Quantum dot light emitting diode, display substrate and display device

Abstract

The invention discloses a quantum dot light-emitting diode, a display substrate and a display device. The quantum dot light-emitting diode comprises a first electrode, a second electrode, and a quantum dot light-emitting layer, a first electron transport layer and a second electron transport layer which are arranged between the first electrode and the second electrode, wherein the first electron transport layer and the second electron transport layer are sequentially arranged on one side, close to the second electrode, of the quantum dot light-emitting layer; wherein the first electron transport layer and the second electron transport layer are made of inorganic nanoparticles, the conduction band bottom energy level of the first electron transport layer is matched with the conduction band bottom energy level of the quantum dot light-emitting layer, and the conduction band bottom energy level of the second electron transport layer is larger than the work function of the second electrode and smaller than the conduction band bottom energy level of the first electron transport layer; the carrier mobility of the second electron transport layer is greater than that of the first electron transport layer, and the second electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode.

Description

Technical Field

[0001] This article relates to, but is not limited to, display technologies, particularly a quantum dot light-emitting diode, a display substrate, and a display device. Background Technology

[0002] Light-emitting diode (LED) displays have garnered widespread attention in the industry due to their advantages such as self-illumination, high brightness, low operating voltage, low power consumption, long lifespan, shock resistance, and stable performance. Furthermore, because LED displays do not require an additional backlight module, they are lighter, facilitating the creation of thinner and lighter displays, thus demonstrating promising market prospects.

[0003] Quantum dots (QDs) are a novel type of light-emitting material with advantages such as high light purity, high quantum efficiency, tunable color emission, and long lifespan, making them a hot research topic in new LED light-emitting materials. Quantum dot light-emitting diodes (QLEDs), using quantum dot materials as the light-emitting layer, have become a major research direction for novel display devices. Summary of the Invention

[0004] This disclosure provides a quantum dot light-emitting diode, a display substrate, and a display device.

[0005] In a first aspect, embodiments of this disclosure provide a quantum dot light-emitting diode, comprising: a first electrode, a second electrode, and a quantum dot light-emitting layer, a first electron transport layer, and a second electron transport layer disposed between the first electrode and the second electrode. The first electron transport layer and the second electron transport layer are sequentially disposed on the side of the quantum dot light-emitting layer near the second electrode. The materials of the first electron transport layer and the second electron transport layer comprise inorganic nanoparticles. The conduction band bottom energy level of the first electron transport layer matches the conduction band bottom energy level of the quantum dot light-emitting layer. The conduction band bottom energy level of the second electron transport layer is greater than the work function of the second electrode and less than the conduction band bottom energy level of the first electron transport layer. The carrier mobility of the second electron transport layer is greater than the carrier mobility of the first electron transport layer. The second electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode.

[0006] In an exemplary embodiment, the material of the second electron transport layer comprises N-type doped zinc oxide nanoparticles.

[0007] In an exemplary embodiment, the ratio of the amount of dopant element to the amount of zinc in the second electron transport layer is greater than or equal to 0.1% and less than or equal to 15%.

[0008] In an exemplary embodiment, the doping element in the second electron transport layer includes at least one of trivalent and tetravalent elements.

[0009] In an exemplary embodiment, the doping element includes one or more of the following: boron, aluminum, gallium, indium, and silicon.

[0010] In an exemplary embodiment, the conduction band bottom energy level of the first electron transport layer is matched with the conduction band bottom energy level of the quantum dot light-emitting layer, including: the difference between the conduction band bottom energy level of the first electron transport layer and the conduction band bottom energy level of the quantum dot light-emitting layer is less than or equal to 0.5 eV.

[0011] In an exemplary embodiment, the sum of the thicknesses of the first electron transport layer and the second electron transport layer is greater than or equal to 70 nm and less than or equal to 190 nm; the thickness of the first electron transport layer is the distance between the opposite side surfaces of the first electron transport layer that are close to the first electrode and away from the first electrode, and the thickness of the second electron transport layer is the distance between the opposite side surfaces of the second electron transport layer that are close to the first electrode and away from the first electrode.

[0012] In an exemplary embodiment, the thickness of the second electron transport layer is greater than or equal to 30 nm and less than or equal to 120 nm.

[0013] In an exemplary embodiment, an insertion layer is further included, which is disposed between the first electron transport layer and the second electron transport layer. The conduction band bottom energy level of the insertion layer is greater than that of the conduction band bottom energy level of the first electron transport layer, and the carrier mobility of the insertion layer is less than that of the carrier mobility of the second electron transport layer.

[0014] In an exemplary embodiment, the material of the insert layer includes any one of the following: poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl))diphenylamine)], polyvinylcarbazole, and poly[bis(4-phenyl)(4-butylphenyl)amine].

[0015] In an exemplary embodiment, a capping layer is also provided on the side of the second electrode away from the quantum dot light-emitting layer.

[0016] In an exemplary embodiment, one of the first electrode and the second electrode is a transmission electrode, and the other is a reflection electrode.

[0017] Secondly, embodiments of this disclosure provide a display substrate including a plurality of light-emitting devices, at least one of the light-emitting devices including a quantum dot light-emitting diode as described above.

[0018] In an exemplary embodiment, the plurality of light-emitting devices include a red light-emitting device, wherein the sum of the thicknesses of the first electron transport layer and the second electron transport layer of the red light-emitting device is greater than or equal to 100 nm and less than or equal to 190 nm.

[0019] In an exemplary embodiment, the thickness of the second electron transport layer of the red light-emitting device is greater than or equal to 60 nm and less than or equal to 150 nm.

[0020] In an exemplary embodiment, the plurality of light-emitting devices include green light-emitting devices, wherein the sum of the thicknesses of the first electron transport layer and the second electron transport layer of the green light-emitting device is greater than or equal to 80 nm and less than or equal to 180 nm.

[0021] In an exemplary embodiment, the thickness of the second electron transport layer of the green light-emitting device is greater than or equal to 40 nm and less than or equal to 140 nm.

[0022] In an exemplary embodiment, the plurality of light-emitting devices include blue light-emitting devices, wherein the sum of the thicknesses of the first electron transport layer and the second electron transport layer of the blue light-emitting device is greater than or equal to 70 nm and less than or equal to 170 nm.

[0023] In an exemplary embodiment, the thickness of the second electron transport layer of the blue light-emitting device is greater than or equal to 30 nm and less than or equal to 130 nm.

[0024] Thirdly, embodiments of this disclosure provide a display device, including a display substrate as described above.

[0025] The quantum dot light-emitting diode (QLED) provided in this disclosure adds a second electron transport layer with stronger conductivity to the side of the quantum dot light-emitting layer near the second electrode. The thickness of the second electron transport layer can be used to control the length of the optical microcavity between the first and second electrodes, thereby placing the optical microcavity length of the QLED within a range that enhances the wavelength of the emitted light, thus improving the light emission of the QLED. When the quantum dot light-emitting diode provided in this disclosure is applied to a display substrate, it helps to improve the front light emission of the display substrate.

[0026] Other features and advantages of this disclosure will be set forth in the following description, or may be learned by practicing this disclosure. Other advantages of this disclosure may be realized and obtained by means of the solutions described in the specification and accompanying drawings. Attached Figure Description

[0027] The accompanying drawings are used to provide an understanding of the technical solutions of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the technical solutions of this disclosure and do not constitute a limitation on the technical solutions of this disclosure.

[0028] Figure 1 This is a schematic diagram of the structure of a display device;

[0029] Figure 2 This is a schematic diagram of a planar structure of a display substrate;

[0030] Figure 3 This is an equivalent circuit diagram of a pixel driving circuit;

[0031] Figure 4 This is a schematic diagram of a cross-sectional structure of a display substrate;

[0032] Figure 5 This is a schematic diagram of the structure of a QLED provided in at least one embodiment of the present disclosure;

[0033] Figure 6 This is a schematic diagram of the energy level relationship of the QLED in Example 1;

[0034] Figure 7 This is a diagram showing the relationship between light distribution and viewing angle for a top-emitting display substrate using QLED as the light-emitting device in Example 1.

[0035] Figure 8 This is a diagram showing the relationship between light distribution and viewing angle of a top-emitting display substrate using QLED as the light-emitting device in the comparative example of Example 1. Detailed Implementation

[0036] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. The implementation can be carried out in many different forms. Those skilled in the art will readily understand that the methods and content can be transformed into other forms without departing from the spirit and scope of this disclosure. Therefore, this disclosure should not be construed as limited to the content described in the following embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.

[0037] In the accompanying drawings, the size, thickness, or area of ​​one or more components is sometimes exaggerated for clarity. Therefore, this disclosure is not necessarily limited to these dimensions, and the shape and size of one or more parts in the drawings do not reflect true proportions. Furthermore, the drawings schematically illustrate ideal examples, and this disclosure is not limited to the shapes or values ​​shown in the drawings. The scale of the drawings in this disclosure can be used as a reference in actual processes, but is not limited thereto. For example, the aspect ratio of channels, the thickness and spacing of film layers, and the width and spacing of signal lines can be adjusted according to actual needs.

[0038] The ordinal numbers such as "first," "second," and "third" used in this specification are used to avoid confusion among the constituent elements, not to limit the quantity. The term "multiple" in this disclosure refers to two or more quantities.

[0039] In this specification, for convenience, terms such as "middle," "upper," "lower," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer" are used to indicate orientation or positional relationships in conjunction with the accompanying drawings. This is solely for the purpose of facilitating the description and simplification, and does not imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this disclosure. The positional relationships of the constituent elements may be appropriately varied depending on the orientation of the constituent elements being described. Therefore, the use of terms not limited to those described in the specification may be appropriately replaced as needed.

[0040] In this specification, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection, an indirect connection via an intermediate component, or a connection within two components. Those skilled in the art will understand the meaning of these terms in this disclosure as appropriate. "Electrical connection" includes situations where constituent elements are connected together by a component having some electrical function. There are no particular limitations on the term "component having some electrical function," as long as it allows for the transmission of electrical signals between the connected constituent elements. Examples of "component having some electrical function" include not only electrodes and wiring, but also switching elements such as transistors, resistors, inductors, capacitors, and other components with one or more functions.

[0041] In this specification, a transistor is a device that includes at least three terminals: a gate electrode, a drain electrode, and a source electrode. A transistor has a channel region between the drain electrode (drain terminal, drain region, or drain) and the source electrode (source terminal, source region, or source), and current can flow through the drain electrode, the channel region, and the source electrode. In this specification, the channel region refers to the region through which current primarily flows.

[0042] In this specification, to distinguish the two terminals of a transistor other than the gate, one electrode is referred to as the first terminal and the other as the second terminal. For example, the first terminal can be the drain electrode and the second terminal can be the source electrode, or vice versa. In cases where transistors with opposite polarities are used or where the current direction changes during circuit operation, the functions of the "source electrode" and "drain electrode" are sometimes interchanged. Therefore, in this specification, the "source electrode" and "drain electrode" can be interchanged, and the "source terminal" and "drain terminal" can be interchanged.

[0043] In this specification, "parallel" refers to the state where the angle formed by two straight lines is greater than or equal to -10° and less than 10°, and therefore also includes the state where the angle is greater than or equal to -5° and less than 5°. Similarly, "perpendicular" refers to the state where the angle formed by two straight lines is greater than or equal to 80° and less than 100°, and therefore also includes the state where the angle is greater than or equal to 85° and less than 95°.

[0044] In this specification, triangles, rectangles, trapezoids, pentagons, or hexagons are not strictly defined; they can be approximate triangles, rectangles, trapezoids, pentagons, or hexagons. Small deformations due to tolerances are possible, as are chamfered corners, curved edges, and other variations.

[0045] In this specification, “about” means a value that is not strictly limited and is within the allowable range of process and measurement errors.

[0046] In this specification, "A extends along direction B" means that A may include a main part and a secondary part connected to the main part. The main part is a line, line segment, or strip-shaped body. The main part extends along direction B, and the length of the main part extending along direction B is greater than the length of the secondary part extending along other directions. In the following description, "A extends along direction B" refers to "the main part of A extends along direction B".

[0047] In this specification, "A and B are set in the same layer" means that A and B are formed simultaneously through the same patterning process during the fabrication of the display substrate.

[0048] Furthermore, in describing representative embodiments, the specification may have presented methods and / or processes as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that the method or process does not depend on the specific order of steps described herein. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Moreover, the claims relating to the method and / or process should not be limited to the steps performed in the order written, and those skilled in the art will readily understand that these orders can be varied and still remain within the spirit and scope of the embodiments disclosed herein.

[0049] QLEDs consist of an anode, a cathode, and a light-emitting layer disposed between the anode and cathode. Their light-emitting principle involves injecting holes and electrons into the light-emitting layer through the anode and cathode, respectively. When electrons and holes meet in the light-emitting layer, they recombine to generate excitons. These excitons emit light as they transition from the excited state to the ground state. QLEDs can be applied in display panels and lighting applications, among others.

[0050] Figure 1 This is a schematic diagram of the structure of a display device. Figure 1As shown, the display device may include: a scan signal driver, a data signal driver, a light emission signal driver, a display substrate, a first power supply unit, a second power supply unit, and an initial power supply unit. In some exemplary embodiments, the display substrate includes at least a plurality of scan signal lines (S(1) to S(N)), a plurality of data signal lines (D(1) to D(M)), and a plurality of light emission signal lines (EM(1) to EM(N)). The scan signal driver is configured to sequentially provide scan signals to the plurality of scan signal lines (S(1) to S(N)), the data signal driver is configured to provide data signals to the plurality of data signal lines (D(1) to D(M)), and the light emission signal driver is configured to sequentially provide light emission control signals to the plurality of light emission signal lines (EM(1) to EM(N)). In some exemplary embodiments, the plurality of scan signal lines and the plurality of light emission signal lines extend in a horizontal direction, and the plurality of data signal lines extend in a vertical direction. The display substrate includes a plurality of sub-pixels, and each sub-pixel includes a pixel driving circuit and a light emission device. The pixel driving circuit is connected to the scan signal line, the light emission control line, and the data signal line. The pixel driving circuit is configured to receive the data voltage transmitted by the data signal line and output a corresponding current to the light-emitting device under the control of the scan signal line and the light emission signal line. The light-emitting device is connected to the pixel driving circuit and is configured to emit light of a corresponding brightness in response to the current output by the pixel driving circuit. The first power supply unit, the second power supply unit, and the initial power supply unit are respectively configured to provide a first power supply voltage, a second power supply voltage, and an initial power supply voltage to the pixel driving circuit through the first power supply line, the second power supply line, and the initial signal line.

[0051] Figure 2 This is a schematic diagram of a planar structure of a display substrate. Figure 2 As shown, the display area of ​​the display substrate may include a plurality of pixel units P arranged in a matrix. At least one of the plurality of pixel units P includes a first sub-pixel P1 emitting a first color light, a second sub-pixel P2 emitting a second color light, and a third sub-pixel P3 emitting a third color light. The first sub-pixel P1, the second sub-pixel P2, and the third sub-pixel P3 each include a pixel driving circuit and a light-emitting device. In some exemplary embodiments, the pixel unit P may include a red (R) sub-pixel, a green (G) sub-pixel, and a blue (B) sub-pixel, or it may include a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white (W) sub-pixel; this disclosure is not limited thereto. In some exemplary embodiments, the shape of the sub-pixels in the pixel unit may be rectangular, rhomboid, pentagonal, or hexagonal. When the pixel unit includes three sub-pixels, the three sub-pixels may be arranged horizontally side by side, vertically side by side, or in a triangular arrangement; when the pixel unit includes four sub-pixels, the four sub-pixels may be arranged horizontally side by side, vertically side by side, or in a square arrangement. However, this disclosure is not limited thereto.

[0052] In some exemplary embodiments, the pixel driving circuit may be a 3T1C, 4T1C, 5T1C, 5T2C, 6T1C or 7T1C structure.

[0053] Figure 3 This is an equivalent circuit diagram of a pixel driving circuit. (Example) Figure 3 As shown, the pixel driving circuit may include seven switching transistors (first transistor T1 to seventh transistor T7), one storage capacitor C, and eight signal lines (data signal line DATA, first scan signal line S1, second scan signal line S2, first initial signal line INIT1, second initial signal line INIT2, first power supply line VSS, second power supply line VDD, and light emission signal line EM). The first initial signal line INIT1 and the second initial signal line INIT2 may be the same signal line.

[0054] In some exemplary embodiments, the control electrode of the first transistor T1 is connected to the second scan signal line S2, the first electrode of the first transistor T1 is connected to the first initial signal line INIT1, and the second electrode of the first transistor T1 is connected to the second node N2. The control electrode of the second transistor T2 is connected to the first scan signal line S1, the first electrode of the second transistor T2 is connected to the second node N2, and the second electrode of the second transistor T2 is connected to the third node N3. The control electrode of the third transistor T3 is connected to the second node N2, the first electrode of the third transistor T3 is connected to the first node N1, and the second electrode of the third transistor T3 is connected to the third node N3. The control electrode of the fourth transistor T4 is connected to the first scan signal line S1, the first electrode of the fourth transistor T4 is connected to the data signal line DATA, and the second electrode of the fourth transistor T4 is connected to the first node N1. The control electrode of the fifth transistor T5 is connected to the light emission signal line EM, the first electrode of the fifth transistor T5 is connected to the second power supply line VDD, and the second electrode of the fifth transistor T5 is connected to the first node N1. The control electrode of the sixth transistor T6 is connected to the light-emitting signal line EM, the first electrode of the sixth transistor T6 is connected to the third node N3, and the second electrode of the sixth transistor T6 is connected to the first electrode of the light-emitting device. The control electrode of the seventh transistor T7 is connected to the first scan signal line S1, the first electrode of the seventh transistor T7 is connected to the second initial signal line INIT2, and the second electrode of the seventh transistor T7 is connected to the first electrode of the light-emitting device. The first terminal of the storage capacitor C is connected to the second power supply line VDD, and the second terminal of the storage capacitor C is connected to the second node N2.

[0055] In some exemplary embodiments, the first transistor T1 to the seventh transistor T7 can be P-type transistors or N-type transistors. Using the same type of transistor in the pixel driving circuit can simplify the process flow, reduce the manufacturing difficulty of the display panel, and improve the product yield. In some possible implementations, the first transistor T1 to the seventh transistor T7 may include both P-type and N-type transistors.

[0056] In some exemplary embodiments, the second electrode of the light-emitting device is connected to the first power line VSS. The signal of the first power line VSS is a low-level signal, and the signal of the second power line VDD is a continuously high-level signal. The first scan signal line S1 is the scan signal line in the pixel driving circuit of this display row, and the second scan signal line S2 is the scan signal line in the pixel driving circuit of the previous display row. That is, for the nth display row, the first scan signal line S1 is S(n), and the second scan signal line S2 is S(n-1). The second scan signal line S2 of this display row is the same signal line as the first scan signal line S1 in the pixel driving circuit of the previous display row, which can reduce the signal lines of the display panel and realize a narrow bezel of the display panel.

[0057] Figure 4 This is a cross-sectional structural diagram of a display substrate, illustrating the structure of three sub-pixels. For example... Figure 4 As shown, on a plane perpendicular to the display substrate, the display substrate may include a driving circuit layer 102 disposed on the substrate 101, a light-emitting device 103 disposed on the side of the driving circuit layer 102 away from the substrate 101, and an encapsulation layer 104 disposed on the side of the light-emitting device 103 away from the substrate 101. In some possible implementations, the display substrate may include other film layers, such as spacers, etc., which are not limited herein.

[0058] In some exemplary embodiments, the substrate 101 may be a flexible substrate or a rigid substrate. The flexible substrate may include a first flexible material layer, a first inorganic material layer, a semiconductor layer, a second flexible material layer, and a second inorganic material layer stacked together. The materials of the first and second flexible material layers may be polyimide (PI), polyethylene terephthalate (PET), or surface-treated polymer soft film, etc. The materials of the first and second inorganic material layers may be silicon nitride (SiNx) or silicon oxide (SiOx), etc., to improve the substrate's resistance to water and oxygen. The material of the semiconductor layer may be amorphous silicon (a-Si).

[0059] In some exemplary embodiments, the driving circuit layer 102 of each sub-pixel may include a plurality of transistors and storage capacitors constituting a pixel driving circuit. Figure 4The illustration uses an example where each sub-pixel includes a driving transistor and a storage capacitor. In some possible implementations, the driving circuit layer 102 of each sub-pixel may include: a first insulating layer 201 disposed on a substrate; an active layer disposed on the first insulating layer; a second insulating layer 202 covering the active layer; a gate electrode and a first capacitor electrode disposed on the second insulating layer 202; a third insulating layer 203 covering the gate electrode and the first capacitor electrode; a second capacitor electrode disposed on the third insulating layer 203; a fourth insulating layer 204 covering the second capacitor electrode, with vias formed in the second insulating layer 202, the third insulating layer 203, and the fourth insulating layer 204, exposing the active layer; a source electrode and a drain electrode disposed on the fourth insulating layer 204, the source electrode and the drain electrode being connected to the active layer through vias; and a planarization layer 205 covering the aforementioned structure, with vias formed in the planarization layer 205, exposing the drain electrode. The active layer, the gate electrode, the source electrode, and the drain electrode constitute the driving transistor 210, and the first capacitor electrode and the second capacitor electrode constitute the storage capacitor 211.

[0060] In some exemplary embodiments, the light-emitting device 103 may include an anode 301, a pixel definition layer 302, a light-emitting functional layer 303, and a cathode 304. The anode 301 is disposed on the planarization layer 205 and connected to the drain electrode of the driving transistor 210 through a via formed in the planarization layer 205; the pixel definition layer 302 is disposed on the anode 301 and the planarization layer 205, and the pixel definition layer 302 is provided with a pixel opening that exposes the anode 301; the light-emitting functional layer 303 is at least partially disposed within the pixel opening and is connected to the anode 301; the cathode 304 is disposed on the light-emitting functional layer 303 and is connected to the light-emitting functional layer 303; the light-emitting functional layer 303 emits light of a corresponding color under the drive of the anode 301 and the cathode 304.

[0061] In some exemplary embodiments, the encapsulation layer 104 may include a first encapsulation layer 401, a second encapsulation layer 402, and a third encapsulation layer 403 stacked together. The first encapsulation layer 401 and the third encapsulation layer 403 may be made of inorganic materials, while the second encapsulation layer 402 may be made of organic materials. The second encapsulation layer 402 is disposed between the first encapsulation layer 401 and the third encapsulation layer 403 to ensure that external moisture cannot enter the light-emitting device 103.

[0062] In some exemplary embodiments, the light-emitting functional layer of the light-emitting device may include an emitting layer (EML) and one or more films selected from the following: a hole injection layer (HIL), a hole transport layer (HTL), a hole block layer (HBL), an electron block layer (EBL), an electron injection layer (EIL), and an electron transport layer (ETL). Driven by the voltages of the anode and cathode, the quantum dot material emits light at the required grayscale level.

[0063] In some exemplary embodiments, QLED light-emitting devices of different colors have different light-emitting layers. For example, a red light-emitting device includes a red light-emitting layer, a green light-emitting device includes a green light-emitting layer, and a blue light-emitting device includes a blue light-emitting layer. To reduce process complexity and improve yield, the hole injection layer and hole transport layer on one side of the light-emitting layer can be common layers, and the electron injection layer and electron transport layer on the other side of the light-emitting layer can also be common layers. In some exemplary embodiments, any one or more of the hole injection layer, hole transport layer, electron injection layer, and electron transport layer can be fabricated in a single process (single vapor deposition process or single inkjet printing process), but isolation is achieved through surface steps of the formed film layers or through surface treatment. For example, any one or more of the hole injection layer, hole transport layer, electron injection layer, and electron transport layer corresponding to adjacent sub-pixels can be isolated. In some exemplary embodiments, the light-emitting functional layer can be formed by vapor deposition using a fine metal mask (FMM) or an open mask, or by blade coating, spin coating, and inkjet printing processes.

[0064] Combination Figure 4 As shown, a display substrate in which light emitted from the light-emitting device 103 exits from one side of the substrate 101 is called a bottom-emitting display substrate. Because circuits and transistors are distributed on the side of the light-emitting device 103 closest to the substrate 101, the aperture ratio of the sub-pixels is low, resulting in lower brightness of the display substrate. Conversely, a display substrate in which light emitted from the light-emitting device 103 exits from the encapsulation layer 104 is called a top-emitting display substrate. The emitted light is not affected by circuits and transistors, resulting in a larger aperture ratio of the sub-pixels and higher brightness of the display substrate. Furthermore, for top-emitting display substrates, the angle of the emitted light can be controlled by utilizing the microcavity effect between the anode 301 and cathode 304 of the light-emitting device 103, enhancing the light emission of the display substrate and achieving better display performance.

[0065] This disclosure provides a quantum dot light-emitting diode, comprising: a first electrode, a second electrode, and a quantum dot light-emitting layer, a first electron transport layer, and a second electron transport layer disposed between the first electrode and the second electrode. The first electron transport layer and the second electron transport layer are sequentially disposed on the side of the quantum dot light-emitting layer near the second electrode. The materials of the first electron transport layer and the second electron transport layer include inorganic nanoparticles. The conduction band bottom energy level of the first electron transport layer matches the conduction band bottom energy level of the quantum dot light-emitting layer. The conduction band bottom energy level of the second electron transport layer is greater than the work function of the second electrode and less than the conduction band bottom energy level of the first electron transport layer. The carrier mobility of the second electron transport layer is greater than that of the first electron transport layer. The second electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode.

[0066] The quantum dot light-emitting diode (QLED) provided in this disclosure adds a second electron transport layer with higher conductivity to the side of the quantum dot light-emitting layer near the second electrode. The thickness of the second electron transport layer can be used to control the length of the optical microcavity between the first and second electrodes, thereby placing the optical microcavity length of the QLED within a range that enhances the wavelength of the emitted light, thus improving the light emission of the QLED. When the quantum dot light-emitting diode provided in this disclosure is applied to a display substrate, it helps to improve the front light emission of the display substrate.

[0067] In an exemplary embodiment, the conduction band bottom energy level of the first electron transport layer is matched with the conduction band bottom energy level of the quantum dot light-emitting layer, including: the difference between the conduction band bottom energy level of the first electron transport layer and the conduction band bottom energy level of the quantum dot light-emitting layer is less than or equal to 0.5 eV.

[0068] Figure 5 This is a schematic diagram of the structure of a QLED provided for at least one embodiment of the present disclosure. For example... Figure 5As shown, the QLED provided in this embodiment includes: a first electrode 10, a second electrode 12, and a quantum dot light-emitting layer 40, a first electron transport layer 51, and a second electron transport layer 52 disposed between the first electrode 10 and the second electrode 12. The first electron transport layer 51 and the second electron transport layer 52 are sequentially disposed on the side of the quantum dot light-emitting layer 40 near the second electrode 12. The materials of the first electron transport layer 51 and the second electron transport layer 52 include inorganic nanoparticles. The conduction band bottom energy level (LUMO level) of the first electron transport layer 51 matches the conduction band bottom energy level of the quantum dot light-emitting layer 40. The conduction band bottom energy level of the second electron transport layer 52 is greater than the work function of the second electrode 12 and less than the conduction band bottom energy level of the first electron transport layer 51. The second electron transport layer 52 is configured to adjust the length of the optical microcavity between the first electrode and the second electrode. In an exemplary embodiment, the quantum dot light-emitting layer 40 is configured to cause electrons and holes to recombine and emit light. The first electrode 10 can be an anode, and the second electrode 12 can be a cathode. The anode of the QLED can be a transmission anode, and the cathode of the QLED can be a reflection cathode. The light emitted by the QLED can be emitted through the anode. Alternatively, the anode of the QLED can be a reflection anode, and the cathode of the QLED can be a transmission cathode. The light emitted by the QLED can be emitted through the cathode. Alternatively, both the anode and cathode of the QLED can be transmission electrodes, and the light emitted by the QLED can be emitted from both the anode and the cathode.

[0069] In an exemplary embodiment, the energy level of the first electron transport layer 51 material can be matched with the energy level of the quantum dot light-emitting layer 40. The second electron transport layer 52 can be made of a highly conductive material. The length of the optical microcavity between the first electrode 10 and the second electrode 12 can be adjusted by controlling the thickness of the second electron transport layer 52, thereby ensuring that the length of the optical microcavity of the QLED is within the range that enhances the wavelength of the emitted light. This allows for matching the thicknesses of each functional layer under optimal electrical performance, effectively coordinating the optical and electrical performance of the QLED, and contributing to improving the light output and operating performance of the QLED. In this embodiment, by controlling the thickness of the second electron transport layer 52, the length of the optical microcavity can meet the cavity length of a first-order microcavity, and can even reach the length of a second-order microcavity. In this embodiment, the thickness of film layer "A" can be the distance between the surface of film layer "A" closest to the first electrode 10 and the surface of film layer "A" furthest from the first electrode 10, such as... Figure 5 As shown, the thickness of the second electron transport layer 52 can be the distance D between the surface of the second electron transport layer 52 closest to the first electrode 10 and the surface of the second electron transport layer 52 furthest from the first electrode 10. 52 .

[0070] In an exemplary embodiment, the conduction band bottom energy level of the first electron transport layer 51 can be greater than or equal to -4.5 electron volts (eV) and less than or equal to -3 eV.

[0071] In an exemplary embodiment, the carrier mobility of the first electron transport layer 51 can be greater than or equal to 1*102 -4 square centimeters per second (cm) 2 / V*s) and less than or equal to 1*10 -2 cm 2 / V*s.

[0072] In an exemplary embodiment, the material of the first electron transport layer 51 comprises magnesium (Mg)-doped zinc oxide (ZnO) nanoparticles.

[0073] In an exemplary embodiment, the molar ratio of Mg in the first electron transport layer 51 can be greater than or equal to 5% and less than or equal to 15%. The molar ratio of Mg in the first electron transport layer 51 can be the ratio of the amount of Mg to the amount of Zn in the first electron transport layer 51.

[0074] In an exemplary embodiment, the sum of the thicknesses of the first electron transport layer and the second electron transport layer is greater than or equal to 70 nm and less than or equal to 190 nm.

[0075] In an exemplary embodiment, the thickness of the first electron transport layer 51 may be greater than or equal to 40 nm and less than or equal to 70 nm.

[0076] In an exemplary embodiment, the conduction band bottom energy level of the second electron transport layer 52 can be greater than or equal to -4.5 eV and less than or equal to -3.1 eV.

[0077] In an exemplary embodiment, the carrier mobility of the second electron transport layer 52 can be greater than or equal to 1*102 - 4 cm 2 / V*s and less than or equal to 1*10 -2 cm 2 / V*s. The second electron transport layer 52 has a higher carrier mobility and stronger conductivity, which helps to flexibly adjust the thickness of the second electron transport layer 52.

[0078] In an exemplary embodiment, the material of the second electron transport layer 52 comprises N-type doped ZnO nanoparticles. In this embodiment, the particles of the dopant element are embedded in the lattice of the ZnO nanoparticles, forming a new material. This doping helps to improve the conductivity of the ZnO nanoparticles themselves.

[0079] In an exemplary embodiment, the doping elements of the second electron transport layer 52 may include trivalent elements, such as boron (B), aluminum (Al), gallium (Ga), indium (In), etc., and may also include tetravalent elements, such as silicon (Si), etc. This disclosure does not limit the doping elements.

[0080] In an exemplary embodiment, the molar ratio of dopant elements in the second electron transport layer 52 can be greater than or equal to 0.1% and less than or equal to 15%. In this embodiment, the molar ratio of dopant elements in the second electron transport layer 52 can be the ratio of the amount of dopant elements in the second electron transport layer 52 to the amount of Zn.

[0081] In an exemplary embodiment, the thickness of the second electron transport layer 52 may be greater than or equal to 30 nm and less than or equal to 120 nm.

[0082] In an exemplary implementation, such as Figure 5 As shown, the QLED also includes an insertion layer 60 disposed between the first electron transport layer 51 and the second electron transport layer 52. The conduction band bottom energy level of the insertion layer 60 is higher than that of the first electron transport layer 51, and the carrier mobility of the insertion layer 60 is lower than that of the second electron transport layer 52. By providing the insertion layer 60, the second electron transport layer 52 can be prevented from dissolving with the first electron transport layer 51 during the fabrication process, thus protecting the first electron transport layer 51.

[0083] In an exemplary embodiment, the carrier mobility of the insertion layer 60 can be less than 1*10. -2 cm 2 / V*s. The insertion layer 60 can act as a tunneling layer for electrons, controlling the magnitude of the injected electron current and promoting the lateral expansion of the current.

[0084] In an exemplary embodiment, the thickness of the insertion layer 60 may be greater than or equal to 0.1 nm and less than or equal to 5 nm.

[0085] In an exemplary embodiment, the material of the insertion layer 60 can be an organic material. For example, the insertion layer 60 can be a thin film formed of an organic polymer. The insertion layer 60 made of this material can be prepared by solution method, which is simple and applicable to devices with different structures.

[0086] In an exemplary embodiment, the material of the insert layer 60 may include any of the following: poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl))diphenylamine)], polyvinylcarbazole and poly[bis(4-phenyl)(4-butylphenyl)amine].

[0087] In an exemplary implementation, such as Figure 5 As shown, the QLED also includes a capping layer (CPL) 13 disposed on the side of the second electrode 12 away from the quantum dot light-emitting layer 40. The capping layer 13 helps to reduce light loss and improve the light efficiency, power efficiency and product life of the QLED.

[0088] In an exemplary implementation, such as Figure 5 As shown, the QLED also includes a hole injection layer 20 and a hole transport layer 30 disposed on the side of the quantum dot light-emitting layer 40 near the first electrode 10, with the hole injection layer 20 located on the side of the hole transport layer 30 near the first electrode 10.

[0089] In an exemplary implementation, when... Figure 5 The QLED shown is applied to Figure 4 In the case of the display substrate shown, the anode of the QLED can face the substrate 101, and the cathode of the QLED is located on the side away from the substrate 101. This structure can be called an upright structure. In other embodiments, the cathode of the QLED can face the substrate 101, and the anode of the QLED is located on the side away from the substrate 101. This structure can be called an inverted structure. The QLED provided in the embodiments of this disclosure can be used in both upright and inverted structures. For example, the above-mentioned organic material insertion layer 60 can be successfully formed by solution method in both upright and inverted structures, and this disclosure does not limit this.

[0090] The QLED provided in this disclosure will be described below with reference to several specific embodiments.

[0091] Example 1

[0092] In an exemplary embodiment, the anode of the QLED can be indium tin oxide (ITO), the hole injection layer 20 can have a thickness of approximately 30 nm, the hole transport layer 30 can have a thickness of approximately 25 nm, the quantum dot light-emitting layer 40 can emit green light, the thickness of the quantum dot light-emitting layer 40 can be approximately 20 nm, the material of the first electron transport layer 51 can be Mg-doped ZnO, the molar ratio of Mg is approximately 10%, the thickness of the first electron transport layer 51 is approximately 60 nm, the material of the insertion layer 60 can be poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl))diphenylamine)](TFB), the thickness of the insertion layer 60 is approximately 1 nm, the material of the second electron transport layer 52 can be Al-doped ZnO, the molar ratio of Al is approximately 5%, the thickness of the second electron transport layer 52 is approximately 60 nm, the material of the second electrode 12 can be metal, the thickness of the second electrode 12 is approximately 10 nm, and the thickness of the capping layer 13 is approximately 60 nm.

[0093] In the exemplary embodiments, the hole injection layer 20, hole transport layer 30, quantum dot light-emitting layer 40, first electron transport layer 51, insertion layer 60 and second electron transport layer 52 in this embodiment can all be prepared by spin coating, blade coating, inkjet printing and other methods, and this disclosure does not limit them.

[0094] Figure 6 This is a schematic diagram of the energy level relationship of the QLED in Example 1, illustrating the Fermi level E of the first electrode 10. F10 The Fermi level E of the second electrode 12 F12 And the positional relationship between the conduction band bottom energy level and the valence band top energy level (HOMO level) of other films located between the first electrode 10 and the second electrode 12. Figure 6 As shown, the conduction band bottom energy level LUMO of the first electron transport layer 51 51 LUMO with the conduction band bottom level of quantum dot emitting layer 40 40 Matching the LUMO of the conduction band bottom level of the second electron transport layer 52 52 The conduction band bottom energy level LUMO greater than or equal to that of the first electron transport layer 51 51 And less than or equal to the Fermi level E of the second electrode 12 F12 The conduction band bottom level LUMO of the insertion layer 60 60 The conduction band bottom energy level LUMO is greater than that of the first electron transport layer 51. 51 .

[0095] Figure 7 This diagram illustrates the relationship between light distribution and viewing angle in a top-emitting display substrate using QLED as the light-emitting device, as shown in Example 1. Figure 7 As shown, the vertical axis I represents light intensity, the horizontal axis represents the light-emitting surface of the display substrate, and the radially distributed lines represent different viewing angles facing the light-emitting surface of the display substrate. Points located on different viewing angle lines represent the light intensity I at that viewing angle. The solid circles connecting the points on different viewing angle lines depict the light distribution facing the display substrate. In the top-emitting display substrate using QLED as the light-emitting device in Embodiment 1, the light emitted by the display substrate is concentrated in the direction directly facing the screen. The light intensity in this direction is relatively high, which is convenient for users to view and helps to save power consumption of the display substrate.

[0096] Comparative Example 1

[0097] In the exemplary embodiment, the difference between this comparative example and Embodiment 1 is that the insertion layer 60 and the second electron transport layer 52 are not provided. The rest of the structure and parameter settings are the same as those in Embodiment 1, and will not be described again here.

[0098] Figure 8 This is a diagram showing the relationship between light distribution and viewing angle in a top-emitting display substrate using QLED as the light-emitting device in the comparative example of Example 1. Figure 8 Display substrate and Figure 7 The only difference between the display substrates used is the type of QLED employed. For example... Figure 8As shown, without the insertion layer 60 and the second electron transport layer 52, the lateral light emission of the display substrate is significantly enhanced, which is detrimental to the power consumption of the display substrate and results in a poor user experience. (Comparison) Figure 7 and Figure 8 It can be seen that by setting the insertion layer 60 and the second electron transport layer 52, the length of the optical microcavity can be adjusted, thereby adjusting the light emission angle and enhancing the light emission, thus improving the display effect of the display substrate.

[0099] Example 2

[0100] In the exemplary embodiment, the difference between Embodiment 2 and Embodiment 1 is that the material of the insertion layer 60 is different, while the materials and parameters of the remaining structures are the same as those in Embodiment 1, and will not be repeated here.

[0101] In an exemplary embodiment, the material of the insert layer 60 in this embodiment can be polyvinylcarbazole (PVK), and the thickness of the insert layer 60 can be set as needed. This disclosure does not limit this.

[0102] Example 3

[0103] In the exemplary embodiment, the difference between Embodiment 3 and Embodiment 1 is that the material of the insertion layer 60 is different, while the materials and parameters of the remaining structures are the same as those in Embodiment 1, and will not be repeated here.

[0104] In an exemplary embodiment, the material of the insert layer 60 in this embodiment can be poly[bis(4-phenyl)(4-butylphenyl)amine] (Poly-TPD), and the thickness of the insert layer 60 can be set as needed. This disclosure does not limit this.

[0105] Example 4

[0106] In the exemplary embodiment, the difference between Embodiment 4 and Embodiment 1 is that the material of the second electron transport layer 52 is different, while the materials and parameters of the remaining structures are the same as those in Embodiment 1, and will not be repeated here.

[0107] In an exemplary embodiment, the material of the second electron transport layer 52 in this embodiment can be Ga-doped ZnO, and the thickness of the second electron transport layer 52 can be set as needed. This disclosure does not limit this.

[0108] Example 5

[0109] In the exemplary embodiments, the difference between Embodiment 5 and Embodiment 4 is that the quantum dot light-emitting layer 40 emits red light, while the materials and parameters of the remaining structures are the same as those in Embodiment 4, and will not be repeated here.

[0110] Example 6

[0111] In the exemplary embodiments, the difference between Embodiment 6 and Embodiment 4 is that the quantum dot light-emitting layer emits 40 blue lights, while the materials and parameters of the remaining structures are the same as those in Embodiment 4, and will not be repeated here.

[0112] This disclosure provides a display substrate including a plurality of light-emitting devices, at least one of which includes a quantum dot light-emitting diode as described above.

[0113] In an exemplary embodiment, the plurality of light-emitting devices include a red light-emitting device, wherein the sum of the thicknesses of the first electron transport layer and the second electron transport layer of the red light-emitting device is greater than or equal to 100 nm and less than or equal to 190 nm.

[0114] In an exemplary embodiment, the thickness of the second electron transport layer of the red light-emitting device is greater than or equal to 60 nm and less than or equal to 150 nm. By setting the sum of the thicknesses of the first and second electron transport layers of the red light-emitting device, and the thickness of the second electron transport layer of the red light-emitting device, the optical microcavity of the red light-emitting device can generate a strong resonance with the red light, thereby improving the light emission intensity of the red light-emitting device.

[0115] In an exemplary embodiment, the plurality of light-emitting devices include green light-emitting devices, wherein the sum of the thicknesses of the first electron transport layer and the second electron transport layer of the green light-emitting device is greater than or equal to 80 nm and less than or equal to 180 nm.

[0116] In an exemplary embodiment, the thickness of the second electron transport layer of the green light-emitting device is greater than or equal to 40 nm and less than or equal to 140 nm. By setting the sum of the thicknesses of the first and second electron transport layers of the green light-emitting device, and the thickness of the second electron transport layer of the green light-emitting device, the optical microcavity of the green light-emitting device can generate a strong resonance with the green light, thereby improving the light emission intensity of the green light-emitting device.

[0117] In an exemplary embodiment, the plurality of light-emitting devices include blue light-emitting devices, wherein the sum of the thicknesses of the first electron transport layer and the second electron transport layer of the blue light-emitting device is greater than or equal to 70 nm and less than or equal to 170 nm.

[0118] In an exemplary embodiment, the thickness of the second electron transport layer of the blue light-emitting device is greater than or equal to 30 nm and less than or equal to 130 nm. By setting the sum of the thicknesses of the first and second electron transport layers of the blue light-emitting device, and the thickness of the second electron transport layer of the blue light-emitting device, the optical microcavity of the blue light-emitting device can generate a strong resonance with the blue light, thereby improving the light emission intensity of the blue light-emitting device.

[0119] This disclosure provides a display device, including a display substrate as described above.

[0120] The display device provided in this disclosure can be any product or component with display function, such as a QLED display, mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, or navigator. This disclosure is not limited to this.

[0121] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A quantum dot light-emitting diode, characterized in that, Comprising: a first electrode, a second electrode, and a quantum dot light emitting layer, a first electron transport layer, and a second electron transport layer disposed between the first electrode and the second electrode, the first electron transport layer and the second electron transport layer being sequentially disposed on a side of the quantum dot light emitting layer close to the second electrode; wherein a material of the first electron transport layer and the second electron transport layer comprises inorganic nanoparticles, a conduction band minimum energy level of the first electron transport layer matches a conduction band minimum energy level of the quantum dot light emitting layer, a conduction band minimum energy level of the second electron transport layer is greater than a work function of the second electrode and less than the conduction band minimum energy level of the first electron transport layer; a carrier mobility of the second electron transport layer is greater than a carrier mobility of the first electron transport layer, and the second electron transport layer is configured to adjust a length of an optical microcavity between the first electrode and the second electrode.

2. The quantum dot light emitting diode of claim 1, wherein, The material of the second electron transport layer comprises N-type doped zinc oxide nanoparticles.

3. The quantum dot light emitting diode of claim 2, wherein, A ratio of a substance amount of a doping element to a substance amount of zinc in the second electron transport layer is greater than or equal to 0.1% and less than or equal to 15%.

4. The quantum dot light emitting diode of claim 2, wherein, The doping element in the second electron transport layer comprises at least one of a trivalent element and a tetravalent element.

5. The quantum dot light emitting diode of claim 4, wherein, The doping element comprises one or more of boron, aluminum, gallium, indium, and silicon.

6. The quantum dot light emitting diode of claim 1, wherein, The conduction band minimum energy level of the first electron transport layer matches the conduction band minimum energy level of the quantum dot light emitting layer, comprising: A difference between the conduction band minimum energy level of the first electron transport layer and the conduction band minimum energy level of the quantum dot light emitting layer is less than or equal to 0.5 eV.

7. The quantum dot light emitting diode of claim 1, wherein, A sum of thicknesses of the first electron transport layer and the second electron transport layer is greater than or equal to 70 nm and less than or equal to 190 nm; a thickness of the first electron transport layer is a distance between opposite side surfaces of the first electron transport layer close to the first electrode and away from the first electrode, and a thickness of the second electron transport layer is a distance between opposite side surfaces of the second electron transport layer close to the first electrode and away from the first electrode.

8. The quantum dot light emitting diode of claim 7, wherein, The thickness of the second electron transport layer is greater than or equal to 30 nm and less than or equal to 120 nm.

9. The quantum dot light emitting diode of claim 1, wherein, Further comprising an interposition layer disposed between the first electron transport layer and the second electron transport layer, a conduction band minimum energy level of the interposition layer is greater than a conduction band minimum energy level of the first electron transport layer, and a carrier mobility of the interposition layer is less than a carrier mobility of the second electron transport layer.

10. The quantum dot light emitting diode of claim 9, wherein, A material of the interposition layer comprises any one of poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butyphenyl))diphenylamine)], polyvinylcarbazole, and poly[bis(4-phenyl)(4-butylphenyl)amine].

11. The quantum dot light emitting diode of claim 1, wherein, Further comprising a cover layer disposed on a side of the second electrode away from the quantum dot light emitting layer.

12. The quantum dot light emitting diode of claim 1, wherein, One of the first electrode and the second electrode is a transmissive electrode, and the other is a reflective electrode.

13. A display substrate, comprising: Comprising a plurality of light emitting devices, at least one of the light emitting devices comprising the quantum dot light emitting diode of any one of claims 1-12. 14.The display substrate of claim 13, wherein, The plurality of light emitting devices includes a red light emitting device, a sum of thicknesses of the first electron transport layer and the second electron transport layer of the red light emitting device is greater than or equal to 100 nm and less than or equal to 190 nm. 15.The display substrate of claim 14, wherein, The thickness of the second electron transport layer of the red light emitting device is greater than or equal to 60 nm and less than or equal to 150 nm. 16.The display substrate of claim 13, wherein, The plurality of light emitting devices includes a green light emitting device, a sum of thicknesses of the first electron transport layer and the second electron transport layer of the green light emitting device is greater than or equal to 80 nm and less than or equal to 180 nm. 17.The display substrate of claim 16, wherein, The thickness of the second electron transport layer of the green light emitting device is greater than or equal to 40 nm and less than or equal to 140 nm. 18.The display substrate of claim 13, wherein, The plurality of light emitting devices includes a blue light emitting device, a sum of thicknesses of the first electron transport layer and the second electron transport layer of the blue light emitting device is greater than or equal to 70 nm and less than or equal to 170 nm.

19. The display substrate of claim 18, wherein, The thickness of the second electron transport layer of the blue light emitting device is greater than or equal to 30 nm and less than or equal to 130 nm.

20. A display device comprising: The display substrate includes the display substrate according to any one of claims 13-19.

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