Display substrate, preparation method thereof and display device

Abstract

A display substrate, a manufacturing method thereof, and a display device are provided. The display substrate includes a substrate and a pixel defining layer having a plurality of pixel openings defining a plurality of sub-pixels, the pixel defining layer including a pixel defining portion between two adjacent pixel openings. The pixel defining portion has an undercut structure on a side facing the pixel opening, the undercut structure including a first portion, a second portion, and a third portion, the first portion being on a side of the second portion closer to the substrate, the first portion protruding in a direction toward the pixel opening relative to the third portion, the third portion being on a side of the second portion farther from the substrate, the second portion being recessed in a direction away from the pixel opening relative to the third portion. The first portion includes a main body portion, a raised portion, and a first protruding portion, the first protruding portion protruding in a direction away from the substrate relative to the main body portion, the first protruding portion being on a side of the first portion closer to the pixel opening.

Description

Display substrate, its preparation method, and display device Technical Field

[0001] This disclosure relates to the field of display technology, and in particular to a display substrate, a method for preparing the substrate, and a display device. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are microdisplays that have emerged in recent years. Using mature silicon-based semiconductor processes, high-PPI (pixel density) and high-refresh-rate OLED displays can be fabricated for applications in VR (Virtual Reality) and AR (Augmented Reality). Silicon-based OLEDs can achieve color display using white light plus three-color filters, and can achieve a superimposed light emission effect by using a charge generation layer (CGL) connected in series with multiple light-emitting layers. However, due to the precision limitations of traditional fine metal masks (FMMs), adjacent pixel units need to be separated using pixel isolation technology. How to achieve effective pixel isolation, reduce leakage current between pixels, and ensure the power consumption and stability of the display substrate is one of the important research topics for researchers.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] In one aspect, a display substrate is provided, comprising:

[0005] Substrate; and

[0006] A pixel defining layer is disposed on the substrate, the pixel defining layer having a plurality of pixel openings defining a plurality of sub-pixels, the plurality of sub-pixels being arranged in an array along a first direction and a second direction.

[0007] The pixel defining layer includes a pixel defining portion located between two adjacent pixel openings. The pixel defining portion has an undercut structure on the side facing the pixel opening. The undercut structure includes a first portion, a second portion, and a third portion. The first portion is located on the side of the second portion closer to the substrate. The first portion protrudes relative to the third portion in a direction toward the pixel opening. The third portion is located on the side of the second portion away from the substrate. The second portion is recessed relative to the third portion in a direction away from the pixel opening.

[0008] The first portion includes a main body, a raised portion, and a first protrusion, wherein the first protrusion is located on the side of the raised portion away from the substrate, and the first protrusion protrudes relative to the main body in a direction away from the substrate; and

[0009] The first protrusion is located on the side of the first portion near the pixel opening.

[0010] According to some exemplary embodiments, the display substrate further includes a light-emitting functional layer disposed on the side of the pixel defining layer away from the substrate. The light-emitting functional layer includes a first light-emitting functional portion located at the intersection of the undercut structure and the pixel opening. The first light-emitting functional portion includes a first surface away from the substrate. In a third direction, the first surface is spaced from the surface of the substrate near the pixel defining layer by a first spacing distance. In a direction along the pixel defining portion pointing towards the pixel opening, the first spacing distance gradually decreases. The third direction is parallel to the light emission direction of the display substrate.

[0011] In the direction from the pixel defining portion to the pixel opening, the first light-emitting functional portion has a first width, and the first portion protrudes a first protrusion distance relative to the third portion in the direction toward the pixel opening, the first protrusion distance being greater than or equal to the first width.

[0012] According to some exemplary embodiments, in the direction in which the pixel defining portion points to the pixel opening, the first protrusion has a second width, the ratio of the second width to the first protrusion distance being greater than or equal to 2 / 3.

[0013] According to some exemplary embodiments, in the third-party direction, the first protrusion has a first thickness, the second portion has a second thickness, and the first thickness is less than the second thickness.

[0014] According to some exemplary embodiments, the first protrusion includes a second surface remote from the substrate, the second surface being substantially parallel to a surface of the substrate near the pixel defining layer.

[0015] According to some exemplary embodiments, the first protrusion includes a second surface away from the substrate, and in the third direction, the second surface is spaced apart from the surface of the substrate near the pixel defining layer by a second spacing distance, and the second spacing distance gradually increases in the direction from the pixel defining portion to the pixel opening.

[0016] According to some exemplary embodiments, the first protrusion distance is greater than or equal to 0.1 micrometers.

[0017] According to some exemplary embodiments, the light-emitting functional layer includes: a first light-emitting sublayer; a charge-generating layer located on the side of the first light-emitting sublayer away from the substrate; and a second light-emitting sublayer located on the side of the charge-generating layer away from the substrate, wherein the first light-emitting sublayer is used to generate light of a first wavelength, and the second light-emitting sublayer is used to generate light of a second wavelength, wherein the first wavelength is greater than the second wavelength.

[0018] The second light-emitting sublayer includes a first light-emitting sub-part and a second light-emitting sub-part. The orthographic projection of the first light-emitting sub-part on the substrate at least partially overlaps with the orthographic projection of the pixel defining part on the substrate. The orthographic projection of the second light-emitting sub-part on the substrate at least partially overlaps with the orthographic projection of the pixel opening on the substrate. The first light-emitting sub-part and the second light-emitting sub-part are disconnected at the intersection of the undercut structure and the pixel opening.

[0019] According to some exemplary embodiments, the orthographic projection of the raised portion on the substrate does not overlap with the orthographic projection of the third portion on the substrate; and

[0020] The distance between the raised portion and the third portion in the direction of the pixel defining portion toward the pixel opening is greater than the distance by which the second portion is recessed relative to the third portion in the direction away from the pixel opening.

[0021] According to some exemplary embodiments, in the direction of the pixel defining portion toward the pixel opening, the spacing between the raised portion and the third portion is greater than the spacing between the first light-emitting sub-part and the second light-emitting sub-part.

[0022] According to some exemplary embodiments, the charge generation layer includes a first charge generation sub-section located at the intersection of the undercut structure and the pixel opening, the first charge generation sub-section including a third surface remote from the substrate, the third surface having a convex arc surface protruding away from the substrate in a direction remote from the substrate.

[0023] According to some exemplary embodiments, the first charge-generating sub-section includes a first side away from the pixel opening, and the second light-emitting sub-section includes a second side away from the pixel opening.

[0024] In the same sub-pixel, in the direction from the pixel definition portion to the pixel opening, the first side is further away from the pixel opening than the second side.

[0025] According to some exemplary embodiments, the light-emitting functional layer includes a plurality of first light-emitting functional sublayers located between the substrate and the second light-emitting sublayer. At least a portion of the plurality of first light-emitting functional sublayers includes a plurality of second protrusions located above the first portion. The orthographic projections of the plurality of second protrusions on the substrate at least partially overlap with the orthographic projections of the first protrusions on the substrate.

[0026] Along a direction away from the substrate, the plurality of second protrusions have convex arc surfaces away from the substrate, and the curvature of the convex arc surfaces of the plurality of second protrusions decreases sequentially.

[0027] According to some exemplary embodiments, the light-emitting functional layer includes a plurality of second light-emitting functional sublayers located on the side of the second light-emitting sublayer away from the substrate. At least a portion of the plurality of second light-emitting functional sublayers includes a plurality of recesses located above the first portion, and the plurality of recesses have a plurality of concave surfaces close to the substrate.

[0028] Wherein, the orthographic projections of the plurality of recesses on the substrate at least partially overlap with the orthographic projections of the first protrusion on the substrate; and

[0029] Along the direction away from the substrate, the curvature of the concave surfaces of the plurality of recesses decreases sequentially.

[0030] According to some exemplary embodiments, the second protrusion furthest from the substrate among the plurality of second protrusions and the recess closest to the substrate among the plurality of recesses are in direct contact.

[0031] According to some exemplary embodiments, on a plane parallel to the light emission direction of the display substrate, the first protrusion has a first cross-sectional shape, the first cross-sectional shape including at least one of rectangle, trapezoid and triangle.

[0032] According to some exemplary embodiments, in the third direction, the first protrusion has a first thickness, the second light-emitting sublayer has a third thickness, and the ratio of the first thickness to the third thickness is greater than or equal to 1 / 2.

[0033] According to some exemplary embodiments, the second surface has a first angle with the first plane direction, the first angle being greater than or equal to 45°, and the first plane direction is perpendicular to the light emission direction of the display substrate.

[0034] According to some exemplary embodiments, the first protrusion has a first slope angle on the side near the pixel opening, and a second slope angle on the side away from the pixel opening, wherein the first slope angle is smaller than the second slope angle.

[0035] In another aspect, a display device is provided, the display device comprising a display substrate as described in any of the preceding claims.

[0036] In another aspect, a method for fabricating a display substrate is provided, comprising:

[0037] Provide substrates;

[0038] A first electrode material layer is formed on one side of the substrate, and a patterning process is performed on the first electrode material layer to form the first electrode layer; and

[0039] A pixel defining material layer is formed on the side of the first electrode layer away from the substrate, and a patterning process is performed on the pixel defining material layer to form a pixel defining layer. The pixel defining layer has multiple pixel openings and includes a pixel defining portion located between two adjacent pixel openings. The pixel defining portion has an undercut structure on the side facing the pixel opening. The undercut structure includes a first portion, a second portion, and a third portion. The first portion is located on the side of the second portion near the substrate, and the first portion protrudes relative to the third portion in a direction towards the pixel opening. The third portion is located on the side of the second portion away from the substrate, and the second portion is recessed relative to the third portion in a direction away from the pixel opening. The first portion includes a main portion, a raised portion, and a first protrusion. The first protrusion is located on the side of the raised portion away from the substrate, and the first protrusion protrudes relative to the main portion in a direction away from the substrate. The first protrusion is located on the side of the first portion near the pixel opening.

[0040] The step of forming a pixel defining material layer on the side of the first electrode layer away from the substrate, and performing a patterning process on the pixel defining material layer to form the pixel defining layer includes:

[0041] A first insulating material is deposited on the side of the first electrode layer away from the substrate, and a patterning process is performed on the first insulating material;

[0042] The steps of depositing the first insulating material and performing a patterning process on the first insulating material are repeated n times to form a first portion including the first protrusion, where n is a positive integer greater than or equal to 3;

[0043] Deposit a second insulating material and perform a patterning process on the second insulating material to form a second portion; and

[0044] A third insulating material is deposited and a patterning process is performed on the third insulating material to form a third portion, thereby forming an undercut structure including a first protrusion in the pixel defining layer. Attached Figure Description

[0045] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0046] Figure 1 is a partial plan view of a display substrate according to an embodiment of the present disclosure;

[0047] Figure 2 is a schematic diagram of the structure of a light-emitting device according to some embodiments of the present disclosure;

[0048] Figure 3A is a schematic cross-sectional view of a display substrate according to some embodiments of the present disclosure, taken along line AA' in Figure 1, showing the undercut structure; Figure 3B is a schematic cross-sectional view of a display substrate according to some other embodiments of the present disclosure, taken along line AA' in Figure 1, showing the outcut structure.

[0049] Figure 4 is a partial cross-sectional schematic diagram of a display substrate according to some embodiments of the present disclosure, showing the case where the second light-emitting sublayer is distorted;

[0050] Figures 5A-5C are spectral comparison diagrams of planarized devices and pixelated devices under different voltages according to embodiments of the present disclosure;

[0051] Figure 6 is a partial cross-sectional schematic diagram of a display substrate according to an embodiment of the present disclosure;

[0052] Figure 7A is a partially enlarged schematic diagram of a display substrate in region S2 of Figure 6 according to some embodiments of the present disclosure, and Figure 7B is a partially enlarged schematic diagram of a display substrate in region S2 of Figure 6 according to other embodiments of the present disclosure.

[0053] Figure 8A is a partial cross-sectional schematic diagram of a display substrate according to an embodiment of the present disclosure, and Figure 8B is a partial cross-sectional schematic diagram of a display substrate according to some other embodiments of the present disclosure;

[0054] FIG9A is a cross-sectional schematic diagram of a reference display substrate according to an embodiment of the present disclosure, and FIG9B is a cross-sectional schematic diagram of an optimized display substrate according to an embodiment of the present disclosure;

[0055] Figure 10A is a partial light emission schematic diagram of the reference display substrate according to Figure 9A, and Figure 10B is a partial light emission schematic diagram of the optimized display substrate according to Figure 9B.

[0056] Figure 11A is a low grayscale viewing angle brightness diagram of the reference display substrate according to Figure 9A, and Figure 11B is a low grayscale viewing angle brightness diagram of the optimized display substrate according to Figure 9B.

[0057] Figure 12 is a comparison of the luminous efficiency of the blue light-emitting layer of the reference display substrate and the optimized display substrate;

[0058] Figure 13 is a comparison of the blue light spectra of the reference display substrate and the optimized display substrate;

[0059] Figure 14 is a schematic diagram of the structure of a display device according to an embodiment of the present disclosure; and

[0060] Figure 15 is a flowchart of a method for fabricating a display substrate according to an embodiment of the present disclosure.

[0061] It should be noted that, for clarity, the dimensions of layers, structures, or regions in the accompanying drawings used to describe embodiments of the present invention may be enlarged or reduced; that is, these drawings are not drawn to actual scale. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0063] It should be noted that, for clarity and / or descriptive purposes, the dimensions and relative dimensions of components may be enlarged in the accompanying drawings. Therefore, the dimensions and relative dimensions of the individual components are not necessarily limited to those shown in the drawings. In the specification and accompanying drawings, the same or similar reference numerals indicate the same or similar parts.

[0064] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0065] In this document, unless otherwise specified, directional terms such as "up," "down," "left," "right," "inner," and "outer" are used to indicate orientation or positional relationships based on the accompanying drawings, and are used only for the convenience of describing this disclosure, and are not intended to indicate or imply that the device, element, or component referred to must have a specific orientation, or be constructed or operated in a specific orientation. It should be understood that when the absolute position of the described object changes, the relative positional relationships they represent may also change accordingly. Therefore, these directional terms should not be construed as limitations on this disclosure.

[0066] Those skilled in the art will understand that, unless otherwise stated herein, the terms “height” or “thickness” refer to the dimensions along the surface of each film layer disposed perpendicular to the display substrate, i.e., the dimensions along the light-emitting direction of the display substrate, or the dimensions along the normal direction of the display device.

[0067] In this document, the directional terms "first direction" and "second direction" are used to describe different directions along a pixel unit, such as the vertical and horizontal directions of the pixel unit, or the row and column directions of a subpixel arrangement. It should be understood that such representations are merely exemplary descriptions and not limitations of this disclosure.

[0068] The technical terms used in this disclosure are briefly described below to help relevant personnel better understand this solution.

[0069] Transfer efficiency: Transfer efficiency is the ratio of the luminous efficiency of a display substrate to the luminous efficiency of a reference light-emitting device formed in the same manufacturing process. The anode and cathode of the reference light-emitting device are both solid-surface electrodes, making it a single, integrated light-emitting unit. This eliminates interference from factors such as leakage current on the luminous efficiency of the reference light-emitting device. The transfer efficiency can be used to measure the leakage current between pixel units in the display substrate; a higher transfer efficiency indicates a lower leakage current level between pixel units.

[0070] Distortion: Due to the significant height difference at the partition structure, the vapor-deposited material film in the OLED device may experience rapid changes in film morphology at the partition structure, resulting in distortion. The probability of leakage current is higher at distorted locations.

[0071] Exemplarily, embodiments of this disclosure provide a display substrate. Specifically, the display substrate includes: a substrate; and a pixel defining layer disposed on the substrate, the pixel defining layer having a plurality of pixel openings defining a plurality of sub-pixels, the plurality of sub-pixels being arranged in an array along a first direction and a second direction. The pixel defining layer includes a pixel defining portion located between two adjacent pixel openings, the pixel defining portion having an undercut structure on the side facing the pixel opening, the undercut structure including a first portion, a second portion, and a third portion, the first portion being located on the side of the second portion near the substrate, the first portion protruding relative to the third portion in the direction facing the pixel opening; the third portion being located on the side of the second portion away from the substrate, the second portion being recessed relative to the third portion in the direction away from the pixel opening. The first portion includes a main portion, a raised portion, and a first protrusion, the first protrusion being located on the side of the raised portion away from the substrate, the first protrusion protruding relative to the main portion in the direction away from the substrate; and the first protrusion being located on the side of the first portion near the pixel opening.

[0072] By designing an undercut structure, the charge generation layer and the light-emitting layer below it can be effectively isolated. By designing protrusions in the first part, and utilizing these protrusions to regulate the film layer structure at the intersection of the undercut structure and the pixel opening, the light-emitting layer above the charge generation layer can be effectively isolated. The combined design of the undercut structure and protrusions improves the isolation effect of multiple film layers at the intersection of the pixel opening and the undercut structure. This, in turn, improves display substrate leakage current, solves problems such as unstable low-grayscale emission state of light-emitting devices, and low low-grayscale efficiency of light-emitting devices, thus contributing to improved stability and display performance of the display substrate.

[0073] It should be noted that, in the embodiments of this disclosure, low grayscale refers to a situation where the luminous brightness of the display substrate is relatively low. Low grayscale includes situations where the driving voltage just reaches the turn-on voltage of the light-emitting devices in the display substrate and situations where the driving voltage is slightly higher than the turn-on voltage of the light-emitting devices in the display substrate.

[0074] Figure 1 is a partial plan view of a display substrate according to an embodiment of the present disclosure.

[0075] Exemplary examples, in some embodiments of this disclosure, referring to FIG1, show substrate 100 includes a display area AA and a plurality of sub-pixels SP located within the display area AA. The plurality of sub-pixels are arranged in an array along a first direction X and a second direction Y. The plurality of sub-pixels SP includes a first sub-pixel SP1 and a second sub-pixel SP2 that are adjacent in the first direction X or the second direction Y. Show substrate 100 also includes a pixel defining layer PDL. Pixel defining layer PDL has a plurality of pixel openings VH, which define the plurality of sub-pixels SP. For example, first sub-pixel SP1 includes a first pixel opening VH1, and second sub-pixel SP2 includes a second pixel opening VH2. The pixel opening may be an opening region that includes a light-emitting area.

[0076] It should be noted that although the embodiments of this disclosure schematically show that the pixel opening VH is square, in some embodiments of this disclosure, the pixel opening can also be various shapes such as rectangle, ellipse, circle, triangle, etc.

[0077] For example, multiple sub-pixels SP may include multiple light-emitting devices. For instance, one sub-pixel includes one light-emitting device.

[0078] In some embodiments, the light-emitting device may include an OLED light-emitting device.

[0079] Exemplary examples, in some embodiments of this disclosure, the display substrate may include a silicon-based OLED display substrate. For instance, the silicon-based OLED can achieve color display using a white light + three-color filter approach. A white OLED may include multiple stacked light-emitting layers, with different layers producing different colors of light. White light is formed by mixing different colors of light, and further, the mixed white light is combined with a filter structure to achieve a color display effect. For example, different light-emitting layers may include a yellow light-emitting layer and a blue light-emitting layer, or a red-green mixed light-emitting layer and a blue light-emitting layer. White light emission can be achieved through a yellow and blue light mixing design, or a red-green mixed light and blue light mixing design.

[0080] Figure 2 is a schematic diagram of the structure of a light-emitting device according to some embodiments of the present disclosure.

[0081] For example, referring to Figures 1 and 2, the display substrate 100 includes a substrate 1 and a first electrode layer 3 disposed on the substrate 1. The first electrode layer 3 includes a plurality of first electrodes 31, which are arranged in an array in a first direction X and a second direction Y. The orthographic projections of the plurality of pixel openings VH on the substrate 1 fall within the orthographic projections of the plurality of first electrodes 31 on the substrate 1. That is, the plurality of first electrodes 31 correspond one-to-one with the positions of the plurality of sub-pixels SP, and the area of ​​the first electrode is larger than the light-emitting area of ​​the sub-pixel.

[0082] For example, the light-emitting device may include a first electrode 31, a light-emitting functional layer 4, and a second electrode 51. For example, the first electrode 31 may be an anode, and the second electrode 51 may be a cathode. The light-emitting functional layer 4 may include multiple light-emitting functional film layers, such as a hole injection layer 41, a first hole transport layer 42, a first light-emitting sublayer 43, a first electron transport layer 44, a charge generation layer (CGL) 45, a second hole transport layer 46, a second light-emitting sublayer 47, a second electron transport layer 48, and an electron injection layer 49 disposed sequentially away from the substrate.

[0083] For example, the first light-emitting sublayer 43 can be used to generate light of a first wavelength, and the second light-emitting sublayer 47 can be used to generate light of a second wavelength. For example, the light of the first wavelength may include yellow light or red-green mixed light, and the light of the second wavelength may include blue light.

[0084] In some embodiments, the first luminescent sublayer 43 may include a single film layer formed by co-evaporation of a host material and a yellow luminescent dye, or the first luminescent sublayer 43 may include a single film layer formed by co-evaporation of a host material, a green luminescent dye and a red luminescent dye, or the first luminescent sublayer 43 may include multiple luminescent film layers. For example, the first luminescent sublayer may include a film layer formed by co-evaporation of a host material one and a green luminescent dye and a film layer formed by co-evaporation of a host material two and a red luminescent dye, wherein the host material one and the host material two may be the same or different.

[0085] In some embodiments, the second luminescent sublayer 47 may include a single film layer formed by co-evaporation of a host material and a blue luminescent dye.

[0086] In multilayer OLED devices, due to the high conductivity of the charge generation layer (CGL) 45, lateral crosstalk between pixels can easily occur when the charge generation layers of adjacent pixels are not separated. To reduce or eliminate lateral crosstalk between pixels, a separation structure can be designed between pixels, causing the charge generation layer to be disconnected at the separation structure. This reduces the probability of lateral crosstalk, helps reduce leakage current, and improves the stability of the display substrate and the display effect.

[0087] Figure 3A is a schematic cross-sectional view of a display substrate according to some embodiments of the present disclosure, taken along line AA' in Figure 1, showing the undercut structure. Figure 3B is a schematic cross-sectional view of a display substrate according to some other embodiments of the present disclosure, taken along line AA' in Figure 1, showing the outcut structure.

[0088] For example, in some embodiments of this disclosure, the pixel defining portion may employ an undercut structure (also known as an inner cut structure) or an outer cut structure (also known as an outer undercut structure) design for separating pixels. The undercut or outer cut structure can increase the step difference at the separation structure, thereby causing the charge generation layer to break at the separation structure.

[0089] By way of example, referring to Figures 1 and 3A, the pixel defining layer PDL includes a plurality of pixel defining portions PDL0. Each pixel defining portion PDL0 may include an undercut structure UDC. The undercut structure UDC includes a first portion UDC1, a second portion UDC2, and a third portion UDC3. The third portion UDC3 is located on the side of the second portion UDC2 away from the substrate 1, and the second portion UDC2 is recessed relative to the third portion UDC3 in a direction away from the pixel opening VH. The first portion UDC1 protrudes relative to the third portion UDC3 in a direction toward the pixel opening VH.

[0090] By designing an undercut structure in the pixel defining portion, that is, designing the part of the pixel defining portion near the pixel opening area as a structure with protruding ends and concave middle, the pixel defining portion can have a better isolation effect on the charge generation layer. At the same time, the required height of the pixel defining layer is lower, so the film layer above the pixel defining layer can be made smoother at the edge of the undercut structure. For example, the cathode layer can be made smoother, thereby improving the uniformity of the electric field distribution within the pixel and reducing stray light at the edges.

[0091] In some embodiments, the pixel defining portion may be designed with multiple undercut structures in the region facing the multiple pixel openings. For example, the pixel defining portion has an undercut structure on the side facing the first pixel opening VH1 and also has an undercut structure on the side facing the second pixel opening VH2.

[0092] For example, the undercut structures of the pixel definition portion facing different pixel openings can be the same or different. For instance, the distance d1 by which the first part UDC1 of the UDC structure near the first pixel opening VH1 protrudes relative to the third part UDC3 in the direction towards the first pixel opening VH1 can be the same as or different from the distance d4 by which the first part UDC1 of the UDC structure near the second pixel opening VH2 protrudes relative to the third part UDC3 in the direction towards the second pixel opening VH2. As another example, the distance d2 by which the second part UDC2 of the UDC structure near the first pixel opening VH1 is recessed relative to the third part UDC3 in the direction away from the first pixel opening VH1 can be the same as or different from the distance d3 by which the second part UDC2 of the UDC structure near the second pixel opening VH2 is recessed relative to the third part UDC3 in the direction away from the second pixel opening VH2.

[0093] By designing undercut structures at both ends of the pixel limiting portion, the number of undercut structures between adjacent pixels can be increased, which helps to further reduce the probability of lateral crosstalk between pixels, thereby improving the display effect of the display substrate.

[0094] For example, continuing to refer to FIG3A, the pixel defining layer PDL may include a plurality of pixel defining sublayers, which may be stacked. For example, the pixel defining layer PDL may include a first pixel defining sublayer PDL1, a second pixel defining sublayer PDL2, and a third pixel defining sublayer PDL3 stacked sequentially along the side away from the substrate 1.

[0095] For example, the first part UDC1 is located in the first pixel-defined sublayer PDL1, the second part UDC2 is located in the second pixel-defined sublayer PDL2, and the third part UDC3 is located in the third pixel-defined sublayer PDL3.

[0096] The materials of multiple pixel-defined sublayers can be the same or different. For example, the material of the first pixel-defined sublayer PDL1 may include SiO2. x ; and / or, the material of the second pixel-defined sublayer PDL2 may include SiN x ; and / or, the material of the third pixel-defined sublayer PDL3 includes SiO2. x Multiple pixel-defining sublayers can have different etching rates under the same etching process. For example, the etching rate of the second pixel-defining sublayer PDL2 can be higher than that of the third pixel-defining sublayer PDL3. This allows for the formation of a recessed structure in the second portion UDC2 relative to the third portion UDC3, moving away from the pixel opening. By forming pixel-defining portions with undercut structures, the charge generation layer can be effectively isolated, lateral crosstalk between pixels can be reduced, leakage current can be lowered, the transfer rate of the display substrate can be improved, and the display effect of the display substrate can be enhanced.

[0097] The depth of the undercut structure affects the partitioning effect of the pixel-defining portion. Generally speaking, the greater the depth of the undercut structure, that is, the greater the indentation distance (e.g., d2 or d3) of the second part UDC2 relative to the third part UDC3 in Figure 3A along the direction away from the pixel opening, the better the partitioning effect. However, the design of the indentation distance of the second part UDC2 relative to the third part UDC3 also needs to take into account the stability of the undercut structure itself and the influence of parameters such as the etching rate of the materials of both the second and third pixel-defining sublayers.

[0098] For example, the undercut structure can be formed using a simultaneous etching process for the second pixel-defining sublayer PDL2 and the third pixel-defining sublayer PDL3. Due to limitations such as etching rate and film support structure, the depth of the undercut structure is affected by the material properties and film thickness of the second pixel-defining sublayer PDL2 and the third pixel-defining sublayer PDL3. For example, when the material of the second pixel-defining sublayer PDL2 is SiN... x The material of the third pixel-defined sublayer PDL3 is SiO2. x Preferably, the second part UDC2 is recessed relative to the third part UDC3 by a distance greater than or equal to 400 angstroms and less than or equal to 600 angstroms in the direction away from the pixel opening.

[0099] By optimizing the depth of the undercut structure, we can ensure the structural stability of the undercut structure itself, and at the same time, maximize the isolation effect of the pixel limiting layer, reduce leakage current, and improve the transfer rate of the display substrate.

[0100] Because of the undercut structure with protruding ends and concave middle, when the pixel limiting part isolates the charge generation layer, it increases the concave distance of the second pixel limiting sub-layer. Therefore, the required height of the pixel limiting layer is smaller, which makes the second electrode layer above the pixel limiting layer more gentle and the electric field distribution above the second electrode layer more uniform, which is beneficial to improving the in-plane uniformity of the display substrate.

[0101] In some embodiments, by optimizing the design of the undercut structure UDC, it can be ensured that the charge generation layer is isolated at the undercut structure while the second electrode layer does not break at the undercut structure UDC, thereby improving the in-plane uniformity of the display substrate.

[0102] Exemplarily, in some embodiments, referring to FIG3B, the pixel defining portion PDL0 may employ an externally cleaved structure OTC. Here, the externally cleaved structure OTC refers to a partial hollowing-out design in the pixel defining portion PDL0 within the gap region between two adjacent pixel openings VH, forming a structure with a protruding top and a recessed bottom. For example, the externally cleaved structure OTC includes a fourth portion OTC1 and a fifth portion OTC2. The fifth portion OTC2 is located on the side of the fourth portion OTC1 away from the substrate 2, and the fifth portion OTC2 protrudes relative to the first portion OTC1 along the side away from the pixel opening VH. With this design, multiple film layers above the pixel defining portion can be disconnected at the externally cleaved structure OTC, thereby reducing the probability of lateral crosstalk between pixels.

[0103] The inventors discovered through research that although the pixel defining portion can isolate the charge generation layer and reduce lateral crosstalk between adjacent pixels, the large film layer step difference in the region of the pixel defining portion near the pixel opening causes multiple film layers located above the pixel defining layer (such as at least some of the hole injection layer 41, first hole transport layer 42, first light-emitting sublayer 43, first electron transport layer 44, charge generation layer (CGL) 45, second hole transport layer 46, second light-emitting sublayer 47, second electron transport layer 48, and electron injection layer 49 in Figure 2) to fluctuate with the pixel defining layer. Some film layers are distorted in the intersection area of ​​the pixel defining portion and the pixel opening, resulting in leakage current in the light-emitting device at the edge area of ​​the pixel opening. This leads to uneven light emission state, poor low grayscale stability, slow response of the device from unstable light emission state to normal light emission state, and low device efficiency, affecting the display effect of the display substrate.

[0104] In some embodiments, although the undercut structure UDC can reduce the film layer step difference near the pixel opening region of the pixel definition portion and reduce the probability of distortion of some film layers above the pixel definition portion compared to the outward cut structure OTC, there is still a situation where some film layers (e.g., the second light-emitting layer 47) are distorted in the intersection region of the pixel definition portion and the pixel opening.

[0105] Figure 4 is a partial cross-sectional schematic diagram of a display substrate according to some embodiments of the present disclosure, showing the distortion of the second light-emitting sublayer. Figures 5A-5C are spectral comparison diagrams of planarization devices and pixelation devices under different voltages according to embodiments of the present disclosure.

[0106] For example, in the intersection region DS1 of the pixel defining portion and the pixel opening, due to the large film layer step of the partition structure (e.g., the undercut structure UDC), at least some of the film layers have large film layer undulations in this region, and some of the film layers are prone to distortion in this region. For example, referring to FIG4, the second light-emitting sub-layer 47 is distorted in the intersection region DS1 of the pixel defining portion and the pixel opening. The second light-emitting sub-layer 47 includes a first light-emitting sub-part 471, a second light-emitting sub-part 472, and a third light-emitting sub-part 473. The orthographic projection of the first light-emitting sub-part 471 on the substrate at least partially overlaps with the orthographic projection of the pixel defining portion PDL0 on the substrate, and the orthographic projection of the second light-emitting sub-part 472 on the substrate at least partially overlaps with the orthographic projection of the pixel opening VH on the substrate. One end of the third light-emitting part 473 is connected to both the first light-emitting part 471 and the second light-emitting part 472, and the other end of the third light-emitting part 473 extends toward the concave region near the undercut structure (i.e., the region in the undercut structure where the second part UDC2 is recessed relative to the third part UDC3).

[0107] In some embodiments, the first light-emitting sublayer 43 is a red-green light-emitting layer, and the second light-emitting sublayer 47 is a blue light-emitting layer. Because the first light-emitting sublayer 43 is disconnected at the junction region DS1 of the pixel defining portion and the pixel opening, while the second light-emitting sublayer is distorted at the junction region DS1 (also called the distortion region), the first light-emitting sub-part 471 and the second light-emitting sub-part 472 are electrically connected in this distortion region. This may affect the resistance of the light-emitting device near the distortion region. For example, if the resistance of the light-emitting device is higher in the pixel opening region and lower in the distortion region, current will preferentially flow through the distortion region, causing the blue light at the pixel edge to be activated first. This may result in uneven device luminescence, poor low-grayscale stability, slow response of the device from an unstable luminescence state to a normal luminescence state, and low device efficiency, affecting the display effect of the display substrate.

[0108] For example, referring to Figures 5A-5C, with the horizontal axis representing wavelength and the vertical axis representing relative light emission intensity, Figures 5A-5C show a comparison of the relative light emission intensity of pixelated devices and planarized devices at different voltages (e.g., 5.5V, 6V, and 6.5V). The difference between pixelated and planarized devices lies in the following: the anode and cathode of a planarized device are both a single, continuous electrode, making it a single, integrated light-emitting unit. This eliminates interference from factors such as leakage current on the luminous efficiency of planarized devices. In contrast, pixelated devices (refer to Figures 1 and 4) include multiple spaced anodes, with pixel-defining portions between adjacent anodes to separate pixels. Because the pixel-defining portions of pixelated devices can cause film distortion and edge leakage, the relative light emission efficiency of pixelated devices is significantly lower than that of planarized devices at the same voltage. Especially at low grayscale levels (e.g., at 5.5V), the blue light emission efficiency of pixelated devices is significantly lower than that of planarized devices.

[0109] To improve the film distortion in the intersection region of the pixel defining portion and the pixel opening, the embodiments of this disclosure further optimize the undercut structure. By designing a first protrusion in the region of the first part of the undercut structure near the pixel opening, the morphology of at least a portion of the film layer above the first part can be controlled. For example, the morphology of the second light-emitting sublayer located in the intersection region of the pixel defining portion and the pixel opening can be controlled to prevent distortion of the second light-emitting sublayer in this region. This reduces the probability of leakage current in the display substrate, improves the low grayscale blue light phenomenon, and moves the light emission boundary towards the pixel opening side, which is beneficial to improving the blue light transfer rate and light emission efficiency, increasing the color purity of blue light, and thus improving the overall light emission efficiency.

[0110] Figure 6 is a partial cross-sectional schematic diagram of a display substrate according to an embodiment of the present disclosure, Figure 7A is a partial enlarged schematic diagram of a display substrate according to some embodiments of the present disclosure in the S2 region of Figure 6, and Figure 7B is a partial enlarged schematic diagram of a display substrate according to some other embodiments of the present disclosure in the S2 region of Figure 6.

[0111] For example, referring to Figures 1, 6, and 7A, the display substrate includes a substrate 1 and a pixel defining layer PDL disposed on the substrate. The pixel defining layer PDL has a plurality of pixel openings VH, which define a plurality of sub-pixels SP. The plurality of sub-pixels SP are arranged in an array along a first direction X and a second direction Y. The pixel defining layer PDL includes a pixel defining portion PDL0 located between two adjacent pixel openings VH, and the pixel defining portion PDL0 has an undercut structure UDC on the side facing the pixel opening VH.

[0112] The undercut structure UDC includes a first part UDC1, a second part UDC2, and a third part UDC3. The first part UDC1 is located on the side of the second part UDC2 closest to the substrate 1, and the first part UDC1 protrudes relative to the third part UDC3 in a direction toward the pixel opening VH. The third part UDC3 is located on the side of the second part UDC2 furthest from the substrate 1, and the second part UDC2 is recessed relative to the third part UDC3 in a direction away from the pixel opening. The first part UDC1 includes a main body UDC11, a first protrusion UDC12, and a raised portion UDC13. The first protrusion UDC12 is located on the side of the raised portion UDC13 furthest from the substrate 1, and the first protrusion UDC12 protrudes relative to the main body UDC11 in a direction away from the substrate 1; and the first protrusion UDC12 is located on the side of the first part closest to the pixel opening VH.

[0113] By providing a first protrusion on the side of the first part near the pixel opening, the first protrusion can adjust the step of the upper film layer, which can improve the distortion of the light-emitting functional layer in the intersection area of ​​the pixel limiting part and the pixel opening, so that the second light-emitting sub-layer is isolated in the intersection area, thereby reducing the probability of leakage of the light-emitting device in the edge area of ​​the pixel opening. This is beneficial to improving the problems of unstable low grayscale light emission state and low low grayscale efficiency of the device, and thus can stabilize the low grayscale performance of the display substrate, making the low grayscale of the display product more stable and adjustable.

[0114] In some embodiments, the main body UDC11, the raised portion UDC13, and the first protrusion UDC12 can be formed in multiple process steps. For example, the main body UDC11 and the raised portion UDC13 can be formed first, and then the first protrusion UDC12 can be formed.

[0115] To ensure the adjustment effect of the first part on the upper film layer, the protrusion distance of the first part relative to the third part towards the pixel opening side should exceed the width of the area of ​​the light-emitting functional layer that is prone to distortion. This allows the first part to adjust the film layer of the entire distortion area, which helps to reduce the leakage probability of the display substrate and improve the low grayscale performance of the display substrate.

[0116] For example, referring to FIG7A, the display substrate further includes a light-emitting functional layer 4 disposed on the side of the pixel defining layer PDL away from the substrate 1.

[0117] Exemplarily, the light-emitting functional layer 4 includes: a first light-emitting sublayer 43; a charge-generating layer 45 located on the side of the first light-emitting sublayer 43 away from the substrate; and a second light-emitting sublayer 47 located on the side of the charge-generating layer 45 away from the substrate. The first light-emitting sublayer 43 is used to generate light of a first wavelength, and the second light-emitting sublayer 47 is used to generate light of a second wavelength, wherein the first wavelength is greater than the second wavelength. For example, the first wavelength of light is red-green light, and the second wavelength of light is blue light.

[0118] The light-emitting functional layer 4 includes a first light-emitting functional portion 410 located in the intersection region DS1 of the undercut structure UDC and the pixel opening VH. The first light-emitting functional portion 410 includes a first surface 4101 away from the substrate. In the third direction Z, the first surface 4101 is separated from the surface 101 of the substrate 1 near the pixel limiting layer by a first spacing distance H1. In the direction from the pixel limiting portion PDL0 to the pixel opening VH, the first spacing distance H1 gradually decreases, and the third direction Z is parallel to the light emission direction of the display substrate. For example, the spacing distance H11 between a point O1 on the first surface 4101 away from the pixel opening and the surface 101 of the substrate 1 near the pixel limiting layer is greater than the spacing distance H12 between a point O2 on the first surface 4101 near the pixel opening and the surface 101 of the substrate 1 near the pixel limiting layer.

[0119] In the direction from the pixel defining portion PDL0 to the pixel opening VH, the first light-emitting functional portion 410 has a first width D1. The first portion UDC1 protrudes a first protrusion distance M1 relative to the third portion UDC3 in the direction toward the pixel opening. For example, the first protrusion distance M1 is greater than or equal to the first width D1.

[0120] In some exemplary embodiments, the first protrusion distance M1 is greater than or equal to 0.1 micrometers. For example, the first protrusion distance M1 may be approximately 0.1 micrometers, 0.11 micrometers, 0.12 micrometers, 0.13 micrometers, or 0.15 micrometers.

[0121] With this design, the step difference of the film layer below the area where the first light-emitting functional part 410 is located can be reduced by using the first part UDC1, thereby reducing the probability of distortion of the first light-emitting functional part, and further reducing the probability of leakage in the pixel opening edge area of ​​the light-emitting device, which is beneficial to improving the luminous efficiency and low grayscale stability of the light-emitting device.

[0122] The inventors discovered through research that, referring to Figure 4, starting from the end furthest from the third portion UDC3, the light-emitting layer (e.g., the second light-emitting sub-layer 47) above the charge-generating layer is prone to distortion near the 1 / 3 position of the first portion UDC1. For example, in the direction from the pixel defining portion to the pixel opening, the ratio of the distance d5 between the location where the second light-emitting sub-layer is distorted and the distance M1 between the third portion UDC3 and the first protrusion distance is approximately 1 / 3. This may result in the formation of a third light-emitting sub-part 473 in this area. The first light-emitting sub-part 471 and the second light-emitting sub-part 472 are connected through the third light-emitting sub-part 473, resulting in lower resistance in the pixel opening edge region. This makes the pixel opening edge region prone to leakage, affecting the low grayscale efficiency and stability of the display substrate.

[0123] In order to effectively isolate the light-emitting layer above the charge-generating layer, in some embodiments of this disclosure, a first protrusion is designed on the first part, which can raise the film layer above the first protrusion, thereby realizing the adjustment of the film morphology of the light-emitting functional layer in the intersection area of ​​the pixel defining part and the pixel opening.

[0124] In some embodiments, by adjusting the width, height, and shape of the first protrusion, the morphology of the upper light-emitting functional layer can be adjusted in a targeted manner, thereby effectively isolating the second light-emitting sub-layer in the intersection area, which is beneficial to improving the leakage current at the edge of the device, thereby improving the stability of the low grayscale light emission state of the device and improving the low grayscale light emission efficiency of the device.

[0125] For example, referring to FIG7A, in the direction from the pixel defining portion PDL0 to the pixel opening VH, the first protrusion UDC12 has a second width D2. The ratio of the second width D2 to the first protrusion distance M1 is greater than or equal to 2 / 3. For example, the first protrusion distance M1 is approximately 0.15 micrometers, and the second width D2 is approximately 0.12 micrometers.

[0126] For example, referring to FIG6, on the third direction Z, the first protrusion UDC12 has a first thickness h1, and the second portion UDC2 has a second thickness h2.

[0127] For example, the second thickness h2 is greater than or equal to 300 angstroms and less than or equal to 600 angstroms. For example, the second thickness h2 is approximately 300 angstroms, 350 angstroms, 400 angstroms, 500 angstroms, or 600 angstroms. By optimizing the second thickness h2 of the second part UDC2, the effect of low grayscale spectrum modulation of the display substrate can be maintained while ensuring effective isolation of the charge generation layer. On the one hand, this reduces the leakage rate, improves the transfer rate of the display substrate, and enhances the efficiency and lifespan of the display substrate. On the other hand, it can modulate the spectrum of the display substrate, thereby improving the display effect of the display substrate.

[0128] For example, the first thickness h1 is less than the second thickness h2. By optimizing the height relationship between the second part UDC2 and the first protrusion UDC12, the morphology of the light-emitting functional layer located above the undercut structure can be adjusted, so that the first light-emitting sub-layer, the charge generation layer and the second light-emitting sub-layer are all isolated, which helps to reduce the probability of leakage current, thereby improving the stability of the device's low grayscale light emission state and improving the device's low grayscale light emission efficiency.

[0129] In some embodiments, the thicker the second light-emitting sublayer, the thicker the first protrusion required to separate the second light-emitting sublayer at the intersection of the pixel definition portion and the pixel opening.

[0130] For example, referring to FIG7A, in the third direction Z, the first protrusion UDC12 has a first thickness h1, and the second light-emitting sublayer 47 has a third thickness h3. The ratio of the first thickness h1 to the third thickness h3 is greater than or equal to 1 / 2. For example, the first thickness h1 is approximately 50 nanometers, and the third thickness h3 is approximately 100 nanometers. As another example, the first thickness h1 is approximately 100 nanometers, and the third thickness h3 is approximately 150 nanometers.

[0131] This design improves the effect of the first protrusion on the morphology of the second light-emitting sub-layer, thereby achieving the isolation of the second light-emitting sub-layer in the intersection area of ​​the pixel limiting part and the pixel opening, and reducing the probability of edge leakage of the light-emitting device.

[0132] For example, the second light-emitting sublayer 47 includes a first light-emitting sub-part 471 and a second light-emitting sub-part 472. The orthographic projection of the first light-emitting sub-part 471 on the substrate at least partially overlaps with the orthographic projection of the pixel defining portion PDL0 on the substrate, and the orthographic projection of the second light-emitting sub-part 472 on the substrate at least partially overlaps with the orthographic projection of the pixel opening VH on the substrate. The first light-emitting sub-part 471 and the second light-emitting sub-part 472 are disconnected at the intersection region DS1 of the undercut structure UDC and the pixel opening VH.

[0133] In some embodiments, by optimizing the width and height of the first protrusion, the second light-emitting sub-part 472 located above the first protrusion can be partially raised, forming a step difference between it and the first light-emitting sub-part 471 located above the pixel defining part. This allows the second light-emitting sub-part 472 and the first light-emitting sub-part 471 to be disconnected, which helps to reduce the probability of edge leakage of the light-emitting device, improve the low grayscale stability of the display substrate, and improve the low grayscale luminous efficiency.

[0134] In some embodiments, the first protrusion has a first cross-sectional shape on a plane parallel to the light emission direction of the display substrate. The first cross-sectional shape includes at least one of a rectangle, a trapezoid, and a triangle. For example, referring to FIG6, the first cross-sectional shape includes a rectangle.

[0135] For example, the first protrusion UDC12 includes a second surface UDC121 away from the substrate. The second surface UDC121 is substantially parallel to the surface 101 of the substrate near the pixel defining layer.

[0136] This design allows for easy adjustment of the height and width of the first protrusion, thereby better controlling the effect of the first protrusion on the shape of the second light-emitting sublayer. This isolates the second light-emitting sublayer at the intersection of the pixel limiting part and the pixel opening, which helps reduce the leakage probability of the display substrate and improve the luminous efficiency and low grayscale stability of the display substrate.

[0137] In some embodiments, the first cross-sectional shape of the first protrusion may also include a rectangular shape. For example, the first cross-sectional shape may include a trapezoid; or, an approximate rectangular shape consisting of a combination of curved sides and right-angled sides.

[0138] For example, continuing to refer to FIG7A, the charge generation layer 45 includes a first charge generation sub-section 451 located in the intersection region DS1 of the undercut structure and the pixel opening. The first charge generation sub-section 451 includes a third surface 4510 remote from the substrate. In a direction remote from the substrate (e.g., the third direction Z), the third surface 4510 has a convex arc surface that protrudes remotely from the substrate. By designing the first protrusion, at least a portion of the film layer located above the first protrusion can be raised, thereby causing at least a portion of the film layer (e.g., the charge generation layer) in the light-emitting functional layer to form a convex arc surface in this region.

[0139] For example, the first charge-generating sub-layer 451 includes a first side L1 away from the pixel opening, and the second light-emitting sub-layer 472 includes a second side L2 away from the pixel opening. Specifically, within the same sub-pixel, in the direction from the pixel defining portion PDL0 to the pixel opening VH, the first side L1 is further away from the pixel opening VH than the second side L2. This design ensures that both the charge-generating layer and the second light-emitting sub-layer are isolated in the intersection region DS1 of the pixel defining portion and the pixel opening, which helps reduce lateral leakage current in the display substrate and improves the low grayscale stability of the display substrate.

[0140] For example, referring to FIG7B, the orthographic projection of the raised portion UDC13 on the substrate does not overlap with the orthographic projection of the third portion UDC3 on the substrate.

[0141] For example, in the direction of the pixel limiting portion toward the pixel opening, the distance d0 between the raised portion UDC13 and the third portion UDC3 is greater than the distance d2 in which the second portion UDC2 is recessed relative to the third portion UDC3 in the direction away from the pixel opening.

[0142] With this design, the concave second part UDC2 can be used to increase the film layer step difference in the intersection area of ​​the pixel limiting part and the pixel opening. At the same time, the first protruding part UDC12 can be used to adjust the film layer morphology in the intersection area, thereby improving the isolation effect of the undercut structure on the upper film layer and ensuring that multiple light-emitting layers are isolated.

[0143] For example, continuing to refer to FIG7B, in the direction from the pixel defining portion toward the pixel opening, the spacing distance d0 between the raised portion UDC13 and the third portion UDC3 is greater than the spacing distance d6 between the first light-emitting sub-part 471 and the second light-emitting sub-part 472. Here, the spacing distance d6 between the first light-emitting sub-part 471 and the second light-emitting sub-part 472 refers to the separation width of the first light-emitting sub-part 471 and the second light-emitting sub-part 472 in the intersection area DS1 of the pixel defining portion and the pixel opening.

[0144] By increasing the spacing between the raised portion UDC13 and the third portion UDC3, the gap width between the first light-emitting portion 471 and the second light-emitting portion 472 can be increased, thereby reducing the lateral leakage current and improving the luminous efficiency of the display substrate.

[0145] For example, referring to FIG7B, the light-emitting functional layer 4 includes a plurality of first light-emitting functional sub-layers 411 located between the substrate 1 and the second light-emitting sub-layer 47. For example, the first light-emitting functional sub-layer 411 may include a plurality of film layers such as a hole injection layer, a first hole transport layer, a first light-emitting sub-layer, a first electron transport layer, a charge generation layer, and a second hole transport layer.

[0146] For example, at least a portion of the plurality of first light-emitting functional sublayers 411 includes a plurality of second protrusions T411 located above the first portion UDC12. The orthographic projection of the plurality of second protrusions T411 on the substrate at least partially overlaps with the orthographic projection of the first protrusion UDC12 on the substrate; and in a direction away from the substrate (e.g., the third direction Z), the plurality of second protrusions T411 have convex arc surfaces T4110 away from the substrate, the curvature of the convex arc surfaces T4110 of the plurality of second protrusions decreasing sequentially.

[0147] For example, the light-emitting functional layer 4 includes a plurality of second light-emitting functional sublayers 412 located on the side of the second light-emitting sublayer 47 away from the substrate. For example, the plurality of second light-emitting functional sublayers 412 may include a plurality of film layers such as a second electron transport layer and an electron injection layer.

[0148] For example, at least a portion of the plurality of second light-emitting functional sublayers 412 includes a plurality of recesses A412 located above the first portion UDC12. The plurality of recesses A412 have a plurality of concave surfaces A4120 close to the substrate. The orthographic projection of the plurality of recesses A412 on the substrate at least partially overlaps with the orthographic projection of the first protrusion UDC12 on the substrate; and the curvature of the concave surfaces of the plurality of recesses A4120 decreases sequentially in the direction away from the substrate.

[0149] For example, the second protrusion T4111 furthest from the substrate among the plurality of second protrusions T411 and the recess A4121 closest to the substrate among the plurality of recesses A412 are in direct contact.

[0150] With this design, a pinch structure can be formed by the second protrusions of multiple first light-emitting functional sub-layers 411 and the recesses of multiple second light-emitting functional sub-layers 412, so that the second light-emitting sub-layer is isolated in the intersection area DS1 of the undercut structure and the pixel opening, which helps to reduce the lateral leakage current of the display substrate and improve the low grayscale stability of the display substrate.

[0151] Figure 8A is a partial cross-sectional schematic diagram of a display substrate according to some embodiments of the present disclosure, and Figure 8B is a partial cross-sectional schematic diagram of a display substrate according to other embodiments of the present disclosure.

[0152] Exemplarily, in some embodiments of this disclosure, the first protrusion may also be wedge-shaped. For example, referring to FIG8A, the first cross-sectional shape includes a triangle.

[0153] For example, the first protrusion UDC12 includes a second surface UDC121 remote from the substrate. In the third direction Z, the second surface UDC121 is spaced apart from the surface 101 of the substrate 1 near the pixel defining layer by a second spacing distance H2. In the direction from the pixel defining portion PDL0 to the pixel opening VH, the second spacing distance H2 gradually increases. For example, the spacing distance H21 between a point O3 on the second surface UDC121 near the pixel opening and the surface 101 of the substrate 1 near the pixel defining layer is greater than the spacing distance H22 between a point O4 on the second surface UDC121 remote from the pixel opening and the surface 101 of the substrate 1 near the pixel defining layer.

[0154] For example, on the third direction Z, the vertex UDC120 of the first protrusion UDC12 that is furthest from the substrate is located on the side close to the pixel opening VH.

[0155] For example, the ratio of the second width D2 of the first protrusion to the first protrusion distance M1 is greater than or equal to 2 / 3.

[0156] For example, the second surface UDC121 has a first angle θ1 with the first planar direction X1. The first angle θ1 is greater than or equal to 45°, and the first planar direction X1 is perpendicular to the light emission direction of the display substrate.

[0157] For example, referring to Figures 7A and 8A, in the third direction Z, the first protrusion UDC12 has a first thickness h1, and the second light-emitting sublayer 47 has a third thickness h3. The ratio of the first thickness h1 to the third thickness h3 is greater than or equal to 1 / 2. It should be noted that the first thickness of the first protrusion here refers to the maximum thickness of the first protrusion in the third direction.

[0158] By adjusting the thickness and the first included angle of the first protrusion, the effect of the first protrusion on the morphology of the second light-emitting sub-layer can be improved, so that the second light-emitting sub-layer is isolated in the intersection area of ​​the pixel limiting part and the pixel opening, which helps to reduce the leakage probability of the display substrate and improve the luminous efficiency and low grayscale stability of the display substrate.

[0159] By designing a first protrusion in the undercut structure, not only can the separation effect between pixels be improved, but the separation requirement for the height of the pixel limiting layer can also be further reduced, thereby improving the flatness of the second electrode and improving the light emission uniformity of the display substrate.

[0160] In some embodiments of this disclosure, the first protrusion may also be prismatic in shape. For example, referring to FIG8B, the first cross-sectional shape includes a trapezoid.

[0161] For example, the first protrusion UDC12 has a first slope angle α1 on the side near the pixel opening VH, and a second slope angle α2 on the side away from the pixel opening VH, wherein the first slope angle α1 is smaller than the second slope angle α2.

[0162] This design can improve the flatness of the film layer in the pixel opening area while ensuring the isolation effect, thereby improving the light emission uniformity of the display substrate.

[0163] In the embodiments of this disclosure, in order to further analyze the display differences between the second light-emitting layer with and without isolation, a set of reference display substrates was designed. One set of display substrates (referred to as reference display substrate S1) adopts an undercut structure but does not have a first protrusion designed in the undercut structure, while the other set of display substrates (referred to as optimized display substrate S2) adopts an undercut structure, and the first part of the undercut structure is provided with a first protrusion.

[0164] FIG9A is a cross-sectional schematic diagram of a reference display substrate according to an embodiment of the present disclosure; FIG9B is a cross-sectional schematic diagram of an optimized display substrate according to an embodiment of the present disclosure; FIG10A is a partial light emission schematic diagram of the reference display substrate according to FIG9A; FIG10B is a partial light emission schematic diagram of the optimized display substrate according to FIG9B; FIG11A is a low grayscale viewing angle brightness diagram of the reference display substrate according to FIG9A; FIG11B is a low grayscale viewing angle brightness diagram of the optimized display substrate according to FIG9B.

[0165] For example, referring to FIG9A, when the undercut structure of the display substrate does not have a protrusion, the second light-emitting sublayer located in the intersection area of ​​the pixel limiting portion and the pixel opening is prone to distortion in this area, causing the second light-emitting sublayer to emit light at the distortion point; referring to FIG9B, when the first protrusion UDC12 is provided on the first part of the undercut structure of the display substrate, the morphology of multiple light-emitting functional film layers located in the intersection area of ​​the pixel limiting portion and the pixel opening can be adjusted by the padding effect of the first protrusion, so that the second light-emitting sublayer is isolated in this area.

[0166] Referring to Figures 10A and 10B, it can be observed that in the low grayscale state, when the second light-emitting sublayer is not isolated at the intersection of the pixel limiting portion and the pixel opening, the edge region of the light-emitting device is lit first, forming a ring-shaped light emission phenomenon as shown in Figure 10A. This is because leakage occurs in the part of the second light-emitting sublayer near the pixel limiting portion (i.e., the edge region), causing the second light-emitting sublayer in this region to be lit first, forming the ring-shaped light emission effect as shown in Figure 10A. This situation leads to a decrease in the overall luminous efficiency of the light-emitting device, and the low grayscale light emission state is not easy to control, which has an adverse effect on the display effect of the display product. However, when the second light-emitting sublayer is isolated at the intersection of the pixel limiting portion and the pixel opening, the edge leakage of the second light-emitting sublayer is alleviated or even eliminated, thereby enabling the entire light-emitting device at the pixel opening to be lit, achieving the whole-surface light emission effect as shown in Figure 10B. In this case, it is beneficial to improve the luminous efficiency of the light-emitting device, and the brightness adjustment of the light-emitting device is more controllable, thereby improving the low grayscale stability and controllability of the display substrate.

[0167] In the reference display substrate S1, referring to FIG9A, the first light-emitting sub-part 471 located above the pixel limiting part and the second light-emitting sub-part 472 located above the pixel opening VH are continuous. The second light-emitting sub-layer leaks current in the edge region of the pixel opening, causing abnormal attenuation of blue light brightness in the light-emitting device at low grayscale. For example, referring to FIG11A, the horizontal axis is the viewing angle and the vertical axis is the relative brightness. Blue light B has obvious warping around 10°. The brightness attenuation rate of blue light at low grayscale is slower than that of red light R and green light B. This may cause a bluish tint at low grayscale at small viewing angles, and the edge emission of blue sub-pixels reduces the light enhancement effect of the light extraction structure (e.g., a brightness enhancement prism) above the blue light.

[0168] In some embodiments of this disclosure, by designing a first protrusion, the second light-emitting sub-layer can be effectively isolated, which is beneficial to improving the consistency of the decay rate of different colors of light emission and improving the consistency of the light-emitting area of ​​multiple pixels.

[0169] For example, in the optimized display substrate S2, referring to FIG9B, the first light-emitting sub-part 471 located above the pixel limiting portion and the second light-emitting sub-part 472 located above the pixel opening VH are disconnected, and the light-emitting boundary is shifted towards the side closer to the pixel opening, so that the entire sub-pixel emits light. Referring to FIG11B, blue light has no warping at small viewing angles, and the brightness decay trends of red light R, green light G, and blue light B are similar, making it easier to control the low grayscale state of the display substrate, and the low grayscale state of the display substrate is more stable, which is beneficial to improving the display effect of the display substrate. In addition, the edge emission of blue light B at low grayscale is eliminated, which can improve the light enhancement effect of the light extraction structure above the blue light.

[0170] Referring to Figures 9A-11B, it can be observed that when the second light-emitting sublayer (e.g., the blue light-emitting layer) located in the intersection area of ​​the pixel limiting part and the pixel opening in the display substrate is isolated, the probability of leakage current in the display substrate is reduced, and the low grayscale light emission stability is significantly improved, which is beneficial to improving the stability of the display substrate, reducing power consumption, and improving the display effect.

[0171] Figure 12 is a comparison of the luminous efficiency of the blue light-emitting layer of the reference display substrate and the optimized display substrate.

[0172] For example, referring to FIG12, the horizontal axis represents current density and the vertical axis represents luminous efficiency. When the second light-emitting sub-layer (e.g., the blue light-emitting layer) located in the intersection region of the pixel definition portion and the pixel opening in the display substrate is blocked, the distortion of the blue light-emitting layer is reduced, and the low grayscale blue light is weakened. At the same current density, the luminous efficiency of the optimized display substrate S2 is improved by about 27% compared with the luminous efficiency of the reference display substrate S1, thereby enhancing the emission of blue light and improving the overall luminous efficiency of the display substrate.

[0173] Figure 13 is a comparison of the blue light spectra of the reference display substrate and the optimized display substrate.

[0174] For example, referring to FIG13, the horizontal axis is wavelength and the vertical axis is relative luminous intensity. When the second light-emitting sub-layer (e.g., the blue light-emitting layer) located in the intersection area of ​​the pixel definition portion and the pixel opening in the display substrate is blocked, the half width at half maximum (FWHM) of the blue light emitted by the blue light-emitting layer is narrowed (e.g., narrowed by about 40%), which can effectively suppress stray light at the edge, improve the purity of blue light, and thus improve the color gamut of the display product.

[0175] Figure 14 is a schematic diagram of the structure of a display device according to some embodiments of the present disclosure.

[0176] Optionally, embodiments of this disclosure also provide a display device. Referring to FIG14, the display device 300 may include the aforementioned display substrate 100. The display device may include, but is not limited to, any product or component with display functionality such as electronic paper, mobile phone, tablet computer, monitor, laptop computer, digital photo frame, and navigator. It should be understood that this display device has the same beneficial effects as the display substrate provided in the foregoing embodiments.

[0177] Figure 15 is a flowchart of a method for fabricating a display substrate according to an embodiment of the present disclosure.

[0178] By way of example, in some embodiments of this disclosure, a method for preparing a display substrate is also provided.

[0179] Referring to Figures 1, 6 and 15, the method for fabricating a display substrate may include the following steps S01-S03.

[0180] In step S01, a substrate 1 is provided.

[0181] In step S02, a first electrode material layer is formed on one side of the substrate, and a patterning process is performed on the first electrode material layer to form a first electrode layer 3. For example, multiple first electrodes 31 arranged in an array can be formed in the first electrode layer.

[0182] In step S03, a pixel defining material layer is formed on the side of the first electrode layer 3 away from the substrate, and a patterning process is performed on the pixel defining material layer to form a pixel defining layer PDL. The pixel defining layer PDL has multiple pixel openings VH, and includes a pixel defining portion PDL0 located between two adjacent pixel openings VH. The pixel defining portion PDL0 has an undercut structure UDC on the side facing the pixel opening. The undercut structure UDC includes a first portion UDC1, a second portion UDC2, and a third portion UDC3. The first portion UDC1 is located on the side of the second portion UDC2 closer to the substrate, and the first portion UDC1 protrudes relative to the third portion UDC3 in the direction towards the pixel opening. The third portion UDC3 is located on the side of the second portion UDC2 away from the substrate, and the second portion UDC2 is recessed relative to the third portion UDC3 in the direction away from the pixel opening. The first part UDC1 includes a main body UDC11, a raised part UDC13, and a first protrusion UDC12. The first protrusion UDC12 is located on the side of the raised part UDC13 away from the substrate. The first protrusion UDC12 protrudes relative to the main body UDC11 in a direction away from the substrate. The first protrusion UDC12 is located on the side of the first part UDC1 closer to the pixel opening VH.

[0183] For example, in step S03, a pixel defining material layer is formed on the side of the first electrode layer away from the substrate, and a patterning process is performed on the pixel defining material layer. The formation of the pixel defining layer may include the following steps S031-S034.

[0184] In step S031, a first insulating material is deposited on the side of the first electrode layer away from the substrate, and a patterning process is performed on the first insulating material.

[0185] In step S032, the steps of depositing the first insulating material and performing a patterning process on the first insulating material are repeated n times to form a first portion UDC12 containing the first protrusion UDC12, where n is a positive integer greater than or equal to 3. For example, n is 3, 4, or 5.

[0186] In step S033, a second insulating material is deposited and a patterning process is performed on the second insulating material to form the second part UDC2.

[0187] In step S034, a third insulating material is deposited and a patterning process is performed on the third insulating material to form a third portion UDC3, thereby forming an undercut structure UDC containing the first protrusion UDC12 in the pixel-defining layer.

[0188] For example, the insulating material in the pixel defining layer (e.g., a first insulating material, a second insulating material, and a third insulating material) may include one or more of silicon nitride, silicon oxide, or silicon oxynitride.

[0189] For example, the method for fabricating a display substrate may further include: after forming a pixel defining layer, continuing to form a light-emitting functional layer and a cathode on the side of the pixel defining layer away from the substrate.

[0190] While some embodiments of the general concept of this disclosure have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the general concept of this disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A display substrate, characterized in that, include: Substrate; A pixel defining layer disposed on the substrate, the pixel defining layer having a plurality of pixel openings defining a plurality of sub-pixels, the plurality of sub-pixels being arranged in an array along a first direction and a second direction, wherein the pixel defining layer includes a pixel defining portion located between two adjacent pixel openings, the pixel defining portion having an undercut structure on the side facing the pixel opening, the undercut structure including a first portion, a second portion and a third portion, the first portion being located on the side of the second portion closer to the substrate, the first portion protruding relative to the third portion in the direction facing the pixel opening, the third portion being located on the side of the second portion away from the substrate, the second portion being recessed relative to the third portion in the direction away from the pixel opening, wherein the first portion includes a main portion, a raised portion and a first protrusion, the first protrusion being located on the side of the raised portion away from the substrate, the first protrusion protruding relative to the main portion in the direction away from the substrate; The first protrusion is located on the side of the first portion near the pixel opening; the display substrate further includes a light-emitting functional layer disposed on the side of the pixel defining layer away from the substrate, the light-emitting functional layer including: a first light-emitting sub-layer; a charge-generating layer located on the side of the first light-emitting sub-layer away from the substrate; and a second light-emitting sub-layer located on the side of the charge-generating layer away from the substrate, the first light-emitting sub-layer being used to generate light of a first wavelength, the second light-emitting sub-layer being used to generate light of a second wavelength, the first wavelength being greater than the second wavelength, wherein the second light-emitting sub-layer includes a first light-emitting sub-part and a second light-emitting sub-part, the orthographic projection of the first light-emitting sub-part on the substrate at least partially overlaps with the orthographic projection of the pixel defining portion on the substrate, the orthographic projection of the second light-emitting sub-part on the substrate at least partially overlaps with the orthographic projection of the pixel opening on the substrate, and the first light-emitting sub-part and the second light-emitting sub-part are disconnected at the intersection region of the undercut structure and the pixel opening.

2. The display substrate according to claim 1, wherein, The light-emitting functional layer includes a first light-emitting functional portion located at the intersection of the undercut structure and the pixel opening. The first light-emitting functional portion includes a first surface away from the substrate. In a third direction, the first surface is spaced apart from the surface of the substrate near the pixel defining layer by a first spacing distance. In the direction from the pixel defining portion to the pixel opening, the first spacing distance gradually decreases. The third direction is parallel to the light emission direction of the display substrate. In the direction from the pixel defining portion to the pixel opening, the first light-emitting functional portion has a first width. The first portion protrudes a first protrusion distance relative to the third portion in the direction toward the pixel opening, and the first protrusion distance is greater than or equal to the first width.

3. The display substrate according to claim 2, wherein, In the direction from the pixel defining portion to the pixel opening, the first protrusion has a second width, and the ratio of the second width to the first protrusion distance is greater than or equal to 2 / 3.

4. The display substrate according to claim 3, wherein, In the third direction, the first protrusion has a first thickness, the second portion has a second thickness, and the first thickness is less than the second thickness.

5. The display substrate according to any one of claims 2-4, wherein, The first protrusion includes a second surface away from the substrate, the second surface being substantially parallel to the surface of the substrate near the pixel defining layer.

6. The display substrate according to any one of claims 2-4, wherein, The first protrusion includes a second surface away from the substrate. In the third direction, the second surface is spaced apart from the surface of the substrate near the pixel defining layer by a second spacing distance. The second spacing distance gradually increases in the direction from the pixel defining portion to the pixel opening.

7. The display substrate according to any one of claims 2-6, wherein, The first protrusion distance is greater than or equal to 0.1 micrometers.

8. The display substrate according to claim 7, wherein, The orthographic projection of the raised portion on the substrate does not overlap with the orthographic projection of the third portion on the substrate; and the distance between the raised portion and the third portion in the direction of the pixel defining portion toward the pixel opening is greater than the distance by which the second portion is recessed relative to the third portion in the direction away from the pixel opening.

9. The display substrate according to claim 8, wherein, In the direction from the pixel defining portion toward the pixel opening, the distance between the raised portion and the third portion is greater than the distance between the first light-emitting sub-part and the second light-emitting sub-part.

10. The display substrate according to claim 8, wherein, The charge generation layer includes a first charge generation sub-section located at the intersection of the undercut structure and the pixel opening. The first charge generation sub-section includes a third surface remote from the substrate, and the third surface has a convex arc surface protruding away from the substrate in a direction remote from the substrate.

11. The display substrate according to claim 10, wherein, The first charge-generating sub-part includes a first side away from the pixel opening, and the second light-emitting sub-part includes a second side away from the pixel opening, wherein, in the same sub-pixel, in the direction along the pixel defining portion toward the pixel opening, the first side is further away from the pixel opening than the second side.

12. The display substrate according to claim 11, wherein, The light-emitting functional layer includes a plurality of first light-emitting functional sub-layers located between the substrate and the second light-emitting sub-layer. At least a portion of the plurality of first light-emitting functional sub-layers includes a plurality of second protrusions located above the first portion. The orthographic projections of the plurality of second protrusions on the substrate at least partially overlap with the orthographic projections of the first protrusions on the substrate. In addition, in a direction away from the substrate, the plurality of second protrusions have convex arc surfaces away from the substrate, and the curvature of the convex arc surfaces of the plurality of second protrusions decreases sequentially.

13. The display substrate according to claim 12, wherein, The light-emitting functional layer includes a plurality of second light-emitting functional sublayers located on the side of the second light-emitting sublayer away from the substrate. At least a portion of the plurality of second light-emitting functional sublayers includes a plurality of recesses located above the first portion. The plurality of recesses have a plurality of concave surfaces close to the substrate. The orthographic projections of the plurality of recesses on the substrate at least partially overlap with the orthographic projections of the first protrusion on the substrate. The curvature of the concave surfaces of the plurality of recesses decreases sequentially in the direction away from the substrate.

14. The display substrate according to claim 13, wherein, The second protrusion furthest from the substrate among the plurality of second protrusions and the recess closest to the substrate among the plurality of recesses are in direct contact.

15. The display substrate according to any one of claims 1-14, wherein, On a plane parallel to the light emission direction of the display substrate, the first protrusion has a first cross-sectional shape, which includes at least one of a rectangle, a trapezoid, and a triangle.

16. The display substrate according to any one of claims 8-14, wherein, In the third direction, the first protrusion has a first thickness, the second light-emitting sublayer has a third thickness, and the ratio of the first thickness to the third thickness is greater than or equal to 1 / 2.

17. The display substrate according to claim 6, wherein, The second surface has a first angle with the first plane direction, the first angle being greater than or equal to 45°, and the first plane direction is perpendicular to the light emission direction of the display substrate.

18. The display substrate according to claim 4, wherein, The first protrusion has a first slope angle on the side near the pixel opening and a second slope angle on the side away from the pixel opening, wherein the first slope angle is smaller than the second slope angle.

19. A display device, characterized in that, Includes the display substrate as described in any one of claims 1-18.

20. A method for preparing a display substrate, characterized in that, include: Provide substrates; A first electrode material layer is formed on one side of the substrate, and a patterning process is performed on the first electrode material layer to form the first electrode layer; A pixel defining material layer is formed on the side of the first electrode layer away from the substrate, and a patterning process is performed on the pixel defining material layer to form a pixel defining layer. The pixel defining layer has a plurality of pixel openings, and includes a pixel defining portion located between two adjacent pixel openings. The pixel defining portion has an undercut structure on the side facing the pixel opening. The undercut structure includes a first portion, a second portion, and a third portion. The first portion is located on the side of the second portion closer to the substrate, and the first portion protrudes relative to the third portion in a direction towards the pixel opening. The third portion is located on the side of the second portion away from the substrate, and the second portion is recessed relative to the third portion in a direction away from the pixel opening. The first portion includes a main body portion, a raised portion, and a first protrusion portion. The first protrusion portion is located on the side of the raised portion away from the substrate. The portion protrudes relative to the main body portion in a direction away from the substrate; and the first protrusion is located on the side of the first portion near the pixel opening, wherein forming a pixel defining material layer on the side of the first electrode layer away from the substrate and performing a patterning process on the pixel defining material layer to form a pixel defining layer includes: depositing a first insulating material on the side of the first electrode layer away from the substrate and performing a patterning process on the first insulating material; repeating the steps of depositing the first insulating material and performing a patterning process on the first insulating material n times to form a first portion including the first protrusion, where n is a positive integer greater than or equal to 3; depositing a second insulating material and performing a patterning process on the second insulating material to form a second portion; and depositing a third insulating material and performing a patterning process on the third insulating material to form a third portion to form an undercut structure including the first protrusion in the pixel defining layer.

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