Quantum dot light-emitting device and preparation method therefor, and display device

Abstract

Disclosed in the present invention are a quantum dot light-emitting device and a preparation method therefor, and a display device. The quantum dot light-emitting device comprises: a quantum dot light-emitting layer; and an electron transport layer located on one side of the quantum dot light-emitting layer, the material of the electron transport layer comprising Zn, S and Se elements.

Description

Quantum dot light emitting device, preparation method thereof and display device TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of display, and in particular to a quantum dot light emitting device, a preparation method thereof and a display device. BACKGROUND

[0002] As a new type of light emitting material, quantum dots (QDs) have the advantages of high light color purity, high light emitting quantum efficiency, adjustable light emitting color, long service life, etc., and have become a research hotspot of light emitting materials in new type light emitting diodes. Therefore, quantum dot light emitting diodes (QLEDs) using quantum dot materials as light emitting layers have become the main direction of research on new type display devices.

[0003] However, the current quantum dot light emitting diodes still have problems of low light emitting efficiency and poor stability. SUMMARY

[0004] Embodiments of the present disclosure provide a quantum dot light emitting device, a preparation method thereof and a display device, and the specific solutions are as follows.

[0005] The quantum dot light emitting device provided in the embodiments of the present disclosure includes a quantum dot light emitting layer and an electron transport layer located on one side of the quantum dot light emitting layer, and the material of the electron transport layer includes Zn element, S element and Se element.

[0006] In a possible implementation, in the quantum dot light emitting device provided in the embodiments of the present disclosure, the material of the electron transport layer is ZnSe 1-x S x alloy structure, 0 < x < 1.

[0007] In a possible implementation, in the quantum dot light emitting device provided in the embodiments of the present disclosure, the total content of S and the total content of Se in the electron transport layer are the same.

[0008] In a possible implementation, in the quantum dot light emitting device provided in the embodiments of the present disclosure, along a direction from the side of the electron transport layer close to the quantum dot light emitting layer to the side of the electron transport layer far away from the quantum dot light emitting layer, the content of S in the electron transport layer gradually decreases, and the content of Se in the electron transport layer gradually increases.

[0009] In one possible implementation, in the quantum dot light-emitting device provided in the embodiments of this disclosure, the valence band position of the electron transport layer is -6.8eV to -6.36eV, and the conduction band position is -3.2eV to -3.46eV.

[0010] In one possible implementation, in the quantum dot light-emitting device provided in the embodiments of this disclosure, the electron transport layer includes: a first electron transport layer located on one side of the quantum dot light-emitting layer, and a second electron transport layer located on the side of the first electron transport layer opposite to the quantum dot light-emitting layer; wherein...

[0011] The first electron transport layer is made of ZnS, which is composed of Zn and S elements, and the second electron transport layer is made of ZnSe, which is composed of Zn and Se elements.

[0012] Alternatively, the material of the first electron transport layer is ZnSe, which is composed of Zn and Se elements, and the material of the second electron transport layer is ZnS, which is composed of Zn and S elements.

[0013] In one possible implementation, in the quantum dot light-emitting device provided in the embodiments of this disclosure, the materials of the quantum dot light-emitting layer and the electron transport layer include at least two identical elements.

[0014] In one possible implementation, in the quantum dot light-emitting device provided in the embodiments of this disclosure, the material of the quantum dot light-emitting layer includes quantum dot materials and ZnS or ZnSe located in the gaps between the quantum dot materials.

[0015] In one possible implementation, in the quantum dot light-emitting device provided in the embodiments of this disclosure, the quantum dot material includes at least one of the following:

[0016] InP, CdS, CdSe, ZnSe, ZnTeSe, PbS, CsPbCl3, CsPbBr3, CsPbI3, ZnSe, ZnSeTe, CdS / ZnS, CdSe / ZnS, InP / ZnS, PbS / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, CsPbI3 / ZnS, InP / ZnSe / ZnS, InP / ZnS / ZnSe, CdS / ZnSeS / ZnS, CdSe / ZnSeS / ZnS, ZnSe / ZnSeS / ZnS, ZnSeTe / ZnSeS / ZnS.

[0017] In one possible implementation, in the quantum dot light-emitting device provided in the embodiments of this disclosure, the electron transport layer is a thin film structure, and the root mean square roughness of the surface of the electron transport layer is 0.1-0.5 nm.

[0018] In one possible implementation, the quantum dot light-emitting device provided in the embodiments of this disclosure further includes: a hole transport layer located on the side of the quantum dot light-emitting layer away from the electron transport layer, a hole injection layer located on the side of the hole transport layer away from the electron transport layer, an anode located on the side of the hole injection layer away from the electron transport layer, and a cathode located on the side of the electron transport layer away from the quantum dot light-emitting layer.

[0019] Accordingly, this disclosure also provides a display device, including the quantum dot light-emitting device described above in this disclosure.

[0020] Accordingly, this disclosure also provides a method for fabricating a quantum dot light-emitting device, used to fabricate the quantum dot light-emitting device provided in this disclosure, the fabrication method comprising:

[0021] A quantum dot light-emitting layer and an electron transport layer are formed in a stacked configuration, wherein the electron transport layer is made of Zn, S, and Se elements.

[0022] In one possible implementation, in the preparation method provided in the embodiments of this disclosure, the formation of the stacked quantum dot light-emitting layer and electron transport layer specifically includes:

[0023] Form the quantum dot light-emitting layer;

[0024] On one side of the quantum dot light-emitting layer and along the direction away from the quantum dot light-emitting layer, ZnSe and ZnS are simultaneously deposited at gradient rates to form a ZnSe material. 1-x S x The electron transport layer of the alloy structure; wherein the rates of ZnSe and ZnS deposition change in opposite directions, and ZnS is deposited at the initial moment and ZnSe is deposited at the final moment, 0 < x < 1.

[0025] In one possible implementation, in the preparation method provided in the embodiments of this disclosure, the first evaporation rate is greater than or equal to the second evaporation rate.

[0026] In one possible implementation, in the preparation method provided in the embodiments of this disclosure, the formation of the stacked quantum dot light-emitting layer and electron transport layer specifically includes:

[0027] Form the quantum dot light-emitting layer;

[0028] A first electron transport layer is formed on one side of the quantum dot light-emitting layer, and the material of the first electron transport layer is ZnS;

[0029] A second electron transport layer is formed on the side of the first electron transport layer away from the quantum dot light-emitting layer, and the material of the second electron transport layer is ZnSe.

[0030] In one possible implementation, in the preparation method provided in the embodiments of this disclosure, the formation of the stacked quantum dot light-emitting layer and electron transport layer specifically includes:

[0031] Form the quantum dot light-emitting layer;

[0032] A first electron transport layer is formed on one side of the quantum dot light-emitting layer, and the material of the first electron transport layer is ZnSe;

[0033] A second electron transport layer is formed on the side of the first electron transport layer away from the quantum dot light-emitting layer, and the material of the second electron transport layer is ZnS. Attached Figure Description

[0034] Figure 1 is a schematic diagram of a quantum dot light-emitting device provided in an embodiment of this disclosure;

[0035] Figure 2 is a schematic diagram of another structure of the quantum dot light-emitting device provided in the embodiments of this disclosure;

[0036] Figure 3 is a schematic diagram of another structure of the quantum dot light-emitting device provided in the embodiments of this disclosure;

[0037] Figure 4 is a schematic flowchart of a method for fabricating a quantum dot light-emitting device according to an embodiment of this disclosure;

[0038] Figure 5 is a schematic flowchart of another method for fabricating a quantum dot light-emitting device provided in an embodiment of this disclosure;

[0039] Figure 6 is a schematic flowchart of another method for fabricating a quantum dot light-emitting device provided in an embodiment of this disclosure;

[0040] Figure 7 shows the current density-voltage-brightness curves of the quantum dot light-emitting devices of Embodiment 1 and Comparative Example 1 of this disclosure;

[0041] Figure 8 shows the brightness-external quantum efficiency curves of the quantum dot light-emitting devices of Embodiment 1 and Comparative Example 1 of this disclosure;

[0042] Figure 9 shows the lifetime curves of the quantum dot light-emitting devices of Embodiment 1 and Comparative Example 1 of this disclosure. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Furthermore, the embodiments and features in the embodiments of this disclosure can be combined with each other without conflict. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0044] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "comprising" or "including," and similar terms as used in this disclosure, mean that an element or object preceding the term encompasses the elements or objects listed following the term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "inner," "outer," "upper," and "lower" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0045] It should be noted that the dimensions and shapes of the figures in the accompanying drawings do not reflect actual proportions and are intended only to illustrate the content of this disclosure. Furthermore, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0046] Quantum dots composed of Group II and Group VI elements have high quantum yields, but many of them contain the heavy metal cadmium. Cadmium is a pollutant that can impact human health and the natural environment. Therefore, current research on quantum dots mainly focuses on green and environmentally friendly cadmium-free quantum dots. Among them, indium phosphide (InP) quantum dots are widely used in QLED devices, but green InP QLEDs still face problems such as low luminous efficiency and poor stability.

[0047] This disclosure provides a quantum dot light-emitting device, as shown in Figures 1-3, including: a quantum dot light-emitting layer 1, and an electron transport layer 2 located on one side of the quantum dot light-emitting layer 1; the material of the electron transport layer 2 includes Zn, S and Se elements.

[0048] The quantum dot light-emitting device provided in this disclosure has an electron transport layer made of Zn, S, and Se elements. Since the shell structure of the quantum dot material in the quantum dot light-emitting layer is generally ZnS or ZnSe, the ZnS or ZnSe deposited at the beginning of electron transport layer fabrication can enter the gaps between the quantum dots without altering their original structure, thus preventing the introduction of new defects and suppressing leakage current. Furthermore, the electron transport material composed of Zn, S, and Se effectively blocks holes and transports electrons, improving electron injection in the quantum dot light-emitting device. Moreover, the electron transport material composed of Zn, S, and Se has better stability and fewer defects than traditional ZnO, which is beneficial for achieving quantum dot light-emitting devices with high luminous efficiency and high stability. Therefore, the quantum dot light-emitting device provided in this disclosure can significantly improve the luminous efficiency and stability of the device.

[0049] In some embodiments, in the quantum dot light-emitting device provided in the present disclosure, as shown in FIG1, the material of the electron transport layer 2 is ZnSe composed of Zn, S and Se elements. 1-x S x Alloy structure, 0 < x < 1. Specifically, ZnSe and ZnS materials can be deposited on the quantum dot emitting layer 1 by vacuum evaporation. The total S content and total Se content in the electron transport layer 2 are the same, and the direction along the electron transport layer 2 from the side closer to the quantum dot emitting layer 1 to the side farther away from the quantum dot emitting layer 1 is such that, as the thickness of the electron transport layer 2 increases, the S content in the electron transport layer gradually decreases, and the Se content in the electron transport layer gradually increases. For example, the rate of ZnS evaporation can be... The rate of ZnSe deposition can be varied from 0 to 0. In this way, a thin ZnS layer is first formed on one side of the quantum dot light-emitting layer 1. As the evaporation rate changes, a gradient ZnSe content gradually increases while the ZnS content gradually decreases, forming in the middle. 1-x S x The alloy structure eventually forms a ZnSe thin layer, such as electron transport layer 2. As the thickness increases, the S and Se contents change in the ZnS / ZnSe ratio. 0.15 S 0.85 / ZnSe 0.5 S 0.5 / ZnSe 0.85 S 0.15 / ZnSe. For example ZnSe 0.15 S 0.85 In this layer, the rate of ZnSe deposition can be... The rate of ZnS vapor deposition can be... Of course, the evaporation rate is not limited to this.

[0050] Specifically, as shown in Figure 1, the shallowest conduction band bottom of ZnS is -3.2 eV, and the deepest valence band top is -6.8 eV, meaning the band structure range of ZnS is -3.2 eV to -6.8 eV; while the shallowest conduction band bottom of ZnSe is -3.46 eV, and the deepest valence band top is -6.36 eV, meaning the band structure range of ZnSe is -3.46 to -6.36 eV; ZnSe 1-x S x The valence band is located at -6.8 eV to -6.36 eV, and the conduction band is located at -3.2 eV to -3.46 eV, i.e., ZnSe 1-x S x The band structure is located between the band structures of ZnSe and ZnS. In this scheme, the electron transport layer 2 formed on the quantum dot luminescent layer 1 can be regarded as the initial ZnS thin layer and the intermediate ZnSe layer. 1-x S x The first ZnS layer and the final ZnSe thin layer are characterized by a wider band structure, which is beneficial for blocking holes, while the ZnSe layer has a slightly narrower band structure, which is beneficial for electron transport. Furthermore, the electron transport layer 2 consists of a ZnSe thin layer, a ZnSe layer, and a ZnSe layer. 1-x S x The structure consists of an intermediate layer and a thin ZnSe layer, with a gradient change in the band structure, which is more conducive to electron transport, thereby improving electron injection in quantum dot light-emitting devices. Furthermore, a gradient ZnSe layer is deposited using vacuum evaporation. 1-x S x The preparation of the electron transport layer replaces the traditional solution method for preparing the ZnO electron transport layer. On the one hand, the ZnS formed first can enter the gaps between quantum dots in the quantum dot light-emitting layer 1, suppressing the leakage current phenomenon of the quantum dot light-emitting device under an electric field. On the other hand, ZnSe... 1-x S x The alloy structure has better stability and fewer defects than traditional ZnO, which is beneficial for realizing quantum dot light-emitting devices with high luminous efficiency and high stability.

[0051] In some embodiments, as shown in FIG1, the thickness of the electron transport layer 2 in the quantum dot light-emitting device provided in the present disclosure is 15-40nm, such as 15nm, 20nm, 25nm, 30nm, 35nm and 40nm; preferably, the thickness of the electron transport layer 2 is 20nm.

[0052] In some embodiments, in the quantum dot light-emitting device provided in the present disclosure, the ZnS thin layer and the ZnSe thin layer can both be about 2 nm.

[0053] It should be noted that the embodiments described above use the evaporation rate of ZnS. The evaporation rate of ZnSe changes from 0 to 0. For example, but not limited to this, the initial evaporation rate of ZnS and the cutoff evaporation rate of ZnSe need to be adjusted according to the ratio of ZnSe to ZnS and the required electron transport layer thickness of the device.

[0054] In some embodiments, in the quantum dot light-emitting device provided in the present disclosure, as shown in FIG1, the electron transport layer 2 can also be made by evaporating ZnSe at a rate of [missing information]. The rate of ZnS deposition can be varied from 0 / s to 0. In this way, a ZnSe thin layer is first formed on one side of the quantum dot light-emitting layer 1. As the evaporation rate changes, a gradient ZnSe layer is formed in the middle, with the ZnSe content gradually decreasing and the ZnS content gradually increasing. 1-x S x The alloy structure is formed, and finally a ZnS thin layer is formed. Preferably, the ZnS thin layer is formed first, followed by a ZnSe thin layer.

[0055] In some embodiments, as shown in FIG2 and FIG3, in the quantum dot light-emitting device provided in the present disclosure, the electron transport layer 2 may include: a first electron transport layer 21 located on one side of the quantum dot light-emitting layer 1, and a second electron transport layer 22 located on the side of the first electron transport layer 21 opposite to the quantum dot light-emitting layer 1.

[0056] Specifically, as shown in Figure 2, the material of the first electron transport layer 21 is ZnS, which is composed of Zn and S elements, and the material of the second electron transport layer 22 is ZnSe, which is composed of Zn and Se elements. In this way, when the first electron transport layer 21 is prepared, ZnS can enter the gap between the quantum dots in the quantum dot light-emitting layer 1, suppressing the leakage current phenomenon of the quantum dot light-emitting device under an electric field. Furthermore, the first electron transport layer 21 is beneficial for blocking holes, while the second electron transport layer 22 is beneficial for electron transport. In addition, ZnS and ZnSe have better stability and fewer defects than traditional ZnO, thus facilitating the realization of quantum dot light-emitting devices with high luminous efficiency and high stability.

[0057] Specifically, as shown in Figure 3, the first electron transport layer 21 is made of ZnSe, composed of Zn and Se elements, and the second electron transport layer 22 is made of ZnS, composed of Zn and S elements. In this way, during the fabrication of the first electron transport layer 21, ZnSe can enter the gaps between the quantum dots in the quantum dot light-emitting layer 1, suppressing the leakage current phenomenon of the quantum dot light-emitting device under an electric field. Furthermore, ZnS and ZnSe have better stability and fewer defects than traditional ZnO, thus facilitating the realization of quantum dot light-emitting devices with high luminous efficiency and high stability.

[0058] In some embodiments, as shown in FIG2 and FIG3, in the quantum dot light-emitting device provided in the present disclosure, the thickness of the first electron transport layer 21 and the second electron transport layer 22 can be the same, and the sum of their thicknesses can be 15-40 nm.

[0059] In some embodiments, as shown in Figures 1-3, the materials of the quantum dot light-emitting layer 1 and the electron transport layer 2 comprise at least two identical elements. Specifically, the material of the quantum dot light-emitting layer 1 includes quantum dot materials and ZnS or ZnSe located in the gaps between the quantum dot materials. This can suppress leakage current in the quantum dot light-emitting device under an electric field.

[0060] Quantum dot materials generally include core structures, core / shell structures, and core / shell / shell structures. This embodiment uses InP / ZnSe / ZnS as an example, where the quantum dot material of the luminescent layer has a core / shell / shell structure. However, it is not limited to this; for example, quantum dot materials can also include, but are not limited to, InP, CdS, CdSe, ZnSe, ZnTeSe, PbS, CsPbCl3, CsPbBr3, CsPbI3, ZnSe, ZnSeTe, etc. In this way, ZnS or ZnSe in the electron transport layer enters the gaps between these quantum dots, effectively encapsulating a shell structure. This not only reduces leakage current but also passivates defects on the surface of the quantum dots, improving luminescence intensity. Quantum dot materials can have core / shell structures including, but not limited to, CdS / ZnS, CdSe / ZnS, InP / ZnS, PbS / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, and CsPbI3 / ZnS. They can also have core / shell / shell structures including, but not limited to, InP / ZnS / ZnSe, CdS / ZnSeS / ZnS, CdSe / ZnSeS / ZnS, ZnSe / ZnSeS / ZnS, and ZnSeTe / ZnSeS / ZnS. In this way, ZnS or ZnSe in the electron transport layer can enter the gaps between these quantum dots without altering the original core / shell or core / shell / shell structures, and can also reduce leakage current. The shapes of quantum dot materials include, but are not limited to, spherical, spherical, ellipsoidal, polyhedral, rod-shaped, cross-shaped, and ring-shaped quantum dot materials of any geometric shape.

[0061] In some embodiments, in the quantum dot light-emitting device provided in the present disclosure, as shown in Figures 1-3, the electron transport layer 2 can be a thin film structure formed by vacuum evaporation, and the root mean square (RMS) roughness of the surface of the electron transport layer 2 is 0.1-0.5 nm, such as 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, etc.

[0062] It should be noted that the electron transport layer 2 of this disclosure contains no organic components other than Zn, S and Se elements.

[0063] In some embodiments, the quantum dot light-emitting device provided in this disclosure, as shown in Figures 1-3, further includes: a hole transport layer 3 located on the side of the quantum dot light-emitting layer 1 facing away from the electron transport layer 2; a hole injection layer 4 located on the side of the hole transport layer 3 facing away from the electron transport layer 2; an anode 5 located on the side of the hole injection layer 4 facing away from the electron transport layer 2; and a cathode 6 located on the side of the electron transport layer 2 facing away from the quantum dot light-emitting layer 1. The working principle of the quantum dot light-emitting device is as follows: holes from the anode 5 and electrons from the cathode 6 are injected into the quantum dot light-emitting layer 1 respectively, and then recombine to emit light.

[0064] In some embodiments, in the quantum dot light-emitting device provided in the present disclosure, the hole transport layer can be an organic material or an inorganic material. When the hole transport layer is made of an organic material, the organic material includes, but is not limited to, polyvinylcarbazole (PVK), poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine (TFB), N,N'-diphenyl-N,N'-di(3-methylbenzene)-(1,1'-biphenyl)-4,4'-diamine (TPD), 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA), or N,N'-diphenyl-N,N'-di(1-naphthyl)-1,1'-biphenyl-4-4'-diamine (NPB). When the hole transport layer is made of an inorganic material, the inorganic material includes, but is not limited to, NiOx or VOx.

[0065] In some embodiments, the material of the hole injection layer in the quantum dot light-emitting device provided in the present disclosure includes, but is not limited to, any one of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), MoOx, NiOx, and CuOx.

[0066] Specifically, quantum dot light-emitting devices can be either upright or inverted structures. The difference lies in the order in which the film layers are fabricated. Specifically, in an upright structure, the anode, hole injection layer, hole transport layer, quantum dot light-emitting layer, electron transport layer, and cathode are formed sequentially on the substrate. In an inverted structure, the cathode, electron transport layer, quantum dot light-emitting layer, hole transport layer, hole injection layer, and anode are formed sequentially on the substrate.

[0067] Optionally, as shown in Figures 1-3, the quantum dot light-emitting device provided in this embodiment of the present disclosure has an upright structure. The quantum dot light-emitting device further includes a substrate 7 located on the side of the anode 5 facing away from the blue quantum dot light-emitting layer. The substrate 7 can be a glass substrate, a flexible substrate (such as PI), or other materials. Specifically, the substrate may include a substrate, a driving circuit located between the substrate and the anode, and a passivation layer, planarization layer, or other structures located between the driving circuit and the anode.

[0068] In some embodiments, the quantum dot light-emitting device provided in this disclosure can be a rigid substrate or a flexible substrate. The rigid substrate can be a glass substrate or a PMMA (polymethyl methacrylate) substrate, while the flexible substrate can be a PET (polyethylene terephthalate) substrate or a PI (polyimide) substrate.

[0069] Optionally, the anode can be a single-layer structure, such as ITO; the anode can also be a multi-layer structure, such as including a transparent conductive layer, a metal layer and a transparent conductive layer stacked together, wherein the material of the metal layer is including but not limited to Ag, and the material of the transparent conductive layer is including but not limited to ITO.

[0070] Optionally, the cathode material includes, but is not limited to, Al, Ag, Au, Mg, Mg / Ag alloys, etc.

[0071] Specifically, the quantum dot light-emitting device provided in this disclosure is a quantum dot light-emitting diode as an example. Of course, quantum dot light-emitting devices can also be photodetectors, photovoltaic solar cells, etc., but are not limited to these.

[0072] Optionally, the light emission type of a quantum dot light-emitting diode can be a top-emitting structure, a bottom-emitting structure, or a double-sided light-emitting structure.

[0073] Based on the same inventive concept, this disclosure provides a method for fabricating the above-mentioned quantum dot light-emitting device. Since the principle of this fabrication method in solving the problem is similar to that of the above-mentioned quantum dot light-emitting device, the implementation of the fabrication method provided in this disclosure can refer to the implementation of the above-mentioned quantum dot light-emitting device provided in this disclosure, and the repeated parts will not be described again.

[0074] In some embodiments, the method for fabricating the quantum dot light-emitting device provided in this disclosure may include:

[0075] A quantum dot luminescent layer and an electron transport layer are formed by stacking the quantum dots. The electron transport layer is made of Zn, S and Se elements.

[0076] In some embodiments, in the preparation method provided in this disclosure, the formation of the stacked quantum dot light-emitting layer and electron transport layer, as shown in FIG4, may specifically include:

[0077] S401, Forming a quantum dot light-emitting layer;

[0078] S402. On one side of the quantum dot emitting layer and along the direction away from the quantum dot emitting layer, ZnSe and ZnS are simultaneously deposited at gradient rates to form a ZnSe material. 1-x S x An electron transport layer with an alloy structure; wherein the rates of ZnSe and ZnS vapor deposition change in opposite directions, and ZnS is vapor deposition at the initial moment and ZnSe is vapor deposition at the final moment, 0 < x < 1.

[0079] Alternatively, the embodiments disclosed herein are not limited to using vapor deposition to form the material ZnSe. 1-x S x The electron transport layer of the alloy structure can also be formed using methods such as CVD (chemical vapor deposition), PVD (physical vapor deposition), magnetron sputtering, and ALD (atomic layer deposition) to create ZnSe material. 1-x S x An electron transport layer with an alloy structure.

[0080] In some embodiments, in the preparation method provided in this disclosure, the evaporation rate of ZnS can be determined by... As the gradient changes to 0, the deposition rate of ZnSe changes from a gradient of 0 to...

[0081] In some embodiments, in the preparation method provided in this disclosure, the formation of the stacked quantum dot light-emitting layer and electron transport layer, as shown in FIG5, may specifically include:

[0082] S501, Forming a quantum dot light-emitting layer;

[0083] S502. A first electron transport layer is formed on one side of the quantum dot light-emitting layer, and the material of the first electron transport layer is ZnS;

[0084] S503. A second electron transport layer is formed on the side of the first electron transport layer away from the quantum dot light-emitting layer. The material of the second electron transport layer is ZnSe.

[0085] In some embodiments, in the preparation method provided in this disclosure, the formation of the stacked quantum dot light-emitting layer and electron transport layer, as shown in FIG6, may specifically include:

[0086] S601, Forming a quantum dot light-emitting layer;

[0087] S602. A first electron transport layer is formed on one side of the quantum dot light-emitting layer, and the material of the first electron transport layer is ZnSe;

[0088] S603. A second electron transport layer is formed on the side of the first electron transport layer away from the quantum dot light-emitting layer. The material of the second electron transport layer is ZnS.

[0089] Optionally, the first and second electron transport layers can be formed by vapor deposition. Alternatively, ZnSe can be formed using methods such as CVD (chemical vapor deposition), PVD (physical vapor deposition), magnetron sputtering, or ALD (atomic layer deposition). 1-x S x An electron transport layer with an alloy structure.

[0090] To more clearly illustrate the fabrication method of the quantum dot light-emitting device provided in the embodiments of this disclosure, the fabrication method will be described in detail.

[0091] The specific steps of Example 1 are as follows:

[0092] (1) Place the glass substrate with ITO anode in deionized water, acetone and isopropanol in sequence and sonicate for 20 min each, then dry at 80℃.

[0093] (2) A hole injection material, such as PEDOT:PSS, is spin-coated onto the treated ITO glass substrate and annealed at 150°C for 20 min to form a hole injection layer.

[0094] (3) After cooling the structure obtained in step (2), transfer it to an inert glove box for spin coating of hole transport material, such as TFB, and anneal at 150°C for 20 min to form a hole transport layer.

[0095] (4) Spin-coat an InP quantum dot solution onto the cooled hole transport layer. For example, the quantum dot structure is an InP / ZnSe / ZnS core / shell / shell structure. Anneal at 80°C for 10 min to form a quantum dot luminescent layer.

[0096] (5) After cooling, the substrate with the quantum dot light-emitting layer is transferred to the evaporation machine and then... and The ZnSe and ZnS materials are co-deposited at different rates to form an alloy structure ZnSe. 1-x S x The electron transport layer of this alloy structure ZnSe 1-x S x The total thickness of the electron transport layer is 20 nm; the evaporation rate of ZnSe is not limited to... The evaporation rate of ZnS is not limited to Specifically, it depends on the ratio of ZnSe to ZnS and the required thickness of the electron transport layer;

[0097] (6) Finally, the cathode material is vapor-deposited to form the cathode, such as Mg / Ag alloy.

[0098] Example 2: It is basically the same as Example 1, except that step (5) is changed to first depositing ZnS in the evaporation machine to form the first electron transport layer, and then depositing ZnSe to form the second electron transport layer, wherein the thickness of the first electron transport layer and the second electron transport layer are 10nm respectively.

[0099] Example 3: It is basically the same as Example 1, except that step (5) is changed to first depositing ZnSe in the vapor deposition machine to form the first electron transport layer, and then depositing ZnS to form the second electron transport layer, wherein the thickness of the first electron transport layer and the second electron transport layer are 10nm respectively.

[0100] Example 4: Basically the same as Example 1, except that step (5) is changed to simultaneously depositing ZnSe and ZnS materials in a vapor deposition machine to form an electron transport layer. The deposition rates of ZnSe and ZnS are both... The thickness of the electron transport layer is 20 nm.

[0101] Example 5: Basically the same as Example 1, except that step (5) is changed to simultaneously depositing ZnSe and ZnS materials in a vapor deposition machine to form an electron transport layer. The deposition rates of ZnSe and ZnS are both... The thickness of the electron transport layer is 20 nm.

[0102] Example 6: Basically the same as Example 1, except that step (5) is changed to simultaneously depositing ZnSe and ZnS materials in a vapor deposition machine to form an electron transport layer, and the deposition rate of ZnSe is... The rate of ZnS vapor deposition is The thickness of the electron transport layer is 20 nm.

[0103] Example 7: Basically the same as Example 1, except that step (5) is changed to simultaneously depositing ZnSe and ZnS materials in a vapor deposition machine to form an electron transport layer, and the deposition rate of ZnSe is... The rate of ZnS vapor deposition is The thickness of the electron transport layer is 20 nm.

[0104] Example 8: Basically the same as Example 1, except that step (5) is changed to simultaneously depositing ZnSe and ZnS materials in a vapor deposition machine to form an electron transport layer, and the deposition rate of ZnSe is... The rate of ZnS vapor deposition is The thickness of the electron transport layer is 20 nm.

[0105] Comparative Example 1: Basically the same as Example 1, except that in step (5), ZnO material is spin-coated to form an electron transport layer with a thickness of 20 nm.

[0106] Comparative Example 2: Basically the same as Example 1, except that step (5) is changed to be used in a vapor deposition machine. A ZnSe material was deposited at a rate of 20 nm to form an electron transport layer.

[0107] Comparative Example 3: Basically the same as Example 1, except that step (5) is changed to be used in a vapor deposition machine. A ZnS material was vapor-deposited at a rate of 20 nm to form an electron transport layer.

[0108] As shown in Table 1 below, Table 1 is a performance comparison analysis table of InP QLEDs in Examples 1-8 and Comparative Examples 1-3.

[0109] Table 1

[0110] As shown in Figures 7-9, Figure 7 shows the current density-voltage-brightness curves of the quantum dot light-emitting devices of Embodiment 1 and Comparative Example 1 of this disclosure, Figure 8 shows the brightness-external quantum efficiency curves of the quantum dot light-emitting devices of Embodiment 1 and Comparative Example 1 of this disclosure, and Figure 9 shows the lifetime curves of the quantum dot light-emitting devices of Embodiment 1 and Comparative Example 1 of this disclosure.

[0111] As can be seen from Table 1 and Figures 7-9, the InP QLED device provided in the embodiments of this disclosure exhibits superior electrical performance.

[0112] Based on the same inventive concept, this disclosure also provides a display device, including the quantum dot light-emitting device described above. The principle by which this display device solves the problem is similar to that of the aforementioned quantum dot light-emitting device; therefore, the implementation of this display device can refer to the implementation of the aforementioned quantum dot light-emitting device, and repeated details will not be elaborated here. This display device can be any product or component with display function, such as a mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, or navigator. Other essential components of this display device are understood by those skilled in the art and will not be described in detail here, nor should they be construed as limiting the present invention.

[0113] This disclosure provides a quantum dot light-emitting device, its fabrication method, and a display device. Since the electron transport layer material includes Zn, S, and Se elements, and the shell structure of the quantum dot material in the quantum dot light-emitting layer is generally ZnS or ZnSe, the ZnS or ZnSe deposited at the beginning of the electron transport layer fabrication can enter the gaps between the quantum dots without altering the original structure of the quantum dots, thus preventing the introduction of new defects and suppressing leakage current. Furthermore, the electron transport material composed of Zn, S, and Se elements is beneficial for blocking holes and transporting electrons, improving electron injection in the quantum dot light-emitting device. Moreover, the electron transport material composed of Zn, S, and Se elements has better stability and fewer defects than traditional ZnO, thus facilitating the realization of quantum dot light-emitting devices with high luminous efficiency and high stability.

[0114] Although preferred embodiments of this disclosure have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this disclosure.

[0115] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this disclosure without departing from the spirit and scope of the embodiments of this disclosure. Therefore, if these modifications and variations to the embodiments of this disclosure fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include these modifications and variations.

Claims

1. A quantum dot light-emitting device, wherein, include: A quantum dot light-emitting layer, and an electron transport layer located on one side of the quantum dot light-emitting layer; The electron transport layer is made of Zn, S, and Se elements.

2. The quantum dot light-emitting device as described in claim 1, wherein, The electron transport layer is made of ZnSe, composed of Zn, S, and Se elements. 1-x S x Alloy structure, 0 < x < 1.

3. The quantum dot light-emitting device as described in claim 2, wherein, The total content of S in the electron transport layer is the same as the total content of Se.

4. The quantum dot light-emitting device according to any one of claims 1-3, wherein, Along the direction from the side of the electron transport layer near the quantum dot emitting layer to the side away from the quantum dot emitting layer, the S content in the electron transport layer gradually decreases, and the Se content in the electron transport layer gradually increases.

5. The quantum dot light-emitting device as described in claim 4, wherein, The valence band of the electron transport layer is located at -6.8 eV to -6.36 eV, and the conduction band is located at -3.2 eV to -3.46 eV.

6. The quantum dot light-emitting device as described in claim 1, wherein, The electron transport layer includes: a first electron transport layer located on one side of the quantum dot emitting layer, and a second electron transport layer located on the side of the first electron transport layer opposite to the quantum dot emitting layer; wherein, The first electron transport layer is made of ZnS, which is composed of Zn and S elements, and the second electron transport layer is made of ZnSe, which is composed of Zn and Se elements. Alternatively, the material of the first electron transport layer is ZnSe, which is composed of Zn and Se elements, and the material of the second electron transport layer is ZnS, which is composed of Zn and S elements.

7. The quantum dot light-emitting device according to any one of claims 1-6, wherein, The materials of the quantum dot luminescent layer and the electron transport layer both comprise at least two identical elements.

8. The quantum dot light-emitting device as described in claim 7, wherein, The material of the quantum dot light-emitting layer includes quantum dot materials and ZnS or ZnSe located in the gaps between the quantum dot materials.

9. The quantum dot light-emitting device as described in claim 8, wherein, The quantum dot material includes at least one of the following: InP, CdS, CdSe, ZnSe, ZnTeSe, PbS, CsPbCl3, CsPbBr3, CsPbI3, ZnSe, ZnSeTe, CdS / ZnS, CdSe / ZnS, InP / ZnS, PbS / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, CsPbI3 / ZnS, InP / Zn Se / ZnS, InP / ZnS / ZnSe, CdS / ZnSeS / ZnS, CdSe / ZnSeS / ZnS, ZnSe / ZnSeS / ZnS, ZnSeTe / ZnSeS / ZnS.

10. The quantum dot light-emitting device according to any one of claims 1-9, wherein, The electron transport layer has a thin film structure, and the root mean square roughness of the electron transport layer surface is 0.1-0.5 nm.

11. The quantum dot light-emitting device according to any one of claims 1-10, wherein, It also includes: a hole transport layer located on the side of the quantum dot light-emitting layer opposite to the electron transport layer, a hole injection layer located on the side of the hole transport layer opposite to the electron transport layer, an anode located on the side of the hole injection layer opposite to the electron transport layer, and a cathode located on the side of the electron transport layer opposite to the quantum dot light-emitting layer.

12. A display device, wherein, Including the quantum dot light-emitting device as described in any one of claims 1-11.

13. A method for fabricating a quantum dot light-emitting device, wherein, The method for preparing the quantum dot light-emitting device as described in any one of claims 1-11 includes: A quantum dot light-emitting layer and an electron transport layer are formed in a stacked configuration, wherein the electron transport layer is made of Zn, S, and Se elements.

14. The preparation method according to claim 13, wherein, The quantum dot light-emitting layer and electron transport layer that are stacked together specifically include: Form the quantum dot light-emitting layer; On one side of the quantum dot light-emitting layer and along the direction away from the quantum dot light-emitting layer, ZnSe and ZnS are simultaneously deposited at gradient rates to form a ZnSe material. 1-x S x The electron transport layer of the alloy structure; wherein the rates of ZnSe and ZnS deposition change in opposite directions, and ZnS is deposited at the initial moment and ZnSe is deposited at the final moment, 0 < x < 1.

15. The preparation method according to claim 13, wherein, The quantum dot light-emitting layer and electron transport layer that are stacked together specifically include: Form the quantum dot light-emitting layer; A first electron transport layer is formed on one side of the quantum dot light-emitting layer, and the material of the first electron transport layer is ZnS; A second electron transport layer is formed on the side of the first electron transport layer away from the quantum dot light-emitting layer, and the material of the second electron transport layer is ZnSe.

16. The preparation method according to claim 13, wherein, The quantum dot light-emitting layer and electron transport layer that are stacked together specifically include: Form the quantum dot light-emitting layer; A first electron transport layer is formed on one side of the quantum dot light-emitting layer, and the material of the first electron transport layer is ZnSe; A second electron transport layer is formed on the side of the first electron transport layer away from the quantum dot light-emitting layer, and the material of the second electron transport layer is ZnS.

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