Display substrate, manufacturing method thereof, display device and method for reducing driving voltage of display substrate

Abstract

The invention discloses a display substrate, a manufacturing method of the display substrate, a display device and a method for reducing driving voltage of the display substrate. The multiple light-emitting units are arranged between the first electrode layer (10) and the second electrode layer (50) and are connected in series, each charge generation layer is arranged between every two adjacent light-emitting units, and a microcavity is formed between the first electrode layer (10) and the second electrode layer (50); each light-emitting unit comprises a first hole transport layer (21), a second hole transport layer (22) and a light-emitting layer, the light-emitting layer comprises a red light-emitting layer located on the red sub-pixel, and at least one light-emitting unit further comprises a red light-emitting auxiliary layer located on the red sub-pixel. The red light-emitting auxiliary layer is arranged between the red light-emitting layer and a second hole transport layer (22), and the red light-emitting auxiliary layer comprises a hole transport material; wherein the thickness of the red light-emitting layer accounts for 8%-16% of the thickness of the microcavity.

Description

Display substrate and manufacturing method thereof, display device, and method for reducing display substrate driving voltage Technical Field

[0001] The embodiments of the present disclosure relate to, but are not limited to, the field of display technology, and in particular to a display substrate and a display device, and a method for reducing a driving voltage of a display substrate. Background Art

[0002] In the field of organic semiconductor technology applications, organic light emitting devices (OLEDs) have been successfully applied in the commercial flat-panel display and lighting industries. OLEDs are self-luminous, require no backlight, and feature thin panels and low weight. They also offer wide viewing angles, high contrast, fast response times, a wide operating temperature range, and flexibility. Tandem OLED devices play a crucial role in the OLED display and lighting industries.

[0003] Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of the present disclosure.

[0005] An embodiment of the present disclosure provides a display substrate, comprising a red sub-pixel, and further comprising: a first electrode layer, a second electrode layer, a plurality of light-emitting units disposed between the first electrode layer and the second electrode layer and connected in series, and a charge generation layer disposed between two adjacent light-emitting units, wherein a microcavity is formed between the first electrode layer and the second electrode layer; the light-emitting unit comprises a first hole transport layer, a second hole transport layer, and a light-emitting layer, wherein the light-emitting layer comprises a red light-emitting layer located in the red sub-pixel, and at least one of the light-emitting units further comprises a red light-emitting auxiliary layer located in the red sub-pixel, wherein the red light-emitting auxiliary layer is disposed between the red light-emitting layer and the second hole transport layer, and wherein the red light-emitting auxiliary layer comprises a hole transport material;

[0006] Wherein, the thickness of each red light-emitting layer accounts for 8% to 16% of the thickness of the microcavity.

[0007] In an exemplary embodiment of the present disclosure, the thickness of each of the red light emitting layers may account for 8% to 10% of the thickness of the microcavity.

[0008] In an exemplary embodiment of the present disclosure, the thickness of each of the red light-emitting auxiliary layers may account for 1% to 5% of the thickness of the microcavity.

[0009] In an exemplary embodiment of the present disclosure, the thickness of each of the red light-emitting auxiliary layers may account for 3% to 5% of the thickness of the microcavity.

[0010] In an exemplary embodiment of the present disclosure, the total thickness of the red light-emitting layer and the red light-emitting auxiliary layer in one light-emitting unit may account for 9% to 17% of the thickness of the microcavity.

[0011] In an exemplary embodiment of the present disclosure, the second hole transport layer and the red light emitting auxiliary layer may satisfy the following conditions: HTL-3 -μ HTL-2 ≥1×10 -1 @5000V 1 / 2 m 1 / 2 ;

[0012] Among them, μ HTL-3 The red light emitting auxiliary layer is at 5000V 1 / 2 m 1 / 2 The migration rate at

[0013] μ HTL-2 For the second hole transport layer at 5000V 1 / 2 m 1 / 2 The migration rate at time.

[0014] In an exemplary embodiment of the present disclosure, the red light-emitting auxiliary layer and the red light-emitting layer may satisfy the following conditions: REML -n HTL-3 │<0.1;

[0015] Among them, n REML is the refractive index of the red light-emitting layer;

[0016] n REML is the refractive index of the red light-emitting auxiliary layer.

[0017] In an exemplary embodiment of the present disclosure, the red light-emitting auxiliary layer and the red light-emitting layer may satisfy the following conditions: 3eV≤|HOMO HTL-3 │-│LUMO HTL-3 │≤3.4eV; │HOMO REML │-│HOMO HTL-3 │<0.2eV; │LUMO REML │-│LUMO HTL-3 │<0.2eV;

[0018] Among them, HOMO HTL-3 is the highest occupied molecular orbital energy level of the red light-emitting auxiliary layer;

[0019] LUMO HTL-3 is the lowest unoccupied molecular orbital energy level of the red light-emitting auxiliary layer;

[0020] HOMOREML is the lowest unoccupied molecular orbital energy level of the red light-emitting layer;

[0021] LUMO REML is the lowest unoccupied molecular orbital energy level of the red light-emitting layer.

[0022] In an exemplary embodiment of the present disclosure, the first hole transport layer, the second hole transport layer, the red light emitting auxiliary layer and the red light emitting layer may satisfy the following conditions: HTL-3 >T HTL-2 ; T HTL-3 <T HTL-1 ; T HTL-3 +T HTL-2 ≥T HTL-1 ; T HTL-3 <T REML ;

[0023] Among them, T HTL-1 is the thickness of the first hole transport layer;

[0024] T HTL-2 is the thickness of the second hole transport layer;

[0025] T HTL-3 is the thickness of the red light-emitting auxiliary layer;

[0026] T REML is the thickness of the red light-emitting layer.

[0027] In an exemplary embodiment of the present disclosure, the thickness of each of the red light-emitting layers may be 30 nm to 50 nm, and the thickness of each of the red light-emitting auxiliary layers may be 10 nm to 25 nm.

[0028] In an exemplary embodiment of the present disclosure, the display substrate may further include a green sub-pixel and a blue sub-pixel, the light-emitting layer may further include a green light-emitting layer and a blue light-emitting layer respectively located at the green sub-pixel and the blue sub-pixel, and at least one of the light-emitting units may further include any one or more of a green light-emitting auxiliary layer located at the green sub-pixel and a blue light-emitting auxiliary layer located at the blue sub-pixel; the green light-emitting auxiliary layer includes a hole transport material, and the blue light-emitting auxiliary layer includes a hole transport material.

[0029] In an exemplary embodiment of the present disclosure, the red light-emitting auxiliary layer, the green light-emitting layer and the blue light-emitting layer may satisfy the following conditions: │HOMO GEML │-│HOMO HTL-3 │≥0.2eV; │HOMO BEML │-│HOMO HTL-3 │≥0.2eV;

[0030] Among them, HOMO HTL-3 is the highest occupied molecular orbital energy level of the red light-emitting auxiliary layer;

[0031] HOMO GEML is the highest occupied molecular orbital energy level of the green light-emitting layer;

[0032] HOMO BEML is the highest occupied molecular orbital energy level of the blue light-emitting layer.

[0033] In an exemplary embodiment of the present disclosure, the hole transport materials in the red light-emitting auxiliary layer, the green light-emitting auxiliary layer and the blue light-emitting auxiliary layer can be independently selected from any one or more of aromatic amine hole transport materials, carbazole hole transport materials and dimethylfluorene hole transport materials.

[0034] In an exemplary embodiment of the present disclosure, the red light emitting layer may include a red host material and a red guest material, and a doping ratio of the red guest material is 1% to 5%.

[0035] In exemplary embodiments of the present disclosure, the red host material may include any one or more of DCM series red light-emitting materials, and the red guest material may include any one or more of metal complex type red light-emitting materials.

[0036] In an exemplary embodiment of the present disclosure, the green light emitting layer may include a green host material and a green guest material, and the doping ratio of the green guest material may be 5% to 15%.

[0037] In an exemplary embodiment of the present disclosure, the green host material may include any one or more of coumarin dyes, quinacridone copper derivatives green light-emitting materials, polycyclic aromatic hydrocarbons green light-emitting materials, diamine anthracene derivatives green light-emitting materials and carbazole derivatives green light-emitting materials, and the green guest material may include any one or more of metal complex green light-emitting materials.

[0038] In an exemplary embodiment of the present disclosure, the blue light emitting layer may include a blue host material and a blue guest material, and a doping ratio of the blue guest material is 1% to 5%.

[0039] In an exemplary embodiment of the present disclosure, the blue host material may include any one or more of a pyrene derivative-type blue light-emitting material, anthracene derivative-type blue light-emitting material, fluorene derivative-type blue light-emitting material, perylene derivative-type blue light-emitting material and styrylamine derivative-type blue light-emitting material, and the blue guest material may include any one or more of a metal complex-type blue light-emitting material.

[0040] An embodiment of the present disclosure further provides a display device, which includes the display substrate provided in the above embodiment of the present disclosure.

[0041] The present disclosure further provides a method for manufacturing the display substrate provided in the above embodiment of the present disclosure, the manufacturing method comprising:

[0042] forming a first electrode layer on one side of the substrate;

[0043] forming a first hole transport layer and a second hole transport layer in sequence on a side of the first electrode layer away from the substrate;

[0044] forming a red light-emitting auxiliary layer located in the red sub-pixel on a side of the second hole transport layer away from the substrate by an evaporation method;

[0045] Using an evaporation method, a red light-emitting layer is formed on a side of the red light-emitting auxiliary layer away from the substrate, and a green light-emitting layer and a blue light-emitting layer are formed on a side of the second hole transport layer away from the substrate, respectively, and are located in the green sub-pixel and the blue sub-pixel. The red light-emitting layer, the green light-emitting layer, and the blue light-emitting layer constitute a light-emitting layer, and the light-emitting layer, the red light-emitting auxiliary layer, the first hole transport layer, and the second hole transport layer constitute a light-emitting unit.

[0046] forming a charge generation layer on a side of the light emitting unit away from the substrate;

[0047] forming at least one light-emitting unit on a side of the charge generation layer away from the substrate, and forming a charge generation layer between two adjacent light-emitting units;

[0048] A second electrode layer is formed.

[0049] The present disclosure also provides a method for reducing a driving voltage of a display substrate, wherein the display substrate includes a red sub-pixel, and further includes: a first electrode layer, a second electrode layer, a plurality of light-emitting units disposed between the first electrode layer and the second electrode layer and connected in series, and a charge generation layer disposed between two adjacent light-emitting units, wherein a microcavity is formed between the first electrode layer and the second electrode layer; the light-emitting unit includes a first hole transport layer, a second hole transport layer, and a light-emitting layer, wherein the light-emitting layer includes a red light-emitting layer located in the red sub-pixel;

[0050] The method for reducing the driving voltage of the display substrate includes: using a hole transport material to form a red light-emitting auxiliary layer located between the red light-emitting layer and the second hole transport layer in the red sub-pixel, and the thickness of the red light-emitting layer accounts for 8% to 16% of the thickness of the microcavity, the thickness of the red light-emitting auxiliary layer accounts for 1% to 5% of the thickness of the microcavity, and the total thickness of the red light-emitting layer and the red light-emitting auxiliary layer in a light-emitting unit accounts for 9% to 17% of the thickness of the microcavity.

[0051] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings are used to provide an understanding of the technical solution of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the technical solution of the present disclosure and do not constitute a limitation to the technical solution of the present disclosure.

[0053] FIG1 is a schematic structural diagram of a display substrate provided by an exemplary embodiment of the present disclosure;

[0054] FIG2 is a schematic structural diagram of another display substrate provided by an exemplary embodiment of the present disclosure;

[0055] FIG3 is a schematic structural diagram of another display substrate provided by an exemplary embodiment of the present disclosure;

[0056] FIG. 4 is a schematic structural diagram of another display substrate provided by an exemplary embodiment of the present disclosure.

[0057] The meanings of the marking symbols in the accompanying drawings are: 10-first electrode layer; 20-first light-emitting unit; 21-first hole transport layer; 22-second hole transport layer; 23-first red light-emitting auxiliary layer; 24-first light-emitting layer; 241-first red light-emitting layer; 242-first green light-emitting layer; 243-first blue light-emitting layer; 25-first green light-emitting auxiliary layer; 26-first blue light-emitting auxiliary layer; 27-first hole blocking layer; 30-first charge generation layer; 40-second light-emitting unit; 41-third hole transport layer; 42-fourth hole transport layer; 43-second Red light-emitting auxiliary layer; 44-second light-emitting layer; 441-second red light-emitting layer; 442-second green light-emitting layer; 443-second blue light-emitting layer; 45-second hole blocking layer; 50-second electrode layer; 60-third light-emitting unit; 61-fifth hole transport layer; 62-sixth hole transport layer; 63-third red light-emitting auxiliary layer; 64-third light-emitting layer; 641-third red light-emitting layer; 642-third green light-emitting layer; 643-third blue light-emitting layer; 70-second charge generation layer; 80-hole injection layer. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the embodiments can be implemented in a variety of different forms. A person of ordinary skill in the art can easily understand the fact that the methods and contents can be transformed into various forms without departing from the purpose and scope of the present disclosure. Therefore, the present disclosure should not be interpreted as being limited to the contents described in the following embodiments. Unless there is a conflict, the embodiments in the present disclosure and the features in the embodiments can be arbitrarily combined with each other. In order to keep the following description of the embodiments of the present disclosure clear and concise, the present disclosure omits detailed descriptions of some known functions and known components. The drawings of the embodiments of the present disclosure only involve structures related to the embodiments of the present disclosure. Other structures can refer to the general design

[0059] The scales of the figures in this disclosure can be used as a reference for actual processes, but are not limited to such. For example, the width-to-length ratio of the channel, the thickness and spacing of the various film layers, and the width and spacing of the various signal lines can be adjusted according to actual needs. The number of pixels in the display substrate and the number of sub-pixels in each pixel are not limited to the numbers shown in the figures. The figures described in this disclosure are merely schematic structural diagrams, and one embodiment of this disclosure is not limited to the shapes or values ​​shown in the figures.

[0060] In this disclosure, for convenience, words and phrases indicating orientation or positional relationships, such as "middle," "upper," "lower," "front," "back," "vertical," "horizontal," "top," "bottom," "inside," and "outside," are used to illustrate the positional relationships of constituent elements with reference to the accompanying drawings. This is merely for the convenience of describing this specification and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation of this disclosure. The positional relationships of constituent elements may be appropriately changed according to the direction in which each constituent element is described. Therefore, the words and phrases described in this disclosure are not limited and may be appropriately replaced according to the circumstances.

[0061] In this disclosure, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed, removable, or integral connections; mechanical or electrical connections; direct connections, indirect connections through intermediaries, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on the specific circumstances.

[0062] In this disclosure, "electrically connected" includes components connected together via an element having some electrical function. There are no particular limitations on the "element having some electrical function" as long as it enables the transfer of electrical signals between the connected components. Examples of "element having some electrical function" include not only electrodes and wiring, but also switching elements such as transistors, resistors, inductors, capacitors, and other components with various functions.

[0063] In this specification, "parallel" refers to a state where the angle formed by two straight lines is greater than -10° and less than 10°, and thus also includes a state where the angle is greater than -5° and less than 5°. Furthermore, "perpendicular" refers to a state where the angle formed by two straight lines is greater than 80° and less than 100°, and thus also includes a state where the angle is greater than 85° and less than 95°.

[0064] In the present disclosure, ordinal numbers such as “first” and “second” are provided to avoid confusion among constituent elements and do not indicate any order, quantity or importance.

[0065] In the present disclosure, the terms "film" and "layer" may be interchanged. For example, "luminescent layer" may sometimes be replaced with "luminescent film."

[0066] Organic electroluminescent devices (OLEDs) are current-driven devices that emit light. Driven by the same current density, the brightness of a tandem OLED consisting of n identical light-emitting units is n times that of a traditional OLED consisting of a single light-emitting unit. Therefore, the current efficiency of a tandem OLED is n times that of a traditional OLED. However, the driving voltage of a tandem OLED is also n times that of a traditional OLED, so the power efficiency of the two is theoretically similar. In addition, OLED displays and lighting devices operate at a certain brightness. At the same light-emitting brightness, the current density driving a tandem OLED is 1 / n of the current density of a traditional OLED. The greater the current density of the OLED, the faster it ages and the shorter the device life. Therefore, the lifespan of a tandem OLED is longer than that of a traditional OLED.

[0067] An embodiment of the present disclosure provides a display substrate, comprising a red sub-pixel, and further comprising: a first electrode layer, a second electrode layer, a plurality of light-emitting units disposed between the first electrode layer and the second electrode layer and connected in series, and a charge generation layer (CGL) disposed between two adjacent light-emitting units, wherein a microcavity is formed between the first electrode layer and the second electrode layer; the light-emitting unit comprises a first hole transport layer (HTL), a second hole transport layer, and an emitting layer (EML), wherein the emitting layer comprises a red light-emitting layer located in the red sub-pixel, and at least one of the light-emitting units further comprises a red light-emitting auxiliary layer located in the red sub-pixel, wherein the red light-emitting auxiliary layer is disposed between the red light-emitting layer and the second hole transport layer, and wherein the red light-emitting auxiliary layer comprises a hole transport material;

[0068] Wherein, the thickness of each red light-emitting layer accounts for 8% to 16% of the thickness of the microcavity.

[0069] In current OLED display substrates, the thickness of each red light-emitting layer accounts for approximately 9% to 20% of the thickness of the microcavity between the first and second electrode layers. In the display substrate of the disclosed embodiments, a red light-emitting auxiliary layer comprising a hole transport material is provided on one side of the red light-emitting layer, reducing the thickness of each red light-emitting layer to 8% to 16% of the microcavity thickness. Therefore, the red light-emitting auxiliary layer replaces a certain thickness of the red light-emitting layer, thereby reducing the driving voltage of the display substrate.

[0070] Figure 1 is a schematic diagram of the structure of a display substrate provided by an exemplary embodiment of the present disclosure. The display substrate includes red sub-pixels, green sub-pixels, and blue sub-pixels. As shown in Figure 1 , the display substrate also includes a first electrode layer 10, a first light-emitting unit 20, a first charge generation layer 30, a second light-emitting unit 40, and a second electrode layer 50.

[0071] The first electrode layer 10 is an anode layer, and the second electrode layer 50 is a cathode layer, or the first electrode layer 10 is a cathode layer, and the second electrode layer 50 is an anode layer. A microcavity is formed between the first electrode layer 10 and the second electrode layer 50, and the thickness of the microcavity is T.

[0072] The first light-emitting unit 20 is disposed on one side of the first electrode layer 10. The first light-emitting unit 20 includes a first hole transport layer 21 disposed on one side of the first electrode layer 10, a second hole transport layer 22 disposed on the side of the first hole transport layer 21 away from the first electrode layer 10, a first red light-emitting auxiliary layer 23 disposed on the side of the second hole transport layer 22 away from the first electrode layer 10, and a first light-emitting layer 24. The first light-emitting layer 24 includes a first red light-emitting layer 241 located in a red sub-pixel, a first green light-emitting layer 242 located in a green sub-pixel, and a first blue light-emitting layer 243 located in a blue sub-pixel. The first red light-emitting auxiliary layer 23 is located in the red sub-pixel and between the second hole transport layer 22 and the first red light-emitting layer 241. The first red light-emitting auxiliary layer 23 includes a hole transport material and its thickness accounts for 8% to 16% of the thickness of the microcavity.

[0073] The first charge generation layer 30 is disposed on a side of the first light emitting unit 20 away from the first electrode layer 10 , and is used to connect the first light emitting unit 20 and the second light emitting unit 40 and generate carriers.

[0074] The second light-emitting unit 40 is disposed on a side of the first charge generation layer 30 away from the first electrode layer 10. The second light-emitting unit 40 includes a third hole transport layer 41 disposed on a side of the first charge generation layer 30 away from the first electrode layer 10, a fourth hole transport layer 42 disposed on a side of the third hole transport layer 41 away from the first electrode layer 10, a second red light-emitting auxiliary layer 43 and a second light-emitting layer 44 disposed on a side of the fourth hole transport layer 42 away from the first electrode layer 10. The second light-emitting layer 44 includes a second red light-emitting layer 441 located in a red sub-pixel, a second green light-emitting layer 442 located in a green sub-pixel, and a second blue light-emitting layer 443 located in a blue sub-pixel. The second red light-emitting auxiliary layer 43 is located in the red sub-pixel and between the fourth hole transport layer 42 and the second red light-emitting layer 441. The second red light-emitting auxiliary layer 43 includes a hole transport material and its thickness accounts for 8% to 16% of the thickness of the microcavity.

[0075] In the display substrate shown in FIG1 , the number of the light-emitting units is 2, and the red sub-pixel of each light-emitting unit is provided with a red light-emitting auxiliary layer.

[0076] In other exemplary embodiments, a red light-emitting auxiliary layer can be provided in only the red sub-pixel of one light-emitting unit, replacing a red light-emitting layer of a certain thickness, which can also effectively reduce the driving voltage of the display substrate. However, providing a red light-emitting auxiliary layer in all red sub-pixels can further reduce the driving voltage of the display substrate.

[0077] Figure 2 is a schematic diagram of the structure of another display substrate provided by an exemplary embodiment of the present disclosure. The display substrate shown in Figure 2 includes two light-emitting units arranged in series: a first light-emitting unit 20 and a second light-emitting unit 40. However, only the red sub-pixel of the first light-emitting unit 20 is provided with a red light-emitting auxiliary layer, and the driving voltage of this display substrate is also relatively low.

[0078] Figure 3 is a schematic diagram of the structure of another display substrate provided by an exemplary embodiment of the present disclosure. The display substrate shown in Figure 3 includes three light-emitting units arranged in series: a first light-emitting unit 20, a second light-emitting unit 40, and a third light-emitting unit 60. A second charge generation layer 70 is disposed between the second light-emitting unit 40 and the third light-emitting unit 60.

[0079] The third light-emitting unit 60 is disposed on the side of the second charge generation layer 70 away from the first electrode layer 10. The third light-emitting unit 60 includes a fifth hole transport layer 61 disposed on the side of the second charge generation layer 70 away from the first electrode layer 10, a sixth hole transport layer 62 disposed on the side of the fifth hole transport layer 61 away from the first electrode layer 10, a third red light-emitting auxiliary layer 63 disposed on the side of the sixth hole transport layer 62 away from the first electrode layer 10, and a third light-emitting layer 64. The third light-emitting layer 64 includes a third red light-emitting layer 641 located in the red sub-pixel, a third green light-emitting layer 642 located in the green sub-pixel, and a third blue light-emitting layer 643 located in the blue sub-pixel. The third red light-emitting auxiliary layer 63 is located in the red sub-pixel and between the sixth hole transport layer 62 and the third red light-emitting layer 641. The third red light-emitting auxiliary layer 63 includes a hole transport material and its thickness accounts for 8% to 16% of the thickness of the microcavity. The rest of the structure is the same as the display substrate shown in Figure 1.

[0080] In an exemplary embodiment of the present disclosure, the thickness of each of the red light emitting layers may account for 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or 16% of the thickness of the microcavity.

[0081] In an exemplary embodiment of the present disclosure, the thickness of each of the red light emitting layers may account for 8% to 10% of the thickness of the microcavity.

[0082] In an exemplary embodiment of the present disclosure, the thickness of the red light-emitting layer in different light-emitting units may be the same or different, and may be independently selected within a range of 8% to 16% of the thickness of the microcavity.

[0083] In an exemplary embodiment of the present disclosure, the thickness of each red light-emitting auxiliary layer may account for 1% to 5% of the thickness of the microcavity. For example, the thickness of each red light-emitting auxiliary layer may account for 1%, 2%, 3%, 4% or 5% of the thickness of the microcavity.

[0084] In an exemplary embodiment of the present disclosure, the total thickness of the red light-emitting layer and the red light-emitting auxiliary layer in one light-emitting unit may account for 9% to 17% of the thickness of the microcavity. For example, the total thickness of the red light-emitting layer and the red light-emitting auxiliary layer in one light-emitting unit may account for 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, or 17% of the thickness of the microcavity.

[0085] The thickness of each of the red light-emitting auxiliary layers accounts for 1% to 5% of the thickness of the microcavity, and the thickness of each of the red light-emitting layers accounts for 8% to 16% of the thickness of the microcavity. In a light-emitting unit, the total thickness of the red light-emitting auxiliary layer and the red light-emitting layer accounts for 9% to 17% of the thickness of the microcavity, which is equivalent to the thickness of a red light-emitting layer in the current OLED display substrate. Therefore, the display substrate of the embodiment of the present disclosure uses a red light-emitting auxiliary layer to replace a red light-emitting layer of a certain thickness, rather than introducing an additional red light-emitting auxiliary layer.

[0086] In an exemplary embodiment of the present disclosure, the thickness of each of the red light-emitting auxiliary layers may account for 3% to 5% of the thickness of the microcavity.

[0087] In an exemplary embodiment of the present disclosure, the thickness of the red light-emitting auxiliary layer in different light-emitting units may be the same or different, and may be independently selected within the range of 1% to 5% of the thickness of the microcavity. For example, the thickness may be independently selected within the range of 3% to 5% of the thickness of the microcavity.

[0088] In an exemplary embodiment of the present disclosure, the second hole transport layer and the red light emitting auxiliary layer may satisfy the following conditions: HTL-3 -μ HTL-2 ≥1×10 -1 @5000V 1 / 2 m 1 / 2 ;

[0089] Among them, μ HTL-3 The red light emitting auxiliary layer is at 5000V 1 / 2 m 1 / 2 The migration rate at

[0090] μ HTL-2 For the second hole transport layer at 5000V 1 / 2 m 1 / 2 The migration rate at time.

[0091] The second hole transport layer and the red light emitting auxiliary layer can satisfy μ HTL-3 -μ HTL-2 ≥1×10 -1 @5000V 1 / 2 m 1 / 2It is more conducive to reducing the driving voltage of the display substrate.

[0092] Replacing part of the red light-emitting layer with a red light-emitting auxiliary layer of a certain thickness and high mobility can significantly reduce the operating voltage of the display substrate. The second hole transport layer has a relatively slow mobility, which can match the mobility of the green light-emitting layer of the green sub-pixel and the blue light-emitting layer of the blue sub-pixel, ensuring normal carrier transmission.

[0093] In an exemplary embodiment of the present disclosure, the red light-emitting auxiliary layer and the red light-emitting layer may satisfy the following conditions: REML -n HTL-3 │<0.1;

[0094] Among them, n REML is the refractive index of the red light-emitting layer;

[0095] n REML is the refractive index of the red light-emitting auxiliary layer.

[0096] The red light-emitting auxiliary layer and the red light-emitting layer may satisfy |n REML -n HTL-3 │<0.1, that is, the refractive index of the red light-emitting auxiliary layer and the red light-emitting layer is at the same level, so that after the red light-emitting auxiliary layer is used to replace part of the red light-emitting layer, the microcavity structure of the display substrate can still be maintained, thereby achieving higher light extraction efficiency.

[0097] In an exemplary embodiment of the present disclosure, the red light-emitting auxiliary layer and the red light-emitting layer may satisfy the following conditions: 3eV≤|HOMO HTL-3 │-│LUMO HTL-3 │≤3.4eV; │HOMO REML │-│HOMO HTL-3 │<0.2eV; │LUMO REML │-│LUMO HTL-3 │<0.2eV;

[0098] Among them, HOMO HTL-3 is the highest occupied molecular orbital energy level of the red light-emitting auxiliary layer;

[0099] LUMO HTL-3 is the lowest unoccupied molecular orbital energy level of the red light-emitting auxiliary layer;

[0100] HOMO REML is the lowest unoccupied molecular orbital energy level of the red light-emitting layer;

[0101] LUMO REML is the lowest unoccupied molecular orbital energy level of the red light-emitting layer.

[0102] The red light-emitting auxiliary layer and the red light-emitting layer may satisfy 3eV≤│HOMO HTL-3 │-│LUMO HTL-3 │≤3.4eV、│HOMO REML │-│HOMO HTL-3 │<0.2eV、│LUMO REML │-│LUMO HTL-3 │<0.2eV is beneficial for reducing the driving voltage of the display substrate and achieving higher light extraction efficiency.

[0103] In an exemplary embodiment of the present disclosure, the first hole transport layer, the second hole transport layer, the red light emitting auxiliary layer and the red light emitting layer may satisfy the following conditions: HTL-3 >T HTL-2 ; T HTL-3 <T HTL-1 ; T HTL-3 +T HTL-2 ≥T HTL-1 ; T HTL-3 <T REML ;

[0104] Among them, T HTL-1 is the thickness of the first hole transport layer;

[0105] T HTL-2 is the thickness of the second hole transport layer;

[0106] T HTL-3 is the thickness of the red light-emitting auxiliary layer;

[0107] T REML is the thickness of the red light-emitting layer.

[0108] The first hole transport layer, the second hole transport layer, the red light-emitting auxiliary layer and the red light-emitting layer satisfy T HTL-3 >T HTL-2 、T HTL-3 <T HTL-1 、T HTL-3 +T HTL-2 ≥T HTL-1 、T HTL-3 <T REML This is beneficial to ensuring the normal transmission of carriers and effectively reducing the operating voltage of the display substrate.

[0109] In an exemplary embodiment of the present disclosure, the thickness of each of the red light-emitting layers may be 30 nm to 50 nm, and the thickness of each of the red light-emitting auxiliary layers may be 10 nm to 25 nm.

[0110] The thickness of each of the red light-emitting layers may be 30 nm to 50 nm, for example, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm.

[0111] The thickness of each of the red light-emitting auxiliary layers may be 10 nm to 25 nm, for example, 10 nm, 15 nm, 20 nm or 25 nm.

[0112] In an exemplary embodiment of the present disclosure, the display substrate may further include a green sub-pixel and a blue sub-pixel, the light-emitting layer may further include a green light-emitting layer and a blue light-emitting layer respectively located at the green sub-pixel and the blue sub-pixel, and at least one of the light-emitting units may further include any one or more of a green light-emitting auxiliary layer located at the green sub-pixel and a blue light-emitting auxiliary layer located at the blue sub-pixel; the green light-emitting auxiliary layer includes a hole transport material, and the blue light-emitting auxiliary layer includes a hole transport material.

[0113] Figure 4 is a schematic diagram of the structure of another display substrate provided by an exemplary embodiment of the present disclosure. As shown in Figure 4, the green sub-pixels and blue sub-pixels of the first light-emitting layer 24 are respectively provided with a first green light-emitting auxiliary layer 25 and a first blue light-emitting auxiliary layer 26. The first green light-emitting auxiliary layer 25 is located between the green light-emitting layer 242 and the second hole transport layer 22, and the first blue light-emitting auxiliary layer 26 is located between the blue light-emitting layer 243 and the second hole transport layer 22. When the red, green, and blue sub-pixels of the light-emitting unit are all provided with a light-emitting auxiliary layer that replaces part of the light-emitting layer, it is beneficial to significantly reduce the driving voltage of the display substrate.

[0114] In an exemplary embodiment of the present disclosure, the red light-emitting auxiliary layer, the green light-emitting layer and the blue light-emitting layer may satisfy the following conditions: │HOMO GEML │-│HOMO HTL-3 │≥0.2eV; │HOMO BEML │-│HOMO HTL-3 │≥0.2eV;

[0115] Among them, HOMO HTL-3 is the highest occupied molecular orbital energy level of the red light-emitting auxiliary layer;

[0116] HOMO GEML is the highest occupied molecular orbital energy level of the green light-emitting layer;

[0117] HOMO BEML is the highest occupied molecular orbital energy level of the blue light-emitting layer.

[0118] The red light-emitting auxiliary layer, the green light-emitting layer and the blue light-emitting layer satisfy |HOMO GEML│-│HOMO HTL-3 │≥0.2eV、│HOMO BEML │-│HOMO HTL-3 │≥0.2eV, which is conducive to ensuring the normal transmission of carriers and effectively reducing the operating voltage of the display substrate.

[0119] In an exemplary embodiment of the present disclosure, the light-emitting substrate may further include any one or more of the following layers: a hole injection layer (HIL), an electron block layer (EBL), a hole block layer (HBL), an electron transport layer (ETL), and an electron injection layer (EIL). In an exemplary embodiment of the present disclosure, one or more of the hole injection layer, hole transport layer, electron block layer, hole blocking layer, electron transport layer, and electron injection layer of all sub-pixels may be a common layer connected together, and the light-emitting layers of adjacent sub-pixels may have a small amount of overlap or may be isolated.

[0120] As shown in FIG1 , the light-emitting substrate further includes a hole injection layer 80 disposed between the first electrode layer 10 and the first light-emitting unit 20, an electron transport layer 90 disposed on the side of the second light-emitting unit 40 away from the first electrode layer 10, and an electron injection layer 100 disposed between the electron transport layer 90 and the second electrode layer 50. The first light-emitting unit 20 further includes a first hole blocking layer 27 disposed on the side of the first light-emitting layer 24 away from the first electrode layer 10. The second light-emitting unit 40 further includes a second hole blocking layer 45 disposed on the side of the second light-emitting layer 44 away from the first electrode layer 10.

[0121] In an exemplary embodiment of the present disclosure, the material of the anode layer may be a material having a high work function. For example, for a bottom-emitting device, the anode may be made of a transparent oxide material, such as indium tin oxide (ITO) or indium zinc oxide (IZO). Alternatively, for a top-emitting device, the anode may be made of a composite electrode of metal and transparent oxide, such as ITO (indium tin oxide, Indium Tin Oxide) / Ag / ITO, Ag / IZO (indium zinc oxide, Indium Zinc Oxide), carbon nanotubes (CNT) / ITO, CNT / IZO, graphene oxide (Graphene Oxide, GO) / ITO, GO / IZO, Al / ITO or Al / IZO, etc., which can ensure good reflectivity.

[0122] In an exemplary embodiment of the present disclosure, the material of the hole injection layer may include a transition metal oxide, for example, any one or more of molybdenum oxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, tungsten oxide, and manganese oxide.

[0123] In another exemplary embodiment, the material of the hole injection layer may include a p-type dopant of a strong electron-withdrawing system and a hole transport material;

[0124] The p-type dopant may include any one or more of 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano-p-benzoquinone (F4TCNQ), and 1,2,3-tris[(cyano)(4-cyano-2,3,5,6-tetrafluorophenyl)methylene]cyclopropane;

[0125] The hole transport material may include any one or more of an aromatic amine hole transport material, a dimethylfluorene hole transport material, and a carbazole hole transport material; for example, the hole transport material may include any one or more of 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (BAFLP), 4,4'-bis[N-(9,9-dimethylfluorene-2-yl)-N-phenylamino]biphenyl (DFLDPBi), 4,4'-di(9-carbazolyl)biphenyl (CBP) and 9-phenyl-3-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (PCzPA).

[0126] In an exemplary embodiment of the present disclosure, the hole injection layer may be formed by evaporation; and the thickness may be 5 nm to 20 nm.

[0127] In an exemplary embodiment of the present disclosure, the material of the hole transport layer may include any one or more of an aromatic amine hole transport material, a dimethylfluorene hole transport material, and a carbazole hole transport material; for example, the material of the hole transport layer may include any one or more of 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (BAFLP) and 4,4'-bis[N-(9,9-dimethylfluorene-2-yl)-N-phenylamino]biphenyl (DFLDPBi).

[0128] In exemplary embodiments of the present disclosure, the material of the red light-emitting auxiliary layer may include any one or more of an aromatic amine hole transport material, a carbazole hole transport material, and a dimethylfluorene hole transport material. For example, the material of the red light-emitting auxiliary layer may include 4,4'-bis(9-carbazolyl)biphenyl (CBP), 9-phenyl-3-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (PCzPA), and the like.

[0129] In exemplary embodiments of the present disclosure, the material of the green light-emitting auxiliary layer may include any one or more of an aromatic amine hole transport material, a carbazole hole transport material, and a dimethylfluorene hole transport material. For example, the material of the green light-emitting auxiliary layer may be 3,3'-bis(9H-carbazol-9-yl)-1,1'-bicarbazole (m-CBP).

[0130] In an exemplary embodiment of the present disclosure, the material of the blue light-emitting auxiliary layer may include any one or more of an aromatic amine hole transport material, a carbazole hole transport material, and a dimethylfluorene hole transport material. For example, the material of the blue light-emitting auxiliary layer may be 1,3-dicarbazol-9-ylbenzene (mCP).

[0131] In an exemplary embodiment of the present disclosure, the hole transport layer may be formed by evaporation.

[0132] In an exemplary embodiment of the present disclosure, the material of the light-emitting layer may include one light-emitting material, or may include two or more light-emitting materials, for example, a host light-emitting material and a guest light-emitting material doped into the host light-emitting material.

[0133] In an exemplary embodiment of the present disclosure, the red light-emitting layer may include a red host material and a red guest material, wherein the doping ratio of the red guest material is 1% to 5%, for example, 2% to 3%. The red host material may be a red phosphorescent material, and the red guest material may be a red phosphorescent dopant.

[0134] In exemplary embodiments of the present disclosure, the red host material may include any one or more of DCM series red light-emitting materials, and the red guest material may include any one or more of metal complex type red light-emitting materials.

[0135] For example, the red host material can be any one or more of 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminophenylvinyl)-4H-pyran (DCM), 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidine-9-enyl)-4H-pyran (DCJTB), and DCJIT; the red guest material can be any one or more of bis(1-phenylisoquinoline)(acetylacetonate)iridium(III) (Ir(piq)2(acac)), octaethylporphyrin platinum (abbreviated as: PtOEP), and bis(2-(2'-benzothienyl)pyridine-N,C3')(acetylacetonate)iridium complex (abbreviated as: Ir(btp)2(acac).

[0136] In an exemplary embodiment of the present disclosure, the green light-emitting layer may include a green host material and a green guest material. The doping ratio of the green guest material may be 5% to 15%, for example, 8% to 10%. The green host material may be a green phosphorescent material, and the green guest material may be a green phosphorescent dopant; alternatively, the green host material may be a green fluorescent material, and the green guest material may be a green fluorescent dopant.

[0137] In an exemplary embodiment of the present disclosure, the green host material may include any one or more of coumarin dyes, quinacridone copper derivatives green light-emitting materials, polycyclic aromatic hydrocarbons green light-emitting materials, diamine anthracene derivatives green light-emitting materials and carbazole derivatives green light-emitting materials, and the green guest material may include any one or more of metal complex green light-emitting materials.

[0138] For example, the green host material may include coumarin 6 (C-6), coumarin 545T (C-525T), quinacridone copper (QA), N,N″-dimethylquinacridone (DMQA), 5,12-diphenylnaphthonaphthalene (DPT), N10,N10′-diphenyl-N10,N10′-diphthaloyl-9,9′-dianthracene-10,10′-diamine (abbreviated as: BA-NPB), tris(8-hydroxyquinoline)aluminum(III) (abbreviated as: Alq3), etc.; the green guest material may be any one or more of tris(2-phenylpyridine)iridium (Ir(ppy)3), di(2-phenylpyridine)iridium acetylacetonate (Ir(ppy)2(acac)).

[0139] In an exemplary embodiment of the present disclosure, the blue light emitting layer may include a blue host material and a blue guest material, and the doping ratio of the blue guest material is 1% to 5%, for example, 1% to 3%.

[0140] In an exemplary embodiment of the present disclosure, the blue host material may include any one or more of a pyrene derivative-type blue light-emitting material, anthracene derivative-type blue light-emitting material, fluorene derivative-type blue light-emitting material, perylene derivative-type blue light-emitting material and styrylamine derivative-type blue light-emitting material, and the blue guest material may include any one or more of a metal complex-type blue light-emitting material.

[0141] For example, the blue host material can be N1,N6-di([1,1'-biphenyl]-2-yl)-N1,N6-di([1,1'-biphenyl]-4-yl)pyrene-1,6-diamine, 9,10-di-(2-naphthyl)anthracene (ADN), 2-methyl-9,10-di-2-naphthylanthracene (MADN), etc.; the blue guest material can be any one or more of 2,5,8,11-tetra-tert-butylperylene (TBPe), 4,4'-bis[4-(diphenylamino)phenylvinyl]biphenyl (BDAVBi), 4,4'-bis[4-(di-p-tolylamino)phenylvinyl]biphenyl (DPAVBi), and bis(4,6-difluorophenylpyridine-C2,N)picolinyliridium (FIrpic).

[0142] In an exemplary embodiment of the present disclosure, the light emitting layer may be formed by evaporation.

[0143] In an exemplary embodiment of the present disclosure, the charge generation layer may include a P-type charge generation layer and an N-type charge generation layer. The P-type charge generation layer may be a hole-type material such as NPB, TPD, etc., and the N-type charge generation layer may be an electron-type material containing phenanthroline or phosphine oxide. Both the P-type charge generation layer and the N-type charge generation layer may contain a dopant. The dopant in the P-type charge generation layer may be HATCN, F4TCNQ, etc., and the dopant in the N-type charge generation layer may be an alkali metal or alkaline earth metal and its oxide.

[0144] In an exemplary embodiment of the present disclosure, the material of the hole blocking layer may include an aromatic heterocyclic hole blocking material, for example, it may include any one or more of a benzimidazole derivative hole blocking material, an imidazopyridine derivative hole blocking material, a benzimidazolephenanthridine derivative hole blocking material, a pyrimidine derivative hole blocking material, a triazine derivative hole blocking material, a quinoline derivative hole blocking material, an isoquinoline derivative hole blocking material, and a phenanthroline derivative hole blocking material.

[0145] For another example, the hole blocking layer material may include any one or more of 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7), 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenyl)-1,2,4-triazole (TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenyl)-1,2,4-triazole (p-EtTAZ), bathophenanthroline (BPhen), (BCP), and 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (BzOs).

[0146] In an exemplary embodiment of the present disclosure, the hole blocking layer may be formed by evaporation.

[0147] In an exemplary embodiment of the present disclosure, the material of the electron transport layer may include an aromatic heterocyclic electron transport material, for example, it may include any one or more of a benzimidazole derivative electron transport material, an imidazopyridine derivative electron transport material, a benzimidazolephenanthridine derivative electron transport material, a pyrimidine derivative electron transport material, a triazine derivative electron transport material, a quinoline derivative electron transport material, an isoquinoline derivative electron transport material, and a phenanthroline derivative electron transport material.

[0148] For another example, the material of the electron transport layer may include any one or more of 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7), 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenyl)-1,2,4-triazole (TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenyl)-1,2,4-triazole (p-EtTAZ), bathophenanthroline (BPhen), (BCP), and 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (BzOs).

[0149] In an exemplary embodiment of the present disclosure, the electron transport layer may be formed by evaporation.

[0150] In an exemplary embodiment of the present disclosure, the material of the electron injection layer may include any one or more of an alkali metal electron injection material and a metal electron injection material.

[0151] For example, the electron injection layer material may include any one or more of LiF, Yb, Mg, and Ca.

[0152] In an exemplary embodiment of the present disclosure, the electron injection layer may be formed by evaporation.

[0153] In an exemplary embodiment of the present disclosure, the cathode may be formed of a metal with a relatively low work function, such as Al, Ag, or Mg, or an alloy containing a metal material with a low work function.

[0154] An embodiment of the present disclosure further provides a display device, which includes the display substrate provided in the above embodiment of the present disclosure.

[0155] The display device can be any product or component with a display function, such as a mobile phone, a tablet computer, a television, a monitor, a laptop computer, a digital photo frame, a navigator, a car display, a smart watch, a smart bracelet, or the like.

[0156] The present disclosure further provides a method for manufacturing the display substrate provided in the above embodiment of the present disclosure, the manufacturing method comprising:

[0157] forming a first electrode layer on one side of the substrate;

[0158] forming a first hole transport layer and a second hole transport layer in sequence on a side of the first electrode layer away from the substrate;

[0159] forming a red light-emitting auxiliary layer located in a red sub-pixel on a side of the second hole transport layer away from the substrate;

[0160] A red light-emitting layer located in a red sub-pixel is formed on a side of the red light-emitting auxiliary layer away from the substrate, and a green light-emitting layer and a blue light-emitting layer are formed on a side of the second hole transport layer away from the substrate, respectively located in a green sub-pixel and a blue sub-pixel, wherein the red light-emitting layer, the green light-emitting layer and the blue light-emitting layer constitute a light-emitting layer, and the light-emitting layer, the red light-emitting auxiliary layer, the first hole transport layer and the second hole transport layer constitute a light-emitting unit;

[0161] forming a charge generation layer on a side of the light emitting unit away from the substrate;

[0162] forming at least one light-emitting unit on a side of the charge generation layer away from the substrate, and forming a charge generation layer between two adjacent light-emitting units;

[0163] A second electrode layer is formed.

[0164] In an exemplary embodiment of the present disclosure, the method of forming the first hole transport layer and the second hole transport layer may be an evaporation method.

[0165] In an exemplary embodiment of the present disclosure, the red light-emitting auxiliary layer may be formed by an evaporation method.

[0166] In an exemplary embodiment of the present disclosure, the red light emitting layer, the green light emitting layer, and the blue light emitting layer may be formed by an evaporation method.

[0167] The present disclosure also provides a method for reducing a driving voltage of a display substrate, wherein the display substrate includes a red sub-pixel, further comprising: a first electrode layer, a second electrode layer, a plurality of light-emitting units disposed between the first electrode layer and the second electrode layer and connected in series, and a charge generation layer disposed between two adjacent light-emitting units, wherein a microcavity is formed between the first electrode layer and the second electrode layer; the light-emitting unit includes a first hole transport layer, a second hole transport layer, and a light-emitting layer, wherein the light-emitting layer includes a red light-emitting layer located in the red sub-pixel;

[0168] The method for reducing the driving voltage of the display substrate includes: using a hole transport material to form a red light-emitting auxiliary layer located between the red light-emitting layer and the second hole transport layer in the red sub-pixel, and the thickness of the red light-emitting layer accounts for 8% to 16% of the thickness of the microcavity, the thickness of the red light-emitting auxiliary layer accounts for 1% to 5% of the thickness of the microcavity, and the total thickness of the red light-emitting layer and the red light-emitting auxiliary layer in a light-emitting unit accounts for 9% to 17% of the thickness of the microcavity.

[0169] The following describes an exemplary embodiment of the present disclosure to illustrate the application of the solution in reducing the driving voltage of an organic EL device.

[0170] The structure of the EL device is shown in FIG1 , including: an indium tin oxide (ITO) layer formed on a glass substrate as an anode, a hole injection layer HTL (5 nm to 30 nm), a first hole transport layer HTL-1 (15 nm to 25 nm), a second hole transport layer HTL-2 (5 nm to 15 nm), a first red light-emitting auxiliary layer HTL-3 (10 nm to 25 nm), a first red light-emitting layer REML-1 (30 nm to 50 nm), a first green light-emitting layer GEML-1 (30 nm to 50 nm), a first blue light-emitting layer BEML-1 (10 nm to 20 nm), a first hole blocking layer HBL-1 (5 nm to 15 nm), and an N-CGL (15 nm to 25 nm). m), P-CGL (5nm to 15nm), third hole transport layer HTL-4 (15nm to 25nm), fourth hole transport layer HTL-5 (5nm to 15nm), second red light-emitting auxiliary layer HTL-6 (10nm to 25nm), second red light-emitting layer REML-2 (30nm to 50nm), second green light-emitting layer GEML-2 (30nm to 50nm), second blue light-emitting layer BEML-2 (10nm to 20nm), second hole blocking layer HBL-2 ​​(5nm to 15nm), electron transport layer ETL (20nm to 100nm), electron injection layer EIL (1nm to 10nm) and cathode (10nm to 20nm). The structures of the two light-emitting units are exactly the same, that is, HTL-1 is the same as HTL-4, HTL-2 is the same as HTL-5, HTL-3 is the same as HTL-6, and HBL-1 is the same as HBL-2, including the same parameters such as materials, doping ratios, and film thickness.

[0171] The device structure of Example 1 includes: ITO / HIL (10nm) / HTL-1 (19nm) / HTL-2 (10nm) / HTL-3 (17nm) / RH:RD (3wt%, 42nm); GH:GD (10wt%, 40nm); BH:BD (3wt%, 15nm) / HBL-1 (5nm) / N-CGL (1% Li, nm) / P-CGL (5%, 9nm) / HTL-4 (19nm) / HTL-5 (10nm) / HTL-6 (17nm) / RH:RD (3wt%, 42nm); GH:GD (10wt%, 40nm); BH:BD (3wt%, 15nm) / HBL-2 ​​(5nm) / ETL:LIQ (1:1, 35nm) / EIL (1nm) / cathode (15nm).

[0172] The other embodiments and comparative examples differ from embodiment 1 only in that the thickness of the first red light-emitting auxiliary layer HTL-3 (or the second red light-emitting auxiliary layer HTL-6) is different, and the thickness of the first red light-emitting layer REML-1 (or the second red light-emitting layer REML-2) is different.

[0173] The device preparation process includes:

[0174] S10: ultrasonically treating the glass substrate with ITO in a cleaning agent, rinsing it in deionized water, ultrasonically degreasing it in an acetone-ethanol mixed solvent, and baking it in a clean environment until the moisture is completely removed;

[0175] S20: Place the glass substrate with the anode in a vacuum chamber and evacuate to 1×10 -5 Pa to 1×10 -6 Pa, vacuum co-evaporating a hole injection material and a first hole transport material (the doping ratio of the first hole transport material is 5%) on the above-mentioned anode layer film to form a hole injection layer;

[0176] S30: evaporating a first hole transport material on the hole injection layer to form a first hole transport layer;

[0177] S40: evaporating a second hole transport layer material on the first hole transport layer to form a second hole transport layer;

[0178] S50: On the second hole transport layer, a first red light-emitting auxiliary layer (third hole transport layer material) is evaporated in the red sub-pixel region to form the first red light-emitting auxiliary layer;

[0179] S60: Vapor-depositing a first red light-emitting layer, a first green light-emitting layer, and a first blue light-emitting layer in the red, green, and blue sub-pixel regions, respectively, to form a first light-emitting layer;

[0180] S70: vacuum evaporating a first hole blocking layer of the device on the first light-emitting layer;

[0181] S80: depositing N-CGL with a Li doping ratio of 1 wt%, N-CGL with a Li doping ratio of 1 wt%, and P-CGL with a Li doping ratio of 5 wt% on the first hole blocking layer in sequence to form a charge generation layer;

[0182] S90: evaporating a first hole transport material on the charge generation layer to form a third hole transport layer;

[0183] S100: evaporating a second hole transport layer material on the third hole transport layer to form a fourth hole transport layer;

[0184] S110: On the fourth hole transport layer, a second red light-emitting auxiliary layer (made of the third hole transport layer) is evaporated in the red sub-pixel region to form a second red light-emitting auxiliary layer;

[0185] S120: Vapor-depositing a second red light-emitting layer, a second green light-emitting layer, and a second blue light-emitting layer in the red, green, and blue sub-pixel regions, respectively, to form a second light-emitting layer;

[0186] S130: vacuum evaporating a second hole blocking layer of the device on the second light-emitting layer;

[0187] S140: vacuum evaporating an electron transport layer of the device on the second hole blocking layer;

[0188] S150: vacuum evaporating Yb with a thickness of 1 nm on the electron transport layer as an electron injection layer;

[0189] S160: Vapor-depositing a Mg:Ag (1:9) layer on the electron injection layer as the cathode of the device.

[0190] The raw materials used in the above-mentioned embodiments and comparative examples are as follows:

[0191] Metal Li:NW

[0192] The driving voltage and luminous efficiency of the EL devices of the above embodiments and comparative examples are shown in Table 1.

[0193] Table 1 Driving voltage and luminous efficiency of EL devices

[0194] It can be seen that the device of the exemplary embodiment of the present disclosure uses a red light-emitting auxiliary layer instead of a red light-emitting layer of a certain thickness to reduce the driving voltage of the EL device and maintain the luminous efficiency of the EL device substantially unchanged.

[0195] Although the embodiments disclosed in this disclosure are as described above, the contents described are merely embodiments adopted to facilitate understanding of the disclosure and are not intended to limit the disclosure. Any person skilled in the art may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope of the disclosure. However, the scope of patent protection of the disclosure shall still be based on the scope defined by the appended claims.

Claims

1. A display substrate, comprising a red sub-pixel, further comprising: A first electrode layer, a second electrode layer, a plurality of light-emitting units arranged between the first electrode layer and the second electrode layer and connected in series, and a charge generation layer arranged between two adjacent light-emitting units, wherein a microcavity is formed between the first electrode layer and the second electrode layer; the light-emitting unit comprises a first hole transport layer, a second hole transport layer and a light-emitting layer, wherein the light-emitting layer comprises a red light-emitting layer located in the red sub-pixel, at least one of the light-emitting units further comprises a red light-emitting auxiliary layer located in the red sub-pixel, and the red light-emitting auxiliary layer is arranged between the red light-emitting layer and the second hole transport layer, and the red light-emitting auxiliary layer comprises a hole transport material; Wherein, the thickness of each red light-emitting layer accounts for 8% to 16% of the thickness of the microcavity.

2. The display substrate according to claim 1, wherein: The thickness of each of the red light-emitting layers accounts for 8% to 10% of the thickness of the microcavity.

3. The display substrate according to claim 1, wherein: The thickness of each of the red light-emitting auxiliary layers accounts for 1% to 5% of the thickness of the microcavity.

4. The display substrate according to claim 3, wherein: The thickness of each of the red light-emitting auxiliary layers accounts for 3% to 5% of the thickness of the microcavity.

5. The display substrate according to any one of claims 1 to 4, wherein: The total thickness of the red light-emitting layer and the red light-emitting auxiliary layer in one light-emitting unit accounts for 9% to 17% of the thickness of the microcavity.

6. The display substrate according to claim 5, wherein: The second hole transport layer and the red light-emitting auxiliary layer meet the following conditions: HTL-3 -μ HTL-2 ≥1×10 -1 @5000V 1 / 2 m 1 / 2 ; Among them, μ HTL-3 The red light-emitting auxiliary layer is 5000V 1 / 2 m 1 / 2 The migration rate at μ HTL-2 For the second hole transport layer at 5000V 1 / 2 m 1 / 2 The migration rate at .

7. The display substrate according to claim 6, wherein: The red light-emitting auxiliary layer and the red light-emitting layer meet the following conditions: REML -n HTL-3 │<0.1; Among them, n REML is the refractive index of the red light emitting layer; n REML is the refractive index of the red light-emitting auxiliary layer.

8. The display substrate according to claim 6 or 7, wherein: The red light-emitting auxiliary layer and the red light-emitting layer meet the following conditions: 3eV≤│HOMO HTL-3 │-│LUMO HTL-3 │≤3.4eV; │HOMO REML │-│HOMO HTL-3 │<0.2eV; │LUMO REML │-│LUMO HTL-3 │<0.2eV; Among them, HOMO HTL-3 is the highest occupied molecular orbital energy level of the red light-emitting auxiliary layer; LUMO HTL-3 is the lowest unoccupied molecular orbital energy level of the red light-emitting auxiliary layer; HOMO REML is the lowest unoccupied molecular orbital energy level of the red light-emitting layer; LUMO REML It is the lowest unoccupied molecular orbital energy level of the red light emitting layer.

9. The display substrate according to any one of claims 6 to 8, wherein: The first hole transport layer, the second hole transport layer, the red light-emitting auxiliary layer and the red light-emitting layer meet the following conditions: HTL-3 >T HTL-2 ; T HTL-3 <T HTL-1 ; T HTL-3 +T HTL-2 ≥T HTL-1 ; T HTL-3 <T REML ; Among them, T HTL-1 is the thickness of the first hole transport layer; T HTL-2 is the thickness of the second hole transport layer; T HTL-3 is the thickness of the red light-emitting auxiliary layer; T REML is the thickness of the red light emitting layer.

10. The display substrate according to claim 9, wherein: The thickness of each of the red light-emitting layers is 30 nm to 50 nm, and the thickness of each of the red light-emitting auxiliary layers is 10 nm to 25 nm.

11. The display substrate according to any one of claims 6 to 10, further comprising a green sub-pixel and a blue sub-pixel, the light-emitting layer further comprising a green light-emitting layer and a blue light-emitting layer respectively located in the green sub-pixel and the blue sub-pixel, at least one of the light-emitting units further comprising any one or more of a green light-emitting auxiliary layer located in the green sub-pixel and a blue light-emitting auxiliary layer located in the blue sub-pixel; the green light-emitting auxiliary layer comprises a hole transport material, and the blue light-emitting auxiliary layer comprises a hole transport material.

12. The display substrate according to claim 11, wherein: The red light-emitting auxiliary layer, the green light-emitting layer and the blue light-emitting layer meet the following conditions: |HOMO GEML │-│HOMO HTL-3 │≥0.2eV; │HOMO BEML │-│HOMO HTL-3 │≥0.2eV; Among them, HOMO HTL-3 is the highest occupied molecular orbital energy level of the red light-emitting auxiliary layer; HOMO GEML is the highest occupied molecular orbital energy level of the green light-emitting layer; HOMO BEML is the highest occupied molecular orbital energy level of the blue light-emitting layer.

13. The display substrate according to claim 12, wherein: The hole transport materials in the red light-emitting auxiliary layer, the green light-emitting auxiliary layer and the blue light-emitting auxiliary layer are independently selected from any one or more of aromatic amine hole transport materials, carbazole hole transport materials and dimethylfluorene hole transport materials.

14. The display substrate according to claim 13, wherein: The red light-emitting layer includes a red host material and a red guest material, and the doping ratio of the red guest material is 1% to 5%; The red host material includes any one or more of the DCM series red light-emitting materials, and the red guest material includes any one or more of the metal complex type red light-emitting materials.

15. The display substrate according to claim 13, wherein: The green light-emitting layer includes a green host material and a green guest material, and the doping ratio of the green guest material is 5% to 15%; The green host material includes any one or more of coumarin dyes, quinacridone copper derivatives type green light-emitting materials, polycyclic aromatic hydrocarbon type green light-emitting materials, diamine anthracene derivatives type green light-emitting materials and carbazole derivatives type green light-emitting materials, and the green guest material includes any one or more of metal complex type green light-emitting materials.

16. The display substrate according to claim 13, wherein: The blue light-emitting layer includes a blue host material and a blue guest material, and the doping ratio of the blue guest material is 1% to 5%; The blue host material includes any one or more of pyrene derivative blue light-emitting materials, anthracene derivative blue light-emitting materials, fluorene derivative blue light-emitting materials, perylene derivative blue light-emitting materials and styrylamine derivative blue light-emitting materials, and the blue guest material includes any one or more of metal complex blue light-emitting materials.

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

18. A method for manufacturing a display substrate according to any one of claims 1 to 16, comprising: forming a first electrode layer on one side of the substrate; forming a first hole transport layer and a second hole transport layer in sequence on a side of the first electrode layer away from the substrate; forming a red light-emitting auxiliary layer located at a red sub-pixel on a side of the second hole transport layer away from the substrate by an evaporation method; By using an evaporation method, a red light-emitting layer located at a red sub-pixel is formed on a side of the red light-emitting auxiliary layer away from the substrate, and a green light-emitting layer and a blue light-emitting layer are formed on a side of the second hole transport layer away from the substrate, respectively located at a green sub-pixel and a blue sub-pixel, wherein the red light-emitting layer, the green light-emitting layer and the blue light-emitting layer constitute a light-emitting layer, and the light-emitting layer, the red light-emitting auxiliary layer, the first hole transport layer and the second hole transport layer constitute a light-emitting unit; forming a charge generating layer on a side of the light emitting unit away from the substrate; forming at least one light-emitting unit on a side of the charge generation layer away from the substrate, and forming a charge generation layer between two adjacent light-emitting units; A second electrode layer is formed.

19. A method for reducing a driving voltage of a display substrate, the display substrate comprising a red sub-pixel, further comprising: A first electrode layer, a second electrode layer, a plurality of light-emitting units disposed between the first electrode layer and the second electrode layer and connected in series, and a charge generation layer disposed between two adjacent light-emitting units, wherein a microcavity is formed between the first electrode layer and the second electrode layer; The light-emitting unit includes a first hole transport layer, a second hole transport layer and a light-emitting layer, and the light-emitting layer includes a red light-emitting layer located in the red sub-pixel; The method includes: using a hole transport material to form a red light-emitting auxiliary layer located between the red light-emitting layer and the second hole transport layer and located in the red sub-pixel, and making the thickness of the red light-emitting layer account for 8% to 16% of the thickness of the microcavity, the thickness of the red light-emitting auxiliary layer account for 1% to 5% of the thickness of the microcavity, and the total thickness of the red light-emitting layer and the red light-emitting auxiliary layer in a light-emitting unit account for 9% to 17% of the thickness of the microcavity.

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