Quantum dot light-emitting diode, display substrate and manufacturing method therefor, and display apparatus

Abstract

A quantum dot light-emitting diode, a display substrate and a manufacturing method therefor, and a display apparatus. The quantum dot light-emitting diode comprises: a first electrode (10), a second electrode (12), and an electron transport layer (20) and a quantum dot light-emitting layer (30) which are provided between the first electrode (10) and the second electrode (12), the electron transport layer (20) being located on the side of the quantum dot light-emitting layer (30) close to the first electrode (10); the electron transport layer (20) is configured to regulate the length of an optical microcavity between the first electrode (10) and the second electrode (12). The material of the electron transport layer (20) comprises patterned inorganic nanoparticles, the patterned inorganic nanoparticles being obtained by performing a photolithography process on inorganic nanoparticles having photosensitive ligands, and, before and after illumination, the photosensitive ligands exhibiting different solubilities in a developing solution.

Description

Quantum dot light-emitting diodes, display substrates, their fabrication methods, and display devices Technical Field

[0001] This article relates to, but is not limited to, the field of display technology, and in particular to a quantum dot light-emitting diode, a display substrate, a method for fabricating the same, 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.

[0004] Summary of the Invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0006] In a first aspect, embodiments of this disclosure provide a quantum dot light-emitting diode, comprising: a first electrode, a second electrode, and an electron transport layer and a quantum dot light-emitting layer disposed between the first electrode and the second electrode, wherein the electron transport layer is located on the side of the quantum dot light-emitting layer closer to the first electrode; wherein the electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode, and the material of the electron transport layer comprises patterned inorganic nanoparticles, wherein the patterned inorganic nanoparticles are obtained by photolithography of inorganic nanoparticles having photosensitive ligands, and the photosensitive ligands have different solubilities in the developing solution before and after light irradiation.

[0007] In an exemplary embodiment, the inorganic nanoparticles are made of any one or more of the following materials: tin oxide, zinc oxide, and titanium oxide.

[0008] In an exemplary embodiment, the material of the quantum dot luminescent layer includes patterned quantum dot particles, which are obtained by photolithography of quantum dot particles with photosensitive ligands. The photosensitive ligands have different solubilities in the developing solution before and after light irradiation. The photosensitive ligands of the quantum dot particles are different from those of the inorganic nanoparticles.

[0009] In an exemplary embodiment, the photosensitive ligand of the inorganic nanoparticle or the photosensitive ligand of the quantum dot particle includes a first end group located at the end of the photosensitive ligand away from the inorganic nanoparticle or the quantum dot particle. The first end group is configured to break bonds and detach under irradiation with light of a specific wavelength, thereby changing the solubility of the photosensitive ligand in the developing solution.

[0010] In an exemplary embodiment, the photosensitive ligand includes Boc aminoethanethiol.

[0011] In an exemplary embodiment, the photosensitive ligand of the inorganic nanoparticle or the photosensitive ligand of the quantum dot particle includes a second end group and a third end group. The second end group is configured to be connected to the inorganic nanoparticle or the quantum dot particle, and the third end group is located at the end away from the photosensitive ligand and is configured to undergo cross-linking under irradiation with light of a specific wavelength.

[0012] In an exemplary embodiment, the second end group includes a coordinating functional group, and the third end group includes any one of the following groups: double bond, triple bond, acrylate bond and ethylene oxide.

[0013] In an exemplary embodiment, the photosensitive ligand comprises mono[2-[(2-methyl-acryloyl)oxy]ethyl succinate.

[0014] In an exemplary embodiment, the quantum dot light-emitting layer emits red light, the thickness of the electron transport layer is greater than or equal to 50 nm and less than or equal to 80 nm, and the thickness of the electron transport layer is the distance between the side surface of the electron transport layer closest to the first electrode and the side surface furthest from the first electrode.

[0015] In an exemplary embodiment, the quantum dot light-emitting layer emits green light, the thickness of the electron transport layer is greater than or equal to 30 nm and less than or equal to 50 nm, and the thickness of the electron transport layer is the distance between the side surface of the electron transport layer closest to the first electrode and the side surface furthest from the first electrode.

[0016] In an exemplary embodiment, the quantum dot light-emitting layer emits blue light, the thickness of the electron transport layer is greater than or equal to 15 nm and less than or equal to 35 nm, and the thickness of the electron transport layer is the distance between the side surface of the electron transport layer closest to the first electrode and the side surface furthest from the first electrode.

[0017] In an exemplary embodiment, a transparent conductive layer is also included, which is located on the side of the first electrode near the electron transport layer.

[0018] Secondly, embodiments of this disclosure provide 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.

[0019] In an exemplary embodiment, the plurality of light-emitting devices include a plurality of first red light-emitting devices, a plurality of second green light-emitting devices, and a plurality of third blue light-emitting devices. The thickness of the electron transport layer of the red light-emitting device is greater than the thickness of the electron transport layer of the green light-emitting device, and the thickness of the electron transport layer of the green light-emitting device is greater than the thickness of the electron transport layer of the blue light-emitting device.

[0020] Thirdly, embodiments of this disclosure provide a method for fabricating a display substrate, comprising: forming a first electrode on a substrate; sequentially coating an inorganic nanoparticle film having photosensitive ligands and a quantum dot particle film having photosensitive ligands on the substrate; performing a photolithography process on the inorganic nanoparticle film having photosensitive ligands and the quantum dot particle film having photosensitive ligands, wherein the inorganic nanoparticles having photosensitive ligands have different solubilities in a developing solution before and after light irradiation, thus becoming patterned inorganic nanoparticles to form an electron transport layer, and the quantum dot particles having different solubilities in the developing solution before and after light irradiation, thus becoming patterned quantum dot particles to form a quantum dot emitting layer; forming a second electrode on the side of the quantum dot emitting layer away from the substrate; wherein the electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode.

[0021] In an exemplary embodiment, the photosensitive ligands of the quantum dot particles are different from those of the inorganic nanoparticles.

[0022] In an exemplary embodiment, the electron transport layer includes a first electron transport layer, a second electron transport layer, and a third electron transport layer, and the quantum dot luminescent layer includes a red quantum dot luminescent layer, a green quantum dot luminescent layer, and a blue quantum dot luminescent layer. The formation of the electron transport layer and the quantum dot luminescent layer includes: sequentially coating an inorganic nanoparticle film with photosensitive ligands and a red quantum dot particle film with photosensitive ligands on a substrate; after photolithography, the first electron transport layer and the red quantum dot luminescent layer are formed, with the red quantum dot luminescent layer located on the side of the first electron transport layer away from the substrate; and sequentially coating an inorganic nanoparticle film with photosensitive ligands and a green quantum dot particle film with photosensitive ligands on a substrate; after photolithography, the second electron transport layer and the green quantum dot luminescent layer are formed. The system comprises three layers: a green quantum dot luminescent layer located on the side of the second electron transport layer away from the substrate; an inorganic nanoparticle film with photosensitive ligands and a blue quantum dot particle film with photosensitive ligands are sequentially coated on the substrate; after photolithography, the third electron transport layer and the blue quantum dot luminescent layer are formed, with the blue quantum dot luminescent layer located on the side of the third electron transport layer away from the substrate; wherein the orthographic projections of the first, second, and third electron transport layers on the substrate do not overlap; the orthographic projections of the red, green, and blue quantum dot luminescent layers on the substrate do not overlap; the thickness of the first electron transport layer is greater than the thickness of the second electron transport layer, and the thickness of the second electron transport layer is greater than the thickness of the third electron transport layer.

[0023] In an exemplary embodiment, before forming the electron transport layer and the quantum dot light-emitting layer, the method further includes: forming a transparent conductive layer on the side of the first electrode away from the substrate, the transparent conductive layer covering the first electrode.

[0024] In an exemplary embodiment, before forming the electron transport layer and the quantum dot emitting layer, the method further includes: forming a pixel definition layer on the side of the transparent conductive layer away from the substrate, the pixel definition layer including a plurality of first pixel openings, a plurality of second pixel openings, and a plurality of third pixel openings; the first electron transport layer and the red quantum dot emitting layer are located within the range of the first pixel openings, the second electron transport layer and the green quantum dot emitting layer are located within the range of the second pixel openings, and the third electron transport layer and the blue quantum dot emitting layer are located within the range of the third pixel openings.

[0025] Fourthly, embodiments of this disclosure provide a display device including the display substrate described above.

[0026] After reading and understanding the accompanying diagrams and detailed descriptions, other aspects can be understood.

[0027] Overview of the attached figures

[0028] 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.

[0029] Figure 1 is a schematic diagram of a display device;

[0030] Figure 2 is a schematic diagram of a planar structure of a display substrate;

[0031] Figure 3 is an equivalent circuit diagram of a pixel driving circuit;

[0032] Figure 4 is a schematic cross-sectional view of a display substrate;

[0033] Figure 5 is a structural schematic diagram of a QLED provided in at least one embodiment of the present disclosure;

[0034] Figure 6 is a schematic diagram of the structure of SnO2 nanoparticles with photosensitive ligands in an exemplary embodiment;

[0035] Figure 7 is a schematic diagram of the structure of QLED in yet another exemplary embodiment;

[0036] Figure 8 shows the spectral simulation of the red QLED structure shown in Figure 7 and a comparative example;

[0037] Figure 9 shows the spectral simulation of the green QLED structure shown in Figure 7 and a comparative example;

[0038] Figure 10 shows the blue QLED structure shown in Figure 7 and a comparative spectral simulation.

[0039] Figure 11 is a cross-sectional view of the display substrate after the transparent conductive layer is formed;

[0040] Figure 12 is a cross-sectional view of the display substrate after the first electron transport layer is formed;

[0041] Figure 13 is a schematic diagram of the exposure process of the display substrate using the first mask.

[0042] Figure 14 is a cross-sectional view of the display substrate after retaining the first electron transport layer and the first quantum dot light-emitting layer located within the first pixel opening;

[0043] Figure 15 is a cross-sectional view of the display substrate after the formation of the second quantum dot light-emitting layer;

[0044] Figure 16 is a schematic diagram of the exposure process of the display substrate using a second mask.

[0045] Figure 17 is a cross-sectional view of the display substrate after retaining the second electron transport layer and the second quantum dot light-emitting layer located within the second pixel opening;

[0046] Figure 18 is a cross-sectional view of the display substrate after the formation of the third quantum dot light-emitting layer;

[0047] Figure 19 is a schematic diagram of the exposure process of the display substrate using the third mask.

[0048] Figure 20 is a cross-sectional view of the display substrate after retaining the third electron transport layer and the third quantum dot light-emitting layer located in the third pixel opening;

[0049] Figure 21 is a cross-sectional view of the display substrate after the cover layer is formed;

[0050] Figure 22 is a cross-sectional view of the display substrate after the encapsulation layer is formed;

[0051] Figure 23 is a schematic diagram of the microcavity structure of the display substrate shown in Figure 22.

[0052] Detailed Explanation

[0053] This disclosure describes several embodiments, but these descriptions are exemplary and not restrictive, and many more embodiments and implementations are possible within the scope of the embodiments described herein, which will be apparent to those skilled in the art. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with or in lieu of any other feature or element in any other embodiment.

[0054] This disclosure includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features, and elements disclosed in this disclosure may also be combined with any conventional features or elements to form a unique inventive scheme as defined by the claims. Any feature or element of any embodiment may also be combined with features or elements from other inventive schemes to form another unique inventive scheme as defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in this disclosure may be implemented individually or in any suitable combination. Therefore, the embodiments are not limited except by the limitations imposed by the appended claims and their equivalents. Furthermore, various modifications and changes may be made within the scope of the appended claims.

[0055] 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.

[0056] In the accompanying drawings, the size of one or more constituent elements, the thickness of layers, or areas are sometimes exaggerated for clarity. Furthermore, the drawings schematically illustrate ideal examples, and this disclosure is not limited to the shapes or numerical values ​​shown in the drawings.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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. Note that in this specification, the channel region refers to the region through which current primarily flows.

[0061] In this specification, the first electrode can be the drain electrode and the second electrode can be the source electrode, or vice versa. In cases where transistors with opposite polarities are used or the current direction changes during circuit operation, the functions of the "source electrode" and "drain electrode" may sometimes be interchanged. Therefore, in this specification, the "source electrode" and "drain electrode" can be interchanged, and the "source terminal" and "drain terminal" can be interchanged.

[0062] 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.

[0063] In this specification, “about” means a value that is not strictly limited and is within the allowable range of process and measurement errors.

[0064] 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°.

[0065] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0066] Figure 1 is a schematic diagram of a display device. As shown in Figure 1, 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.

[0067] Figure 2 is a schematic diagram of a planar structure of a display substrate. As shown in Figure 2, the display area of ​​the display substrate may include multiple pixel units P arranged in a matrix. At least one of the multiple 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 all 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, which is not limited herein. 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.

[0068] In some exemplary embodiments, the pixel driving circuit can be a 3T1C, 4T1C, 5T1C, 5T2C, 6T1C, or 7T1C structure. Figure 3 is an equivalent circuit diagram of a pixel driving circuit. As shown in Figure 3, 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 can be the same signal line.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] Figure 4 is a cross-sectional schematic diagram of a display substrate, illustrating the structure of three sub-pixels. As shown in Figure 4, on a plane perpendicular to the display substrate, the display substrate may include a driving circuit layer 102 disposed on a 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.

[0073] 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).

[0074] In some exemplary embodiments, the driving circuit layer 102 of each sub-pixel may include a plurality of transistors and a storage capacitor constituting a pixel driving circuit. FIG4 illustrates an example where each sub-pixel includes one driving transistor and one 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, wherein vias are formed in the second insulating layer 202, the third insulating layer 203 and the fourth insulating layer 204, and the vias expose the active layer; a source electrode and a drain electrode disposed on the fourth insulating layer 204, wherein the source electrode and the drain electrode are respectively connected to the active layer through vias; and a planarization layer 205 covering the aforementioned structure, wherein vias are formed in the planarization layer 205, and the vias expose the drain electrode. The active layer, gate electrode, source electrode and drain electrode form a driving transistor 210, and the first capacitor electrode and the second capacitor electrode form a storage capacitor 211.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] As shown in Figure 4, a display substrate where light emitted from the light-emitting device 103 exits from the substrate 101 side 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 where light emitted from the light-emitting device 103 exits from the encapsulation layer 104 side 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.

[0080] This disclosure provides a quantum dot light-emitting diode, comprising: a first electrode, a second electrode, and an electron transport layer and a quantum dot light-emitting layer disposed between the first electrode and the second electrode, wherein the electron transport layer is located on the side of the quantum dot light-emitting layer closer to the first electrode; wherein the electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode, and the material of the electron transport layer comprises patterned inorganic nanoparticles, wherein the patterned inorganic nanoparticles are obtained by photolithography of inorganic nanoparticles having photosensitive ligands, and the photosensitive ligands have different solubilities in the developing solution before and after light irradiation.

[0081] The quantum dot light-emitting diode (QLED) provided in this disclosure, by utilizing the electron transport layer to adjust the length of the optical microcavity between the first and second electrodes, helps the QLED obtain an optical microcavity of suitable length. This allows the emitted light to resonate within the optical microcavity, increasing the intensity of the emitted light and improving the internal quantum efficiency and light extraction efficiency of the QLED. Furthermore, inorganic nanoparticles with photosensitive ligands can passivate surface defects in the electron transport layer, reducing fluorescence quenching of the light emitted by the quantum dot light-emitting layer. After illumination, the photosensitive ligands can reduce the surface roughness of the electron transport layer, reducing the leakage current of the QLED and improving its performance. Here, "illumination" can refer to irradiating the photosensitive ligands with light of a specific wavelength under suitable reaction conditions.

[0082] In an exemplary embodiment, since the photosensitive ligand is located on the inorganic nanoparticles, the solubility of the photosensitive ligand in the developer will affect the solubility of the inorganic nanoparticles in the developer. The morphology of the electron transport layer can be controlled by controlling the solubility of inorganic nanoparticles at different locations in the developer.

[0083] In an exemplary embodiment, the photosensitive ligand's solubility in the developing solution decreases after light irradiation, causing the un-illuminated inorganic nanoparticles to dissolve while the irradiated inorganic nanoparticles remain insoluble in the developing solution, forming an electron transport layer. For example, the developing solution can be a solvent for an inorganic nanoparticle solution, thus effectively dissolving the inorganic nanoparticles. In this way, one or more colors of QLEDs can be formed on a single display substrate.

[0084] In an exemplary embodiment, the solubility of the photosensitive ligand in the developing solution increases after light irradiation, causing the irradiated inorganic nanoparticles to dissolve in the developing solution, while the unirradiated inorganic nanoparticles form an electron transport layer. The dissolution principle of the photosensitive ligand under light irradiation can be selected as needed, and this disclosure does not limit it.

[0085] In an exemplary embodiment, the inorganic nanoparticles can be inorganic oxide nanoparticles, such as tin oxide (SnO2), zinc oxide (ZnO2), and titanium oxide (TiO2). Compared to magnesium (Mg)-doped zinc oxide (ZnO2), materials such as tin oxide, zinc oxide, and titanium oxide have higher conductivity, higher transmittance, higher stability, and lower defect density. Using nanoparticles such as tin oxide to form the electron transport layer 20 helps improve the performance of QLEDs. Suitable inorganic nanoparticles can be selected as needed; the following description uses tin oxide as an example, but this disclosure does not limit the scope of the invention.

[0086] In an exemplary embodiment, the surface of a single inorganic nanoparticle has at least one photosensitive ligand.

[0087] Figure 5 is a schematic diagram of a QLED structure provided in at least one embodiment of this disclosure. As shown in Figure 5, the QLED provided in this embodiment includes: a first electrode 10, a second electrode 12, and an electron transport layer 20 and a quantum dot light-emitting layer 30 disposed between the first electrode 10 and the second electrode 12. The electron transport layer 20 is disposed on the side of the quantum dot light-emitting layer 30 near the first electrode 10. The material of the electron transport layer 20 includes patterned inorganic nanoparticles, which are obtained by photolithography of inorganic nanoparticles with photosensitive ligands. The photosensitive ligands have different solubilities in the developing solution before and after light exposure. The electron transport layer 20 is configured to adjust the length of the optical microcavity between the first electrode 10 and the second electrode 12. In this embodiment of the disclosure, the thickness of film layer "A" can be the distance between the surface of film layer "A" near the first electrode 10 and the surface of film layer "A" away from the first electrode 10. As shown in Figure 5, the thickness D of the electron transport layer 20 is... 20 This is the distance between the surface of the electron transport layer 20 closest to the first electrode 10 and the surface of the electron transport layer 20 furthest from the first electrode 10. In an exemplary embodiment, the quantum dot light-emitting layer 30 is configured to emit light by recombination of electrons and holes. The first electrode 10 can be a cathode, the second electrode 12 can be an anode, the anode of the QLED can be a transparent anode, and the cathode of the QLED can be a reflective cathode, so the light emitted by the QLED can be emitted through the anode; alternatively, the anode of the QLED can be a reflective anode, and the cathode of the QLED can be a transparent cathode, so the light emitted by the QLED can be emitted through the cathode; or both the anode and cathode of the QLED can be transparent electrodes, so the light emitted by the QLED can be emitted from both the anode and cathode.

[0088] In this embodiment of the disclosure, the thickness D of the electron transport layer 20 is controlled. 20 The length of the optical microcavity between the first electrode 10 and the second electrode 12 can be controlled, allowing the light emitted by the QLED to resonate within the optical microcavity, thereby enhancing the light intensity and improving the performance of the QLED. By adding photosensitive ligands to the surface of inorganic nanoparticles, surface defects of the inorganic nanoparticles are passivated, reducing the fluorescence quenching of the quantum dot emitting layer 30 by the electron transport layer 20, thus increasing the light intensity emitted by the QLED. Furthermore, the photosensitive ligands, after cross-linking, can reduce the surface roughness of the electron transport layer 20, reducing the leakage current of the QLED. The QLED provided in this embodiment has higher internal quantum efficiency and light extraction efficiency, resulting in superior performance.

[0089] In an exemplary embodiment, the photosensitive ligand of the inorganic nanoparticles may include a first end group located at the end of the photosensitive ligand away from the inorganic nanoparticles. The first end group is configured to break and detach under irradiation with light of a specific wavelength, thereby altering the solubility of the photosensitive ligand in the developing solution. Photosensitive ligands with a first end group include, for example, Boc aminoethanethiol. Normally, photosensitive ligands with Boc aminoethanethiol on their surface are soluble in the developing solution. However, under irradiation with light of a specific wavelength, the Boc group (first end group) of Boc aminoethanethiol breaks and detaches, while the aminoethanethiol remains on the surface of the photosensitive ligand. The photosensitive ligand with aminoethanethiol on its surface does not dissolve in the developing solution, thus obtaining patterned inorganic nanoparticles. Following the same principle, other photosensitive ligands with a first end group can be selected, and this disclosure is not limiting in this regard.

[0090] Formula 1 describes the structural changes of SnO2 nanoparticles (hereinafter referred to as SnO2-Boc) with Boc aminoethanethiol groups on their surface under photoacid generator (PAG) and ultraviolet light irradiation. After irradiation, SnO2-Boc undergoes ligand bond breaking, removes the Boc group, and changes its solubility, thereby obtaining patterned SnO2 nanoparticles.

[0091] In an exemplary embodiment, the photosensitive ligand for the inorganic nanoparticles may include a second end group and a third end group. The second end group is configured to be connected to the inorganic nanoparticles, and the third end group is located at the end away from the photosensitive ligand and is configured to undergo cross-linking under irradiation with light of a specific wavelength. In an exemplary embodiment, the second end group may be a coordinating functional group, such as a thiol (-SH), carboxyl (-COOH), or amino (-NH2). The third end group may be a double bond, triple bond, acrylate bond, ethylene oxide, or other groups, and this disclosure is not limited thereto. Photosensitive ligands having second and third end groups include, for example, mono[2-[(2-methyl-acryloyl)oxy]ethyl succinate (MMES). Under irradiation with light of a specific wavelength, MMES undergoes cross-linking, and the solubility of the cross-linked inorganic nanoparticles in the developing solution changes, resulting in patterned inorganic nanoparticles. Following the same principle, other photosensitive ligands having second and third end groups may be selected, and this disclosure is not limited thereto. Based on the principle of solubility change, other types of photosensitive ligands can be formed on the surface of inorganic nanoparticles in electron transport layer 20, and this disclosure does not limit this.

[0092] Formula 2 represents the structural changes that occur in SnO2 nanoparticles with MMES groups on their surface (hereinafter referred to as SnO2-MMES) under photocrosslinking agent and ultraviolet light irradiation. SnO2-MMES undergoes crosslinking after light irradiation to form a network structure. The solubility of the network structure changes, thereby obtaining patterned SnO2 nanoparticles.

[0093] Figure 6 is a schematic diagram of the structure of SnO2 nanoparticles with photosensitive ligands in an exemplary embodiment. As shown in Figure 6, the main surface of the SnO2 nanoparticles may have multiple photosensitive ligands, which may be Boc aminoethanethiol as described above, or any one of MMES.

[0094] In an exemplary embodiment, the material of the quantum dot luminescent layer 30 includes patterned quantum dot particles, which are obtained by photolithography of quantum dot particles with photosensitive ligands. The photosensitive ligands exhibit different solubilities in the developing solution before and after illumination. For example, the photosensitive ligands located on the surface of the quantum dot particles may have a first end group, or they may have a second and a third end group; this disclosure does not impose any limitations on this.

[0095] In exemplary embodiments, quantum dot materials may include: CdS, CdSe, InP, ZnSe, PbS, CsPbCl3, CsPbBr3, CsPhI3, CdS / ZnS, CdSe / ZnS, PbS / ZnS, InP / ZnS, CsPbCl3 / ZnS, CsPbBr3 / ZnS, CsPhI3 / ZnS, etc. The quantum dot particles formed by two materials may be, for example, core-shell structures. Quantum dots with suitable materials and structures can be formed as needed, and this disclosure does not limit this.

[0096] In an exemplary embodiment, at least one photosensitive ligand may be disposed on the surface of a single quantum dot particle. The photosensitive ligand disposed on the surface of the quantum dot particle in the quantum dot luminescent layer 30 may include: Boc aminoethanethiol, or mono[2-[(2-methyl-acryloyl)oxy]ethyl] succinate (MMES). The structure and reaction principle of these two photosensitive ligands can be referred to the foregoing description of SnO2 nanoparticles, and will not be repeated here.

[0097] In an exemplary embodiment, the photosensitive ligand disposed on the surface of the quantum dot particles in the quantum dot luminescent layer 30 is a different photosensitive ligand from the photosensitive ligand disposed on the surface of the inorganic nanoparticles in the electron transport layer 20. The developing solution for the quantum dot particles and the developing solution for the inorganic nanoparticles can be different; for example, the developing solution for the quantum dot particles can be a solvent for the quantum dot particle solution, thereby effectively dissolving the quantum dot particles. This disclosure does not limit this.

[0098] In an exemplary embodiment, the thickness of the electron transport layer 20 of the red QLED is greater than the thickness of the electron transport layer 20 of the green QLED, and the thickness of the electron transport layer 20 of the green QLED is greater than the thickness of the electron transport layer 20 of the blue QLED.

[0099] In an exemplary embodiment, as shown in FIG5, the quantum dot light-emitting layer 30 of the QLED can emit red light, and the thickness D of the electron transport layer 20 is... 20 It can be greater than or equal to 50 nanometers (nm) and less than or equal to 80 nm, for example, D 20 It can be approximately 67nm. In D 20 Within this thickness range, red light can generate a stronger resonance when passing through the optical microcavity, resulting in a greater light intensity for the red QLED.

[0100] In an exemplary embodiment, as shown in FIG5, the quantum dot light-emitting layer 30 of the QLED can emit green light, and the thickness D of the electron transport layer 20 is... 20 It can be greater than or equal to 30nm and less than or equal to 50nm, for example, D 20 It can be approximately 42nm. In D 20 Within this thickness range, green light can generate a stronger resonance when passing through the optical microcavity, resulting in greater light intensity from the green QLED.

[0101] In an exemplary embodiment, as shown in FIG5, the quantum dot light-emitting layer 30 of the QLED can emit blue light, and the thickness D of the electron transport layer 20 is... 20 It can be greater than or equal to 15nm and less than or equal to 35nm, for example, D 20 It can be approximately 22nm. In D 20 Within this thickness range, blue light can generate a stronger resonance when passing through the optical microcavity, resulting in a greater light output intensity for the blue QLED.

[0102] In an exemplary embodiment, as shown in FIG5, the QLED further includes a capping layer (CPL) 13 located on the side of the second electrode 12 away from the quantum dot light-emitting layer 30. The capping layer 13 helps to reduce light loss and improve the luminous efficiency, power efficiency, and product lifespan of the QLED.

[0103] In an exemplary embodiment, as shown in FIG5, the QLED further includes a hole transport layer 40 and a hole injection layer 50. The hole transport layer 40 is located on the side of the quantum dot light-emitting layer 30 near the second electrode 12, and the hole injection layer 50 is located on the side of the hole transport layer 40 near the second electrode 12.

[0104] Figure 7 is a schematic diagram of the QLED structure in another exemplary embodiment. The difference between Figure 7 and Figure 5 is that Figure 7 also includes a transparent conductive layer 11, which is located on the side of the first electrode 10 near the electron transport layer 20. The material of the transparent conductive layer can be, for example, indium tin oxide (ITO). The remaining structure can be referred to the description of Figure 5 above, and will not be repeated here.

[0105] As shown in Figure 7, the material of the first electrode 10 of the QLED can be metallic silver (Ag), and the thickness D of the first electrode 10 is... 10 It can be approximately 100 nm. The thickness D of the transparent conductive layer 11 11 The wavelength can be approximately 8nm. By depositing a transparent conductive layer 11 on the surface of metallic silver, the excellent conductivity of silver and the high light transmittance of ITO are utilized. Since QLED devices have high requirements for the photoelectric properties of electrode materials, this composite structure can effectively balance the conductivity and light transmittance of the first electrode 10. Moreover, this combination not only improves the electron injection efficiency but also well meets the needs of top-emitting QLED display substrates.

[0106] In an exemplary embodiment, the thickness D of the quantum dot light-emitting layer 30 is... 30 It can be approximately 14 nm. The thickness D of the hole transport layer 40 40 It can be approximately 25nm. The thickness D of the hole injection layer 50 50 The thickness can be approximately 27 nm. The material of the second electrode 12 can be metallic aluminum (Al), and the thickness D of the second electrode 12 is... 12 The thickness can be approximately 10 nm. By making the second electrode 12 thinner, light can be more easily emitted from the side of the second electrode 12. The thickness D of the capping layer 13... 13 It can be approximately 70nm.

[0107] In an exemplary embodiment, the quantum dot light-emitting layer 30 of the QLED structure shown in FIG7 can emit red light. When the QLED structure shown in FIG7 is a red QLED, the thickness D of the electron transport layer 20... 20 It can be approximately 67 nm. The length Dq of the optical microcavity between the first electrode 10 and the second electrode 12 is approximately 141 nm. The length Dq of the optical microcavity can be the sum of the film thicknesses from the transparent conductive layer 11 to the hole injection layer 50.

[0108] Figure 8 shows the spectral simulations of the red QLED with the structure shown in Figure 7 and the comparative example. In Figure 8, the vertical axis represents intensity, and the horizontal axis represents wavelength (nm). Curve a represents the red QLED with the structure shown in Figure 7, and curve b represents the red QLED with the comparative example. The only difference between the red QLED with the comparative example and the red QLED with the structure shown in Figure 7 is the thickness of the electron transport layer 20. In this embodiment, multiple comparative examples were set up during the experiment, and the thickness of the electron transport layer 20 was different in each comparative example. Figure 8 only shows the spectral simulation of a single comparative example. Curve a represents the size range where the length Dq of the optical microcavity is within the range that produces a strong resonance effect with red light, while curve b represents the size range where the length Dq of the optical microcavity produces a weaker resonance effect with red light. As shown in Figure 8, by setting an electron transport layer 20 of appropriate thickness in the red QLED, the red QLED can achieve a strong microcavity effect, and the intensity of the emitted light is much higher than that of the device without the electron transport layer 20. After spectral normalization of Figure 8, it was found that the full width at half maximum (FWHM) of the red emission peak decreased from 23.5 nm to 22.3 nm. This shows that the efficiency and color purity of the red QLED with an electron transport layer 20 of appropriate thickness were significantly improved.

[0109] In an exemplary embodiment, the quantum dot light-emitting layer 30 of the QLED structure shown in FIG7 can emit green light. When the QLED structure shown in FIG7 is a green QLED, the thickness D of the electron transport layer 20... 20 It can be approximately 42 nm. The length Dq of the optical microcavity between the first electrode 10 and the second electrode 12 is approximately 116 nm. The length Dq of the optical microcavity can be the sum of the film thicknesses from the transparent conductive layer 11 to the hole injection layer 50.

[0110] Figure 9 shows the spectral simulation of the green QLED with the structure shown in Figure 7 and a comparative example. In Figure 9, the vertical axis represents intensity, and the horizontal axis represents wavelength (nm). Curve c represents the green QLED with the structure shown in Figure 7, and curve d represents the green QLED of the comparative example. The only difference between the green QLED of the comparative example and the green QLED with the structure shown in Figure 7 is the thickness of the electron transport layer 20. In this embodiment, multiple comparative examples were set up during the experiment, and the thickness of the electron transport layer 20 was different in each comparative example. Figure 9 only shows the spectral simulation of a single comparative example. Curve c represents the size range where the length Dq of the optical microcavity is within the range that produces a strong resonance effect with green light, while curve d represents the length Dq of the optical microcavity where the resonance effect with green light is weaker. As shown in Figure 9, by setting an electron transport layer 20 of appropriate thickness in the green QLED, the green QLED can achieve a strong microcavity effect, and the emitted light intensity is much higher than that of devices without an electron transport layer 20. After spectral normalization of Figure 9, it was found that the full width at half maximum (FWHM) of the green emission peak decreased from 28.7 nm to 21.6 nm. This shows that the efficiency and color purity of the green QLED with an electron transport layer 20 of appropriate thickness were significantly improved.

[0111] In an exemplary embodiment, the quantum dot light-emitting layer 30 of the QLED structure shown in FIG7 can emit blue light. When the QLED structure shown in FIG7 is a blue QLED, the thickness D of the electron transport layer 20... 20 It can be approximately 22 nm. The length Dq of the optical microcavity between the first electrode 10 and the second electrode 12 is approximately 96 nm. The length Dq of the optical microcavity can be the sum of the film thicknesses from the transparent conductive layer 11 to the hole injection layer 50.

[0112] Figure 10 shows the spectral simulation of the blue QLED with the structure shown in Figure 7 and a comparative example. In Figure 10, the vertical axis represents intensity, and the horizontal axis represents wavelength (nm). Curve e represents the blue QLED with the structure shown in Figure 7, and curve f represents the blue QLED of the comparative example. The only difference between the blue QLED of the comparative example and the blue QLED with the structure shown in Figure 7 is the thickness of the electron transport layer 20. In this embodiment, multiple comparative examples were set up during the experiment, and the thickness of the electron transport layer 20 was different in each comparative example. Figure 10 only shows the spectral simulation of a single comparative example. Curve e represents the size range in which the length Dq of the optical microcavity is within the range that produces a strong resonance effect with blue light, while curve f represents the size range in which the length Dq of the optical microcavity produces a weaker resonance effect with blue light. As shown in Figure 10, by setting an electron transport layer 20 of appropriate thickness in the blue QLED, the blue QLED can achieve a strong microcavity effect, and the intensity of the emitted light is much higher than that of the device without an electron transport layer 20. After spectral normalization of Figure 10, it was found that the full width at half maximum (FWHM) of the blue emission peak decreased from 26.3 nm to 22.5 nm. This shows that the efficiency and color purity of the blue QLED with an electron transport layer 20 of appropriate thickness were significantly improved.

[0113] Based on the simulation results above, it can be seen that by adjusting the thickness of the electron transport layer 20, the microcavity lengths of the red, green, and blue quantum dot light-emitting diodes can be controlled separately, which can significantly enhance the luminous intensity of the device and narrow the emission spectrum. The required thicknesses of the electron transport layer 20 are different for the red, green, and blue quantum dot light-emitting diodes. When the display substrate includes quantum dot light-emitting diodes of all three colors, the microcavity lengths of the three colors need to be adjusted separately during the fabrication process, and color crosstalk must be avoided.

[0114] 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.

[0115] In an exemplary embodiment, the plurality of light-emitting devices include a plurality of first red light-emitting devices, a plurality of second green light-emitting devices, and a plurality of third blue light-emitting devices. The thickness of the electron transport layer of the red light-emitting device is greater than the thickness of the electron transport layer of the green light-emitting device, and the thickness of the electron transport layer of the green light-emitting device is greater than the thickness of the electron transport layer of the blue light-emitting device.

[0116] In an exemplary embodiment, one of the first electrode and the second electrode of the light-emitting device can be a transparent electrode, and the other can be a reflective electrode.

[0117] In an exemplary embodiment, the first electrode of the light-emitting device may be located on the side close to the substrate. The first electrode may be a cathode, and the display substrate may be an inverted top-emitting display substrate.

[0118] In an exemplary embodiment, a display substrate including the QLED shown in FIG7 can be formed using the following fabrication method. This display substrate can be an inverted top-emitting display substrate. The "patterning process" described in this disclosure includes, for metallic, inorganic, or transparent conductive materials, processes such as photoresist coating, mask exposure, development, etching, and photoresist stripping; for organic materials, processes such as organic material coating, mask exposure, and development. Deposition can be performed using any one or more of sputtering, evaporation, and chemical vapor deposition; coating can be performed using any one or more of spraying, spin coating, and inkjet printing; etching can be performed using any one or more of dry etching and wet etching. This disclosure does not limit the methods used. "Thin film" refers to a thin film made of a certain material on a substrate using deposition, coating, or other processes. If the "thin film" does not require a patterning process during the entire fabrication process, it can also be called a "layer." If the "thin film" requires a patterning process during the entire fabrication process, it is called a "thin film" before the patterning process and a "layer" after the patterning process.

[0119] First, a driving circuit layer 102 is formed on a substrate 101 using a patterning process. The driving circuit layer for each sub-pixel may include a driving transistor and a storage capacitor constituting a pixel driving circuit. Then, a first electrode 10 and a transparent conductive layer 11 are formed on the substrate 101 with the aforementioned structure using a patterning process. The transparent conductive layer 11 may be made of indium tin oxide. The display substrate after the transparent conductive layer 11 is formed is then sequentially cleaned with water, ethanol, and acetone, and dried with a nitrogen gun. Figure 11 is a cross-sectional view of the display substrate after the transparent conductive layer is formed. Next, a pixel definition layer (not shown) is formed on the substrate 101 with the aforementioned structure. The pixel definition layer may include multiple pixel openings that expose the surface of the transparent conductive layer 11. The multiple pixel openings may include a first pixel opening, a second pixel opening, and a third pixel opening. Different colored light-emitting devices can subsequently be formed within different pixel openings.

[0120] Subsequently, a SnO2-Boc nanoparticle film is coated on the substrate 101 on which the aforementioned structure is formed, and a first electron transport layer 21 is formed within the pixel opening. The thickness of the first electron transport layer 21 can be approximately 67 nm. Figure 12 is a cross-sectional view of the display substrate after the formation of the first electron transport layer.

[0121] Subsequently, a thin film of first quantum dot particles with MMES groups on the surface is coated on the substrate 101 forming the aforementioned structure. A first quantum dot light-emitting layer 31 is formed on the side of the first electron transport layer 21 away from the substrate 101. The display substrate is exposed and developed using a first mask, and the first electron transport layer 21 and the first quantum dot light-emitting layer 31 located in the second pixel opening and the third pixel opening are cleaned away, while the first electron transport layer 21 and the first quantum dot light-emitting layer 31 located in the first pixel opening are retained. After exposure and development, the SnO2 surface ligand of the first electron transport layer 21 becomes aminoethanethiol, and the surface ligand of the first quantum dot particles becomes cross-linked MMES. Due to the different reaction mechanisms of the photosensitive ligands, no reaction occurs between SnO2 and the first quantum dot particles. The first quantum dot light-emitting layer 31 can be a red quantum dot light-emitting layer. Figure 13 is a schematic diagram of the exposure process of the display substrate using the first mask, and Figure 14 is a cross-sectional view of the display substrate after retaining the first electron transport layer and the first quantum dot light-emitting layer located in the first pixel opening.

[0122] Subsequently, a SnO2-Boc nanoparticle film is coated on the substrate 101 forming the aforementioned structure, forming a second electron transport layer 22 within the pixel opening. The thickness of the second electron transport layer 22 can be approximately 42 nm. Next, a second quantum dot particle film with MMES groups on its surface is coated on the substrate 101 forming the aforementioned structure. A second quantum dot emitting layer 32 is formed on the side of the second electron transport layer 22 away from the substrate 101. The display substrate is exposed and developed using a second mask, cleaning away the second electron transport layer 22 and the second quantum dot emitting layer 32 located within the first and third pixel openings, while retaining the second electron transport layer 22 and the second quantum dot emitting layer 32 located within the second pixel opening. After exposure and development, the SnO2 surface ligands of the second electron transport layer 22 become aminoethanethiol, and the surface ligands of the second quantum dot particles become cross-linked MMES. Due to the different reaction mechanisms of the photosensitive ligands, no reaction occurs between SnO2 and the second quantum dot particles. The second quantum dot emitting layer 32 can be a green quantum dot emitting layer. Figure 15 is a cross-sectional view of the display substrate after the formation of the second quantum dot light-emitting layer. Figure 16 is a schematic diagram of the exposure process of the display substrate using the second mask. Figure 17 is a cross-sectional view of the display substrate after retaining the second electron transport layer and the second quantum dot light-emitting layer located in the second pixel opening.

[0123] Subsequently, a SnO2-Boc nanoparticle film is coated on the substrate 101 where the aforementioned structure is formed, and a third electron transport layer 23 is formed within the pixel opening. The thickness of the third electron transport layer 23 can be approximately 22 nm. Then, a third quantum dot particle film with MMES groups on its surface is coated on the substrate 101 where the aforementioned structure is formed. A third quantum dot emitting layer 33 is formed on the side of the third electron transport layer 23 away from the substrate 101. The display substrate is exposed and developed using a third mask, and the third electron transport layer 23 and the third quantum dot emitting layer 33 located within the first and second pixel openings are removed, while the third electron transport layer 23 and the third quantum dot emitting layer 33 located within the third pixel opening are retained. After exposure and development, the SnO2 surface ligands of the third electron transport layer 23 become aminoethanethiol, and the surface ligands of the third quantum dot particles become cross-linked MMES. Due to the different reaction mechanisms of the photosensitive ligands, no reaction occurs between SnO2 and the third quantum dot particles. The third quantum dot emitting layer 33 can be a blue quantum dot emitting layer. Figure 18 is a cross-sectional view of the display substrate after the formation of the third quantum dot light-emitting layer. Figure 19 is a schematic diagram of the exposure process of the display substrate using the third mask. Figure 20 is a cross-sectional view of the display substrate after retaining the third electron transport layer and the third quantum dot light-emitting layer located in the third pixel opening.

[0124] Subsequently, a hole transport layer 40, a hole injection layer 50, and a second electrode 12 are sequentially deposited on the substrate 101 on which the aforementioned structure is formed. The hole transport layer 40, the hole injection layer 50, and the second electrode 12 are located sequentially on the side of the pixel opening away from the substrate 101. The second electrode 12 of each sub-pixel can be connected to the drain electrode of the corresponding driving transistor through a via. The second electrode 12 can be an anode. Subsequently, a capping layer 13 is formed on the substrate 101 on which the aforementioned structure is formed. The capping layer 13 can cover the substrate 101 to encapsulate multiple light-emitting devices. Figure 21 is a cross-sectional view of the display substrate after the capping layer is formed.

[0125] Subsequently, an encapsulation layer 104 can be formed on the substrate 101 that forms the aforementioned structure to encapsulate the entire display substrate. Figure 22 is a cross-sectional view of the display substrate after the encapsulation layer is formed.

[0126] As can be seen from the above preparation process, since the corresponding electron transport layer 20 is formed before the quantum dot light-emitting layer 30, the electron transport layer 20 can act as a sacrificial layer, reducing the residual quantum dots on the display substrate and helping to improve the color gamut of the display substrate. In this embodiment, the electron transport layer material has Boc aminoethanethiol as the photosensitive ligand, and the quantum dot material has MMES as the photosensitive ligand, as an example. The thickness of each film layer of the light-emitting device can be referred to the previous description of Figure 7, and will not be repeated here. This disclosure does not limit the materials, shapes, and size parameters of other film layers of the display substrate.

[0127] In an exemplary embodiment, by setting electron transport layers of different thicknesses in light-emitting devices of different colors, and by having microcavities of different lengths in each light-emitting device of different colors, the light of the corresponding colors resonates within the corresponding microcavities, enhancing the luminescence of quantum dots in each sub-pixel and improving the display performance of the display substrate. Figure 23 is a schematic diagram of the microcavity structure of the display substrate shown in Figure 22, omitting other structures of the display substrate. As shown in Figure 23, the light emitted by the first quantum dot light-emitting layer 31, after being reflected by the first electrode 10 and the second electrode 12, can be emitted through the second electrode 12 corresponding to the first quantum dot light-emitting layer 31. The light emitted by the second quantum dot light-emitting layer 32 and the third quantum dot light-emitting layer 33 are similar to those emitted by the first quantum dot light-emitting layer 31, and will not be described again here.

[0128] This disclosure provides a method for fabricating a display substrate, comprising: forming a first electrode on a substrate; sequentially coating an inorganic nanoparticle film having photosensitive ligands and a quantum dot particle film having photosensitive ligands on the substrate; performing a photolithography process on the inorganic nanoparticle film having photosensitive ligands and the quantum dot particle film having photosensitive ligands, wherein the inorganic nanoparticles having photosensitive ligands have different solubilities in the developing solution before and after light exposure, forming patterned inorganic nanoparticles to form an electron transport layer, and the quantum dot particles having different solubilities in the developing solution before and after light exposure, forming patterned quantum dot particles to form a quantum dot emitting layer; forming a second electrode on the side of the quantum dot emitting layer away from the substrate; wherein the electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode.

[0129] In this embodiment, the length of the optical microcavity of the light-emitting device on the display substrate can be adjusted by photolithography. The preparation method is simple, low-cost, and easy to promote and use.

[0130] In an exemplary embodiment, the photosensitive ligands of the quantum dot particles are different from those of the inorganic nanoparticles.

[0131] In an exemplary embodiment, the electron transport layer includes a first electron transport layer, a second electron transport layer, and a third electron transport layer, and the quantum dot luminescent layer includes a red quantum dot luminescent layer, a green quantum dot luminescent layer, and a blue quantum dot luminescent layer. The formation of the electron transport layer and the quantum dot luminescent layer includes: sequentially coating an inorganic nanoparticle film with photosensitive ligands and a red quantum dot particle film with photosensitive ligands on a substrate; after photolithography, the first electron transport layer and the red quantum dot luminescent layer are formed, with the red quantum dot luminescent layer located on the side of the first electron transport layer away from the substrate; and sequentially coating an inorganic nanoparticle film with photosensitive ligands and a green quantum dot particle film with photosensitive ligands on a substrate; after photolithography, the second electron transport layer and the green quantum dot luminescent layer are formed. The system comprises three layers: a green quantum dot luminescent layer located on the side of the second electron transport layer away from the substrate; an inorganic nanoparticle film with photosensitive ligands and a blue quantum dot particle film with photosensitive ligands are sequentially coated on the substrate; after photolithography, the third electron transport layer and the blue quantum dot luminescent layer are formed, with the blue quantum dot luminescent layer located on the side of the third electron transport layer away from the substrate; wherein the orthographic projections of the first, second, and third electron transport layers on the substrate do not overlap; the orthographic projections of the red, green, and blue quantum dot luminescent layers on the substrate do not overlap; the thickness of the first electron transport layer is greater than the thickness of the second electron transport layer, and the thickness of the second electron transport layer is greater than the thickness of the third electron transport layer.

[0132] In an exemplary embodiment, before forming the electron transport layer and the quantum dot light-emitting layer, the method further includes: forming a transparent conductive layer on the side of the first electrode away from the substrate, the transparent conductive layer covering the first electrode.

[0133] In an exemplary embodiment, before forming the electron transport layer and the quantum dot emitting layer, the method further includes: forming a pixel definition layer on the side of the transparent conductive layer away from the substrate, the pixel definition layer including a plurality of first pixel openings, a plurality of second pixel openings, and a plurality of third pixel openings; the first electron transport layer and the red quantum dot emitting layer are located within the range of the first pixel openings, the second electron transport layer and the green quantum dot emitting layer are located within the range of the second pixel openings, and the third electron transport layer and the blue quantum dot emitting layer are located within the range of the third pixel openings.

[0134] This disclosure provides a display device, including a display substrate as described above.

[0135] 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.

[0136] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes to the form and details of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

A quantum dot light emitting diode comprising: A first electrode, a second electrode, and an electron transport layer and a quantum dot light-emitting layer disposed between the first electrode and the second electrode, wherein the electron transport layer is located on the side of the quantum dot light-emitting layer closer to the first electrode; The electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode. The material of the electron transport layer includes patterned inorganic nanoparticles. The patterned inorganic nanoparticles are obtained by photolithography of inorganic nanoparticles with photosensitive ligands. The photosensitive ligands have different solubilities in the developing solution before and after light irradiation. The quantum dot light emitting diode of claim 1, wherein, The inorganic nanoparticles are made of any one or more of the following materials: tin oxide, zinc oxide, and titanium oxide. The quantum dot light emitting diode of claim 1, wherein, The material of the quantum dot light-emitting layer includes patterned quantum dot particles, which are obtained by photolithography of quantum dot particles with photosensitive ligands. The photosensitive ligands have different solubilities in the developing solution before and after light irradiation. The photosensitive ligands of the quantum dot particles are different from those of the inorganic nanoparticles. The quantum dot light emitting diode of claim 3, wherein, The photosensitive ligand of the inorganic nanoparticle or the photosensitive ligand of the quantum dot particle includes a first end group, which is located at the end of the photosensitive ligand away from the inorganic nanoparticle or the quantum dot particle. The first end group is configured to break bonds and detach under irradiation with light of a specific wavelength, thereby changing the solubility of the photosensitive ligand in the developing solution. The quantum dot light emitting diode of claim 4, wherein, The photosensitive ligand includes Boc aminoethanethiol. The quantum dot light emitting diode of claim 3, wherein, The photosensitive ligand of the inorganic nanoparticle or the photosensitive ligand of the quantum dot particle includes a second end group and a third end group. The second end group is configured to be connected to the inorganic nanoparticle or the quantum dot particle, and the third end group is located at the end away from the photosensitive ligand and is configured to undergo cross-linking under irradiation with light of a specific wavelength. The quantum dot light emitting diode of claim 6, wherein, The second end group includes a coordinating functional group, and the third end group includes any one of the following groups: double bond, triple bond, acrylate bond and ethylene oxide. The quantum dot light emitting diode of claim 7, wherein, The photosensitive ligand includes mono[2-[(2-methyl-acryloyl)oxy]ethyl succinate. The quantum dot light emitting diode of claim 1, wherein, The quantum dot light-emitting layer emits red light, and the thickness of the electron transport layer is greater than or equal to 50 nm and less than or equal to 80 nm. The thickness of the electron transport layer is the distance between the side surface of the electron transport layer closest to the first electrode and the side surface furthest from the first electrode. The quantum dot light emitting diode of claim 1, wherein, The quantum dot light-emitting layer emits green light, and the thickness of the electron transport layer is greater than or equal to 30 nm and less than or equal to 50 nm. The thickness of the electron transport layer is the distance between the side surface of the electron transport layer closest to the first electrode and the side surface furthest from the first electrode. The quantum dot light emitting diode of claim 1, wherein, The quantum dot light-emitting layer emits blue light, and the thickness of the electron transport layer is greater than or equal to 15 nm and less than or equal to 35 nm. The thickness of the electron transport layer is the distance between the side surface of the electron transport layer closest to the first electrode and the side surface furthest from the first electrode. The quantum dot light emitting diode of claim 1, wherein, It also includes a transparent conductive layer located on the side of the first electrode near the electron transport layer. A display substrate includes a plurality of light-emitting devices, at least one of which includes a quantum dot light-emitting diode as described in any one of claims 1-12. The display substrate according to claim 13, wherein The plurality of light-emitting devices include a plurality of red light-emitting devices, a plurality of green light-emitting devices, and a plurality of blue light-emitting devices. The thickness of the electron transport layer of the red light-emitting device is greater than the thickness of the electron transport layer of the green light-emitting device, and the thickness of the electron transport layer of the green light-emitting device is greater than the thickness of the electron transport layer of the blue light-emitting device. A method for preparing a display substrate, comprising: A first electrode is formed on the substrate; An inorganic nanoparticle film with photosensitive ligands and a quantum dot particle film with photosensitive ligands are sequentially coated on the substrate; The inorganic nanoparticle film with photosensitive ligands and the quantum dot particle film with photosensitive ligands are subjected to photolithography. The inorganic nanoparticles with photosensitive ligands have different solubilities in the developing solution before and after light exposure, thus becoming patterned inorganic nanoparticles and forming an electron transport layer. The quantum dot particles with photosensitive ligands have different solubilities in the developing solution before and after light exposure, thus becoming patterned quantum dot particles and forming a quantum dot luminescent layer. A second electrode is formed on the side of the quantum dot luminescent layer away from the substrate; wherein the electron transport layer is configured to adjust the length of the optical microcavity between the first electrode and the second electrode. The method of manufacturing according to claim 15, wherein, The photosensitive ligands of the quantum dot particles are different from those of the inorganic nanoparticles. The method of manufacturing according to claim 16, wherein, The electron transport layer includes a first electron transport layer, a second electron transport layer, and a third electron transport layer; the quantum dot luminescent layer includes a red quantum dot luminescent layer, a green quantum dot luminescent layer, and a blue quantum dot luminescent layer; forming the electron transport layer and the quantum dot luminescent layer includes: An inorganic nanoparticle film with photosensitive ligands and a red quantum dot particle film with photosensitive ligands are sequentially coated on the substrate. After photolithography, the first electron transport layer and the red quantum dot luminescent layer are formed. The red quantum dot luminescent layer is located on the side of the first electron transport layer away from the substrate. An inorganic nanoparticle film with photosensitive ligands and a green quantum dot particle film with photosensitive ligands are sequentially coated on the substrate. After photolithography, a second electron transport layer and a green quantum dot luminescent layer are formed. The green quantum dot luminescent layer is located on the side of the second electron transport layer away from the substrate. An inorganic nanoparticle film with photosensitive ligands and a blue quantum dot particle film with photosensitive ligands are sequentially coated on the substrate. After photolithography, the third electron transport layer and the blue quantum dot luminescent layer are formed. The blue quantum dot luminescent layer is located on the side of the third electron transport layer away from the substrate. The first electron transport layer, the second electron transport layer and the third electron transport layer are not overlapped in orthographic projection on the substrate; the red quantum dot light-emitting layer, the green quantum dot light-emitting layer and the blue quantum dot light-emitting layer are not overlapped in orthographic projection on the substrate; the thickness of the first electron transport layer is greater than the thickness of the second electron transport layer, and the thickness of the second electron transport layer is greater than the thickness of the third electron transport layer. The method of manufacturing according to claim 17, wherein, Before the electron transport layer and the quantum dot light-emitting layer are formed, the method further comprises: forming a transparent conductive layer on the side of the first electrode away from the substrate, the transparent conductive layer covering the first electrode. The method of manufacturing according to claim 18, wherein, Before the electron transport layer and the quantum dot light-emitting layer are formed, the method further comprises: forming a pixel definition layer on the side of the transparent conductive layer away from the substrate, the pixel definition layer comprising a plurality of first pixel openings, a plurality of second pixel openings and a plurality of third pixel openings; the first electron transport layer and the red quantum dot light-emitting layer are located within the range of the first pixel openings, the second electron transport layer and the green quantum dot light-emitting layer are located within the range of the second pixel openings, and the third electron transport layer and the blue quantum dot light-emitting layer are located within the range of the third pixel openings. A display device comprising the display substrate of claim 13 or 14.

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