Pixel defining layer structure, method and equipment for improving film forming uniformity of ink-jet printing OLED (Organic Light Emitting Diode)

Abstract

According to the pixel defining layer structure, method and device for improving the film forming uniformity of the ink-jet printing OLED, the material distribution and surface characteristics of PDL are optimized, and the film forming uniformity in the ink droplet evaporation process is remarkably improved. The structure adopts combined distribution of hydrophilic and hydrophobic materials, and the hydrophilic material covers 65% of the area of the bottom of the pixel defining layer to promote uniform spreading of ink droplets; the hydrophobic material covers 35% of the area of the top, limiting the diffusion of the ink droplets. The contact angle between the ink droplet and the hydrophilic material is adjusted to be 55-72 degrees, the contact angle between the ink droplet and the hydrophobic material is adjusted to be 100-120 degrees, the PDL inclination angle is optimized to be 60-61 degrees, the evaporation rate distribution of the ink droplet is further balanced, and the coffee ring effect is reduced. According to the structure, when ink droplets are evaporated, the film forming uniformity is optimal, the luminous efficiency of an OLED device is effectively improved, the service life of the OLED device is effectively prolonged, and the OLED device has a remarkable industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electroluminescent device (OLED) manufacturing, and relates to a pixel definition layer structure, method and equipment for improving the uniformity of inkjet printed OLED film formation. Background Art

[0002] Organic electroluminescent devices (OLEDs) are widely used in display, lighting, healthcare, and other fields due to their advantages such as fast response speed, wide field of view, and high flexibility. To meet the growing market demand, OLED manufacturing technology continues to be updated and iterated. Compared with traditional vacuum evaporation technology, inkjet printing technology has gradually become one of the advanced preparation technologies for OLED devices due to its high cost-effectiveness, fast printing speed, and simple process. The preparation of OLED devices using inkjet printing technology involves multiple physical processes, including the formation of ink droplets, the spread of ink droplets when they fly and hit the substrate, and the evaporation and drying of ink droplets. Among them, ink droplet evaporation, as a key process in the preparation process, directly determines the uniformity of the organic layer film, thereby affecting the luminescence level and lifespan of the device.

[0003] In the manufacturing process of inkjet-printed OLED devices, the uniformity of ink droplet evaporation and film formation is a key factor affecting device performance. Traditional pixel-defining layer structures typically use a single hydrophilic or hydrophobic material, but these structures have significant limitations. A single hydrophilic pixel-defining layer can cause ink droplets to climb or remain during spreading, while a single hydrophobic pixel-defining layer can result in excessive surface curvature, leading to uneven evaporation rates and a "coffee ring" effect, which seriously affects film quality. Summary of the Invention

[0004] To address the challenges of existing technologies, the present invention provides a pixel-defining layer structure that improves the uniformity of inkjet-printed OLED film formation. By distributing hydrophilic and hydrophobic materials in different regions of the pixel-defining layer, the structure optimizes the spreading and evaporation behavior of ink droplets, reduces the triple-point evaporation rate, and significantly improves film uniformity. This structure not only improves the dynamic characteristics of ink droplet evaporation but also increases the luminous efficiency and service life of OLED devices, possessing significant industrial application value.

[0005] The present invention is achieved through the following technical solutions: A pixel definition layer combination structure for improving the uniformity of ink droplet evaporation film formation in OLED pixel holes includes a heating substrate at the bottom and pixel definition layers arranged around it. The pixel definition layers are composed of a combination of hydrophobic and hydrophilic materials to form a layered or partitioned composite structure.

[0006] Preferably, the hydrophilic material is primarily distributed at the bottom of the pixel-defining layer, forming a stable base that promotes uniform spreading of ink droplets within the layer. The hydrophobic material is distributed at the top of the pixel-defining layer, forming a confining layer that prevents ink droplets from excessively spreading or climbing onto the sidewalls of the pixel-defining layer during evaporation. This distribution pattern creates a stable flow and evaporation pattern during ink droplet evaporation, while also preventing uneven ink droplet residue on the surface of the pixel-defining layer.

[0007] Preferably, the hydrophobic material covers 35% of the entire area of ​​the pixel defining layer, while the hydrophilic material covers the remaining 65% of the area. This distribution ratio can balance the spreading and evaporation characteristics of the ink droplets.

[0008] Preferably, a lower contact angle makes it easier for the ink droplets to spread on the bottom of the pixel defining layer, forming a flatter shape and reducing the "coffee ring" effect, while a higher contact angle limits the diffusion of the ink droplets on the top of the pixel defining layer, preventing the ink droplets from forming an uneven film during evaporation.

[0009] Preferably, by adjusting the surface energies of the hydrophilic and hydrophobic materials, the ink droplet's contact angle with the hydrophilic material is approximately 55° to 72°, and the contact angle with the hydrophobic material is approximately 100° to 120°. This contact angle combination can effectively reduce the relative evaporation rate of the ink droplet's triple point, thereby improving film uniformity.

[0010] Preferably, the hydrophilicity and hydrophobicity of the material surface are adjusted by plasma treatment or chemical modification to achieve the desired contact angle.

[0011] Preferably, by adjusting the tilt angle of the pixel defining layer, the evaporation path and flow pattern of the ink droplets can be further optimized. When the tilt angle is 60-61 degrees, the evaporation rate distribution of the ink droplets during the evaporation process is more uniform, thereby further improving the uniformity of film formation.

[0012] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention utilizes a combination of hydrophilic and hydrophobic materials. The areas covered by the hydrophilic material can guide the ink droplets to spread evenly, while the areas covered by the hydrophobic material limit the excessive diffusion of the ink droplets. Under these combined effects, the ink droplets form a more uniform flow pattern during the evaporation process, effectively reducing the "coffee ring" effect and making the film thickness after the ink droplets evaporate more uniform.

[0013] The structure of this invention optimizes the evaporation path of ink droplets. A hydrophilic material is distributed at the bottom of the pixel-defining layer, providing a stable base for the ink droplets to spread; a hydrophobic material is distributed at the top, preventing the ink droplets from diffusing toward the sidewalls of the pixel-defining layer during evaporation. This layered design ensures that ink droplets evaporate evenly along a predetermined path during evaporation, avoiding variations in film thickness caused by uneven droplet diffusion. Compared to traditional pixel-defining layer structures with a single property, film uniformity is significantly improved.

[0014] The structure of the present invention can be implemented on existing inkjet printing equipment, eliminating the need for extensive equipment modifications. The coating and surface treatment processes for the hydrophilic and hydrophobic materials are relatively simple, allowing for easy integration into existing production processes. This not only reduces production costs but also minimizes production interruptions associated with equipment modifications, thereby improving production efficiency.

[0015] By optimizing the tilt angle of the pixel-defining layer, the present invention can further control the evaporation behavior of ink droplets. Adjusting the tilt angle can alter the flow path and evaporation rate distribution of ink droplets within the pixel-defining layer. Compared to traditional fixed pixel-defining layers, this dynamic control capability allows for more uniform solute distribution during evaporation, further improving film uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of the pixel definition layer assembly structure of this embodiment; Figure 2 The variation of the evaporation rate of the highest point of the ink droplet over time in this embodiment and the comparative example; Figure 3 The variation of the triple point evaporation rate of the ink droplet over time in this embodiment and the comparative example; Figure 4 The variation law of the relative evaporation rate of the triple point of the ink droplet in this embodiment and the comparative example; Figure 5 is the height difference between the highest point of the ink droplet and the triple point in this embodiment and the comparative example; Figure 6 is the height difference between the highest point of the ink droplet and the triple point in this embodiment and another comparative example.

[0018] In the figure, 1. heating substrate, 2. pixel defining layer, 3. ink droplet, 4. first contact angle, 5. second contact angle, 6. tilt angle of pixel defining layer, 201. hydrophobic material, 202. hydrophilic material. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] like Figure 1 The embodiment of the present invention provides a pixel definition layer composite structure for improving the uniformity of ink droplet evaporation film formation in OLED pixel holes. The structure comprises a heating substrate 1 at the bottom and pixel definition layers 2 arranged around the periphery. The pixel definition layers 2 are composed of a hydrophobic material 201 and a hydrophilic material 202, forming a composite structure with upper and lower layers or zones. The hydrophobic material layer is made of a hydrophobic polymer such as polytetrafluoroethylene, while the hydrophilic material layer is made of a hydrophilic polymer such as polyvinyl alcohol.

[0022] The hydrophilic material 202 of the pixel-defining layer 2 is primarily distributed at the bottom, forming a stable base that promotes uniform spreading of ink droplets 3 within the pixel-defining layer 2. The hydrophobic material 201 is distributed at the top of the pixel-defining layer 2, forming a confining layer that prevents ink droplets from excessively spreading or climbing onto the sidewalls of the pixel-defining layer during evaporation. This distribution pattern creates a stable flow and evaporation pattern during ink droplet evaporation, while also preventing uneven ink droplet residue on the surface of the pixel-defining layer.

[0023] The hydrophilic material 202 covers 65% of the entire area of ​​the pixel defining layer 2 , and the hydrophobic material 201 covers the remaining 35%. This distribution ratio can balance the spreading and evaporation characteristics of the ink droplets.

[0024] The first contact angle 4 between the hydrophobic material 201 and the ink droplet 3 is 100°~120°, and the first contact angle 4 is the contact angle between the ink droplet and the hydrophobic material. The second contact angle 5 between the hydrophilic material 202 and the ink droplet 3 is 55°~72°, and the second contact angle 5 is the contact angle between the ink droplet and the hydrophilic material. This contact angle combination can effectively reduce the relative evaporation rate of the triple point of the ink droplet, thereby improving the uniformity of film formation.

[0025] The surface energies of the hydrophilic material and the hydrophobic material are adjusted so that the contact angle between the ink droplet and the hydrophilic material is about 55° to 72°, and the contact angle between the ink droplet and the hydrophobic material is about 100° to 120°, wherein the surface energy range of the hydrophobic material (201) is 20-30 mN / m, and the surface energy range of the hydrophilic material (202) is 40-50 mN / m. For example, a plasma treatment or chemical modification method can be used to modify the surface hydrophilicity of the hydrophilic material layer so that the contact angle between the ink droplet and the hydrophobic material layer is about 60° to 68°; and a surface hydrophobicity modification can be used to modify the surface hydrophobicity of the hydrophobic material layer so that the contact angle between the ink droplet and the hydrophobic material layer is about 100° to 120°. The hydrophobic material can also include an alkoxy compound to increase the adhesion between the hydrophobic pixel defining layer and the hydrophilic pixel defining layer.

[0026] By adjusting the tilt angle 6 between the pixel defining layer 2 and the heated substrate 1, the migration rate of the ink droplet's three-phase contact line can be controlled, further optimizing the ink droplet's evaporation path and flow pattern. Specifically, by adjusting the pixel defining layer's fabrication process parameters, such as the sputtering angle and spin coating rate, the tilt angle between the pixel defining layer and the heated substrate can be controlled within a range of 60° to 61°. When the tilt angle 6 is between 60° and 61°, the ink droplet's evaporation rate is more evenly distributed during the evaporation process, further improving film uniformity.

[0027] The evaporation process of the ink droplet (3) includes three stages: Initial stage: ink droplets spread rapidly on the surface of the hydrophilic material (202) to form a basic liquid film; Intermediate stage: the hydrophobic material (201) area limits the retraction of the liquid film through the contact angle hysteresis effect; Final stage: The tilt angle (6) guides the remaining solvent to evaporate along a predetermined path, avoiding local supersaturated crystallization.

[0028] The OLED light-emitting layer is produced on the pixel definition layer using an inkjet printing process. Specifically, an organic light-emitting material ink with appropriate viscosity and surface tension is used, and the ink is precisely sprayed into the opening area of ​​the pixel definition layer using an inkjet printer. The ink is then cured at high temperature to form the light-emitting layer of the OLED device. Comparative Examples and Examples Figure 2 The numerical simulation results of the variation of the evaporation rate of the highest point of the ink droplet with time when the pixel definition layer is arranged as a single hydrophilicity, a single hydrophobicity, and a combination of them. Figure 3 The numerical simulation results of the time-varying law of the evaporation rate of the triple point of ink droplets when the pixel boundary layer is arranged as a single hydrophilicity, a single hydrophobicity, and a combination of them are presented. Figure 4 The numerical simulation results of the temporal variation of the relative evaporation rate of the triple point of ink droplets (the difference between the evaporation rate of the triple point and the evaporation rate of the highest point) when the pixel definition layer is arranged as a single hydrophilicity, a single hydrophobicity, and a combination of these. Figure 5 These are the numerical simulation results of the height difference between the highest point of the ink droplet and the triple point at 2000ms when the pixel definition layer is arranged as a single hydrophilicity, a single hydrophobicity, and a combination. Figure 6 These are the numerical simulation results of the height difference between the highest point of the ink droplet and the triple point at 2000ms under five different combinations of pixel definition layers.

[0029] Depend on Figure 2 It can be seen that when t = 200~800ms, the evaporation rate of the highest point of the ink droplet when the pixel definition layer is arranged in combination is basically the same as when the pixel definition layer is arranged as a single hydrophobic material, while the evaporation rate of the highest point of the ink droplet when the pixel definition layer is arranged as a single hydrophilic material is the highest. t = 800~1200ms, due to the contact angle between ink droplet and PDL θ Changes occur, and the evaporation rate of the highest point of the ink droplet when the pixel definition layer is arranged in combination increases rapidly.

[0030] Depend on Figure 3 It can be seen that as the evaporation proceeds, when the pixel definition layer is arranged, the surface characteristics of the pixel definition layer change. t = 1000 ~ 1200ms, the evaporation rate of the triple point of the ink droplet increases rapidly. At this time, the evaporation rate of the triple point of the ink droplet arranged in a single pixel definition layer still increases uniformly. When the flow inside the ink droplet stabilizes, t = 1200~2000ms, the evaporation rate of the ink droplet triple point increases evenly under the single hydrophilic material arrangement and the combined arrangement of the pixel definition layer, but the evaporation rate of the ink droplet triple point increases faster when the pixel definition layer is arranged in combination, indicating that the change of the PDL surface properties has an important influence on the evaporation rate of the ink droplet triple point.

[0031] Depend on Figure 4 It can be seen that when the pixel definition layer adopts a single hydrophilic material, the relative evaporation rate of the ink droplet triple point increases uniformly; when the pixel definition layer adopts a single hydrophobic material, t = 1600~1800ms, then decreases t =1800~2000ms rises rapidly; when the pixel definition layer is combined and arranged, t = 800 ~ 1200ms, the relative evaporation rate of the ink droplet first decreases rapidly and then increases rapidly, indicating that the transition of the PDL material properties from hydrophobic to hydrophilic leads to a sudden change in the evaporation rate of the ink droplet's highest point and triple point. This is because when the PDL material properties change, the evaporation rate of the ink droplet's triple point located on the PDL will first decrease rapidly. However, the ink droplet's highest point is far away from the PDL. After the evaporation rate of the ink droplet's triple point is relatively stable, the evaporation rate of the ink droplet's highest point begins to decrease rapidly. Overall, during the evaporation process, when the pixel definition layer combination is arranged, the average relative evaporation rate of the ink droplet's triple point is lower, indicating that the combination of hydrophilic and hydrophobic materials has a positive impact on the uniformity of ink droplet evaporation film formation compared to the other two arrangements.

[0032] Depend on Figure 5 It can be seen that when the pixel defining layer is arranged with a single hydrophobic material, the height difference between the triple point and the highest point of the ink droplet is the largest. The main reason is that before the ink droplet evaporates, the surface curvature of the ink droplet is large. In addition, due to the rapid evaporation rate of the ink droplet triple point, the height difference between the triple point and the highest point of the ink droplet is large at 2000ms. When the pixel defining layer is arranged in combination, the height difference between the triple point and the highest point of the ink droplet is the smallest. It is worth noting that when the pixel defining layer is arranged with a single hydrophilic material, the height difference between the triple point and the highest point of the ink droplet is also small. This may be because a small amount of hydrophobic material is arranged in the upper half of the PDL during the combination arrangement, resulting in a larger surface curvature of the ink droplet before evaporation begins. In order to minimize the height difference between the highest point and the triple point of the ink droplet and improve the uniformity of ink droplet film formation, further research on more reasonable combination arrangement schemes is needed.

[0033] Depend on Figure 6 It can be seen that when the ink droplet contacts the hydrophilic θ = 55°, the height difference between the highest point of the ink droplet and the triple point is 0.27μm. At this time, the height difference between the triple point of the ink droplet and the highest point is relatively small. When the ink droplet and the hydrophilic contact angle θ = 50°, the height difference between the highest point of the ink droplet and the triple point becomes negative, indicating that the height of the triple point of the ink droplet is higher than the height of the highest point of the ink droplet. This situation will still have an adverse effect on the uniformity of the ink droplet evaporation film. Therefore, when the combined arrangement is adopted, the contact angle between the ink droplet and the hydrophilic θ When the angle is about 55°, the uniformity of ink droplet evaporation and film formation is optimal.

[0034] An OLED inkjet printing device, comprising the pixel definition layer combination structure as described above; A material distribution control system is used to form a composite structure of the hydrophobic material (201) and the hydrophilic material (202) on the surface of the pixel definition layer (2); comprising a micro-jet printing device for depositing the hydrophilic material (202) in the bottom area of ​​the pixel definition layer (2); a laser direct writing device for etching the hydrophobic material (201) in the top area of ​​the pixel definition layer (2); and a mask alignment system for ensuring that the boundary accuracy between the hydrophobic area (201) and the hydrophilic area (202) is ≤2μm.

[0035] A tilt angle control module for precisely controlling the tilt angle (6) between the pixel defining layer (2) and the heating substrate (1) within a range of 60° to 61°; Surface treatment unit, integrating plasma treatment unit and chemical modification unit, used to adjust the surface energy parameters of materials; The flow monitoring module, which includes a high-speed camera and contact angle meter, monitors the ink droplet contact angle and film thickness distribution in real time. Using a spectral confocal microscope, the module provides the following functions: real-time acquisition of contact angle data, dynamic feedback adjustment of surface treatment parameters; establishment of a mathematical model of film thickness versus evaporation time to predict film uniformity; and automatic triggering of an angle adjustment mechanism for compensation when the thickness standard deviation exceeds 5%.

[0036] The feedback control system connects the flow monitoring module and the tilt angle control module to form a closed-loop regulation mechanism.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. When a component is referred to as being "fixed to" another component, it can be directly on the other component or there can also be an intermediate component. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there can be an intermediate component at the same time. When a component is considered to be "set on" another component, it can be directly set on the other component or there can be an intermediate component at the same time.

[0040] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0041] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A pixel definition layer structure for improving the uniformity of inkjet printed OLED film formation, characterized in that: It comprises a heating substrate (1) located at the bottom and a pixel definition layer (2) arranged around it; The pixel defining layer (2) is formed of a hydrophobic material (201) and a hydrophilic material (202) arranged in layers or zones to form a composite structure; the hydrophilic material (202) is distributed in the bottom area of ​​the pixel defining layer (2), and the hydrophobic material (201) is distributed in the top area of ​​the pixel defining layer (2).

2. The pixel definition layer structure for improving the uniformity of inkjet printed OLED film formation according to claim 1, characterized in that: The hydrophilic material (202) covers 65% of the entire area of ​​the pixel definition layer (2), and the hydrophobic material (201) covers the remaining 35% of the area of ​​the pixel definition layer (2).

3. The pixel definition layer structure for improving the uniformity of inkjet printed OLED film formation according to claim 1, characterized in that: The first contact angle (4) between the hydrophobic material (201) and the ink droplet (3) is 100° to 120°, and the second contact angle (5) between the hydrophilic material (202) and the ink droplet (3) is 55° to 72°.

4. The pixel definition layer structure for improving the uniformity of inkjet printed OLED film formation according to claim 3, characterized in that: The surface energies of the hydrophilic material (202) and the hydrophobic material (201) are adjusted by plasma treatment or chemical modification, so that the contact angle (5) between the ink droplet (3) and the hydrophilic material (202) reaches 55° to 72°; and the contact angle (4) between the ink droplet (3) and the hydrophobic material (201) reaches 100° to 120°.

5. The pixel definition layer structure for improving the uniformity of inkjet printed OLED film formation according to claim 1, characterized in that: The tilt angle (6) between the pixel defining layer (2) and the heating substrate (1) is 60° to 61°.

6. The pixel definition layer structure for improving the uniformity of inkjet printed OLED film formation according to claim 1, characterized in that: The hydrophobic material layer is made of polytetrafluoroethylene; the hydrophilic material layer is made of polyvinyl alcohol.

7. A method for improving the uniformity of inkjet printed OLED film formation, characterized in that: The pixel defining layer combination structure according to any one of claims 1 to 6 is adopted, and by regulating the interfacial energy gradient distribution between the hydrophilic material (202) and the hydrophobic material (201) of the pixel defining layer (2), the ink droplets (3) are guided to form a radial flow pattern during the evaporation process.

8. The method for improving the uniformity of inkjet printed OLED film formation according to claim 7, characterized in that: By adjusting the tilt angle (6) between the pixel defining layer (2) and the heating substrate (1) to 60°-61°, the migration rate of the three-phase contact line of the ink droplet (3) is controlled.

9. An OLED inkjet printing device for improving the uniformity of inkjet printed OLED film formation according to any one of claims 1 to 6, characterized in that: The device comprises a device for controlling the material distribution and surface characteristics of the pixel defining layer (2), and a device for adjusting the tilt angle (6) of the pixel defining layer (2).

10. The OLED inkjet printing device according to claim 9, characterized in that: The device further comprises a control unit for implementing the method according to any one of claims 7 to 8.

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