Display substrate, preparation method thereof and display device

Abstract

The invention provides a display substrate. The display substrate comprises a substrate body; the plurality of organic light-emitting diodes are located on the substrate and comprise first electrodes, hole injection layers, light-emitting layers and second electrodes; the pixel defining layer is located on the substrate and defines a plurality of pixel openings, and the orthographic projections of the first electrodes of the adjacent organic light emitting diodes on the substrate are at least partially overlapped with the orthographic projections of the adjacent pixel openings on the substrate respectively; the orthographic projections of the first electrodes of the adjacent organic light emitting diodes on the substrate are spaced; the orthographic projections of the hole injection layers of the adjacent organic light emitting diodes on the substrate respectively cover the orthographic projections of the adjacent pixel openings on the substrate, and the orthographic projections of the hole injection layers of the adjacent organic light emitting diodes on the substrate are connected with each other; the first electrode comprises an anode modification layer which is located on the side, facing the hole injection layer, of the first electrode, and the anode modification layer comprises a p-type oxide doped anode material.

Description

Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a display substrate and a preparation method thereof, and a display device. Background Art

[0002] Organic Light Emitting Diode (OLED) panels have self-luminous properties, can achieve infinite contrast, present the purest black and richer color levels, and have ultra-thin design, excellent picture quality, fast response, energy saving and high efficiency, strong flexibility and good shock resistance. In the process of preparing OLED panels, each OLED device has an independent organic light-emitting layer to emit specific light as needed. Other film layers, such as hole injection layer (HIL), electron transport layer (ETL), cathode (Cathode), etc. are usually common layers, that is, the HIL, ETL and cathode of multiple OLED devices are all integrated structures. Carriers will be transported laterally in the common layer, generating lateral current, resulting in poor crosstalk. The HIL is the most seriously affected. In order to improve the impact of HIL on crosstalk, the concentration of p-type doping material (p-dopant) in HIL is generally reduced. However, the reduction of p-dopant concentration leads to an increase in the operating voltage of the device, resulting in increased power consumption, poor reliability and other problems. Targeted improvement of these display problems is a topic that R&D personnel continue to pay attention to.

[0003] The above information disclosed in this section is only for understanding the background of the inventive concept of the present disclosure and therefore the above information may contain information that does not constitute the prior art. Summary of the invention

[0004] In order to solve at least one aspect of the above problems, embodiments of the present disclosure provide a display substrate and a method for manufacturing the same, and a display device.

[0005] According to one aspect of an embodiment of the present disclosure, a display substrate is provided, comprising:

[0006] substrate substrate;

[0007] a plurality of organic light emitting diodes, located on the base substrate, the organic light emitting diodes comprising a first electrode, a hole injection layer, a light emitting layer, and a second electrode; and

[0008] A pixel defining layer is located on the base substrate, and the pixel defining layer defines a plurality of pixel openings.

[0009] The orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate at least partially overlap with the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate are spaced apart;

[0010] The orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate respectively cover the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate are connected to each other; and

[0011] The first electrode comprises:

[0012] An anode modification layer is located on a side of the first electrode facing the hole injection layer, and the anode modification layer comprises an anode material doped with a p-type oxide.

[0013] In some embodiments, the hole injection layer includes a p-type doped material.

[0014] In some embodiments, at least a portion of the anode modification layer is located in the pixel opening, and an orthographic projection of the anode modification layer on the base substrate covers an orthographic projection of the first electrode on the base substrate.

[0015] In some embodiments, the energy level of the p-type oxide ranges from -4.5 eV to -7.5 eV; and / or,

[0016] The material of the p-type oxide is selected from at least one of MoO3, NiO, and Cu2O.

[0017] In some embodiments, the ratio of the thickness of the first electrode to the thickness of the anode modification layer is in the range of 2 to 10; and / or,

[0018] The doping concentration of the p-type oxide in the anode modification layer is 5% to 30%.

[0019] In some embodiments, the hole injection layer includes a plurality of hole injection sublayers stacked in sequence, each of the hole injection sublayers including a hole transport material and a p-type doping material;

[0020] Along the light emitting direction of the display substrate, the concentration of the p-type doping material in the plurality of hole injection sublayers increases sequentially.

[0021] In some embodiments, the doping concentration of the p-type doping material ranges from 0.5 to 2%;

[0022] The number of the hole injection sublayers is 2 to 5.

[0023] In some embodiments, the ratio of the thickness of the hole injection layer to the thickness of the first electrode is in the range of 0.5 to 4;

[0024] The thickness of the hole injection layer is

[0025] Another aspect of the embodiments of the present disclosure provides a display substrate, including:

[0026] substrate substrate;

[0027] A plurality of organic light emitting diodes, located on the base substrate, the organic light emitting diodes comprising a first electrode, a hole injection layer, a light emitting layer and a second electrode, wherein the hole injection layer comprises a p-type doping material;

[0028] A pixel defining layer is located on the base substrate, and the pixel defining layer defines a plurality of pixel openings.

[0029] The orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate at least partially overlap with the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate are spaced apart;

[0030] The orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate respectively cover the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate are connected to each other; and

[0031] The display substrate further comprises:

[0032] An n-type material layer is located on a side of the pixel defining layer away from the base substrate, an orthographic projection of the n-type material layer on the base substrate at least partially overlaps with an orthographic projection of the hole injection layer on the base substrate, at least a portion of the n-type material layer contacts at least a portion of the hole injection layer, and a pn junction is formed at a contact interface between the n-type material layer and the hole injection layer.

[0033] In some embodiments, the orthographic projection of the n-type material layer on the substrate is located between orthographic projections of adjacent pixel openings on the substrate; and / or,

[0034] The n-type material layer is located between the pixel definition layer and the hole injection layer.

[0035] In some embodiments, the ratio of the thickness of the hole injection layer to the thickness of the n-type material layer is in a range of 2 to 60; and / or,

[0036] The n-type material layer is at least one of Yb / Li-doped organic electron transport material, ZnO and AgO.

[0037] Another aspect of the embodiments of the present disclosure provides a display device, comprising a display substrate according to any one of the above items.

[0038] Another aspect of the embodiments of the present disclosure provides a method for preparing a display substrate, the method comprising the following steps:

[0039] Forming a pixel defining layer on the base substrate, wherein the pixel defining layer defines a plurality of pixel openings;

[0040] A first electrode is formed on a side of the pixel defining layer away from the base substrate; the orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate at least partially overlap with the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate are spaced apart;

[0041] forming an anode modification layer on a side of the first electrode away from the substrate, wherein the anode modification layer comprises an anode material doped with p-type oxide;

[0042] A hole injection layer is formed on a side of the anode modification layer away from the base substrate; the orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate respectively cover the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate are connected to each other;

[0043] forming a light-emitting layer on a side of the hole injection layer away from the base substrate;

[0044] A second electrode is formed on a side of the light emitting layer away from the base substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Other objects and advantages of the present disclosure will be apparent from the following description of the present disclosure with reference to the accompanying drawings and will help to have a comprehensive understanding of the present disclosure.

[0046] Figure 1 An energy level diagram of an OLED device is schematically shown.

[0047] Figure 2 Schematic diagram of the work function of ITO / hole transport and p-type doping materials is shown schematically.

[0048] Figure 3A The relationship between brightness and lifetime at different p-dopant doping concentrations is schematically shown.

[0049] Figure 3B The relationship between the device operating voltage increase and time at different p-dopant doping concentrations is schematically shown.

[0050] Figure 4A is a cross-sectional view of a display substrate along a direction parallel to a light emitting direction according to some exemplary embodiments of the present disclosure.

[0051] Figure 4B yes Figure 4A A simplified structural diagram of .

[0052] Figure 4C is a plan view of a display substrate according to some exemplary embodiments of the present disclosure.

[0053] Figure 4D is a graph showing the relationship between operating voltage and time according to some exemplary embodiments of the present disclosure.

[0054] Figure 5A is a cross-sectional view of a display substrate including a plurality of hole injection sublayers according to some other exemplary embodiments of the present disclosure.

[0055] Figure 5B FIG. 4 is a schematic diagram of work functions of hole injection layers with different p-dopant doping concentrations according to other exemplary embodiments of the present disclosure.

[0056] Figure 5C FIG. 4 is a graph showing a relationship between operating voltage and time according to some other exemplary embodiments of the present disclosure.

[0057] Figure 6 The schematic diagram schematically shows the crosstalk problem of OLED devices caused by excessive p-dopant doping concentration in the related art.

[0058] Fig. 7A is a cross-sectional view of a display substrate along a direction parallel to a light emitting direction according to some exemplary embodiments of the present disclosure.

[0059] Figure 7B yes Fig. 7A A simplified structural diagram of .

[0060] Figure 7C is a plan view of a display substrate according to some exemplary embodiments of the present disclosure.

[0061] Fig.7D FIG. 4 is a schematic diagram of charge distribution of a PN junction according to some exemplary embodiments of the present disclosure.

[0062] Figure 8A to Figure 8B A schematic diagram of the structure of a display device provided in an embodiment of the present disclosure.

[0063] Fig. 9 is a flow chart of a method for preparing a display substrate according to an exemplary embodiment of the present disclosure.

[0064] It should be noted that, for the sake of clarity, in the drawings used to describe the embodiments of the present disclosure, the sizes of layers, structures or regions may be enlarged or reduced, that is, these drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0065] The technical solution of the present disclosure is further specifically described below through examples and in conjunction with the accompanying drawings. In the specification, the same or similar figure numbers indicate the same or similar parts. The following description of the embodiments of the present disclosure with reference to the accompanying drawings is intended to explain the overall inventive concept of the present disclosure and should not be construed as a limitation of the present disclosure.

[0066] In addition, in the following detailed description, for the purpose of explanation, numerous specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details.

[0067] It should be understood that, although the terms first, second, etc. can be used here to describe different elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiment, the first element can be named as the second element, and similarly, the second element can be named as the first element. The term "and / or" as used herein includes any combination and all combinations of one or more related listed items.

[0068] It should be understood that when an element or layer is referred to as "formed on" another element or layer, the element or layer can be directly or indirectly formed on another element or layer. That is, for example, there may be an intermediate element or intermediate layer. On the contrary, when an element or layer is referred to as "directly formed on" another element or layer, there is no intermediate element or intermediate layer. Other words used to describe the relationship between elements or layers should be interpreted in a similar manner (for example, "between" and "directly between", "adjacent" and "directly adjacent", etc.). In addition, the X-axis, Y-axis and Z-axis are not limited to the three axes of the rectangular coordinate system, and can be interpreted in a broader sense. For example, the X-axis, Y-axis and Z-axis may be perpendicular to each other, or may represent different directions that are not perpendicular to each other. For the purpose of this disclosure, "at least one of X, Y and Z" and "at least one selected from the group consisting of X, Y and Z" can be interpreted as only X, only Y, only Z, or any combination of two or more of X, Y and Z such as XYZ, XY, YZ and XZ.

[0069] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. It will also be understood that when the terms "comprise" and / or "include" are used herein, the description indicates the presence of the features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0070] The basic structure of an OLED device includes anode (Anode) / hole injection layer (HIL) / hole transport layer (HTL) / luminescent layer (EML) / electron transport layer (ETL) / electron injection layer (EIL) / cathode (Cathode, CTD). An OLED device may also include a light-emitting functional layer (Prime), a hole blocking layer (HBL), a capping layer (CPL), etc. Among these layers, energy level matching is crucial to the performance of organic electroluminescent devices.

[0071] Figure 1 The schematic diagram of an OLED device energy level is shown. In an OLED device, different organic layers (such as hole injection layer, hole transport layer, electron transport layer and electron injection layer) have different energy levels, and the energy level arrangement of these layers is crucial for the injection and transport of electrons and holes. Figure 1 As shown, the OLED device structure includes ITO / HIL / HTL / Prime / EML / HBL / ETL / CTD, each rectangle represents the energy level of the corresponding layer, the height of the bottom side of the rectangle represents the HOMO energy level of the layer, and the height of the top side of the rectangle represents the LUMO energy level of the layer. For example, the HOMO energy level of ITO needs to be aligned or close to the HOMO energy level of HIL to facilitate hole injection; similarly, the LUMO energy level of CTD needs to be aligned or close to the LUMO energy level of ETL to facilitate electron injection. The work function of ITO is higher (-4.95eV), and the energy level of HTL is lower (-5.3eV). The energy level barrier between the two is large, which is not conducive to the transmission of holes; while the use of HIL is conducive to reducing the energy level difference between ITO and HTL and promoting hole injection. Doping p-type doping material (p-dopant) in HIL can further adjust the degree of energy level matching and improve the hole injection efficiency, thereby improving the performance of OLED devices.

[0072] Figure 2 Schematic diagram of the work function of ITO / hole transport and p-type doping materials. For example, 0.5% HI in the horizontal axis represents 0.5% p-dopant doping in the hole injection layer, and the second rectangular column represents the hole injection layer and hole transport layer doped with 0.5% p-dopant ( Figure 2The energy level corresponding to HT) is expressed in , and so on. Figure 2 It can be seen that within the doping concentration range of 0-2%, the higher the p-dopant doping concentration, the more conducive it is to hole injection.

[0073] However, the inventors found that too high a p-dopant doping concentration can cause crosstalk problems in OLED devices; a low p-dopant doping concentration (eg 0.5%) can cause problems such as increased operating voltage and abnormal brightness, affecting the display performance of the OLED.

[0074] Table 1 shows the device performance at a current density of 15 mA / cm at different p-dopant doping concentrations (0-2%). 2 The test results of the operating voltage (op.V) and optical performance under the conditions; among them, Cd / m 2 represents light intensity, Cd / A represents brightness, CIEx and CIEy represent coordinates in the color space, E / y represents the value of current efficiency divided by CIEy, Peak represents the peak point of luminescence, and FWHM represents the half-peak width of luminescence. As can be seen from Table 1, the higher the p-dopant doping concentration, the lower the operating voltage of the device, while the optical performance of the device is almost unaffected.

[0075] Table 1

[0076]

[0077] Figure 3A The relationship between brightness and lifetime at different p-dopant doping concentrations (0-2%) is schematically shown. Figure 3B The relationship between the device operating voltage increase (ΔV) and time at different p-dopant doping concentrations (0-2%) is schematically shown.

[0078] Depend on Figure 3A It can be seen that when the doping concentration of p-dopant is lower than 0.6%, the OLED device has abnormal brightness, that is, the brightness increases abnormally at the beginning of the life test. Figure 3B It can be seen that when the doping concentration of p-dopant is lower than 0.6%, the device operating voltage increases significantly, leading to problems such as increased power consumption and reduced reliability.

[0079] On the one hand, in order to solve the problem of abnormal brightness and increased operating voltage of OLED devices when the doping concentration of p-dopant is low, an embodiment of the present disclosure provides a display substrate.

[0080] Figure 4A is a cross-sectional view of a display substrate according to some exemplary embodiments of the present disclosure in a direction parallel to a light emitting direction, Figure 4B yes Figure 4A A simplified schematic diagram of Figure 4C is a plan view of a display substrate according to some exemplary embodiments of the present disclosure, for example, Figure 4A It can be a display substrate along Figure 4C A cross-sectional view taken along line AA'. Figure 4D is a graph showing the relationship between operating voltage and time according to some exemplary embodiments of the present disclosure.

[0081] In an embodiment of the present disclosure, a display substrate 10 includes: a base substrate 11; a plurality of organic light emitting diodes 14 located on the base substrate 11, the organic light emitting diodes 14 including a first electrode 141, a hole injection layer 142, a light emitting layer 143 and a second electrode 145; and a pixel defining layer 13 located on the base substrate 11, the pixel defining layer 13 defining a plurality of pixel openings 131, wherein the orthographic projections of the first electrodes 141 of adjacent organic light emitting diodes 14 on the base substrate 11 respectively overlap with the orthographic projections of the adjacent pixel openings 131 on the base substrate 11 at least partially, and the orthographic projections of the first electrodes 141 of adjacent organic light emitting diodes 14 on the base substrate 11 are spaced apart; the orthographic projections of the hole injection layers 142 of adjacent organic light emitting diodes 14 on the base substrate 11 respectively cover the orthographic projections of the adjacent pixel openings 131 on the base substrate 11, and the orthographic projections of the hole injection layers 142 of adjacent organic light emitting diodes 14 on the base substrate 11 are connected to each other.

[0082] According to some exemplary embodiments, the base substrate 11 can be a rigid substrate, such as a glass substrate, a silicon substrate, etc., or can be formed of a flexible material with excellent heat resistance and durability, such as polyimide (PI), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene, polyacrylate, polyarylate, polyetherimide, polyethersulfone, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polysulfone (PSF), polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), cycloolefin polymer (COP) and cycloolefin copolymer (COC), etc.

[0083] In an exemplary embodiment of the present disclosure, a driving circuit layer 12 is included on the base substrate 11. The driving circuit layer 12 may include a plurality of thin film transistors and storage capacitors forming a pixel driving circuit. In an exemplary embodiment, the driving circuit layer 12 may include, for example, a first insulating layer, a semiconductor layer, a second insulating layer, a first gate metal layer, a third insulating layer, a second gate metal layer, a fourth insulating layer, a source-drain metal layer, and a planar layer sequentially disposed on the base substrate 11.

[0084] Exemplarily, the organic light emitting layer 143 is one of a red light emitting layer, a green light emitting layer, a blue light emitting layer or a white light emitting layer to form a red sub-pixel R, a green sub-pixel G, a blue sub-pixel B or a white sub-pixel.

[0085] Exemplarily, the first electrode 141 is an anode, and the second electrode 145 is a cathode. The materials of the first electrode 141 and the second electrode 145 may be, for example, at least one of a metal and ITO. For example, the second electrode 145 may be an ITO layer of a display substrate. When the ITO layer is used as an electrode layer of a display substrate, it has good electrical conductivity and high transmittance to visible light, and can conduct current without blocking the light emitted by the light-emitting layer 143.

[0086] The pixel defining layer 13 is disposed on the side of the driving circuit layer 12 away from the base substrate 11. The pixel defining layer 13 has a plurality of pixel openings 131 spaced apart from each other. The pixel openings 131 are used to form corresponding sub-pixel regions such as red sub-pixel R, green sub-pixel G, and blue sub-pixel B. The first electrode 141 is disposed at the bottom of the pixel opening 131. The light-emitting layer 143 is disposed on the first electrode 141 in the pixel opening 131. The second electrode 145 is disposed on the pixel defining layer 13. The coverage area of ​​the second electrode 145 includes the pixel opening 131 and the non-pixel opening area. In this way, the first electrode 141 and the second electrode 145 can drive the light-emitting layer 143 to emit light when a voltage is connected.

[0087] For example, the pixel defining layer 13 is located on the side of the flat layer away from the base substrate 11, and the first electrode 141 can contact the circuits or conductive traces inside the driving circuit layer 12 through multiple vias arranged in the flat layer, so that the organic light-emitting diodes 14 can be driven separately through the driving circuit layer 12 to achieve the display function.

[0088] In some embodiments of the present disclosure, the hole injection layer 142 is disposed between the first electrode 141 and the light-emitting layer 143 to reduce the interface barrier between the first electrode 141 and the light-emitting layer 143 and improve the hole injection capability from the first electrode 141 to the light-emitting layer 143. The hole injection layer 142 includes a p-type doping material to further improve the hole injection capability; wherein the concentration of the p-type doping material is less than 0.6%.

[0089] In some embodiments of the present disclosure, the first electrode 141 includes: an anode modification layer 1411 , the anode modification layer 1411 is located on a side of the first electrode 141 facing the hole injection layer 142 , and the anode modification layer 1411 includes a p-type oxide-doped anode material.

[0090] By adding an anode modification layer 1411 on the surface of the first electrode 141, the hole injection ability is further improved by using p-type oxide, and the interface energy level between the first electrode 141 and the hole injection layer 142 is regulated to ensure that holes can be effectively injected into the hole injection layer 142, thereby improving the problem of increased device operating voltage.

[0091] In some embodiments of the present disclosure, at least a portion of the anode modification layer 1411 is located in the pixel opening 131 , and the orthographic projection of the anode modification layer 1411 on the base substrate 11 covers the orthographic projection of the first electrode 141 on the base substrate 11 .

[0092] Reference Figure 4A The anode modification layer 1411 covers the surface of the first electrode 141 , and the anode modification layer 1411 is located between the first electrode 141 and the hole injection layer 142 to adjust the interface energy level therebetween.

[0093] In some embodiments of the present disclosure, the energy level range of the p-type oxide is -4.5 eV to -7.5 eV; and / or the material of the p-type oxide is selected from at least one of MoO3, NiO, and Cu2O.

[0094] P-type oxide is a type of metal oxide. This type of metal oxide usually has a slightly larger number of oxygen atoms. The atomic ratio of metal to oxygen elements is not strictly in accordance with the atomic ratio in the chemical formula. The structural defects in the oxide are metal ion vacancies. Therefore, the carriers in the p-type oxide semiconductor are holes. P-type oxide doping is beneficial to improving the hole injection capability.

[0095] In some embodiments of the present disclosure, the ratio of the thickness of the first electrode 141 to the thickness of the anode modification layer 1411 is in a range of 2 to 10; and / or the doping concentration of the p-type oxide in the anode modification layer 1411 is in a range of 5% to 30%.

[0096] The thickness of the anode modification layer 1411 is thinner than that of the first electrode 141, and can be prepared by magnetron sputtering (PVD). The main body material of the anode modification layer 1411 is the same as that of the first electrode 141, and the doping concentration of the p-type oxide is in the range of 5% to 30%, which is conducive to better energy level regulation.

[0097] In some embodiments of the present disclosure, the organic light emitting diode 14 may further include various functional layers such as a hole transport layer (HTL), an electron injection layer (EIL), an electron transport layer (HTL) 144, and a hole blocking layer (HBL), which work together to enable the OLED device to emit light under an applied voltage. Electrons and holes are injected from the cathode and anode, respectively, move to the light emitting layer through their respective transport layers, recombine in the light emitting layer and release energy to generate photons, thereby achieving light emission.

[0098] Exemplarily, the organic light emitting diode 14 comprises a structure 1:

[0099] ITO / MoO3: ITO / HIL / HT / Prime / EML / HBL / ETL / EIL / CTD / CPL; ITO is the anode; MoO3: ITO is used as the anode modification layer; HIL is located between the anode and the hole transport layer to reduce the energy level difference between the anode and the hole transport layer; HT has a high hole mobility to facilitate the transport of holes; Prime is a luminescent functional material located between the hole transport layer and the main material; EML is the luminescent layer, where electrons and holes recombine to form excitons, which emit photons through radiation recombination; HBL prevents holes from entering ETL, thereby reducing non-radiative recombination and improving the luminescence efficiency and life of the device; ETL has a high electron mobility to facilitate the transport of electrons; EIL is located between the luminescent layer and the cathode to reduce the energy level difference between the cathode and the electron transport layer and promote the injection of electrons; CTD is the cathode; CPL is a covering layer, which is an organic film located on the cathode of the OLED. The thickness of ITO is The thickness of MoO3:ITO is The ratio of MoO3:ITO is 1:9.

[0100] The organic light emitting diode 14 comprises a structure 2:

[0101] ITO / MoO3: ITO / HIL / HT / Prime / EML / HBL / ETL / EIL / CTD / CPL; among which, the thickness of ITO is The thickness of MoO3:ITO is The ratio of MoO3:ITO is 2:8.

[0102] Comparative structure (Ref):

[0103] ITO / HIL / HT / Prime / EML / HBL / ETL / EIL / CTD / CPL.

[0104] Table 2 shows the performance of the devices with structure 1 and structure 2 at a current density of 15 mA / cm 2 The test results of the operating voltage (op.V) and optical performance under the conditions. As shown in Table 2, the operating voltages of the anode modification layer composed of MoO3:ITO, structure 1 and structure 2 are lower than that of the comparative example, and the optical performance of the device is almost unaffected.

[0105] Table 2

[0106]

[0107] Reference Figure 4D , structure 1 corresponds to the polyline of condition 1, and structure 2 corresponds to the polyline of condition 2. Figure 4D It can be seen that the problem of greatly increased working voltage of the devices of Structure 1 and Structure 2 with the addition of the anode modification layer is significantly improved.

[0108] Figure 5A is a cross-sectional view of a display substrate including a plurality of hole injection sublayers according to some other exemplary embodiments of the present disclosure. Figure 5B FIG. 4 is a schematic diagram of work functions of hole injection layers with different p-dopant doping concentrations according to other exemplary embodiments of the present disclosure. Figure 5C FIG. 4 is a graph showing a relationship between operating voltage and time according to some other exemplary embodiments of the present disclosure.

[0109] In some embodiments of the present disclosure, the hole injection layer 142 includes a plurality of hole injection sublayers stacked in sequence, each of which includes a hole transport material and a p-type doping material; along the light emitting direction of the display substrate, the concentration of the p-type doping material in the plurality of hole injection sublayers increases in sequence. The doping concentration of the p-type doping material ranges from 0.5 to 2%; and the number of hole injection sublayers is 2 to 5 layers.

[0110] Exemplarily, referring to Figure 5, the hole injection layer 142 includes three sublayers: a hole injection sublayer 1421, a hole injection sublayer 1422 and a hole injection sublayer 1423. The concentration of the p-type doping material in the hole injection sublayer 1421 is 0.5%, the concentration of the p-type doping material in the hole injection sublayer 1422 is 0.75%, and the concentration of the p-type doping material in the hole injection sublayer 1423 is 1%.

[0111] In some embodiments of the present disclosure, the ratio of the thickness of the hole injection layer 142 to the thickness of the first electrode 141 is in the range of 0.5 to 4; the thickness of the hole injection layer 142 is

[0112] The thickness of the first electrode 141 is If the thickness of the first electrode 141 is too thin, it is easy to cause leakage of the OLED device; if the thickness of the first electrode 141 is too thick, the first electrode material absorbs the light of the device strongly, resulting in low luminous efficiency. The thickness of the hole injection layer 142 is about If the thickness of the hole injection layer 142 is too thin, the hole injection effect will be unsatisfactory; if the thickness of the hole injection layer 142 is too thick, the p-dopant doped therein will strongly absorb light, resulting in low luminous efficiency.

[0113] Exemplarily, the organic light emitting diode 14 includes a structure 3:

[0114] ITO / HIL1 / HIL2 / HIL3 / HT / Prime / EML / HBL / ETL / EIL / CTD / CPL; among which, the thickness of ITO is The thickness of HIL1 / HIL2 / HIL3 is The doping concentrations of p-dopant in HIL1 / HIL2 / HIL3 are 0.5%, 0.75% and 1.0% Pd, respectively.

[0115] Comparative structure (Ref):

[0116] ITO / HIL / HT / Prime / EML / HBL / ETL / EIL / CTD / CPL.

[0117] Among them, the thickness of ITO is The thickness of HIL is The doping concentration of p-dopant is 0.5%.

[0118] Reference Figure 5B , the work functions of HIL1 / HIL2 / HIL3 increase successively, which reduces the energy level difference between the interfaces and is beneficial to the injection of holes into the hole injection layer 142.

[0119] Table 3 shows that the device of structure 3 has a current density of 15 mA / cm 2 The test results of the operating voltage (op.V) and optical performance under the conditions. As shown in Table 3, the operating voltage of the hole injection layer composed of hole injection sublayers with different p-dopant doping concentrations in structure 3 is lower than that of the comparative example, and the optical performance of the device is almost unaffected.

[0120] Table 3

[0121]

[0122] Reference Figure 5C , structure 3 corresponds to the broken line of condition 3. Figure 5C It can be seen that the problem of greatly increased device operating voltage in structure 3 using a hole injection layer with multiple hole injection sublayers is significantly improved.

[0123] In the above embodiment, when the doping concentration of p-dopant is lower than 0.6%, crosstalk can be effectively improved, but the problem of significantly increased operating voltage will occur; and when the doping concentration of p-dopant is greater than or equal to 0.6%, for example, 2%, obvious crosstalk will occur. It can be understood that 0.6% is only a relative limit value, and the limit value may be different in different OLED devices.

[0124] Figure 6The schematic diagram schematically shows the crosstalk problem of OLED devices caused by excessive p-dopant doping concentration in the related art.

[0125] Reference Figure 6 , the display substrate 20 includes a first electrode 11, a driving circuit layer 12, a first electrode 141, a hole injection layer 142, and a light-emitting layer 143. The OLED pixel includes a red (R) OLED pixel and a blue (B) OLED pixel. The red OLED pixel and the blue OLED pixel have independent light-emitting layers 143, respectively, and the hole injection layer 142 is a common layer. The display substrate displays a first picture such as a blue picture, and the first electrode 11 of the B pixel injects holes. At this time, the hole concentration of the hole injection layer 142 is uneven, and the hole concentration of the B pixel is greater than the hole concentration of the R pixel. Since the hole injection layer 142 has good conductivity, the holes in the B pixel area will diffuse to the R pixel area, so that the charge is transferred horizontally in the hole injection layer, and a horizontal current appears, causing the R pixel to light up slightly, resulting in poor crosstalk.

[0126] On the other hand, in order to solve the problem of crosstalk in OLED devices when the doping concentration of p-dopant is high, an embodiment of the present disclosure provides a display substrate.

[0127] Fig. 7A is a cross-sectional view of a display substrate according to some exemplary embodiments of the present disclosure in a direction parallel to a light emitting direction, Figure 7B yes Fig. 7A A simplified schematic diagram of Figure 7C is a plan view of a display substrate according to some exemplary embodiments of the present disclosure, for example, Fig. 7A It can be a display substrate along Figure 7C A cross-sectional view taken along line BB'. Fig.7D FIG. 4 is a schematic diagram of charge distribution of a PN junction according to some exemplary embodiments of the present disclosure. Figure 7A-7C Some structures of the display substrate shown can refer to the above Figure 4A-4C Moreover, the same or similar components or structures are represented by the same reference numerals.

[0128] In some embodiments of the present disclosure, the display substrate 30 includes: a base substrate 11; a plurality of organic light emitting diodes 14, located on the base substrate 11, the organic light emitting diodes 14 including a first electrode 141, a hole injection layer 142, a light emitting layer 143 and a second electrode 145, wherein the hole injection layer 142 includes a p-type doping material; a pixel defining layer 13, located on the base substrate 11, the pixel defining layer 13 defines a plurality of pixel openings 131, wherein the orthographic projections of the first electrodes 141 of adjacent organic light emitting diodes 14 on the base substrate 11 are at least partially overlapped with the orthographic projections of the adjacent pixel openings 131 on the base substrate 11, and ... first electrodes 141 of adjacent organic light emitting diodes 14 on the base substrate 11. The projections are separated; the orthographic projections of the hole injection layers 142 of adjacent organic light emitting diodes 14 on the substrate substrate 11 respectively cover the orthographic projections of adjacent pixel openings 131 on the substrate substrate 11, and the orthographic projections of the hole injection layers 142 of adjacent organic light emitting diodes 14 on the substrate substrate 11 are connected to each other; and the display substrate also includes: an n-type material layer 15, which is located on the side of the pixel defining layer 13 away from the substrate substrate 11, the orthographic projection of the n-type material layer 15 on the substrate substrate 11 is at least partially overlapped with the orthographic projection of the hole injection layer 142 on the substrate substrate 11, at least a portion of the n-type material layer 15 is in contact with at least a portion of the hole injection layer 142, and the n-type material layer 15 and the hole injection layer 142 form a pn junction at the contact interface.

[0129] The hole injection layer 142 includes a p-type doping material, wherein the concentration of the p-type doping material is relatively high, for example, 2%. 11 The type material layer 15 and the hole injection layer 142 form a pn junction at the contact interface. Under the dual influence of drift motion and diffusion, a high resistance region with a very small number of carriers is formed in the pn junction. Fig.7D As shown, under the influence of the built-in electric field of the PN junction, a built-in voltage (0.5-1.0V) appears at the PN junction. When the hole concentration between adjacent OLED pixels is uneven so that the holes are transferred horizontally in the hole injection layer 142, the vertical electric field formed at the PN junction can make the holes diffused to the area diffuse in the vertical direction under the action of the vertical electric field, thereby suppressing the lateral movement of the holes on the hole injection layer 142, so that the holes cannot diffuse from the pixels with high concentration to the pixels with low concentration, thereby avoiding crosstalk.

[0130] In some embodiments of the present disclosure, the orthographic projection of the n-type material layer 15 on the base substrate 11 is located between the orthographic projections of adjacent pixel openings 131 on the base substrate 11 ; and / or, the n-type material layer 15 is located between the pixel defining layer 13 and the hole injection layer 142 .

[0131] Reference Figure 7CThe n-type material layer 15 is located between each pixel opening to block the movement of holes between adjacent pixels and avoid pixel crosstalk. The n-type material layer 15 can be not only discontinuous but also continuous. The continuous n-type material layers 15 have better anti-crosstalk performance.

[0132] In some embodiments of the present disclosure, the ratio of the thickness of the hole injection layer 142 to the thickness of the n-type material layer 15 is in a range of 2 to 60; and / or the n-type material layer 15 is at least one of Yb / Li doped organic electron transport material, ZnO and AgO.

[0133] The thickness of the n-type material layer 15 is about 5 to 50 nm; the thickness of the hole injection layer 142 is about 10 nm to 300 nm. When the n-type material layer 15 is ZnO or AgO, it can be prepared by inkjet printing; when the n-type material layer 15 is an organic electron transport material doped with Yb / Li, it can be prepared by evaporation. Organic electron transport materials are, for example, TPBi, Bphen, etc., with a doping concentration of 0.1% to 5%. By arranging the n-type material layer 15 between the pixel defining layer 13 and the hole injection layer 142, the built-in voltage generated reduces the lateral transmission of the HIL, making it difficult to light up the surrounding sub-pixels, thereby improving the crosstalk problem.

[0134] The embodiment of the present disclosure also provides a display device, such as Figure 8A-B As shown, Figure 8A-B A structural schematic diagram of a display device 100 provided in an embodiment of the present disclosure, wherein the display device 100 includes a device body 40 and a display substrate 10 or a display substrate 30 disposed on the device body 40, wherein the device body 40 includes a shell and components such as a processor, a power supply, and a camera disposed in the shell, and the display device 100 can adopt the display substrate 10 or the display substrate 30 provided in the above-mentioned embodiment.

[0135] The display device 100 may include any device or product having a display function. For example, the display device 100 may be a smart phone, a mobile phone, an e-book reader, a desktop computer (PC), a laptop PC, a netbook PC, a personal digital assistant (PDA), a portable multimedia player (PMP), a digital audio player, a mobile medical device, a camera, a wearable device (such as a head-mounted device, an electronic clothing, an electronic bracelet, an electronic necklace, an electronic accessory, an electronic tattoo, or a smart watch), a television, etc.

[0136] It should be understood that the display device 100 according to some exemplary embodiments of the present disclosure has all the features and advantages of the above-mentioned display substrate 10 or display substrate 30, and these features and advantages can be referred to the above description of the display substrate 10 or display substrate 30, which will not be repeated here.

[0137] Fig. 9 The flowchart of the method for preparing a display substrate according to an embodiment of the present disclosure is schematically shown.

[0138] According to some exemplary embodiments, referring to Figure 4A , the method for preparing the display substrate includes the following steps S910 to S960.

[0139] In step S910 , a pixel defining layer 13 is formed on the base substrate 11 , and the pixel defining layer 13 defines a plurality of pixel openings 131 .

[0140] In step S920, a first electrode 141 is formed on a side of the pixel defining layer 13 away from the base substrate 11; the orthographic projections of the first electrodes 141 of adjacent organic light emitting diodes 14 on the base substrate 11 at least partially overlap with the orthographic projections of adjacent pixel openings 131 on the base substrate 11, and the orthographic projections of the first electrodes 141 of adjacent organic light emitting diodes 14 on the base substrate 11 are spaced apart.

[0141] In step S930 , an anode modification layer 1411 is formed on a side of the first electrode 141 away from the base substrate 11 , and the anode modification layer 1411 includes a p-type oxide-doped anode material.

[0142] In step S940, a hole injection layer 142 is formed on the side of the anode modification layer 1411 away from the base substrate 11; the orthographic projections of the hole injection layers 142 of adjacent organic light emitting diodes 14 on the base substrate 11 respectively cover the orthographic projections of adjacent pixel openings 131 on the base substrate 11, and the orthographic projections of the hole injection layers 142 of adjacent organic light emitting diodes 14 on the base substrate 11 are connected to each other.

[0143] In step S950 , a light emitting layer 143 is formed on a side of the hole injection layer 142 away from the base substrate 11 .

[0144] In step S960 , a second electrode 145 is formed on a side of the light emitting layer 143 away from the base substrate 11 .

[0145] Exemplarily, a first electrode material is deposited on the base substrate 11, and a first electrode 141 is formed by a patterning process. The first electrode 141 is electrically connected to the driving circuit layer 12 through a via, wherein the material of the first electrode may be indium tin oxide. An anode modification layer 1411 is deposited on the first electrode 141, and the anode modification layer 1411 includes an anode material doped with a p-type oxide. A pixel defining film is coated on the first electrode 141, and the pixel defining film is exposed and developed using a mask plate to form a pixel defining layer 13, and the pixel defining layer 13 defines a plurality of pixel openings 131. A hole injection layer 142, a light emitting layer 143, an electron transport layer 144, and a second electrode 145 are sequentially formed on the pixel defining layer 13, and the light emitting layer 143 is located in the pixel opening 131 region. It is easy to understand that the hole injection layer 142, the electron transport layer 144, and the second electrode 145 can be formed by deposition or coating, and the light emitting layer 413 can be formed in the pixel opening 131 region by an evaporation process.

[0146] As used herein, the terms "substantially," "approximately," "approximately," and other similar terms are used as terms of approximation rather than as terms of degree, and they are intended to account for the inherent deviations in measured or calculated values ​​that would be recognized by one of ordinary skill in the art. Taking into account factors such as process fluctuations, measurement problems, and errors associated with the measurement of a particular quantity (i.e., limitations of the measurement system), "approximately" or "approximately" as used herein include the stated value and mean that the particular value is within an acceptable range of deviation as determined by one of ordinary skill in the art. For example, "approximately" can mean within one or more standard deviations, or within ±10% or ±5% of the stated value.

[0147] Although some embodiments according to the general inventive concept of the present disclosure have been illustrated and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the general inventive concept of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A display substrate, comprising: substrate substrate; A plurality of organic light emitting diodes are located on the base substrate, wherein the organic light emitting diodes include a first electrode, a hole injection layer, a light emitting layer, and a second electrode; as well as A pixel defining layer is located on the base substrate, and the pixel defining layer defines a plurality of pixel openings. The orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate at least partially overlap with the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate are spaced apart; The orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate respectively cover the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate are connected to each other; and The first electrode comprises: An anode modification layer is located on a side of the first electrode facing the hole injection layer, and the anode modification layer comprises an anode material doped with a p-type oxide.

2. The display substrate according to claim 1, wherein: The hole injection layer includes a p-type doping material.

3. The display substrate according to claim 1, wherein: At least a portion of the anode modification layer is located in the pixel opening, and the orthographic projection of the anode modification layer on the base substrate covers the orthographic projection of the first electrode on the base substrate.

4. The display substrate according to claim 1, wherein: The energy level range of the p-type oxide is -4.5 eV to -7.5 eV; and / or, The material of the p-type oxide is selected from at least one of MoO3, NiO, and Cu2O.

5. The display substrate according to claim 1, wherein: The ratio of the thickness of the first electrode to the thickness of the anode modification layer is in the range of 2 to 10; and / or, The doping concentration of the p-type oxide in the anode modification layer is 5% to 30%.

6. The display substrate according to claim 1, wherein: The hole injection layer comprises a plurality of hole injection sublayers stacked in sequence, each of the hole injection sublayers comprising a hole transport material and a p-type doping material; Along the light emitting direction of the display substrate, the concentration of the p-type doping material in the plurality of hole injection sublayers increases sequentially.

7. The display substrate according to claim 6, wherein: The doping concentration of the p-type doping material is in the range of 0.5 to 2%; The number of the hole injection sublayers is 2 to 5.

8. The display substrate according to claim 6, wherein: The ratio of the thickness of the hole injection layer to the thickness of the first electrode is in the range of 0.5 to 4; The thickness of the hole injection layer is 9. A display substrate, comprising: substrate substrate; A plurality of organic light emitting diodes are located on the base substrate, wherein the organic light emitting diodes include a first electrode, a hole injection layer, a light emitting layer and a second electrode, wherein the hole injection layer includes a p-type doping material; A pixel defining layer is located on the base substrate, and the pixel defining layer defines a plurality of pixel openings. The orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate at least partially overlap with the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate are spaced apart; The orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate respectively cover the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate are connected to each other; and The display substrate further comprises: An n-type material layer is located on a side of the pixel defining layer away from the base substrate, an orthographic projection of the n-type material layer on the base substrate at least partially overlaps with an orthographic projection of the hole injection layer on the base substrate, at least a portion of the n-type material layer contacts at least a portion of the hole injection layer, and a pn junction is formed at a contact interface between the n-type material layer and the hole injection layer.

10. The display substrate according to claim 9, wherein: The orthographic projection of the n-type material layer on the substrate is located between the orthographic projections of adjacent pixel openings on the substrate; and / or, The n-type material layer is located between the pixel definition layer and the hole injection layer.

11. The display substrate according to claim 9, wherein: The ratio of the thickness of the hole injection layer to the thickness of the n-type material layer is in the range of 2 to 60; and / or, The n-type material layer is at least one of Yb / Li-doped organic electron transport material, ZnO and AgO.

12. A display device, characterized in that: The invention comprises a display substrate according to any one of claims 1 to 7.

13. A method for preparing a display substrate, the method comprising the following steps: Forming a pixel defining layer on the base substrate, wherein the pixel defining layer defines a plurality of pixel openings; forming a first electrode on a side of the pixel defining layer away from the base substrate; The orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate at least partially overlap with the orthographic projections of adjacent pixel openings on the base substrate, respectively, and the orthographic projections of the first electrodes of adjacent organic light emitting diodes on the base substrate are spaced apart; forming an anode modification layer on a side of the first electrode away from the substrate, wherein the anode modification layer comprises an anode material doped with p-type oxide; forming a hole injection layer on a side of the anode modification layer away from the substrate; The orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate respectively cover the orthographic projections of adjacent pixel openings on the base substrate, and the orthographic projections of the hole injection layers of adjacent organic light emitting diodes on the base substrate are connected to each other; forming a light-emitting layer on a side of the hole injection layer away from the base substrate; A second electrode is formed on a side of the light emitting layer away from the base substrate.

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