KR100855487B1 - Light Emitting Device - Google Patents

Abstract

The present invention is a substrate; A first conductive layer disposed on the substrate, the first conductive layer including a first conductive layer, a second conductive layer, and a reaction prevention layer formed between the first conductive layer and the second conductive layer to a thickness in the range of 0.1 to 5 nm to block the movement of oxygen; electrode; An emission layer including an organic material positioned on the first electrode; And a second electrode on the light emitting layer, wherein the reaction prevention layer includes at least one metal selected from the group consisting of Cr, Cr alloy, Mo, Mo alloy, Ti, and Ti alloy, and the first conductive layer is Al, Al. Alloys, Ag, Ag alloys, including at least one metal selected from the group, the second conductive layer has a light transmittance, the first electrode has an optical reflectivity of 60 to 90%, the second conductive layer is a first Provided is an electroluminescent device characterized in that the work function of the electrode is adjusted to be relatively lower than the work function of the second electrode.

Electroluminescent device, work function

Description

Light Emitting Device

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

FIG. 2 is an enlarged view of a portion A of FIG. 1; FIG.

3A to 3E are graphs showing experimental data on reflectance of the electroluminescent device according to the first embodiment of the present invention.

* Description of the main parts of the drawings *

100 electroluminescent device 110 substrate

120: first electrode 130: first charge injection / transport layer

140: light emitting layer 150: second charge injection / transport layer

160: second electrode

The present invention relates to an electroluminescent device.

The electroluminescent device injects electrons and holes into the light emitting layer from an electron injection electrode and a hole injection electrode, respectively, and excitons of the injected electrons and holes combine from the excited state. It is a self-luminous device that emits light when it falls to the ground state.

In addition, the electroluminescent device can be driven at a low voltage and has advantages such as thinness. The electroluminescent device is attracting attention as a next-generation display that can solve the disadvantages pointed out as a problem in the conventional liquid crystal display because of its wide viewing angle and fast response speed.

The electroluminescent device is classified into a top-emitting LED that emits light in a direction opposite to the substrate and a bottom-emitting LED that emits toward the substrate, depending on the light emitting method.

In the conventional electroluminescent device, a first electrode is formed of at least one layer on a substrate, and at least one charge injection / transport layer and a light emitting layer are stacked on the first electrode to form a light emitting part. In addition, a second electrode was formed on the light emitting portion.

In the structure described above, since the first electrode had a reflective characteristic, it was formed of a metal series and at least one adjusting layer for adjusting the work function of the first electrode was required for more efficient light emission.

Specifically, a conductive layer containing any one or more of a metal having good reflectance, for example, Al or Al alloy, was formed on the substrate. An insulating film for patterning the light emitting portion was formed on the conductive layer, and an adjustment layer for adjusting the work function was formed on the patterned insulating film.

At this time, the adjustment layer should be formed of, for example, ITO or IZO since it should be a conductive layer having light transmittance.

Curing process had to be performed in the process of forming the above adjustment layer, and after the curing process, a large number of defects occurred mainly on the region where the conductive layer and the adjustment layer were laminated.

The defect mentioned above was caused by the diffusion and compounding reaction between the conductive layer of the first electrode and the work function adjustment layer. For example, oxygen is moved from ITO, which is the work function adjusting layer of the first electrode, to Al, which is the main conductive layer of the first electrode, and a large number of defects are caused by the aggregation of In and Sn separated from oxygen. Have occurred.

The occurrence of such defects caused problems of dark spots on the display and partial luminance non-uniformity in the electroluminescent device, thereby lowering the yield and reliability of the device.

An object of the present invention is to provide an electroluminescent device which can solve the above problems and improve production yield and reliability.

The present invention to achieve this object is a substrate; A first conductive layer disposed on the substrate, the first conductive layer including a first conductive layer, a second conductive layer, and a reaction prevention layer formed between the first conductive layer and the second conductive layer to a thickness in the range of 0.1 to 5 nm to block the movement of oxygen; electrode; An emission layer including an organic material positioned on the first electrode; And a second electrode on the light emitting layer, wherein the reaction prevention layer includes at least one metal selected from the group consisting of Cr, Cr alloy, Mo, Mo alloy, Ti, and Ti alloy, and the first conductive layer is Al, Al. Alloys, Ag, Ag alloys, including at least one metal selected from the group, the second conductive layer has a light transmittance, the first electrode has an optical reflectivity of 60 to 90%, the second conductive layer is a first Provided is an electroluminescent device characterized in that the work function of the electrode is adjusted to be relatively lower than the work function of the second electrode.

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

1 is a cross-sectional view illustrating a structure of an electroluminescent device according to a first embodiment of the present invention, and FIG. 2 is a partially enlarged view of region A on FIG. 1.

Referring to FIG. 1, in the electroluminescent device 100 according to the first embodiment of the present invention, a first electrode 120 is formed on a substrate 110.

The emission layer 140 and the second electrode 160 are formed on the first electrode 120. In addition, a first charge injection / transport layer 130 and a second charge injection / transport layer 150 may be formed between the emission layer 140 and the first and second electrodes 120 and 160 to facilitate the transfer of charge. have. For example, when the first electrode 120 is an anode and the second electrode 160 is a cathode, the first charge injection / transport layer 130 formed between the first electrode 120 and the light emitting layer 140 may be It serves to facilitate the hole transfer from the first electrode 120 to the light emitting layer 140, the second charge injection / transport layer 150 formed between the light emitting layer 140 and the second electrode 160 is a second It serves to facilitate the transfer of electrons from the electrode 160 to the light emitting layer 140.

In the electroluminescent device 100 according to the first embodiment of the present invention as described above, the first electrode 120 should serve to reflect light according to the light emitting direction of the device 100.

Referring to FIG. 2, which shows an enlarged structure of the first electrode 120, the first conductive layer 122 is formed on the substrate 110 by Al, which is a metal having good light reflection characteristics. In this case, the first conductive layer 122 may be formed to have a thickness in the range of 50 to 500 nm so that the first electrode 120 has sufficient conductivity and reflectance (optical reflectance in the range of 80 to 90%).

Although the first conductive layer 122 is formed of Al, for example, the material of the first conductive layer 122 included in the first electrode 120 of the electroluminescent device 100 according to the present invention. Is not limited to Al, and any conductive material capable of optically reflecting in the range of 80 to 90% including Ag is applicable.

The reaction prevention layer 124 and the second conductive layer 126 are formed on the first conductive layer 122.

The reaction prevention layer 124 should be capable of preventing diffusion and compounding reaction between the second conductive layer 126 and the first conductive layer 122 positioned on the first conductive layer 122, and for the luminous efficiency of the device. It must have sufficient light transmittance and is formed to a thickness in the range of 0.1 to 5 nm. In addition, when the first electrode 120 is formed of an anode, since the second conductive layer 126 is mainly formed of a material such as ITO or IZO, the reaction prevention layer 124 should be able to block the movement of oxygen. Accordingly, the reaction prevention layer 124 may include one or more metals selected from the group consisting of Cr, Cr alloys, Ti, and Ti alloys, but the material of the reaction prevention layer 124 is not limited thereto.

On the other hand, the second conductive layer 126 should be formed of a light transmitting conductive material, and should be able to adjust the work function of the first electrode 120 to a predetermined range. For example, when the first electrode 120 is formed as an anode, the work function of the first electrode 120 should be adjusted to 4.5 ev or more. Accordingly, the second conductive layer 126 may be formed of any one of transparent conductive oxide (TCO) including ITO, IZO, and ITZO, but the material of the second conductive layer 126 is not limited thereto.

The structure of the first electrode 120 of the electroluminescent device 100 according to the first embodiment of the present invention as described above reacts the diffusion and compounding reaction between the first conductive layer 122 and the second conductive layer 124. Since the prevention layer 124 prevents the occurrence of various types of defects formed on the first electrode 120. Accordingly, the electroluminescent device 100 according to the first embodiment of the present invention can prevent dark spots or partial luminance defects on the display.

3A to 3E are graphs showing experimental data on reflectances of the electroluminescent devices according to the second to sixth embodiments of the present invention.

Hereinafter, the graphs of FIGS. 3A to 3E are data representing a change in light reflectance of the substrate on which the first electrode is formed according to a change in thickness of the reaction prevention film included in the first electrode on the substrate. Specifically, a first conductive layer (ex; Al) serving as a reflective layer in the first electrode, a second conductive layer (ex: ITO) and a first conductive layer serving as a work function adjusting layer in the first electrode (ex; Al) and the second conductive layer (ex; ITO) visible light region (X coordinates) with respect to the first electrode on the substrate formed by laminating a reaction prevention film (ex; Cr) to prevent the movement of oxygen It is the data expressing the reflectance (Y coordinate x 100%) of the 1st electrode measured in the 400-700 nm wavelength range as a percentage.

Referring to FIG. 3A, in the second embodiment of the present invention, an Al layer is formed to a thickness of 100 nm on a substrate, a Cr film is formed to a thickness of 0.1 nm on an Al layer, and ITO is formed to a thickness of 10 nm on a Cr film. Is formed.

As shown in FIG. 3A, the reflectance of the substrate on which the first electrode is formed according to the second embodiment of the present invention exhibits an efficiency in the range of 85 to 90%.

Referring to FIG. 3B, in the third embodiment of the present invention, an Al layer is formed to a thickness of 100 nm on a substrate, a Cr film is formed to a thickness of 1 nm on an Al layer, and ITO is formed to a thickness of 10 nm on a Cr film. Is formed.

As shown in FIG. 3B, the reflectance of the substrate on which the first electrode is formed according to the third embodiment of the present invention is in the range of 78 to 85%.

Referring to FIG. 3C, in the fourth embodiment of the present invention, an Al layer is formed to a thickness of 100 nm on a substrate, a Cr film is formed to a thickness of 2 nm on an Al layer, and ITO is formed to a thickness of 10 nm on a Cr film. Is formed.

As shown in FIG. 3C, the reflectance of the substrate on which the first electrode is formed according to the fourth embodiment of the present invention exhibits an efficiency in the range of 75 to 82%.

Referring to FIG. 3D, in the fifth embodiment of the present invention, an Al layer is formed to a thickness of 100 nm on the substrate, a Cr film is formed to a thickness of 3 nm on the Al layer, and ITO is formed to a thickness of 10 nm on the Cr film. Is formed.

As shown in FIG. 3D, the reflectance of the substrate on which the first electrode is formed according to the fifth embodiment of the present invention exhibits an efficiency in the range of 75 to 82%.

 Referring to FIG. 3E, in the sixth embodiment of the present invention, an Al layer is formed to a thickness of 100 nm on a substrate, a Cr film is formed to a thickness of 5 nm on an Al layer, and ITO is formed to a thickness of 10 nm on a Cr film. Is formed.

As shown in FIG. 3E, the reflectance of the substrate on which the first electrode is formed according to the sixth embodiment of the present invention is in the range of 64 to 78%.

As described above, when the reflectance of the first electrode on the substrate according to the second to sixth embodiments of the present invention is changed, the reflectance of the first electrode on the substrate is 60 to 90 when the thickness of the reaction prevention film is formed within the range of 0.1 to 5 nm. It can be seen that it represents the% range efficiency.

The critical significance of the thickness range of the reaction prevention film based on various embodiments of the present invention is that the reaction prevention film should be formed to a thickness of 0.1 nm or more, for example, oxygen diffusion and compounding reactions between the first conductive layer and the second conductive layer, for example, oxygen. It is possible to sufficiently block the movement of, and the reaction prevention film may be formed to a thickness of 5 nm or less to satisfy the effective light extraction efficiency range of the device.

Therefore, for sufficient light extraction efficiency of the electroluminescent device according to the present invention, the reflectance of the first electrode on the substrate should be adjusted within the range of 60 to 90%, and thus the thickness of the reaction prevention film should be formed within the range of 0.1 to 5 nm. It can be seen.

The electroluminescent device according to the first embodiment of the present invention has been described as an example in which a charge injection / transport layer is interposed between the electrode and the light emitting layer, but the structure of the electroluminescent device according to the present invention is not limited thereto. The injection / transport layer may not be present.

The light emitting layer of the electroluminescent device according to various embodiments of the present invention may include any one or more of an organic material, an inorganic material.

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, the above-described embodiments are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the above description, and the meaning and scope of the claims are as follows. And all changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

As described above, the present invention can provide an electroluminescent device capable of improving production yield and reliability.

Claims (10)

Board; Located on the substrate and including a first conductive layer, a second conductive layer and a reaction prevention layer formed between the first conductive layer and the second conductive layer to a thickness in the range of 0.1 to 5nm to block the movement of oxygen A first electrode; An emission layer including an organic material positioned on the first electrode; And Including a second electrode located on the light emitting layer, The reaction prevention layer comprises at least one metal selected from the group consisting of Cr, Cr alloy, Mo, Mo alloy, Ti, Ti alloy, The first conductive layer comprises at least one metal selected from the group consisting of Al, Al alloys, Ag, Ag alloy, the second conductive layer has a light transmittance, The first electrode optically has a reflectance of 60 to 90%, And the second conductive layer adjusts a work function of the first electrode to be lower than a work function of the second electrode. delete delete delete delete delete delete delete delete delete

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