Light-emitting device and preparation method thereof

Abstract

The invention provides a light-emitting device and a preparation method thereof. The quantum dot film in the light-emitting device comprises the first quantum dot and the second quantum dot, the crystal structures of the first quantum dot and the second quantum dot are different, injection imbalance of electrons and holes can be relieved or eliminated, non-light-emitting energy loss is reduced, the light-emitting efficiency of the QLED device is improved, and the service life of the QLED device is prolonged.

Description

Technical Field

[0001] This application relates to the field of quantum dot technology, and in particular to a light-emitting device and its fabrication method. Background Technology

[0002] QLEDs (Quantum Dot Light Emitting Diodes) have advantages such as high color saturation, wet fabrication capability, and high stability, which have attracted increasing attention to QLED research and led to their wide application in display, lighting, and smart wearable fields.

[0003] QLED devices typically include a cathode and an anode positioned opposite each other, and a quantum dot film located between the cathode and anode. The quantum dot film comprises quantum dots, which are semiconductor crystal particles with a particle size of nanometers. Quantum dots exhibit high luminous brightness and high luminous efficiency. Because their bandgap varies with particle size, quantum dots possess the characteristic of being able to control the emission wavelength. When used in display devices, quantum dots can achieve a wider color gamut and lower power consumption than traditional phosphor materials. However, existing quantum dot films suffer from an imbalance between electron and hole injection, resulting in lower luminous efficiency in QLED devices. Summary of the Invention

[0004] Based on this, this application provides a light-emitting device and a method for fabricating the same.

[0005] In a first aspect, this application provides a light-emitting device, including a first electrode and a second electrode disposed opposite to each other, and a quantum dot film disposed between the first electrode and the second electrode. The quantum dot film includes a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures.

[0006] Secondly, embodiments of this application provide a method for fabricating a light-emitting device, comprising:

[0007] A first electrode is provided, and a quantum dot film is prepared on the first electrode. The quantum dot film includes a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures, including a zincblende structure, a wurtzite structure, a NaCl-type structure, or a CsCl-type structure.

[0008] A second electrode is formed on the side of the quantum dot film opposite to the first electrode.

[0009] The light-emitting device provided in this application uses a quantum dot thin film that can alleviate or eliminate the imbalance between the injection of electrons and holes in the quantum dot thin film, reduce the non-light-emitting energy loss in the quantum dot thin film, and improve the luminous efficiency and lifespan of the QLED device. Attached Figure Description

[0010] 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.

[0011] Figure 1 This is a schematic diagram of a first structure of a quantum dot thin film provided in an embodiment of this application.

[0012] Figure 2 This is a schematic diagram of a second structure of a quantum dot thin film provided in an embodiment of this application.

[0013] Figure 3 This is a first flowchart of a method for preparing quantum dot thin films provided in an embodiment of this application.

[0014] Figure 4 This is a second flowchart illustrating a method for preparing quantum dot thin films according to an embodiment of this application.

[0015] Figure 5 This is a schematic diagram of the structure of the light-emitting device provided in the embodiments of this application.

[0016] Figure 6 A flowchart illustrating the fabrication method of the light-emitting device provided in this application embodiment. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. 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.

[0018] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0019] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both mean: a, b, c, a+b, a+c, b+c, or a+b+c, where a, b, and c can be single or multiple.

[0020] In this application, another layer is formed "on" a certain layer. The term "on" is a broad concept and can mean that the formed other layer is adjacent to a certain layer, or that there are other spacer structures between the other layer and the certain layer. For example, a second electrode is formed "on" the first charge carrier functional layer. The term "on" can mean that the formed second electrode is adjacent to the first charge carrier functional layer, or that there are other spacer structures between the second electrode and the first charge carrier functional layer, such as a light-emitting layer.

[0021] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges 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., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0022] Please see Figure 1 and Figure 2 This application provides a quantum dot film 40, which includes a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures.

[0023] For example, the thickness of the quantum dot film 40 is 10nm-80nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, etc.

[0024] For example, in a quantum dot film, the average particle size of the first quantum dot is 1nm-30nm (e.g., 1nm, 2nm, 5nm, 8nm, 10nm, 13nm, 15nm, 17nm, 20nm, 22nm, 25nm, 28nm, 30nm, etc.), and the average particle size of the second quantum dot is 1nm-30nm (e.g., 1nm, 2nm, 5nm, 8nm, 10nm, 13nm, 15nm, 17nm, 20nm, 22nm, 25nm, 28nm, 30nm, etc.).

[0025] For example, in the embodiments of this application, at least two include two or more, such as three, four, five, six, seven, eight, nine, ten, etc.

[0026] For example, the crystal structure includes a zincblende structure, a wurtzite structure, a NaCl-type structure, or a CsCl-type structure.

[0027] It is understandable that quantum dots with different crystal structures are generally synthesized through different synthetic methods. Common crystal structures for Zn and Cd quantum dots include the zincblende structure and the wurtzite structure. For example, the main component of blue quantum dots is CdZnSeS. By adjusting the elemental composition, changing the ligands used, and adjusting the reaction temperature, the growth process can be made to favor the zincblende structure or the wurtzite structure.

[0028] Please see Figure 1 The quantum dot film 40 is a single-layer film, in which a first quantum dot and a second quantum dot are distributed. The first quantum dot and the second quantum dot may have the same or different constituent elements.

[0029] It should be noted that when the compositions of any two quantum dots with different crystal structures in a monolayer thin film are different, the inconsistency in elemental composition leads to inconsistent intrinsic electron transport rates and potential barrier stratification, which may increase the hole transport rate of the quantum dots. At the same time, since the crystal structures of the quantum dots are also different, the electron transport rate of the quantum dots will be reduced. This can improve the problem of electron-hole imbalance caused by excessive electron injection in existing quantum dot thin films, which is conducive to achieving carrier balance in quantum dot thin films, reducing non-luminescent energy loss in quantum dot thin films, and thus improving the luminous efficiency of light-emitting devices.

[0030] Exemplarily, the monolayer film contains a first quantum dot and a second quantum dot, with a mass ratio of (0.8-1.2):(0.8-1.2), such as 1:1, 0.8:0.9, 0.8:1.0, 0.8:1.1, 0.8:1.2, 1:0.8, 1:0.9, 1:1.1, 1:1.2, 1.2:0.8, 1.2:0.9, 1.2:1.0, 1.2:1.1, etc. Exemplarily, the first crystal structure can be selected from one of the following: zincblende structure, wurtzite structure, NaCl-type structure, and CsCl-type structure; the second crystal structure can also be selected from one of the following: zincblende structure, wurtzite structure, NaCl-type structure, and CsCl-type structure.

[0031] In some embodiments, the monolayer film comprises zincblende quantum dots and wurtzite quantum dots, wherein the mass ratio of the zincblende quantum dots to the wurtzite quantum dots is (0.8-1.2):(0.8-1.2), for example 1:1, 0.8:0.9, 0.8:1.0, 0.8:1.1, 0.8:1.2, 1:0.8, 1:0.9, 1:1.1, 1:1.2, 1.2:0.8, 1.2:0.9, 1.2:1.0, 1.2:1.1, etc. Exemplarily, the materials of the zincblende quantum dots and the wurtzite quantum dots may be the same or different.

[0032] Please see Figure 1 When two or more quantum dots are distributed in a single-layer film, the crystal structures of any two quantum dots are different, and the ratio of the mass of any one quantum dot to the total mass of the quantum dots in the single-layer film is less than or equal to 1 / 2. For example, the ratio of the mass of any one quantum dot to the total mass of the quantum dots in the single-layer film can be 1 / 2, 1 / 3, 1 / 4, 1 / 5, 1 / 6, etc.

[0033] It should be noted that by limiting the proportion of any one type of quantum dot in the total number of quantum dots to less than or equal to 1 / 2, the probability of quantum dots with the same crystal structure appearing around any one type of quantum dot can be reduced. It is known that the electron transport efficiency between quantum dots with the same crystal structure is high, while the electron transport efficiency between quantum dots with different crystal structures is low. Therefore, the above setting can reduce the electron mobility of quantum dot films, thereby alleviating or eliminating the imbalance of electron and hole injection in quantum dot films and promoting carrier balance.

[0034] Please see Figure 2The quantum dot film 40 includes multiple unit film layers stacked together, wherein the crystal structures of the quantum dots in any two adjacent unit film layers are different. The multiple unit film layers include a first unit film layer 41 and a second unit film layer 42 stacked together, wherein the material of the first unit film layer 41 includes a first quantum dot, and the material of the second unit film layer 42 includes a second quantum dot.

[0035] In the embodiments of this application, "multiple" refers to two or more, such as three, four, five, six, seven, eight, nine, ten, etc.

[0036] For example, the quantum dots in each unit film have the same crystal structure.

[0037] For example, the crystal structure of the first quantum dot can be selected from one of the following: zincblende structure, wurtzite structure, NaCl-type structure, and CsCl-type structure; the crystal structure of the second quantum dot can be selected from one of the following: zincblende structure, wurtzite structure, NaCl-type structure, and CsCl-type structure.

[0038] It should be noted that, due to the different crystal structures of quantum dots in two adjacent unit layers, the electron transport efficiency between the two adjacent unit layers is relatively low. Therefore, the electron mobility of the quantum dot film composed of multiple unit layers is relatively low, which can alleviate or eliminate the imbalance between the injection of electrons and holes in the quantum dot film and promote carrier balance.

[0039] For example, quantum dots in two adjacent unit films can use different ligands so that the quantum dots in two adjacent unit films have different polarities.

[0040] For example, two adjacent unit films can be prepared using different solvents when using solution film formation method, in order to avoid the quantum dots in the lower unit film being washed away by the solvent in the upper unit film, resulting in uneven film formation.

[0041] For example, the thickness of the unit film can be 5nm to 30nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, etc.

[0042] For example, any two adjacent unit films have the same thickness, or the absolute value of the difference between the thicknesses of any two adjacent unit films is less than or equal to 4 nm, such as 0.1 nm, 0.5 nm, 2 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, etc.

[0043] For example, in a plurality of unit films, the quantum dots in any two unit films may have the same or different compositions.

[0044] For example, the quantum dot film 40 may include alternating layers of zincblende quantum dot films and wurtzite quantum dot films, wherein the number of zincblende quantum dot films and the number of wurtzite quantum dot films are at least one. At least one means one, two, or more, such as three, four, five, six, seven, eight, nine, ten, etc.

[0045] For example, the absolute value of the difference in the average particle size of quantum dots in any two adjacent unit films is less than or equal to 3 nm. In some embodiments, the absolute value of the difference in the average particle size of quantum dots in any two adjacent unit films is less than or equal to 3 nm, 2.5 nm, 2 nm, 1.5 nm, 1 nm, or 0.5 nm, or the average particle size of quantum dots in any two adjacent unit films is equal.

[0046] It should be noted that the reason for setting the absolute value of the difference in the average particle size of quantum dots in any two adjacent unit films to be less than or equal to 3 nm is that when the average particle size of quantum dots in adjacent unit films is greater than 3 nm, larger pores are easily formed between multiple quantum dots in the unit film with larger particle size. At this time, quantum dots in the unit film with smaller particle size are easily embedded in the pores, thus failing to achieve the layering effect.

[0047] Please see Figure 2 The quantum dot film 40 may further include a third unit film layer 43 and a fourth unit film layer 44. The third unit film layer 43 is disposed on the side of the second unit film layer 42 opposite to the first unit film layer 41, and the fourth unit film layer 44 is disposed on the side of the third unit film layer 43 opposite to the second unit film layer 42. The crystal structure of the quantum dots in the third unit film layer 43 is different from the second crystal structure, and the crystal structure of the quantum dots in the fourth unit film layer 44 is different from the crystal structure of the quantum dots in the third unit film layer 43. Exemplarily, the crystal structure of the quantum dots in the third unit film layer 43 may be the same as or different from the first crystal structure, and the crystal structure of the quantum dots in the fourth unit film layer 44 may be the same as or different from the second crystal structure.

[0048] Exemplarily, the first quantum dot and the second quantum dot each comprise at least one of a single-structure quantum dot and a core-shell structure quantum dot. The material of the single-structure quantum dot, the core material of the core-shell structure quantum dot, and the shell material of the core-shell structure quantum dot each comprise at least one of group II-VI compounds, group IV-VI compounds, group III-V compounds, and group I-III-VI compounds. The group II-VI compounds are selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, and Cd... At least one of the following group IV-VI compounds: STe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe, wherein the IV-VI compound is selected from SnS, SnSe, SnTe, PbS, At least one of PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe, wherein the III-V compound is selected from GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, and Al At least one of PAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb, wherein the group I-III-VI compound is selected from at least one of CuInS2, CuInSe2, CuInSeS, and AgInS2.

[0049] For example, the surface of the first quantum dot and / or the second quantum dot is connected to a ligand, the ligand including at least one of acid ligand, thiol ligand, amine ligand, phosphophosphine ligand, phospholipid, lecithin, and polyvinylpyridine, the acid ligand being at least one of decaic acid, undecenoic acid, tetradecanoic acid, oleic acid, and stearic acid, the thiol ligand being at least one of octaalkylthiol, dodecylthiol, and octadecylthiol, the amine ligand being at least one of oleylamine, octadecylamine, and octadecylamine, and the phosphophosphine ligand being at least one of trioctylphosphine, tributylphosphine, and trioctylphosphine oxychloride.

[0050] The quantum dot film provided in this application includes a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures. Since the electron transport efficiency between quantum dots with different crystal structures is lower than that between quantum dots with the same crystal structure, the quantum dot film of this application has a lower electron mobility, which can alleviate or eliminate the imbalance of electron and hole injection in the quantum dot film, promote carrier balance, reduce non-luminescent energy loss in the quantum dot film, and thus help improve the luminous efficiency and lifespan of QLED devices.

[0051] Please see Figure 3 This application provides a method for preparing quantum dot thin films, used to prepare... Figure 1 The quantum dot thin film shown can be prepared by methods including:

[0052] S110, providing a composite quantum dot solution, the composite quantum dot solution comprising quantum dot material and solvent, the quantum dot material comprising a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures.

[0053] For example, the concentration of the composite quantum dot solution can be from 10 mg / mL to 100 mg / mL, such as 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL, 60 mg / mL, 70 mg / mL, 80 mg / mL, 90 mg / mL, 100 mg / mL, etc. In some embodiments, the concentration of quantum dots in the composite quantum dot solution is from 20 mg / mL to 50 mg / mL.

[0054] For example, the solvent in the composite quantum dot solution includes at least one of n-hexane, n-octane, n-heptane, toluene, chlorobenzene, and water.

[0055] For example, the crystal structure includes a zincblende structure, a wurtzite structure, a NaCl-type structure, or a CsCl-type structure.

[0056] S120, deposit composite quantum dot solution to obtain quantum dot film.

[0057] For example, the deposition of the composite quantum dot solution to obtain a quantum dot film may include: depositing the composite quantum dot solution to obtain a wet film layer, annealing the wet film layer at an annealing temperature of 60℃~100℃ (e.g., 60℃, 70℃, 80℃, 90℃, 100℃, etc.) and an annealing time of 5 minutes~30 minutes (e.g., 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.) to obtain a quantum dot film.

[0058] It can be seen that, Figure 1 The quantum dot film prepared by the method shown is a monolayer film.

[0059] Please see Figure 4 At the same time, combined Figure 2 This application provides a method for preparing quantum dot thin films, used to prepare... Figure 2 The quantum dot thin film shown can be prepared by methods including:

[0060] S210, a first quantum dot solution is provided, the first quantum dot solution including a first quantum dot and a solvent, and the first quantum dot solution is deposited to obtain a first unit film layer 41.

[0061] For example, the concentration of the first quantum dot solution can be from 10 mg / mL to 100 mg / mL, such as 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL, 60 mg / mL, 70 mg / mL, 80 mg / mL, 90 mg / mL, 100 mg / mL, etc. In some embodiments, the concentration of quantum dots in the first quantum dot solution is from 20 mg / mL to 50 mg / mL.

[0062] For example, the solvent in the first quantum dot solution includes at least one of n-hexane, n-octane, n-heptane, toluene, chlorobenzene, and water.

[0063] For example, the first crystal structure may be selected from one of the following: zincblende structure, wurtzite structure, NaCl type structure, and CsCl type structure.

[0064] For example, the deposition of the first quantum dot solution to obtain the first unit film 41 may include: depositing the first quantum dot solution to obtain a first wet film layer, annealing the first wet film layer at an annealing temperature of 60℃~100℃ (e.g., 60℃, 70℃, 80℃, 90℃, 100℃, etc.) and an annealing time of 5 minutes~30 minutes (e.g., 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.) to obtain the first unit film 41.

[0065] S220, a second quantum dot solution is provided, the second quantum dot solution includes a second quantum dot and a solvent, the second quantum dot solution is deposited on the first unit film layer 41 to obtain the second unit film layer 42, forming a quantum dot thin film, wherein the crystal structures of the first quantum dot and the second quantum dot are different, and the quantum dot thin film includes the first unit film layer 41 and the second unit film layer 42 stacked together.

[0066] For example, the concentration of the second quantum dot solution can be from 10 mg / mL to 100 mg / mL, such as 10 mg / mL, 20 mg / mL, 30 mg / mL, 40 mg / mL, 50 mg / mL, 60 mg / mL, 70 mg / mL, 80 mg / mL, 90 mg / mL, 100 mg / mL, etc. In some embodiments, the concentration of quantum dots in the second quantum dot solution is from 20 mg / mL to 50 mg / mL.

[0067] For example, the solvent in the second quantum dot solution includes at least one of n-hexane, n-octane, n-heptane, toluene, chlorobenzene, and water.

[0068] For example, the second crystal structure can be selected from one of the following: zincblende structure, wurtzite structure, NaCl type structure, and CsCl type structure.

[0069] For example, the deposition of the second quantum dot solution to obtain the second unit film 42 may include: depositing the second quantum dot solution to obtain a second wet film layer, annealing the second wet film layer at an annealing temperature of 60℃~100℃ (e.g., 60℃, 70℃, 80℃, 90℃, 100℃, etc.) and an annealing time of 5 minutes~30 minutes (e.g., 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.) to obtain the second unit film 42.

[0070] It can be seen that, Figure 2 The quantum dot film prepared by the method shown comprises multiple unit film layers.

[0071] It is understood that after obtaining the second unit film 42, a third unit film 43 and a fourth unit film 44 can be prepared on the second unit film 42. The third unit film 43 is disposed on the side of the second unit film 42 away from the first unit film 41, and the fourth unit film 44 is disposed on the side of the third unit film 43 away from the second unit film 42. The crystal structure of the quantum dots in the third unit film 43 is different from the second crystal structure, and the crystal structure of the quantum dots in the fourth unit film 44 is different from the crystal structure of the quantum dots in the third unit film 43. For example, the crystal structure of the quantum dots in the third unit film 43 may be the same as or different from the first crystal structure, and the crystal structure of the quantum dots in the fourth unit film 44 may be the same as or different from the second crystal structure.

[0072] Please see Figure 5 This application also provides a light-emitting device 100, including a first electrode 10 and a second electrode 60 disposed opposite to each other, and a quantum dot film 40 disposed between the first electrode 10 and the second electrode 60. The quantum dot film 40 is a quantum dot film 40 prepared by the quantum dot film preparation method in any of the above embodiments or a quantum dot film 40 in any of the above embodiments.

[0073] Please see Figure 5 When the first electrode 10 is the anode and the second electrode 60 is the cathode, the light-emitting device 100 includes a first electrode 10, a hole functional layer, a quantum dot film 40, an electron functional layer, and a second electrode 60 stacked sequentially. The hole functional layer includes a hole injection layer 20 and a hole transport layer 30. The hole injection layer 20 is disposed on the side close to the first electrode 60. The electron functional layer includes an electron transport layer 50.

[0074] For example, the material of hole transport layer 30 may include 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine (α-NPD), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)biphenylamine) (Poly-TP D), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine (DNTPD), 4,4',4'-tris(N-carbazolyl)-triphenylamine (TCTA), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA), poly[(9,9'-dioctylfluorene-2,7-diyl)co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))] (TFB), poly(N-vinylcarbazole) (PVK) and its derivatives, N,N'-bis(1-naphthyl)-N, N'-Diphenyl-1,1'-Biphenyl-4-4'-Diamine (NPB), Poly(phenylenevinylene) (PPV), Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MOMO-PPV), 2,2',7,7'-Tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (spiro-omeTAD), 4,4'-cyclohexyldi[N,N-di(4-... [-methylphenyl)aniline] (TAPC), 1,3-bis(carbazole-9-yl)benzene (MCP), polyaniline, polypyrrole, poly(p-)phenylenevinylene, aromatic tertiary amine, polynuclear aromatic tertiary amine, 4,4'-bis(p-carbazole)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, polyspirofluorene and its derivatives, polythiophene (TPH) and its derivatives, at least one of the following.

[0075] Exemplarily, the material of the hole injection layer 20 may include at least one selected from poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), copper phthalocyanine (CuPc), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzphenanthrene (HAT-CN), polydioxyethyl thiophene (PEDOT), a MoO3-doped derivative of PEDOT:PSS (PEDOT:PSS-MoO3), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA), tetracyanoquinone dimethane (F4-TCNQ), transition metal oxides, and transition metal chalcogenides. Exemplarily, the transition metal oxide may include MoO3. x VO x WO x CrO x One or more of CuO. For example, metal chalcogenides may include one or more of MoS2, MoSe2, WS2, WSe2, and CuS.

[0076] For example, the material of the electron transport layer 50 may include at least one of a metal oxide, a doped metal oxide, a group II-VI semiconductor material, a group III-V semiconductor material, and a group I-III-VI semiconductor material. The metal oxide is selected from at least one of ZnO, BaO, TiO2, and SnO2. The metal oxide in the doped metal oxide is selected from at least one of ZnO, TiO2, and SnO2, and the doping element is selected from at least one of Al, Mg, Li, In, and Ga. The group II-VI semiconductor material is selected from at least one of ZnS, ZnSe, and CdS. The group III-V semiconductor material is selected from at least one of InP and GaP. The group I-III-VI semiconductor material is selected from at least one of CuInS and CuGaS.

[0077] In some embodiments, the electron transport layer 50 is made of ZMO (magnesium-doped zinc oxide), which refers to magnesium-doped zinc oxide obtained by adding Mg precursors (magnesium compounds such as magnesium acetate, magnesium chloride, and magnesium nitrate) during the synthesis of zinc oxide.

[0078] For example, the material of the electron transport layer 50 can be nanoparticles of various morphologies such as nanospheres, nanosheets, and nanorods, and the average particle size of the material of the electron transport layer 50 is 2nm to 15nm, such as 2nm, 5nm, 10nm, 12nm, 15nm, etc.

[0079] For example, the first electrode 10 and the second electrode 60 can each be independently selected from doped metal oxide electrodes, composite electrodes, graphene electrodes, carbon nanotube electrodes, elemental metal electrodes, or alloy electrodes. The material of the doped metal oxide electrode can be, but is not limited to, one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), aluminum-doped magnesium oxide (AMO), and cadmium-doped zinc oxide. The composite electrode is an electrode formed by stacking two or more layers of conductive materials, such as 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, Ca / Al, LiF / Ca, LiF / Al, BaF2 / Al, CsF / Al, CaCO3 / Al, BaF2 / Ca / Al, etc., where " / " indicates a stacked structure. For example, AZO / Ag / AZO represents a composite electrode that includes a sequentially stacked AZO layer, an Ag layer, and an AZO layer. The material of the elemental metal electrode may be one or more of the following: silver (Ag), magnesium (Mg), aluminum (Al), gold (Au), gallium (Ga), nickel (Ni), platinum (Pt), iridium (Ir), copper (Cu), molybdenum (Mo), calcium (Ca), and barium (Ba). The alloy electrode may include, but is not limited to, Au:Mg alloy electrode or Ag:Mg alloy electrode.

[0080] In some embodiments, the first electrode is an anode, which can be an electrode with a relatively high work function, such as one or more of a doped metal oxide electrode, a metal element electrode with a relatively high work function, and a carbon nanotube electrode, including but not limited to the following: the metal element electrode with a relatively high work function can be made of materials such as Ni, Pt, Au, Ag, or Ir.

[0081] In some embodiments, the second electrode is a cathode, which can be an electrode with a relatively low work function, such as including but not limited to a metal element electrode with a relatively low work function, a composite electrode with a relatively low work function, and an alloy electrode with a relatively low work function; the material of the metal element electrode with a relatively low work function can be Ca, Ba, Al, Mg, etc.; the structure of the composite electrode with a relatively low work function can be Ca / Al, LiF / Ca, LiF / Al, BaF2 / Al, CsF / Al, CaCO3 / Al, BaF2 / Ca / Al, etc.; the alloy electrode with a relatively low work function can be Au:Mg or Ag:Mg, etc.

[0082] For example, the thickness of the hole transport layer 30 is 10nm-100nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc. In some embodiments, the thickness of the hole transport layer 30 is 70nm-90nm.

[0083] For example, the thickness of the hole injection layer 20 is 20nm-120nm, such as 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, etc. In some embodiments, the thickness of the hole injection layer 20 is 70nm-90nm.

[0084] For example, the thickness of the electron transport layer 50 is 15nm-60nm, such as 15nm, 20nm, 30nm, 40nm, 50nm, 60nm, etc. In some embodiments, the thickness of the electron transport layer 50 is 40nm-60nm.

[0085] For example, the thickness of the first electrode 10 and the thickness of the second electrode 60 are each 10nm-125nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 125nm, etc. In some embodiments, the thickness of the anode is 115nm-125nm, and the thickness of the cathode is 55nm-65nm.

[0086] Exemplarily, the light-emitting device 100 may further include a substrate disposed on one side of the first electrode 10. Exemplarily, the substrate may be a rigid substrate or a flexible substrate. In some embodiments, the material of the substrate may be selected from, but is not limited to, at least one of glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, and polyethersulfone.

[0087] Please see Figure 6 At the same time, combined Figure 5 This application provides a method for fabricating a light-emitting device, comprising:

[0088] S310, a first electrode 10 is provided, and a quantum dot film 40 is prepared on the first electrode 10. The quantum dot film 40 includes a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures, including a zincblende structure, a wurtzite structure, a NaCl-type structure, or a CsCl-type structure.

[0089] Please combine Figure 3For example, the fabrication of the quantum dot thin film 40 on the first electrode 10 includes:

[0090] A composite quantum dot solution is provided, the composite quantum dot solution comprising a quantum dot material and a solvent, the quantum dot material comprising a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures;

[0091] The composite quantum dot solution was deposited to obtain a quantum dot film 40.

[0092] Please combine Figure 4 For example, the fabrication of the quantum dot thin film 40 on the first electrode 10 includes:

[0093] A first quantum dot solution is provided, the first quantum dot solution comprising a first quantum dot and a solvent, and the first quantum dot solution is deposited to obtain a first unit film layer;

[0094] A second quantum dot solution is provided, the second quantum dot solution comprising a second quantum dot and a solvent, and the second quantum dot solution is deposited on the first unit film layer to obtain a second unit film layer, forming a quantum dot thin film 40, wherein the quantum dot thin film 40 comprises a first unit film layer and a second unit film layer stacked together.

[0095] S320, a second electrode 60 is formed on the side of the quantum dot film 40 opposite to the first electrode 10.

[0096] For example, when the first electrode 10 is the anode and the second electrode 60 is the cathode, the preparation of the quantum dot film on the first electrode includes: sequentially preparing a hole injection layer, a hole transport layer and a quantum dot film 40 on the first electrode 10; the formation of the second electrode on the side of the quantum dot film opposite to the first electrode includes: preparing an electron transport layer on the quantum dot film 40 and preparing the second electrode 60 on the electron transport layer.

[0097] For example, when the first electrode 10 is a cathode and the second electrode 60 is an anode, the preparation of a quantum dot film on the first electrode includes: preparing an electron transport layer on the first electrode 10 and preparing a quantum dot film 40 on the electron transport layer; the formation of a second electrode on the side of the quantum dot film opposite to the first electrode includes: sequentially preparing a hole transport layer, a hole injection layer and a second electrode 60 on the quantum dot film 40.

[0098] This application also provides a display device, including a light-emitting device 100 prepared by the method of preparing the light-emitting device in any of the above embodiments, or a light-emitting device 100 in any of the above embodiments.

[0099] For example, the display device can be a terminal such as a television, mobile phone, tablet computer, monitor, or advertising display screen, or it can be a device with a display screen such as a gaming device, augmented reality (AR) device, virtual reality (VR) device, data storage device, audio playback device, video playback device, or wearable device. Wearable devices can be smart bracelets, smart glasses, smartwatches, smart decorations, etc.

[0100] The quantum dot thin film and its preparation method, as well as the light-emitting device and its preparation method, of this application are described in detail below with reference to specific embodiments.

[0101] In the following embodiments, the average particle size of the quantum dots was obtained by using a laser particle size analyzer and dynamic light scattering method. The working principle of dynamic light scattering method is as follows: when light shines on small particles much smaller than its wavelength, the light will be scattered in all directions. At the same time, since the tiny particles in the solution are always in constant random motion, the intensity of the scattered light will fluctuate over time. The scattered light signal is then received by a receiver, and the average particle size is calculated by the Stokes-Einstein equation.

[0102] The film thickness was measured using a profilometer. The working principle of the profilometer is as follows: when the probe of the profilometer gently slides across the surface of the object being measured, the tiny peaks and valleys on the surface of the object will cause the probe to move up and down while sliding. Therefore, the surface contour is reflected to a certain extent by the movement of the probe. When the output signal passes through the measuring bridge, the output signal is proportional to the displacement of the probe's equilibrium position, and the amplitude-modulated signal appears accordingly. After amplification and rectification, the displacement signal is demodulated from the amplitude-modulated signal, and the signal becomes correspondingly slower. Subsequently, noise filters and waviness filters further filter out factors such as the modulation frequency and external interference signals, and the impact of errors is reduced.

[0103] Thin Film Example 1

[0104] A quantum dot thin film, the preparation method of which includes:

[0105] Step 11: Provide a composite quantum dot solution, which includes quantum dot materials and a solvent (n-octane). The quantum dot materials include quantum dots with a zincblende structure (ZnS / CdSe / ZnS) and quantum dots with a wurtzite structure (ZnSe / CdZnSe). The average particle size of the quantum dots with a zincblende structure (ZnS / CdSe / ZnS) is 8 nm, the average particle size of the quantum dots with a wurtzite structure (ZnSe / CdZnSe) is 8 nm, the mass ratio of the quantum dots with a zincblende structure to the quantum dots with a wurtzite structure is 1:1, and the concentration of the composite quantum dot solution is 30 mg / ml.

[0106] Step 12: Deposit the composite quantum dot solution using spin coating at a speed of 2000 r / min for 30 seconds. After spin coating, anneal in a glove box under nitrogen atmosphere at a temperature of 80°C for 10 minutes to obtain a quantum dot film with a thickness of 40 nm.

[0107] Thin Film Example 2

[0108] A quantum dot thin film, the preparation method of which differs from that of thin film Example 1 in that:

[0109] In the composite quantum dot solution provided in step 11, the average particle size of the quantum dots with the zincblende structure is 7 nm, and the average particle size of the quantum dots with the wurtzite structure is 10 nm.

[0110] Thin Film Example 3

[0111] A quantum dot thin film, the preparation method of which differs from that of thin film Example 1 in that:

[0112] In the composite quantum dot solution provided in step 11, the mass ratio of quantum dots with a zincblende structure to quantum dots with a wurtzite structure is 0.8:1.2.

[0113] Thin Film Example 4

[0114] A quantum dot thin film, the preparation method of which differs from that of thin film Example 1 in that:

[0115] In the composite quantum dot solution provided in step 11, the mass ratio of quantum dots with a zincblende structure to quantum dots with a wurtzite structure is 1.2:0.8.

[0116] Thin Film Example 5

[0117] A quantum dot thin film, the preparation method of which includes:

[0118] Step 21: Provide a first quantum dot solution, which includes quantum dots (ZnS / CdSe / ZnS) with a zincblende structure and a solvent (toluene). The concentration of the first quantum dot solution is 30 mg / ml, and the average particle size of the quantum dots (ZnS / CdSe / ZnS) with a zincblende structure is 8 nm. Deposit the first quantum dot solution by spin coating at a speed of 3500 r / min for 30 seconds. After spin coating, anneal in a glove box under a nitrogen atmosphere at a temperature of 80 °C for 10 minutes to obtain a first unit film with a thickness of 20 nm.

[0119] Step 22: Provide a second quantum dot solution, which includes quantum dots (ZnSe / CdZnSe) with a wurtzite structure and a solvent (water). The average particle size of the quantum dots (ZnSe / CdZnSe) with a wurtzite structure is 8 nm. The concentration of the second quantum dot solution is 30 mg / ml. The second quantum dot solution is deposited on the first unit film layer by spin coating at a speed of 3500 r / min for 30 seconds. After spin coating, the film is annealed in a glove box under a nitrogen atmosphere at a temperature of 80°C for 10 minutes to obtain the second unit film layer with a thickness of 20 nm, forming a quantum dot film. The quantum dot film consists of a first unit film layer (zincblende structure quantum dots, 20 nm) and a second unit film layer (wurtzite structure quantum dots, 20 nm) stacked together.

[0120] Thin Film Example 6

[0121] A quantum dot thin film, the preparation method of which differs from that in Thin Film Example 5, is as follows:

[0122] In step 21, the average particle size of the quantum dots (ZnS / CdSe / ZnS) with the zincblende structure in the first quantum dot solution is 7 nm.

[0123] In step 22, the average particle size of the quantum dots (ZnSe / CdZnSe) with wurtzite structure in the second quantum dot solution is 10 nm.

[0124] Thin Film Example 7

[0125] A quantum dot thin film, the preparation method of which differs from that in Thin Film Example 5, is as follows:

[0126] In step 21, the average particle size of the quantum dots (ZnS / CdSe / ZnS) with zincblende structure in the first quantum dot solution is 6 nm.

[0127] In step 22, the average particle size of the quantum dots (ZnSe / CdZnSe) with wurtzite structure in the second quantum dot solution is 10 nm.

[0128] Thin Film Example 8

[0129] A quantum dot thin film, the preparation method of which includes:

[0130] Step 21: Provide a first quantum dot solution, which includes quantum dots (ZnS / CdSe / ZnS) with a zincblende structure and a solvent (toluene). The concentration of the first quantum dot solution is 30 mg / ml, and the average particle size of the quantum dots (ZnS / CdSe / ZnS) with a zincblende structure is 8 nm. Deposit the first quantum dot solution by spin coating at a speed of 4200 r / min for 30 seconds. After spin coating, anneal in a glove box under a nitrogen atmosphere at a temperature of 80 °C for 10 minutes to obtain a first unit film with a thickness of 10 nm.

[0131] Step 22: Provide a second quantum dot solution, which includes quantum dots (ZnSe / CdZnSe) with a wurtzite structure and a solvent (water). The concentration of the second quantum dot solution is 30 mg / ml, and the average particle size of the quantum dots (ZnSe / CdZnSe) with a wurtzite structure is 8 nm. Deposit the second quantum dot solution on the first unit film layer using a spin coating method at a rotation speed of 4200 r / min and a spin coating time of 30 seconds. After spin coating, anneal in a glove box under a nitrogen atmosphere at an annealing temperature of 80 °C for 10 minutes to obtain the second unit film layer with a thickness of 10 nm.

[0132] Step 23: Provide a first quantum dot solution, which includes quantum dots (ZnS / CdSe / ZnS) with a zincblende structure and a solvent (toluene). The concentration of the first quantum dot solution is 30 mg / ml, and the average particle size of the quantum dots (ZnS / CdSe / ZnS) with a zincblende structure is 8 nm. Deposit the first quantum dot solution on the second unit film layer using a spin coating method at a rotation speed of 4200 r / min and a spin coating time of 30 seconds. After spin coating, anneal in a glove box under a nitrogen atmosphere at an annealing temperature of 80 °C for 10 minutes to obtain a third unit film layer with a thickness of 10 nm.

[0133] Step 24: Provide a second quantum dot solution, which includes quantum dots (ZnSe / CdZnSe) with a wurtzite structure and a solvent (water). The concentration of the second quantum dot solution is 30 mg / ml. The average particle size of the quantum dots (ZnSe / CdZnSe) with a wurtzite structure is 8 nm. The second quantum dot solution is deposited on the third unit film layer by spin coating at a speed of 4200 r / min for 30 seconds. After spin coating, the film is annealed in a glove box under a nitrogen atmosphere at a temperature of 80°C for 10 minutes to obtain a fourth unit film layer with a thickness of 10 nm, forming a quantum dot film. The quantum dot film consists of a first unit film layer (zincblende structure quantum dots, 10 nm), a second unit film layer (zincblende structure quantum dots, 10 nm), a third unit film layer (zincblende structure quantum dots, 10 nm), and a fourth unit film layer (zincblende structure quantum dots, 10 nm) stacked together.

[0134] Thin Film Example 9

[0135] A quantum dot thin film, the preparation method of which includes:

[0136] Step 21: Provide a first quantum dot solution, which includes quantum dots (ZnS / CdSe / ZnS) with a zincblende structure and a solvent (toluene). The concentration of the first quantum dot solution is 30 mg / ml, and the average particle size of the quantum dots (ZnS / CdSe / ZnS) with a zincblende structure is 8 nm. Deposit the first quantum dot solution by spin coating at a speed of 4200 r / min for 30 seconds. After spin coating, anneal in a glove box under a nitrogen atmosphere at a temperature of 80 °C for 10 minutes to obtain a first unit film with a thickness of 13 nm.

[0137] Step 22: Provide a second quantum dot solution, which includes quantum dots (ZnSe / CdZnSe) with a wurtzite structure and a solvent (water). The concentration of the second quantum dot solution is 30 mg / ml, and the average particle size of the quantum dots (ZnSe / CdZnSe) with a wurtzite structure is 8 nm. Deposit the second quantum dot solution on the first unit film layer using a spin coating method at a rotation speed of 3500 r / min and a spin coating time of 30 seconds. After spin coating, anneal in a glove box under a nitrogen atmosphere at an annealing temperature of 80 °C for 10 minutes to obtain the second unit film layer with a thickness of 14 nm.

[0138] Step 23: Provide a first quantum dot solution, which includes quantum dots (ZnS / CdSe / ZnS) with a zincblende structure and a solvent (toluene). The concentration of the first quantum dot solution is 30 mg / ml. The average particle size of the quantum dots (ZnS / CdSe / ZnS) with a zincblende structure is 8 nm. Deposit the first quantum dot solution on the second unit film layer using a spin coating method at a rotation speed of 4200 r / min and a spin coating time of 30 seconds. After spin coating, anneal in a glove box under a nitrogen atmosphere at an annealing temperature of 80 °C for 10 minutes to obtain a third unit film layer with a thickness of 10 nm, forming a quantum dot film. The quantum dot film consists of a first unit film layer (zincblende structure quantum dots, 13 nm), a second unit film layer (wurtzite structure quantum dots, 14 nm), and a third unit film layer (zincblende structure quantum dots, 13 nm) stacked together.

[0139] Thin Film Comparative Example 1

[0140] A quantum dot thin film, the preparation method of which includes:

[0141] Step 101: Provide a quantum dot solution, which includes quantum dot material and solvent (toluene). The quantum dot material includes quantum dots (ZnS / CdSe / ZnS) with a zincblende structure and an average particle size of 8 nm. The concentration of the quantum dot solution is 30 mg / ml.

[0142] Step 102: Deposit quantum dot solution by spin coating at a speed of 2000 r / min for 30 seconds. After spin coating, anneal in a glove box under nitrogen atmosphere at a temperature of 80°C for 10 minutes to obtain a quantum dot film with a thickness of 40 nm.

[0143] It can be seen that the quantum dot film prepared in Comparative Example 1 is a quantum dot with a single crystal structure (i.e., zincblende structure).

[0144] Thin Film Comparative Example 2

[0145] A quantum dot thin film, the preparation method of which includes:

[0146] Step 101: Provide a quantum dot solution, which includes quantum dot material and solvent (water). The quantum dot material includes quantum dots (ZnSe / CdZnSe) with a wurtzite structure and an average particle size of 8 nm. The concentration of the quantum dot solution is 30 mg / ml.

[0147] Step 102: Deposit quantum dot solution by spin coating at a speed of 2000 r / min for 30 seconds. After spin coating, anneal in a glove box under nitrogen atmosphere at a temperature of 80°C for 10 minutes to obtain a quantum dot film with a thickness of 40 nm.

[0148] It can be seen that the quantum dot film prepared in Comparative Example 2 is a quantum dot with a single crystal structure (i.e., wurtzite structure).

[0149] Device Example 1

[0150] A light-emitting device, the method for fabricating which includes:

[0151] Step S1: Place the glass substrate with an anode (ITO) in a glass dish, and ultrasonically clean it for 20 minutes each with detergent, acetone, deionized water and ethanol in sequence. Then, dry it thoroughly in an oven. Next, place the cleaned ITO glass sheet in oxygen plasma for 10 minutes. Finally, treat the substrate surface with ultraviolet-ozone for 15 minutes.

[0152] Step S2: Spin-coat PEDOT:PSS onto the side of the anode facing away from the glass substrate at a speed of 3500 r / min for 30 seconds. After spin-coating, place the wafer in air for annealing at a temperature of 150°C for 30 minutes to obtain a hole injection layer with a thickness of 25 nm. After annealing, quickly transfer the wafer to a glove box in a nitrogen atmosphere.

[0153] Step S3: Spin coat TFB onto the hole injection layer at a speed of 4000 r / min for 30 seconds. After spin coating, anneal in a glove box at a temperature of 180°C for 30 minutes to obtain a hole transport layer with a thickness of 15 nm.

[0154] Step S4: Prepare quantum dot films on the hole transport layer using the method of Thin Film Example 1;

[0155] Step S5: Curing the unfinished components in a UV curing oven (120mW / cm²) under a nitrogen atmosphere in a glove box. 2 Irradiate for 5 minutes to cure the quantum dot film;

[0156] Step S6: Spin-coat a zinc oxide dispersion solution onto a quantum dot film. The zinc oxide dispersion solution includes zinc oxide nanoparticles and ethanol. The average particle size of the zinc oxide nanoparticles is 3.5 nm, and the concentration of the zinc oxide nanoparticles is 30 mg / mL. The zinc oxide dispersion solution is annealed at 80 °C for 10 minutes to completely evaporate the solvent ethanol in the zinc oxide dispersion solution, thereby obtaining an electron transport layer with a thickness of 40 nm.

[0157] Step S7: Deposit Ag on the electron transport layer to obtain a cathode with a thickness of 100 nm, thus obtaining an optoelectronic device.

[0158] Device Example 2

[0159] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0160] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of thin film example 2.

[0161] Device Example 3

[0162] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0163] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of thin film example 3.

[0164] Device Example 4

[0165] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0166] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of thin film example 4.

[0167] Device Example 5

[0168] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0169] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of thin film example 5.

[0170] Device Example 6

[0171] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0172] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of Thin Film Example 6.

[0173] Device Example 7

[0174] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0175] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of thin film example 7.

[0176] Device Example 8

[0177] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0178] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of Thin Film Example 8.

[0179] Device Example 9

[0180] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0181] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of Thin Film Example 9.

[0182] Device Comparison Example 1

[0183] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0184] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of thin film comparative example 1.

[0185] Device Comparison Example 2

[0186] A light-emitting device, the method of which is prepared differs from that of device embodiment 1 in that:

[0187] In step S4, a quantum dot thin film is prepared on the hole transport layer using the method of thin film comparative example 2.

[0188] Device performance testing:

[0189] (1) Luminous efficiency EQE (%): Measured using optical testing instruments (F-STAROptical Measurement Systems).

[0190] (2) The test method for lifespan T95@1000nit is as follows:

[0191] The time required for a device's brightness to decrease to a certain percentage of its maximum brightness under constant current or voltage drive, defined as T95, is the time it takes for the brightness to drop to 95% of its maximum brightness. This lifetime is the measured lifetime. To shorten the testing cycle, device lifetime testing is usually performed at high brightness by accelerating device aging, and the lifetime at high brightness is obtained by fitting an extended exponential decay brightness decay formula. For example, the lifetime at 1000 nits is measured as T95@1000nits. The specific calculation formula is as follows:

[0192]

[0193] Among them, T95 L For longer lifespan at low brightness, T95 H For the measured lifetime under high brightness, L HTo accelerate the device to its maximum brightness, L L The value is 1000 nits, and A is the acceleration factor. In this experiment, the lifetime of several groups of green QLED devices under rated brightness was measured, and the value of A was found to be 1.7.

[0194] The device performance test results are shown in Table 1:

[0195] Table 1

[0196]

[0197]

[0198] As shown in Table 1, the luminous efficiency (EQE) of the light-emitting devices prepared in Device Comparative Example 1 and Device Comparative Example 2 is lower than that of the light-emitting devices prepared in Device Examples 1-9 of this application. The T95 lifetime of the light-emitting devices prepared in Device Comparative Example 1 and Device Comparative Example 2 is also lower than that of the light-emitting devices prepared in Device Examples 1-9 of this application. The difference between Device Examples 1-9, Device Comparative Example 1, and Device Comparative Example 2 is that the quantum dot films prepared in Device Examples 1-9 contain two different quantum dots (zincblende structure quantum dots and wurtzite structure quantum dots), while the quantum dot film prepared in Device Comparative Example 1 uses a single quantum dot (zincblende structure quantum dot), and the quantum dot film prepared in Device Comparative Example 2 uses a single quantum dot (wurtzite structure quantum dot). This indicates that when the quantum dot film contains at least two different quantum dots, the electron mobility of the quantum dot film can be reduced, thereby alleviating or eliminating the imbalance of electron and hole injection in the quantum dot film, promoting carrier balance, and thus helping to improve the luminous efficiency (EQE) and lifetime of the light-emitting device.

[0199] By comparing Device Examples 5, 6, and 7, it can be seen that the luminous efficiency (EQE) and T95 lifespan of the light-emitting devices prepared in Device Examples 5 and 6 are greater than those of the light-emitting device prepared in Device Example 7. The difference between Device Examples 5, 6, and 7 is that the difference in average particle size between the first and second unit layers of the quantum dot film prepared in Device Examples 5 and 6 is less than or equal to 3 nm, while the difference in average particle size between the first and second unit layers of the quantum dot film prepared in Device Example 7 is greater than 3 nm. This indicates that when the difference in average particle size of quantum dots in adjacent unit layers is less than or equal to 3 nm, the injection of electrons and holes in the prepared quantum dot film is more balanced, which is beneficial for improving the luminous efficiency (EQE) and lifespan of the light-emitting device.

[0200] The light-emitting devices and their fabrication 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 embodiments above are only for the purpose of helping to understand this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A light-emitting device, characterized in that, The device includes a first electrode and a second electrode disposed opposite to each other, and a quantum dot film disposed between the first electrode and the second electrode. The quantum dot film includes a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures.

2. The light-emitting device according to claim 1, characterized in that, The crystal structure includes zincblende structure, wurtzite structure, NaCl type structure or CsCl type structure; And / or, the average particle size of the first quantum dot is 1nm-30nm; And / or, the average particle size of the second quantum dot is 1nm-30nm.

3. The light-emitting device according to claim 1, characterized in that, The quantum dot film is a single-layer film, in which first quantum dots and second quantum dots are distributed, and the first quantum dots and second quantum dots may have the same or different constituent elements. And / or, the mass ratio of the first quantum dot to the second quantum dot is (0.8-1.2):(0.8-1.2); And / or, when two or more quantum dots are distributed in the monolayer film, the crystal structures of any two quantum dots are different, and the ratio of the mass of any one quantum dot to the total mass of the quantum dots in the monolayer film is less than or equal to 1 / 2.

4. The light-emitting device according to claim 1, characterized in that, The quantum dot film comprises multiple unit film layers stacked together, wherein the crystal structures of the quantum dots in any two adjacent unit film layers are different. The multiple unit film layers include a first unit film layer and a second unit film layer stacked together. The material of the first unit film layer includes a first quantum dot, and the material of the second unit film layer includes a second quantum dot.

5. The light-emitting device according to claim 4, characterized in that, In a multi-unit film layer, the quantum dots in any two unit film layers may have the same or different compositions; And / or, the absolute value of the difference in the average particle size of quantum dots in any two adjacent unit films is less than or equal to 3 nm; And / or, the quantum dot film includes alternating layers of zincblende quantum dot film and wurtzite quantum dot film, wherein the number of zincblende quantum dot film layers is at least one and the number of wurtzite quantum dot film layers is at least one. And / or, the thickness of any two adjacent unit films is the same or the absolute value of the difference is less than or equal to 4 nm.

6. The light-emitting device according to any one of claims 1-5, characterized in that, The thickness of the quantum dot film is 10nm-80nm; and / or The first quantum dot and the second quantum dot each comprise at least one of a single-structure quantum dot and a core-shell structure quantum dot. The material of the single-structure quantum dot, the core material of the core-shell structure quantum dot, and the shell material of the core-shell structure quantum dot each comprise at least one of group II-VI compounds, group IV-VI compounds, group III-V compounds, and group I-III-VI compounds. The group II-VI compounds are selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, and CdSTe. At least one of ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe, wherein the IV-VI compound is selected from SnS, SnSe, SnTe, PbS, and PbSe. At least one of PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, and SnPbSTe, wherein the III-V compound is selected from GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, and AlPAs. At least one of the following: AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb, wherein the group I-III-VI compound is selected from at least one of CuInS2, CuInSe2, CuInSeS, and AgInS2; and / or The surface of the first quantum dot and / or the second quantum dot is connected to a ligand, the ligand including at least one of acid ligand, thiol ligand, amine ligand, phosphophosphine ligand, phospholipid, lecithin, and polyvinylpyridine, the acid ligand being at least one of decaic acid, undecenoic acid, tetradecanoic acid, oleic acid, and stearic acid, the thiol ligand being at least one of octyl mercaptan, dodecyl mercaptan, and octadecyl mercaptan, the amine ligand being at least one of oleylamine, octadecylamine, octylamine, dioctylamine, and trioctylamine, and the phosphophosphine ligand being at least one of trioctylphosphine, tributylphosphine, and trioctylphosphine oxychloride.

7. The light-emitting device according to claim 1, characterized in that, The light-emitting device includes a first electrode, a hole-functional layer, a quantum dot thin film, an electronic functional layer, and a second electrode stacked sequentially. The hole functional layer comprises a hole injection layer and a hole transport layer. The hole injection layer is disposed on the side closest to the first electrode. The hole transport layer is made of materials including 4,4'-N,N'-dicarbazolyl-biphenyl, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine, and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-di Amines, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine, 4,4',4'-tris(N-carbazolyl)-triphenylamine, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))], poly(N-vinylcarbazole) and its derivatives, N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine, poly(phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene], 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene, 4,4'-cyclohexyldi[N,N-di( At least one of the following: 4-methylphenyl)aniline, 1,3-bis(carbazole-9-yl)benzene, polyaniline, polypyrrole, poly(p-)phenylenevinylene, aromatic tertiary amine, polynuclear aromatic tertiary amine, 4,4'-bis(p-carbazole)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, polyspirofluorene and its derivatives, and polythiophene and its derivatives; and / or The hole injection layer is made of at least one of the following materials: poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid and its derivatives, copper phthalocyanine, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene, polydioxyethyl thiophene, 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine, tetracyanoquinone dimethyl ether, transition metal oxides, and transition metal chalcogenides; and / or The electronic functional layer includes an electron transport layer. The material of the electron transport layer includes at least one of a metal oxide, a doped metal oxide, a group II-VI semiconductor material, a group III-V semiconductor material, and a group I-III-VI semiconductor material. The metal oxide is selected from at least one of ZnO, BaO, TiO2, and SnO2; the doped metal oxide is selected from at least one of ZnO, TiO2, and SnO2, and the doping element is selected from at least one of Al, Mg, Li, In, and Ga; the group II-VI semiconductor material is selected from at least one of ZnS, ZnSe, and CdS; the group III-V semiconductor material is selected from at least one of InP and GaP; and the group I-III-VI semiconductor material is selected from at least one of CuInS and CuGaS; and / or The first electrode and the second electrode are each independently selected from doped metal oxide electrodes, composite electrodes, graphene electrodes, carbon nanotube electrodes, elemental metal electrodes, or alloy electrodes. The materials of the doped metal oxide electrodes include one or more of indium-doped tin oxide, fluorine-doped tin oxide, antimony-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, indium-doped zinc oxide, magnesium-doped zinc oxide, and aluminum-doped magnesium oxide. The composite electrodes include 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, or ZnS / Al / ZnS. The materials of the elemental metal electrodes include one or more of Ag, Al, Cu, Mo, Au, Pt, Ca, Mg, and Ba.

8. A method for fabricating a light-emitting device, characterized in that, include: A first electrode is provided, and a quantum dot film is prepared on the first electrode. The quantum dot film includes a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures, including a zincblende structure, a wurtzite structure, a NaCl-type structure, or a CsCl-type structure. A second electrode is formed on the side of the quantum dot film opposite to the first electrode.

9. The method for fabricating a light-emitting device according to claim 8, characterized in that, The preparation of the quantum dot thin film on the first electrode includes: A composite quantum dot solution is provided, the composite quantum dot solution comprising a quantum dot material and a solvent, the quantum dot material comprising a first quantum dot and a second quantum dot, wherein the first quantum dot and the second quantum dot have different crystal structures; The composite quantum dot solution was deposited to obtain a quantum dot film.

10. The method for preparing a light-emitting device according to claim 8, characterized in that, The preparation of the quantum dot thin film on the first electrode includes: A first quantum dot solution is provided, the first quantum dot solution comprising a first quantum dot and a solvent, and the first quantum dot solution is deposited to obtain a first unit film layer; A second quantum dot solution is provided, the second quantum dot solution comprising a second quantum dot and a solvent, and the second quantum dot solution is deposited on the first unit film layer to obtain a second unit film layer, thereby forming a quantum dot thin film, wherein the quantum dot thin film comprises a first unit film layer and a second unit film layer stacked together.

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