KR101074924B1 - top emission type Organic Electro luminescence Device and fabrication method thereof - Google Patents

Abstract

An organic light emitting display device according to the present invention includes a first substrate and a second substrate disposed to face each other; A thin film transistor formed on each of the sub-pixels on the first substrate; A first electrode connected to the thin film transistor and formed on the first substrate; An organic light emitting layer and a second electrode sequentially formed on the first electrode; A seal pattern formed at an edge of the substrate for bonding the first substrate and the second substrate is included, wherein the first electrode is formed of a dual structure of a metal layer having a high work function and a metal layer having a high reflectance. The metal layer having a high work function is characterized by being formed in several tens of kPa or less.

According to the present invention, the first electrode is formed of a dual structure of a metal layer having a high work function and a metal layer having a high reflectance, and the thickness of the metal layer having the high work function is maintained at several tens of micrometers or less, thereby providing an organic electroluminescence. There is an advantage that contributes to increased efficiency and longer life of the device.

Description

Top emission type organic electroluminescent device and fabrication method thereof

1 is a schematic cross-sectional view of a conventional bottom emission type organic electroluminescent device.

Figure 2 is a schematic cross-sectional view of a conventional top-emitting organic electroluminescent device.

Figure 3 is a schematic cross-sectional view of an organic light emitting device of the top emission method according to an embodiment of the present invention.

4 is a cross-sectional view of the first electrode shown in FIG. 3.

FIG. 5 is an enlarged cross-sectional view of one subpixel area of the organic light emitting display device shown in FIG. 3; FIG.

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

120: first electrode 122: metal layer having a high work function

124: highly reflective metal layer 140: organic light emitting layer

160: second electrode

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device having a top light emitting method and a method of manufacturing the same.

In the field of flat panel displays (FPDs), a liquid crystal display device (LCD) has been the most noticeable display device until now, but the liquid crystal display device is a light receiving device, not a light emitting device. Due to technical limitations in brightness, contrast, viewing angle, and large area, development of new flat panel display devices that can overcome these disadvantages is being actively developed.

The organic electroluminescent device, which is one of the new flat panel displays, has a better viewing angle, contrast, and the like than the liquid crystal display because of its self-luminous type, and is light and thin because it does not require a backlight, and is advantageous in terms of power consumption.

In addition, since it is possible to drive a DC low voltage, the response speed is fast, and all solid, it is strong against external shock and has a wide range of use temperature. In particular, unlike the liquid crystal display device or the plasma display panel (PDP), all of the deposition and encapsulation equipments are manufactured in the organic electroluminescent device manufacturing process. Therefore, the process is very simple.

In addition, when the organic light emitting diode is driven in an active matrix method having a thin film transistor as a switching element for each pixel, the same luminance is displayed even when a low current is applied, and thus, low power consumption, high definition, and large size can be obtained.

1 is a schematic cross-sectional view of a conventional bottom emission type organic electroluminescent device.                         

As illustrated, the first and second substrates 10 and 30 are disposed to face each other, and the edge portions of the first and second substrates 10 and 30 are sealed by a seal pattern 40. The thin film transistor T is formed on the transparent substrate 1 of the first substrate 10 for each subpixel, and is connected to the thin film transistor T to form the first electrode 12. Red, green, and blue colors are disposed on the transistor T and the first electrode 12 to be connected to the thin film transistor T so as to correspond to the first electrode 12. An organic light emitting layer 14 including a light emitting material is formed, and a second electrode 16 is formed on the organic light emitting layer 14.

The first and second electrodes 12 and 16 serve to apply an electric field to the organic light emitting layer 14.

The second electrode 16 and the second substrate 30 are spaced apart from each other by the seal pattern 40 described above, and although not shown in the drawing, the inner surface of the second substrate 30 may be formed from the outside. A moisture absorbent (not shown) that absorbs the incoming moisture and a semipermeable tape (not shown) for adhesion between the moisture absorbent and the second substrate 30 are included.

In the bottom emission type structure, the first electrode 12 is formed of an anode and the second electrode 16 is formed of a cathode.

Accordingly, the first electrode 12 is selected from a transparent conductive material, and the second electrode 16 is selected from a metal material having a low work function. Under these conditions, the organic light emitting layer 14 is formed of the first electrode 12. A hole injection layer 14a, a hole transporting layer 14b, a hole transporting layer 14b, an emission layer 14c, and an electron transporting layer 14d are formed in this order.

For example, it is preferable that ITO is used as the transparent electrode as the first electrode 12, and a metal material having a low work function, such as Al, Mg, or Ca, is used as the second electrode 16.

In this case, the light emitting layer 14c has a structure in which light emitting materials for implementing red, green, and blue colors are sequentially disposed for each subpixel.

However, the conventional organic light emitting diode of the conventional bottom emission method has a disadvantage in that it is difficult to apply to a high resolution product due to the limitation of the aperture ratio.

2 is a schematic cross-sectional view of a conventional top-emitting organic light emitting display device.

Referring to FIG. 2, in the conventional top emission type organic light emitting diode, the direction in which light generated in the organic light emitting layer 24 emits light is lower than in the bottom when compared with the bottom emission type organic light emitting diode shown in FIG. 1. There is a difference in that the first electrode 22 and the second electrode 26 is different from the lower light emitting method for this purpose.

For example, when the first electrode 22 is formed of an anode and the second electrode 26 is formed of a cathode, the first electrode 22 may emit light generated by the organic light emitting layer 24. The second electrode 26 should reflect the light generated by the organic light emitting layer 24.

Therefore, when ITO is used as the first electrode 22, a reflector 28 should be further provided below the second electrode 26, and the second electrode 26 should be formed thin enough to transmit light.

However, in the conventional upper light emitting method, the reflectance of the first electrode 22 and the reflector 28 is weak, so that the driving voltage applied to the first electrode 22 must be increased to obtain high efficiency. There is this.

Increasing the driving voltage as a result causes a problem of shortening the lifespan of the organic light emitting display device, and causes a poor image quality such as a dark spot.

In the organic light emitting device of the top emission type, the first electrode is formed of a double structure of a metal layer having a high work function and a metal layer having a high reflectance, and the thickness of the metal layer having a high work function is several tens of micrometers or less. It is an object of the present invention to provide an organic light emitting display device and a method for manufacturing the organic light emitting display device having a top light emitting method, which contributes to an increase in efficiency and lifespan of the organic light emitting device.

In order to achieve the above object, an organic light emitting display device according to the present invention includes a first substrate and a second substrate disposed to face each other; A thin film transistor formed on each of the sub-pixels on the first substrate; A first electrode connected to the thin film transistor and formed on the first substrate; An organic light emitting layer and a second electrode sequentially formed on the first electrode; A seal pattern formed on the edge of the substrate for bonding the first substrate and the second substrate is included, the first electrode is formed of a dual structure of a metal layer having a high work function and a metal layer having a high reflectance, The thickness of the metal layer having the high work function is characterized by being formed in several tens of kPa or less.

Here, the first electrode is an anode (anode), the second electrode is a cathode (cathode), the second electrode is characterized in that composed of a transparent electrode so that the light generated in the organic electroluminescent layer can be transmitted.

In addition, the metal layer having a high work function is made of one of Cr, C, a-Si, Ni, Pd, Au, Pt, Pb, ITO, IZO, is formed to a thickness of 10 ~ 50Å of the metal layer The metal layer having high reflectance may be made of one of AlNd, Al, and Mo.

In addition, the organic light emitting layer is a stacked structure in order from the layer in contact with the first electrode, a hole injection layer (hole injection layer), a hole transporting layer (hole transporting layer), an emission layer (electron transporting layer) in order Has

In addition, the manufacturing method of the top emission type organic light emitting device according to the present invention comprises the steps of: forming a thin film transistor on a first substrate in subpixel units; Forming a first electrode to be electrically connected to the thin film transistor; Sequentially forming an organic light emitting layer and a second electrode on the first electrode; And bonding the second substrate, which is a transparent substrate, to a position opposite to the first substrate, wherein the first electrode is formed of a double structure of a metal layer having a high work function and a metal layer having a high reflectance, and the high work function Characterized in that the thickness of the metal layer having a tens of kPa or less.

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

FIG. 3 is a schematic cross-sectional view of an organic light emitting display device of a top emission type according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view of a first electrode shown in FIG. 3. 5 is an enlarged cross-sectional view of one subpixel area of the organic light emitting display device illustrated in FIG. 3.

Referring to FIGS. 3 to 5, the structure and manufacturing method of the organic light emitting display device according to the present invention are as follows.

As shown in FIG. 3, the first and second substrates 100 and 300 are disposed to face each other, and edge portions of the first and second substrates 100 and 300 are sealed by a seal pattern 400. In the structure, the thin film transistor T is formed on each of the subpixels on the substrate 10 of the first substrate 100.

In addition, the first electrode 120 is formed to be connected to the thin film transistor T, and the first electrode 120 is connected to the thin film transistor T on the thin film transistor T and the first electrode 120. The organic light emitting layer 140 including red, green, and blue light emitting materials disposed to correspond to each other is formed, and the second electrode is disposed on the organic light emitting layer 140. 160 is formed.

The first and second electrodes 120 and 160 serve to apply an electric field to the organic light emitting layer 140.                     

As shown in FIG. 4, the first electrode 120 has a double structure of a metal layer 122 having a high work function and a metal layer 124 having a high reflectance, and has a metal layer having the high work function ( It is characterized in that it is configured to maintain the thickness of 122).

Through this, the light generated in the organic light emitting layer 140 and emitted toward the first electrode 120 can be reflected at maximum efficiency, thereby driving the organic light emitting diode without applying a high driving voltage. It contributes to extending the life of the organic light emitting display device, and can overcome the problem of poor image quality such as dark spots. The second electrode 160 and the second substrate 300 are spaced apart from each other by the aforementioned seal pattern 400, and although not shown in the drawing, the inner surface of the second substrate 300 may be disposed from the outside. A moisture absorbent that absorbs the incoming moisture is included.

In the case of the present invention, it is preferable to use a coating material of a transparent material because the hygroscopic agent is a top emission method.

In the exemplary embodiment of the present invention, the first electrode 120 is configured as an anode, and the second electrode 160 is configured as a cathode.

Accordingly, the organic light emitting layer 140 may include a hole injection layer 140a, a hole transporting layer 140b, an emission layer 140c, and an electron from a layer in contact with the first electrode 120. It forms a stacked structure in order of the transport layer (140d; electron transporting layer).

In this case, the light emitting layer 140c has a structure in which light emitting materials for implementing red, green, and blue colors are sequentially disposed for each subpixel.                     

However, since the second electrode 160 has a role of transmitting light, a metal such as Al, Mg, Ca, etc. having a low work function should be formed thin enough to transmit light.

Alternatively, the second electrode 160 may be formed of a double layer of Al of about 10 GPa and ITO of about 1000 GPa.

In addition, as shown in FIG. 4, the first electrode 120 is formed in a double structure of a metal layer 122 having a high work function and a metal layer 124 having a high reflectance, and has a metal layer 122 having the high work function. It is characterized in that it is configured to maintain the thickness of several).

Here, the metal layer 122 having the high work function may be made of one of Cr, C, a-Si, Ni, Pd, Au, Pt, Pb, ITO, IZO, and the metal layer 122 It is preferable to form the thickness at 10-50 microseconds.

In addition, the highly reflective metal layer 124 is preferably made of one of AlNd, Al, Mo.

The detailed structure of the thin film transistor T, the first electrode 120, the organic electroluminescent layer 140, and the second electrode 160 described above with reference to FIG. 3 will be described with reference to FIG. 4.

As illustrated, the semiconductor layer 62, the gate electrode 68, the source and drain electrodes 80 and 82 are sequentially formed on the transparent substrate 10 to form a thin film transistor region, and the source and drain electrodes 80, 82 is connected to an organic light emitting diode E formed of a power electrode 72 and a first electrode 120, an organic light emitting layer 140, and a second electrode 160 formed in a power supply line (not shown). have.                     

In addition, the capacitor electrode 64 is positioned with an insulator interposed between the power electrode 72 and a lower portion of the power electrode 72, and the corresponding region forms a storage capacitor region.

Elements formed in the thin film transistor region and the storage capacitor region other than the organic light emitting diode E form the array element A.

The organic light emitting diode E includes a first electrode 120 and a second electrode 160 facing each other with the organic light emitting layer 140 interposed therebetween. The organic light emitting diode E is positioned in a light emitting area for emitting self-emitting light to the outside.

In the exemplary embodiment of the present invention, as described above, the first electrode 120 is formed of a dual structure of the metal layer 122 having a high work function and the metal layer 124 having a high reflectance.
Here, each of the metal layer 122 having a high work function and the metal layer 124 having a high reflectance is in direct contact with the drain electrode 82 of the thin film transistor.

As described above, when the first electrode is formed of a double layer having the structure described by the leaf structure of the top emission type organic light emitting device, the light emitted from the organic light emitting layer and emitted toward the first electrode may be generated. It can be reflected at maximum efficiency, and it is possible to drive the organic light emitting device without applying a high driving voltage, thereby contributing to extending the life of the organic light emitting device, and to solve the problem of poor image quality such as dark spots. It will be able to overcome.

According to the present invention, the first electrode is formed of a double structure of a metal layer having a high work function and a metal layer having high reflectance, and the thickness of the metal layer having the high work function is maintained at several tens of micrometers or less, thereby providing organic electroluminescence. There is an advantage that contributes to increased efficiency and longer life of the device.

Claims (10)

A first substrate and a second substrate disposed to face each other; A thin film transistor formed on each of the sub-pixels on the first substrate; A first electrode connected to the thin film transistor and formed on the first substrate; An organic light emitting layer and a second electrode sequentially formed on the first electrode; A seal pattern formed at an edge of the substrate for bonding the first substrate and the second substrate is included, The first electrode is formed of a double structure of a metal layer having a high work function and a metal layer having a high reflectance, and a thickness of the metal layer having the high work function is several tens of Pa or less, And each of the metal layer having the high work function and the metal layer having the high reflectance are in direct contact with a drain electrode of the thin film transistor. The method of claim 1, The first electrode is an anode (anode), the second electrode is a cathode (cathode), the second electrode is a top emission type, characterized in that composed of a transmissive electrode to transmit light generated in the organic electroluminescent layer Organic electroluminescent device. The method of claim 1, The metal layer having a high work function is an organic electroluminescent device of the top emission type, characterized in that composed of one of Cr, C, a-Si, Ni, Pd, Au, Pt, Pb, ITO, IZO. The method of claim 3, The organic light emitting device of the upper light emitting method, characterized in that formed in a thickness of 10 ~ 50Å of the metal layer. The method of claim 1, The high reflectance metal layer is an organic light emitting device of the top emission type, characterized in that composed of one of AlNd, Al, Mo. The method of claim 1, The organic light emitting layer has a structure in which a layer in contact with the first electrode is laminated in the order of a hole injection layer, a hole transporting layer, an emission layer, and an electron transporting layer. An organic light emitting display device characterized in that. Forming a thin film transistor on a first substrate in units of subpixels; Forming a first electrode to be electrically connected to the thin film transistor; Sequentially forming an organic light emitting layer and a second electrode on the first electrode; Bonding a second substrate, which is a transparent substrate, to a position opposite to the first substrate, The first electrode is formed of a double structure of a metal layer having a high work function and a metal layer having a high reflectance, and a thickness of the metal layer having the high work function is several tens of Pa or less, And each of the metal layer having the high work function and the metal layer having the high reflectance are in direct contact with a drain electrode of the thin film transistor. The method of claim 7, wherein The first electrode is an anode (anode), the second electrode is a cathode (cathode), the second electrode is a top emission type, characterized in that composed of a transmissive electrode to transmit light generated in the organic electroluminescent layer Organic electroluminescent device manufacturing method. The method of claim 7, wherein The metal layer having a high work function is made of one of Cr, C, a-Si, Ni, Pd, Au, Pt, Pb, ITO, IZO, characterized in that formed of a thickness of 10 ~ 50Å of the metal layer The organic light emitting device manufacturing method of the top light emitting method. The method of claim 7, wherein The metal layer having a high reflectance is a method of manufacturing an organic light emitting display device of the upper light emitting method, characterized in that composed of one of AlNd, Al, Mo.

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