CN113555407A

CN113555407A - Organic electroluminescent display substrate, preparation method thereof and display device

Info

Publication number: CN113555407A
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: 2021-10-26
Anticipated expiration: 2041-07-21
Also published as: CN113555407B

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 of the present disclosure includes 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 also comprises a micro-nano composite film, and the micro-nano composite film covers the flat part and the opening part of the pixel limiting layer; 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 a 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

Organic Light Emitting Diodes (OLEDs) belong to a novel current type semiconductor Light Emitting device, and belong to an autonomous Light Emitting technology by controlling injection of current carriers of the device and compositely exciting Light Emitting display of Organic materials. Compared with a passive light emitting Liquid Crystal Display (LCD), the OLED Display capable of emitting light autonomously has the advantages of fast response speed, high contrast, wide viewing angle, and the like, is easy to realize flexible Display, is generally seen in the industry, and is considered in the industry to be a mainstream product of the next generation Display technology.

At present, each functional material layer and the cathode metal layer film of the OLED are all prepared by a vacuum thermal evaporation process, that is, an organic small molecular material is heated in a vacuum cavity to be sublimated or melted and gasified into material vapor, and the material vapor is deposited on a glass substrate through an opening of a metal mask. But the preparation cost is high due to vacuum thermal evaporation, which limits the wide-range commercialization of the OLED display. The Ink-jet printing (IJP) has the advantages of high material utilization rate and the like, is a key technology for solving the problem of cost of a large-size OLED display, and compared with the traditional vacuum evaporation process, the IJP technology has the advantages of material saving, mild process conditions, more uniform film forming and the like in the preparation of a light-emitting layer of an OLED device, so that the IJP technology has more application potential. The method is to drop a functional material ink into a predetermined pixel region using a plurality of nozzles, and then obtain a desired pattern film by drying.

However, due to the different hydrophilicity of different inks, for an ink with good hydrophilicity, the ink will climb up the inclined inner surface of the retaining wall to form a concave film layer, and for an ink with poor hydrophilicity, a convex film layer will be formed in the groove of the retaining wall, so that the thickness of the film of the light-emitting element functional layer in each pixel region after drying is not uniform, which not only affects the uniformity of light emission of the OLED device, but also degrades the quality of the OLED device.

Disclosure of Invention

The present disclosure is directed to at least one of the technical problems in the prior art, and provides an organic electroluminescent display substrate, a method for manufacturing the same, 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, and the micro-nano composite film covers the flat part and the opening part of the pixel limiting layer;

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 a dark state environment.

Optionally, the micro-nano composite film comprises at least one of a nanorod array structure, a pinpoint array structure and a hexagonal array structure formed by oxides.

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

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

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

providing a substrate base plate;

forming a pixel defining layer on the substrate through a patterning process, the pixel defining layer including a flat portion and an opening portion;

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

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

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

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

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

before the ink is dripped into the opening part, the flat part is shielded, and the micro-nano composite film is irradiated by ultraviolet light, so that the micro-nano composite film covering the opening part is changed from hydrophobicity to hydrophilicity;

dropping a predetermined amount of ink into the opening;

and 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, 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, the present disclosure provides a display device including the 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 a position where a second 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 view of ink forming a concave film layer within the pixel defining layer opening shown in FIG. 4;

FIG. 6 is a schematic view of the ink forming a convex membrane layer within the pixel defining layer opening 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 provided in the practice 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

For a better understanding of the technical aspects of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.

Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. Also, the use of the terms "a," "an," or "the" and similar referents 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 the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

It should be noted that the "patterning process" refers to a step of forming a structure having a specific pattern, and may be a photolithography process, where the photolithography process includes one or more steps of forming a material layer, coating a photoresist, exposing, developing, etching, and stripping the photoresist; 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 base plate, and a plurality of pixel units 0 formed on the substrate base plate, and each pixel unit 0 has a pixel driving circuit and an OLED device disposed therein. 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 compensating transistor, a first reset transistor, a second reset transistor, a first light emission controlling transistor, and a second light emission controlling transistor. Fig. 2 is a circuit diagram of a pixel driving circuit in the display substrate shown in fig. 1, and referring to fig. 2, a source of the data writing transistor T4 is electrically connected to a source of the driving transistor T3, a drain 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 of the data writing transistor T4 is configured to be electrically connected to the first scanning signal line Ga1 to receive a scanning signal; a first plate CC1 of the storage capacitor Cst is electrically connected to the first power voltage terminal VDD, and a second plate CC2 of the storage capacitor Cst is electrically connected to the gate of the driving transistor T3; a source of the threshold compensation transistor T2 is electrically connected to a drain of the driving transistor T3, a drain of the threshold compensation transistor T2 is electrically connected to a gate of the driving transistor T3, and a gate of the threshold compensation transistor T2 is configured to be electrically connected to the second scan signal line Ga2 to receive a compensation control signal; a source of the first reset transistor T1 is configured to be electrically connected to a first reset power source terminal Vinit1 to receive a first reset signal, a drain of the first reset transistor T1 is electrically connected to a gate of the driving transistor T3, and a gate of the first reset transistor T1 is configured to be electrically connected to a first reset control signal line Rst1 to receive a first sub-reset control signal; a source of the second reset transistor T7 is configured to be electrically connected to the first reset power source terminal Vinit1 to receive the first reset signal, a drain of the second reset transistor T7 is electrically connected to the first electrode D1 of the light emitting device D, and a 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; a source of the first light emission controlling transistor T5 is electrically connected to the first power voltage terminal VDD, a drain of the first light emission controlling transistor T5 is electrically connected to the source of the driving transistor T3, and a gate of the first light emission controlling transistor T5 is configured to be electrically connected to the first light emission controlling signal line EM1 to receive the first light emission controlling signal; a source of the second light emission controlling transistor T6 is electrically connected to the drain of the driving transistor T3, a drain of the second light emission controlling transistor T6 is electrically connected to the first electrode D1 of the light emitting device D, and a gate of the second light emission controlling transistor T6 is configured to be electrically connected to the second light emission controlling signal line EM2 to receive a second light emission controlling signal; the second electrode D3 of the light emitting device D is electrically connected to a second power voltage terminal VSS.

Fig. 3 is a cross-sectional view of the pixel driving circuit of fig. 2 at a connection position of a second light emission control transistor and a light emitting device, and as shown in fig. 3, a driving circuit layer may be formed on a substrate base plate. 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, and the interlayer dielectric layer 103 is made of an inorganic material, for example: silicon oxide, silicon nitride and other inorganic materials to reach the effect of blocking water, oxygen and alkali 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 electrode 106, a second gate insulating layer 108, an interlayer dielectric layer 103, a source electrode 110, and a drain electrode 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 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 away from the substrate and are respectively located on two opposite sides of the gate electrode 106, and the source electrode 110 and the drain electrode 111 may respectively contact two opposite sides of the active layer 104 through a via (e.g., a metal via). It should be understood that the thin film transistor may also be a bottom gate type.

As shown in fig. 3, the capacitor structure may include a first plate 130 and a second plate 131, the first plate 130 is disposed on the same layer as the gate 103, and the second plate 131 is disposed between the second gate insulating layer 105 and the interlayer dielectric layer 103 and opposite to the first plate 130.

As shown in fig. 3, the display device is located in the display region, and the display device may include a first electrode 112 and a pixel defining portion 113 sequentially formed on the interlayer dielectric layer 103, and it is 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 of a top gate type, a planarization layer can be manufactured before a display device is manufactured, and the planarization layer can be of a single-layer structure or a multi-layer structure; the planarization layer is usually made of organic materials, such as: materials such as photoresists, acrylic-based polymers, silicon-based polymers, and the like; as shown in fig. 3, the planarization layer may include a planarization portion 116, wherein 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 ITO (indium tin oxide), Indium Zinc Oxide (IZO), zinc oxide (ZnO), or other materials; the pixel defining portion 113 can cover the planarization portion 116, and the pixel defining portion 113 can be made of organic material, such as: an organic material such as photoresist, and the pixel defining part 113 may have a pixel opening exposing the first electrode 112; a light emitting portion 114a is positioned in the pixel opening and formed on the first electrode 112, the light emitting portion 114a may include a small molecule organic material or a polymer molecule 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 actual needs, the light emitting section 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 the polarity 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), or silver (Ag).

As shown in fig. 3, the first electrode 112, the light-emitting portion 114a, and the second electrode 115 may constitute one light-emitting sub-pixel 1 d. The display device may include a plurality of light emitting sub-pixels 1d arranged in an array. Note that 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 a full-surface structure disposed 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 structural view of ink forming a concave film layer in the pixel defining layer opening shown in fig. 4, and fig. 5 is a schematic structural view of ink forming a convex film layer in the pixel defining layer opening shown in fig. 4. Fig. 4 to 6 only show 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.

As shown in fig. 4 to 6, the organic electroluminescent display substrate includes a substrate 1, a pixel driving circuit 2 disposed on the substrate 1, a planarization layer 3 disposed on a side of the pixel driving circuit 2 facing away from the substrate 1, an anode 4 of the organic electroluminescent device disposed on a side of the planarization layer 3 facing away from the substrate 1, a pixel defining layer 5 disposed 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 disposed 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 technique, due to the difference in hydrophilicity between different inks, a concave film layer (as shown in fig. 5) is formed by a high degree of uphill on the inclined inner surface of the opening 52 for an ink with good hydrophilicity, and a convex film layer (as shown in fig. 6) is formed in the opening 51 for an ink with poor hydrophilicity, so that the thickness of the film of the light emitting element functional layer 6 in each pixel region after drying is not uniform, which affects the uniformity of light emission of the organic electroluminescent display device OLED, and degrades the quality of the organic electroluminescent display device OLED.

In order to solve at least one of the above technical problems, the present disclosure provides an organic electroluminescent display substrate, a method for manufacturing the same, and a display device, and the organic electroluminescent display substrate, the method for manufacturing the same, and the display device provided by the present disclosure are further described in detail with reference to the accompanying drawings and the 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 including 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 away from the substrate 11, an anode layer 14 of the organic electroluminescent device is disposed on a side of the planarization layer 13 away from the substrate, a pixel defining layer 15 is disposed on a side of the anode layer 14 of the organic electroluminescent device away from the substrate 11, and the pixel defining layer 15 includes an opening 151 and a flat portion 152 disposed around the opening. The micro-nano composite film 16 covers the opening part 151 and the flat part 152 of the pixel limiting layer, the micro-nano composite film 16 has hydrophobicity, but under the condition of illumination, the micro-nano composite film can be changed from hydrophobicity to hydrophilicity, and under the dark state environment, the micro-nano composite film which is changed into hydrophilicity can also be changed into hydrophobicity. In this embodiment, the micro-nano composite film 16 covering the opening 151 may change from hydrophobic to hydrophilic in an illumination environment, and the micro-nano composite film 16 covering the opening 151 may change from hydrophilic to hydrophobic in a dark environment.

In this embodiment, since the micro-nano composite film 16 covering the opening 151 can be changed from hydrophobic to hydrophilic in the light environment, the micro-nano composite film 16 covering the opening 151 can be changed from hydrophilic to hydrophobic in the dark environment. Thus, before the ink is dropped into the opening, the micro-nano composite film 16 covering the flat portion 152 is shielded, the micro-nano composite film 16 covering the opening 151 is irradiated with light, and the irradiated micro-nano composite film 16 covering the opening 151 is changed from hydrophobic to hydrophilic; after the ink is dripped into the opening part 151, the micro-nano composite film 16 covering the flat part 152 is hydrophobic, and the micro-nano composite film 16 covering the opening part 151 is hydrophilic, so that the micro-nano composite film 16 covering the opening part 151 has tension on the ink, the micro-nano composite film 16 covering the flat part 152 has repulsive force on the ink, and the uniformity of the ink under the two forces is increased, so that the ink is ensured to be uniformly formed in the opening part 151 of the pixel limiting layer 15, and the light emitting uniformity of the organic electroluminescent device is effectively improved. Meanwhile, in the process of drying the ink, the organic electroluminescent display substrate is placed in a dark state environment, and the micro-nano composite film 16 can change from hydrophilicity to hydrophobicity in the dark state environment, so that the micro-nano composite film 16 covering the opening 151 can change from hydrophilicity to hydrophobicity, the surface property of the organic functional film 16 can be recovered, and the homogenization of the surface of the organic functional film is realized.

In some embodiments, the micro-nano composite film 16 includes at least one of a nanorod array structure, a pinpoint 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 be given by taking an example in which the oxide in the micro-nano composite film 16 is titanium dioxide TiO 2: the titanium dioxide TiO2 is a semiconductor material with wide application prospect, and the excellent physical and chemical properties of the titanium dioxide TiO2 make the titanium dioxide TiO2 have attractive application prospect in the aspects of solar cells, photocatalytic degradation of pollutants, sensors, glass antifogging and the like, and become a hot spot of current domestic and foreign research. The current titanium dioxide film preparation methods comprise 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 the embodiment, a TiO2 nano film layer is deposited and grown on the surface of the pixel limiting layer 15, a hydrothermal method is adopted to grow for two hours at 160 ℃, a TiO2 micro-nano composite film with a micro-nano scale is prepared on the surface of the pixel limiting layer 15, the TiO2 micro-nano composite film has a composite structure cluster, the size of the composite structure cluster is 0.1-0.2um, and the composite structure cluster is composed of a TiO2 nano rod array with the size of 10-30 nm. The TiO2 micro-nano composite film has a large number of pores, and the large number of pores can prevent liquid drops from infiltrating, so that the TiO2 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 TiO2 micro-nano composite film is changed into high hydrophilicity. Under a dark state environment (i.e. no light irradiation or trace light irradiation), the TiO2 micro-nano composite film can also become hydrophobic after releasing energy.

In the embodiment, the TiO2 micro-nano composite film is formed by a hydrothermal method, 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 is changed into high hydrophilicity. The TiO2 micro-nano composite film becomes hydrophobic after releasing energy without irradiation or in dark light.

In some embodiments, micro-nano composite films with various morphologies can be prepared by changing the conditions of concentration of the hydrothermal growth solution, ionic additives, growth time and the like, and the micro-nano composite films can comprise a needle tip array, a nanorod array, a hexagonal microdisk and the like formed by oxides.

It should be noted that the oxide in the micro-nano composite film may also be tin dioxide, zinc oxide, etc., and the principle of using the oxide to prepare the micro-nano composite film is the same as that of using titanium dioxide to form the micro-nano composite film, which is not illustrated herein.

In some embodiments, as shown in fig. 7, the organic electroluminescent display substrate further comprises an organic functional layer 17 and a cathode layer 18 of the organic electroluminescent device. The organic functional layer 17 is arranged on the side of the micro-nano composite film 16, which is far away from the substrate 11, and is formed in the opening 151 of the pixel limiting layer 15. The cathode layer 18 of the organic electroluminescent device is arranged on the side of the micro-nano composite film 16, which is far away from the substrate base plate 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, a certain distance is provided between the top of the organic functional layer 17 and the micro-nano composite film 16, and the certain distance is provided to prevent short circuit, and a person skilled in the art can select a suitable distance according to a specific structure, which is not 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 the 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.

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

In a second aspect, embodiments of the present disclosure provide a method for manufacturing an organic electroluminescent display substrate, as shown in fig. 9, the method for manufacturing an organic electroluminescent display substrate includes:

s101, providing a substrate base plate.

The substrate of the substrate is used as a support for an electrode layer and an organic functional film layer in an organic electroluminescent device, has good light transmission performance and certain capability of preventing water vapor and oxygen from permeating in a visible light region, has good surface smoothness, and can be generally made of glass, flexible substrates, array substrates and the like. If a flexible substrate is selected, it may be made of polyester, polyimide, or a relatively thin metal.

And S102, sequentially forming a pixel driving circuit and a planarization layer on the substrate. Forming the pixel driving circuit on the substrate may include, for example: and sequentially forming a grid electrode, a grid insulating layer, an active layer, a source electrode and a drain electrode on the substrate, wherein the drain electrode is connected with the pixel electrode through a through 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.

And S103, forming an anode layer of the organic electroluminescent device on one side of the planarization layer, which is far away from the substrate. The anode is usually made of inorganic metal oxide (such as Indium Tin Oxide (ITO), zinc oxide (ZnO), etc.), organic conductive polymer (such as poly (3, 4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT: PSS, polyaniline PANI, etc.), or high work function metal material (such as gold, copper, silver, platinum, etc.).

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

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

For example, a hydrothermal method is adopted to grow for two hours at 160 ℃, a micro-nano composite film with a micro-nano scale is prepared on the surface of the pixel limiting layer, the micro-nano composite film has composite structure clusters, the size of the composite structure clusters is 0.1-0.2um, and the composite structure clusters are composed of 10-30nm nanorod arrays. The micro-nano composite film has a large number of pores which can prevent the infiltration of liquid drops, so the micro-nano composite film has good hydrophobicity. In addition, after the surface of the composite structure graph cluster is irradiated by ultraviolet light or high-energy light, the composite structure is changed in a 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 in dark light.

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

The functional layers of the organic electroluminescent device are 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 comprises any one of 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-hexaazatriphenylene (HAT-CN), 2,3,5, 6-tetrafluoro-7, 7',8,8' -tetracyanoldimethyl-p-phenylene (F4-TCNQ) and ammonium tris (4-bromophenyl) hexachloroantimonate (TBAHA). The material of the hole transport layer 5 may be made of aromatic diamine compounds, triphenylamine compounds, aromatic triamine compounds, biphenyldiamine derivatives, triarylamine polymers, metal complexes, or carbazole polymers, and preferably: any one of N, N '-di (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 organic material which is undoped fluorescent light-emitting composed of a light-emitting material having a hole transport ability not lower than an electron transport ability, or made of an organic material which is doped with a fluorescent material composed of a fluorescent dopant and a host material, or made of an organic material which is doped with a phosphorescent 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-phenyl oxadiazole (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.

Alternatively, the forming of the functional layer (S106) of the organic electroluminescent device in the opening portion may specifically include:

s1061, before ink is dripped into the opening part, shielding the micro-nano composite film covering the flat part, and irradiating the micro-nano composite film by using ultraviolet light to change the hydrophobicity of the micro-nano composite film covering the opening part into hydrophilicity;

s1062, dropping a certain amount of ink into the opening part of the pixel limiting layer;

and S1063, in the ink drying process, placing the display substrate in a dark state environment to change the hydrophilicity of the micro-nano composite film covering the opening part into hydrophobicity.

And 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 is usually made of a low work function metal 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, and the like) and the above metal or alloy.

It is to be understood that the above embodiments are merely exemplary embodiments that are employed to illustrate the principles of the present disclosure, and that the present disclosure is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the disclosure, and these are to be considered as the scope of the disclosure.

Claims

1. An organic electroluminescence display substrate, comprising a pixel defining layer provided on a base 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, and the micro-nano composite film covers the flat part and the opening part of the pixel limiting layer;

the micro-nano composite film covering the flat part is changed 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.

2. The organic electroluminescent display substrate according to claim 1, wherein the micro-nano composite film comprises at least one of a nanorod array structure, a pinpoint array structure and a hexagonal array structure formed of an oxide.

3. The organic electroluminescent display substrate according to claim 2, wherein the oxide comprises at least one of zinc oxide, titanium oxide, and tin oxide.

4. The organic electroluminescent display substrate according to claim 3, wherein conductive particles are disposed in the micro-nano composite film covering the flat portion.

5. A method for preparing an organic electroluminescent display substrate is characterized by comprising the following steps:

providing a substrate base plate;

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

6. The method for manufacturing an organic electroluminescent display substrate according to claim 5, wherein a micro-nano composite film is formed on the flat portion and the opening portion, and specifically comprises:

7. The method of manufacturing an organic electroluminescent display substrate according to claim 6, further comprising, after the step of forming a micro-nano composite film on the flat portion and the opening portion:

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

8. The method of manufacturing an organic electroluminescent display substrate according to claim 7, wherein forming an organic electroluminescent device functional layer in the opening portion specifically includes:

dropping a predetermined amount of ink into the opening;

9. The method of manufacturing an organic electroluminescent display substrate according to claim 8, further comprising, after forming an organic electroluminescent device functional layer in the opening portion:

10. A display device comprising the display substrate according to any one of claims 1 to 4.