deposited.

[0138] Next, a blue quantum dot intermediate layer is deposited and treated with saturated vapor containing an organic acid for a third duration, which can be, for example, 0 to 60 minutes. By patterning the blue quantum dot intermediate layer and the hole transport layer, a stacked hole transport layer pattern and a blue quantum dot light-emitting layer can be formed within the blue sub-pixel. In some embodiments, the blue quantum dot light-emitting layer has a thickness of 20 to 50 nm.

[0139] After organic acid treatment, a portion of the organic acid groups are chemically bonded to the surface of the red, green, and blue quantum dots, thereby passivating defects on the quantum dot surface. This portion of organic acid groups plays a positive role and can promote the positive aging process of the light-emitting device. Another portion of organic acid groups is not chemically bonded to the surface of the red, green, and blue quantum dots and has no passivating effect on the surface defects of the quantum dots. This portion of organic acid groups is referred to as "redundant organic acid groups." For example, before organic acid treatment, the quantum dots include a quantum dot body and multiple secondary ligands coordinated to the quantum dot body. After organic acid treatment according to method one, a portion of the multiple secondary ligands on each quantum dot body are replaced with organic acid groups. The organic acid groups are connected to the quantum dot body through coordination bonds. Therefore, the portion of organic acid groups chemically bonded to the quantum dot surface and used to passivate defects on the quantum dot surface can be regarded as the replaced ligands on the quantum dot body.

[0140] Next, the surface of the red, green, and blue quantum dot light-emitting layer 102 away from the first electrode 101 is treated with saturated steam containing an alkaline material, causing the alkaline material to undergo an acid-base neutralization reaction with excess organic acid groups on the surface of the red, green, and blue quantum dot light-emitting layer 102, thereby forming a salt layer, i.e., a protective layer 103, on the side of the red, green, and blue quantum dot light-emitting layer 102 away from the first electrode 101. The organic acid groups that have been chemically bonded to the surface of the quantum dots will not react with the alkaline material, while the excess organic acid groups in the quantum dot light-emitting layer 102 will undergo an acid-base neutralization reaction with the alkaline material to form a salt layer, i.e., the protective layer 103. Exemplarily, the protective layer 103 can be a carboxylate layer or a quaternary ammonium salt layer, depending on the type of organic acid and alkaline material used. For example, the organic acid can be acrylic acid, Lewis acid (lewis acid), butyric acid, acetic acid, propionic acid, isobutyric acid, benzoic acid, methacrylic acid, 3-butenoic acid, etc. as described above, and the alkaline material can be an organic base, a quaternary ammonium base, a Lewis base (lewis base), a metal oxide, etc. If the organic acid is acrylic acid and the alkaline material is Mg (OH) 2, Al (OH) 3, MgO, Al 2 O 3, etc., the salt generated by the neutralization reaction of the organic acid and the alkaline material can be magnesium acrylate or aluminum acrylate, etc. If the organic acid is acrylic acid and the alkaline material is a quaternary ammonium base, the salt generated by the neutralization reaction of the organic acid and the alkaline material can be a quaternary ammonium salt substance. The alkaline material is generally a weakly alkaline material and does not react chemically with the quantum dot material and the electron transport material substantially. Therefore, even if the alkaline material contacts the quantum dot light-emitting layer 102, the alkaline material will not affect the performance of the quantum dot light-emitting layer 102.

[0141] Then, an electron transport material is deposited on the side of the protective layer 103 away from the first electrode 101 to form an electron transport layer 104. The electron transport material includes but is not limited to ZnO. The electron transport material can be deposited in different sub-pixels by inkjet printing, photolithography, etc.

[0142] Finally, the second electrode 107 is deposited on the side of the electron transport layer 104 away from the first electrode 101. The material of the second electrode 107 includes but is not limited to Al, Ag, IZO, etc., and the thickness of the second electrode 107 can be 10-100 nm.

[0143] In method one, as the treatment time of quantum dot light-emitting layers of different colors varies, the organic acid content on their surfaces will also vary. For example, if the first duration is less than the second duration and less than the third duration, the molar ratio of the organic acid group on each quantum dot in the red quantum dot light-emitting layer to the initial second ligand (untreated with organic acid) is less than the molar ratio of the organic acid group on each quantum dot in the green quantum dot light-emitting layer to the initial second ligand (untreated with organic acid) and less than the molar ratio of the organic acid group on each quantum dot in the blue quantum dot light-emitting layer to the initial second ligand (untreated with organic acid). As mentioned above, due to the quantum dot light-emitting layer, the forward aging degree of the red light-emitting device is greater than that of the green light-emitting device and greater than that of the blue light-emitting device. The purpose of adding organic acid to the quantum dot light-emitting layer is to accelerate forward aging. Since the red quantum dot light-emitting layer has the strongest forward aging effect, the amount of organic acid required to be added is the least, while the blue quantum dot light-emitting layer has the weakest forward aging effect, so the amount of organic acid required to be added is the highest.

[0144] In short, in method one, the quantum dot intermediate layer is treated with saturated steam including an organic acid so that the organic acid is connected to the quantum dots through chemical bonds, and the surface of the formed quantum dot light-emitting layer is treated with saturated steam including an alkaline material. The alkaline material undergoes an acid-base neutralization reaction with the excess organic acid groups on the quantum dot light-emitting layer 102 to form a protective layer 103 between the quantum dot light-emitting layer 102 and the electron transport layer 104.

[0145] Method 2:

[0146] Compared to method 1, the remaining processes remain unchanged. The only difference is that, when preparing the red, green, and blue quantum dot light-emitting layers, instead of treating the quantum dot intermediate layer with saturated vapor containing an organic acid, the organic acid is mixed with the corresponding quantum dot solution, and then the mixed solution is deposited on the first electrode 101 to form the red, green, and blue quantum dot light-emitting layers, respectively. After adding the organic acid to the quantum dot solution, some defects will appear on the quantum dot surface, or the surface atoms will be connected to the organic acid molecules through chemical bonds.

[0147] Before being treated with organic acid, the quantum dots include a quantum dot body and a plurality of second ligands coordinated on the quantum dot body. After being treated with organic acid in method 2, a portion of the plurality of second ligands on each quantum dot body are replaced with organic acid groups, and the organic acid groups are connected to the quantum dot body through coordination bonds. Therefore, the portion of the organic acid groups that are connected to the surface of the quantum dot through chemical bonds and are used to passivate the surface defects of the quantum dot can be regarded as the replaced ligands on the quantum dot body.

[0148] In some embodiments, the content of the organic acid varies in different quantum dot solutions. For example, in a red quantum dot solution, the molar ratio of the organic acid to the second ligand can be 0.1 to 10%, such as 0.1%, 5%, or 10%. In a green quantum dot solution, the molar ratio of the organic acid to the second ligand can be 0.1 to 20%, such as 10%, 15%, or 20%. In a blue quantum dot solution, the molar ratio of the organic acid to the second ligand can be 0.1 to 60%, such as 30%, 45%, or 60%.

[0149] The solvent of the organic acid can be the same as the quantum dot solvent. Organic acids generally have strong solubility and can be dissolved in both polar solvents and non-polar solvents.

[0150] In short, in method two, organic acid molecules are added to the quantum dot solution so that the organic acid is connected to the quantum dots through chemical bonds, and the surface of the formed quantum dot light-emitting layer is treated with saturated steam including an alkaline material. The alkaline material undergoes an acid-base neutralization reaction with the excess organic acid groups on the quantum dot light-emitting layer 102 to form a protective layer 103 between the quantum dot light-emitting layer 102 and the electron transport layer 104.

[0151] Method 3

[0152] Compared to method 1, the remaining processes remain unchanged, with the only difference being that, when preparing the red, green, and blue quantum dot light-emitting layers, a quantum dot intermediate layer of the corresponding colors is first formed on the first electrode 101, and then an organic acid solution is applied to the side of the intermediate layer away from the first electrode 101 so that the quantum dot intermediate layer is soaked in the organic acid solution. The organic acid solution is then removed, thereby forming a red, green, and blue quantum dot light-emitting layer comprising organic acid groups on the first electrode 101. Exemplarily, a quantum dot intermediate layer of the corresponding colors is first formed on the first electrode 101, and then an organic acid solution, such as an ethanol solution of acrylic acid, is dropwise added onto the quantum dot intermediate layer so that the quantum dot intermediate layer is soaked in the ethanol solution of acrylic acid. The ethanol solution of acrylic acid is then spin-coated and dried, thereby forming a red, green, and blue quantum dot light-emitting layer comprising organic acid groups on the first electrode 101.

[0153] Before being treated with organic acid, the quantum dots include a quantum dot body and multiple second ligands coordinated on the quantum dot body. After the organic acid treatment of method three, a portion of the multiple second ligands on each quantum dot body are replaced by organic acid groups, and the organic acid groups are connected to the quantum dot body through coordination bonds. Therefore, the portion of the organic acid groups that are connected to the surface of the quantum dot through chemical bonds and are used to passivate the surface defects of the quantum dot can be regarded as the replaced ligands on the quantum dot body.

[0154] In short, in method three, the quantum dot intermediate layer is soaked in an organic acid solvent so that the organic acid is connected to the quantum dots through chemical bonds, and the surface of the formed quantum dot light-emitting layer is treated with saturated steam including an alkaline material. The alkaline material undergoes an acid-base neutralization reaction with the excess organic acid groups on the quantum dot light-emitting layer 102, thereby forming a protective layer 103 between the quantum dot light-emitting layer 102 and the electron transport layer 104.

[0155] Method 4

[0156] Compared to method 1, the remaining processes remain unchanged, differing only in that, during the preparation of the red, green, and blue quantum dot light-emitting layers, a portion of the quantum dot ligands are replaced with organic acids through ligand exchange. Specifically, a quantum dot solution is first prepared. The quantum dots include a quantum dot body and secondary ligands coordinated to the quantum dot body. Through ligand exchange, at least some of the multiple secondary ligands are replaced with organic acid groups to form a treated quantum dot solution. The treated quantum dot solution is then deposited on the first electrode 101 to form the red, green, and blue quantum dot light-emitting layers, respectively.

[0157] In one example, the ligand exchange method can be as follows: first, ethanol is added to a non-polar solution of quantum dots (such as octane) to precipitate the quantum dots, and then the quantum dot powder is placed in an ethanol solution including a photosensitive ligand and an unsaturated organic acid to perform ligand exchange, and then washed with ethanol 1 to 3 times. Finally, the above solution is redissolved in the amphoteric solution PGMEA.

[0158] The general chemical formula of the second ligand of the quantum dot can be C n H 2n-1 COOH (unsaturated fatty carboxylic acid) or C6H5-C n H 2n -COOH (aromatic carboxylic acid), n is a positive integer greater than or equal to 1. The material of the second ligand can be butyric acid, acetic acid, propionic acid, isobutyric acid, acrylic acid, benzoic acid, methacrylic acid, 3-butenoic acid, etc. n H 2n-1 COOH or C6H5-C n H 2nIn -COOH, the number of C atoms can be, for example, less than or equal to 8. In this way, the main chain structure is smaller, which is conducive to entering the ligand gap of the quantum dot, thereby passivating the quantum dot light-emitting layer and its surface defects and inhibiting surface exciton quenching.

[0159] Before being treated with organic acid, the quantum dots include a quantum dot body and a plurality of second ligands coordinated on the quantum dot body. After being treated with organic acid in method four, a portion of the plurality of second ligands on each quantum dot body are replaced with organic acid groups, and the organic acid groups are connected to the quantum dot body through coordination bonds. Therefore, the portion of the organic acid groups that are chemically bonded to the surface of the quantum dot and used to passivate the surface defects of the quantum dot can be regarded as the replaced ligands on the quantum dot body.

[0160] In short, in method four, organic acid molecules are introduced into the quantum dot ligands so that the organic acid is connected to the quantum dots through chemical bonds, and the surface of the formed quantum dot light-emitting layer is treated with saturated steam including an alkaline material. The alkaline material undergoes an acid-base neutralization reaction with the excess organic acid groups on the quantum dot light-emitting layer 102 to form a protective layer 103 between the quantum dot light-emitting layer 102 and the electron transport layer 104.

[0161] Methods 1, 2, 3, and 4 utilize different methods to treat the quantum dot intermediate layer or quantum dot solution, allowing the organic acid groups to be chemically bonded to the quantum dot surface. In the quantum dot light-emitting layers obtained after treatment using methods 1, 2, 3, and 4, a portion of the multiple secondary ligands on each quantum dot body are replaced with organic acid groups. Therefore, the chemical structures of the quantum dot light-emitting layers obtained using methods 1, 2, 3, and 4 can be considered essentially identical.

[0162] Method 5

[0163] In method five, the treatment of the quantum dot light-emitting layer can adopt any one of the above methods one, two, three, and four, and the preparation method of the electron transport layer 104 is different from that of method one. In method six, when preparing the electron transport layer 104, the alkaline material is first doped into the electron transport material ZnO to form a mixed material, and then the mixed material is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101. The alkaline material in the mixed material reacts with the excess organic acid groups on the surface of the quantum dot light-emitting layer 102 to form a salt layer, i.e., a protective layer 203. In some embodiments, the molar ratio of the alkaline material to ZnO in the mixed material is 0.1% to 60%, for example, 0.1%, 30%, 60%, etc. The alkaline material can be, for example, an organic base or a Lewis base. The preparation method and process of other film layers are the same as those of method one.

[0164] In some embodiments, the electron transport layer 104 includes a first electron transport layer 1041, a second electron transport layer 1042, and a third electron transport layer 1043, the quantum dot light-emitting layer includes a red quantum dot light-emitting layer, a green quantum dot light-emitting layer, and a blue quantum dot light-emitting layer, the orthographic projection of the first electron transport layer 1041 on the first electrode 101 at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode 101, the orthographic projection of the second electron transport layer 1042 on the first electrode 101 at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode 101, and the orthographic projection of the third electron transport layer 1043 on the first electrode 101 at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode 101. Wherein, the alkaline material is doped into the electron transport material to form a mixed material, and the mixed material is deposited on the side of the quantum dot light-emitting layer away from the first electrode to form an electron transport layer, including: doping the alkaline material and the electron transport material ZnO at a first molar ratio, a second molar ratio, and a third molar ratio to form a first mixed material, a second mixed material, and a third mixed material, and depositing the first mixed material, the second mixed material, and the third mixed material on the side of the quantum dot light-emitting layer 102 away from the first electrode 101 to form a first electron transport layer 1041, a second electron transport layer 1042, and a third electron transport layer 1043, wherein the first molar ratio is greater than the second molar ratio, and the second molar ratio is greater than the third molar ratio. Exemplarily, the content of the alkaline material in the first electron transport layer 1041 is greater than the content of the alkaline material in the second electron transport layer 1042, and the content of the alkaline material in the second electron transport layer 1042 is greater than the content of the alkaline material in the third electron transport layer 1043.

[0165] The protective layer 203 formed in this way has the following order: the amount of salt substance in the first protective layer 2031 corresponding to the red sub-pixel > the amount of salt substance in the second protective layer 2032 corresponding to the green sub-pixel > the amount of salt substance in the third protective layer 2033 corresponding to the blue sub-pixel. In this way, the electron blocking effect of the first protective layer 2031 can be achieved > the electron blocking effect of the second protective layer 2032 > the electron blocking effect of the third protective layer 2033, which is beneficial to enhancing the electron blocking effect at the red sub-pixel.

[0166] The protective layer 203 formed by method five is not only located between the quantum dot light-emitting layer 102 and the electron transport layer 104, but also located within the electron transport layer 104. Since the alkaline material is doped in ZnO but not chemically bonded to ZnO, the protective layer 203 is in physical contact with the electron transport layer 104.

[0167] Method 6

[0168] In method six, the treatment of the quantum dot light-emitting layer can adopt any one of the above methods one, two, three, and four, and the method for forming the protective layer 103 is different from that in method one. In method six, an anti-contact layer is provided on the side of the quantum dot light-emitting layer 102 away from the first electrode 101. The material of the anti-contact layer can be any one of the hydrophobic materials HMDS, silane coupling agent, and epoxy resin, and the anti-contact layer serves as the protective layer 103; or, an alkaline layer is provided on the side of the quantum dot light-emitting layer 102 away from the first electrode 101. The alkaline layer reacts with the excess organic acid groups on the surface of the quantum dot light-emitting layer 102 to form a salt layer, and the salt layer serves as the protective layer 103. The protective layer 103 is located between the quantum dot light-emitting layer 102 and the electron transport layer 104. The preparation method and process of other film layers are the same as those in method one.

[0169] Method 7

[0170] In method seven, the quantum dot light-emitting layer can be treated using any of the above methods one, two, three, and four. The preparation method of the electron transport layer 104 is different from that of method one. In method seven, when preparing the electron transport layer 104, an electron transport material ZnO having a first ligand including a basic group is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101. The basic groups on the first ligand react with the excess organic acid groups on the surface of the quantum dot light-emitting layer 102 to form a salt layer, i.e., a protective layer 203. The alkaline material can be, for example, an organic base or a Lewis base. The preparation method and process of the other film layers are the same as those of method one.

[0171] The general chemical formula of the first ligand of ZnO is The first ligand can be, for example, an alcohol amine. In this general chemical formula, the group R represents an alkyl chain, and the group X can be the structure shown in FIG8 Alternatively, it may be the structure shown in FIG. 9 Alternatively, it may be the structure shown in FIG. 10 Alternatively, it may be the structure shown in FIG. 11

[0172] In some embodiments, the electron transport layer 104 includes a first surface close to the quantum dot light-emitting layer 102 and a second surface away from the quantum dot light-emitting layer 102, and the salt layer (i.e., the protective layer 203) is connected to the first coordination group at the first surface through a chemical bond. This is because, during the preparation stage, the basic group on the first ligand on the first surface of the electron transport layer 104 close to the quantum dot light-emitting layer 102 usually undergoes an acid-base neutralization reaction with the excess organic acid group on the quantum dot light-emitting layer 102 to form a salt layer. Therefore, the salt layer is usually connected to the first coordination group at the first surface. The basic group on the first ligand on the second surface of the electron transport layer 104 away from the quantum dot light-emitting layer 102 usually does not participate in the reaction. Therefore, the first ligand on the second surface is still connected to the basic group.

[0173] In some embodiments, the electron transport layer 104 includes a first electron transport layer 1041, a second electron transport layer 1042, and a third electron transport layer 1043, the quantum dot light-emitting layer includes a red quantum dot light-emitting layer, a green quantum dot light-emitting layer, and a blue quantum dot light-emitting layer, the orthographic projection of the first electron transport layer 1041 on the first electrode 101 at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode 101, the orthographic projection of the second electron transport layer 1042 on the first electrode 101 at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode 101, and the orthographic projection of the third electron transport layer 1043 on the first electrode 101 at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode 101. In which, the electron transport material ZnO having a first ligand including a basic group is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101, including: depositing the first electron transport material, the second electron transport material, and the third electron transport material on the side of the quantum dot light-emitting layer 102 away from the first electrode 101 to form a first electron transport layer 1041, a second electron transport layer 1042, and a third electron transport layer 1043, respectively, wherein the ratio of the basic group in the first electron transport material ZnO to the first ligand is a first molar ratio, the ratio of the basic group in the second electron transport material ZnO to the first ligand is a second molar ratio, and the ratio of the basic group in the third electron transport material ZnO to the first ligand is a third molar ratio, the first molar ratio is greater than the second molar ratio, and the second molar ratio is greater than the third molar ratio.

[0174] The protective layer 203 formed in this way has the following order: the amount of salt substance in the first protective layer 2031 corresponding to the red sub-pixel > the amount of salt substance in the second protective layer 2032 corresponding to the green sub-pixel > the amount of salt substance in the third protective layer 2033 corresponding to the blue sub-pixel. In this way, the electron blocking effect of the first protective layer 2031 can be achieved > the electron blocking effect of the second protective layer 2032 > the electron blocking effect of the third protective layer 2033, which is beneficial to enhancing the electron blocking effect at the red sub-pixel.

[0175] The protective layer 203 formed by method seven is not only located between the quantum dot light-emitting layer 102 and the electron transport layer 104, but also located inside the electron transport layer 104. The protective layer 203 is in chemical contact with the electron transport layer 104 and can be connected to the end of the first ligand.

[0176] Method 8

[0177] In method eight, the treatment of the quantum dot light-emitting layer can adopt any one of the above methods one, two, three, and four, and the method for forming the protective layer 303 and the electron transport layer 104 is different from method one. In method eight, the electron transport material ZnO is first wrapped with a surfactant, and then the electron transport material ZnO wrapped with the surfactant is deposited on the side of the quantum dot light-emitting layer 102 away from the first electrode 101 to form the electron transport layer 104, wherein the surfactant acts as a protective layer 303. In this case, the surfactant can wrap the ZnO nanoparticles between the electron transport layer 104 and the quantum dot light-emitting layer 102, or it can wrap the ZnO nanoparticles from all sides of the electron transport layer 104. Alternatively, a surfactant layer can be first formed on the side of the quantum dot light-emitting layer 102 away from the first electrode 101, the surfactant layer acts as a protective layer 303, and then the electron transport layer 104 is formed on the side of the protective layer 303 away from the first electrode 101. In this case, the surfactant can wrap the electron transport layer 104 between the electron transport layer 104 and the quantum dot light-emitting layer 102, or it can wrap the electron transport layer 104 from all sides. The surfactant can form a vesicle-like structure to wrap the ZnO in the electron transport layer 104. While protecting the ZnO from the influence of the organic acid groups, it can also increase the distance between the ZnO particles, reduce electron injection, and reduce conductivity, which is beneficial to charge balance.

[0178] In some embodiments, the chemical formula of the surfactant can be represented by A + B - , where A + represents cations, B - represents an anion. For example, B - Can be selected from halogen ions, hydroxide ions, PF6 -、BF4 - Any of A + The chemical formula can be expressed as C n H 2n+1 N(C m H 2m+1 )3 or C n H 2n+1 N(C m H 2m+1 )2(C m H 2m+1 )2NC n H 2n+1 , where n is any positive integer between 8 and 20, and m is any positive number between 0 and 4. n H 2n+1 N(C m H 2m+1 ) 3 can be a cation of a quaternary ammonium salt or a cation of a quaternary ammonium base, which contains one nitrogen atom and is a single-center ion; C n H 2n+1 N(C m H 2m+1 )2(C m H 2m+1 )2NC n H 2n+1 It can be a quaternary ammonium salt or quaternary ammonium base cation, which contains two nitrogen atoms and is a double-center ion. Surfactant molecules are quaternary ammonium salts or quaternary ammonium base molecules containing non-polar long chain ends.

[0179] For other technical effects of the method for preparing the light-emitting device, reference can be made to the technical effects of the light-emitting device described in the previous embodiment, and for the sake of brevity, they will not be described again here.

[0180] It will be understood that although the terms first, second, third, etc. may be used to describe various elements, components, areas, layers and / or parts in this article, these elements, components, areas, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer or part from another element, component, area, layer or part. Therefore, the first element, component, area, layer or part discussed above can be referred to as the second element, component, area, layer or part without departing from the teachings of the present disclosure.

[0181] Spatially relative terms such as "row," "column," "under," "above," "left," "right," and the like may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures for ease of description. It will be understood that these spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figure is flipped, the element described as "under other elements or features" will be oriented as "above other elements or features." Thus, the exemplary term "under" can encompass both orientations of above and below. The device can be oriented otherwise (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein are interpreted accordingly. In addition, it will also be understood that when a layer is referred to as "between two layers," it can be the only layer between the two layers, or one or more intermediate layers may also be present.

[0182] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "one", "an" and "the" are intended to also include the plural forms, unless the context clearly indicates otherwise. It will be further understood that the terms "include" and / or "comprise" when used in this specification specify the presence of the features, wholes, steps, operations, elements and / or parts, but do not exclude the presence of one or more other features, wholes, steps, operations, elements, parts and / or their groups or add one or more other features, wholes, steps, operations, elements, parts and / or their groups. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In the description of this specification, the description of the reference terms "one embodiment", "another embodiment" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily need to be directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. Furthermore, those skilled in the art may combine different embodiments or examples and features of different embodiments or examples described in this specification without mutual contradiction.

[0183] It will be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “adjacent to” another element or layer, it can be directly on, directly connected to, directly coupled to, or directly adjacent to another element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” “directly coupled to,” or “directly adjacent to” another element or layer, no intervening elements or layers are present. However, in no case should “on” or “directly on” be interpreted as requiring that one layer completely cover the underlying layer.

[0184] Embodiments of the present disclosure are described herein with reference to schematic illustrations (and intermediate structures) of idealized embodiments of the present disclosure. Because of this, variations in the illustrated shapes, for example as a result of manufacturing techniques and / or tolerances, should be expected. Therefore, embodiments of the present disclosure should not be interpreted as being limited to the specific shapes of the regions illustrated herein, but should include shape deviations, for example, due to manufacturing. Therefore, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shape of the regions of the device and are not intended to limit the scope of the present disclosure.

[0185] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant art and / or the context of this specification, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0186] As will be appreciated by those skilled in the art, although the various steps of the method of the present disclosure are described in a particular order in the accompanying drawings, this does not require or imply that the steps must be performed in that particular order unless the context clearly indicates otherwise. Additionally or alternatively, multiple steps may be combined into a single step and / or a single step may be broken down into multiple steps and performed. In addition, other method steps may be inserted between steps. An inserted step may represent an improvement to a method such as that described herein, or may be unrelated to the method. In addition, a given step may not be fully completed before the next step begins.

[0187] “At least one of A, B, and C” has the same meaning as “at least one of A, B, or C,” and both include the following combinations of A, B, and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B, and C.

[0188] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0189] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0190] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A light-emitting device, comprising: a first electrode; quantum dot light-emitting layer; an electron transport layer, located on a side of the quantum dot light-emitting layer away from the first electrode; as well as a protective layer, located on a side of the quantum dot light-emitting layer away from the first electrode, The quantum dot light-emitting layer includes organic acid groups, and the protective layer blocks the organic acid groups from contacting the electron transport layer.

2. The light emitting device according to claim 1, wherein The protective layer is at least located between the quantum dot light-emitting layer and the electron transport layer.

3. The light emitting device according to claim 2, wherein The protective layer is also located in the electron transport layer. The light emitting device according to claim 3 , wherein: The protective layer is located on a side of the electron transport layer close to the quantum dot light-emitting layer, and the protective layer is in contact with the quantum dot light-emitting layer. The light emitting device according to claim 2 , wherein: The protective layer comprises an anti-contact layer or a salt layer. The light emitting device according to claim 5 , wherein: The salt layer includes a carboxylate layer or a quaternary ammonium salt layer.

7. The light emitting device according to claim 6, wherein The salt layer also includes unreacted base. The light emitting device according to claim 5 , wherein: The material of the anti-contact layer includes any one of a hydrophobic material, a silane coupling agent, and an epoxy resin.

9. The light emitting device according to any one of claims 5 to 7, wherein: The salt layer is in physical contact with the electron transport layer.

10. The light emitting device according to any one of claims 5 to 7, wherein: The salt layer is connected to the electron transport layer through a chemical bond. The light emitting device according to claim 10 , wherein: The electron transport layer includes a ZnO body and a first coordination group coordinated on the ZnO body, and the salt layer is connected to at least some of the first coordination groups through the chemical bond.

12. The light emitting device according to claim 11, wherein The electron transport layer includes a first surface close to the quantum dot light-emitting layer and a second surface away from the quantum dot light-emitting layer. The salt layer is connected to the first coordination group at the first surface through the chemical bond. The second surface includes a first ligand coordinated on the ZnO body, and the first ligand includes a basic group.

13. The light emitting device according to claim 12, wherein: The chemical formula of the first ligand is Wherein, the group R represents an alkyl chain, and the group X is selected from any one of the following:

14. The light emitting device according to claim 1 or 2, wherein: The protective layer includes a surfactant, and the surfactant wraps the electron transport layer.

15. The light emitting device according to claim 1 or 2, wherein: The electron transport layer includes zinc oxide nanoparticles, and the protective layer includes a surfactant, which wraps the zinc oxide nanoparticles.

16. The light emitting device according to claim 14 or 15, wherein: The chemical formula of the surfactant is A + B - , where A + represents cations, B - represents anions, Among them, B - Selected from halogen ions, hydroxide ions, PF6 - 、BF4 - any of; and Among them, A + The chemical formula is C n H 2n+1 N(C m H 2m+1 )3 or C n H 2n+1 N(C m H 2m+1 )2(C m H 2m+1 )2NC n H 2n+1 , n is any positive integer between 8 and 20, and m is any positive number between 0 and 4.

17. The light emitting device according to any one of claims 1 to 16, wherein: The quantum dot light-emitting layer includes a plurality of quantum dots, at least some of the plurality of quantum dots include a quantum dot body and a second ligand coordinated on the quantum dot body, and at least some of the second ligands are the organic acid groups.

18. The light emitting device according to claim 17, wherein The general chemical formula of the organic acid group is C n H 2n-1 COOH or C6H5-C n H 2n -COOH, n is a positive integer greater than or equal to 1.

19. The light emitting device according to any one of claims 1 to 18, further comprising: a hole injection layer, located between the first electrode and the quantum dot light-emitting layer; A hole transport layer, located between the hole injection layer and the quantum dot light-emitting layer; as well as The second electrode is located on a side of the electron transport layer away from the first electrode.

20. The light emitting device according to any one of claims 1 to 16, wherein: The quantum dot light-emitting layer includes a plurality of quantum dots, at least some of the plurality of quantum dots include a quantum dot body and a plurality of second ligands coordinated on the quantum dot body, a portion of the second ligands in the plurality of second ligands are the organic acid groups, the quantum dot light-emitting layer includes a red quantum dot light-emitting layer configured to emit red light, a green quantum dot light-emitting layer configured to emit green light, and a blue quantum dot light-emitting layer configured to emit blue light, the red quantum dot light-emitting layer, the green quantum dot light-emitting layer, and the blue quantum dot light-emitting layer are separated from each other, and The molar ratio of the organic acid groups in the red quantum dot light-emitting layer to the multiple second ligands in the red quantum dot light-emitting layer is smaller than the molar ratio of the organic acid groups in the green quantum dot light-emitting layer to the multiple second ligands in the green quantum dot light-emitting layer, and the molar ratio of the organic acid groups in the green quantum dot light-emitting layer to the multiple second ligands in the green quantum dot light-emitting layer is smaller than the molar ratio of the organic acid groups in the blue quantum dot light-emitting layer to the multiple second ligands in the blue quantum dot light-emitting layer.

21. The light emitting device according to claim 20, wherein The molar ratio of the organic acid group in the red quantum dot light-emitting layer to the plurality of second ligands in the red quantum dot light-emitting layer is 0.1% to 10%, The organic acid groups in the green quantum dot light-emitting layer and the green quantum dot light-emitting layer The molar ratio of the plurality of second ligands is 0.1% to 20%, The molar ratio of the organic acid groups in the blue quantum dot light-emitting layer to the plurality of second ligands in the blue quantum dot light-emitting layer is 0.1% to 60%.

22. The light emitting device according to claim 20 or 21, wherein: The protective layer is located between the quantum dot light-emitting layer and the electron transport layer, and the protective layer includes a first protective layer, a second protective layer, and a third protective layer. The orthographic projection of the first protective layer on the first electrode at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode, the orthographic projection of the second protective layer on the first electrode at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode, and the orthographic projection of the third protective layer on the first electrode at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode. The thickness of the first protective layer is greater than the thickness of the second protective layer, and the thickness of the second protective layer is greater than the thickness of the third protective layer.

23. The light emitting device according to claim 20 or 21, wherein: The electron transport layer includes a hydrophobic material or an alkaline material, and the electron transport layer includes a first electron transport layer, a second electron transport layer, and a third electron transport layer. The orthographic projection of the first electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode, the orthographic projection of the second electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode, and the orthographic projection of the third electron transport layer on the first electrode at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode. The content of the hydrophobic material or alkaline material in the first electron transport layer is greater than the content of the hydrophobic material or alkaline material in the second electron transport layer, and the content of the hydrophobic material or alkaline material in the second electron transport layer is greater than the content of the hydrophobic material or alkaline material in the third electron transport layer.

24. The light emitting device according to claim 23, wherein The protective layer includes a salt layer, and the protective layer includes a first protective layer, a second protective layer, and a third protective layer. The orthographic projection of the first protective layer on the first electrode at least partially overlaps with the orthographic projection of the red quantum dot light-emitting layer on the first electrode, the orthographic projection of the second protective layer on the first electrode at least partially overlaps with the orthographic projection of the green quantum dot light-emitting layer on the first electrode, and the orthographic projection of the third protective layer on the first electrode at least partially overlaps with the orthographic projection of the blue quantum dot light-emitting layer on the first electrode. The amount of salt substance in the first protective layer is greater than the amount of salt substance in the second protective layer, and the amount of salt substance in the second protective layer is greater than the amount of salt substance in the third protective layer.

25. A display device comprising a plurality of light-emitting devices according to any one of claims 1 to 24.

26. A method for preparing a light-emitting device, comprising: providing a first electrode; treating the intermediate layer or the quantum dot solution with an organic acid to form a quantum dot light-emitting layer including organic acid groups; forming an electron transport layer on a side of the quantum dot light-emitting layer away from the first electrode; as well as A protective layer is formed on a side of the quantum dot light-emitting layer away from the first electrode, and the protective layer blocks the organic acid group from contacting the electron transport layer.

27. The method according to claim 26, wherein A protective layer is formed on a side of the quantum dot light-emitting layer away from the first electrode, comprising: The surface of the quantum dot light-emitting layer is treated with saturated steam containing an alkaline material, so that the alkaline material and the excess organic acid groups on the surface of the quantum dot light-emitting layer undergo an acid-base neutralization reaction to form a salt layer.

28. The method according to claim 26, wherein A protective layer is formed on a side of the quantum dot light-emitting layer away from the first electrode, comprising: providing an anti-contact layer on a side of the quantum dot light-emitting layer away from the first electrode, wherein the material of the anti-contact layer comprises any one of a hydrophobic material, a silane coupling agent, and an epoxy resin; or A basic layer is provided on a side of the quantum dot light-emitting layer away from the first electrode, and the basic layer undergoes an acid-base neutralization reaction with excess organic acid groups on the surface of the quantum dot light-emitting layer to form a salt layer.

29. The method according to claim 26, wherein Forming an electron transport layer on a side of the quantum dot light-emitting layer away from the first electrode and forming a protective layer on a side of the quantum dot light-emitting layer away from the first electrode, comprising: Alkaline material is doped into the electron transport material to form a mixed material, and the mixed material is deposited on the side of the quantum dot light emitting layer away from the first electrode to form the electron transport layer, and the alkaline material in the mixed material is in contact with the surface of the quantum dot light emitting layer. The excess organic acid groups on the surface undergo acid-base neutralization reaction to form a salt layer; or An electron transport material having a first ligand including a basic group is deposited on a side of the quantum dot light-emitting layer away from the first electrode to form the electron transport layer, and the basic groups on the first ligand undergo an acid-base neutralization reaction with excess organic acid groups on the surface of the quantum dot light-emitting layer to form a salt layer.

30. The method according to claim 29, wherein The electron transport layer includes a first electron transport layer, a second electron transport layer, and a third electron transport layer; the quantum dot light-emitting layer includes a red quantum dot light-emitting layer, a green quantum dot light-emitting layer, and a blue quantum dot light-emitting layer; an orthographic projection of the first electron transport layer on the first electrode at least partially overlaps with an orthographic projection of the red quantum dot light-emitting layer on the first electrode; an orthographic projection of the second electron transport layer on the first electrode at least partially overlaps with an orthographic projection of the green quantum dot light-emitting layer on the first electrode; and an orthographic projection of the third electron transport layer on the first electrode at least partially overlaps with an orthographic projection of the blue quantum dot light-emitting layer on the first electrode. The method comprises doping an alkaline material into an electron transport material to form a mixed material, and depositing the mixed material on a side of the quantum dot light-emitting layer away from the first electrode to form the electron transport layer, comprising: The alkaline material and the electron transport material are doped in a first molar ratio, a second molar ratio, and a third molar ratio, respectively, to form a first mixed material, a second mixed material, and a third mixed material. The first mixed material, the second mixed material, and the third mixed material are deposited on the side of the quantum dot light-emitting layer away from the first electrode to form the first electron transport layer, the second electron transport layer, and the third electron transport layer, wherein the first molar ratio is greater than the second molar ratio, and the second molar ratio is greater than the third molar ratio.

31. The method of claim 26, wherein: Forming an electron transport layer on a side of the quantum dot light-emitting layer away from the first electrode and forming a protective layer on a side of the quantum dot light-emitting layer away from the first electrode, comprising: Wrapping an electron transport material with a surfactant, and depositing the electron transport material wrapped with the surfactant on a side of the quantum dot light-emitting layer away from the first electrode to form the electron transport layer; or forming a surfactant on a side of the quantum dot light-emitting layer away from the first electrode, and forming the electron transport layer on a side of the surfactant away from the first electrode; Wherein, the protective layer includes the surfactant.

32. The light emitting device according to any one of claims 26 to 31, wherein: Treating the interlayer or quantum dot solution with an organic acid includes: forming the intermediate layer on the first electrode, the intermediate layer including quantum dots, and treating the intermediate layer with saturated steam including the organic acid to form the quantum dot light-emitting layer on the first electrode; or forming the intermediate layer on the first electrode, the intermediate layer comprising quantum dots, applying an organic acid solution to a side of the intermediate layer away from the first electrode so that the intermediate layer is soaked in the organic acid solution, and removing the organic acid solution to form the quantum dot light-emitting layer on the first electrode; or preparing the quantum dot solution, wherein the quantum dots include a quantum dot body and a second ligand coordinated to the quantum dot body, replacing at least some of the plurality of second ligands with the organic acid group by ligand exchange to form a treated quantum dot solution, and depositing the treated quantum dot solution on the first electrode to form the quantum dot light-emitting layer; or The organic acid is mixed with the quantum dot solution, and the mixed solution is deposited on the first electrode to form the quantum dot light-emitting layer.

Images