CN109904340B

CN109904340B - OLED display panel and preparation method thereof

Info

Publication number: CN109904340B
Application number: CN201910085679.1A
Authority: CN
Inventors: 夏晨
Original assignee: Wuhan China Star Optoelectronics Semiconductor Display Technology Co Ltd
Current assignee: Wuhan China Star Optoelectronics Semiconductor Display Technology Co Ltd
Priority date: 2019-01-29
Filing date: 2019-01-29
Publication date: 2021-02-02
Anticipated expiration: 2039-01-29
Also published as: CN109904340A

Abstract

The invention relates to an OLED display panel and a preparation method thereof. The OLED display panel comprises a substrate, a TFT driving layer, an OLED light emitting layer, a first inorganic packaging layer, an organic packaging layer, a buffer layer, a metal layer, a flat layer and a second inorganic packaging layer. According to the invention, the buffer layer and the metal layer are added on the organic packaging layer, so that exciton attenuation in the emission layer can be reduced, and the extraction of incident light is enhanced, thereby enhancing light emission and improving external quantum efficiency.

Description

OLED display panel and preparation method thereof

Technical Field

The invention relates to the technical field of display, in particular to an OLED display panel and a preparation method thereof.

Background

An Organic Light-Emitting Diode (OLED) display device is also called an Organic electroluminescent display device or an Organic Light-Emitting semiconductor. The basic structure of OLED is a sandwich structure composed of a thin and transparent Indium Tin Oxide (ITO) with semiconductor property connected to the positive electrode of power, and another metal cathode. The whole structure layer comprises a Hole Transport Layer (HTL), a light Emitting Layer (EL) and an Electron Transport Layer (ETL). When power is supplied to a proper voltage, positive holes and surface cathode charges are combined in the light-emitting layer and are recombined to form excitons (electron-hole pairs) in an excited state at a certain probability under the action of coulomb force, the excited state is unstable in a normal environment, the excitons in the excited state are recombined and transfer energy to the light-emitting material, so that the light-emitting material is transited from a ground state energy level to the excited state, the excited state energy generates photons through a radiation relaxation process, light energy is released, brightness is generated, and three primary colors of red, green and blue are generated according to different formulas to form basic colors.

First, the OLED is characterized by self-luminescence, unlike a TFT-LCD (Thin film transistor-liquid crystal display) device, which requires a backlight, and thus has high visibility and brightness. Secondly, the OLED has the advantages of low voltage requirement, high power saving efficiency, fast response, light weight, thin thickness, simple structure, low cost, wide viewing angle, almost infinite contrast, low power consumption, extremely high response speed, etc., has become one of the most important display technologies at present, is gradually replacing the TFT-LCD, and is expected to become the next generation of mainstream display technology following the LCD.

Quantum efficiency is an important parameter describing the photoelectric conversion capability of a photoelectric device, and is the ratio of the average number of generated photons to the number of incident photons per unit time at a specific wavelength. In the injection type semiconductor laser tube, the ratio of the number of photons generated at the PN junction region per unit time to the number of injected electron-hole pairs. Injecting carriers into the diode, wherein one part of the carriers are recombined through an electron-hole pair, and the other part of the carriers flow away through a tunnel effect and other forms of junction regions; some of the carriers that recombine emit energy in the form of light, and another part of the carriers may convert the emitted energy into thermal energy of lattice vibration or other forms of energy. Such recombination is called non-radiative recombination. Internal quantum efficiency is a quantitative relationship that describes how well the luminescence recombination is in proportion to this entire physical process. However, the number of generated photons cannot be totally emitted outside the device, because of losses such as absorption scattering and diffraction in the outer PN junction. External Quantum Efficiency (EQE) is the ratio between the number of photons emitted by an electroluminescent device and the number of electrons injected into the device in the observation direction, and is the most important index for evaluating the performance of the device. EQE ═ γ χ η PL η OC, where γ is the ratio of injected electrons to holes undergoing recombination; chi refers to the proportion of radiative transition generated after exciton recombination; η PL refers to the fluorescence quantum yield of the luminescent material; η OC is the light extraction rate of the emitted photons. The effects of the above four coefficients on EQE are equivalent.

At present, the development of phosphorescence and thermally activated delayed fluorescence materials in the light emitting layer makes the internal quantum efficiency reach 100% theoretically, but the external quantum efficiency of the OLED is still limited by waveguides, substrates, surface plasmons, etc., and the external quantum efficiency is lost to a large extent. The electroluminescent device is generally formed by laminating different materials, and when light enters from the high-refractive-index layer to the low-refractive-index layer, the device is internally provided with a parallel layer structure, so that most incident light is lost due to total reflection, and the light-emitting rate of the device is greatly reduced. There is a need for a new OLED display panel to improve the external quantum efficiency of OLED devices.

Disclosure of Invention

An object of the present invention is to provide an OLED display panel and a method for manufacturing the same, which can solve the problem of low external quantum efficiency of the current OLED display panel.

In order to solve the above problems, an embodiment of the present invention provides an OLED display panel including, in order: the organic light emitting diode comprises a substrate, a TFT driving layer, an OLED light emitting layer, a first inorganic packaging layer, an organic packaging layer, a buffer layer, a metal layer, a flat layer and a second inorganic packaging layer. Wherein the TFT drive layer is disposed on the substrate; the OLED light emitting layer is arranged on the TFT driving layer; the first inorganic packaging layer is arranged on the OLED light-emitting layer; the organic encapsulation layer is arranged on the first inorganic encapsulation layer; the buffer layer is arranged on the organic packaging layer; the metal layer is arranged on the buffer layer; the flat layer is coated on the metal layer; the second inorganic encapsulation layer is disposed on the planarization layer.

Further, the metal layer is formed by adopting a nanoparticle structure through the forming material of the metal layer.

Further, the metal layer adopts a nano-particle structure with the particle size ranging from 50nm to 150 nm.

Further, the metal layer is made of metal silver.

Further wherein the metallic silver has a thickness in the range of 10-12 nm.

Further, the buffer layer is made of polyethylene dioxythiophene-polystyrene sulfonic acid.

Further, the material of the flat layer is SU-8 photoresist.

Further wherein the buffer layer has a thickness in the range of 1-1.5 μm and the planarization layer has a thickness in the range of 1-1.5 μm.

Another embodiment of the present invention also provides a method for manufacturing the OLED display panel, including the steps of:

s1, providing a substrate, and sequentially preparing a TFT driving layer and an OLED light emitting layer on the substrate;

s2, preparing a first inorganic packaging layer on the OLED light-emitting layer;

s3, preparing an organic encapsulation layer on the first inorganic encapsulation layer;

s4, preparing a buffer layer on the organic packaging layer;

s5, preparing a metal layer on the buffer layer;

s6, preparing a flat layer on the metal layer;

and S7, preparing a second inorganic packaging layer on the flat layer.

Further, step S5 includes preparing a layer of metal on the buffer layer, and then performing low-temperature annealing on the prepared metal, where the annealed metal becomes a metal layer formed by using a nanoparticle structure through a material of the buffer layer under the energy modification effect of the surface of the buffer layer material.

The invention has the advantages that: the invention relates to an OLED display panel and a preparation method thereof.A buffer layer and a metal layer are sequentially prepared on an organic packaging layer, and the obtained structure is subjected to low-temperature annealing treatment, so that the metal layer is formed by adopting a nano-particle structure through the forming material of the metal layer; the metal nano-particle subjected to annealing treatment has a larger particle size, the lower the absorption rate of the metal nano-particle to light is, the better the scattering efficiency is, and due to the local surface plasma resonance and light scattering performance of the metal nano-particle scattering layer, the exciton attenuation in the emitting layer can be reduced, and the extraction of incident light is enhanced, so that the light emitting is enhanced, and the external quantum efficiency is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of an OLED display panel according to the present invention.

FIG. 2 is a process diagram of the OLED display panel of the present invention.

The components in the figure are identified as follows:

1. substrate 2, TFT drive layer

3. OLED light-emitting layer 4, first inorganic encapsulation layer

5. Organic encapsulation layer 6, buffer layer

7. Metal layer 8, planarization layer

9. Second inorganic encapsulation layer

Detailed Description

The following detailed description of the preferred embodiments of the present invention is provided to enable those skilled in the art to make and use the present invention in a complete manner, and is provided for illustration of the technical disclosure of the present invention so that the technical disclosure of the present invention will be more clearly understood and appreciated by those skilled in the art how to implement the present invention. The present invention may, however, be embodied in many different forms of embodiment, and the scope of the present invention should not be construed as limited to the embodiment set forth herein, but rather construed as being limited only by the following description of the embodiment.

The directional terms used in the present invention, such as "up", "down", "front", "back", "left", "right", "inner", "outer", "side", etc., are only directions in the drawings, and are used for explaining and explaining the present invention, but not for limiting the scope of the present invention.

In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. In addition, the size and thickness of each component shown in the drawings are arbitrarily illustrated for convenience of understanding and description, and the present invention is not limited to the size and thickness of each component.

When certain components are described as being "on" another component, the component can be directly on the other component; there may also be an intermediate component disposed on the intermediate component and the intermediate component disposed on another component. When an element is referred to as being "mounted to" or "connected to" another element, they are directly "mounted to" or "connected to" the other element or "mounted to" or "connected to" the other element through an intermediate element.

Example 1

As shown in fig. 1, the OLED display panel of the present embodiment includes, in order: the organic light emitting diode comprises a substrate 1, a TFT driving layer 2, an OLED light emitting layer 3, a first inorganic packaging layer 4, an organic packaging layer 5, a buffer layer 6, a metal layer 7, a flat layer 8 and a second inorganic packaging layer 9.

The OLED light-emitting layer 3 is arranged on the TFT driving layer 2, and OLED refers to a phenomenon that the organic semiconductor material and the light-emitting material emit light under the driving of an electric field through carrier injection and recombination. The principle is that an ITO transparent electrode and a metal electrode are respectively used as an anode and a cathode of the device, under the drive of a certain voltage, electrons and holes are respectively injected into an electron transport layer and a hole transport layer from the cathode and the anode, the electrons and the holes respectively migrate to a luminescent layer through the electron transport layer and the hole transport layer and meet in the luminescent layer to form excitons and excite luminescent molecules, and the latter emits visible light through radiation relaxation.

The first inorganic encapsulation layer 4 is disposed on the OLED light-emitting layer 3, and may be formed by a chemical vapor deposition method. Vapor Deposition (CVD) is a process of forming functional or decorative metal, non-metal or compound coating on the surface of a workpiece by physical and Chemical processes occurring in the Vapor phase. The chemical vapor deposition is one of them. Chemical vapor deposition is a chemical technology, which is a method for generating a film by performing a chemical reaction on the surface of a substrate by using one or more gas-phase compounds or simple substances containing film elements. The thickness of the first inorganic encapsulation layer 4 is in the range of 0.5-1 μm, and the material of the first inorganic encapsulation layer 4 may be SiNx (silicon nitride) or SiOx (silicon oxide). The prepared film not only can play a role in antireflection, but also has the functions of surface passivation and body passivation, and can well achieve the packaging effect.

The organic packaging layer 5 is arranged on the first inorganic packaging layer 4, and can be prepared and formed in an ink-jet printing mode, wherein the ink-jet printing technology adopts the working principle that firstly, a silk screen photosensitive adhesive is coated on a silk screen and dried, light-blocking ink is sprayed and printed on a photosensitive layer through a spraying quantity system, after the ink is dried, the ultraviolet rays are used for carrying out overall exposure on the silk screen, at the moment, the part which is not sprayed with the ink is hardened by the light, and the part sprayed with the ink can be washed away; the developing solution is usually water, i.e. the part sprayed with ink is washed away by water to form the image-text part of the screen. The thickness of the organic encapsulation layer 5 is in the range of 3-8 μm, and the material of the organic encapsulation layer 5 can be selected from PMMA (polymethyl methacrylate).

The buffer layer 6 is disposed on the organic encapsulation layer 5, and may be formed by coating. The coating modes include smooth roll gluing coating, anilox roll gluing coating and hot melt adhesive spray extrusion coating. Smooth roll size coating typically employs two roll transfer coating. The size of the coating amount can be adjusted by adjusting the gap between the upper rubber roll and the coating roll; the anilox roller is mainly coated by an anilox (concave hole) coating roller; the hot melt adhesive spraying and extruding coating is mainly characterized in that after solid glue is heated and melted, the glue is directly sprayed on a substrate through a coating die head by hydraulic loading. Wherein the thickness of the buffer layer 6 is in the range of 1-1.5 μm, and the buffer layer 6 can be made of polyethylenedioxythiophene-polystyrenesulfonic acid due to its strong feasibility. Therefore, the sulfur-containing group of the polyethylene dioxythiophene-polystyrene sulfonic acid can form a complex bond with metal atoms, so that the function of fixing metal nanoparticles is achieved, and the nucleation and growth of the metal nanoparticles are facilitated.

The metal layer 7 is disposed on the buffer layer 6, and the metal layer 7 is formed by using a nanoparticle structure as a constituent material, preferably, the metal layer 7 is made of metallic silver. Since the light scattering effect is the strongest when the particle size range of the nanoparticle structure used for the metal layer 7 is within 50 to 150nm, the particle size range of the nanoparticle structure used for the metal layer 7 is preferably 50 to 150 nm. Specifically, a layer of metal is prepared on the buffer layer 6 in an evaporation mode, then the prepared metal is subjected to low-temperature annealing treatment at 150 ℃ for 10 minutes, and metal nanoparticles subjected to annealing treatment become larger and larger under the surface energy modification effect of polyethylene dioxythiophene-polystyrene sulfonic acid of the buffer layer 6, wherein the particle size of the metal nanoparticles reaches 50nm-150nm, so that the metal is changed into the metal layer 7 which is formed by adopting a nanoparticle structure through the forming material of the metal. Due to the local surface plasma resonance and light scattering performance of the metal layer 7, exciton attenuation in the emitting layer can be reduced, and extraction of incident light is enhanced, so that light emission is enhanced, and external quantum efficiency is improved.

The flat layer 8 covers the metal layer 7, and may be formed by coating. Wherein the thickness of the planarization layer is in the range of 1-1.5 μm, which can better cover the metal layer 7. The material of the flat layer is SU-8 photoresist, and the flatness of the flat layer 8 formed by the method is good.

The second inorganic encapsulation layer 9 is disposed on the planarization layer 8, and may be formed by a chemical vapor deposition method. Vapor Deposition (CVD) is a process of forming functional or decorative metal, non-metal or compound coating on the surface of a workpiece by physical and Chemical processes occurring in the Vapor phase. The chemical vapor deposition is one of them. Chemical vapor deposition is a chemical technology, which is a method for generating a film by performing a chemical reaction on the surface of a substrate by using one or more gas-phase compounds or simple substances containing film elements. The thickness of the second inorganic encapsulation layer 9 is in the range of 0.5-1 μm, and the material of the second inorganic encapsulation layer 9 may be SiNx (silicon nitride) or SiOx (silicon oxide). The prepared film not only can play a role in antireflection, but also has the functions of surface passivation and body passivation, and can well achieve the water and oxygen blocking packaging effect.

Example 2

As shown in fig. 2, the method for manufacturing the OLED display panel includes: s1, providing a substrate 1, and sequentially preparing a TFT driving layer 2 and an OLED light-emitting layer 3 on the substrate 1; s2, preparing a first inorganic packaging layer 4 on the OLED light-emitting layer 3; s3, preparing an organic encapsulation layer 5 on the first inorganic encapsulation layer 4; s4, preparing a buffer layer 6 on the organic packaging layer 5; s5, preparing a layer of metal on the buffer layer 6, then continuing to perform low-temperature annealing treatment on the prepared metal, and changing the annealed metal into a metal layer 7 formed by the constituent materials thereof in a nanoparticle structure under the energy modification effect of the surface of the buffer layer material; s6, preparing a flat layer 8 on the metal layer 7; s7, preparing a second inorganic encapsulation layer 9 on the planarization layer 8.

The OLED display panel and the method for manufacturing the same according to the present invention are described in detail above. It should be understood that the exemplary embodiments described herein should be considered merely illustrative for facilitating understanding of the method of the present invention and its core ideas, and not restrictive. Descriptions of features or aspects in each exemplary embodiment should generally be considered as applicable to similar features or aspects in other exemplary embodiments. While the present invention has been described with reference to exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention cover the modifications and variations of this invention provided they come within the spirit and scope of the appended claims and their equivalents and improvements made thereto.

Claims

1. An OLED display panel, comprising:

a substrate;

a TFT drive layer disposed on the substrate;

the OLED light emitting layer is arranged on the TFT driving layer;

a first inorganic encapsulation layer disposed on the OLED light emitting layer;

an organic encapsulation layer disposed on the first inorganic encapsulation layer;

a buffer layer disposed on the organic encapsulation layer;

the metal layer is arranged on the buffer layer;

the flat layer is coated on the metal layer; and

a second inorganic encapsulation layer disposed on the planarization layer;

the metal layer is made of metal silver, and the metal layer is of a nanoparticle structure; the buffer layer is made of polyethylene dioxythiophene-polystyrene sulfonic acid.

2. The OLED display panel according to claim 1, wherein the metal layer has a nanoparticle structure with a particle size ranging from 50nm to 150 nm.

3. The OLED display panel of claim 1, wherein the metallic silver has a thickness in the range of 10-12 nm.

4. The OLED display panel of claim 1, wherein the material of the planarization layer is SU-8 photoresist.

5. The OLED display panel of claim 1, wherein the buffer layer has a thickness in a range of 1-1.5 μm and the planarization layer has a thickness in a range of 1-1.5 μm.

6. A method of manufacturing the OLED display panel of claim 1, comprising the steps of:

s4, preparing a buffer layer on the organic packaging layer, wherein the buffer layer is made of polyethylene dioxythiophene-polystyrene sulfonic acid;

s5, preparing a metal layer on the buffer layer, wherein the metal layer is made of metallic silver and is in a nanoparticle structure;

s6, preparing a flat layer on the metal layer; and

and S7, preparing a second inorganic packaging layer on the flat layer.

7. The method of claim 6, wherein the step S5 includes preparing a layer of metal on the buffer layer, and then performing a low-temperature annealing process on the prepared metal, wherein the annealed metal is changed into a metal layer with a nanoparticle structure through the material of the buffer layer under the energy modification effect of the surface of the buffer layer.