Display substrate and preparation method therefor, and display apparatus

Abstract

A display substrate and a preparation method therefor, and a display apparatus. The display substrate comprises at least one sub-pixel, the at least one sub-pixel comprising a first electrode (11), a light-emitting functional layer (12), and a second electrode (13) that are sequentially stacked in the direction away from a base, wherein the light-emitting functional layer (12) comprises at least one light-emitting unit, the at least one light-emitting unit comprising a light-emitting layer, the light-emitting layer comprising a first light-emitting sub-layer (51) and a second light-emitting sub-layer (52) that are sequentially stacked in the direction away from the base, the first light-emitting sub-layer (51) and the second light-emitting sub-layer (52) being in contact with each other, and the exciton recombination center of the light-emitting layer being located at the contact interface between the first light-emitting sub-layer (51) and the second light-emitting sub-layer (52), or being located in the second light-emitting sub-layer (52).

Description

Display substrate, preparation method thereof and display device

[0001] The present application claims priority to the Chinese patent application No. 202411018485.7, filed on July 26, 2024, and entitled "Display substrate, preparation method thereof and display device", the content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of display, in particular to a display substrate, a preparation method thereof and a display device. BACKGROUND

[0003] Micro Organic Light-Emitting Diode (Micro-OLED) is a micro display developed in recent years, and silicon-based OLED is one of them. Silicon-based OLED not only can realize active addressing of pixels, but also can realize preparation of pixel driving circuit structure on silicon-based substrate, which is beneficial to reduce system volume and realize light weight. Silicon-based OLED is prepared by mature Complementary Metal Oxide Semiconductor (CMOS) integrated circuit process, has the advantages of small volume, high resolution (Pixels Per Inch, PPI), high refresh rate, etc., and is widely used in Virtual Reality (VR) or Augmented Reality (AR) near-eye display field. SUMMARY

[0004] The following is a summary of the subject matter of the detailed description herein. This summary is not intended to limit the scope of the claims.

[0005] In one aspect, the present disclosure provides a display substrate, comprising at least one sub-pixel, the at least one sub-pixel comprising a first electrode, a light-emitting functional layer and a second electrode which are sequentially stacked along a direction away from a substrate; the light-emitting functional layer comprising at least one light-emitting unit, the at least one light-emitting unit comprising a light-emitting layer, the light-emitting layer comprising a first sub-light-emitting layer and a second sub-light-emitting layer which are sequentially stacked along a direction away from the substrate, the first sub-light-emitting layer and the second sub-light-emitting layer contacting each other, and an exciton recombination center of the light-emitting layer being located at an interface between the first sub-light-emitting layer and the second sub-light-emitting layer, or being located in the second sub-light-emitting layer.

[0006] In an exemplary embodiment, the thickness of the first sub-light-emitting layer is less than the thickness of the second sub-light-emitting layer.

[0007] In an example embodiment, the thickness of the second sub-light-emitting layer is 50 angstroms to 370 angstroms greater than the thickness of the first sub-light-emitting layer.

[0008] In an example embodiment, the thickness of the first sub-light-emitting layer is 30 angstroms to 150 angstroms.

[0009] In an example embodiment, the thickness of the second sub-light-emitting layer is 200 angstroms to 400 angstroms.

[0010] In an example embodiment, the first sub-light-emitting layer includes a first host material and a first guest material, the second sub-light-emitting layer includes a second host material and a second guest material, and the first host material and the second host material are the same.

[0011] In an example embodiment, the first host material and the second host material each have a triplet energy level greater than the triplet energy level of the second guest material.

[0012] In an example embodiment, the first host material includes a first P-type semiconductor material and a first N-type semiconductor material, the second host material includes a second P-type semiconductor material and a second N-type semiconductor material, the first P-type semiconductor material is the same as the second P-type semiconductor material, and the first N-type semiconductor material is the same as the second N-type semiconductor material.

[0013] In an example embodiment, the mass ratio of the first P-type semiconductor material to the first N-type semiconductor material is 1 to 3, and the mass ratio of the second P-type semiconductor material to the second N-type semiconductor material is 0.5 to 1.5.

[0014] In an example embodiment, the first sub-light-emitting layer is a red light-emitting layer, and the second sub-light-emitting layer is a green light-emitting layer.

[0015] In an example embodiment, the light-emitting functional layer includes a first light-emitting unit and a second light-emitting unit stacked in sequence in a direction away from the substrate, and a charge generation layer disposed between the first light-emitting unit and the second light-emitting unit, the first light-emitting unit includes a first light-emitting layer, the first light-emitting layer emits yellow light, the first light-emitting layer includes a first sub-light-emitting layer and a second sub-light-emitting layer stacked in sequence in a direction away from the substrate, the first sub-light-emitting layer is a red light-emitting layer, the second sub-light-emitting layer is a green light-emitting layer, the first sub-light-emitting layer and the second sub-light-emitting layer are in contact with each other, and an exciton recombination center of the first light-emitting layer is located at an interface between the first sub-light-emitting layer and the second sub-light-emitting layer or in the second sub-light-emitting layer, the second light-emitting unit includes a second light-emitting layer, and the second light-emitting layer is a blue light-emitting layer.

[0016] In an example embodiment, the light-emitting functional layer comprises a first light-emitting unit and a second light-emitting unit stacked in sequence along the direction away from the substrate, and a charge generation layer disposed between the first light-emitting unit and the second light-emitting unit, the first light-emitting unit comprises a first light-emitting layer, the first light-emitting layer is a blue light-emitting layer; the second light-emitting unit comprises a second light-emitting layer, the second light-emitting layer emits yellow light, the second light-emitting layer comprises a first sub-light-emitting layer and a second sub-light-emitting layer stacked in sequence along the direction away from the substrate, the first sub-light-emitting layer is a red light-emitting layer, the second sub-light-emitting layer is a green light-emitting layer, the first sub-light-emitting layer and the second sub-light-emitting layer are in contact with each other, and the exciton recombination center of the second light-emitting layer is located at the contact interface of the first sub-light-emitting layer and the second sub-light-emitting layer, or in the second sub-light-emitting layer.

[0017] In an example embodiment, the at least one light-emitting unit further comprises a hole injection layer, a hole transport layer, a functional layer, a hole blocking layer and an electron transport layer, the hole transport layer is located between the light-emitting layer and the first electrode, the hole injection layer is located on the side of the hole transport layer close to the substrate and in contact with the first electrode; the functional layer is located on the side of the hole transport layer away from the substrate and in contact with the light-emitting layer; the electron transport layer is located between the light-emitting layer and the second electrode, and the hole blocking layer is disposed on the side of the electron transport layer close to the substrate and in contact with the light-emitting layer.

[0018] In an example embodiment, the first electrode comprises a first conductive pattern, a second conductive pattern and a third conductive pattern stacked in sequence along the direction away from the substrate; or the first electrode comprises a first conductive pattern, a second conductive pattern, a dielectric layer and a third conductive pattern stacked in sequence along the direction away from the substrate, the dielectric layer is provided with a via hole, and the third conductive pattern is connected with the second conductive pattern through the via hole.

[0019] On the other hand, the disclosure also provides a preparation method of a display substrate, comprising:

[0020] forming a first electrode, a light-emitting functional layer and a second electrode in sequence along the direction away from the substrate;

[0021] The light-emitting functional layer comprises at least one light-emitting unit, the at least one light-emitting unit comprises a light-emitting layer, the light-emitting layer comprises a first sub-light-emitting layer and a second sub-light-emitting layer stacked in sequence along the direction away from the substrate, the first sub-light-emitting layer and the second sub-light-emitting layer are in contact with each other, and the exciton recombination center of the light-emitting layer is located at the contact interface of the first sub-light-emitting layer and the second sub-light-emitting layer, or in the second sub-light-emitting layer.

[0022] In another aspect, the present disclosure also provides a display device comprising any of the display substrates described above.

[0023] Other aspects can become apparent from a review of the drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and serve to explain the principles of the present disclosure, and should not be considered limiting of the present disclosure's scope.

[0025] FIG. 1 is a structural schematic diagram of a display device;

[0026] FIG. 2 is a planar structural schematic diagram of a display area in a display device;

[0027] FIG. 3 is a cross-sectional structural schematic diagram of a display substrate according to an embodiment of the present disclosure;

[0028] FIG. 4 is a cross-sectional structural schematic diagram of a light-emitting structure layer of a display substrate according to an embodiment of the present disclosure;

[0029] FIG. 5 is a cross-sectional structural schematic diagram of another display substrate according to an embodiment of the present disclosure;

[0030] FIG. 6 is a cross-sectional structural schematic diagram of a light-emitting structure layer of another display substrate according to an embodiment of the present disclosure;

[0031] FIG. 7 is a graph of the relationship between current efficiency and red light luminance for different display substrates;

[0032] FIG. 8 is a graph of the relationship between current efficiency and green light luminance for different display substrates. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the present disclosure clearer, below the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the embodiments can be implemented in multiple different forms. One of ordinary skill in the art can easily understand that the manners and contents can be changed into various forms without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure should not be interpreted as being limited to the contents described in the following embodiments. The embodiments in the present disclosure and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0034] The scale of the drawings in this disclosure can be used as a reference in an actual process, but is not limited thereto. For example, the width-length ratio of the channel, the thickness and interval of each film layer, and the width and interval of each signal line can be adjusted as needed. The number of pixels in the display device and the number of sub-pixels in each pixel are not limited to the number shown in the drawings. The drawings described in this disclosure are merely schematic diagrams of the structure, and one embodiment of this disclosure is not limited to the shapes or values shown in the drawings.

[0035] The ordinal numbers "first", "second", "third" and the like in this specification are used to avoid confusion among components, and are not intended to indicate or imply a specific order or sequence.

[0036] In this specification, the words "center", "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like that indicate the orientation or positional relationship of components are used to describe the positional relationship of components with reference to the drawings, and are merely used for convenience of this specification and simplification of the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on this disclosure. The positional relationship of the components is appropriately changed according to the direction of describing each component. Therefore, it is not limited to the words described in the specification, and can be appropriately changed according to the situation.

[0037] In this specification, unless otherwise explicitly specified and limited, the terms "mount", "connected", "connected" should be understood broadly. For example, it can be fixedly connected, or detachably connected, or integrally connected; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate, or the communication between two elements. For those skilled in the art, the specific meaning of the above terms in this disclosure can be understood according to the specific circumstances.

[0038] In this specification, a transistor refers to an element including at least a gate electrode, a drain electrode, and a source electrode. The transistor has a channel region between the drain electrode (drain electrode terminal, drain region, or drain electrode) and the source electrode (source electrode terminal, source region, or source electrode), 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 a region where current mainly flows.

[0039] In this specification, the first electrode can be a drain electrode, and the second electrode can be a source electrode, or the first electrode can be a source electrode, and the second electrode can be a drain electrode. In the case of using a transistor with opposite polarity or in the case of changing the direction of current in the circuit operation, the functions of "source electrode" and "drain electrode" are sometimes exchanged with each other. Therefore, in this specification, "source electrode" and "drain electrode" can be exchanged with each other, and "source terminal" and "drain terminal" can be exchanged with each other.

[0040] In the present specification, "electrically connected" includes a case where elements constituting components are connected together through an element having some electrical action. The element having some electrical action is not particularly limited as long as it can perform transmission and reception of an electrical signal between the connected elements constituting components. Examples of the element having some electrical action include not only electrodes and wiring but also switching elements such as transistors, resistors, inductors, capacitors, and other elements having various functions.

[0041] In the present specification, "parallel" means a state where the angle formed by two straight lines is -10° or more and 10° or less, and thus, a state where the angle is -5° or more and 5° or less is also included. In addition, "perpendicular" means a state where the angle formed by two straight lines is 80° or more and 100° or less, and thus, a state where the angle is 85° or more and 95° or less is also included.

[0042] In the present specification, "film" and "layer" can be replaced with each other. For example, "a conductive layer" can be replaced with "a conductive film". Similarly, "an insulating film" can be replaced with "an insulating layer".

[0043] In the present specification, a triangle, a rectangle, a trapezoid, a pentagon, or a hexagon is not strictly a triangle, a rectangle, a trapezoid, a pentagon, or a hexagon, and can be an approximate triangle, a rectangle, a trapezoid, a pentagon, or a hexagon. There can be some small deformation due to a tolerance, and there can be an inside corner, an arc side, and deformation.

[0044] In the present disclosure, "about" means not strictly limited to a boundary, and allows values within a range of process and measurement errors.

[0045] The display substrate provided by the embodiment of the present disclosure includes at least one sub-pixel, and the at least one sub-pixel includes a first electrode, a light-emitting functional layer, and a second electrode which are sequentially stacked in a direction away from a substrate; the light-emitting functional layer includes at least one light-emitting unit, and the at least one light-emitting unit includes a light-emitting layer which includes a first sub-light-emitting layer and a second sub-light-emitting layer which are sequentially stacked in the direction away from the substrate, the first sub-light-emitting layer and the second sub-light-emitting layer contact each other, and an exciton recombination center of the light-emitting layer is located at an interface between the first sub-light-emitting layer and the second sub-light-emitting layer, or is located in the second sub-light-emitting layer.

[0046] FIG. 1 is a structural schematic diagram of a display device. As shown in FIG. 1, the display device can include a timing controller, a data driver, a scan driver, an emission driver, and a pixel array. The timing controller is connected to the data driver, the scan driver, and the emission driver, respectively. The data driver is connected to a plurality of data signal lines (e.g., D1 to Dn), the scan driver is connected to a plurality of scan signal lines (e.g., S1 to Sm), and the emission driver is connected to a plurality of emission control lines (e.g., E1 to Eo), respectively. Here, n, m, and o can be natural numbers. The pixel array can include at least two sub-pixels Pxij, i and j can be natural numbers. At least one sub-pixel Pxij can include a pixel circuit and an emission device connected to the pixel circuit. The pixel circuit can be connected to the scan signal line, the emission control line, and the data signal line, respectively.

[0047] In some example embodiments, the timing controller can provide a gray scale value and a control signal suitable for the specification of the data driver to the data driver, can provide a clock signal, a scan start signal, and the like suitable for the specification of the scan driver to the scan driver, and can provide a clock signal, an emission stop signal, and the like suitable for the specification of the emission driver to the emission driver. The data driver can generate a data voltage to be provided to the data signal lines D1, D2, D3, …, and Dn using the gray scale value and the control signal received from the timing controller. For example, the data driver can sample the gray scale value using the clock signal and apply a data voltage corresponding to the gray scale value to the data signal lines D1 to Dn in units of a pixel. The scan driver can generate a scan signal to be provided to the scan signal lines S1, S2, S3, …, and Sm by receiving the clock signal, the scan start signal, and the like from the timing controller. For example, the scan driver can sequentially provide a scan signal having an on-level pulse to the scan signal lines S1 to Sm. For example, the scan driver can be configured in the form of a shift register and can generate the scan signal in such a manner that the scan start signal provided in the form of an on-level pulse is sequentially transferred to a next stage circuit under the control of the clock signal. The emission driver can generate an emission control signal to be provided to the emission control lines E1, E2, E3, …, and Eo by receiving the clock signal, the emission stop signal, and the like from the timing controller. For example, the emission driver can sequentially provide an emission signal having an off-level pulse to the emission control lines E1 to Eo. For example, the emission driver can be configured in the form of a shift register and can generate the emission control signal in such a manner that the emission stop signal provided in the form of an off-level pulse is sequentially transferred to a next stage circuit under the control of the clock signal.

[0048] FIG. 2 is a schematic diagram of a planar structure of a display region in a display device. As shown in FIG. 2, the display region of the display device can include a plurality of pixel units P arranged in a matrix manner, at least one of the plurality of pixel units P including a first sub-pixel P1 emitting first color light, a second sub-pixel P2 emitting second color light, and a third sub-pixel P3 emitting third color light, the first sub-pixel P1, the second sub-pixel P2, and the third sub-pixel P3 each including a pixel driving circuit and a light emitting device. The pixel driving circuit in each sub-pixel is connected to a scan signal line and a data signal line, respectively, and is configured to receive a data voltage transmitted by the data signal line under the control of the scan signal line and output a corresponding current to the display light emitting device. The display light emitting device in each sub-pixel is connected to the pixel driving circuit in the sub-pixel, and is configured to emit light of a corresponding brightness in response to the current output by the pixel driving circuit in the sub-pixel.

[0049] In an example embodiment, the first sub-pixel P1 can be a red sub-pixel emitting red (R) light, the second sub-pixel P2 can be a green sub-pixel emitting green (G) light, and the third sub-pixel P3 can be a blue sub-pixel emitting blue (B) light. In an example embodiment, the shape of the sub-pixel can be any one or more of a triangle, a square, a rectangle, a diamond, a trapezoid, a parallelogram, a pentagon, a hexagon, and other polygons, and can be arranged in a horizontal side-by-side manner, a vertical side-by-side manner, an X shape, a cross shape, a pin shape, a square shape, a diamond shape, or a delta shape, without limitation in the present disclosure.

[0050] In an example embodiment, the pixel unit can include four sub-pixels, without limitation in the present disclosure.

[0051] FIG. 3 is a schematic diagram of a cross-sectional structure of a display substrate according to an embodiment of the present disclosure, which can be a cross-sectional view of the A-A' direction in FIG. 2. The display substrate shown in FIG. 3 is a structure for realizing full color in a white light + color film manner. As shown in FIG. 3, in a direction perpendicular to the display substrate, the display substrate according to an embodiment of the present disclosure can include a substrate 101, a driving circuit layer 102 disposed on the substrate 101, a light emitting structure layer 103 disposed on a side of the driving circuit layer 102 away from the substrate 101, an encapsulation layer 104 disposed on a side of the light emitting structure layer 103 away from the substrate 101, a color film structure layer 105 disposed on a side of the encapsulation layer 104 away from the substrate 101, and an optical auxiliary layer 106 disposed on a side of the color film structure layer 105 away from the substrate 101. In some possible implementations, the display device can include other film layers, such as a touch film layer, a cover plate layer, etc., without limitation in the present disclosure.

[0052] In an example embodiment, the substrate 101 can be a silicon substrate or a glass substrate. In an example embodiment, the substrate 101 can be a silicon substrate or a glass substrate.

[0053] In an example embodiment, the driving circuit layer 102 can be prepared on the substrate 101 by a silicon semiconductor process (e.g., a CMOS process), and can include a plurality of circuit units, which can at least include pixel driving circuits, respectively connected with scan signal lines and data signal lines, and can include a plurality of transistors and storage capacitors.

[0054] In an example embodiment, the light-emitting structure layer 103 can include a plurality of light-emitting devices, which can be tandem light-emitting devices and emit white light. The light-emitting functional layer of the tandem light-emitting device includes at least two light-emitting units stacked and connected in series along the vertical substrate direction, and a charge generation layer is provided between the adjacent two light-emitting units, which generates holes and electrons under the voltage action of the first electrode and the second electrode.

[0055] In an example embodiment, the light-emitting device can at least include a first electrode 11, a light-emitting functional layer 12, and a second electrode 13 stacked in sequence along the direction away from the substrate 101, the first electrode 11 can be connected with a transistor through a connecting electrode, the light-emitting functional layer 12 is connected with the first electrode 11, the second electrode 13 is connected with the light-emitting functional layer 12, the second electrode 13 is connected with a voltage line, and the light-emitting functional layer 12 emits light under the driving of the first electrode 11 and the second electrode 13.

[0056] In an example embodiment, the encapsulation layer 104 can be prepared in a thin film encapsulation (TFE) manner, which can ensure that external water vapor cannot enter the light-emitting structure layer.

[0057] In an example embodiment, the color film structure layer 105 can include a black matrix (BM) and a color filter (CF), the positions of the color filters can correspond to the positions of the light-emitting devices, the black matrix can be located between adjacent color filters, and the color filters are configured to filter the white light emitted by the light-emitting devices into red (R) light, green (G) light, or blue (B) light, forming red sub-pixels, green sub-pixels, and blue sub-pixels.

[0058] In an example embodiment, the optical auxiliary layer 106 includes a plurality of convex lenses, which can correspond to the color filters, and the convex lenses cover the convex projections of the corresponding color filters on the substrate. The convex lenses are configured to converge the red (R) light, green (G) light, or blue (B) light emitted by the color filters, thereby improving the brightness of the corresponding sub-pixels.

[0059] In the example embodiment, the display substrate further comprises a pixel definition layer 21 disposed on the side of the first electrode 11 away from the base 101, the pixel definition layer 21 is configured to define pixel openings for sub-pixels, the pixel openings expose at least part of the first electrode 11, and the light-emitting functional layer 12 covers the pixel openings and contacts the first electrode 11 exposed by the pixel openings. In the example embodiment, the first electrode 11 can be a full reflection electrode. The first electrode 11 can be a single-film layer or a multi-film layer structure prepared by a sputtering process.

[0060] In the example embodiment, the first electrode 11 can be a weak microcavity structure. The first electrode 11 can comprise a first conductive pattern 11-1, a second conductive pattern 11-2, and a third conductive pattern 11-3 stacked in sequence along the direction away from the base 101, the second conductive pattern 11-2 is disposed on the side of the first conductive pattern 11-1 away from the base 101 and contacts the first conductive pattern 11-1, and the third conductive pattern 11-3 is disposed on the side of the second conductive pattern 11-2 away from the base 101 and contacts the second conductive pattern 11-2.

[0061] In the example embodiment, the materials of the first conductive pattern 11-1 and the third conductive pattern 11-3 can be metal compounds, such as indium tin oxide (ITO), and the material of the second conductive pattern 11-2 can be a conductive metal, such as silver, aluminum, etc. The thickness of the first conductive pattern 11-1 and the third conductive pattern 11-3 can each be 70 angstroms to 100 angstroms (including the end point values), and the thickness of the second conductive pattern 11-2 can be 800 angstroms to 1200 angstroms (including the end point values).

[0062] In some embodiments, the first electrode can include a number of conductive layers other than three layers, for example, the first electrode can include two layers, four layers, five layers, six layers, etc. For example, the first electrode can include four conductive layers, the first electrode can include a first conductive pattern, a second conductive pattern, a third conductive pattern, and a fourth conductive layer stacked in sequence along the direction perpendicular to the base, the material of the first conductive pattern can be titanium, the material of the second conductive pattern can be aluminum, the material of the third conductive pattern can be titanium or titanium nitride, and the material of the fourth conductive layer can be indium tin oxide, the thickness of the first conductive pattern can be 50 angstroms to 100 angstroms (including the end point values), the thickness of the second conductive pattern can be 800 angstroms to 2000 angstroms (including the end point values), the thickness of the third conductive pattern can be 50 angstroms to 100 angstroms (including the end point values), and the thickness of the fourth conductive layer can be 50 angstroms to 100 angstroms (including the end point values).

[0063] FIG. 4 is a schematic diagram of a cross-sectional structure of a light-emitting structure layer of a display substrate according to an embodiment of the present disclosure. The light-emitting structure layer shown in FIG. 4 can be the light-emitting structure layer in FIG. 3. In an exemplary embodiment, as shown in FIG. 4, the light-emitting functional layer 12 is located between the first electrode 11 and the second electrode 13 and is in contact with the first electrode 11 and the second electrode 13, respectively. The light-emitting functional layer 12 can include a first light-emitting unit 12-1 and a second light-emitting unit 12-2 stacked in sequence along a direction away from the substrate 101, and a charge generation layer 30 disposed between the first light-emitting unit 12-1 and the second light-emitting unit 12-2.

[0064] In an exemplary embodiment, the first light-emitting unit 12-1 is located on a side of the second light-emitting unit 12-2 close to the substrate, and is in series with the second light-emitting unit 12-2 through the charge generation layer 30.

[0065] The display substrate according to an embodiment of the present disclosure achieves the effect of emitting white light by superimposing light emitted by the first light-emitting unit 12-1 and light emitted by the second light-emitting unit 12-2.

[0066] In an exemplary embodiment, the sum of the thickness of the light-emitting functional layer 12 and the thickness of the second electrode 13 is 200 angstroms to 250 angstroms (including the end point values). For example, the sum of the thickness of the light-emitting functional layer 12 and the thickness of the second electrode 13 is 210 angstroms to 230 angstroms (including the end point values).

[0067] In an exemplary embodiment, the first light-emitting unit 12-1 can include a first auxiliary layer 41, a first light-emitting layer 31, and a second auxiliary layer 42 stacked in sequence along a direction away from the substrate 101, and the first light-emitting layer 31 is in contact with the first auxiliary layer 41 and the second auxiliary layer 42, respectively. The first auxiliary layer 41 is located on a side of the first light-emitting layer 31 close to the substrate and is in contact with the first electrode 11, and the second auxiliary layer 42 is located on a side of the first light-emitting layer 31 away from the substrate and is in contact with the charge generation layer 30.

[0068] In an exemplary embodiment, the first auxiliary layer 41 includes at least a first hole transport layer 41-1 (HTL), and the first hole transport layer 41-1 is disposed between the first light-emitting layer 31 and the first electrode 11. The first auxiliary layer 41 can further include a first hole injection layer 41-2 (HIL) and a first functional layer 41-3 (prime), the first hole injection layer 41-2 is located on a side of the first hole transport layer 41-1 close to the substrate and is in contact with the first electrode 11, and the first functional layer 41-3 is located on a side of the first hole transport layer 41-1 away from the substrate and is in contact with the first light-emitting layer 31.

[0069] In an example embodiment, the second auxiliary layer 42 includes at least a first electron transport layer 42-1 (ETL), which is disposed between the first light-emitting layer 31 and the second electrode 13, and in contact with the charge generation layer 30. The second auxiliary layer 42 can further include a first hole blocking layer 42-2 (HBL), which is disposed on the side of the first electron transport layer 42-1 close to the substrate, and in contact with the first light-emitting layer 31.

[0070] In an example embodiment, the first light-emitting layer 31 includes a first sub-light-emitting layer 51 and a second sub-light-emitting layer 52 stacked in sequence along a direction away from the substrate, the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52 are in contact with each other, the first sub-light-emitting layer 51 is located on the side of the second sub-light-emitting layer 52 close to the first electrode 11, and the second sub-light-emitting layer 52 is located on the side of the first sub-light-emitting layer 51 close to the second electrode 13. The first sub-light-emitting layer 51 can emit first color light, and the second sub-light-emitting layer 52 can emit second color light.

[0071] In an example embodiment, the first sub-light-emitting layer 51 can be a red light-emitting layer, and the first sub-light-emitting layer 51 can emit red light; the second sub-light-emitting layer 52 can be a green light-emitting layer, and the second sub-light-emitting layer 52 can emit green light, and the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52 are stacked with each other to realize that the first light-emitting layer 31 emits yellow light.

[0072] In an example embodiment, the exciton recombination center of the first light-emitting layer 31 is located at the contact interface between the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52, or in the second sub-light-emitting layer 52, thereby improving the light-emitting efficiency of the second sub-light-emitting layer 52, helping to reduce the voltage and improve the display efficiency. Wherein, the exciton recombination center can capture electrons and holes to increase the recombination probability of the electrons and holes.

[0073] In an example embodiment, the thickness of the first sub-light-emitting layer 51 is less than the thickness of the second sub-light-emitting layer 52. Wherein, the thickness of the first sub-light-emitting layer 51 is the average size of the first sub-light-emitting layer 51 perpendicular to the substrate direction; and the thickness of the second sub-light-emitting layer 52 is the average size of the first sub-light-emitting layer 51 perpendicular to the substrate direction.

[0074] The display substrate of the example embodiment of the present disclosure has the thickness of the first sub-light-emitting layer 51 less than the thickness of the second sub-light-emitting layer 52, which is conducive to the holes passing through the first sub-light-emitting layer 51, and the exciton recombination center of the first light-emitting layer 31 is biased towards the side close to the second sub-light-emitting layer 52, for example, the exciton recombination center of the first light-emitting layer 31 is located at the contact interface between the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52, or the exciton recombination center of the first light-emitting layer 31 is located in the second sub-light-emitting layer 52.

[0075] In an example embodiment, the difference between the thickness of the second sub-light-emitting layer 52 and the thickness of the first sub-light-emitting layer 51 is 50 angstroms to 370 angstroms (including the end values). For example, the difference between the thickness of the second sub-light-emitting layer 52 and the thickness of the first sub-light-emitting layer 51 is 100 angstroms to 200 angstroms (including the end values).

[0076] In an example embodiment, the thickness of the first sub-light-emitting layer 51 is 30 angstroms to 150 angstroms (including the end values). For example, the thickness of the first sub-light-emitting layer 51 is 50 angstroms to 100 angstroms (including the end values).

[0077] In an example embodiment, the thickness of the second sub-light-emitting layer 52 is 200 angstroms to 400 angstroms (including the end values). For example, the thickness of the second sub-light-emitting layer 52 is 250 angstroms to 300 angstroms (including the end values).

[0078] In an example embodiment, the first sub-light-emitting layer 51 includes a first host material and a first guest material, the second sub-light-emitting layer 52 includes a second host material and a second guest material, the first host material and the second host material are the same, and for example, the first host material includes a first P-type semiconductor material and a first N-type semiconductor material, the second host material includes a second P-type semiconductor material and a second N-type semiconductor material, the first P-type semiconductor material is the same as the second P-type semiconductor material, and the first N-type semiconductor material is the same as the second N-type semiconductor material.

[0079] In an example embodiment, the first P-type semiconductor material and the second P-type semiconductor material can each include at least one of a triphenylamine derivative, a carbazole derivative. The first N-type semiconductor material and the second N-type semiconductor material can each include at least one of a triazine derivative, a pyrazine derivative, a pyridine derivative, a quinoline derivative, and a phenanthroline derivative.

[0080] The display substrate according to the embodiments of the present disclosure has the first host material of the first sub-light-emitting layer 51 and the second host material of the second sub-light-emitting layer 52 being the same, which reduces the energy level barrier of the contact interface between the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52, is conducive to the transmission or recombination of carriers (e.g., holes) at the contact interface between the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52, helps to reduce the voltage, improve the display efficiency, and improve the display effect of the low gray scale of the display substrate.

[0081] In an example embodiment, the mass ratio of the first P-type semiconductor material to the first N-type semiconductor material of the first sub-light-emitting layer 51 can be the same as or different from the mass ratio of the second P-type semiconductor material to the second N-type semiconductor material of the second sub-light-emitting layer 52.

[0082] In the exemplary embodiments, the mass ratio of the first P-type semiconductor material to the first N-type semiconductor material of the first sub-light-emitting layer 51 can be 1 to 3 (including the end values). For example, the mass ratio of the first P-type semiconductor material to the first N-type semiconductor material of the first sub-light-emitting layer 51 can be 7:3, or the mass ratio of the first P-type semiconductor material to the first N-type semiconductor material of the first sub-light-emitting layer 51 can be 3:2.

[0083] In the exemplary embodiments, the mass ratio of the second P-type semiconductor material to the second N-type semiconductor material of the second sub-light-emitting layer 52 can be 0.5 to 1.5 (including the end values). For example, the mass ratio of the second P-type semiconductor material to the second N-type semiconductor material of the second sub-light-emitting layer 52 can be 1:1.

[0084] In the exemplary embodiments, the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52 can be deposited by a mixed evaporation method. In the mixed evaporation process, the ratio of the evaporation rates of the P-type semiconductor material and the N-type semiconductor material can be controlled to obtain the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52.

[0085] In the exemplary embodiments, the triplet energy level of the first host material of the first sub-light-emitting layer 51 and the triplet energy level of the second host material of the second sub-light-emitting layer 52 are both greater than the triplet energy level of the second guest material of the second sub-light-emitting layer 52, which is conducive to energy transfer from the host material to the guest material, and helps to reduce the voltage and improve the display efficiency.

[0086] In the exemplary embodiments, the first light-emitting layer 31 can be a phosphorescent material.

[0087] In the exemplary embodiments, the second light-emitting unit 12-2 can include a third auxiliary layer 43, a second light-emitting layer 32, and a fourth auxiliary layer 44 stacked in sequence along the direction away from the substrate 101, and the second light-emitting layer 32 is in contact with the third auxiliary layer 43 and the fourth auxiliary layer 44, respectively. The third auxiliary layer 43 is located on the side of the second light-emitting layer 32 close to the substrate and is in contact with the charge generation layer 30, and the fourth auxiliary layer 44 is located on the side of the second light-emitting layer 32 away from the substrate and is in contact with the second electrode 13.

[0088] In the exemplary embodiments, the third auxiliary layer 43 at least includes a second hole transport layer 43-1 (HTL), and the second hole transport layer 43-1 is arranged between the second light-emitting layer 32 and the first electrode 11, and the second hole transport layer 43-1 is in contact with the charge generation layer 30. The third auxiliary layer 43 can further include a second functional layer 43-2 (prime), and the second functional layer 43-2 is located on the side of the second hole transport layer 43-1 away from the substrate and is in contact with the second light-emitting layer 32.

[0089] In an exemplary embodiment, the fourth auxiliary layer 44 includes at least a second electron transport layer 44-1 (ETL), which is disposed between the second light emitting layer 32 and the second electrode 13. The second auxiliary layer 42 can further include a second hole blocking layer 44-2 (HBL), which is disposed on the side of the second electron transport layer 44-1 closer to the substrate and in contact with the second light emitting layer 32, and an electron injection layer 44-3 (EIL), which is disposed on the side of the second electron transport layer 44-1 farther from the substrate and in contact with the second electrode 13.

[0090] In an exemplary embodiment, the second light emitting layer 32 can emit light of a third color. The second light emitting layer 32 and the first light emitting layer 31 are stacked with each other to realize a white light emitting device.

[0091] In an exemplary embodiment, the second light emitting layer 32 can be a blue light emitting layer, and the second light emitting layer 32 can emit blue light.

[0092] In an exemplary embodiment, the second light emitting layer 32 can be a fluorescent material or a phosphorescent material.

[0093] In an exemplary embodiment, the charge generation layer 30 can include a first generation layer 30-1 and a second generation layer 30-2 disposed in sequence along a direction away from the substrate, and the first generation layer 30-1 and the second generation layer 30-2 are in contact with each other. The first generation layer 30-1 is located on the side of the second generation layer 30-2 closer to the substrate and in contact with the first electron transport layer 42-1. The first generation layer 30-1 can be an N-type charge generation layer. The second generation layer 30-2 is located on the side of the first generation layer 30-1 farther from the substrate and in contact with the second hole transport layer 43-1. The second generation layer 30-2 can be a P-type charge generation layer.

[0094] In an exemplary embodiment, the second electrode 13 can transmit visible light. For example, the second electrode 13 can have a transmittance of visible light greater than or equal to 80%. Alternatively, the second electrode 13 can transmit a certain amount of visible light and reflect a certain amount of visible light. For example, the second electrode 13 can have a transmittance of visible light of 50%, and a reflectance of visible light of 50%.

[0095] FIG. 5 is a schematic view of a cross-sectional structure of another display substrate according to an embodiment of the present disclosure. FIG. 5 can be a cross-sectional view of the display substrate along the A-A' direction in FIG. 2. The display substrate shown in FIG. 5 is a structure for realizing full color using a white light + color filter method. As shown in FIG. 5, the structure of the display substrate according to the embodiment of the present disclosure is substantially the same as that shown in FIG. 3, except that the first electrode 11 of the display substrate according to the embodiment of the present disclosure is a strong microcavity structure. The first electrode 11 can include a first conductive pattern 11-1, a second conductive pattern 11-2, a dielectric layer 11-4, and a third conductive pattern 11-3, which are sequentially stacked in a direction perpendicular to the substrate. The second conductive pattern 11-2 is disposed on a side of the first conductive pattern 11-1 away from the substrate 101. The dielectric layer 11-4 is disposed on a side of the second conductive pattern 11-2 away from the substrate 101. The third conductive pattern 11-3 is disposed on a side of the dielectric layer 11-4 away from the substrate 101. The dielectric layer 11-4 has a via hole formed therein. The third conductive pattern 11-3 is connected to the second conductive pattern 11-2 through the via hole. The dielectric layer 11-4 is configured to adjust a vertical distance between a surface of the first electrode 11 on a side away from the substrate and a surface of the substrate.

[0096] In an example embodiment, the display substrate according to the embodiment of the present disclosure includes a first sub-pixel P1, a second sub-pixel P2, and a third sub-pixel P3. The first sub-pixel P1 can be a red sub-pixel that emits red (R) light, the second sub-pixel P2 can be a green sub-pixel that emits green (G) light, and the third sub-pixel P3 can be a blue sub-pixel that emits blue (B) light. A vertical distance h3 between a surface of the first electrode 11 on a side away from the substrate and a surface of the substrate for the third sub-pixel P3 is greater than a vertical distance h1 between a surface of the first electrode 11 on a side away from the substrate and a surface of the substrate for the first sub-pixel P1. The vertical distance h1 between a surface of the first electrode 11 on a side away from the substrate and a surface of the substrate for the first sub-pixel P1 is greater than a vertical distance h2 between a surface of the first electrode 11 on a side away from the substrate and a surface of the substrate for the second sub-pixel P2.

[0097] In an example embodiment, the thickness of the dielectric layer 11-4 in the first electrode 11 of the first sub-pixel P1 can be 100 angstroms to 150 angstroms (inclusive of the end points). The thickness of the dielectric layer 11-4 in the first electrode 11 of the second sub-pixel P2 can be less than or equal to 50 angstroms. The thickness of the dielectric layer 11-4 in the first electrode 11 of the third sub-pixel P3 can be 110 angstroms to 160 angstroms (inclusive of the end points).

[0098] In an exemplary embodiment, the material of the medium layer 11-4 can include a conductive material. For example, the material of the medium layer 11-4 can include at least one of indium tin oxide (ITO) and indium zinc oxide (IZO). The material of the medium layer 11-4 can also include an inorganic material. For example, the material of the medium layer 11-4 can include at least one of silicon oxide, silicon nitride, and silicon oxynitride.

[0099] In an exemplary embodiment, the medium layer 11-4 can be a light-transmitting material, and the transmittance of the medium layer 11-4 to visible light can be greater than 90%.

[0100] FIG. 6 is a schematic view of a cross-sectional structure of a light-emitting structure layer of a display substrate according to another embodiment of the present disclosure. The light-emitting structure layer shown in FIG. 6 can be the light-emitting structure layer in FIG. 5. As shown in FIG. 6, the structure of the light-emitting structure layer of the display substrate according to the embodiment of the present disclosure is basically the same as that shown in FIG. 4, except that the first light-emitting layer 31 of the display substrate according to the embodiment of the present disclosure can emit light of a third color. The second light-emitting layer 32 includes a first sub-light-emitting layer 51 and a second sub-light-emitting layer 52 stacked in sequence along a direction away from the substrate, the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52 are in contact with each other, the first sub-light-emitting layer 51 is located on the side of the second sub-light-emitting layer 52 close to the first electrode 11, and the second sub-light-emitting layer 52 is located on the side of the first sub-light-emitting layer 51 close to the second electrode 13. The first sub-light-emitting layer 51 can emit light of a first color, and the second sub-light-emitting layer 52 can emit light of a second color.

[0101] In an exemplary embodiment, the first light-emitting layer 31 can be a blue light-emitting layer, and the first light-emitting layer 31 can emit blue light. The first sub-light-emitting layer 51 can be a red light-emitting layer, and the first sub-light-emitting layer 51 can emit red light. The second sub-light-emitting layer 52 can be a green light-emitting layer, and the second sub-light-emitting layer 52 can emit green light. The first sub-light-emitting layer 51 and the second sub-light-emitting layer 52 are stacked with each other, so that the second light-emitting layer 32 emits yellow light. The second light-emitting layer 32 and the first light-emitting layer 31 are stacked with each other, so that the light-emitting device emits white light.

[0102] The materials and sizes of the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52 according to the embodiment of the present disclosure are the same as those of the first sub-light-emitting layer 51 and the second sub-light-emitting layer 52 in FIG. 4, and the present disclosure will not be described here.

[0103] Simulation experiments are performed on the relationship between current efficiency and brightness of different display substrates.

[0104] FIG. 7 is a graph of current efficiency versus red light brightness for different display substrates. As shown in FIG. 7, line a is a graph of current efficiency versus red light brightness for a display substrate having a structure substantially the same as the display substrate shown in FIG. 5, wherein the first sub-light emitting layer emits red light and the second sub-light emitting layer emits green light, the host materials of the first sub-light emitting layer and the second sub-light emitting layer are different, the energy level mobility of the first sub-light emitting layer and the second sub-light emitting layer are different, the thickness of the first sub-light emitting layer is 200 angstroms, and the thickness of the second sub-light emitting layer is 300 angstroms. Line b is a graph of current efficiency versus red light brightness for a display substrate of an embodiment of the present disclosure, wherein the display substrate has a structure substantially the same as the display substrate shown in FIG. 5, wherein the first sub-light emitting layer emits red light and the second sub-light emitting layer emits green light, the host materials of the first sub-light emitting layer and the second sub-light emitting layer include the same P-type semiconductor material and N-type semiconductor material, the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the first sub-light emitting layer can be 6:4, and the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the second sub-light emitting layer can be 5:5; the thickness of the first sub-light emitting layer is 100 angstroms, and the thickness of the second sub-light emitting layer is 300 angstroms. Line c is a graph of current efficiency versus red light brightness for another display substrate of an embodiment of the present disclosure, wherein the display substrate has a structure substantially the same as the display substrate shown in FIG. 5, wherein the first sub-light emitting layer emits red light and the second sub-light emitting layer emits green light, the host materials of the first sub-light emitting layer and the second sub-light emitting layer include the same P-type semiconductor material and N-type semiconductor material, the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the first sub-light emitting layer can be 7:3, and the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the second sub-light emitting layer can be 5:5; the thickness of the first sub-light emitting layer is 100 angstroms, and the thickness of the second sub-light emitting layer is 300 angstroms.

[0105] FIG. 8 is a graph of the current efficiency and green light brightness of different display substrates. As shown in FIG. 8, line a is a graph of the current efficiency and red light brightness of a related display substrate, which has a structure substantially the same as that of the display substrate shown in FIG. 5, wherein the first sub-light emitting layer emits red light, the second sub-light emitting layer emits green light, the host materials of the first sub-light emitting layer and the second sub-light emitting layer are different, the energy level mobility of the first sub-light emitting layer and the second sub-light emitting layer are different, the thickness of the first sub-light emitting layer is 200 angstroms, and the thickness of the second sub-light emitting layer is 300 angstroms. Line b is a graph of the current efficiency and red light brightness of a display substrate according to an embodiment of the present disclosure, which has a structure substantially the same as that of the display substrate shown in FIG. 5, wherein the first sub-light emitting layer emits red light, the second sub-light emitting layer emits green light, the host materials of the first sub-light emitting layer and the second sub-light emitting layer include the same P-type semiconductor material and N-type semiconductor material, the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the first sub-light emitting layer can be 6:4, and the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the second sub-light emitting layer can be 5:5; the thickness of the first sub-light emitting layer is 100 angstroms, and the thickness of the second sub-light emitting layer is 300 angstroms. Line c is a graph of the current efficiency and red light brightness of another display substrate according to an embodiment of the present disclosure, which has a structure substantially the same as that of the display substrate shown in FIG. 5, wherein the first sub-light emitting layer emits red light, the second sub-light emitting layer emits green light, the host materials of the first sub-light emitting layer and the second sub-light emitting layer include the same P-type semiconductor material and N-type semiconductor material, the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the first sub-light emitting layer can be 7:3, and the mass ratio of the P-type semiconductor material and the N-type semiconductor material of the second sub-light emitting layer can be 5:5; the thickness of the first sub-light emitting layer is 100 angstroms, and the thickness of the second sub-light emitting layer is 300 angstroms.

[0106] As shown in FIGS. 7 and 8, the green light brightness of the related display substrate climbs severely at low high gray scale, the low gray scale green light brightness is small, the display substrate lacks green light when displaying an image at low gray scale, the color of the image is purple, which leads to display failure of low gray scale color purple. In contrast, the thickness of the red light emitting layer (the first sub-light emitting layer) of the display substrate according to an embodiment of the present disclosure is small, the host materials of the red light emitting layer and the green light emitting layer (the second sub-light emitting layer) are the same, the red light brightness and green light brightness curves of the display substrate according to an embodiment of the present disclosure match, and the color deviation at low gray scale is effectively improved.

[0107] The thickness of the first sub-light emitting layer 51 of the display substrate according to an embodiment of the present disclosure is smaller than the thickness of the second sub-light emitting layer 52, which is beneficial for holes to pass through the first sub-light emitting layer 51, makes the exciton recombination center of the first light emitting layer 31 deviate to the side close to the second sub-light emitting layer 52, and helps to reduce the voltage and improve the display efficiency.

[0108] The display substrate provided by the embodiment of the present disclosure has the same first main body material of the first sub-light emitting layer 51 and the second main body material of the second sub-light emitting layer 52, reduces the energy level barrier of the contact interface between the first sub-light emitting layer 51 and the second sub-light emitting layer 52, is beneficial to the transmission or recombination of carriers (for example, holes) at the contact interface between the first sub-light emitting layer 51 and the second sub-light emitting layer 52, helps to reduce the voltage, improve the display efficiency, and improve the display effect of the low gray scale of the display substrate.

[0109] The embodiment of the present disclosure also provides a preparation method of a display substrate, comprising:

[0110] In step 101, a first conductive thin film is formed on a substrate by a sputtering process; then, the first conductive thin film is patterned by a gluing / exposure / development / etching / peeling process to form a first electrode corresponding to different sub-pixels.

[0111] In step 102, a pixel definition layer is formed on the side of the first electrode away from the substrate, and a pixel opening is arranged in the pixel definition layer, which exposes the first electrode of each sub-pixel.

[0112] In step 103, a light emitting functional layer is formed on the side of the pixel definition layer away from the substrate by an evaporation process, which covers the pixel opening and is in contact with the exposed first electrode. Some film layers in the light emitting functional layer of all sub-pixels can be a common layer connected together.

[0113] In step 104, a second electrode is formed on the side of the light emitting functional layer away from the substrate, and the second electrode of all sub-pixels can be a common layer connected together. The material of the second electrode can be an alloy, for example, the material of the second electrode can be a magnesium-silver alloy, and the mass ratio of magnesium to silver of the second electrode is 1:9. The thickness of the second electrode can be 100 angstroms to 200 angstroms (including the end point value). The second electrode is a semi-transparent material, and the transmittance of the second electrode to light can be 55% to 57% (including the end point value).

[0114] In step 105, a thin film encapsulation (TFE) method is used to form an encapsulation layer on the side of the second electrode away from the substrate.

[0115] In step 106, a color film structure layer is formed on the side of the encapsulation layer away from the substrate, and the color film structure layer includes a black matrix (BM) and a color filter (CF), and the position of the color filter can correspond to the pixel opening of the pixel definition layer.

[0116] The display device can be any product or component with a display function, such as a mobile phone, a wearable device, an AR or VR display device, a vehicle-mounted display device, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator, or the like, and the embodiments of the present application are not limited thereto.

[0117] The present application also provides a preparation method of a display substrate, which comprises:

[0118] forming a first electrode, a light-emitting functional layer, and a second electrode in sequence along a direction away from the substrate;

[0119] The light-emitting functional layer comprises at least one light-emitting unit, and the at least one light-emitting unit comprises a light-emitting layer, a hole transport layer, and an electron transport layer. -6 cm 2 / Vs, and the electron transport layer is located between the light-emitting layer and the second electrode, and the electron transport layer has an electron mobility greater than or equal to 1*10 -4 cm 2 / Vs and less than or equal to 1*10 -6 cm 2 / Vs. -4 cm 2 / Vs.

[0120] Although the embodiments of the present application are disclosed as above, the content described is only the embodiments adopted for the purpose of facilitating the understanding of the present application, and is not intended to limit the present application. Any person skilled in the art can make any modification and change in the form and details without departing from the spirit and scope of the present application, and the patent protection scope of the present application shall be subject to the scope defined by the appended claims.

Claims

1. A display substrate comprising at least one sub-pixel, the at least one sub-pixel comprising a first electrode, a light-emitting functional layer, and a second electrode, which are sequentially stacked along a direction away from a substrate; the light-emitting functional layer comprising at least one light-emitting unit, the at least one light-emitting unit comprising a light-emitting layer, the light-emitting layer comprising a first sub-light-emitting layer and a second sub-light-emitting layer, which are sequentially stacked along the direction away from the substrate, the first sub-light-emitting layer and the second sub-light-emitting layer being in contact with each other, an exciton recombination center of the light-emitting layer being located at an interface between the first sub-light-emitting layer and the second sub-light-emitting layer, or being located in the second sub-light-emitting layer. 2.The display substrate of claim 1, wherein, The thickness of the first sub-light-emitting layer is less than the thickness of the second sub-light-emitting layer. 3.The display substrate of claim 2, wherein, The difference between the thickness of the second sub-light-emitting layer and the thickness of the first sub-light-emitting layer is 50 angstroms to 370 angstroms. 4.The display substrate of claim 2, wherein, The thickness of the first sub-light-emitting layer is 30 angstroms to 150 angstroms. 5.The display substrate of claim 2, wherein, The thickness of the second sub-light-emitting layer is 200 angstroms to 400 angstroms. 6.The display substrate according to any one of claims 1 to 5, wherein The first sub-light-emitting layer comprises a first host material and a first guest material, the second sub-light-emitting layer comprises a second host material and a second guest material, and the first host material and the second host material are the same. 7.The display substrate of claim 6, wherein, The triplet energy level of the first host material and the second host material is greater than the triplet energy level of the second guest material. 8.The display substrate of claim 6, wherein, The first host material comprises a first P-type semiconductor material and a first N-type semiconductor material, the second host material comprises a second P-type semiconductor material and a second N-type semiconductor material, the first P-type semiconductor material is the same as the second P-type semiconductor material, and the first N-type semiconductor material is the same as the second N-type semiconductor material. 9.The display substrate of claim 8, wherein, The mass ratio of the first P-type semiconductor material to the first N-type semiconductor material can be 1 to 3, and the mass ratio of the second P-type semiconductor material to the second N-type semiconductor material can be 0.5 to 1.

5.

10. The display substrate according to any one of claims 1 to 5, wherein The first sub-light-emitting layer is a red light-emitting layer, and the second sub-light-emitting layer is a green light-emitting layer.

11. The display substrate according to any one of claims 1 to 5, wherein The light-emitting functional layer comprises a first light-emitting unit and a second light-emitting unit, which are sequentially stacked along the direction away from the substrate, and a charge generation layer arranged between the first light-emitting unit and the second light-emitting unit, the first light-emitting unit comprising a first light-emitting layer, the first light-emitting layer emitting yellow light, the first light-emitting layer comprising a first sub-light-emitting layer and a second sub-light-emitting layer, which are sequentially stacked along the direction away from the substrate, the first sub-light-emitting layer being a red light-emitting layer, the second sub-light-emitting layer being a green light-emitting layer, the first sub-light-emitting layer and the second sub-light-emitting layer being in contact with each other, an exciton recombination center of the first light-emitting layer being located at an interface between the first sub-light-emitting layer and the second sub-light-emitting layer, or being located in the second sub-light-emitting layer; the second light-emitting unit comprising a second light-emitting layer, the second light-emitting layer being a blue light-emitting layer.

12. The display substrate according to any one of claims 1 to 5, wherein The light-emitting functional layer comprises a first light-emitting unit and a second light-emitting unit stacked in sequence along a direction away from the substrate, and a charge generation layer arranged between the first light-emitting unit and the second light-emitting unit, the first light-emitting unit comprises a first light-emitting layer, and the first light-emitting layer is a blue light-emitting layer; The second light-emitting unit comprises a second light-emitting layer, the second light-emitting layer emits yellow light, the second light-emitting layer comprises a first sub-light-emitting layer and a second sub-light-emitting layer stacked in sequence along a direction away from the substrate, the first sub-light-emitting layer is a red light-emitting layer, the second sub-light-emitting layer is a green light-emitting layer, the first sub-light-emitting layer and the second sub-light-emitting layer are in contact with each other, and an exciton recombination center of the second light-emitting layer is located at an interface between the first sub-light-emitting layer and the second sub-light-emitting layer, or is located in the second sub-light-emitting layer.

13. The display substrate according to any one of claims 1 to 5, wherein The at least one light-emitting unit further comprises a hole injection layer, a hole transport layer, a functional layer, a hole blocking layer and an electron transport layer, the hole transport layer is located between the light-emitting layer and the first electrode, the hole injection layer is located on a side of the hole transport layer close to the substrate and in contact with the first electrode; The functional layer is located on a side of the hole transport layer away from the substrate and in contact with the light-emitting layer, the electron transport layer is located between the light-emitting layer and the second electrode, and the hole blocking layer is arranged on a side of the electron transport layer close to the substrate and in contact with the light-emitting layer.

14. The display substrate according to any one of claims 1 to 5, wherein The first electrode comprises a first conductive pattern, a second conductive pattern and a third conductive pattern stacked in sequence along a direction away from the substrate; or the first electrode comprises a first conductive pattern, a second conductive pattern, a dielectric layer and a third conductive pattern stacked in sequence along a direction away from the substrate, the dielectric layer is provided with a via hole, and the third conductive pattern is connected with the second conductive pattern through the via hole.

15. A preparation method of a display substrate, comprising: forming a first electrode, a light-emitting functional layer and a second electrode in sequence along a direction away from a substrate; The light-emitting functional layer comprises at least one light-emitting unit, the at least one light-emitting unit comprises a light-emitting layer, the light-emitting layer comprises a first sub-light-emitting layer and a second sub-light-emitting layer stacked in sequence along a direction away from the substrate, the first sub-light-emitting layer and the second sub-light-emitting layer are in contact with each other, and an exciton recombination center of the light-emitting layer is located at an interface between the first sub-light-emitting layer and the second sub-light-emitting layer, or is located in the second sub-light-emitting layer.

16. A display device comprising the display substrate according to any one of claims 1 to 14.

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