A quantum dot transfer method and QLED preparation method

Abstract

The present invention discloses a quantum dot transfer method and a QLED preparation method, the transfer method comprising: water treatment and heat treatment of a first quantum dot to obtain a second quantum dot that is insoluble in polar and non-polar solvents; wherein the first quantum dot has a first ligand and the second quantum dot has a second ligand; the first quantum dot is made into a first film, and the second quantum dot is made into a second film; the second film is dipped for the first time by a transfer head, and the first film is dipped for the second time after the first dipping is completed; and the substrate to be transferred is printed using the transfer head dipped with the first film and the second film. The present invention dips two quantum dots with ligands of different properties onto the transfer head at the same time, so that the process steps required for transferring different quantum dots can be reduced, providing a simpler method for printing QLED-inverted QLED or multi-color QLED layers, and at the same time reducing the cost of QLED printing.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a quantum dot transfer method and a QLED preparation method. Background Art

[0002] As an important semiconductor structure, the emerging quantum dots make quantum dot light-emitting diodes (QLEDs) with the advantages of high quantum efficiency, low cost, and wide color gamut, and have great application prospects in the field of high-precision display devices. In display devices, each pixel requires an RGB primary color light-emitting block. The process of combining multiple block components and multiple pixels into a screen is called arraying. At present, high-end display devices usually pursue high resolution and thin finished products, which creates a demand for high-precision pixel thin film arraying. In traditional methods of high-precision pixel arraying, such as electrodeposition and photolithography, high requirements are placed on device substrate processing, and inkjet printing is difficult to achieve high-precision printing. Compared with the above methods, transfer printing is more suitable for high-precision arraying processes.

[0003] The characteristic of transfer printing is that the pixel material is first arrayed into a thin film in a non-substrate environment, and then transplanted to the device substrate through a transfer head to form an LED. In this way, the substrate does not require large-area patterning, nor does it need to be kept in a long-term and stable environment for the film formation of the pixel material. In other words, the transfer method does not require high substrate processing, and the pixel material can be transferred after arraying in a non-substrate environment, which has higher flexibility. The patterning process and the thin film are separated in the processing of the transfer head and the transfer material, which reduces the process difficulties brought by high precision. However, the separation process of the transfer method also brings the disadvantages of the transfer technology, such as the many repeated processes of the transfer method, as well as the potential cleaning loss and alignment errors. Among them, the arraying of multi-color and large-area LEDs on the substrate requires repeated transfers, and each transfer requires holes to be left for other color LEDs, which will aggravate the loss and error caused by the repeated process, thereby increasing the process cost.

[0004] Therefore, how to reduce the process steps of transfer printing and lower the process cost is a problem that technical personnel in this field need to solve. Summary of the invention

[0005] The embodiments of the present invention provide a quantum dot transfer method and a QLED preparation method, which aim to reduce the quantum dot transfer process, improve the QLED printing efficiency, and reduce the QLED printing cost.

[0006] An embodiment of the present invention provides a quantum dot transfer method, comprising:

[0007] The first quantum dot is subjected to water treatment and heat treatment to obtain a second quantum dot that is insoluble in polar and non-polar solvents; wherein the first quantum dot has a first ligand and the second quantum dot has a second ligand;

[0008] The first quantum dots are formed into a first thin film, and the second quantum dots are formed into a second thin film;

[0009] Dipping the second film for the first time by a transfer head, and dipping the first film for the second time after the first dipping is completed;

[0010] The transferred substrate is printed using a transfer head dipped with the first film and the second film.

[0011] Furthermore, the first ligand is an oleic acid ligand, and the second ligand is a hydroxyl ligand.

[0012] Furthermore, the first quantum dots are subjected to water treatment and heat treatment to obtain second quantum dots that are poorly soluble in polar and non-polar solvents, comprising:

[0013] According to the following formula, the first quantum dots are subjected to water treatment to obtain the second quantum dots:

[0014] QD-C 18 H 34 O2+H2O=QD-OH+C 18 H 35 O2

[0015] Among them, QD-C 18 H 34 O2 represents the first quantum dot with oleic acid ligand, QD-OH represents the second quantum dot with hydroxyl ligand, H2O represents water, C 18 H 35 O2 is polyethylene glycol stearate.

[0016] Furthermore, the heating time of the heating treatment is 30-80 minutes.

[0017] Furthermore, the step of forming the first quantum dots into a first film includes:

[0018] The first quantum dots are made into a first thin film by using Langmuir trough self-film forming technology.

[0019] Furthermore, the step of making the second quantum dots into a second film comprises:

[0020] The second quantum dots are made into a second thin film by using any of Langmuir trough self-film forming technology, spin coating technology or deposition technology.

[0021] Furthermore, before the first quantum dots are subjected to water treatment, the process includes:

[0022] The first quantum dots are made into a third film by using a spin coating technique.

[0023] Furthermore, it also includes:

[0024] Pre-patterning the transfer head using photolithography technology;

[0025] The method of printing the transferred substrate by using a transfer head dipped with the first film and the second film comprises:

[0026] The first film and the second film are printed onto the substrate based on a transfer head subjected to a patterning process, and an RGB arrangement is formed on the substrate.

[0027] Furthermore, the material of the transfer head is polydimethylsiloxane.

[0028] An embodiment of the present invention further provides a QLED preparation method, including the quantum dot transfer method as described above.

[0029] The embodiment of the present invention provides a quantum dot transfer method and a QLED preparation method, the transfer method comprising: water treatment and heat treatment of the first quantum dot to obtain a second quantum dot that is insoluble in polar and non-polar solvents; wherein the first quantum dot has a first ligand and the second quantum dot has a second ligand; the first quantum dot is made into a first film, and the second quantum dot is made into a second film; the second film is dipped for the first time by a transfer head, and the first film is dipped for the second time after the first dipping is completed; the substrate to be transferred is printed using the transfer head dipped with the first film and the second film. The embodiment of the present invention achieves the effect of differentiating the solubility properties of the two quantum dots by water treatment of the quantum dots, and then the two quantum dots with ligands of different properties are dipped onto the transfer head simultaneously through two consecutive dipping actions, so that the process steps required for transferring different quantum dots can be reduced, and a simpler method for printing QLED-inverted QLED or multi-color QLED layers is provided, and the printing cost of QLED can also be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0031] Figure 1A schematic diagram of a process of a quantum dot transfer method provided by an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of the principle of a quantum dot transfer method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0035] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0036] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0037] See below Figure 1 , an embodiment of the present invention provides a quantum dot transfer method, which specifically includes: steps S101 to S104.

[0038] S101, subjecting the first quantum dot to water treatment and heat treatment to obtain a second quantum dot that is poorly soluble in polar and non-polar solvents; wherein the first quantum dot has a first ligand, and the second quantum dot has a second ligand;

[0039] S102, forming the first quantum dots into a first thin film, and forming the second quantum dots into a second thin film;

[0040] S103, dipping the second film for the first time by using a transfer head, and continuing to dip the first film for the second time after the first dipping is completed;

[0041] S104, using a transfer head dipped with the first film and the second film to print on the transferred substrate.

[0042] Combination Figure 2 In this embodiment, the first quantum dots with the first ligand are first treated with water, and then heated in the atmosphere of the water treatment, so that the ligand part of the first quantum dots undergoes a substitution reaction, thereby obtaining the second quantum dots with the second ligand and being insoluble in polar and non-polar solvents. Then, the first quantum dots are made into a first film on the one hand, and the second quantum dots are made into a second film on the other hand. Subsequently, the second film is first dipped with a transfer head, and then the first film is dipped, and then the dipped first film and second film are transferred to the substrate to be transferred.

[0043] In this embodiment, the quantum dots are treated with water to achieve the effect of differentiating the solubility properties of the two quantum dots, and then the two quantum dots with ligands of different properties are simultaneously dipped onto the transfer head through two consecutive dipping actions. This can reduce the process steps required for transferring different quantum dots, provide a simpler method for printing QLED-inverted QLED or multi-color QLED layers, and also reduce the cost of QLED printing.

[0044] In one embodiment, the first ligand is an oleic acid ligand, and the second ligand is a hydroxyl ligand.

[0045] Oleic acid is a monounsaturated omega-9 fatty acid found in plants and animals. Its chemical formula is C 18 H 34 O2. Oleic acid can be hydrogenated to obtain stearic acid. The quantum dots in this embodiment are divided into inner and outer ligands, the inner layer is IV, II-VI, IV-VI or III-V elements, thereby providing a PN junction for the quantum dots, and the outer ligand is used to protect the inner layer structure and provide solubility in the solvent. Oleic acid ligand quantum dots refer to quantum dot particles whose ligand molecules are Z-9 octadecenoic acid.

[0046] Hydroxyl is a common polar group with the chemical formula -OH. Hydroxyl has some similar properties to water. Hydroxyl is a typical polar group that can form hydrogen bonds with water. It exists in the form of negatively charged ions (OH-) in aqueous solutions of inorganic compounds, called hydroxide.

[0047] In one embodiment, the step of subjecting the first quantum dots to water treatment and heat treatment to obtain second quantum dots that are poorly soluble in polar and non-polar solvents comprises:

[0048] According to the following formula, the first quantum dots are subjected to water treatment to obtain the second quantum dots:

[0049] QD-C18 H 34 O2+H2O=QD-OH+C 18 H 35 O2

[0050] Among them, QD-C 18 H 34 O2 represents the first quantum dot with oleic acid ligand, QD-OH represents the second quantum dot with hydroxyl ligand, H2O represents water, C 18 H 35 O2 is polyethylene glycol stearate.

[0051] As can be seen from the above formula, the polarity of the second quantum dot QD comes from the polar ligand -OH. The so-called polarity is not exactly the same as the polar compound. The second quantum dot can have the property of being difficult to dissolve in both non-polar solvents and polar solvents through the hydroxyl ligand, and this property will prevent the second quantum dot from being peeled off in the LB tank later.

[0052] In addition, the heating time of the heating treatment described in this embodiment can be 30-80 minutes, for example, the heating time is 50 minutes. Of course, in other embodiments, the heating time can also be set accordingly according to actual needs to ensure that the polarity of the obtained second quantum dots is reliable and stable.

[0053] In one embodiment, forming the first quantum dots into a first film includes:

[0054] The first quantum dots are made into a first thin film by using Langmuir trough self-film forming technology.

[0055] Combination Figure 2 It can be seen that the first film is prepared by the LB (Langmuir-Blodgett trough) trough in this embodiment. The LB trough disperses the molecules at the gas-liquid interface in the trough, and then gradually compresses the area occupied by the molecules on the liquid surface through the sliding barriers on both sides of the trough, so that they spontaneously and tightly arrange into a monolayer, thereby obtaining the corresponding LB film (Langmuir-Blodgett film). LB film refers to when molecules have hydrophobic (water-hating) and hydrophilic (water-loving) functional groups, they gather in a predictable way at the gas-liquid interface and form a monolayer. The film transferred to the solid substrate is the LB film.

[0056] Furthermore, the step of making the second quantum dots into a second film comprises:

[0057] The second quantum dots are made into a second thin film by using any of Langmuir trough self-film forming technology, spin coating technology or deposition technology.

[0058] The first thin film described in this embodiment is produced by Langmuir trough self-film forming technology, and the second thin film can also be produced by Langmuir trough self-film forming technology. Of course, it can also be produced by film forming technologies such as spin coating technology or deposition technology.

[0059] Spin coating is the abbreviation of the rotary coating method. It is a coating process that relies on the centrifugal force and gravity generated when the workpiece rotates to spread the coating droplets that fall on the workpiece on the surface of the workpiece. Spin coating is a commonly used preparation method for organic light-emitting diodes, and the main equipment used is a coating machine. The spin coating method includes three steps: batching, high-speed rotation, and volatilization film formation. The thickness of the film is controlled by controlling the coating time, rotation speed, droplet volume, and the concentration and viscosity of the solution used.

[0060] Deposition technology refers to the thin film deposition process, which is mainly divided into two categories: physical vapor deposition and chemical vapor deposition. Among them, physical vapor deposition (PVD) technology refers to the use of physical methods under vacuum conditions to vaporize the material source - solid or liquid surface into gaseous atoms, molecules or partially ionized into ions, and through a low-pressure gas (or plasma) process, deposit a thin film with some special functions on the surface of the substrate. At present, physical vapor deposition technology can not only deposit metal films and alloy films, but also compounds, ceramics, semiconductors, polymer films, etc. Common methods for depositing thin films include vacuum evaporation coating, sputtering coating and ion plating.

[0061] Furthermore, before the first quantum dots are subjected to water treatment, the process includes:

[0062] The first quantum dots are made into a third film by using a spin coating technique.

[0063] That is to say, the water treatment process in this embodiment directly processes the quantum dots that have been spin-coated into films, rather than pure quantum dots.

[0064] In one embodiment, the quantum dot transfer method further comprises:

[0065] Pre-patterning the transfer head using photolithography technology;

[0066] The method of printing the transferred substrate by using a transfer head dipped with the first film and the second film comprises:

[0067] The first film and the second film are printed onto the substrate based on a transfer head subjected to a patterning process, and an RGB arrangement is formed on the substrate.

[0068] In this embodiment, the transfer head is patterned in advance so that it can meet the transfer pattern requirements. After the first film and the second film are dipped by the transfer head, the first film and the second film are transferred to the substrate, and due to the patterning treatment, the first film and the second film will be printed on the substrate in the form of RGB arrangement. Specifically, the material of the transfer head described in this embodiment is polydimethylsiloxane, that is, a PDMS transfer head. Polydimethylsiloxane (PDMS) is an organosilicon polymer, which has been widely used to make a variety of micro-nano devices due to its advantages such as easy stretchability, high light transmittance, easy molding and high biocompatibility.

[0069] In addition, when the first ligand is an oleic acid ligand and the second ligand is a hydroxyl ligand, when the transfer head is dipped, the first quantum dots with oleic acid ligands can be pressed into the holes of the transfer head with the help of the LB tank liquid phase substrate, while the second quantum dots with insoluble hydroxyl ligands will not be peeled off in the liquid in the tank. Specifically, when the transfer head is dipped in polar hydroxyl QDs, the substrate of hydroxyl QDs is solid, and what is dipped is a single contact surface that is only attached to the shallowest layer. When the transfer head is dipped in non-polar oleic acid QDs, since the first film corresponding to the oleic acid QDs is formed through the LB tank, the QD film substrate is liquid, so when the transfer head is pressed in, the first film corresponding to the oleic acid QDs will change shape according to the transfer head groove, thereby pressing into the groove hole. Here, the LB tank film-forming substrate is liquid, forming a single-layer film similar to the oil film on the water surface, and the non-polar solvent is the liquid phase substrate in the LB tank.

[0070] It should also be noted that although Figure 2 The number of quantum dots is shown in FIG. 1 , but this is because the quantitative relationship of QDs (the quantitative relationship of the polar and non-polar QDs dipped) is difficult to express, so this embodiment is Figure 2 In the figure, a circle represents a QD film with a certain area.

[0071] An embodiment of the present invention further provides a QLED preparation method, which includes the quantum dot transfer method as described above.

[0072] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of this application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of this application.

[0073] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A quantum dot transfer method, characterized in that: include: The first quantum dot is subjected to water treatment and heat treatment to obtain a second quantum dot that is insoluble in polar and non-polar solvents; wherein the first quantum dot has a first ligand, and the second quantum dot has a second ligand; the first ligand is an oleic acid ligand, and the second ligand is a hydroxyl ligand; The first quantum dots are formed into a first thin film, and the second quantum dots are formed into a second thin film; Dipping the second film for the first time by a transfer head, and dipping the first film for the second time after the first dipping is completed; Printing the transferred substrate using a transfer head dipped with the first film and the second film; The step of subjecting the first quantum dots to water treatment and heating treatment to obtain second quantum dots that are poorly soluble in polar and non-polar solvents comprises: According to the following formula, the first quantum dots are subjected to water treatment to obtain the second quantum dots: QD-C 18 H 34 O2+H2O=QD-OH+C 18 H 35 O2 Among them, QD-C 18 H 34 O2 represents the first quantum dot with oleic acid ligand, QD-OH represents the second quantum dot with hydroxyl ligand, H2O represents water, C 18 H 35 O2 is polyethylene glycol stearate.

2. The quantum dot transfer method according to claim 1, characterized in that: The heating time of the heating treatment is 30-80 minutes.

3. The quantum dot transfer method according to claim 1, characterized in that: The step of forming the first quantum dots into a first film comprises: The first quantum dots are made into a first thin film by using Langmuir trough self-film forming technology.

4. The quantum dot transfer method according to claim 1, characterized in that: The step of forming the second quantum dots into a second film comprises: The second quantum dots are made into a second thin film by using any of Langmuir trough self-film forming technology, spin coating technology or deposition technology.

5. The quantum dot transfer method according to claim 1, characterized in that: Before the first quantum dot is subjected to water treatment, the method comprises: The first quantum dots are made into a third film by using a spin coating technique.

6. The quantum dot transfer method according to claim 1, characterized in that: Also includes: Pre-patterning the transfer head using photolithography technology; The method of printing the transferred substrate by using a transfer head dipped with the first film and the second film comprises: The first film and the second film are printed onto the substrate based on a transfer head subjected to a patterning process, and an RGB arrangement is formed on the substrate.

7. The quantum dot transfer method according to claim 1, characterized in that: The material of the transfer head is polydimethylsiloxane.

8. A QLED preparation method, characterized in that: The invention comprises the quantum dot transfer method as described in any one of claims 1 to 7.

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