Quantum dot film and preparation method thereof, optoelectronic device and preparation method thereof

Abstract

The application provides a quantum dot film and a preparation method thereof, and a photoelectric device and a preparation method thereof. The quantum dot film is prepared by dispersing ionizable ligand-modified quantum dots in a polar solvent to form an electrostatically stable quantum dot solution, and then introducing a conductive substrate into the quantum dot solution and applying a voltage between the conductive substrate and the quantum dot solution. After power-on, the ionic ligand carried by the quantum dots is ionized, and the charged quantum dots are gathered into a film towards the electrode with opposite polarity. The performance of the film, such as the thickness, surface roughness and refractive index of the film, can be regulated by adjusting the strength of the electric field, the power-on time and the concentration of the quantum dots in the quantum dot solution, so that the performance of the film is regulated during the film forming stage. The film prepared by the preparation method has good compactness and variable thickness, roughness and refractive index.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor materials and display, and particularly relates to a quantum dot film and a preparation method thereof, and a photoelectric device and a preparation method thereof. BACKGROUND

[0002] Quantum dot light emitting diode (QLED) has advantages of adjustable emission spectrum, narrow light emission spectrum, high light emission efficiency, etc., and is a selection of next generation flat panel light emitting technology that attracts attention. At present, QLED has better competitive advantages in color purity, color saturation and production cost compared with OLED and traditional LCD.

[0003] At present, in the existing QLED device, the light emitting layer is usually a quantum dot film formed by inorganic quantum dot light emitting material. On the one hand, because the interface gap penetration between the film layers is prone to occur between the quantum dot light emitting layer and the electron transport layer, and the film layer uniformity is poor when the film is formed as a substrate, the flatness is poor, which causes the quenching of excitons and reduces the performance of the device; on the other hand, the quantum dot light emitting layer is usually prepared by a solution method in the prior art, and the refractive index of the quantum dot film is relatively fixed under the condition that the concentration of the quantum dot solution is certain in the solution method, so the refractive index of the quantum dot light emitting layer cannot be effectively controlled in the film forming process, thereby it is difficult to achieve a better light extraction effect. SUMMARY

[0004] Therefore, the present application provides a preparation method of a quantum dot film, which can control the surface roughness and refractive index of the quantum dot film, and can be used to prepare a light emitting layer of a photoelectric device to improve the performance of the device.

[0005] The present application is implemented in the following manner, a preparation method of a quantum dot film is provided,

[0006] A preparation method of a quantum dot film, comprising the following steps:

[0007] providing a conductive substrate,

[0008] providing a quantum dot solution,

[0009] covering the conductive surface of the conductive substrate with the quantum dot solution, applying a voltage between the conductive substrate and the quantum dot solution, depositing quantum dots in the quantum dot solution on the surface of the conductive substrate to form the quantum dot film;

[0010] The quantum dot solution comprises quantum dots with ligands and a polar solvent, and the ligands comprise ionic ligands.

[0011] In some embodiments, the step of applying a voltage between the conductive substrate and the quantum dot solution comprises:

[0012] connecting one end of the power electrode with the conductive substrate, and connecting the other end of the power electrode with a counter electrode, and immersing the counter electrode into the quantum dot solution;

[0013] The power electrode includes a positive electrode and a negative electrode, and the power electrode connected with the conductive substrate has an electrical property opposite to that of the ionic ligand.

[0014] In some embodiments, the ionic organic ligand is an anionic ligand, and the step of applying a voltage between the conductive substrate and the quantum dot solution includes:

[0015] The positive electrode of the power electrode is connected with the conductive substrate, and the negative electrode of the power electrode is connected with the counter electrode; or

[0016] The ionic ligand is a cationic ligand, and the step of applying a voltage between the conductive substrate and the quantum dot solution includes:

[0017] The negative electrode of the power electrode is connected with the conductive substrate, and the positive electrode of the power electrode is connected with the counter electrode.

[0018] In some embodiments, the ionic ligand is selected from at least one of a carboxylate anionic ligand, a phosphonate anionic ligand, a carbamate anionic ligand, a polyethylene glycol amine cationic ligand, and an oleylamine cationic ligand; and / or

[0019] The polar solvent is selected from at least one of chloroform, a mixture of chloroform and acetonitrile, and propylene glycol methyl ether acetate; and / or

[0020] The quantum dot is a core-shell quantum dot light emitting material, and the core or shell of the core-shell quantum dot is selected from one or more of a II-VI compound, a III-V compound, a II-V compound, a III-VI compound, a IV-VI compound, a I-III-VI compound, a II-IV-VI compound, or a IV element.

[0021] In some embodiments, the concentration of the quantum dot with ligands in the quantum dot solution is 5 mg / ml to 50 mg / ml; and / or

[0022] The voltage is less than or equal to 6 V; and / or

[0023] In the step of applying a voltage between the conductive substrate and the quantum dot solution, the time for applying the voltage is a first preset time, and the first preset time is less than or equal to 30 s.

[0024] In some embodiments, the voltage is greater than or equal to 0 V and less than or equal to 3.5 V.

[0025] In some embodiments, the preparation method further includes: after applying a voltage between the conductive substrate and the quantum dot solution, removing the conductive substrate from the quantum dot solution and continuing to apply the voltage; and / or

[0026] The quantum dot film was annealed at 80°C to 110°C for 10 to 30 minutes.

[0027] In some embodiments, removing the conductive substrate from the quantum dot solution and continuing to apply a voltage includes:

[0028] After the conductive substrate is removed from the quantum dot solution, a voltage is continued to be applied for a second preset time, wherein the second preset time is less than or equal to 30 seconds.

[0029] This application provides a quantum dot thin film, which is prepared using the preparation method described above.

[0030] In some embodiments, the thickness of the quantum dot film is 10 nm to 200 nm, the surface roughness is 0.5 nm to 4 nm, and / or the density of the quantum dot film is 2 g / cm³. 3 ~3g / cm 3 The refractive index of light with a wavelength of 630 nm in the quantum dot film is 1.7 to 3.

[0031] In some embodiments, the optoelectronic device includes a cathode, an anode, and a light-emitting layer disposed between the cathode and the anode, wherein the light-emitting layer includes a quantum dot thin film as described above.

[0032] In some embodiments, the cathode is selected from one or more of a metal electrode, a carbon electrode, and a composite electrode formed from doped or undoped metal oxide electrodes; wherein the material of the metal electrode is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the material of the carbon electrode is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the material of the doped or undoped metal oxide electrode is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; the material of the composite electrode is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2; and / or

[0033] The anode is selected from one or more of the following: metal electrode, carbon electrode, and composite electrode formed by doped or undoped metal oxide electrode; wherein, the material of the metal electrode is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the material of the carbon electrode is selected from at least one of graphite, carbon nanotube, graphene, and carbon fiber; the material of the doped or undoped metal oxide electrode is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; and the material of the composite electrode is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0034] In some embodiments, an electronic functional layer is further disposed between the cathode and the light-emitting layer, and / or a hole functional layer is further disposed between the anode and the light-emitting layer.

[0035] In some embodiments, the electronic functional layer is an electron transport layer, and the material of the electron transport layer is selected from at least one of ZnO, TiO2, CsF, LiF, CsCO3, and Alq3; and / or

[0036] The hole functional layer is a hole transport layer and / or a hole injection layer. The material of the hole transport layer is selected from poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4 At least one of the following: 4',4”-tris(carbazole-9-yl)triphenylamine (TCATA), 4,4'-di(9-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), doped graphene, undoped graphene, and C60;

[0037] The material of the hole injection layer is selected from at least one of poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethylethane (F4-TCNQ), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene (HATCN), copper polyester carbonate (CuPc), transition metal oxides, and transition metal chalcogenides.

[0038] This application provides a method for fabricating an optoelectronic device, comprising the following steps:

[0039] An electrode substrate is provided, wherein the electrode substrate is provided with an anode layer;

[0040] A quantum dot solution is provided, and the quantum dot solution covers at least one surface of the electrode substrate on the side where the anode layer is provided. A voltage is applied between the electrode substrate and the quantum dot solution to deposit quantum dots in the quantum dot solution on the surface of the electrode substrate on the side where the anode layer is provided, thereby forming a light-emitting layer.

[0041] A cathode layer is disposed on the surface of the light-emitting layer away from the anode layer; or...

[0042] An electrode substrate is provided, wherein the electrode substrate is provided with a cathode layer;

[0043] A quantum dot solution is provided, and the quantum dot solution covers at least one side surface of the electrode substrate on which the cathode layer is provided. A voltage is applied between the electrode substrate and the quantum dot solution to deposit quantum dots in the quantum dot solution on the side surface of the electrode substrate on which the cathode layer is provided, thereby forming a light-emitting layer.

[0044] An anode layer is disposed on the surface of the light-emitting layer away from the cathode layer;

[0045] The quantum dot solution comprises quantum dots with ligands and a polar solvent, wherein the ligands include ionic ligands.

[0046] In some embodiments, the preparation method further includes:

[0047] Before forming the light-emitting layer, a hole functional layer is provided on the side surface of the electrode substrate on which the anode layer is provided, and / or an electron functional layer is provided on the side surface of the light-emitting layer away from the anode layer after forming the light-emitting layer and before forming the cathode layer;

[0048] Alternatively, the preparation method may further include:

[0049] Before forming the light-emitting layer, an electronic functional layer is provided on the side surface of the electrode substrate on which the cathode layer is provided, and / or after forming the light-emitting layer and before providing the anode layer, a hole functional layer is provided on the side surface of the light-emitting layer away from the cathode layer.

[0050] This application provides a method for preparing quantum dot thin films. The method involves dispersing ionizable ligand-modified quantum dots in a polar solvent to form an electrostatically stable quantum dot solution. A conductive substrate is then immersed in the quantum dot solution, and a voltage is applied between the conductive substrate and the quantum dot solution. Upon energization, the ionic ligands on the quantum dots ionize, and the charged quantum dots aggregate towards an electrode with opposite polarity to form a film. The properties of the thin film, such as its thickness, surface roughness, and refractive index, can be controlled by adjusting the magnitude of the electric field, the energizing time, and the concentration of quantum dots in the solution. This allows for the control of the film's properties during the film formation stage. The thin films prepared by this method achieve good density and variable thickness, roughness, and refractive index, showing broad application prospects.

[0051] Furthermore, this preparation method can be used to prepare quantum dot light-emitting layers in optoelectronic devices such as quantum dot light-emitting diodes. It can improve the film density of the quantum dot light-emitting layer and conveniently control its thickness, surface roughness, and refractive index. It effectively improves the limitation of existing solution-based light-emitting layer preparation methods, which can only change the thickness after the concentration of the quantum dot solution is determined. This is of great significance for improving the performance and process efficiency of quantum dot light-emitting diodes. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a flowchart of a quantum dot thin film preparation method provided in an embodiment of this application. Figure 1 ;

[0054] Figure 2 This is a flowchart of a quantum dot thin film preparation method provided in an embodiment of this application. Figure 2 ;

[0055] Figure 3 This is a flowchart of a quantum dot thin film preparation method provided in an embodiment of this application. Figure 3 ;

[0056] Figure 4 This is a schematic diagram of the structure of an optoelectronic device provided in an embodiment of this application;

[0057] Figure 5 This is a flowchart of a method for fabricating an optoelectronic device according to an embodiment of this application;

[0058] Figure 6 This is a graph showing the change in quantum dot film thickness with energizing time under different voltages in Embodiment 1 of this application;

[0059] Figure 7 This is a graph showing the change in surface roughness of the quantum dot film as a function of voltage under constant energizing time in Embodiment 2 of this application.

[0060] Figure 8 This is a dot-shaped trend diagram showing the changes in the density and optical refractive index of the quantum dot film with voltage magnitude under constant energizing time in Embodiment 2 of this application. Detailed Implementation

[0061] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application. In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. In addition, in the description of this application, the term "including" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and conciseness and should not be construed as a hard limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values ​​within that range. For example, it should be assumed that the description of a range from 1 to 6 specifically discloses subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0062] Please see Figure 1 This application first provides a method for preparing quantum dot thin films, including the following steps:

[0063] S1 provides a conductive substrate.

[0064] S2 provides a quantum dot solution, wherein the quantum dot solution comprises quantum dots with ligands and a polar solvent, the ligands comprising ionic ligands;

[0065] S3 ensures that the quantum dot solution at least covers the conductive surface of the conductive substrate, and applies a voltage between the conductive substrate and the quantum dot solution to deposit quantum dots in the quantum dot solution onto the surface of the conductive substrate, forming the quantum dot film.

[0066] In step S1, the conductive substrate can be any conductive base or support known in the art. It is understood that because a voltage needs to be applied to deposit quantum dots from the quantum dot solution onto the substrate surface, the substrate should be conductive so that it exhibits polarity after being energized, thereby allowing quantum dots to be deposited on its surface under the influence of charge. The shape or material of the conductive substrate is not particularly limited, as long as it can serve as a support for the thin film and is conductive. In some embodiments, the conductive substrate is provided with an electrode material known in the art, such as one or more of metals, carbon materials, and metal oxides. The metals may be one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon materials may be one or more of graphite, carbon nanotubes, graphene, and carbon fibers; the metal oxides may be doped or undoped metal oxides, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, as well as composite electrodes in which a metal is sandwiched between doped or undoped transparent metal oxides. The composite electrodes include, but are not limited to, one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0067] In step S2, the quantum dot solution comprises quantum dots with ligands and a polar solvent. The ligands include ionic ligands that are ionized in the polar solvent to charge the quantum dots, allowing them to move under the influence of the charge upon application of a voltage. In some embodiments, the ionic ligands may be organic or inorganic ligands that are ionized in the polar solvent and can coordinate with the quantum dots. The ionic organic ligands may be selected from at least one of, for example, carboxylate anionic ligands, phosphonate anionic ligands, carbamate anionic ligands, polyethylene glycol amine cationic ligands, and oleylamine cationic ligands. The polar solvent may be selected from at least one of chloroform, a mixture of chloroform and acetonitrile, and propylene glycol methyl ether acetate.

[0068] In step S3, the conductive substrate can be immersed entirely or partially in the quantum dot solution, allowing the quantum dot solution to cover the surface of the conductive substrate; alternatively, the side of the conductive substrate with the electrode material can be brought into contact with the quantum dot solution, allowing the quantum dot solution to cover the side of the conductive substrate with the electrode material. Thus, when a voltage is applied, the quantum dots can move under the influence of the charge and deposit onto the side of the conductive substrate with the electrode material.

[0069] In some embodiments, applying a voltage between the conductive substrate and the quantum dot solution includes electrically connecting one end of a power electrode to the conductive substrate, connecting the other end of the power electrode to a counter electrode, and immersing the counter electrode in the quantum dot solution. Thus, when the power supply is connected, a voltage is applied between the conductive substrate and the quantum dot solution. It is understood that the power electrode includes a positive and a negative electrode. The electrical charge of the power electrode electrically connected to the conductive substrate is opposite to the charge of the ionic organic ligands in the quantum dot solution. This allows the quantum dots to move towards the conductive substrate with the opposite charge under the influence of the charge and deposit on the side of the conductive substrate where the electrode material is disposed, forming a quantum dot film. In some embodiments, the conductive substrate and the counter electrode are arranged opposite to each other, with the conductive side of the conductive substrate facing the counter electrode, which is more conducive to quantum dot deposition.

[0070] In some embodiments, the ionic ligand is an anionic ligand, in which case the positive terminal of the power supply electrode is electrically connected to the conductive substrate, and the negative terminal of the power supply electrode is electrically connected to the counter electrode. In other embodiments, the ionic ligand is a cationic ligand, in which case the negative terminal of the power supply electrode is electrically connected to the conductive substrate, and the positive terminal of the power supply electrode is electrically connected to the counter electrode.

[0071] Accordingly, see Figure 2 In some embodiments, the method for preparing the quantum dot thin film provided in this embodiment includes:

[0072] S11 provides a conductive substrate;

[0073] S21 provides a quantum dot solution comprising quantum dots with ligands and a polar solvent, wherein the ligands are anionic ligands;

[0074] S31 connects the positive terminal of the power supply electrode to the conductive substrate, connects the negative terminal of the power supply electrode to the counter electrode, immerses the counter electrode in the quantum dot solution, turns on the power supply to apply voltage between the conductive substrate and the quantum dot solution, so that the quantum dots in the quantum dot solution are deposited on the surface of the conductive substrate to form a quantum dot film.

[0075] See Figure 3 In other embodiments, the method for preparing the quantum dot thin film provided in this embodiment includes:

[0076] S12 provides a conductive substrate;

[0077] S22 provides a quantum dot solution comprising quantum dots with ligands and a polar solvent, wherein the organic ligands are cationic ligands;

[0078] S32 connects the negative terminal of the power supply electrode to the conductive substrate, connects the positive terminal of the power supply electrode to the counter electrode, immerses the counter electrode in the quantum dot solution, turns on the power supply to apply voltage between the conductive substrate and the quantum dot solution, so that the quantum dots in the quantum dot solution are deposited on the surface of the conductive substrate to form a quantum dot film.

[0079] In a quantum dot solution, the concentration of quantum dots with ligands is not particularly limited. Those skilled in the art will understand that different quantum dot concentrations achieve different film thicknesses and film density. In some embodiments, a suitable quantum dot concentration is 5 mg / ml to 50 mg / ml, for example, 10 mg / ml, 15 mg / ml, 20 mg / ml, 30 mg / ml, 40 mg / ml, or any other concentration within this range.

[0080] When applying voltage, the voltage applied between the conductive substrate and the quantum dot solution is less than or equal to 6V, and the voltage application time is a first preset time, which is less than or equal to 30s. It can be understood that this voltage is greater than 0V, and the first preset time is greater than 0s. When the quantum dot film preparation method of this embodiment is used to prepare the quantum dot light-emitting layer in a QLED, setting the voltage magnitude and energizing time as described above results in a lower surface roughness of the film, thus lower leakage current in the QLED, fewer interface defects after film formation, better interface performance with the electron transport layer, and more stable performance of the QLED device. Furthermore, when the voltage is less than or equal to 3.5V, the refractive index of the quantum dot film can be lowered, making the resulting quantum dot film more conducive to light extraction when applied to the quantum dot light-emitting layer.

[0081] In some embodiments, the applied voltage and the first preset energizing time can be determined based on the desired film properties such as film thickness and density. For example, the applied voltage can be 0V to 6V, preferably 0.5V to 3.5V, such as 3V, 2.5V, 2V, etc. If the applied voltage is too low, it will be difficult to obtain a dense quantum dot film with sufficient thickness; if the voltage is too high, the roughness of the quantum dot film will increase sharply, and the surface morphology will be destroyed. The first preset energizing time can be 3 to 30s, such as 10s, 15s, 20s, or 25s, etc. If the energizing time is too short, it will be difficult to deposit a film effectively; if the energizing time is too long, the film thickness will no longer increase, but the density will continue to increase.

[0082] In this embodiment of the application, the method for preparing quantum dot thin films further includes:

[0083] After applying a voltage between the conductive substrate and the quantum dot solution, the method further includes removing the conductive substrate from the quantum dot solution and continuing to apply the voltage. That is, after steps S3, S31, or S32, step S4 is included: removing the conductive substrate immersed in the quantum dot solution from the quantum dot solution and continuing to apply the voltage. Specifically, in the preparation method including step S31, the conductive substrate connected to the positive electrode of the power supply is removed from the quantum dot solution; in the preparation method including step S32, the conductive substrate connected to the negative electrode of the power supply is removed from the quantum dot solution. By removing the conductive substrate from the quantum dot solution, the quantum dots in the solution no longer continue to deposit onto the surface of the conductive substrate. Continuing to apply the voltage increases the adhesion of the quantum dots to the conductive substrate, increasing the density and thickness of the thin film.

[0084] In some embodiments, after removing the conductive substrate from the quantum dot solution in step S4, a voltage is continued to be applied for a second preset time, wherein the second preset time is less than or equal to 30 seconds. In some embodiments, a second preset time of less than or equal to 15 seconds can achieve good film density.

[0085] In some embodiments, the preparation method further includes annealing the quantum dot film at 80°C to 110°C for 10 min to 30 min after the voltage is applied.

[0086] In some embodiments, the counter electrode immersed in the quantum dot solution can be any type of electrode known in the art, such as a platinum electrode or a polymer electrode, as long as it can form a potential difference with the conductive substrate to apply an electric field between the conductive substrate and the quantum dot solution.

[0087] The quantum dot thin film preparation method provided in this application is applicable to the preparation of thin films of various types of quantum dots, and there is no particular limitation on the type of quantum dots. In some embodiments, the quantum dots are QD core-shell structure quantum dot luminescent materials, wherein the core-shell structure quantum dots are selected from one or more of group II-VI compounds, group III-V compounds, group II-V compounds, group III-VI compounds, group IV-VI compounds, group I-III-VI compounds, group II-IV-VI compounds, or group IV elements. As an example, the core material of the core-shell structured quantum dots may be, but is not limited to, at least one selected from CdSe, CdS, ZnSe, ZnS, CdTe, CdZnS, CdZnSe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdSeSTe, ZnSeSTe, CdZnSeSTe, InP, InAs, and InAsP, and the shell material may be, but is not limited to, at least one selected from CdS, ZnSe, ZnS, CdSeS, and ZnSeS.

[0088] Accordingly, another embodiment of this application provides a quantum dot film, wherein the material of the quantum dot film comprises quantum dots with ionic organic ligands, the thickness of the quantum dot film is 10 nm to 200 nm, and the surface roughness is 0.5 nm to 4 nm. Alternatively, a quantum dot film is provided, wherein the material of the quantum dot film comprises quantum dots with ionic ligands, and the density of the quantum dot film is 2 g / cm³. 3 ~3g / cm 3 The refractive index of light with a wavelength of 630 nm in the quantum dot film is 1.7 to 3.

[0089] In another embodiment, the quantum dot film has a thickness of 10 nm to 200 nm, a surface roughness of 0.5 nm to 4 nm, and a density of 2 g / cm³. 3 ~3g / cm 3 The refractive index of light with a wavelength of 630 nm in the quantum dot film is 1.7 to 3.

[0090] The quantum dot film provided in this embodiment can be prepared by the aforementioned method for preparing quantum dot films. All aspects of the aforementioned method for preparing quantum dot films are applicable to the preparation of the quantum dot film of this embodiment, and will not be repeated here.

[0091] This application also provides an optoelectronic device that uses a quantum dot thin film as the light-emitting layer, as described above. Specifically, see [link to relevant documentation]. Figure 4 The optoelectronic device includes a cathode 60, an anode 10, and a light-emitting layer 40 disposed between the cathode and the anode, wherein the light-emitting layer 40 includes a quantum dot film prepared by the aforementioned quantum dot film preparation method.

[0092] In some embodiments, the optoelectronic device further includes a hole functional layer disposed between the anode and the light-emitting layer, and an electron functional layer 50 disposed between the light-emitting layer 40 and the cathode 60. The hole functional layer may be a hole injection layer 20, a hole transport layer 30, or a combination of both. When the hole functional layer is a combination of the hole injection layer 20 and the hole transport layer 30, the hole injection layer 20 is closer to the anode 10, and the hole transport layer 30 is closer to the light-emitting layer 40. The electron functional layer 50 may be an electron transport layer.

[0093] The thickness of the light-emitting layer 40 can be within the range of thicknesses known in quantum dot optoelectronic devices, such as 10nm to 80nm, for example, 10nm, 20nm, 50nm, 80nm, etc.

[0094] The electronic functional layer 50 can be an electron transport layer, and the material of the electron transport layer can be various electron transport materials in the art. For example, it can be selected from, but is not limited to, one or more of inorganic nanocrystalline materials, doped inorganic nanocrystalline materials, and organic materials. In some embodiments, the electron transport material is selected from at least one of ZnO, TiO2, CsF, LiF, CsCO3, and Alq3.

[0095] The thickness of the electronic functional layer 50 can be, for example, 20nm to 60nm, such as 20nm, 30nm, 40nm, 50nm, 60nm, etc.

[0096] The anode 10 is made of a material known in the art for use as an anode, and the cathode 60 is made of a material known in the art for use as a cathode. The materials of the anode 10 and the cathode 60 can be one or more of metals, carbon materials, and metal oxides. For example, the metals can be one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon materials can be one or more of graphite, carbon nanotubes, graphene, and carbon fibers; the metal oxides can be doped or undoped metal oxides, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, as well as composite electrodes with metal sandwiched between doped or undoped transparent metal oxides. The composite electrodes include, but are not limited to, one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0097] The thickness of the anode 10 is a known anode thickness in the art, for example, it can be from 50nm to 120nm, such as 50nm, 60nm, 70nm, 80nm, 120nm, etc. The thickness of the cathode 60 is a known cathode thickness in the art, for example, it can be from 60nm to 150nm, such as 60nm, 80nm, 100nm, 120nm, 150nm, etc.

[0098] In some embodiments, the optoelectronic device may further include a hole transport layer 30, which is located between the anode 10 and the light-emitting layer 40. The material of the hole transport layer 30 may be selected from organic materials with hole transport capabilities, including but not limited to poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCATA), 4,4'-bis(9-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4 The hole transport layer 30 may be selected from one or more of the following: 1-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), doped graphene, undoped graphene, and C60. The material of the hole transport layer 30 may also be selected from inorganic materials with hole transport capabilities, including but not limited to one or more of doped or undoped NiO, WO3, MoO3, and CuO. The thickness of the hole transport layer 30 may be, for example, from 10 nm to 100 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 100 nm, etc.

[0099] The material of the hole injection layer 20 is a material known in the art for hole injection layers. The material of the hole injection layer 20 can be selected from materials with hole injection capability, including but not limited to poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethylethane (F4-TCNQ), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzphenanthrene (HATCN), copper polyester carbonate (CuPc), transition metal oxides, and transition metal chalcogenides. The thickness of the hole injection layer 20 can be the thickness of a conventional hole injection layer, for example, it can be from 20 nm to 80 nm, such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, etc.

[0100] It is understandable that, in addition to the functional layers mentioned above, optoelectronic devices can also have additional functional layers that are commonly used in optoelectronic devices to improve their performance, such as electron blocking layers, hole blocking layers, electron transport auxiliary layers, and interface modification layers. It is also understandable that the materials and thicknesses of the various layers in an optoelectronic device can be adjusted according to the device's light-emitting requirements.

[0101] In some embodiments of this application, the optoelectronic device is a quantum dot light-emitting diode (LED). The LED can be either a forward-mounted or inverted structure. In a forward-mounted LED, the substrate is connected to the anode 10, and the structure can be: glass substrate-anode 10-hole injection layer 20-hole transport layer 30-quantum dot light-emitting layer 40-electronic functional layer 50-cathode 60. In an inverted LED, the substrate is connected to the cathode 60, and the structure can be: glass substrate-cathode 60-electronic functional layer 50-quantum dot light-emitting layer 40-hole transport layer 30-hole injection layer 20-anode 10.

[0102] It is understood that at least one mentioned in this application includes one, two, or more than two.

[0103] This application also provides a method for fabricating an optoelectronic device. Based on the same inventive concept, the light-emitting layer of this method can be fabricated using the quantum dot thin film fabrication method described above.

[0104] In one embodiment, see Figure 5 The fabrication method of optoelectronic devices includes the following steps:

[0105] S10 provides an electrode substrate, which has an anode layer or a cathode layer.

[0106] S20 Prepares a light-emitting layer on one side of the electrode substrate where an anode layer or a cathode layer is provided: Provide a quantum dot solution, cover at least one side of the electrode substrate where an anode layer or a cathode layer is provided with the quantum dot solution, apply a voltage between the electrode substrate and the quantum dot solution, and deposit quantum dots in the quantum dot solution on the surface of the electrode substrate to form a light-emitting layer;

[0107] Quantum dot solutions consist of quantum dots with ligands and a polar solvent, including ionic ligands.

[0108] When used to fabricate an upright device including a hole functional layer, the electrode substrate includes an anode layer and a hole functional layer, the hole functional layer including a hole injection layer and / or a hole transport layer.

[0109] When used to fabricate an inverted device including an electron transport layer, the electrode substrate includes a cathode layer and an electron transport layer.

[0110] It is understood that the ionic ligand is an anionic ligand. In this case, the positive electrode of the power supply electrode is electrically connected to the electrode substrate, the negative electrode of the power supply electrode is connected to the counter electrode, and the counter electrode is immersed in the quantum dot solution. In other embodiments, the ionic ligand is a cationic organic ligand. The negative electrode of the power supply electrode is electrically connected to the electrode substrate, the positive electrode of the power supply electrode is connected to the counter electrode, and the counter electrode is immersed in the quantum dot solution.

[0111] In some embodiments, a method for fabricating an optoelectronic device, wherein the optoelectronic device is a positively positioned quantum dot light-emitting diode, includes the following steps:

[0112] S101 provides an electrode substrate with an anode.

[0113] S102 provides a quantum dot solution, which is then used to cover the side of the electrode substrate where the anode layer is located. A voltage is applied between the electrode substrate and the quantum dot solution, causing quantum dots in the quantum dot solution to deposit on the surface of the anode layer of the electrode substrate, forming a light-emitting layer.

[0114] S103 forms an electron transport layer by disposing an electron transport material on the side of the light-emitting layer away from the anode.

[0115] S104 has a cathode on the side of the electron transport layer away from the light-emitting layer.

[0116] It is understood that when the optoelectronic device includes a hole-functional layer such as a hole injection layer and / or a hole transport layer, between steps S101 and S102, the method further includes first setting a hole injection layer or a hole transport layer 30 on the anode, or sequentially setting a hole injection layer 20 and a hole transport layer 30, to obtain an electrode substrate with a hole-functional layer. Then, a quantum dot solution is applied to the side of the electrode substrate with the hole-functional layer, and a voltage is applied between the electrode substrate and the quantum dot solution to deposit quantum dots from the quantum dot solution onto the surface of the hole-functional layer. For example, an electrode substrate with an anode and hole-functional layer already set can be immersed in a quantum dot solution, and a voltage can be applied between the electrode substrate and the quantum dot solution.

[0117] In some embodiments, step S102 includes: providing a quantum dot solution, immersing an electrode substrate having an anode layer and a hole injection layer in the quantum dot solution, electrically connecting one end of a power electrode to the electrode substrate, connecting the other end of the power electrode to a counter electrode, immersing the counter electrode in the quantum dot solution, turning on the power supply, and applying a voltage between the electrode substrate and the quantum dot solution.

[0118] This application provides another method for fabricating an optoelectronic device, which is an inverted quantum dot light-emitting diode, including the following steps:

[0119] In some embodiments, a method for fabricating an optoelectronic device, wherein the optoelectronic device is a positively positioned quantum dot light-emitting diode, includes the following steps:

[0120] S201 provides an electrode substrate with a cathode.

[0121] S202 forms an electron transport layer by disposing an electron transport material on the side of the cathode away from the substrate.

[0122] S203 provides a quantum dot solution, which is then used to cover the side of the electrode substrate where the electron transport layer is located. A voltage is applied between the electrode substrate and the quantum dot solution, causing quantum dots in the quantum dot solution to deposit on the surface of the electron transport layer, forming a light-emitting layer.

[0123] S204 has an anode on the side of the light-emitting layer away from the electron transport layer.

[0124] It is understood that when the optoelectronic device includes hole functional layers such as hole injection layer and / or hole transport layer, between steps S203 and S204, the device may further include setting a hole injection layer or hole transport layer 30 on the light-emitting layer, or setting a hole transport layer 30 and a hole injection layer 20 in sequence.

[0125] In some embodiments, step S203 includes: providing a quantum dot solution; immersing an electrode substrate having a cathode layer and an electron transport layer in the quantum dot solution; electrically connecting one end of a power electrode to the electrode substrate; connecting the other end of the power electrode to a counter electrode; immersing the counter electrode in the quantum dot solution; turning on the power supply; and applying a voltage between the electrode substrate and the quantum dot solution. At this time, the electrode substrate includes a cathode layer and an electron transport layer.

[0126] In the fabrication methods of optoelectronic devices, the method for preparing the light-emitting layer can be the aforementioned method for preparing quantum dot thin films, and the electrode substrate is equivalent to the conductive substrate in the quantum dot thin film preparation method. It is understood that, in the fabrication methods of optoelectronic devices, depending on whether the device is upright or inverted, a substrate with the anode or cathode of the optoelectronic device, or a substrate with a hole functional layer (e.g., a hole injection layer and / or a hole transport layer) or an electron functional layer (e.g., an electron transport layer), is used as the substrate for depositing the quantum dot light-emitting layer. The content of the aforementioned quantum dot thin film preparation methods is applicable to the fabrication methods of optoelectronic devices and will not be repeated here.

[0127] The materials of the cathode, anode, light-emitting layer, electron transport layer or other functional layers involved in the preparation method of the embodiments of this application are as described above, and will not be repeated here.

[0128] It is understood that when the optoelectronic device also includes other functional layers such as an electron blocking layer, a hole blocking layer, an electron injection layer, a hole injection layer, and / or an interface modification layer, the fabrication method of the optoelectronic device may further include the step of forming each of the functional layers.

[0129] It should be noted that the anode, hole injection layer, hole transport layer, electron transport layer, cathode, and other functional layers in the embodiments of this application can all be prepared using techniques known in the art, including but not limited to solution methods and deposition methods. Solution methods include, but are not limited to, spin coating, coating, inkjet printing, blade coating, dip-coating, immersion, spraying, roller coating, or casting. Deposition methods include chemical methods and physical methods. Chemical methods include, but are not limited to, chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, or co-precipitation. Physical methods include, but are not limited to, thermal evaporation deposition, electron beam evaporation deposition, magnetron sputtering, multi-arc ion plating, physical vapor deposition, atomic layer deposition, or pulsed laser deposition. When using solution methods to prepare the anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, cathode, and other functional layers, a drying process must be added.

[0130] This application also provides a display device, including the optoelectronic device provided in this application. The display device can be any electronic product with display function, including but not limited to televisions, mobile phones, monitors, etc.

[0131] The technical solutions and effects of this application will be described in detail below through specific embodiments, comparative examples and experimental examples. The following embodiments are only some embodiments of this application and are not intended to limit this application.

[0132] Example 1

[0133] This embodiment provides a method for preparing quantum dot films and the prepared quantum dot films.

[0134] A solution containing CdSe@ZnS green quantum dots was prepared using propylene glycol methyl ether acetate as the solvent. The quantum dot shells were coated with polyethylene glycol carboxylic acid ligands, and the concentration of quantum dots in the solution was 10 mg / ml.

[0135] A conductive substrate was immersed in the solution containing quantum dots. The conductive substrate was connected to the positive terminal of a DC regulated power supply, and the negative terminal of the DC regulated power supply was connected to a platinum electrode. The platinum electrode was immersed in the solution containing quantum dots, and energization was applied for a first preset time. Groups with voltages of 3V, 5V, and 10V were set, and the first preset energization time was set to the range of 0s to 80s for each group. The thickness of the obtained quantum dot film was measured, and the results are as follows. Figure 6 As shown.

[0136] according to Figure 6 It can be seen that, under specific quantum dot concentrations and energizing voltages, the thickness of the quantum dot film initially increases with energizing time. After 30 seconds, the thickness of the quantum dot film reaches a certain level and then stabilizes. At this point, further extending the energizing time leads to a continued increase in the density of the quantum dot film. It can also be seen that, at a specific quantum dot concentration, if the energizing time is fixed, the higher the voltage, the thicker the quantum dot film.

[0137] Example 2

[0138] This embodiment provides a method for preparing quantum dot films and the prepared quantum dot films.

[0139] The difference between this embodiment and Embodiment 1 is that the energizing time is set to 15 seconds, and multiple sets of parallel samples are prepared, each using a different energizing voltage within the range of 0V to 10V. The roughness of the prepared quantum dot film is measured using an atomic force microscope, and the results are as follows. Figure 7 As shown. The density of the prepared quantum dot film was measured using a gravimetric method (the mass of the film per unit volume characterizes the density of the film), and the refractive index of the prepared film at a wavelength of 630 nm was tested. The results are as follows. Figure 8 As shown.

[0140] according to Figure 7As shown, under the condition that the concentration of the quantum dot solution and the energizing time are constant, the surface roughness of the quantum dot film increases slowly with the increase of the applied voltage, and then reaches a stable state. When the voltage exceeds 7V, the surface roughness of the quantum dot film increases sharply. Therefore, it is more advantageous to control the energizing voltage within the range of less than or equal to 6V to obtain quantum dot films with smaller surface roughness.

[0141] according to Figure 8 It is known that the density and refractive index of quantum dot films gradually increase with increasing voltage, but the rate of change in density and refractive index slows down after the voltage reaches 6V. Therefore, controlling the voltage to be less than or equal to 6V is more advantageous for obtaining dense quantum dot films. Furthermore, considering that the low refractive index of the quantum dot emitting layer is more conducive to light extraction in quantum dot diode light-emitting devices, when using this method to prepare the quantum dot emitting layer, controlling the voltage to be less than or equal to 3.5V can yield quantum dot films with excellent density, film thickness, and refractive index, suitable for quantum dot light-emitting devices.

[0142] Example 3

[0143] This embodiment provides an optoelectronic device and its fabrication method.

[0144] An ITO anode was prepared on a glass substrate, and a hole injection layer was prepared on the ITO anode: the water-soluble conductive polymer PEDOT was spin-coated onto the anode, dried to form a film, and then annealed at 150°C for 20 min to a thickness of 45 nm.

[0145] A hole transport layer was prepared on the hole injection layer: TFB ink was spin-coated onto the hole injection layer, dried under vacuum to form a film, and then annealed at 230°C for 30 min to a thickness of 25 nm.

[0146] Fabrication of a quantum dot luminescent layer on a hole transport layer:

[0147] A quantum dot solution was prepared using CdSe@ZnS green quantum dots, with a shell coated with polyethylene glycol carboxylic acid ligands and propylene glycol methyl ether acetate as the polar solvent. The concentration of quantum dots in the solution was 20 mg / ml.

[0148] like Figure 4As shown, a substrate with a hole transport layer was connected to the positive terminal of a DC regulated power supply, and a platinum electrode was connected to the negative terminal of the DC regulated power supply. The substrate was then immersed in a container containing the aforementioned quantum dot solution, with the side of the substrate with the hole transport layer facing the platinum electrode. A voltage of 3V was applied for 10 seconds. After 10 seconds, the substrate was removed, and the voltage was applied for another 10 seconds. Then, the power supply was disconnected. Subsequently, the substrate was immersed in a container containing pure propylene glycol methyl ether acetate solvent for 20 seconds to remove any unadsorbed quantum dots. The substrate was then annealed at 80°C for 15 minutes to obtain a quantum dot light-emitting layer with a thickness of 20 nm.

[0149] An electron transport layer was prepared on the quantum dot luminescent layer: ZnO ink was spin-coated onto the quantum dot luminescent layer, dried under vacuum to form a film, and then annealed at 120°C for 15 min to a thickness of 40 nm.

[0150] A cathode was fabricated on the electron transport layer: Al was deposited on the electron transport layer by vapor deposition, with a thickness of 150 nm.

[0151] The entire process of packaging and fabricating the device is carried out in a nitrogen glove box.

[0152] In this embodiment, the surface roughness of the quantum dot light-emitting layer was measured to be 1.65 nm, and the refractive index of light with a wavelength of 630 nm in the quantum dot light-emitting layer was 1.782.

[0153] Example 4

[0154] This embodiment provides an optoelectronic device and its fabrication method.

[0155] This embodiment is prepared according to Example 3. The only difference from Example 3 is that the voltage is changed to 2.5V, the voltage is applied for 15s, the substrate is removed after 15s, and the voltage is applied for another 10s. The thickness of the quantum dot light-emitting layer is 20nm.

[0156] In this embodiment, the surface roughness of the quantum dot light-emitting layer was measured to be 1.53 nm, and the refractive index of light with a wavelength of 630 nm in the quantum dot light-emitting layer was 1.746.

[0157] Example 5

[0158] This embodiment provides an optoelectronic device and its fabrication method.

[0159] This embodiment is prepared according to Example 3, except that the quantum dot surface is coated with polyethylene glycolamine ligand, the polar solvent is ethanol, the negative terminal of the power supply is connected to the substrate, the positive terminal of the power supply is connected to the platinum electrode, the voltage is changed to 2.5V, the power is applied for 15s, the substrate is removed after 15s, and the voltage is applied for another 10s. The thickness of the quantum dot light-emitting layer is 20nm.

[0160] In this embodiment, the surface roughness of the quantum dot light-emitting layer was measured to be 1.48 nm, and the refractive index of light with a wavelength of 630 nm in the quantum dot light-emitting layer was 1.724.

[0161] Example 6

[0162] This embodiment provides an optoelectronic device and its fabrication method.

[0163] This embodiment is prepared according to Example 3. The only difference from Example 3 is that the voltage is changed to 3.5V, the voltage is applied for 8s, the conductive substrate is removed after 8s, and the voltage is applied for another 10s. The thickness of the quantum dot light-emitting layer is 20nm.

[0164] In this embodiment, the surface roughness of the quantum dot light-emitting layer was measured to be 1.72 nm, and the refractive index of light with a wavelength of 630 nm in the quantum dot light-emitting layer was 1.805.

[0165] Example 7

[0166] This embodiment provides an optoelectronic device and its fabrication method.

[0167] This embodiment is prepared according to Example 3. The only difference from Example 3 is that the voltage is changed to 5V, the voltage is applied for 6s, the platinum electrode is removed after 6s, and the voltage is applied for another 10s. The thickness of the quantum dot light-emitting layer is 20nm.

[0168] In this embodiment, the surface roughness of the quantum dot light-emitting layer was measured to be 2.2 nm, and the refractive index of light with a wavelength of 630 nm in the quantum dot light-emitting layer was 1.834.

[0169] Example 8

[0170] This embodiment provides an optoelectronic device and its fabrication method.

[0171] This embodiment is prepared according to Example 3. The only difference from Example 3 is that after the conductive substrate is removed, no further power is applied, and the thickness of the quantum dot light-emitting layer is 15 nm.

[0172] In this embodiment, the surface roughness of the quantum dot light-emitting layer was measured to be 1.68 nm, and the refractive index of light with a wavelength of 630 nm in the quantum dot light-emitting layer was 1.764.

[0173] Comparative Example 1

[0174] This comparative example provides an optoelectronic device and its fabrication method. Compared to Example 3, the only difference in Comparative Example 1 is that the ligand is a neutral ligand of tri-n-octylphosphine oxide, the solvent is the nonpolar solvent n-octane, and the quantum dot solution is spin-coated onto the hole transport layer. In this example, the surface roughness of the quantum dot emitting layer was measured to be 1.72 nm, and the refractive index of light with a wavelength of 630 nm in the quantum dot emitting layer was 1.875.

[0175] The QLEDs in Examples 3-5 and Comparative Example 1 were tested for external quantum dot efficiency (EQE), current efficiency, and lifetime T80@1000 nit. EQE and current efficiency were measured using an IVL EQE optical testing instrument. T80@1000 nit refers to the lifetime at which the initial brightness decays to 80% at 1000 nits. The driving current for both lifetime T80@1000 knit and EQE testing was 2 mA. The test results are shown in Table 1.

[0176] Table 1

[0177]

[0178] According to the test results of Examples 3 to 8 and Comparative Example 1, when the quantum dot light-emitting layer in the QLED is prepared using the method provided in the embodiments of this application, the surface roughness and refractive index of the quantum dot light-emitting layer are significantly lower than those prepared by the method of Comparative Example 1. Examples 3 to 8 use a quantum dot solution system with ionic ligands and a polar solvent. This allows the ionic ligands to ionize and become charged in the polar solvent. An electric field is applied between the substrate and the quantum dot solution, causing the charged quantum dots in the solution to move towards the substrate and deposit on the substrate surface under the influence of the electric field, significantly improving the surface morphology and refractive index of the quantum dot light-emitting layer. As shown in Table 1, the QLED devices prepared using the method of the embodiments of this application, specifically Examples 3 to 8, exhibit superior external quantum dot efficiency, current efficiency, and lifetime, all of which are better than or comparable to Comparative Example 1. Furthermore, comparing Examples 3 with Examples 6 and 7, it can be seen that QLED devices exhibit good performance within the voltage range of 0–6V, and show better external quantum dot efficiency, current efficiency, and lifetime when the voltage is below 3V. Compared to Example 8, Example 3, by continuing to apply power after removing the substrate, further improves the adhesion of the quantum dots, preventing them from being washed off due to weak adhesion, and increases the thickness and density of the light-emitting layer, thus resulting in higher external quantum dot efficiency, current efficiency, and lifetime. Conversely, in Example 8, while the external quantum efficiency and current efficiency are significantly improved compared to Comparative Example 1, the adhesion of the quantum dots on the substrate cannot be further strengthened after removing the conductive substrate, and some quantum dots are washed off during the rinsing process, leading to poor thickness and density of the light-emitting layer and affecting the device lifetime.

[0179] Therefore, the improved quantum dot light-emitting layer film formation performance and surface morphology provided in this application embodiment significantly improve the device performance, thereby improving both the device's luminous efficiency and lifetime.

[0180] Furthermore, the quantum dot thin film preparation method and the optoelectronic device preparation method provided in this application embodiment can conveniently control the requirements of film thickness, density, surface roughness and refractive index by adjusting the voltage magnitude and energizing time, which can meet the needs of different scenarios and has a wide range of applications.

[0181] The quantum dot thin films and their preparation methods, as well as the optoelectronic devices and their preparation methods provided in the embodiments of this application, have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a quantum dot thin film, characterized by, The method comprises the following steps: providing an electrically conductive substrate, providing a quantum dot solution, applying a voltage between the electrically conductive substrate and the quantum dot solution to cause quantum dots in the quantum dot solution to deposit on a surface of the electrically conductive substrate, thereby forming a quantum dot film on the surface of the electrically conductive substrate; wherein the quantum dot solution comprises quantum dots with ligands and a polar solvent, the ligands comprise ionic ligands, the ionic ligands are organic or inorganic ligands that can be ionized in the polar solvent and can be coordinated with the quantum dots, the ionic ligands are selected from at least one of carboxylate anion ligands, phosphonate anion ligands, polyethylene glycol amine cation ligands, and oleylamine cation ligands, and a refractive index of light with a wavelength of 630 nm in the quantum dot film is 1.7-1.

834.

2. The production method according to claim 1, characterized by, The step of applying a voltage between the electrically conductive substrate and the quantum dot solution comprises: electrically connecting one end of a power electrode to the electrically conductive substrate and electrically connecting the other end of the power electrode to a counter electrode, wherein the counter electrode is immersed in the quantum dot solution; wherein the power electrode comprises an anode and a cathode, and the power electrode electrically connected to the electrically conductive substrate has an electrical property opposite to that of the ionic ligands.

3. The method of claim 1, wherein: the ionic ligands are anionic ligands, and the step of applying a voltage between the electrically conductive substrate and the quantum dot solution comprises: electrically connecting the anode of a power electrode to the electrically conductive substrate and electrically connecting the cathode of the power electrode to the counter electrode; or the ionic ligands are cationic ligands, and the step of applying a voltage between the electrically conductive substrate and the quantum dot solution comprises: electrically connecting the cathode of a power electrode to the electrically conductive substrate and electrically connecting the anode of the power electrode to the counter electrode.

4. The method of any one of claims 1-3, wherein: the carboxylate anion ligands are selected from polyethylene glycol carboxylate ligands; the polyethylene glycol amine cation ligands are selected from polyethylene glycol amine ligands; the polar solvent is selected from at least one of chloroform, a mixture of chloroform and acetonitrile, and propylene glycol methyl ether acetate; the quantum dots are core-shell quantum dot light emitting materials, wherein the core or shell of the quantum dots is selected from one or more of group II-VI compounds, group III-V compounds, group II-V compounds, group III-VI compounds, group IV-VI compounds, group I-III-VI compounds, group II-IV-VI compounds, or group IV elemental substances.

5. The method of any one of claims 1-3, wherein the method further comprises, the concentration of the quantum dots with ligands in the quantum dot solution is 5-50 mg / ml; and / or the voltage is less than or equal to 6 V; and / or in the step of applying a voltage between the electrically conductive substrate and the quantum dot solution, the voltage is applied for a first preset time, and the first preset time is less than or equal to 30 s.

6. The production method according to claim 5, characterized by, the voltage is greater than 0 V and less than or equal to 3.5 V.

7. The preparation method according to claim 2, characterized in that, the method further comprises, after the step of applying a voltage between the electrically conductive substrate and the quantum dot solution, continuing to apply the voltage after the electrically conductive substrate is removed from the quantum dot solution; and / or The quantum dot film is annealed at 80-110°C for 10-30 minutes.

8. The production method according to claim 7, characterized by, The voltage is continuously applied after the conductive substrate is taken out of the quantum dot solution, and the voltage is applied for a second preset time, wherein the second preset time is less than or equal to 30 seconds. The quantum dot film is prepared by the method according to any one of claims 1-8.

9. A quantum dot film, characterized in that, The photoelectric device comprises a cathode, an anode, and a light-emitting layer disposed between the cathode and the anode, wherein the light-emitting layer comprises the quantum dot film prepared by the method according to any one of claims 1-8, or the light-emitting layer comprises the quantum dot film according to any one of claims 9 or 10.

10. The quantum dot film of claim 9, wherein, The quantum dot film has a thickness of 10 nm to 200 nm, a surface roughness of 0.5 nm to 4 nm, and / or a density of 2 g / cm 3 ~3 g / cm 3 .

11. An optoelectronic device, characterized in that The cathode is selected from one or more of a metal electrode, a carbon electrode, and a doped or undoped metal oxide electrode; wherein the material of the metal electrode is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the material of the carbon electrode is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the material of the doped or undoped metal oxide electrode is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; and the material of the composite electrode is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

12. The optoelectronic device of claim 11, wherein, The anode is selected from one or more of a metal electrode, a carbon electrode, and a doped or undoped metal oxide electrode; wherein the material of the metal electrode is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the material of the carbon electrode is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the material of the doped or undoped metal oxide electrode is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; and the material of the composite electrode is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2. An electron functional layer is further disposed between the cathode and the light-emitting layer, and / or a hole functional layer is further disposed between the anode and the light-emitting layer.

13. The optoelectronic device of claim 11, wherein, ​ 14. The optoelectronic device of claim 13, wherein, The electronic functional layer is an electron transport layer, and the material of the electron transport layer is selected from at least one of ZnO, TiO2, CsF, LiF, CsCO3, and Alq3; and / or The hole functional layer is a hole transport layer and / or a hole injection layer, and the material of the hole transport layer is selected from at least one of poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine), polyvinylcarbazole, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), 4,4',4''-tris(carbazol-9-yl)triphenylamine, 4,4'-bis(9-carbazol) biphenyl, N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, doped graphene, undoped graphene, and C60. The material of the hole injection layer is selected from at least one of poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, polymeric copper carbonate, transition metal oxides, and transition metal chalcogenides.

15. A method of fabricating an optoelectronic device, the method comprising: The preparation method comprises the following steps: providing an electrode substrate provided with an anode layer; providing a quantum dot solution, covering at least one side surface of the electrode substrate provided with the anode layer with the quantum dot solution, applying a voltage between the electrode substrate and the quantum dot solution, and depositing quantum dots in the quantum dot solution on the side surface of the electrode substrate provided with the anode layer to form a light-emitting layer; providing a cathode layer on a side surface of the light-emitting layer away from the anode layer; or providing an electrode substrate provided with a cathode layer; providing a quantum dot solution, covering at least one side surface of the electrode substrate provided with the cathode layer with the quantum dot solution, applying a voltage between the electrode substrate and the quantum dot solution, and depositing quantum dots in the quantum dot solution on the side surface of the electrode substrate provided with the cathode layer to form a light-emitting layer, wherein the light-emitting layer comprises a quantum dot film prepared by the preparation method according to any one of claims 1 to 8, or the light-emitting layer comprises the quantum dot film according to any one of claims 9 or 10; providing an anode layer on a side surface of the light-emitting layer away from the cathode layer. The quantum dot solution comprises quantum dots with ligands and a polar solvent, the ligands comprise ionic ligands, the ionic ligands are organic ligands or inorganic ligands that can be ionized in a polar solvent and can be coordinated with quantum dots, and the ionic ligands are selected from at least one of carboxylate anion ligands, phosphonate anion ligands, polyethylene glycol amine cation ligands, and oleylamine cation ligands. The preparation method further comprises:

16. The method of claim 15, wherein, ​ Before forming the light-emitting layer, a hole functional layer is arranged on the side surface of the electrode substrate provided with the anode layer, and / or after forming the light-emitting layer, an electron functional layer is arranged on the side surface of the light-emitting layer away from the anode layer before the cathode layer is arranged; Alternatively, the preparation method further comprises: Before forming the light-emitting layer, an electron functional layer is arranged on the side surface of the electrode substrate provided with the cathode layer, and / or after forming the light-emitting layer, a hole functional layer is arranged on the side surface of the light-emitting layer away from the cathode layer before the anode layer is arranged.

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