CN113555407B

CN113555407B - Organic electroluminescent display substrate, preparation method thereof and display device

Info

Publication number: CN113555407B
Application number: CN202110824961.4A
Authority: CN
Inventors: 井杨坤
Original assignee: BOE Technology Group Co Ltd; Hefei BOE Zhuoyin Technology Co Ltd
Current assignee: BOE Technology Group Co Ltd; Hefei BOE Zhuoyin Technology Co Ltd
Priority date: 2021-07-21
Filing date: 2021-07-21
Publication date: 2024-06-11
Anticipated expiration: 2041-07-21
Also published as: CN113555407A

Abstract

The disclosure provides an organic electroluminescent display substrate, a preparation method thereof and a display device, and belongs to the technical field of display. The organic electroluminescent display substrate comprises a pixel defining layer arranged on a substrate, wherein the pixel defining layer comprises a flat part and an opening part; the organic electroluminescent display substrate further comprises a micro-nano composite film, wherein the micro-nano composite film covers the flat part and the opening part of the pixel defining layer; wherein, the micro-nano composite film covering the flat part can be changed from hydrophobicity to hydrophilicity in the illumination environment; the micro-nano composite film covering the opening part can be changed from hydrophilicity to hydrophobicity in dark state environment.

Description

Organic electroluminescent display substrate, preparation method thereof and display device

Technical Field

The disclosure belongs to the technical field of display, and particularly relates to an organic electroluminescent display substrate, a preparation method thereof and a display device.

Background

An Organic LIGHT EMITTING Diode (OLED) belongs to a novel current type semiconductor light-emitting device, which is a self-luminous technology by controlling the injection of a carrier of the device and the luminous display of a compound excitation Organic material. Compared with a passive light-emitting Liquid crystal display (Liquid CRYSTAL DISPLAY, LCD), the self-light-emitting OLED display has the advantages of high response speed, high contrast, wide viewing angle and the like, is easy to realize flexible display, is widely seen in the industry, and is considered to be a main stream product of the next-generation display technology in the industry.

At present, each functional material layer and cathode metal layer film of the OLED are prepared by a vacuum thermal evaporation process, namely, organic micromolecular materials are heated in a vacuum cavity to sublimate or melt and gasify the organic micromolecular materials into material vapor, and the material vapor is deposited on a glass substrate through openings of a metal mask. However, the high cost of vacuum thermal evaporation limits the wide commercialization of OLED displays. Ink-jet Printing (IJP) has the advantages of high material utilization rate, and the like, is a key technology for solving the cost problem of a large-size OLED display, and has more application potential because the IJP technology has the advantages of saving materials, mild processing conditions, more uniform film formation, and the like compared with the traditional vacuum evaporation process in the preparation of the light-emitting layer of the OLED device. The method is to drop the functional material ink into a predetermined pixel area by using a plurality of nozzles, and then obtain a desired pattern film by drying.

However, as the hydrophilia of different inks is different, for the ink with good hydrophilia, the slope climbing on the inclined inner surface of the retaining wall is higher, a concave film layer is formed, for the ink with poor hydrophilia, a convex film layer is formed in the groove of the retaining wall, so that the film thickness of the luminous element functional layer in each pixel area after drying is uneven, the luminous uniformity of the OLED device is affected, and the quality of the OLED device is reduced.

Disclosure of Invention

The disclosure aims to at least solve one of the technical problems in the prior art, and provides an organic electroluminescent display substrate, a preparation method thereof and a display device.

In a first aspect, embodiments of the present disclosure provide an organic electroluminescent display substrate including a pixel defining layer disposed on a substrate, the pixel defining layer including a flat portion and an opening portion; the organic electroluminescent display substrate further comprises a micro-nano composite film, wherein the micro-nano composite film covers the flat part and the opening part of the pixel defining layer;

Wherein, the micro-nano composite film covering the flat part can be changed from hydrophobicity to hydrophilicity in the illumination environment; the micro-nano composite film covering the opening part can be changed from hydrophilicity to hydrophobicity in dark state environment.

Optionally, the micro-nano composite film comprises at least one of a nano rod array structure, a needle tip array structure and a hexagonal array structure formed by oxide.

Optionally, the oxide includes at least one of zinc oxide, titanium oxide, tin oxide.

Optionally, conductive particles are disposed in the micro-nano composite film covering the flat portion.

In a second aspect, an embodiment of the present disclosure provides a method for preparing an organic electroluminescent display substrate, including:

Providing a substrate;

Forming a pixel defining layer on the substrate base plate through a patterning process, wherein the pixel defining layer comprises a flat part and an opening part;

And forming a micro-nano composite film on the flat part and the opening part.

Optionally, forming a micro-nano composite film on the flat portion and the opening portion specifically includes:

And forming the micro-nano composite film on the flat part and the opening part by adopting a hydrothermal method.

Optionally, the step of forming a micro-nano composite film on the flat portion and the opening portion further includes: and forming an organic electroluminescent device functional layer in the opening.

Optionally, forming an organic electroluminescent device functional layer in the opening specifically includes:

Before the ink drops into the opening, shielding the flat part, and irradiating the micro-nano composite film by ultraviolet light to change the hydrophobicity of the micro-nano composite film covered on the opening into hydrophilicity;

Dropping a certain amount of ink into the opening;

in the ink drying process, the display substrate is placed in a dark state environment, so that the micro-nano composite film covering the opening part is changed from hydrophilicity to hydrophobicity.

Optionally, after forming the organic electroluminescent device functional layer in the opening portion, the method further includes:

And forming an electrode layer of the organic electroluminescent device on the organic electroluminescent device functional layer and the micro-nano composite film.

In a third aspect, embodiments of the present disclosure provide a display device including the above-described organic electroluminescent display substrate.

Drawings

Fig. 1 is a schematic plan view of an exemplary organic electroluminescent display substrate;

FIG. 2 is a circuit diagram of a pixel driving circuit in the display substrate shown in FIG. 1;

FIG. 3 is a cross-sectional view of the pixel driving circuit of FIG. 2 at the location where a second light-emission control transistor is connected to a light-emitting device;

fig. 4 is a schematic structural view of another exemplary organic electroluminescent display substrate;

FIG. 5 is a schematic illustration of ink forming a concave film layer within the pixel defining layer openings shown in FIG. 4;

FIG. 6 is a schematic illustration of ink forming a convex film layer within the pixel defining layer openings shown in FIG. 4;

fig. 7 is a schematic structural diagram of an organic electroluminescent display substrate according to an embodiment of the present disclosure;

FIG. 8 is a schematic structural diagram of another organic electroluminescent display substrate according to an embodiment of the present disclosure;

fig. 9 is a flowchart of a method for manufacturing an organic electroluminescent display substrate according to an embodiment of the present disclosure.

Detailed Description

In order that those skilled in the art will better understand the technical solutions of the present disclosure, the present disclosure will be described in further detail with reference to the accompanying drawings and detailed description.

Unless defined otherwise, technical or scientific terms used in this disclosure should be given the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and the like, as used in this disclosure, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Likewise, the terms "a," "an," or "the" and similar terms do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed.

It should be noted that, the "patterning process" refers to a step of forming a structure having a specific pattern, which may be a photolithography process, including one or more steps of forming a material layer, coating photoresist, exposing, developing, etching, photoresist stripping, and the like; of course, the "patterning process" may also be an imprinting process, an inkjet printing process, or other processes.

Fig. 1 is a schematic plan view of an exemplary organic electroluminescent display substrate, and as shown in fig. 1, the display substrate includes a substrate, and a plurality of pixel units 0 formed on the substrate, and each pixel unit 0 is provided with a pixel driving circuit and an OLED device. The pixel driving circuit may include a 7T1C (i.e., seven transistors and one capacitor) structure including, for example, a driving transistor, a data writing transistor, a storage capacitor, a threshold compensation transistor, a first reset transistor, a second reset transistor, a first light emission control transistor, and a second light emission control transistor. Fig. 2 is a circuit diagram of a pixel driving circuit in the display substrate shown in fig. 1, referring to fig. 2, a source electrode of the data writing transistor T4 is electrically connected to a source electrode of the driving transistor T3, a drain electrode of the data writing transistor T4 is configured to be electrically connected to the data line Vd to receive a data signal, and a gate electrode of the data writing transistor T4 is configured to be electrically connected to the first scan signal line Ga1 to receive a scan signal; the first polar plate CC1 of the storage capacitor Cst is electrically connected with the first power supply voltage end VDD, and the second polar plate CC2 of the storage capacitor Cst is electrically connected with the grid electrode of the driving transistor T3; the source of the threshold compensation transistor T2 is electrically connected to the drain of the driving transistor T3, the drain of the threshold compensation transistor T2 is electrically connected to the gate of the driving transistor T3, and the gate of the threshold compensation transistor T2 is configured to be electrically connected to the second scan signal line Ga2 to receive the compensation control signal; the source of the first reset transistor T1 is configured to be electrically connected to the first reset power supply terminal Vinit1 to receive the first reset signal, the drain of the first reset transistor T1 is electrically connected to the gate of the driving transistor T3, and the gate of the first reset transistor T1 is configured to be electrically connected to the first reset control signal line Rst1 to receive the first sub-reset control signal; the source of the second reset transistor T7 is configured to be electrically connected to the first reset power terminal Vinit1 to receive the first reset signal, the drain of the second reset transistor T7 is electrically connected to the first electrode D1 of the light emitting device D, and the gate of the second reset transistor T7 is configured to be electrically connected to the second reset control signal line Rst2 to receive the second sub-reset control signal; the source of the first light emitting control transistor T5 is electrically connected to the first power supply voltage terminal VDD, the drain of the first light emitting control transistor T5 is electrically connected to the source of the driving transistor T3, and the gate of the first light emitting control transistor T5 is configured to be electrically connected to the first light emitting control signal line EM1 to receive the first light emitting control signal; the source of the second light emission control transistor T6 is electrically connected to the drain of the driving transistor T3, the drain of the second light emission control transistor T6 is electrically connected to the first electrode D1 of the light emitting device D, and the gate of the second light emission control transistor T6 is configured to be electrically connected to the second light emission control signal line EM2 to receive the second light emission control signal; the second electrode D3 of the light emitting device D is electrically connected to the second power voltage terminal VSS.

Fig. 3 is a cross-sectional view of the pixel driving circuit of fig. 2 at a location where a second light emission control transistor is connected to a light emitting device, and as shown in fig. 3, a driving circuit layer may be formed on a substrate. For example, as shown in fig. 3, the driving circuit layer may be formed on the buffer layer 102. The driving circuit layer may include an interlayer dielectric layer 103, where the interlayer dielectric layer 103 is made of an inorganic material, for example: inorganic materials such as silicon oxide and silicon nitride to achieve the effects of blocking water and oxygen and blocking alkaline ions.

In detail, the driving circuit layer further includes a thin film transistor and a capacitor structure.

As shown in fig. 3, the thin film transistor may be a top gate type, and the thin film transistor may include an active layer 104, a first gate insulating layer 105, a gate 106, a second gate insulating layer 108, an interlayer dielectric layer 103, a source 110, and a drain 111. Specifically, the active layer 104 may be formed on the buffer layer 102, the first gate insulating layer 105 covers the buffer layer 102 and the active layer 104, the gate electrode 106 is formed on a side of the first gate insulating layer 105 facing away from the active layer 104, the second gate insulating layer 108 covers the gate electrode 106 and the first gate insulating layer 105, the interlayer dielectric layer 103 covers the second gate insulating layer 108, the source electrode 110 and the drain electrode 111 are formed on a side of the interlayer dielectric layer 103 facing away from the substrate and on opposite sides of the gate electrode 106, respectively, and the source electrode 110 and the drain electrode 111 may be in contact with opposite sides of the active layer 104 through vias (e.g., metal vias), respectively. It should be appreciated that the thin film transistor may also be bottom gate.

As shown in fig. 3, the capacitor structure may include a first electrode 130 and a second electrode 131, where the first electrode 130 is disposed on the same layer as the gate 106, and the second electrode 131 is disposed between the second gate insulating layer 108 and the interlayer dielectric layer 103 and opposite to the first electrode 130.

As shown in fig. 3, a display device is located in the display area, and the display device may include a first electrode 112 and a pixel defining portion 113 sequentially formed on the interlayer dielectric layer 103, it being understood that the display device may further include a light emitting portion 114a and a second electrode 115.

In detail, when the thin film transistor is a top gate type, a planarization layer may be formed before the display device is manufactured, and the planarization layer may have a single-layer structure or a multi-layer structure; the planarization layer is typically made of an organic material, for example: photoresist, acrylic-based polymer, silicon-based polymer, and the like; as shown in fig. 3, the planarization layer may include a planarization portion 116, where the planarization portion 116 is formed between the interlayer dielectric layer 103 and the first electrode 112. The first electrode 112 may be electrically connected to the drain 111 through a metal via, and the first electrode 112 may be an anode made of materials such as ITO (indium tin oxide), indium Zinc Oxide (IZO), zinc oxide (ZnO), etc.; the pixel defining portion 113 may cover the planarization portion 116, and the pixel defining portion 113 may be made of an organic material, for example: organic materials such as photoresist, and the pixel defining portion 113 may have a pixel opening exposing the first electrode 112; the light emitting part 114a is disposed in the pixel opening and formed on the first electrode 112, and the light emitting part 114a may include a small molecular organic material or a polymer molecular organic material, may be a fluorescent light emitting material or a phosphorescent light emitting material, may emit red light, green light, blue light, or may emit white light, etc.; in addition, according to different practical needs, in different examples, the light emitting portion 114a may further include functional layers such as an electron injection layer, an electron transport layer, a hole injection layer, and a hole transport layer; the second electrode 115 covers the light emitting portion 114a, and the polarity of the second electrode 115 is opposite to that of the first electrode 112; the second electrode 115 may be a cathode made of a metal material such as lithium (Li), aluminum (Al), magnesium (Mg), silver (Ag), etc.

As shown in fig. 3, the first electrode 112, the light emitting portion 114a, and the second electrode 115 may form one light emitting subpixel 1d. The display device may include a plurality of light emitting sub-pixels 1d arranged in an array. In addition, the first electrodes 112 of the light-emitting sub-pixels 1d are independent from each other, and the second electrodes 115 of the light-emitting sub-pixels 1d are connected over the entire surface; that is, the second electrode 115 is an entire surface structure provided on the display substrate 10, and is a common electrode for a plurality of display devices.

Fig. 4 is a schematic structural view of another exemplary organic electroluminescent display substrate, fig. 5 is a schematic view of ink forming a concave film layer in the pixel defining layer opening shown in fig. 4, and fig. 5 is a schematic view of ink forming a convex film layer in the pixel defining layer opening shown in fig. 4. In fig. 4 to 6, only the substrate 1, the driving circuit 2, the planarizing layer 3, the anode 4 of the organic electroluminescent device, and the pixel defining layer 5 are schematically shown.

As shown in fig. 4 to 6, the organic electroluminescent display substrate includes a substrate 1, a pixel driving circuit 2 provided on the substrate 1, a planarization layer 3 provided on a side of the pixel driving circuit 2 facing away from the substrate 1, an anode 4 of the organic electroluminescent device provided on a side of the planarization layer 3 facing away from the substrate 1, a pixel defining layer 5 provided on a side of the anode 4 of the organic electroluminescent device facing away from the substrate 1, the pixel defining layer 5 having a flat portion 52 and an opening portion 51, and an organic functional layer 6 may be provided in the opening portion 51 of the pixel defining layer 5.

In the process of forming the organic functional layer 6 by the inkjet printing technology, since different inks have different hydrophilicities, the inks having good hydrophilicities can climb up on the inclined inner surfaces of the openings 51 to form a concave film layer (as shown in fig. 5), and the inks having poor hydrophilicities can form a convex film layer (as shown in fig. 6) in the openings 51, so that the film thickness of the light emitting element functional layer 6 in each pixel region after drying is uneven, the uniformity of the light emission of the organic electroluminescent display device OLED is affected, and the quality of the organic electroluminescent display device OLED is degraded.

In order to solve at least one of the above technical problems, the present disclosure provides an organic electroluminescent display substrate, a preparation method thereof, and a display device, and the organic electroluminescent display substrate, the preparation method thereof, and the display device provided by the present disclosure are described in further detail below with reference to the accompanying drawings and detailed description.

In a first aspect, fig. 7 is a schematic structural diagram of an organic electroluminescent display substrate according to an embodiment of the present disclosure, and as shown in fig. 7, an embodiment of the present disclosure provides an organic electroluminescent display substrate, where the organic electroluminescent display substrate includes a substrate 11, a pixel driving circuit 12, a planarization layer 13, an anode layer 14 of an organic electroluminescent device, a pixel defining layer 15, and a micro-nano composite film 16.

Specifically, the pixel driving circuit 12 is disposed on the substrate 11, a planarization layer 13 is disposed on a side of the pixel driving circuit 12 facing away from the substrate 11, an anode layer 14 of an organic electroluminescent device is disposed on a side of the planarization layer 13 facing away from the substrate, a pixel defining layer 15 is disposed on a side of the anode layer 14 of the organic electroluminescent device facing away from the substrate 11, and the pixel defining layer 15 includes an opening 151 and a planarization portion 152 disposed around the opening. The micro-nano composite film 16 covers the opening 151 and the flat 152 of the pixel defining layer, and the micro-nano composite film 16 has hydrophobicity, but in the case of light irradiation, the micro-nano composite film may be changed from hydrophobicity to hydrophilicity, and in the dark state environment, the micro-nano composite film converted to hydrophilicity may also be changed to hydrophobicity. In the present embodiment, the micro-nano composite film 16 covering the opening 151 may change from hydrophobic to hydrophilic in the light environment, and the micro-nano composite film 16 covering the opening 151 may change from hydrophilic to hydrophobic in the dark environment.

In the present embodiment, since the micro-nano composite film 16 covering the opening 151 may be changed from hydrophobic to hydrophilic in the light environment, the micro-nano composite film 16 covering the opening 151 may be changed from hydrophilic to hydrophobic in the dark environment. Thus, before the ink drops into the openings, the micro-nano composite film 16 covering the flat portions 152 can be blocked, the micro-nano composite film 16 covering the openings 151 is irradiated with light, and the irradiated micro-nano composite film 16 covering the openings 151 changes from hydrophobic to hydrophilic; after the ink drops into the opening 151, the micro-nano composite film 16 covering the flat portion 152 is hydrophobic, and the micro-nano composite film 16 covering the opening 151 is divided into hydrophilic, so that the micro-nano composite film 16 covering the opening 151 has a tensile force on the ink, the micro-nano composite film 16 covering the flat portion 152 has a repulsive force on the ink, and the uniformity of the ink under the action of the two forces is increased, so that the uniform film formation of the ink in the opening 151 of the pixel defining layer 15 is ensured, and the light emitting uniformity of the organic electroluminescent device is effectively improved. Meanwhile, in the ink drying process, the organic electroluminescent display substrate is placed in a dark state environment, and the micro-nano composite film 16 can be changed from hydrophilic to hydrophobic in the dark state environment, so that the micro-nano composite film 16 covering the opening 151 is changed from hydrophilic to hydrophobic, and thus, the surface properties of the organic functional film 16 can be restored, and the identity of the organic functional film surface can be realized.

In some embodiments, the micro-nano composite film 16 includes at least one of a nanorod array structure, a needle-tip array structure, and a hexagonal array structure formed of an oxide. Specifically, the oxide may include at least one of zinc oxide, titanium oxide, and tin oxide.

The following description will take the oxide in the micro-nano composite film 16 as titanium dioxide TiO2 as an example: titanium dioxide TiO2 is a semiconductor material with wide application prospect, and has excellent physical and chemical characteristics, so that the titanium dioxide TiO2 has attractive application prospect in the aspects of solar cells, photocatalytic degradation of pollutants, sensors, glass antifogging and the like, and becomes a hot spot for current domestic and foreign research. The existing titanium dioxide film preparation methods include a hydrothermal method, plasma spraying, electrodeposition, an electrochemical anodic oxidation method, a sol-gel method and the like. It is known that a film layer formed of titanium oxide has hydrophobicity. In this embodiment, a layer of TiO2 nano-film layer is deposited and grown on the surface of the pixel defining layer 15, and a hydrothermal method is used to grow for two hours at 160 ℃, so that a TiO2 micro-nano composite film with micro-nano scale is prepared on the surface of the pixel defining layer 15, the TiO2 micro-nano composite film has composite structure clusters, the size of the composite structure clusters is 0.1-0.2 um, and the composite structure cluster group is composed of a TiO2 nanorod array with a size of 10-30 nm. Because the TiO2 micro-nano composite film has a large number of pores, the infiltration of liquid drops can be prevented by the large number of pores, and therefore, the TiO2 micro-nano composite film has good hydrophobicity. In addition, after the surface of the cluster of the composite structure diagram is irradiated by ultraviolet light or high energy light, the composite structure is changed in the forward direction, and the TiO2 micro-nano composite film becomes high hydrophilic. In dark state environment (i.e. no light irradiation or trace light irradiation), the TiO2 micro-nano composite film can become hydrophobic after releasing energy.

In this embodiment, the TiO2 micro-nano composite film is formed by a hydrothermal method, and after the TiO2 micro-nano composite film is irradiated by ultraviolet light or high energy light, the composite structure is changed in the forward direction, and the TiO2 micro-nano composite film becomes highly hydrophilic. The TiO2 micro-nano composite film becomes hydrophobic after releasing energy without irradiation or under dark light.

In some embodiments, the micro-nano composite film with various morphologies can be prepared by changing the concentration of the hydrothermal growth solution, the ion additive, the growth time and other conditions, and the micro-nano composite film can comprise a needlepoint array formed by oxide, a nano rod array, a hexagonal micron disc and the like.

The oxide in the micro-nano composite film can be tin dioxide, zinc oxide and the like, and the method for preparing the micro-nano composite film by using the oxide is the same as the principle of forming the micro-nano composite film by using titanium dioxide, and is not illustrated one by one.

In some embodiments, as shown in fig. 7, the organic electroluminescent display substrate further includes an organic functional layer 17 and a cathode layer 18 of the organic electroluminescent device. Wherein the organic functional layer 17 is disposed on the side of the micro-nano composite film 16 facing away from the substrate 11 and formed in the opening 151 of the pixel defining layer 15. The cathode layer 18 of the organic electroluminescent device is arranged on the side of the micro-nano composite film 16 facing away from the substrate 11. The organic functional layer 17 is generally composed of one or more layers of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and the like. As shown in fig. 7, the top of the organic functional layer 17 is spaced from the micro-nano composite film 16 by a certain distance to prevent short circuit, and a person skilled in the art can select a suitable distance according to a specific structure, which will not be described in detail herein.

In some embodiments, as shown in fig. 8, the micro-nano composite film 16 covering the flat portion 152 of the pixel defining layer is uniformly provided with conductive particles 19, and the conductive particles 19 may be conductive metal particles or conductive alloy particles, or a novel conductive material, such as graphene, or the like.

In this embodiment, since the conductive particles 19 are uniformly disposed in the micro-nano composite film 16 covering the flat portion 152 of the pixel defining layer 15, the micro-nano composite film 16 covering the flat portion 152 of the pixel defining layer 15 is overlapped with the cathode 18 of the organic electroluminescent device to form a parallel structure, so that the resistance of the cathode 17 can be reduced, the voltage drop of the cathode film is reduced, and the uniformity of the brightness of the OLED luminescent device is improved.

In a second aspect, an embodiment of the present disclosure provides a method for preparing an organic electroluminescent display substrate, as shown in fig. 9, including:

S101, providing a substrate base plate.

The substrate base is used as a support of an electrode layer and an organic functional film layer in the organic electroluminescent device, has good light transmission performance in a visible light region, certain water vapor and oxygen permeation prevention capability and good surface flatness, and can be generally made of glass, a flexible substrate, an array substrate or the like. If a flexible substrate is selected, it may be made of polyesters, phthalimide or thinner metals.

S102, sequentially forming a pixel driving circuit and a planarization layer on a substrate. Forming the pixel driving circuit on the substrate base plate may include, for example: and forming a grid electrode, a grid insulating layer, an active layer, a source electrode and a drain electrode on the substrate in sequence, wherein the drain electrode is connected with the pixel electrode through a via hole arranged on the protective layer. The gate electrode, the gate insulating layer, the active layer, the source electrode, and the drain electrode constitute the structure of the thin film transistor 300.

S103, forming an anode layer of the organic electroluminescent device on one side of the planarization layer away from the substrate. The anode is typically made of inorganic metal oxides (e.g., indium Tin Oxide (ITO), zinc oxide (ZnO), etc.), organic conductive polymers (e.g., poly 3, 4-ethylenedioxythiophene/polystyrene sulfonate (PEDOT: PSS), polyaniline (PANI), etc.), or high work function metallic materials (e.g., gold, copper, silver, platinum, etc.).

And S104, forming a pixel limiting layer on one side of the anode layer, which is away from the substrate, through a patterning process, wherein the pixel limiting layer comprises an opening part and a flat part which is arranged around the opening part. Specifically, the openings and the flat portions in the pixel defining layer may be formed by exposure, development, and etching processes using MASK of the pixel defining layer.

S105, forming a micro-nano composite film on the opening part and the flat part. Alternatively, a micro-nano composite film may be formed on the opening portion and the flat portion using PECVD or hydrothermal method.

For example, a hydrothermal method is adopted to grow for two hours at 160 ℃, a micro-nano composite film with micro-nano scale is prepared on the surface of the pixel limiting layer, the micro-nano composite film is provided with composite structure clusters, the size of the composite structure clusters is 0.1-0.2um, and the composite structure cluster consists of a 10-30nm nanorod array. The micro-nano composite film has a large number of pores, and the infiltration of liquid drops can be prevented by the large number of pores, so that the micro-nano composite film has good hydrophobicity. In addition, after the surface of the composite structure diagram cluster is irradiated by ultraviolet light or high energy light, the composite structure is changed in the forward direction, and the micro-nano composite film is changed into high hydrophilicity; the micro-nano composite film can also become hydrophobic after releasing energy without irradiation or under dark light.

S106, forming a functional layer of the organic electroluminescent device in the opening.

The functional layer of the organic electroluminescent device is generally composed of one or more layers of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and the like. The material of the hole injection layer includes any one of 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-hexaazabenzophenanthrene (HAT-CN), 2,3,5, 6-tetrafluoro-7, 7', 8' -tetracyanodimethyl p-benzene (F4-TCNQ), and ammonium tris (4-bromophenyl) hexachloroantimonate (TBAHA). The hole transport layer may be made of an aromatic diamine compound, a triphenylamine compound, an aromatic triamine compound, a biphenyldiamine derivative, a triarylamine polymer, a metal complex, or a carbazole polymer, and is preferably: any one of N, N '-bis (1-naphthyl) -N, N' -diphenyl-1, 1 '-biphenyl-4-4' -diamine (NPB), triphenyldiamine derivative (TPD), TPTE, 1,3, 5-tris (N-3-methylphenyl-N-phenylamino) benzene (TDAB). The light emitting layer 3 may be made of an undoped fluorescent light emitting organic material composed of a light emitting material having a hole transporting capability not lower than an electron transporting capability, or made of a fluorescent material doped organic material composed of a fluorescent dopant and a host material, or made of a phosphorescent material doped organic material composed of a phosphorescent dopant and a host material. The material of the electron transport layer 6 includes any one of 2- (4-biphenyl) -5-Phenyloxadiazole (PBD), 2, 5-bis (1-naphthyl) -1,3, 5-oxadiazole (BND), and 2,4, 6-triphenoxy-1, 3, 5-Triazine (TRZ). The material of the electron injection layer 7 is any one of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, lithium oxide, and lithium metaborate.

Optionally, forming the functional layer (S106) of the organic electroluminescent device in the opening portion specifically includes:

S1061, before ink drops into the opening, shielding the micro-nano composite film covering the flat part, and irradiating the micro-nano composite film with ultraviolet light to change the hydrophobicity of the micro-nano composite film covering the opening into hydrophilicity;

S1062, dropping a certain amount of ink into the opening of the pixel defining layer;

s1063, in the ink drying process, placing the display substrate in a dark state environment to change the micro-nano composite film covering the opening part from hydrophilicity to hydrophobicity.

S107, forming a cathode layer of the organic electroluminescent device on the functional layer of the organic electroluminescent device and the micro-nano composite film.

The cathode typically employs a low work function metallic material such as: lithium, magnesium, calcium, strontium, aluminum, indium, etc. or alloys of the above metals with copper, gold, silver; or a very thin buffer insulating layer (such as lithium fluoride LiF, cesium carbonate CsCO3, etc.) and the metal or alloy.

It is to be understood that the above embodiments are merely exemplary embodiments employed to illustrate the principles of the present disclosure, however, the present disclosure is not limited thereto. Various modifications and improvements may be made by those skilled in the art without departing from the spirit and substance of the disclosure, and are also considered to be within the scope of the disclosure.

Claims

1. An organic electroluminescent display substrate, comprising a pixel defining layer disposed on a substrate, the pixel defining layer comprising a flat portion and an opening portion; the organic electroluminescent display substrate further comprises a micro-nano composite film, wherein the micro-nano composite film covers the flat part and the opening part of the pixel defining layer;

Wherein the micro-nano composite film covering the opening part changes from hydrophobicity to hydrophilicity in an illumination environment; the micro-nano composite film covering the opening part is changed from hydrophilicity to hydrophobicity in a dark state environment; the micro-nano composite film comprises at least one of a nano rod array structure, a needle tip-shaped array structure and a hexagonal array structure which are formed by oxides;

The oxide comprises titanium dioxide.

2. The organic electroluminescent display substrate according to claim 1, wherein conductive particles are provided in the micro-nano composite film covering the flat portion.

3. A method for manufacturing an organic electroluminescent display substrate, comprising:

Providing a substrate;

Forming a micro-nano composite film on the flat part and the opening part; the micro-nano composite film comprises at least one of a nano rod array structure, a needle tip-shaped array structure and a hexagonal array structure which are formed by oxides; the oxide comprises titanium dioxide;

Wherein the micro-nano composite film covering the opening part changes from hydrophobicity to hydrophilicity in an illumination environment; the micro-nano composite film covering the opening part is changed from hydrophilicity to hydrophobicity in dark state environment.

4. The method of manufacturing an organic electroluminescent display substrate according to claim 3, wherein forming the micro-nano composite film on the flat portion and the opening portion, specifically comprises:

5. The method of manufacturing an organic electroluminescent display substrate according to claim 4, further comprising, after the step of forming the micro-nano composite film on the flat portion and the opening portion:

And forming an organic electroluminescent device functional layer in the opening.

6. The method for manufacturing an organic electroluminescent display substrate according to claim 5, wherein forming the organic electroluminescent device functional layer in the opening portion comprises:

Dropping a certain amount of ink into the opening;

7. The method of manufacturing an organic electroluminescent display substrate according to claim 6, further comprising, after forming the organic electroluminescent device functional layer in the opening portion:

8. A display device comprising the display substrate according to any one of claims 1-2.