KR100686340B1 - Organic electroluminescent display device using anode having a metal oxide layer and method for fabricating the same - Google Patents

Abstract

The present invention relates to an organic electroluminescent display device using a lower electrode including a metal oxide layer and a method of manufacturing the same, a substrate; A lower electrode formed of a metal oxide layer on the first metal layer, the second metal layer, and the second metal layer formed on the substrate; An upper electrode formed on the substrate; And an organic layer including at least an organic emission layer formed between the lower electrode and the upper electrode, wherein the first metal is Mo and the second metal layer is Mo-alloy. And by providing a manufacturing method thereof, it is possible to prevent the reflection of external light without using a polarizing plate to reduce the cost, the manufacturing process is simple, and does not use a heavy metal material such as Cr / CrOx used as a conventional light absorption layer An environmentally friendly organic electroluminescent display device can be provided.

Organic electroluminescent device, metal oxide layer, work function, light absorption layer

Description

FIELD OF THE INVENTION Organic electroluminescent device using an anode electrode comprising a metal oxide layer and a method of manufacturing the same

1 is a view schematically showing the structure of an organic electroluminescent display device manufactured according to a conventional embodiment.

2 is a cross-sectional view illustrating a structure and a manufacturing process of an organic electroluminescent display device manufactured according to an embodiment of the present invention.

Figure 3 is a graph showing the results of measuring the work function of molybdenum tungsten (MoW) and molybdenum tungsten oxide (MoWOx) used in one embodiment of the present invention.

[Industrial use]

The present invention relates to an organic electroluminescent device including a lower electrode including a metal oxide layer and a method for manufacturing the same, and more particularly to a metal oxide layer without reflecting external light without a decrease in contrast even without using a polarizing plate. It relates to a lower electrode and a manufacturing method thereof.

[Prior art]

Recently, organic electroluminescent devices have attracted attention as next generation display devices due to their advantages such as thin, wide viewing angle, light weight, small size, fast response speed, and small power consumption, compared to cathode ray tubes (CRTs) and liquid crystal devices (LCDs).

In particular, since the organic EL device has a simple structure of a lower electrode, an organic layer, and a cathode, there is an advantage that the organic EL device can be easily manufactured through a simple manufacturing process. In addition, the organic layer may be composed of several layers depending on the function, and generally consists of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer.

When voltage is applied between the lower electrode and the upper electrode, holes are injected into the organic light emitting layer from the lower electrode, and electrons are injected into the organic light emitting layer from the cathode. The holes and electrons injected into the organic light emitting layer recombine in the organic light emitting layer to generate excitons, and the excitons emit light while transitioning from the excited state to the ground state.

The lower electrode is formed to be reflective, that is, to reflect light, and the cathode is formed to be transmissive, that is, to transmit light, thereby manufacturing an organic EL device emitting light emitted from the organic light emitting layer toward the upper electrode. have.

At this time, as the reflective lower electrode, a conductive material having excellent reflection characteristics and an appropriate work function is suitable, but there is currently no single material that satisfies these characteristics and is applicable. Therefore, the above characteristics are satisfied by forming the reflective lower electrode in a multilayer structure.

1 is a cross-sectional view showing a cross-sectional structure of a conventional active matrix organic field display device.

Referring to FIG. 1, in the insulating substrate 100 including a thin film transistor and a capacitor, the thin film transistor includes a source / drain region formed in a semiconductor layer, a gate electrode (not shown) formed on a gate insulating film, and an interlayer insulating film. And source / drain electrodes (not shown) that are formed on and electrically connected to source / drain regions (not shown), respectively, through contact holes.

Meanwhile, an organic light emitting diode is formed on the insulating substrate 100. The organic light emitting diode is formed on the passivation layer formed on the thin film transistor, the pixel electrode 110 as an anode electrically connected to the drain electrode through the via hole, and the pixel electrode 110 exposed through the opening A. The organic light emitting layer 130 is formed on the () and the upper electrode 140 formed on the organic light emitting layer 190.

The lower electrode 110 sequentially forms an aluminum film 110a and an indium tin oxide (ITO) film 110b on the substrate 100, and then forms a photoresist pattern on the ITO film 110b. The ITO film 110b and the aluminum film 110a are sequentially etched using the photoresist pattern as a mask. As a result, the lower electrode 110 in which the aluminum film 110a and the ITO film 110b are sequentially stacked is formed. The photoresist pattern is then removed using a strip solution.

In addition, the pixel defining layer PDL 120 may be formed to separate and insulate the lower electrodes 110 from each other.

Subsequently, the organic light emitting diode 130 is formed on the lower electrode 110 and the cathode 140 is formed on the organic light emitting layer, thereby manufacturing an organic EL device.

The ITO film 110b of the lower electrode not only has a high work function but is transparent, and the aluminum film 110a is a film having excellent reflection characteristics. Therefore, the lower electrode 110 may not only easily inject holes into the organic light emitting layer, but also efficiently reflect light emitted from the organic light emitting layer.

However, a flat panel display device such as an active matrix organic light emitting display device having a structure as described above is composed of a switching element and various wirings for applying power to the switching element. External light is reflected by the wiring metal material.

For example, external light is reflected by the metal material constituting the gate electrode and the lower electrode of the capacitor, the electrode material constituting the source / drain electrode and the upper electrode of the capacitor, and the electrode material constituting the cathode. It is greatly reduced.

In order to prevent the lowering of the contrast caused by the reflection of external light, an expensive polarizer is conventionally attached to the front of the display device, but this not only increases the manufacturing cost due to the use of the expensive polarizer but also the polarizer itself emits from the organic electroluminescent layer. Since the light is also blocked, there is a problem of lowering the transmittance and lowering the luminance.

In addition, the electrical characteristics may be lowered as the interface characteristics between the aluminum film and the ITO of the lower electrode are lowered.

In addition, there was a method of separately forming a black matrix made of Cr / CrOx or an organic film in a region where TFTs and capacitors are formed. This method requires a separate mask process to form a black matrix, which makes the process complicated. , Cr and Cr / CrOx are heavy metals that can cause environmental problems.

The present invention has been made to solve the problems as described above, an object of the present invention is to form an oxide layer on the lower electrode when forming the organic electroluminescent device to the external light is reflected even without using a polarizing plate contrast (contrast) ) Can be prevented from significantly lowering, and to provide an organic EL device and a method for manufacturing the same that can be manufactured by a simple process.

The present invention to achieve the above object,

The present invention

Board;

A lower electrode formed of a metal oxide layer on the first metal layer, the second metal layer, and the second metal layer formed on the substrate;

An upper electrode formed on the substrate; And

An organic film layer including at least an organic light emitting layer formed between the lower electrode and the upper electrode;
The first metal layer is Mo, and the second metal layer is Mo-alloy to provide an organic electroluminescent device.

In addition, the present invention

Sequentially depositing a first metal layer formed of Mo and a second metal layer formed of Mo-alloy on a substrate on which the thin film transistor is formed;

Completing a lower electrode by forming a metal oxide layer on the stacked second metal layer;

Forming an organic layer including an organic emission layer on the metal oxide layer; And

It provides a method of manufacturing an organic EL device comprising the step of forming an upper electrode on the organic film layer.

Hereinafter, with reference to the accompanying drawings of the present invention will be described in more detail. Like numbers refer to like elements throughout the specification.

2 is a cross-sectional view illustrating a structure and a manufacturing process of an organic electroluminescent display device manufactured according to an embodiment of the present invention.

Referring to FIG. 2, a first metal layer 111 connected to a source / drain electrode (not shown) of a thin film transistor is formed on a substrate 100 on which one or more thin film transistors (not shown) are formed.

Subsequently, it is preferable to use sputtering on the first metal layer 111 on the second metal layer 112 to a thickness of 50 to 2000 mm 3. Since the first metal layer 111 and the second metal layer 112 act as reflective metals, reflection characteristics are deteriorated when they are thin, and contact resistance increases when they are too thick, which is not preferable.

As the first metal layer 111 and the second metal layer 112, a low resistance metal having a low contact resistance is preferably used as the low resistance metal. The first metal layer 111 is Mo, and the second metal layer 112 is Mo. ) Uses Mo-alloy.

The Mo-alloy preferably uses MoW.

Subsequently, a metal oxide layer 113 is formed on the second metal layer 112.

The metal oxide layer 113 may be formed of the same material as the first metal layer 111 or the second metal layer 112, and preferably formed of the same material as the second metal layer 112.

The metal oxide layer 113 is formed of an oxide of Mo or Mo-alloy, preferably an oxide of Mo-alloy, for example, an oxide of MoW.

The metal oxide layer 113 may be manufactured by oxidizing the second metal layer 112 by exposing the substrate 100 on which the second metal layer 112 is formed in an oxygen or oxygen and nitrogen mixed atmosphere. At this time, the exposure time is preferably 20 minutes.

In another embodiment, after the second metal layer 112 is formed, the metal oxide layer 113 is in situ in a mixed atmosphere of oxygen or nitrogen and oxygen in a state where the second metal layer 112 is formed by sputtering. Form in-situ. Subsequently, the lower electrode 110 is completed by forming a photoresist pattern on the metal oxide layer 113, forming the metal oxide layer 113 pattern using the photoresist pattern as a mask, and removing the photoresist. .

Since the metal oxide layer 113 of the lower electrode does not absorb and reflect external light as a light absorbing layer, the contrast is not required even when an independent black matrix layer such as a polarizing plate or Cr / CrOx is formed in the organic EL display device. The fall can be prevented.

In addition, in order to transfer holes to the organic light emitting layer formed in a subsequent process, the work function of the ITO typically used as the lower electrode 110 should not be different from each other, so that the work function of the metal oxide layer 113 is 5.3. eV to about 5.6 eV.

In the present invention, the lower electrode 110 is an anode electrode, the upper electrode 140 is preferably a cathode electrode.

Figure 3 is a graph showing the results of measuring the work function of molybdenum tungsten (MoW) and molybdenum tungsten oxide (MoWOx) used in one embodiment of the present invention.

Referring to FIG. 3, it can be seen that the MoW film has a work function of 4.6 eV, which is an energy in which the number of photoelectrons rapidly increases with light energy. In the case of MoWOx, which is an oxide film of Mo-alloy, the work function is 5.3 eV. You can see that.

On the other hand, the metal oxide film more O ₂ - When a plasma treatment, for example, the MoWOx O ₂ - When a plasma treatment and it can be seen that the work function increases more to 5.6 eV.

Therefore, in one embodiment of the present invention, after the metal oxide layer 113 is formed, it is preferable to further oxidize with O ₂ -plasma.

In addition, since the charge is transferred by the tunneling phenomenon between the metal oxide layer 113 and the organic light emitting layer 130 formed in a subsequent process, the metal oxide layer 113 is preferably formed to a thickness of 50 Å or less, In order to appropriately perform the role of the light absorbing layer, it is preferable to have a thickness of 10 GPa or more.

Subsequently, a pixel defined layer 120 may be formed on the lower electrode 110. The pixel definition layer 120 is stacked on the entire surface of the substrate, and then exposed using a photomask to expose a region where the metal oxide layer is formed among the lower electrodes, and define a pixel on the region where the second metal layer is formed. The opening A is formed by patterning the film to remain.

The light emitting area of the organic electroluminescent display is defined by the opening A. FIG. The pixel definition layer 120 may be formed of one selected from the group consisting of benzocyclobutene (BCB), acrylic photoresist, phenolic photoresist, and polyimide photoresist.

Subsequently, an organic layer 130 including at least an organic emission layer is formed on the opening.

As the light emitting layer, both a polymer and a low molecular material may be used, and a material used as a conventional light emitting layer forming material may be used.

In addition, the light emitting layer may be formed using a light emitting layer forming method commonly used according to the nature of the material used. That is, a conventional light emitting layer forming method such as spin coating, vacuum deposition, and laser thermal transfer method can be used.

The organic layer 130 may further include one or more layers selected from the group consisting of a hole injection layer, a hole transport layer, a hole suppression layer, an electron transport layer, and an electron injection layer, according to device characteristics.

Subsequently, an upper electrode 140 is formed on the organic layer 130. The upper electrode 140 is formed using one metal selected from the group consisting of Mg, Ca, Al, Ag, Ba, and alloys thereof, but is preferably formed to a thickness sufficient to transmit light. .

As a result, an organic light emitting display device including the lower electrode 110 including the metal oxide layer having the light absorption function, the upper electrode 140 and the organic layer 130 interposed therebetween can be manufactured. have.

The organic electroluminescent display device prevents light from entering the inside of the device from being absorbed by the metal oxide layer of the lower electrode to be reflected by the metal of the conventional lower electrode, thereby preventing the lowering of the contrast.

As described above, in the present invention, by introducing a metal oxide layer having a high work function while absorbing external light into the lower electrode, reflection of external light can be prevented without using a polarizing plate, thereby reducing costs and simplifying the manufacturing process. Since a heavy metal material such as Cr / CrOx used as a conventional light absorption layer is not used, an environment-friendly organic electroluminescent display device can be provided.

Claims (19)

Board; A lower electrode formed of a metal oxide layer on the first metal layer, the second metal layer, and the second metal layer formed on the substrate; An upper electrode formed on the substrate; And An organic film layer including at least an organic emission layer formed between the lower electrode and the upper electrode, And wherein the first metal is Mo and the second metal layer is Mo-alloy. delete The method of claim 1, The alloy of Mo is MoW organic electroluminescent display device. The method of claim 1, The metal oxide layer is an organic electroluminescent display device formed of an oxide of Mo or Mo-alloy. The method of claim 4, wherein The Mo-alloy is MoW organic electroluminescent display device. The method of claim 1, The thickness of the metal oxide layer is 10 to 50 kPa organic electroluminescent display device. The method of claim 1, The metal oxide layer absorbs external light and has a work function of 5.3 eV to 5.6 eV. The method of claim 1, And the lower electrode is positioned closer to the substrate than the upper electrode. The method of claim 1, And the upper electrode is made of one metal selected from the group consisting of Mg, Ca, Al, Ag, Ba, and alloys thereof. The method of claim 1, The metal oxide layer is O ₂ -plasma treated organic electroluminescent display device. Sequentially depositing a first metal layer formed of Mo and a second metal layer formed of Mo-alloy on a substrate on which the thin film transistor is formed; Completing a lower electrode by forming a metal oxide layer on the stacked second metal layer; Forming an organic layer including an organic emission layer on the metal oxide layer; And And forming an upper electrode on the organic layer. delete The method of claim 11, The alloy of Mo is MoW manufacturing method of an organic electroluminescent display device. The method of claim 11, The metal oxide layer is a method of manufacturing an organic electroluminescent display device is an oxide of Mo or Mo-alloy. The method of claim 11, And the metal oxide layer is formed by exposing the second metal layer to an oxygen atmosphere and oxidizing the same. The method of claim 11, The metal oxide layer is a method of manufacturing an organic electroluminescent display device which is performed in situ using sputtering on the second metal layer. The method of claim 16,  The metal and the second metal layer of the metal oxide layer is the same metal manufacturing method of the organic electroluminescent display device. The method of claim 11, The thickness of the metal oxide layer is a method of manufacturing an organic electroluminescent display device of 10 to 50 kPa. The method of claim 11, And forming a metal oxide layer and performing O ₂ -plasma treatment on the metal oxide layer.

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