Quantum dot material, quantum dot ink, quantum dot device and preparation method therefor

Abstract

A quantum dot material, a quantum dot ink, a quantum dot device and a preparation method therefor. The quantum dot material comprises a quantum dot bulk and an initial ligand coordinated to the surface of the quantum dot bulk, wherein the initial ligand accounts for 7-11% of the quantum dot material.

Description

A quantum dot material, quantum dot ink, quantum dot device, and its fabrication method Technical Field

[0001] This disclosure relates to the field of display technology, and in particular to a quantum dot material, a quantum dot ink, a quantum dot device, and a method for preparing the same. Background Technology

[0002] Quantum dots (QDs), also known as nanocrystals, are nanoparticles composed of group II-VI or III-V elements. The particle size of quantum dots typically ranges from 1 to 20 nm. Due to the quantum confinement of electrons and holes, the continuous band structure becomes a discrete energy level structure, allowing them to emit fluorescence when stimulated. With the advancement of quantum dot fabrication technology, the stability and luminous efficiency of quantum dots are continuously improving, and their application prospects in the display field are becoming increasingly promising.

[0003] Quantum dot light-emitting diodes (QLEDs) have shown great promise in the display and lighting fields due to their unique characteristics such as narrow emission peaks, high color purity, strong fluorescence lifetime, high fluorescence quantum yield, and continuously tunable fluorescence spectrum.

[0004] Commonly used techniques for preparing quantum dot light-emitting layers include inkjet printing, transfer printing, and photolithography. Photolithography is the most promising method for preparing high-resolution QLEDs. Summary of the Invention

[0005] This disclosure provides a quantum dot material, a quantum dot ink, a quantum dot device, and a method for preparing the same, as detailed below:

[0006] This disclosure provides a quantum dot material, including a quantum dot body and an initial ligand that coordinates with the surface of the quantum dot body, wherein the initial ligand accounts for 7%-11% of the quantum dot material.

[0007] In one possible implementation, in the quantum dot material provided in the embodiments of this disclosure, the proportion of gravity lost by the quantum dot material in the range of 500 to 600°C is 7%-11% in the thermogravimetric analysis curve.

[0008] In one possible implementation, in the quantum dot material provided in the embodiments of this disclosure, the carbon chain length of the initial ligand is greater than or equal to 10, and the initial ligand accounts for 7%-10% of the quantum dot material.

[0009] In one possible implementation, in the quantum dot material provided in the embodiments of this disclosure, the quantum dot material emits red light, and the initial ligand accounts for 8.5%-9.5% of the quantum dot material.

[0010] The quantum dot material emits green light, and the initial ligand accounts for 8%-9% of the quantum dot material.

[0011] The quantum dot material emits blue light, and the initial ligand accounts for 7.5%-8.5% of the quantum dot material.

[0012] In one possible implementation, in the quantum dot material provided in the embodiments of this disclosure, the initial ligand includes at least one of oleic acid and oleylamine.

[0013] In one possible implementation, in the quantum dot material provided in the embodiments of this disclosure, the carbon chain length of the initial ligand is less than 10, and the initial ligand accounts for 8%-11% of the quantum dot material.

[0014] In one possible implementation, in the quantum dot material provided in the embodiments of this disclosure, the quantum dot material emits red light, and the initial ligand accounts for 9.5%-10.5% of the quantum dot material.

[0015] The quantum dot material emits green light, and the initial ligand accounts for 9%-10% of the quantum dot material.

[0016] The quantum dot material emits blue light, and the initial ligand accounts for 8.5%-9.5% of the quantum dot material.

[0017] In one possible implementation, the initial ligand in the quantum dot material provided in the embodiments of this disclosure includes octanoic acid.

[0018] In one possible implementation, the quantum dot material provided in the embodiments of this disclosure includes CdS, CdSe, InP, ZnSe, PbS, CsPbCl3, CsPbBr3, CsPhI3, CdS / ZnS, CdSe / ZnS, PbS / ZnS, InP / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, or CsPhI3 / ZnS.

[0019] Accordingly, this disclosure also provides a quantum dot ink, comprising a solvent and the quantum dot material described in any of the above embodiments of this disclosure.

[0020] Accordingly, this disclosure also provides a quantum dot device, including a quantum dot layer, wherein the material of the quantum dot layer is any of the quantum dot materials described in the above-mentioned embodiments of this disclosure.

[0021] In one possible implementation, in the quantum dot device provided in the embodiments of this disclosure, the quantum dot layer includes red quantum dot units, green quantum dot units, and blue quantum dot units, wherein the red quantum dot units, the green quantum dot units, and the blue quantum dot units do not overlap with each other, and the proportion of the initial ligand in the quantum dot material of the red quantum dot units, the green quantum dot units, and the blue quantum dot units decreases sequentially.

[0022] In one possible implementation, in the quantum dot device provided in the embodiments of this disclosure, the surfaces of the quantum dot bodies in the red quantum dot unit, the green quantum dot unit, and the blue quantum dot unit are further coordinated with inorganic ions.

[0023] In one possible implementation, in the quantum dot device provided in the embodiments of this disclosure, the inorganic ions include Cl. - ,Br - I - At least one of them.

[0024] In one possible implementation, the quantum dot device provided in the embodiments of this disclosure further includes a carrier transport layer located on one side of the quantum dot layer, the carrier transport layer having a cross-linked network structure.

[0025] In one possible implementation, in the quantum dot device provided in the embodiments of this disclosure, the carrier transport layer is a hole transport layer or an electron transport layer.

[0026] In one possible implementation, in the quantum dot device provided in the embodiments of this disclosure, the thickness of the quantum dot layer is 15nm-30nm.

[0027] Accordingly, this disclosure also provides a method for fabricating a quantum dot device, comprising:

[0028] A carrier transport thin film is formed on one side of a substrate; the material of the carrier transport thin film includes a carrier transport material and a crosslinking agent;

[0029] The carrier transport film is exposed;

[0030] A quantum dot film is formed on the side of the exposed carrier transport film away from the substrate; the material of the quantum dot film is any of the quantum dot materials described in the embodiments of this disclosure.

[0031] The exposed carrier transport film is developed to remove the unexposed areas of the carrier transport film and the quantum dot film, so as to form a patterned carrier transport layer and quantum dot layer in the exposed area.

[0032] In one possible implementation, the fabrication method provided in the embodiments of this disclosure, after forming the patterned carrier transport layer and quantum dot layer in the exposure region, further includes:

[0033] An ethanol solution of ZnX2 was drop-coated onto the side of the quantum dot layer away from the substrate. After soaking for a predetermined time, the quantum dot layer was washed with ethanol to remove X2. - Coordinated on the quantum dot bulk surface of the quantum dot material; wherein, X - For Cl - ,Br - or I - . Attached Figure Description

[0034] Figure 1 is a schematic diagram of the structure of a quantum dot material provided in an embodiment of this disclosure;

[0035] Figure 2 is a schematic diagram of the quantum dot material of this disclosure obtained after conventionally synthesized quantum dot material is washed with solvent;

[0036] Figure 3 is a schematic diagram of the structure of a quantum dot device provided in an embodiment of this disclosure;

[0037] Figure 4 is a schematic diagram of the structure of another quantum dot device provided in an embodiment of this disclosure;

[0038] Figure 5 is a schematic flowchart of a quantum dot device fabrication method provided in an embodiment of this disclosure;

[0039] Figure 6 is a schematic flowchart of another method for fabricating a quantum dot device according to an embodiment of this disclosure;

[0040] Figure 7 shows the thermogravimetric curves of the conventional and the green quantum dot materials synthesized in this disclosure;

[0041] Figure 8 is a fluorescence photograph of the green quantum dot layer prepared in this disclosure;

[0042] Figure 9 shows the SEM images of the exposed and unexposed areas after development.

[0043] Figure 10 is a schematic diagram of the thickness data obtained by a step tester for the hole transport layer and quantum dot layer formed in this disclosure.

[0044] Figure 11 shows a fluorescence photograph of the green quantum dot layer prepared in Comparative Example 1;

[0045] Figure 12 is a SEM image of the exposed area of ​​Comparative Example 1 after development;

[0046] Figures 13A-13K are schematic diagrams of the structure of the quantum dot device provided in the embodiments of this disclosure during each step of the fabrication process.

[0047] Figures 14A and 14B are schematic diagrams of the structure corresponding to each step in the fabrication of the quantum dot device shown in Figure 3.

[0048] Figures 15A-15L are schematic diagrams of the structure corresponding to each step in the fabrication of the quantum dot device shown in Figure 4.

[0049] Figure 16 is a schematic diagram of the structure of a display device provided in an embodiment of this disclosure. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Furthermore, the embodiments and features in the embodiments of this disclosure can be combined with each other without conflict. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0051] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "comprising" or "including," and similar terms as used in this disclosure, mean that an element or object preceding the term encompasses the elements or objects listed following the term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "inner," "outer," "upper," and "lower" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0052] It should be noted that the dimensions and shapes of the figures in the accompanying drawings do not reflect actual proportions and are intended only to illustrate the content of this disclosure. Furthermore, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0053] Patterning high-resolution QLED products requires photolithography. Direct photolithography involves ligand exchange of quantum dots (QDs) to obtain photosensitive QDs, and the addition of photosensitive crosslinking agents to the QD solution. However, the addition of photosensitive crosslinking agents and exposure processes negatively impact the final device efficiency. Therefore, reducing the processing of QD materials can lead to higher-performance QLED devices.

[0054] This disclosure provides a quantum dot material, as shown in Figure 1, comprising a quantum dot body QD and an initial ligand A coordinated with the surface of the quantum dot body QD. The initial ligand A accounts for 7%-11% of the quantum dot material (QD+A). During the photolithographic patterning development process, more ligands make the quantum dots easier to develop cleanly (experiments have confirmed that adding ligands can result in cleaner development); conversely...

[0055] The quantum dot materials provided in this disclosure have an initial ligand content of 7%-11%, compared to approximately 13% for conventionally synthesized quantum dot materials. This lower initial ligand content does not affect the luminescence properties of the quantum dot materials. Furthermore, the lower initial ligand content results in relatively poor colloidal stability and reduced solubility, making it less susceptible to dissolution and rinsing by the developer during photolithography. This allows for better adhesion to the substrate side, transforming the less easily dissolved quantum dot material into patterned quantum dots. Thus, the quantum dot materials of this disclosure do not require ligand exchange; they can be directly synthesized with initial ligands for photolithographic patterning, reducing potential efficiency degradation during ligand exchange. Moreover, during photolithographic patterning, this disclosure eliminates the need for photosensitive crosslinking agents and exposure treatment, maximizing the preservation of the intrinsic efficiency of the quantum dot materials and thereby improving the efficiency of quantum dot devices.

[0056] It should be noted that the proportion of initial ligands in quantum dot materials refers to the ratio of the mass of all initial ligands to the total mass of the quantum dot material (the quantum dot bulk plus the initial ligands on its surface) to the total mass of the quantum dot material, with the total mass of the quantum dot material (the quantum dot bulk plus the initial ligands on its surface) being 1.

[0057] In some embodiments, as shown in FIG7, in the quantum dot materials provided in the present disclosure, the proportion of quantum dot material lost in the thermogravimetric analysis (TGA) range of 50–600 °C is 7%–11%. Specifically, the TGA analysis curve is obtained by measuring the proportion of organic ligands lost (volatile) in the quantum dot material in the high-temperature range using differential scanning calorimetry, which proves that the initial ligand A of the present disclosure accounts for 7%–11% of the quantum dot material (QD+A), and the content of the initial ligand of the present disclosure is relatively low compared with conventionally synthesized quantum dot materials.

[0058] In some embodiments, in order to obtain quantum dot materials with an initial ligand content of 7%-11% in the quantum dot material, a certain amount of the initial ligand can be washed away multiple times with a solvent on the basis of conventionally synthesized quantum dot materials with an initial ligand content of approximately 13%, as shown in Figure 2. This will reduce the dissolving and developing ability of the developing solution during the photolithography process and increase the thickness of the patterned quantum dot layer.

[0059] In some embodiments, in the quantum dot materials provided in this disclosure, as shown in FIG1, when the carbon chain length (i.e., the number of carbon atoms on the main chain) of the initial ligand A is greater than or equal to 10, this disclosure refers to the initial ligand A with a carbon chain length greater than or equal to 10 as a long-chain ligand. For example, the initial ligand A includes, but is not limited to, at least one of oleic acid and oleylamine. In this case, the proportion of the initial ligand A in the quantum dot material (QD+A) can be 7%-10%. Specifically, the content of the initial ligand (e.g., oleylamine) after the synthesis of conventional quantum dot materials is approximately 13%. This disclosure can use antisolvents such as methanol and ethanol to wash the conventionally synthesized quantum dot materials 3-6 times to reduce the original content of the initial ligand from 13% to 7%-10%, thereby obtaining a quantum dot material that can reduce the solubility and rinsing effect of the developer in the photolithography process and improve the film retention rate.

[0060] In some embodiments, during the development process, red quantum dot materials are more likely to remain, while blue quantum dot materials are least likely to remain. Therefore, for the easily retained red quantum dot materials, the initial ligand content can be relatively higher to improve luminescence efficiency, while for the least retained blue quantum dot materials, the initial ligand content can be lower. Since fewer ligands result in lower solubility in the developing solution and easier retention, the film retention rate of blue quantum dot materials is improved. Therefore, in the quantum dot materials provided in the embodiments of this disclosure, for the quantum dot materials with long-chain ligands, when the luminescence color of the quantum dot material is red, the initial ligand content can be 8.5%-9.5%; when the luminescence color of the quantum dot material is green, the initial ligand content can be 8%-9%; and when the luminescence color of the quantum dot material is blue, the initial ligand content can be 7.5%-8.5%.

[0061] In some embodiments, in the quantum dot materials provided in this disclosure, as shown in FIG1, when the carbon chain length of the initial ligand A is less than 10, this disclosure refers to the initial ligand A with a carbon chain length less than 10 as a short-chain ligand. For example, the initial ligand A includes, but is not limited to, octanoic acid. In this case, the proportion of the initial ligand A in the quantum dot material (QD+A) can be 8%-11%. This is because the solubility of short-chain ligands is relatively poor compared to that of long-chain ligands, and they are easier to retain during development. Therefore, the content range of short-chain ligands can be slightly higher to improve luminescence efficiency.

[0062] In some embodiments, for the quantum dot materials provided in this disclosure, when the quantum dot material emits red light, the initial ligand accounts for 9.5%-10.5% of the quantum dot material; when the quantum dot material emits green light, the initial ligand accounts for 9%-10% of the quantum dot material; and when the quantum dot material emits blue light, the initial ligand accounts for 8.5%-9.5% of the quantum dot material.

[0063] In some embodiments, as shown in FIG1, the quantum dot body (QD) in the quantum dot materials provided in the embodiments of this disclosure may include, but is not limited to, CdS, CdSe, InP, ZnSe, PbS, CsPbCl3, CsPbBr3, CsPhI3, CdS / ZnS, CdSe / ZnS, PbS / ZnS, InP / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, or CsPhI3 / ZnS.

[0064] Based on the same inventive concept, this disclosure also provides a quantum dot ink, including a solvent and the quantum dot material described above. Since the principle by which this quantum dot ink solves the problem is similar to that of the quantum dot material described above, the implementation of the quantum dot ink provided in this disclosure can refer to the implementation of the quantum dot material described above, and repeated details will not be elaborated further.

[0065] Based on the same inventive concept, this disclosure also provides a quantum dot device, as shown in Figures 3 and 4, including a quantum dot layer 10. The material of the quantum dot layer 10 is the quantum dot material provided in this disclosure. When the quantum dot layer 10 is fabricated using photolithography, this quantum dot device does not require ligand exchange of the quantum dot material, does not require the addition of a photosensitive crosslinking agent to the quantum dot material, and does not require exposure treatment of the quantum dot material. This maximizes the preservation of the intrinsic efficiency of the quantum dot material, thereby improving the luminous efficiency of the quantum dot device.

[0066] In some embodiments, in the quantum dot devices provided in this disclosure, as shown in Figures 3 and 4, to achieve full-color display, the quantum dot layer 10 generally includes, but is not limited to, red quantum dot units (RQD), green quantum dot units (GQD), and blue quantum dot units (BQD). The red quantum dot units (RQD), green quantum dot units (GQD), and blue quantum dot units (BQD) do not overlap. The proportion of initial ligand A in the quantum dot material (QD+A) decreases sequentially among the red quantum dot units (RQD), green quantum dot units (GQD), and blue quantum dot units (BQD). This embodiment can be referred to the aforementioned description of the specific content of initial ligand A for quantum dot materials of different emission colors, which will not be repeated here.

[0067] In some embodiments, because the initial ligand content of the quantum dot material provided in this disclosure is lower than that of conventional quantum dot materials, some defects are generated on the surface of the quantum dot body, reducing the luminescence efficiency. Therefore, in the quantum dot devices provided in the embodiments of this disclosure, as shown in Figures 3 and 4, the surface of the quantum dot body QD in the red quantum dot unit RQD, green quantum dot unit GQD, and blue quantum dot unit BQD is also coordinated with inorganic ions B. This allows for the application of an ethanol solution of ZnX2 to one side of the quantum dot layer 10 after development during the photolithography process to prepare the quantum dot layer 10. - The quantum dot layer 10 is passivated with inorganic ions B. After a certain period of time, the quantum dot layer 10 is cleaned with ethanol, thereby passivating the defects on the surface of the quantum dot body QD caused by the initial ligand detachment and improving the luminescence efficiency.

[0068] In some embodiments, in the quantum dot devices provided in the present disclosure, as shown in Figures 3 and 4, the inorganic ion B may include, but is not limited to, Cl. - ,Br - I - At least one of them.

[0069] In some embodiments, as shown in Figures 3 and 4, in the quantum dot devices provided in the present disclosure, the surface of the quantum dot body QD in the red quantum dot unit RQD, the green quantum dot unit GQD, and the blue quantum dot unit BQD may still have a small amount of ZnX2 that has not been cleaned off, which does not affect the luminescence of the quantum dot layer.

[0070] In some embodiments, as shown in Figures 3 and 4, the quantum dot device provided in this disclosure further includes a carrier transport layer 20 located on one side of the quantum dot layer 10, the carrier transport layer 20 having a cross-linked network structure. Thus, when fabricating the quantum dot layer 10 using photolithography, the carrier transport layer 20 can be used as a sacrificial layer, i.e., a carrier transport film is formed using a carrier transport material containing a photosensitive cross-linking agent, and then exposed. A stable cross-linked network structure is formed within the exposed area of ​​the carrier transport film. Subsequently, a quantum dot film is formed on the carrier transport film using the quantum dot material provided in this disclosure. Finally, development is performed to remove the unexposed areas of the carrier transport film and the quantum dot film, thereby forming a patterned carrier transport layer 20 and quantum dot layer 10 in the exposed area. That is, the quantum dot material of this disclosure does not require ligand exchange to form photosensitive ligands and does not require the addition of a photosensitive cross-linking agent, which can greatly improve the luminescence efficiency of the quantum dot layer 10.

[0071] In some embodiments, in the quantum dot devices provided in this disclosure, as shown in Figures 3 and 4, the thickness of the quantum dot layer 10 ranges from 15 nm to 30 nm, preferably around 15 nm thick, i.e., a single-layer quantum dot layer 10. This is because if the quantum dot layer 10 is too thick, the developing solution will not easily penetrate the quantum dot layer 10 to wash away the next layer of charge carrier transport layer 20, resulting in quantum dot residue; and if the quantum dot layer 10 is too thin, a continuous quantum dot film cannot be formed, causing leakage.

[0072] Currently, electroluminescent devices can be divided into upright structures and inverted structures. The difference between the upright and inverted structures lies in the order in which the film layers are fabricated. Specifically, in an upright structure, the anode, hole injection layer, hole transport layer, quantum dot layer, electron transport layer, and cathode are formed sequentially on the substrate. In an inverted structure, the cathode, electron transport layer, quantum dot layer, hole transport layer, hole injection layer, and anode are formed sequentially on the substrate.

[0073] In some embodiments, as shown in FIG3, the quantum dot device provided in the present disclosure is an upright structure, the carrier transport layer 20 is a hole transport layer, and the quantum dot device further includes: a substrate 30 located on the side of the carrier transport layer 20 away from the quantum dot layer 10, an anode 40 located between the substrate 30 and the carrier transport layer 20, a hole injection layer 50 located between the anode 40 and the carrier transport layer 20, an electron transport layer 60 located on the side of the quantum dot layer 10 away from the substrate 30, and a cathode 70 located on the side of the electron transport layer 60 away from the substrate 30. In this embodiment, the hole transport layer is used as a sacrificial layer when fabricating the quantum dot layer 10.

[0074] In some embodiments, as shown in FIG4, the quantum dot device provided in this disclosure has an inverted structure, with the carrier transport layer 20 serving as an electron transport layer. The quantum dot device further includes: a substrate 30 located on the side of the carrier transport layer 20 away from the quantum dot layer 10; a cathode 70 located between the substrate 30 and the carrier transport layer 20; a hole transport layer 80 located on the side of the quantum dot layer 10 away from the substrate 30; a hole injection layer 50 located on the side of the hole transport layer 80 away from the substrate 30; and an anode 40 located on the side of the hole injection layer 50 away from the substrate 30. In this embodiment, the electron transport layer is used as a sacrificial layer when fabricating the quantum dot layer 10.

[0075] Alternatively, the electron transport layer can be made of materials such as ZnO or ZnMgO.

[0076] Optionally, the hole transport layer material includes, but is not limited to, polyvinylcarbazole (PVK), poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB), N,N'-diphenyl-N,N'-di(3-methylbenzene)-(1,1'-biphenyl)-4,4'-diamine (TPD), 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA), or N,N'-diphenyl-N,N'-di(1-naphthyl)-1,1'-biphenyl-4-4'-diamine (NPB).

[0077] Optionally, the material of the hole injection layer includes, but is not limited to, PEDOT:PSS, MoOx, NiOx, and CuOx.

[0078] Alternatively, the anode material may include, but is not limited to, indium tin oxide (ITO).

[0079] Optionally, the cathode material can be, but is not limited to, Al, Mg:Ag.

[0080] Specifically, the light-emitting principle of the quantum dot device shown in Figures 3 and 4 is as follows: holes in the anode 40 and cathode 70 are injected into the quantum dot layer 10 to emit light in a composite manner.

[0081] In some embodiments, the quantum dot device provided in this disclosure is a quantum dot light-emitting diode, and its light emission mode can be bottom light emission, top light emission, and double-sided light emission.

[0082] In some embodiments, the quantum dot devices provided in this disclosure may also be photodetectors, photovoltaic solar cells, etc., but are not limited thereto.

[0083] Based on the same inventive concept, this disclosure also provides a method for fabricating quantum dot devices, used to fabricate the quantum dot devices shown in Figures 3 and 4. As shown in Figure 5, the fabrication method may include:

[0084] S501. A carrier transport thin film is formed on one side of the substrate; the material of the carrier transport thin film includes a carrier transport material and a crosslinking agent;

[0085] S502. Expose the carrier transport thin film;

[0086] S503. A quantum dot film is formed on the side of the exposed carrier transport film away from the substrate; the material of the quantum dot film is the quantum dot material provided in the embodiments of this disclosure.

[0087] S504. Develop the exposed carrier transport film to remove the unexposed areas of the carrier transport film and quantum dot film, so as to form a patterned carrier transport layer and quantum dot layer in the exposed area.

[0088] The quantum dot device fabrication method provided in this disclosure eliminates the need for ligand exchange in the quantum dot material. Directly synthesized quantum dot materials with initial ligands can be used for photolithographic patterning, reducing potential efficiency degradation during ligand exchange. Furthermore, during photolithographic patterning, this disclosure eliminates the need to add a photosensitive crosslinking agent to the quantum dot material and avoids exposure treatment; only the carrier transport layer needs exposure. This reduces the risk of device performance degradation due to defects such as oxidation of the quantum dot surface caused by light exposure. Therefore, this fabrication method maximizes the preservation of the intrinsic efficiency of the quantum dot material, thereby improving the efficiency of the quantum dot device.

[0089] In some embodiments, step S501 above, which forms a carrier transport film on one side of the substrate, may form a hole transport film. The material of the hole transport film includes a hole transport material and an azide crosslinking agent.

[0090] In some embodiments, step S501 above, which forms a carrier transport film on one side of the substrate, may be an electron transport film. The material of the electron hole transport film includes an electron transport material and a diazonoquinone crosslinking agent.

[0091] In some embodiments, in the above-described preparation method provided in this disclosure, after performing step S504 to form a patterned carrier transport layer and a quantum dot layer in the exposure area, as shown in FIG6, the method further includes:

[0092] S601. Drop a ZnX2 ethanol solution onto the side of the quantum dot layer away from the substrate, soak for a preset time, and then wash the quantum dot layer with ethanol to remove X2. - Coordinated on the bulk surface of the quantum dot material; wherein, X - For Cl - ,Br - Or I -This allows for the passivation of the quantum dot layer with inorganic ions, thereby passivating defects on the quantum dot surface caused by the initial ligand detachment and improving luminescence efficiency.

[0093] The following specific embodiments further illustrate how the fabrication method of the quantum dot device provided in this disclosure can form a patterned quantum dot layer, but this disclosure is not limited to the following embodiments.

[0094] Example 1:

[0095] First, a green quantum dot material was prepared, with oleylamine (OA) as the initial ligand. This green quantum dot material is represented as GQD-OA, and the OA content is approximately 8%. The experimental method is as follows: conventional GQD-OA with an oleylamine content of approximately 13% was prepared using conventional methods. Then, the conventionally synthesized GQD-OA was washed five times with methanol solvent to obtain the quantum dot material disclosed in this invention. As shown in Figure 7, which displays the thermogravimetric analysis (TGA) curves of the conventionally synthesized and the green quantum dot materials of this invention, it can be seen that the proportion of oleylamine in the conventionally synthesized quantum dot material (solid line) is 12.4%. In the quantum dot material of this invention (dashed line), the initial ligand content was reduced from 12.4% to 8.4% due to multiple washings of the conventionally synthesized quantum dot material. Therefore, the initial ligand content in the quantum dot material of this invention is less than that in the conventional quantum dot material.

[0096] Secondly, the fabrication of green upright quantum dot devices follows these steps:

[0097] (1) A patterned anode is prepared on one side of the substrate, and the anode material can be ITO.

[0098] (2) The substrate with the anode is cleaned in sequence with water, ethanol and acetone, and then dried with a nitrogen gun for later use.

[0099] (3) Form a hole injection layer on the side of the anode away from the substrate, for example by spin coating PEDOT:PSS.

[0100] (4) Form a hole transport film by spin-coating TFB+crosslinking agent on the side of the hole injection layer away from the substrate;

[0101] (5) Add a photo mask to the hole transport film and perform alignment exposure;

[0102] (6) A green quantum dot film is formed by coating the side of the hole transport film away from the substrate with the green quantum dot material with an initial ligand content of 8.4%.

[0103] (7) Develop the exposed hole transport film to remove the hole transport film and green quantum dot film in the unexposed area, so as to form a patterned hole transport layer and green quantum dot layer in the exposed area.

[0104] As shown in Figure 8, Figure 8 is a fluorescence photograph of the green quantum dot layer prepared by the above steps (1)-(7). It can be seen that the green quantum dot layer has a uniform pattern and complete morphology, and emits light uniformly.

[0105] As shown in Figure 9, Figure 9(a) is a SEM image of the exposed area after development. It can be seen that the quantum dot layer pattern left in the exposed area is relatively dense. Theoretically, the initial ligand content in the exposed area will be washed away in small amounts after development, thus reducing it to approximately 7.4%-8.4%. Figure 9(b) is a SEM image of the unexposed area after development. It can be seen that there is basically no residual quantum dot material in the unexposed area, proving that the quantum dot device fabrication method of this disclosure has a good development effect and basically no QD residue.

[0106] As shown in Figure 10, Figure 10(a) shows the thickness data of the hole transport film (represented by HTL) formed in step (4) above, obtained by step meter testing. It can be seen that the thickness of the hole transport film measured by step meter is 25.5 nm. Figure 10(b) shows the sum of the thicknesses of the hole transport layer (HTL) and the green quantum dot layer (GQD) formed in step (7) above, obtained by step meter testing. It can be seen that the sum of the thicknesses of HTL and GQD is 40.1 nm. Therefore, the thickness of GQD is about 14.6 nm, approximately 15 nm. The quantum dot layer is neither too thick nor too thin.

[0107] Comparative Example 1: The difference from Example 1 is that Comparative Example 1 uses conventionally synthesized quantum dot materials (oleylamine accounts for 12.4% of the quantum dot materials) to prepare a green upright quantum dot device.

[0108] As shown in Figure 11, which is a fluorescence photograph of the green quantum dot layer prepared in Comparative Example 1, it can be seen that the pattern of the green quantum dot layer is severely damaged and cannot form the pre-designed patterned quantum dot film.

[0109] As shown in Figure 12, which is a SEM image of the exposed area of ​​Comparative Example 1 after development, it can be seen that when the initial ligand content is relatively high (12.4%), the quantum dot material has good solubility in the developer, which makes it impossible to form a uniform and dense film, and thus the quantum dot layer cannot be patterned.

[0110] A comparison of Example 1 and Comparative Example 1 shows that when the initial ligand content is low (e.g., the initial ligand content of green quantum dot materials ranges from 7-10%, preferably 8-9%), patterned quantum dot layers can be formed due to their significantly reduced solubility in the developer. However, when the initial ligand content exceeds 10% (the initial ligand content of conventional GQD-OA is 12.4%), patterned quantum dot layers cannot be formed. This conclusion also applies to the patterning of red and blue quantum dot layers. Based on these results, this disclosure can fabricate patterned devices with R / G / B three-color quantum dot layers, and essentially achieves a residue-free process.

[0111] The quantum dot device for forming a full-color R / G / B three-color quantum dot layer will be further explained below with reference to specific embodiments.

[0112] Example 3:

[0113] Taking a quantum dot device as an example of a positive bottom-emitting structure, a quantum dot device with a full-color R / G / B three-color quantum dot layer is prepared. The synthesis methods of the red and blue quantum dot materials disclosed in this paper are the same as the synthesis method of the green quantum dot material in Example 1 above. The initial ligand content of the three colors of quantum dot materials can be referred to the relevant examples in the aforementioned quantum dot material. The specific preparation steps are as follows:

[0114] (1) As shown in Figure 13A, a patterned anode 40 is prepared on one side of the substrate 30. The anode 40 material can be ITO. The substrate 30 with the anode 40 is then cleaned with water, ethanol and acetone in sequence, and then dried with a nitrogen gun for later use.

[0115] (2) As shown in Figure 13B, a hole injection layer 50 is formed by spin-coating PEDOT:PSS on the side of the anode 40 away from the substrate 30, and a hole transport film 20' is formed by spin-coating TFB+crosslinking agent on the side of the hole injection layer 50 away from the substrate 30, and a first photo mask (photomask 100) is added to the hole transport film 20' for alignment exposure.

[0116] (3) As shown in Figure 13C, the red quantum dot material disclosed herein is coated on the side of the hole transport film 20' away from the substrate 30 after exposure to form a red quantum dot film RQD'.

[0117] (4) As shown in Figure 13D, the exposed hole transport film 20' is developed to remove the unexposed area hole transport film 20' and red quantum dot film RQD', so as to form a patterned hole transport layer (i.e. carrier transport layer 20) and red quantum dot unit RQD in the exposed area.

[0118] (5) As shown in Figure 13E, a hole transport film 20' is formed by spin-coating TFB+ crosslinking agent on the side of the red quantum dot unit RQD away from the substrate 30, and a second photo mask (photomask 200) is added to the hole transport film 20' for alignment exposure.

[0119] (6) As shown in Figure 13F, the green quantum dot material provided herein is coated on the side of the hole transport film 20' away from the substrate 30 after exposure to form a green quantum dot film GQD'.

[0120] (7) As shown in Figure 13G, the exposed hole transport film 20' is developed to remove the unexposed area hole transport film 20' and green quantum dot film GQD', so as to form a patterned hole transport layer (i.e. carrier transport layer 20) and green quantum dot unit GQD in the exposed area.

[0121] (8) As shown in Figure 13H, a hole transport film 20' is formed by spin-coating TFB+ crosslinking agent on the side of the green quantum dot unit GQD away from the substrate 30, and a third photo mask (photomask 300) is added to the hole transport film 20' for alignment exposure.

[0122] (9) As shown in Figure 13I, the blue quantum dot material disclosed herein is coated on the side of the hole transport film 20' away from the substrate 30 after exposure to form a blue quantum dot film BQD'.

[0123] (10) As shown in Figure 13J, the hole transport film 20' after exposure is developed to remove the hole transport film 20' and the blue quantum dot film BQD' in the unexposed area, so as to form a patterned hole transport layer (i.e. carrier transport layer 20) and blue quantum dot units BQD in the exposed area, thereby forming a quantum dot layer 10 including red quantum dot units RQD, green quantum dot units GQD and blue quantum dot units BQD.

[0124] (11) As shown in Figure 13K, ZnO material is spin-coated on the side of the quantum dot layer 10 away from the substrate 30 to form an electron transport layer 60, and Al is vapor-deposited on the side of the electron transport layer 60 away from the substrate 30 to form a cathode 70, and the quantum dot device is packaged.

[0125] Example 4: Since the quantum dot material provided in this embodiment is a conventional quantum dot material that retains a low initial ligand content after multiple washings, some of the washed-off initial ligands may cause some defects. Therefore, after step (10) of Example 3 and before step (11) of Example 3, the following may be included: as shown in FIG14A, an ethanol solution of ZnX2 is drop-coated on the side of the quantum dot layer 10 away from the substrate 30, soaked for a preset time (e.g., about three minutes), and then the quantum dot layer 10 is washed with ethanol (e.g., washed twice) to remove X2. - (i.e., inorganic ion B) is coordinated on the bulk surface of the quantum dot material; wherein, X - For Cl - ,Br - Or I - This allows for the passivation of the quantum dot layer 10 with inorganic ions, thereby passivating defects on the surface of the quantum dot matrix caused by the initial ligand detachment and improving luminescence efficiency. Then, step (11) of Example 3 is performed again to form the structure shown in Figure 14B.

[0126] Example 5:

[0127] Taking a quantum dot device with an inverted structure as an example, the fabrication steps of a full-color R / G / B three-color quantum dot layer quantum dot device are as follows:

[0128] (1) As shown in Figure 15A, a cathode 70 is prepared on one side of the substrate 30. The cathode 70 material can be Al. The substrate 30 with the cathode 70 is then cleaned with water, ethanol and acetone in sequence, and then dried with a nitrogen gun for later use.

[0129] (2) As shown in Figure 15B, ZnO + crosslinking agent is spin-coated on the side of the cathode 70 away from the substrate 30 to form an electron transport thin film 20”, and a first photo mask (photomask 100) is added to the electron transport thin film 20” for alignment exposure.

[0130] (3) As shown in Figure 15C, the red quantum dot material disclosed herein is coated on the side of the exposed electron transport film 20” away from the substrate 30 to form a red quantum dot film RQD'.

[0131] (4) As shown in Figure 15D, the exposed electron transport film 20” is developed to remove the unexposed electron transport film 20” and red quantum dot film RQD', so as to form a patterned electron transport layer (i.e. carrier transport layer 20) and red quantum dot unit RQD in the exposed area.

[0132] (5) As shown in Figure 15E, ZnO+ crosslinking agent is spin-coated on the side of the red quantum dot unit RQD away from the substrate 30 to form an electron transport thin film 20”, and a second photo mask (photomask 200) is added to the electron transport thin film 20” for alignment exposure.

[0133] (6) As shown in Figure 15F, the green quantum dot material disclosed herein is coated on the side of the exposed electron transport film 20” away from the substrate 30 to form a green quantum dot film GQD'.

[0134] (7) As shown in Figure 15G, the exposed electron transport film 20” is developed to remove the unexposed electron transport film 20” and green quantum dot film GQD', so as to form a patterned electron transport layer (i.e. carrier transport layer 20) and green quantum dot unit GQD in the exposed area.

[0135] (8) As shown in Figure 15H, ZnO+ crosslinking agent is spin-coated on the side of the green quantum dot unit GQD away from the substrate 30 to form an electron transport thin film 20”, and a third photo mask (photomask 300) is added to the electron transport thin film 20” for alignment exposure.

[0136] (9) As shown in Figure 15I, the blue quantum dot material disclosed herein is coated on the side of the exposed electron transport film 20” away from the substrate 30 to form a blue quantum dot film BQD'.

[0137] (10) As shown in Figure 15J, the exposed electron transport film 20” is developed to remove the unexposed area electron transport film 20” and blue quantum dot film BQD’, so as to form a patterned electron transport layer (i.e. carrier transport layer 20) and blue quantum dot unit BQD in the exposed area, thereby forming a quantum dot layer 10 including red quantum dot unit RQD, green quantum dot unit GQD and blue quantum dot unit BQD.

[0138] (11) As shown in Figure 15K, an ethanol solution of ZnX2 is drop-coated onto the side of the quantum dot layer 10 away from the substrate 30. After soaking for a preset time (e.g., about three minutes), the quantum dot layer 10 is washed with ethanol (e.g., twice) to remove X2. - (i.e., inorganic ion B) is coordinated on the bulk surface of the quantum dot material; wherein, X - For Cl - ,Br - Or I - This allows for the passivation of the quantum dot layer 10 with inorganic ions, thereby passivating defects on the quantum dot surface caused by the initial ligand detachment and improving luminescence efficiency.

[0139] (12) As shown in Figure 15L, a hole transport layer 80 is formed by spin coating TFB on the side of the quantum dot layer 10 away from the substrate 30, and a hole injection layer 50 is formed by spin coating PEDOT:PSS on the side of the hole transport layer 80 away from the substrate 30, and an anode 40 is formed on the side of the hole injection layer 50 away from the substrate 30. The quantum dot device is then encapsulated.

[0140] Based on the same inventive concept, this disclosure also provides a display device, including the quantum dot device described above. The principle by which this display device solves the problem is similar to that of the aforementioned quantum dot device; therefore, the implementation of this display device can refer to the implementation of the aforementioned quantum dot device, and the repetitions will not be repeated here.

[0141] In specific implementation, the display device provided in the embodiments of this disclosure is an organic light-emitting display device.

[0142] In specific implementation, the display device provided in the embodiments of this disclosure may be a full-screen display device or a flexible display device, etc., and is not limited thereto.

[0143] In specific implementations, the display device provided in this disclosure can be a full-screen mobile phone as shown in FIG16. The display device can also be any product or component with display function, such as a tablet computer, television, monitor, laptop computer, digital photo frame, or navigator. Other essential components of this display device are understood by those skilled in the art and will not be described in detail here, nor should they be construed as limiting this disclosure. Implementation of this display device can refer to the embodiments of the quantum dot light-emitting device described above; repeated details will not be repeated.

[0144] In specific implementations, the display device provided in the embodiments of this disclosure may also include other functional film layers well known to those skilled in the art, which will not be described in detail here.

[0145] This disclosure provides a quantum dot material, quantum dot ink, quantum dot device, and its preparation method. Since the initial ligand content of the quantum dot material is 7%-11%, compared to approximately 13% for conventionally synthesized quantum dot materials, the lower initial ligand content in this disclosure does not affect the luminescence properties of the quantum dot material. Furthermore, the lower initial ligand content results in relatively poor colloidal stability and reduced solubility, making it less susceptible to dissolution and rinsing by the developer during photolithography. This allows for better adhesion to the substrate side, transforming the less easily dissolved quantum dot material into patterned quantum dots. Thus, the quantum dot material of this disclosure does not require ligand exchange; it can be directly synthesized with initial ligands for photolithographic patterning, reducing potential efficiency degradation during ligand exchange. Moreover, during photolithographic patterning, this disclosure does not require the addition of a photosensitive crosslinking agent or exposure treatment, maximizing the preservation of the intrinsic efficiency of the quantum dot material and thereby improving the efficiency of the quantum dot device.

[0146] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include such modifications and variations.

Claims

1. A quantum dot material, wherein, It includes a quantum dot body and an initial ligand that coordinates with the surface of the quantum dot body, wherein the initial ligand accounts for 7%-11% of the quantum dot material.

2. The quantum dot material as described in claim 1, wherein, In the thermogravimetric analysis curves, the quantum dot material loses 7%-11% of its weight in the range of 500-600℃.

3. The quantum dot material as described in claim 1 or 2, wherein, The initial ligand has a carbon chain length greater than or equal to 10, and the initial ligand accounts for 7%-10% of the quantum dot material.

4. The quantum dot material as described in claim 3, wherein, The quantum dot material emits red light, and the initial ligand accounts for 8.5%-9.5% of the quantum dot material. The quantum dot material emits green light, and the initial ligand accounts for 8%-9% of the quantum dot material. The quantum dot material emits blue light, and the initial ligand accounts for 7.5%-8.5% of the quantum dot material.

5. The quantum dot material as described in claim 4, wherein, The initial ligand includes at least one of oleic acid and oleylamine.

6. The quantum dot material as described in claim 1 or 2, wherein, The initial ligand has a carbon chain length of less than 10, and the initial ligand accounts for 8%-11% of the quantum dot material.

7. The quantum dot material as described in claim 6, wherein, The quantum dot material emits red light, and the initial ligand accounts for 9.5%-10.5% of the quantum dot material. The quantum dot material emits green light, and the initial ligand accounts for 9%-10% of the quantum dot material. The quantum dot material emits blue light, and the initial ligand accounts for 8.5%-9.5% of the quantum dot material.

8. The quantum dot material as described in claim 7, wherein, The initial ligand includes octanoic acid.

9. The quantum dot material according to any one of claims 1-8, wherein, The quantum dot bulk includes CdS, CdSe, InP, ZnSe, PbS, CsPbCl3, CsPbBr3, CsPhI3, CdS / ZnS, CdSe / ZnS, PbS / ZnS, InP / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, or CsPhI3 / ZnS.

10. A quantum dot ink, wherein, Includes solvents and quantum dot materials as described in any one of claims 1-9.

11. A quantum dot device, wherein, Includes a quantum dot layer, wherein the material of the quantum dot layer is the quantum dot material as described in any one of claims 1-9.

12. The quantum dot device of claim 11, wherein, The quantum dot layer includes red quantum dot units, green quantum dot units, and blue quantum dot units. The red quantum dot units, green quantum dot units, and blue quantum dot units do not overlap with each other. The proportion of the initial ligand in the quantum dot material decreases sequentially among the red quantum dot units, green quantum dot units, and blue quantum dot units.

13. The quantum dot device of claim 12, wherein, The surfaces of the quantum dot bodies in the red, green, and blue quantum dot units are also coordinated with inorganic ions.

14. The quantum dot device of claim 13, wherein, The inorganic ions include Cl. - ,Br - I - At least one of them.

15. The quantum dot device according to any one of claims 11-14, wherein, It also includes a carrier transport layer located on one side of the quantum dot layer, the carrier transport layer having a cross-linked network structure.

16. The quantum dot device of claim 15, wherein, The carrier transport layer is either a hole transport layer or an electron transport layer.

17. The quantum dot device according to any one of claims 11-16, wherein, The thickness of the quantum dot layer is 15nm-30nm.

18. A method for fabricating a quantum dot device, wherein, include: A carrier transport thin film is formed on one side of the substrate; The carrier transport thin film is made of a carrier transport material and a crosslinking agent; The carrier transport film is exposed; A quantum dot film is formed on the side of the exposed carrier transport film away from the substrate; The quantum dot film is made of the quantum dot material as described in any one of claims 1-9; The exposed carrier transport film is developed to remove the unexposed areas of the carrier transport film and the quantum dot film, so as to form a patterned carrier transport layer and quantum dot layer in the exposed area.

19. The preparation method according to claim 18, wherein, After forming the patterned carrier transport layer and quantum dot layer in the exposure area, the method further includes: An ethanol solution of ZnX2 was drop-coated onto the side of the quantum dot layer away from the substrate. After soaking for a predetermined time, the quantum dot layer was washed with ethanol to remove X2. - Coordinated on the quantum dot bulk surface of the quantum dot material; wherein, X - For Cl - ,Br - Or I - .

Images