KR101850147B1 - Light emitting layer of organic light emitting diodde device and method of fabricating the same - Google Patents

Abstract

The present invention relates to an organic light emitting diode (OLED) device capable of increasing the luminous efficiency of a light emitting layer by controlling the concentration of a dopant distributed in a light emitting layer depending on a position, and a method of manufacturing the same. The organic light emitting diode device of the present invention comprises a substrate; A first electrode and a first associated layer sequentially formed on the substrate; A light emitting layer formed on the first related layer, wherein the host material and the dopant material are mixed, and the concentration of the dopant material varies depending on the position; And a second related layer and a second electrode sequentially formed on the light emitting layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED)

The present invention relates to an organic light emitting diode device and a method of manufacturing the same.

2. Description of the Related Art Recently, various flat panel display devices capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), have been developed. Such a flat panel display device includes a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) And a light emitting device (Electroluminescence Device).

PDP has attracted attention as a display device that is most advantageous for large screen size but small size because of its simple structure and manufacturing process, but it has disadvantage of low luminous efficiency, low luminance and high power consumption. Thin Film Transistor LCD (TFT LCD) is the most widely used flat panel display device, but has a narrow viewing angle and low response speed. The electroluminescence device is classified into an inorganic light emitting diode display device and an organic light emitting diode device depending on the material of the light emitting layer. Among them, the organic light emitting diode device is a self light emitting device that emits itself, has a high response speed, .

An organic light emitting diode (OLED) has a structure as shown in FIG.

The OLED is an organic electronic device that converts electric energy into light energy, and includes an organic light emitting material that emits light between the anode electrode (ANODE) and the cathode electrode (CATHODE). Holes are injected from the anode electrode ANODE and electrons are injected from the cathode electrode CATHODE. When the holes and electrons injected from the electrodes are injected into an organic emission layer (EML) emitting light, excitons are formed. The excitons emit energy while emitting energy to light. A hole injection layer (HIL) and a hole transport layer (HTL) are interposed between the anode electrode ANODE and the light emitting layer EML to facilitate the injection of holes from the anode electrode ANODE to the light emitting layer EML. And an electron injection layer (EIL) and an electron transport layer (EIL) are formed between the cathode electrode CATHODE and the emission layer EML in order to smoothly inject electrons from the cathode electrode CATHODE to the emission layer EML. Electron Transport Layer (ETL) is formed. In order to facilitate hole injection, the hole injection layer (HIL) and the hole transport layer (HTL) must have a highest occupied molecular orbital (HOMO) level between the emission layer (EML) and the anode electrode, (EML) and the electron injection layer (EIL) must have a lowest unoccupied molecular orbital (LUMO) level between the cathode and the light emitting layer emission layer (EML) in order to facilitate electron transfer to the electron transport layer (EML). The luminance from the OLED element and the efficiency characteristics of the element are determined by the amount of holes injected from the anode electrode (ANODE) and the amount of electrons injected from the cathode electrode (CATHODE).

In general, since the mobility of holes is faster than the mobility of electrons, excitons can be formed in regions other than the light emitting layer. In this case, there is a problem that the color stability is lowered as the applied current increases. In order to solve such a problem, an impurity light emitting material (hereinafter referred to as "dopant ") is uniformly distributed in a host luminescent material (hereinafter referred to as a host) Or by adjusting the doping concentration by forming two or more layers of the light emitting layer, thereby increasing the luminous efficiency and improving the color stability.

FIG. 2 is a view showing an organic light emitting diode device manufactured by a conventional method. In FIG. 2 (a), a light emitting layer is formed of two layers of a first light emitting layer (EML1) and a second light emitting layer (EML2) FIG. 2 (b) is a schematic view showing an organic light emitting diode device in which dopants added to the first and second light emitting layers are different from each other. FIG. 2 (b) And FIG.

In the light emitting layers (EML, EML1, EML2) as shown in FIGS. 2A and 2B, a host and a dopant are mixed. The energy band gap, which is the energy difference between the HOMO and LUMO levels of the host, is different from the energy band gap of the dopant. Generally, when two luminescent materials (host and dopant) are mixed, the energy of the excitons generated from the luminescent material having a large energy band gap is transferred to the luminescent material having a small energy band gap, . Therefore, doping the host with a dopant having an energy band gap larger than the energy band gap of the host allows the host to directly contribute to light emission. On the other hand, the dopant that does not contribute to light emission has a HOMO level lower than that of the host, and thus acts as a barrier of holes transported from the hole transport layer. Accordingly, by decreasing the mobility of holes having a higher mobility than that of the former, it is possible to prevent the formation of excitons in a region other than the light emitting layer, thereby improving the luminous efficiency.

However, in such a light emitting layer, since the dopant is uniformly distributed over the entire region of each light emitting layer, the mobility of holes can not be efficiently controlled, or since two or more light emitting layers are used, . In addition, when the dopant doped in the light emitting layer has poor affinity with a material constituting the hole transporting layer or the electron transporting layer adjacent to the light emitting layer, there arises another problem that it may cause another problem.

On the other hand, as a representative method of forming the conventional light emitting layer (EML), a method using an organic vapor phase deposition (OVPD) or a fine metal mask (FMM) is known.

Organic gas-phase deposition (OVPD) is a method in which a host and a dopant material are simultaneously heated in one deposition chamber, and the sublimated organic molecules are transferred to a cold substrate by using nitrogen gas or the like. This method has a problem in that it is not suitable for mass production due to a problem that an additional investment of the deposition chamber is required when the light emitting layer is formed in two or more layers and the process time is increased.

In the fine metal mask method (FMM), red, green, and blue light-emitting materials are formed by patterning each pixel using a metal fine mask. Although this method has excellent advantages in terms of device characteristics, the process yield is lowered due to clogging of the mask, and it is difficult to apply a large display device due to difficulty in developing a large mask.

As described above, there is a problem that the mobility of holes can not be efficiently controlled by using a light emitting layer in which a dopant is uniformly distributed in an organic light emitting diode device. In the case of using two or more light emitting layers formed with different dopant concentrations, And there is a problem in mass production.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to control the distribution gradient of the dopant in the light emitting layer to appropriately control the hole mobility and solve the problems caused by the affinity of the materials with neighboring hole transporting layers and electron transporting layers And a method of manufacturing the same.

In order to achieve the above object, an organic light emitting diode device according to an embodiment of the present invention includes a substrate; A first electrode and a first associated layer sequentially formed on the substrate; A light emitting layer formed on the first related layer, wherein the host material and the dopant material are mixed, and the concentration of the dopant material varies depending on the position; And a second related layer and a second electrode sequentially formed on the light emitting layer.

According to another aspect of the present invention, there is provided a method of manufacturing an organic light emitting diode (OLED) device, comprising: sequentially forming a first electrode and a first associated layer on a first substrate; Sequentially forming at least one first light emitting material layer and at least one second light emitting material layer on a second substrate; Aligning the first substrate and the second substrate such that the first related layer and the second luminous material layer face each other; A transfer step of sublimating the first and second light emitting material layers by applying energy to the second substrate and transferring the first and second light emitting material layers to the first substrate to form a light emitting layer; And sequentially forming a second related layer and a second electrode on the light emitting layer formed in the transfer step.

In the above structure, the first electrode and the second electrode may be an anode electrode and a cathode electrode, respectively, and the first associated layer may be formed of a hole-related layer that is responsible for the inflow and transport of holes and vice versa.

In addition, it is preferable that the transferring step is performed by laser induced thermal imaging (LITI) or joule heat transfer, and the energy may be obtained by using any one of laser energy, infrared energy, ultraviolet energy and electric energy good.

Further, it is preferable that at least one of the first and second light emitting layers is alternately laminated on the first substrate.

Alternatively, the first light emitting layer may be a dopant material layer, the second light emitting layer may be a host material layer, the first light emitting layer may be a host material layer, and the second light emitting layer may be a dopant material layer.

According to the organic light emitting diode device and the manufacturing method thereof according to the embodiment of the present invention, the concentration of the dopant distributed in the light emitting layer can be appropriately controlled so as to be changed depending on the position, An organic light emitting diode device capable of solving the problems caused by the affinity of a hole transporting layer and an electron transporting layer adjacent to each other and an efficiency of a normal manufacturing process and a manufacturing method thereof have.

Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 3 to 8. FIG. Like reference numerals refer to like elements throughout the specification.

FIG. 3 is a flow chart schematically illustrating a method of manufacturing an organic light emitting diode (OLED) according to an embodiment of the present invention. FIGS. 4A and 4B are cross- 5A to 5F are cross-sectional views illustrating various processes for forming a host layer and a dopant layer on a donor substrate. FIGS. 5A to 5F are cross-sectional views illustrating a process of forming a hole-related layer including a hole injection layer and a hole injection layer, And FIGS. 6A to 6F are cross-sectional views showing a state in which the dopant is formed in the light emitting layer with a constant gradient by the adhesion and transfer of the donor substrate and the acceptor substrate shown in FIGS. 5A to 5F, FIG. 8 is a cross-sectional view illustrating a state in which an electron-transporting layer and an electron-transporting layer of an electron-injecting layer and a second electrode of an OLED are formed on an acceptor substrate having a light- Table and graph comparing electrical characteristics and life span according to embodiments of the invention.

Referring to FIG. 3, a method of manufacturing an organic light emitting diode (OLED) device according to an embodiment of the present invention includes a step S1 of forming an acceptor substrate, a step S2 of forming a donor substrate, a step of attaching an acceptor substrate and a donor substrate, A coalescing and transferring step (S3) of transferring the host layer and the dopant layer formed on the substrate to the acceptor substrate, and a step (S4) of forming the electron-associating layer and the second electrode on the acceptor substrate.

In the step of forming the acceptor substrate (S1), the first electrode of the OLED and the hole-related layer (HIL / HTL) are sequentially formed on the acceptor substrate. In the donor substrate formation step (S2), the host layer and the dopant layer as the light emitting material are separately formed. In the laminating and transferring step (S3), the acceptor substrate and the donor substrate are aligned and adhered, and then the host layer and the donor layer formed on the donor substrate are sublimated using the laser heat transfer method, the joule heat transfer method, Thereby forming a light emitting layer. In the electron-related layer and the second electrode forming step S4, the electron-related layers ETL and EIL and the second electrode are sequentially formed on the acceptor substrate on which the light-emitting layer is formed.

First, an acceptor substrate forming step (S1) will be described in more detail with reference to Figs. 4A and 4B.

Referring to FIG. 4A, a first electrode 110 of an OLED is formed on an acceptor substrate 100 made of transparent glass or a plastic material. The first electrode 110 may be an anode electrode or a cathode electrode. When the first electrode 110 is used in a display device, it is preferable that the first electrode 110 is a transparent conductive layer containing an oxide such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). The first electrode 110 supplies holes to the light-emitting layer via hole-related layers (HIL, HTL) to be described later.

Referring to FIG. 4B, the hole injection layer 120 and the hole transport layer 130 are successively formed on the first electrode, that is, the susceptor substrate 100 on which the anode electrode 110 is formed, using a thermal evaporation method. The hole-related layer is formed.

Next, the donor substrate forming step (S2) will be described in more detail with reference to Figs. 5A to 5F.

Referring to FIGS. 5A to 5F, on the donor substrate 200 made of transparent glass or plastic, a dopant layer and a host layer as a light emitting material are separately formed. FIGS. 5A to 5F show various embodiments in which the donor substrate 200 and the host layer are alternately formed on the donor substrate 200. The dopant layer and the host layer are respectively formed on the donor substrate 200 by a process such as thermal evaporation. 5A shows an example of a donor substrate on which a first dopant layer 210 and a first host layer 220 are sequentially formed on a donor substrate 200. FIG. FIG. 5C shows an example of a donor substrate 210 on which a first dopant layer 210, a first host layer 220 and a second dopant layer 213 are sequentially formed. 5D shows an example of a donor substrate on which a first host layer 220, a second dopant layer 213 and a second host layer 223 are sequentially formed. 5E shows an example of a donor substrate on which a first host layer 220, a first dopant layer 210 and a second host layer 210 are sequentially formed on a donor substrate 200, A first host layer 220, a first dopant layer 210, a second host layer 223, and a second host layer 223 are sequentially stacked on a donor substrate 200, 2 dopant Layer 213 is sequentially formed on the donor substrate. In the present embodiment, the host layer, the dopant layer, the dopant layer, and the host layer are alternately arranged on the donor substrate 200, and the present invention is not limited thereto. Of course not. The order and number of layers for forming the dopant layer and the host layer in accordance with the technical idea of the present invention fall within the scope of the present invention.

Next, the laminating and transferring step (S3) will be described in more detail with reference to Figs. 6A to 6F. 6A to 6F are views showing a step of transferring the light emitting layer to the acceptor substrate using the donor substrate of Figs. 5A to 5F.

6A, an acceptor substrate 100 on which hole-related layers 120 and 130 are formed, a donor substrate 200 on which a first dopant layer 210 and a first host layer 220 are sequentially formed, And cemented. This alignment and cementation process is performed under a vacuum or inactive gas (Ar, N _2, etc.) atmosphere to protect the organic light emitting material, which is the first dopant layer 210 and the first host layer 220, from moisture / . Adhesion may also be achieved by mechanical pressing. Thermal energy is applied from the outside to the donor substrate 200 on which alignment and adhesion processes have been completed. Laser, infrared, ultraviolet, electrical resistance can be used as an energy source for supplying such heat energy. In the present invention, since the dopant layer 210 and the host layer 220 are formed on the donor substrate 200 as separate layers, the laser induced thermal imaging (LITI) or Joule heat transfer The transfer process can be more effectively achieved. When a laser thermal transfer method is used, a first dopant layer 210 and a first host layer 220 are sequentially formed on a transfer film (not shown), and light such as a laser beam is irradiated from the back surface of the donor substrate 200 The dopant layer 210 and the host layer 220 on the transfer film are transferred onto the acceptor substrate 100 to form the light emitting layer 230. [ In the case of using the Joule heat transfer method, a heating pattern (not shown) is formed below the host layer and / or the dopant layer and a power source is connected from the outside to generate heat in the heating pattern, thereby forming the dopant layer 210, And the host layer 220 are sublimated to form the light emitting layer 230 on the acceptor substrate 200.

The process of forming the light emitting layer 230 by transferring the dopant layer 210 and the host layer 220 formed on the donor substrate 200 to the acceptor substrate 100 will now be described in more detail. When heat is conducted to the dopant layer 210 and the host layer 220 formed on the donor substrate 200 by the laser thermal transfer method or the Joule heat transfer method, the dopant layer 210 and the host layer 220, Are successively sublimated and transferred to the susceptor substrate 100. That is, the relatively small amount of the dopant light emitting material 231 sublimated by the thermal energy penetrates the relatively large amount of the host light emitting material 232 to produce the light emitting layer 230 in a mixed state with each other. As a result, as shown in the right side of FIG. 6A, the dopant light emitting material 231 is more dispersed on the side closer to the donor substrate 200, that is, on the upper side of the light emitting layer 230.

In FIGS. 6B to 6F, since the light emitting layers 240, 250, 260, 270 and 280 are formed through the same processes as those of FIG. 6A, detailed description thereof will be omitted here. The formation positions of the first and second dopant layers 210 and 213 and the first and second host layers 220 and 223 formed on the donor substrate 200, The dopant light emitting materials 241, 251, and 252 distributed in the host light emitting materials 242, 252, 262, 272, and 282 of the light emitting layers 240, 250, 260, 270, and 280 formed on the acceptor substrate 100, 261, 271, and 281 may be formed at positions different from each other. Therefore, the number of layers of the dopant layer, the host layer, and the stacking order formed on the donor substrate 200 can be appropriately selected to form the light emitting layer having a different dopant concentration depending on the position in the light emitting layer. When the light emitting layer having a different dopant concentration is formed on the acceptor substrate by the above-described transfer step, the donor substrate and the acceptor substrate are separated.

Next, the step S4 of forming the electron-related layer (ETL / EIL) and the second electrode on the acceptor substrate will be described with reference to Fig. For simplicity of explanation, the case of the light emitting layer formed by the method of FIG. 6A will be described as an example.

7, an electron transport layer 300 and an electron injection layer 400 are continuously and entirely deposited on an acceptor substrate 100 on which an emission layer 230 is formed by a thermal evaporation process to form an electron- 300, and 400 are formed. The hole-related layers 120 and 130, the light-emitting layer 230, and the electron-related layers 300 and 400 constitute an organic compound layer of the OLED.

Next, the second electrode 500 of the OLED is formed on the front surface of the acceptor substrate 100 on which the electron-related layers 300 and 400 are formed. The second electrode 500 may be formed as a cathode electrode in a single layer structure of a metal material and may also be formed in a multi-layer structure including first and second metal layers sandwiched between the dielectric layers. The second electrode 500 applies the electrons applied through the Vss supply wiring to the organic compound layer.

FIGS. 8 and 9 are tables and graphs showing the effect of improving the luminous efficiency and lifetime of the OLED according to the embodiment of the present invention.

8 is a table and a graph comparing the electrical characteristics and lifetime of the OLED according to the conventional art and the OLED according to the embodiment of the present invention.

FIG. 8A is a graph showing electrical characteristics when a current of 10 mA / cm 2 is supplied to a conventional OLED and an OLED according to the embodiment of FIG. 7 of the present invention. FIG. Fig.

8 (a) and 8 (b), it can be seen that the electrical characteristics and lifetime of the OLED according to the embodiment of the present invention are improved as compared with the conventional OLED. ,

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. For example, in the embodiment of the present invention, the first electrode and the second electrode are described as the anode electrode and the cathode electrode, respectively. However, the technical idea of the present invention is not limited to this, and the first electrode and the second electrode may be referred to as a cathode electrode and an anode Even when the electrode is used, it is applied as it is. In this case, the hole-related layer described in the embodiment may be replaced with an electron-related layer, and the electron-related layer described in the embodiment may be replaced with a hole-related layer. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a structure of an organic light emitting diode. FIG.

2 is a view showing an organic light emitting diode device manufactured by a conventional method.

3 is a flowchart illustrating a method of manufacturing an organic light emitting diode device according to an embodiment of the present invention.

4A and 4B are cross-sectional views illustrating a process of forming a hole-related layer including a first electrode, a hole injection layer, and a hole transport layer on an acceptor substrate.

5A to 5F are cross-sectional views showing various examples of forming a host layer and a dopant layer on a donor substrate;

6A to 6F are cross-sectional views showing a state in which a dopant is formed in the light emitting layer with a constant gradient by coalescence and transfer of the donor substrate and the acceptor substrate shown in Figs. 5A to 5F.

7 is a cross-sectional view showing a state in which an electron-transporting layer and an electron-transporting layer of an electron-injecting layer and a second electrode of an OLED are formed on an acceptor substrate on which a light-emitting layer is formed;

8 is a table and graph comparing the electrical characteristics and lifetime according to the OLED according to the prior art and the embodiment of the present invention.

Description of the Related Art

100: Acceptor substrate 110: First electrode

120: Hole injection layer 130: Hole transport layer

200: donor substrate 210, 213: dopant layer

220, 223: host layer

220, 230, 240, 250, 260, 270, 280:

300: electron transport layer 400: electron injection layer

500: Second electrode

Claims (9)

delete delete delete Sequentially forming a first electrode and a first associated layer on a first substrate; Forming heating patterns on a second substrate, and sequentially forming at least one first light emitting material layer and at least one second light emitting material layer to contact with the heating patterns; Aligning the first substrate and the second substrate such that the first related layer and the second luminous material layer face each other; The at least one first light emitting material layer and the at least one second light emitting material layer are sublimated and transferred to the first substrate by applying electrical energy by connecting a power source to the heating patterns of the second substrate, 1) a step of forming a light-emitting layer on an associated layer; Sequentially forming a second related layer and a second electrode on the light emitting layer of the first substrate formed in the transfer step, The concentration of the first luminescent material layer is increased or decreased from the first surface to the second surface between a first surface close to the first related layer of the light emitting layer and a second surface close to the second related layer And repeating the increase or decrease of the thickness of the organic light emitting diode. 5. The method of claim 4, Wherein the step of transferring is performed by Joule heat transfer method. delete 5. The method of claim 4, Wherein the at least one first light emitting material layer and the at least one second light emitting material layer are alternately stacked on the first substrate. 5. The method of claim 4, Wherein the at least one first light emitting material layer is a dopant material layer and the at least one second light emitting material layer is a host material layer. 5. The method of claim 4, Wherein the at least one first light emitting material layer is a host material layer and the at least one second light emitting material layer is a dopant material layer.

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