KR20040013969A - Method for fabricating an electrode in organic electro luminescence display - Google Patents

Abstract

PURPOSE: A method is provided to reduce costs and allow for ease of dry or wet etching, while achieving improved characteristics of hole injection. CONSTITUTION: A method comprises a step of forming an anode electrode pattern(20) through a photo lithography process by depositing a nickel on a glass substrate(10); a step of depositing a material to be used as a hole injection layer on the anode electrode pattern, wherein the material includes a poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonated acid(30); a step of depositing a high/low molecular organic light emitting layer(40) on the hole injection layer; and a step of forming a cathode electrode pattern on the high/low molecular organic light emitting layer, wherein the cathode electrode pattern includes an electron injection thin film(50-1) and a transparent conductive layer(50-2).

Description

Electrode fabrication method of organic EL device {METHOD FOR FABRICATING AN ELECTRODE IN ORGANIC ELECTRO LUMINESCENCE DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode fabrication method of an organic EL (Electro Luminescence Display) device, and more particularly to an electrode fabrication method of a top emission method using nickel, a high work function material, as an anode will be.

In general, organic EL displays are active-driven self-luminous devices that can be driven even at low voltages, providing low-power consumption and high luminous efficiency, providing high quality data, and providing fast moving images, resulting in perfect moving images, and limited viewing angles. It is a next-generation display that can see the contents of the screen from any location.

These active-driven organic EL displays are suitable for flat panel displays because they can be manufactured in a thin film form without any backlight as they do not have any kind of moving picture display media from small to large due to the advantages of wide viewing angle and ultra-fast response speed. In addition, since it can be manufactured at low temperature, it is advantageous to lower the price.

In addition, active-drive type organic EL displays are attracting attention due to their high resolution and low power consumption. FIG. 1 shows a top emission method and a bottom emission method according to the emission direction of an organic EL element. The drawing is divided into a) method, and is classified into a top emission method and a bottom emission method according to the emission direction.

That is, the top emission method refers to a method in which light is directed in the opposite direction of the substrate, and the bottom emission method refers to a method in which light emitted in the direction of the substrate is emitted through the substrate.

In other words, in the bottom emission method, since the light is directed toward the substrate, the actual pixel area (aperture ratio) that emits light depends on the design of the pixel such as the number of transistors, the wiring width, and the storage capacity. In an organic EL requiring three to four or more transistors, the aperture ratio is inevitably small. Therefore, as the resolution increases, the increase of the driving voltage and the current increases, and the increase of the driving voltage and the current leads to an increase in power consumption and a reduction in the lifespan of the display panel.

On the other hand, the top emission method is much more advantageous than the bottom emission method in terms of power consumption and lifespan because the light emitting pixel area does not vary greatly depending on the pixel design since the direction of light is directed toward the opposite direction of the substrate.

However, in the top emission type organic EL device, since light must be directed in a direction opposite to the direction of the substrate, gold (Au), platinum (Pt), or aluminum (Al), which are opaque metal electrodes, are used as the anode electrode. A transparent conductive oxide film such as indium tin oxide (ITO), which transmits light through the electrode and is electrically used, is used.

As shown in FIG. 2, Pt and Au used as the anode electrode have a good work characteristic because of easy work of injecting holes due to a large work function, but are expensive and difficult to wet and dry etch. Due to the fast diffusion through, there is a problem in that it adversely affects the characteristics of the thin film transistor for driving the pixel.Al also, Al of the anode electrode is cheap and easy to process, but because of its small work function, it is not easy to inject holes. There is a problem of deterioration.

Accordingly, the present invention has been made to solve the problems described above, the object of which is to fabricate an electrode of an organic EL device in a top emission method using a nickel (Nickel), a high work function material as an anode material In providing a method.

Electrode fabrication method of the organic EL device in the present invention for achieving the above object is to form a pattern of the anode (anode (+)) electrode through a photolithography process by depositing nickel (Nickel) as the anode material on a glass substrate step; After forming the anode electrode pattern, applying a material (PEDT: Pos (Poly (3,4-ethylenedioxythiophene) doped with polystyrene sultponated acid) (PEDT) that can be used as a hole injection layer on the electrode pattern; Applying a polymer / low molecular weight organic light emitting layer to a PEDT: PSS material; And forming a pattern of a cathode (cathode) electrode as a double layer on the polymer / low molecular weight organic light emitting layer by using an electron injection ultra thin film and a transparent conductive layer.

FIG. 1 is a diagram divided into a top emission method and a bottom emission method according to an emission direction of an organic EL device.

2 is a diagram illustrating etching characteristics of Pt and Au metal electrodes in an organic EL device,

3A to 3D are diagrams illustrating an electrode fabrication process using a top emission method using nickel, which is a high work function material, as an anode material in an organic EL device according to an exemplary embodiment of the present invention.

4 is a view showing a bipolar structure of a bi-layer structure using a conductive layer and Nickel according to another embodiment of the present invention,

FIG. 5 is a diagram showing current-voltage characteristics when nickel, a high work function material, is used as an anode material according to an embodiment of the present invention.

6 is a view showing etching characteristics of a Nickel metal electrode in the organic EL device according to the present invention.

<Description of the symbols for the main parts of the drawings>

DESCRIPTION OF SYMBOLS 10 Glass substrate 20 Pattern of an anode (for example, anode (+)) electrode

20-1: conductive layer 30: PEDT: PSS material

40: polymer / low molecular organic light emitting layer 50-1: electron injection ultra-thin film

50-2: transparent conductive layer

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3A to 3D are diagrams illustrating an electrode fabrication process using a top emission method using nickel, which is a high work function material, as an anode material in the organic EL device according to the present invention.

That is, referring to FIG. 3A, nickel (Nickel), which is an anode material, is deposited on the glass substrate 10 to form a pattern 20 of an anode (eg, anode (+)) electrode through a photolithography process. Here, the pattern 20 of the electrode may be formed on the plastic substrate 10 instead of the glass substrate 10.

Next, as shown in FIG. 3B, after the anode electrode pattern 20 is formed, a material that can be used as a hole injection layer for hole injection and modification of the electrode surface on the electrode pattern 20 (PEDT: PSS (Poly ( 3,4-ethylenedioxythiophene) doped with polystyrene sultponated acid)) (30).

In the state where the PEDT: PSS material 30 is applied, the polymer organic light emitting layer 40 is coated on the PEDT: PSS material 30 using an evaporation, spin coating, or inkjet method as shown in FIG. 3C. Or to a selected area. Here, the low molecular weight organic light emitting layer 40 may be applied instead of the high molecular weight organic light emitting layer 40. In particular, when the spin coating method is applied, the low molecular weight organic light emitting layer 40 may be dried in a vacuum at 100 ° C.

Lastly, a transparent electron injection layer having a low work function on the polymer / low molecular organic light emitting layer 40 includes aluminum (Al), lithium (Li), lithium fluoride (LiF), magnesium (Mg), calcium (Ca), A cathode (for example, a cathode) electrode is formed by using a double layer of an electron injection ultrathin film 50-1, which is silver (Ag), and a transparent conductive layer 50-2, which is ITO (IZO) or indium zinc oxide (IZO) having good electrical conductivity. Form a pattern.

On the other hand, Figure 4 is a diagram showing the anode structure of the double layer structure using a conductive layer and Nickel according to another embodiment of the present invention, when forming the anode electrode pattern in the process of Figure 3a, Al, copper (Cu ), An Al-alloy, ITO conductive layer 20-1 and nickel (Nickel) 20 is a double layer to form an anode electrode pattern.

FIG. 5 is a diagram illustrating current-voltage characteristics when nickel, which is a high work function material, is used as an anode material, according to an embodiment of the present invention. When nickel is used as an anode material, ITO, Compared with Al, the device has the same current characteristics at lower driving voltages, whereas Pt anode material has the same current at lower drive voltages than the nickel anode material. Anode material is expensive and difficult to wet and dry etching.

As described above, as nickel (Nickel), which is a high work function material, is used as the anode material, as shown in FIG. 6, the etching characteristics of the Nickel metal electrode are improved in the organic EL device, thereby improving device characteristics.

As described above, the present invention uses nickel as a high work function material as an anode material to fabricate an electrode of an organic EL device in a top emission method, compared to an anode material of aluminum or ITO. The hole injection characteristics are improved, and thus the device characteristics are improved, and the price is lower than that of Pt or Au, and it is easy to dry and wet etching.

Claims (9)

In the electrode manufacturing method of the top emission organic EL (Electro Luminescence Display) device, Depositing nickel, an anode material, on the glass substrate to form a pattern of an anode (anode) electrode through a photolithography process; After forming the anode electrode pattern, applying a material usable as a hole injection layer on the electrode pattern; Applying a polymer / low molecular weight organic light emitting layer to the hole injection layer; And forming a pattern of the cathode (cathode) electrode using a double layer of an electron injection ultra thin film and a transparent conductive layer on the polymer / low molecular organic light emitting layer. The method of claim 1, The glass substrate is an electrode manufacturing method of an organic EL device, characterized in that used by replacing the plastic film. The method of claim 1, The hole injection layer material is a method for manufacturing an electrode of an organic EL device, characterized in that for the injection of holes and modification of the electrode surface. The method of claim 1, The polymer / low molecular weight organic light emitting layer is coated by an evaporation, spin coating, or inkjet method. The method of claim 4, wherein The polymer / low molecular weight organic light emitting layer is coated on an entire surface or a selected region of the hole injection layer material. The method of claim 1, The electron injection ultra-thin film is a transparent electron injection layer having a low work function, characterized in that the aluminum (Al), lithium (Li), lithium fluoride (LiF), magnesium (Mg), calcium (Ca), silver (Ag) The electrode manufacturing method of organic electroluminescent element made into. The method of claim 1, The transparent conductive layer is a transparent oxide film having good electrical conductivity, indium tin oxide (ITO), indium zinc oxide (IZO) electrode manufacturing method of an organic EL device, characterized in that. The method of claim 1, The anode electrode pattern is an electrode manufacturing method of an organic EL device, characterized in that the conductive layer of Al, copper (Cu), Al-alloy, ITO and nickel (Nickel) is formed in a double layer. The method of claim 1 And said cathode electrode has a single layer cathode electrode layer using a transparent oxide film having a low work function.