KR20030026421A - Electro-luminescence Display Device and Method of Fabricating The Same - Google Patents

Abstract

PURPOSE: An organic electroluminescence device and a method for manufacturing the same are provided to lower the electric resistance while increasing the degree of crystallinity. CONSTITUTION: An organic electroluminescence device comprises an anode electrode(32) formed on a substrate(31) and a seed layer(44) formed between the anode electrode(32) and the substrate(31) to crystallize the material which forms the anode electrode(32). The electroluminescence device comprises a cathode electrode(40) opposing to the anode electrode(32), a hole injecting layer(34) for receiving a hole from the anode electrode(32), an electron injecting layer(38) for receiving an electron from the cathode electrode(40) and an emitting layer(36) for exciting fluorescent material by collision between the hole from the hole injecting layer and the electron from the electron injecting layer. A protective layer is additionally provided between the seed layer(44) and the substrate(31).

Description

Organic electroluminescent device and its manufacturing method {Electro-luminescence Display Device and Method of Fabricating The Same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat panel display, and more particularly, to an organic electroluminescent device capable of lowering an electrical resistance value and increasing crystallinity, and a method of manufacturing the same.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Such flat panel displays include liquid crystal displays (hereinafter referred to as "LCDs"), field emission displays (FEDs) and plasma display panels (hereinafter referred to as "PDPs") and electroluminescence. (Electro-luminescence: "EL") display devices, etc. Researches are being actively conducted to improve the display quality of such flat panel display devices and to make large screens, among which PDP has a simple structure and manufacturing process. However, it is attracting attention as a display device that is lightest, lightest and smallest, but has the disadvantage of low luminous efficiency, low brightness, and high power consumption, whereas a thin film transistor (TFT) is used as a switching element. Active matrix LCD uses a semiconductor process, which makes it difficult to display large screens. Increasing demand, however, has the disadvantage that LCDs are difficult to make large areas, and power consumption is large due to the backlight unit, and LCDs have high light loss and viewing angles due to optical elements such as polarizing filters, prism sheets, and diffusion plates. In contrast, the EL display device is classified into an inorganic EL and an organic EL according to the material of the light emitting layer. The EL display device is a self-light emitting device that emits light by itself, and has a high response speed and high luminous efficiency, luminance, and viewing angle.

As shown in FIG. 1, the organic EL device includes a hole injection layer 4 formed on the substrate 1 between the anode electrode 2 and the cathode electrode 10, and between the anode electrode 2 and the cathode electrode 10. ), A light emitting layer 6 and an electron injection layer 8.

The cathode electrode 10 is formed of a metal thin film such as Au, Ag, Pt, Pd. The cathode electrode 10 receives a scanning pulse from a gate driving circuit (not shown). The anode electrode 2 is formed of an oxide thin film of ITO, IZO, GZO, CdO, or the like. The anode 2 receives data from a data driving circuit (not shown).

When scanning pulses are supplied to the cathode electrode 10 and data is applied to the anode electrode 2, holes are accelerated toward the cathode electrode 10 and electrons are accelerated toward the anode electrode 2.

The electron injection layer 8 accelerates and supplies electrons supplied from the cathode electrode 10 to the light emitting layer 6. The hole injection layer 4 accelerates the holes supplied from the anode electrode 2 and supplies them to the light emitting layer 6.

Holes supplied from the hole injection layer 4 and electrons supplied from the electron injection layer 8 collide at the center of the light emitting layer 6. The light emitting layer 6 generates visible light when colliding with electrons and holes.

When the substrate 1 of such an organic EL display element is formed of soda-lime glass, damage and characteristic change of the element are caused by alkali ions such as Na + contained in the substrate 1. Accordingly, as shown in FIG. 2, a silicon nitride (SiO ₂ ) is deposited on the substrate 1 to form a protective film 12.

Since the anode electrode 2 is formed on the substrate 1 on which the protective film 12 having the amorphous structure is formed, in order to form a crystallized structure, the substrate 1 is deposited when the oxide thin film forming the anode electrode 2 is deposited. Raising the temperature to a high temperature or after the deposition process requires a separate heat treatment process. As a result, when crystallization occurs, the anode electrode 2 is formed on the substrate 1, so that the anode electrode 2 does not have an orientation along a specific crystal plane as shown in FIG. That is, the oxide thin film forming the anode electrode 2 has four array directions in the directions of (211), (222), (400), and (440). Accordingly, the atoms of the oxide thin film are scattered in various directions and arranged randomly, so that even after crystallization, the electrical resistance value does not have a low value enough to be used as a wiring electrode material of the organic EL element.

In order to solve this problem, the charge transporter concentration is inversely proportional to the electrical resistance value of the oxide thin film. The charge transporter concentration is approximately 10 ²⁰ / cm 3 to 10 ²¹ / cm 3, and the variables for determining the charge transporter concentration include the content of Sn atoms (donate one electron) and oxygen vacancies (donate two electrons). There is this. If the concentration of the charge transporter is increased by using these variables, the electrical resistance of the oxide thin film is lowered, but there is a problem that the values of visible light transmittance and work function are reduced.

Accordingly, an object of the present invention is to provide an organic electroluminescent device and a method of manufacturing the same, which can lower the electrical resistance value and increase the crystallinity.

1 is a cross-sectional view schematically showing a conventional organic electroluminescent device.

2 is a cross-sectional view showing a conventional organic electroluminescent device having a protective layer formed between a substrate and an anode electrode.

FIG. 3 is a graph showing an X-ray diffraction pattern of the anode electrode shown in FIG. 2.

4 is a cross-sectional view showing an organic electroluminescent device according to a first embodiment of the present invention.

5 is a cross-sectional view of an organic electroluminescent device according to a second embodiment of the present invention.

6 is a graph showing an X-ray diffraction pattern of the anode electrode shown in FIGS. 4 and 5.

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

1,31 substrate 2,32 anode electrode

4,34: hole injection layer 6,36: light emitting layer

8,38 electron injection layer 10,40 cathode electrode

12,42: protective layer

In order to achieve the above object, the organic electroluminescent device according to the present invention comprises an anode electrode formed on the substrate, and a seed layer formed between the anode electrode and the substrate to crystallize the material forming the anode electrode do.

The organic electroluminescent device includes a cathode electrode formed to face the anode electrode, a hole injection layer supplied with holes from the anode electrode, an electron injection layer supplied with electrons from the cathode electrode, and a hole from the hole injection layer And an emission layer for exciting electrons from the electron injection layer to excite the fluorescent material.

A protective film is further provided between the seed layer and the substrate.

The protective film is formed of an insulating material such as silicon nitride.

The seed layer is characterized in that formed of YSZ, MgO, ZrO ₂ , ZnO and the like.

The seed layer is characterized in that formed of a non-conductive material.

The anode electrode is formed of an oxide thin film such as ITO, IZO, GZO, CdO, or the like.

The material for forming the cathode is characterized in that formed of a metal thin film, such as Au, Ag, Pt, Pd.

In order to achieve the above object, a method of manufacturing an organic electroluminescent device according to the present invention comprises the steps of forming a seed layer on the substrate, forming an anode electrode having a high crystallinity with the seed layer, on the anode electrode Forming a hole injection layer, forming a light emitting layer on the hole injection layer, forming an electron injection layer on the light emitting layer, and forming a cathode on the electron injection layer.

The method of manufacturing the organic electroluminescent device further comprises forming a protective film between the seed layer and the substrate.

The protective film is formed of an insulating material such as silicon nitride.

The seed layer is characterized in that formed of YSZ, MgO, ZrO ₂ , ZnO and the like.

The seed layer is characterized in that formed of a non-conductive material.

The anode electrode is formed of an oxide thin film such as ITO, IZO, GZO, CdO, or the like.

The material for forming the cathode is characterized in that formed of a metal thin film, such as Au, Ag, Pt, Pd.

Other objects and advantages of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 4 to 6.

Referring to FIG. 4, the organic EL device according to the present invention includes a protective layer 42 and a seed layer 44 formed between the substrate 31 and the anode electrode 32. A hole injection layer 34, a light emitting layer 36, and an electron injection layer 38 formed between the anode electrode 32 and the cathode electrode 40 are provided.

The protective layer 42 is formed of an insulating material such as silicon nitride (SiO ₂ ) on the substrate 31 in order to prevent damage to the element and change of characteristics of alkali ions such as Na + contained in the substrate 31. .

The seed layer 44 is formed on the protective layer 42 to reduce the electrical resistance of the anode electrode 32. The seed layer 44 increases the crystallinity of the oxide thin film forming the anode electrode 32 to reduce the electrical resistance of the anode electrode 32. The seed layer 44 is formed of any one of YSZ, MgO, ZrO 2, and ZnO. In particular, when ZnO is formed as the seed layer 44, the lattice constant misalignment based on the closest oxygen atom with respect to the anode electrode 32 having a hexagonal dense structure and Bix byte crystal structure is within 3%. to be. In addition, since the (0001) plane of ZnO and (111), which is the lowest dense plane of ITO, are well matched, the electrical conductivity of the anode electrode 32 increases as the crystallinity increases.

The cathode electrode 40 is formed of a metal thin film such as Au, Ag, Pt, Pd. The cathode electrode 40 receives a scanning pulse from a gate driving circuit (not shown). The anode electrode 32 is formed of an oxide thin film of ITO, IZO, GZO, CdO, or the like. The anode electrode 32 receives data from a data driving circuit (not shown).

When scanning pulses are supplied to the cathode electrode 40 and data is applied to the anode electrode 32, holes are accelerated toward the cathode electrode 40 and electrons are accelerated toward the anode electrode 32.

The electron injection layer 38 accelerates and supplies electrons supplied from the cathode electrode 40 to the emission layer 36. The hole injection layer 34 accelerates the holes supplied from the anode electrode 32 and supplies them to the light emitting layer 36.

Holes supplied from the hole injection layer 34 and electrons supplied from the electron injection layer 38 collide at the center of the light emitting layer 36. The light emitting layer 36 generates visible light when the electrons and holes collide with each other.

Referring to FIG. 5, the organic EL device according to the second embodiment of the present invention may have a seed layer that serves as a protective layer between the substrate 31 and the anode electrode 32 as compared to the organic EL device shown in FIG. 4. 42) with the same components except that they are formed.

Since the seed layer 42 is formed of an electrically nonconductive material and has electrical insulation properties, the seed layer 42 serves as a protective film against alkali ions such as Na +.

FIG. 6 is a graph showing the internal crystal structure of the oxide thin film forming the anode electrode 32 shown in FIGS. 4 and 5, in which the vertical axis represents the intensity of diffracted X-rays.

It can be seen that the internal crystal structure of the oxide thin film forming the conventional anode electrode 2 is formed in four directions so that atoms forming the oxide are randomly formed in various directions, thereby reducing the crystallinity of the oxide thin film.

On the other hand, in the oxide thin film forming the anode electrode 32 of the present invention, the seed layer 42 is formed under the oxide thin film so that the internal crystal structure of the oxide thin film is formed in the same direction as the seed layer 42 in the (222) direction. do. Accordingly, it can be seen that the crystallinity of the oxide thin film is increased due to the preferential orientation according to the specific crystal plane as in the seed layer 42. As the degree of crystallinity increases, the grain boundary area decreases, so that carrier scattering at the grain boundary decreases, and the probability of Sn being substituted into the In ₂ O ₃ structure increases, thereby decreasing the electrical resistance.

As described above, the electroluminescent display device according to the present invention forms a seed layer between the anode electrode and the substrate. By forming this seed layer, the crystallinity of the anode electrode is improved and the electrical resistance is reduced. As a result, the voltage drop to the resistive portion of the electrode is reduced, so that the power loss is reduced, which further helps to prolong the life of the organic EL element.

In addition, by forming the seed layer with an electrically insulating material, the seed layer serves as a protective film for alkali ions, thereby reducing the production cost.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. 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.

Claims (15)

An anode formed on the substrate, And a seed layer formed between the anode electrode and the substrate to crystallize a material forming the anode electrode. The method of claim 1, A cathode electrode formed to face the anode electrode; A hole injection layer receiving holes from the anode electrode, An electron injection layer receiving electrons from the cathode electrode; An organic electroluminescent device, further comprising a light emitting layer for exciting holes from the hole injection layer and electrons from the electron injection layer to excite the fluorescent material. The method of claim 1, An electroluminescence display device further comprising a protective film between the seed layer and the substrate. The method of claim 3, wherein The protective film is an organic electroluminescent device, characterized in that formed of an insulating material such as silicon nitride. The method of claim 1, The seed layer is organic electroluminescent device, characterized in that formed of YSZ, MgO, ZrO ₂ , ZnO and the like. The method of claim 1, The seed layer is an organic electroluminescent device, characterized in that formed of a non-conductive material. The method of claim 1, The anode forming material is an organic electroluminescent device, characterized in that formed of an oxide thin film, such as ITO, IZO, GZO, CdO. The method of claim 1, The material for forming the cathode electrode is an organic electroluminescent device, characterized in that formed of a metal thin film such as Au, Ag, Pt, Pd. Forming a seed layer on the substrate, Forming an anode electrode having a high crystallinity in the seed layer; Forming a hole injection layer on the anode; Forming a light emitting layer on the hole injection layer; Forming an electron injection layer on the light emitting layer; A method of manufacturing an organic electroluminescent device, comprising the step of forming a cathode on the electron injection layer. The method of claim 9, A method of manufacturing an electroluminescence display device, further comprising forming a protective film between the seed layer and the substrate. The method of claim 10, The protective film is a method of manufacturing an organic electroluminescent device, characterized in that formed of an insulating material such as silicon nitride. The method of claim 9, The seed layer is a method of manufacturing an organic electroluminescent device, characterized in that formed of YSZ, MgO, ZrO ₂ , ZnO and the like. The method of claim 9, The seed layer is a method of manufacturing an organic electroluminescent device, characterized in that formed of a non-conductive material. The method of claim 9, The material for forming the anode electrode is formed of an oxide thin film of ITO, IZO, GZO, CdO and the like. The method of claim 9, The material for forming the cathode electrode is a method of manufacturing an organic electroluminescent device, characterized in that formed of a metal thin film such as Au, Ag, Pt, Pd.