Quantum dot film layer with high compactness, preparation method thereof, and QLED light-emitting device and display device

Abstract

This application relates to the field of quantum dot light-emitting diodes (QLEDs), disclosing a highly dense quantum dot film, its fabrication method, and QLED light-emitting devices and display devices. This application introduces rigid steric materials such as fullerenes, which are smaller in volume than quantum dots and have a diameter of 0.2-2 nm, into the quantum dots to fill the gaps between them. Compared to conventional quantum dot films, the spin-coated quantum dot film produced by this method exhibits significantly improved morphology and better film density.

Description

Technical Field

[0001] This application relates to the field of quantum dot light-emitting diodes, and more particularly to a quantum dot film with high density, a method for preparing the same, and QLED light-emitting devices and display devices. Background Technology

[0002] All-solution-processed quantum dot light-emitting diodes (QLEDs) have great potential applications in future display and lighting fields. Currently, the hole transport layer and electron transport layer in QLEDs can be formed by non-solution processes such as evaporation or sputtering, but quantum dot materials are still mostly processed using solution methods.

[0003] In the quantum dot solution film deposition process, quantum dot materials are nanomaterials with a certain spatial volume. After film deposition, gaps between nanomaterials are inevitable. These gaps may lead to a deterioration of the film layer in subsequent devices, affecting the transport of charge carriers.

[0004] Current solutions include spin-coating multiple quantum dot films or increasing the thickness of the quantum dot film. However, these methods can only solve the pinhole defects in the quantum dot film and do not improve the gaps formed by the spatial structure of the quantum dot film itself. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a method for preparing a quantum dot film with high density, by introducing a three-dimensional rigid material of appropriate size to fill the gaps in the quantum dot film itself, thereby improving the density of the quantum dot film.

[0006] Another objective of this application is to provide a quantum dot film layer formed by quantum dots and a three-dimensional rigid material of suitable size, and a QLED light-emitting device and display device having the quantum dot film layer.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] In the first aspect of this application, a method for preparing a highly dense quantum dot film is provided, in which a three-dimensional rigid material with a diameter of 0.2-2 nm is mixed with a quantum dot solution and then co-formed into a film. Meanwhile, considering the carrier transport efficiency between quantum dots, the mobility of the three-dimensional rigid material in this application is (1×10⁻⁶). -2 )-(1×10 -5 )cm 2 / V / s.

[0009] Optionally, the stereo rigid material is one or more of fullerene, adamantane, and stereo metal-organic framework materials.

[0010] Optionally, the fullerene is a metallofullerene; further optionally, the fullerene or metallofullerene has 60-82 C atoms, for example, the fullerene or metallofullerene may have 60, 70, 79, 80 or 82 C atoms.

[0011] Optionally, the metal fullerene is a metal fullerene containing rare earth elements; more preferably, the metal fullerene is a metal fullerene containing one or more rare earth elements selected from Gd, Dy, Yb, Y, and Sc, for example, the metal fullerene is selected from Gd@C 82 Yb@C 82 Dy@C 82 Sc3C2@C 80 Y2@C 79 N、DySc2N@C 80 One or more of them.

[0012] Optionally, the surface of the metallofullerene is modified with an amino acid or ethylenediamine (EDA); further optionally, the amino acid is alanine, such as β-alanine.

[0013] In a second aspect of this application, a quantum dot film is provided, comprising quantum dots and a three-dimensional rigid material with a diameter of 0.2-2 nm used in the aforementioned preparation method, wherein the three-dimensional rigid material fills the gaps between the quantum dots.

[0014] In a third aspect of this application, a QLED light-emitting device is provided, wherein the light-emitting layer has the aforementioned quantum dot film layer.

[0015] Optionally, the QLED light-emitting device further includes one or more components selected from the following: substrate, cathode, electron injection layer, electron transport layer, hole blocking layer, electron blocking layer, hole transport layer, hole injection layer, and anode.

[0016] In a fourth aspect of this application, a display device is provided, including the QLED light-emitting device described in this application.

[0017] The method disclosed in this application mixes fullerenes and other three-dimensional rigid materials of suitable diameter into quantum dots to fill the gaps between the quantum dots. After forming a film together, the morphology of the film is greatly improved and the film density is better. In contrast, conventional quantum dot films have large pores and defects, poor film uniformity and density, and large roughness. Attached Figure Description

[0018] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the following detailed description to explain this application, but do not constitute a limitation thereof.

[0019] Figure 1 The image shown is the AFM image of the quantum dot film without the addition of fullerene derivatives;

[0020] Figure 2 The image shown is the AFM image of a quantum dot film with added fullerene derivatives. Detailed Implementation

[0021] This application discloses a highly dense quantum dot film and its preparation method, as well as a QLED light-emitting device and display apparatus. Those skilled in the art can refer to the content of this application and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The methods and products described in this application have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate changes and combinations to the methods and products described herein without departing from the content, spirit, and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] It should be noted that, in this document, relational terms such as "first" and "second," "S1 and S2," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0023] Quantum dots, as nanomaterials, possess a certain spatial volume, inevitably resulting in gaps between nanomaterials after film formation. Even using current common methods—modifying quantum dots with organic ligands—the lack of rigidity after film formation means gaps still exist in the quantum dot film. Therefore, this application selects a stereolithographic rigid material of suitable size to form a film together with the quantum dot solution, which can largely fill the gaps in the film layer and improve its density. The stereolithographic rigid material here includes, but is not limited to, fullerenes, adamantane, and stereometallic organic frameworks.

[0024] In the first aspect of this application, the three-dimensional rigid material and the quantum dot solution are mixed and then coated together to form a film using a spin-coating method. The volume ratio between the two is determined based on the actual size of the quantum dots selected and the required migration rate after filling the three-dimensional rigid material. In some embodiments of this application, the volume ratio of quantum dots to three-dimensional rigid material is 1:1-5:1, and in some embodiments of this application, the volume ratio of quantum dots to three-dimensional rigid material is 1:1, 2:1, 3:1, 4:1, or 5:1.

[0025] In some embodiments of this application, the rigid stereomaterial is a fullerene. Fullerenes are the third allotrope of elemental carbon discovered. Any cage-like molecular cluster composed solely of carbon, existing in a spherical, elliptical, or tubular structure, can be called a fullerene, belonging to a large class of substances. Fullerenes are structurally similar to graphite, but unlike graphite which only has six-membered rings, fullerenes may also contain five-membered rings. Currently, only carbon cages with 60-82 carbon atoms have been found in nature, corresponding to fullerene diameters ranging from 0.2-2 nm; simultaneously, to obtain better mobility, for example (1×10⁻⁶... -2 )-(1×10 -5 )cm 2 / V / s, this application modifies the fullerene carbon cage surface by modifying it with different groups, such as modifying the fullerene carbon cage surface with amino acids or ethylenediamine.

[0026] Metallofullerenes possess the dual characteristics of having an embedded metal and an outer carbon cage. They can embed one or two metal atoms, and in some cases, three. Compared to fullerenes, metallofullerenes exhibit improved stability and chemical reactivity, making them more conducive to the formation of fullerene derivatives. Therefore, in some embodiments, the fullerene is selected as a metallofullerene, typically using the general formula M@C. n In this representation, M represents the metal atom within the cage, and C... nThe symbol represents a fullerene molecule (n is the number of carbon atoms), and @ indicates "sandwich," signifying that the metal atoms are inside the carbon cage. For example, rare earth elements are selected and encased within the fullerene carbon cage. The rare earth elements can be one or more of Gd, Dy, Yb, Y, and Sc. In addition, there are currently metal fullerenes based on this general formula that embed other elements and / or modify other elements. In some other embodiments of this invention, the metal fullerene can be Gd@C 82 Yb@C 82 Dy@C 82 Sc3C2@C 80 Y2@C 79 N、DySc2N@C 80 One or more of them.

[0027] The surface of metallofullerenes can also be chemically modified. In some embodiments of this application, based on the further requirements for mobility and solubility in alkanes, amino acids or ethylenediamine (EDA) are modified on the surface of metallofullerenes to obtain metallofullerene-based derivatives M@C. n -X, where M represents a rare earth element, which can be selected from one or more of Gd, Dy, Yb, Y, and Sc; n represents the number of C atoms in the fullerene, which can be any integer in the range of 60-82, for example, the number of C atoms can be 60, 70, 79, 80, or 82; X represents the modified β-alanine and ethylenediamine.

[0028] In other embodiments of this application, the metallofullerene derivative may be Gd@C 82 -Ala、Gd@C 82 -EDA、Dy@C 82 -Ala or Dy@C 82 -EDA.

[0029] The metallofullerene derivatives described in this application can be synthesized using existing processes. In some embodiments of this application, M@C 82 -Ala and M@C 82 - EDA is used as an example to illustrate the modification method;

[0030] In M@C 82 In the modification of Ala-type metal fullerene derivatives, metal fullerene M@C 82 The reaction was carried out with β-alanine under an alkaline environment (e.g., sodium hydroxide solution) with stirring and heating until the insoluble matter was completely dissolved and the solution turned yellow. The reaction was then stopped, cooled to room temperature, and ethanol was added to precipitate the precipitate. The precipitate dissolved in water and was dialyzed and filtered to obtain M@C. 82 -Ala;

[0031] In M@C 82In the modification of EDA-based metal fullerene derivatives, metal fullerene M@C 82 After stirring and reacting with EDA, the mixture was filtered to obtain a product containing M@C. 82 -EDA and unreacted EDA solution. Unreacted EDA was removed by rotary drying followed by dialysis with hydrochloric acid to form chloride.

[0032] In a second aspect of this application, the quantum dot film comprises quantum dots and a three-dimensional rigid material with a diameter of 0.2-2 nm used in the aforementioned method, wherein the three-dimensional rigid material fills the gaps between the quantum dots, or is a quantum dot film formed using the aforementioned method.

[0033] In a third aspect of this application, a QLED light-emitting device is provided, wherein the light-emitting layer has the aforementioned quantum dot film layer. In addition, it may, as needed, include one or more components selected from the following: a substrate layer, a cathode, an electron injection layer, an electron transport layer, a hole blocking layer, an electron blocking layer, a hole transport layer, a hole injection layer, and an anode.

[0034] In a QLED light-emitting device with an upright structure, its structure from bottom to top is generally a substrate, anode, hole injection layer, hole transport layer, quantum dot light-emitting layer, electron transport layer, and cathode;

[0035] In an inverted QLED light-emitting device, the structure, from bottom to top, generally consists of a substrate, a cathode, an electron transport layer, a quantum dot light-emitting layer, a hole transport layer, a hole injection layer, and an anode. The hole transport layer, electron transport layer, and hole injection layer can contain materials commonly used in existing light-emitting elements. Hole transport layers can include, for example, TPD, polyTPD, PVK, TFB, CBP, NPD, etc. Electron transport layers can include, for example, ZnO nanoparticles, MgZnO nanoparticles, etc. Hole injection layers can include, for example, PEDOT:PSS, MoO3, NiO, etc.

[0036] Unless otherwise specified, any of the layers in a QLED light-emitting device may be deposited by any suitable method. For organic layers, preferred methods include thermal evaporation, inkjet printing, organic vapor deposition (OVPD), and deposition via organic vapor jet printing (OVJP). Other suitable deposition methods include spin coating and other solution-based processes. Solution-based processes are preferably performed in a nitrogen or inert atmosphere. For other layers, preferred methods include thermal evaporation.

[0037] In a fourth aspect of this application, a display device is provided, including the QLED light-emitting device described in this application. The display device can be a flexible display device (also known as a flexible screen) or a rigid display device (i.e., a display device that cannot be bent), and there is no limitation herein. The display device can be a QLED display device, or any product or component with display function, such as a television, digital camera, mobile phone, or tablet computer, that includes QLED.

[0038] The following provides a further description of a highly dense quantum dot film, its preparation method, and a QLED light-emitting device and display device provided in this application.

[0039] Example 1: β-Alanine-modified metallofullerene

[0040] Solid fullerene M@C 82 (M is Gd or Dy, purity: 99%, Xiamen Funa New Material Technology Co., Ltd.) Grind in a tissue grinder under the following conditions: grinding time 30-90s, grinding power 40-100Hz, and grinding times 30-50 times.

[0041] Add 50-100 mg of the ground metal fullerene powder to a solution containing 14-30% NaOH. (aq) Add 50-100 mL of β-alanine (3.6-10 g) to a single-necked flask and heat to 80-100 °C with stirring. Stop the reaction when the black insoluble substance in the flask is completely dissolved and the solution turns yellow. Cool to room temperature, add a large amount of ethanol to precipitate the precipitate, centrifuge, and dissolve the precipitate in water. Place the precipitate in a dialysis bag and dialyze for three days. Filter the product through a 220 nm filter membrane and disperse the filtered nanomaterial (solution) in water for later use. The diameter of the metallofullerene derivative is about 1.2 nm.

[0042] Example 2: EDA-modified metallofullerene

[0043] Add 50 mL of EDA (analytical grade, Sinopharm reagent, density 0.9 mg / mL) to a 100 mL stoppered conical flask, and add 50 mg of solid fullerene M@C. 82 (M represents Gd or Dy, purity: 99%, Xiamen Funa New Material Technology Co., Ltd.) A magnetic stir bar was then added, and the mixture was stirred at room temperature for 24 hours. The reaction product was then filtered through a 200nm filter membrane. The resulting solution was a brownish-red color, primarily composed of unreacted ethylenediamine and M@C. 82 -EDA.

[0044] Add the solution obtained above to a 250 ml round-bottom flask, and then use a rotary evaporator to dry the filtrate completely by rotation. Add 1 mol / L hydrochloric acid to the round-bottom flask, shake to dissolve the solid, and obtain a clear brownish-red solution.

[0045] The resulting brownish-red clear solution was neutralized until it tested weakly acidic on pH paper (approximately pH 5) to ensure that excess ethylenediamine existed as chloride and could be fully removed during the dialysis step. The neutralized solution was then placed in a dialysis bag (cutoff molecular weight 3500) and dialyzed in ultrapure water until the conductivity of the ultrapure water was less than 1 μS / cm, indicating that the diameter of the metallofullerene derivative was approximately 1.5 nm.

[0046] Example 3: Effects of metal fullerene derivatives on quantum dot films

[0047] Following the preparation method of Example 1, a metallofullerene derivative Gd@C82-Ala with a diameter of 1.2 nm was prepared; Gd@C 82 - Ala was mixed with quantum dots in a volume ratio of 1:2 and a film was formed by spin coating. A control group was set up, namely the quantum dot film without the addition of metal fullerene derivatives. Except for the difference between adding metal fullerene derivatives, all other experimental conditions were kept the same for each group.

[0048] according to Figure 1 The results show that the AFM height coordinate of the quantum dot film without the metal fullerene derivative is 23.9 nm, and the film has large pores and defects, poor uniformity and compactness, and high roughness. In contrast, the AFM height coordinate of the quantum dot film with the metal fullerene derivative is 16.5 nm, which is lower than that of the film without the metal fullerene derivative. However, according to... Figure 2 The results show that the morphology of the film is greatly improved and the film density is better after incorporating materials such as metal fullerene derivatives of appropriate diameter into the quantum dots.

[0049] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a quantum dot film layer with high compactness, characterized in that, A stereorigid material with a diameter of 0.2-2nm is mixed with a quantum dot solution to form a film; the mobility of the stereorigid material is (1×10 -2 ) - (1×10 -5 ) cm 2 / V / s; the stereorigid material is one or more of fullerene, diamondoid and stereometal-organic framework material, and the stereorigid material at least includes fullerene, and the fullerene is metal fullerene.

2. The method of claim 1, wherein, The number of C atoms of the fullerene is 60-82.

3. The preparation method according to claim 1, characterized in that, The metal fullerene is a metal fullerene containing a rare earth element.

4. The preparation method according to claim 3, characterized in that, The metal fullerene is a metal fullerene containing one or more than two rare earth elements selected from Gd, Dy, Yb, Y, and Sc.

5. The preparation method according to claim 4, characterized in that, The metallofullerene is selected from one or more of Gd@C 82 , Yb@C 82 , Dy@C 82 , Sc3C2@C 80 , Y2@C 79 , N, DySc2N@C 80 and two or more thereof.

6. The method of any one of claims 1, 3-5, wherein the compound is prepared by the method of claim 2. The metal fullerene is surface-modified with an amino acid or ethylenediamine.

7. The preparation method according to claim 6, characterized in that, The amino acid is alanine.

8. A quantum dot film layer, characterized in that, The quantum dot and the stereorigid material with a diameter of 0.2-2 nm in the preparation method of any one of claims 1-7 are filled in the gap between the quantum dots.

9. A QLED light emitting device, characterized in that, The light-emitting layer has the quantum dot film layer of claim 8.

10. A display device, characterized by comprising: The QLED light-emitting device of claim 9.

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