KR100590259B1 - Top Emission OLED using Assistant Electrode to prevent IR drop and fabricating the same - Google Patents

Abstract

The present invention includes a lower electrode formed on an insulating substrate having a thin film transistor and electrically connected to the thin film transistor; An auxiliary electrode formed on the same layer as the lower electrode; A pixel defining layer which is not formed on the auxiliary electrode and has an opening formed only at an edge of the lower electrode to expose a portion of the lower electrode; An organic film formed on the opening; And an upper electrode formed on the entire surface of the insulating substrate and electrically connected to the auxiliary electrode, wherein the taper angle of the edge portion of the auxiliary electrode is 90 ° or more and less than 180 °.

Organic electroluminescent display, top emission, auxiliary electrode, voltage drop, taper angle

Description

Top-emitting OLED using Assistant Electrode to prevent IR drop and fabricating the same}

1 is a cross-sectional view illustrating a conventional top-emitting organic light emitting display device.

2 is a cross-sectional view illustrating a top-emitting organic light emitting display device according to a first embodiment of the present invention.

3A to 3C are cross-sectional views illustrating a top-emitting organic light emitting display device according to a first embodiment of the present invention.

4 is a cross-sectional view of an organic light emitting display device limited to an upper electrode voltage drop preventing auxiliary electrode according to an exemplary embodiment of the present invention.

5A to 5D are planar views illustrating an organic light emitting display device in which an auxiliary electrode is formed according to an exemplary embodiment of the present invention.

(Explanation of symbols for main parts of drawing)

300; Insulating substrate 310; Buffer layer

320; Active layer 330; Gate insulating film

341; Gate electrode 347; Capacitor Bottom Electrode

350; Interlayer insulating films 351 and 355; Contact hall

361, 365; Source / drain electrodes 367; Capacitor Top Electrode

370; Protective film 375; Via Hall

380; Lower electrode 383; Auxiliary electrode

385; A pixel defining layer 389; Opening

390; Organic film 395; Upper electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display device and a method of manufacturing the same. More particularly, a top-emitting organic light emitting display device which can be enlarged by preventing a voltage drop of a cathode electrode by using an auxiliary electrode for preventing a voltage drop of an upper electrode, and a method thereof It relates to a manufacturing method.

In general, in a top emission active matrix organic electroluminescent display (AMOLED), a transparent cathode electrode is used to emit light toward the encapsulation substrate.

Generally, the transparent cathode electrode is mainly made of a transparent conductive material such as ITO or IZO, but in order to function as a cathode electrode, a thin work material (low work function) is deposited on the side in contact with the organic film to form a semi-transparent layer. A metal film is formed and a thick ITO or IZO is deposited on the transflective metal film.

In the above process, since the ITO or IZO is formed after the organic film is formed, it is formed by low temperature deposition in order to minimize the damage of the organic film by heat or plasma (plasma), the film quality is bad, the specific resistance is high.

However, the high resistivity of the cathode does not mean that the same cathode voltage is applied to each pixel position, but a voltage difference occurs in a region near and far from the region where power is input due to a voltage drop (IR drop). Unevenness of image characteristics can be caused, and power consumption rises.

In addition, due to the voltage drop phenomenon, there is a problem that it is difficult to apply to the medium-large top-emitting active matrix organic electroluminescent display (AMOLED).

In order to solve the above problem, shoji terada et al. Introduced a method of forming an auxiliary electrode for preventing an upper electrode voltage drop on the pixel defining layer 185 in 54.5L of SID2003.

Hereinafter, a conventional top emission organic light emitting display device will be described with reference to the accompanying drawings.

FIG. 1 illustrates a cross-sectional structure of a conventional top emission organic light emitting display device, and is limited to a portion corresponding to one thin film transistor, a pixel electrode, and a capacitor.

Referring to FIG. 1, a buffer layer 110 is formed on an insulating substrate 100, an active layer 120 having source / drain regions 121 and 125 is formed on the buffer layer 110, and a gate insulating film ( The gate electrode 141 and the lower electrode 167 of the capacitor C are formed on the 130. One of the source / drain electrodes 161 and 165 and the source / drain electrodes 161 and 165 connected to the source / drain regions 121 and 125 through the contact holes 151 and 155 on the interlayer insulating layer 150. For example, the upper electrode 147 of the capacitor C connected to the source electrode 161 is formed.

A passivation layer 170 is formed on the entire surface of the insulating substrate 100, and one of the source / drain electrodes 161 and 165, for example, the drain electrode 165, is formed on the passivation layer 170 through the via hole 175. A lower electrode 180 which is a pixel electrode is formed as an anode electrode of an EL element connected to A pixel defining layer 185 having an opening 189 exposing a portion of the lower electrode 180 is formed, and an organic layer 190 is formed on the lower electrode 180 in the opening 189. An auxiliary electrode 193 is formed on the pixel defining layer 185 to prevent an upper electrode voltage drop, and an upper electrode 195 serving as a cathode is formed on the entire surface of the insulating substrate 100.

However, in the above method, in the process of forming the auxiliary electrode 193, when the semi-transparent metal film used as the auxiliary electrode 193 is deposited and patterned on the pixel defining layer 185, the organic layer 190 is formed. In addition, there is a problem in that the damage, in addition, the mask process is added to form the auxiliary electrode 193 for preventing the upper electrode voltage drop has a problem that the process is complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems of the prior art, and an object of the present invention is to provide an organic light emitting display device which prevents a voltage drop of an upper electrode by using an auxiliary electrode.

In addition, an object of the present invention is to provide a top-emitting organic electroluminescent display device capable of preventing the voltage drop of the upper electrode to improve the brightness and image characteristics, thereby increasing the size.

The present invention for achieving the above object is formed on an insulating substrate having a thin film transistor, the lower electrode electrically connected to the thin film transistor; An auxiliary electrode formed on the same layer as the lower electrode; A pixel defining layer which is not formed on the auxiliary electrode and has an opening formed only at an edge of the lower electrode to expose a portion of the lower electrode; An organic film formed on the opening; And an upper electrode formed on the entire surface of the insulating substrate and electrically connected to the auxiliary electrode, wherein the taper angle of the edge portion of the auxiliary electrode is 90 ° or more and less than 180 °.

Preferably, the taper angle of the edge portion of the auxiliary electrode is 90 ° or more and 135 ° or less, and the auxiliary electrode is preferably an auxiliary electrode for preventing an upper electrode voltage drop.

Preferably, the upper electrode is electrically connected to at least one side of the auxiliary electrode and the auxiliary electrode.

Preferably, the lower electrode and the auxiliary electrode are made of a conductive material having a higher work function than the upper electrode material.

The lower electrode and the auxiliary electrode are preferably made of a material having low specific resistance and excellent reflectance.

The lower electrode and the auxiliary electrode are preferably made of a single film or multiple films.

The lower electrode and the auxiliary electrode may be made of any one of Al, Mo, MoW, Ti, Ag / ITO, Ag / MoW, and MoW / Al (Nd) / ITO.

The lower electrode and the auxiliary electrode are preferably thicker than the organic layer.

Preferably, the auxiliary electrode has a linear structure.

Preferably, the auxiliary electrode has a grid structure.

The auxiliary electrode is preferably connected to the cathode lead terminal of the pad portion.

In addition, the present invention is formed on the insulating substrate having a thin film transistor, the lower electrode electrically connected to the thin film transistor; An auxiliary electrode formed on the same layer as the lower electrode; A pixel defining layer which is not formed on the auxiliary electrode and has an opening formed only at an edge of the lower electrode to expose a portion of the lower electrode; An organic film formed on the opening; And an upper electrode formed on the entire surface of the insulating substrate and electrically connected to the auxiliary electrode, wherein an upper surface of the auxiliary electrode is greater than or equal to a length of a lower surface.

The length of the upper surface of the auxiliary electrode is preferably the sum of the length of the lower surface and the length of the lower surface to twice the thickness of the auxiliary electrode.

In addition, the present invention includes the steps of simultaneously forming an auxiliary electrode and a lower electrode electrically connected to the thin film transistor on the insulating substrate having a thin film transistor; Forming a pixel defining layer that is not formed on the auxiliary electrode, the pixel defining layer having an opening formed only at an edge of the lower electrode to expose a portion of the lower electrode; Forming an organic layer on the opening; A method of manufacturing an organic light emitting display device, the method comprising forming an upper electrode formed on an entire surface of the insulating substrate and electrically connected to the auxiliary electrode.

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

FIG. 2 illustrates a cross-sectional structure of a top-emitting organic light emitting display device according to a first embodiment of the present invention, and is limited to R, G and B unit pixels.

Referring to FIG. 2, an active matrix organic light emitting display device (AMOLED) according to a first exemplary embodiment of the present invention includes source / drain electrodes 211 of a thin film transistor on an insulating substrate 200 for each of R, G, and B pixels. And an upper electrode voltage drop formed between the lower electrode 220 electrically connected to the second electrode 215, and the lower electrode 220 of each of the R, G, and B pixels, and formed on the same layer as the lower electrode 220. An auxiliary electrode 223 for prevention is provided.

In addition, it is not formed on the auxiliary electrode 223 and is formed only at an edge of the lower electrode 220, and is separated for each of R, G, and B pixels, and exposes a portion of the lower electrode 220. The pixel defining layer 230 having the opening 235 is formed.

In addition, an organic layer 240 is formed on the lower electrode 220 exposed by the opening 235 and the pixel defining layer, and is not formed on at least one side of the auxiliary electrode 223.

In addition, an upper electrode 250 is formed on the entire surface of the insulating substrate 200 and electrically connected to at least one side of the auxiliary electrode 223 for preventing the upper electrode voltage drop.

3A to 3C illustrate a cross-sectional view of a top-emitting organic light emitting display device according to a preferred embodiment of the present invention, and are limited to a capacitor C, one thin film transistor, and an EL device connected to the thin film transistor. It is shown.

Referring to FIG. 3A, an active layer 320 including source / drain regions 321 and 325 is formed on each of the R, G, and B pixels on the insulating substrate 300 on which the buffer layer 310 is formed.

After forming the active layer 320, the gate insulating layer 330 is formed on the insulating substrate 300, and a conductive material is deposited and patterned to form the gate electrode 341 and the lower electrode 347 of the capacitor. .

Next, an interlayer insulating film 350 is formed, and contact holes 351 and 355 exposing a portion of the source / drain regions 321 and 325 are formed.

After forming the contact holes 351 and 355, a source / drain electrically connected to the source / drain regions 321 and 325 through the contact holes 351 and 355 by depositing and patterning a conductive material such as MoW. A drain electrode 361 and 365 and an upper electrode 367 of a capacitor connected to one of the source / drain electrodes 361 and 365, for example, the source electrode 361, are formed to form a thin film transistor and a capacitor. do.

After forming the source / drain electrodes 361 and 365 and the upper electrode 367 of the capacitor, a protective film 370 is formed on the entire surface of the insulating substrate 300, and among the source / drain electrodes 361 and 365. For example, the via hole 375 exposing the drain electrode 365 is formed.

An upper portion for forming a lower electrode 380, which is an island-shaped pixel electrode electrically connected to the drain electrode 365 through the via hole 375, and at the same time to prevent a voltage drop of the upper electrode formed thereafter. An auxiliary electrode 383 for preventing the voltage drop is formed between the lower electrodes 380 of R, G, and B pixels.

At this time, the lower electrode 380 and the upper electrode voltage drop prevention auxiliary electrode 383 preferably have a taper angle of at least one edge portion of 90 ° or more and less than 180 °. In other words, it is preferable that the at least one edge portion is made of a reverse tapered structure. This is to allow the organic layer to be separated by the auxiliary electrode 383 for preventing the voltage drop when forming the organic layer to be formed later.

Preferably, the upper electrode voltage drop preventing auxiliary electrode 383 and the lower electrode 380 are made of a conductive material having a higher work function than the upper electrode material formed in a subsequent process. More preferably, the resistivity is low to minimize the voltage drop of the cathode electrode, and the Al, Mo, MoW, Ti, Ag / ITO, Ag / MoW, MoW having excellent reflectivity to increase the reflectance of the organic film formed in a subsequent process. It is preferably made of a material that can be used as / Al (Nd) / ITO or other reflective film or anode electrode. In addition, the lower electrode 380 and the upper electrode voltage drop preventing auxiliary electrode 383 may be formed as a single layer or multiple layers. In addition, the lower electrode 380 and the upper electrode voltage drop preventing auxiliary electrode 383 may be formed to be thicker than the organic film formed later.

Referring to FIG. 3B, a pixel defining layer 385 having an opening 389 exposing a portion of the lower electrode 380 is formed. In this case, the pixel defining layer 385 is not formed on the upper electrode voltage drop preventing auxiliary electrode 383, and is formed only at an edge portion of the lower electrode 380.

After the pixel defining layer 385 is formed, an organic layer 390 is formed on the opening. The organic layer 390 may be formed of various layers according to its function. In general, the organic layer 390 may include an emission layer, a hole injection layer HIL, a hole transport layer HTL, a hole blocking layer HBL, It has a multilayer structure including at least one layer of an electron transport layer (ETL), an electron injection layer (EIL).

In this case, the organic layer 390 is formed on the entire surface of the insulating substrate 300, but is not formed on at least one side of the auxiliary electrode 383. The pixel defining layer 385 may be formed to have a certain acute angle, so that the organic layer 390 may be over, but the auxiliary electrode 383 may have a taper angle of at least one edge portion of 90 ° or more but less than 180 °. This is because it is made of a reverse tapered structure, and is sufficiently thicker than the thickness of the organic layer 390.

Referring to FIG. 3C, an upper electrode 395 serving as a cathode electrode is formed on the entire surface of the insulating substrate 300. In this case, the upper electrode 395 forms a semi-transparent metal film by thinly depositing a metal material having a low work function, and forms a transparent conductive film formed by thickly depositing a transparent conductive material such as ITO or IZO on the semi-transparent metal film. It consists of a two-layered structure of a translucent metal film and a transparent conductive film.

Since the organic layer 390 is not formed on at least one side of the upper electrode voltage drop preventing auxiliary electrode 383, the upper electrode 395 may have at least one side surface of the upper electrode voltage drop preventing auxiliary electrode 383. Electrically connected. Therefore, since the upper electrode 395 is electrically connected to at least one side of the auxiliary electrode 383 for preventing the upper electrode voltage drop, it is possible to prevent the voltage drop of the upper electrode 395.

4 is a cross-sectional view of an organic light emitting display device limited to an auxiliary electrode for preventing an upper electrode voltage drop according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the taper angle α of at least one edge portion of the upper electrode voltage drop preventing auxiliary electrode 410 according to an exemplary embodiment of the present invention is preferably 90 ° or more, and more preferably, α is 90 ° to 135. It is preferable that it is °. That is, at least one edge portion is made of a reverse tapered structure.

When the taper angle α of the edge portion of the upper electrode voltage drop preventing auxiliary electrode 410 is less than 90 °, the organic layer is not insulated from the side of the upper electrode voltage drop preventing auxiliary electrode 410 when the organic layer is formed. This is because it can ride over the auxiliary electrode 410 for preventing the electrode voltage drop.

In addition, when the taper angle α of the edge portion of the upper electrode voltage drop preventing auxiliary electrode 410 is greater than 135 °, the length b of the lower surface of the upper electrode voltage drop preventing auxiliary electrode 410 is larger than the length a of the upper surface. This is because the auxiliary electrode 410 for preventing the voltage drop of the upper electrode may be relatively short. In addition, there is a problem in that a stress and a strong electric field are generated on the edge portion of the auxiliary electrode 410 for preventing the voltage drop of the upper electrode when the organic light emitting display is driven.

Meanwhile, when the cross-sectional shape of the upper electrode voltage drop preventing auxiliary electrode 410 is called a trapezoidal shape, the length of the upper surface of the upper electrode voltage drop preventing auxiliary electrode 410 is a, the length of the lower surface b is the upper surface of the auxiliary electrode 410. When the thickness of the auxiliary electrode 410 for preventing the electrode voltage drop is h and the angle obtained by subtracting 90 ° from the right angle of the taper angle α of the edge portion of the upper electrode voltage drop prevention auxiliary electrode 410 is α ', the upper electrode voltage drop prevention The length a of the upper surface of the auxiliary electrode 410 and the length b of the lower surface of the auxiliary electrode 410 have the following relationship.

Equation 1

b + htanα'≤a≤b + 2htanα '(0 ° ≤α'≤45 °)

Since the α 'is 0 ° to 45 °, the length a of the upper surface of the auxiliary electrode 410 for preventing the upper electrode voltage drop is preferably b ≦ a ≦ b + 2h.

That is, the length a of the upper surface of the upper electrode voltage drop preventing auxiliary electrode 410 is the sum of the length b of the lower surface to the thickness h of the upper electrode voltage drop preventing auxiliary electrode 410 and the length b of the lower surface. It is preferable.

5A to 5D illustrate a planar structure of an organic light emitting display device in which an auxiliary electrode for preventing an upper electrode voltage drop is formed according to an exemplary embodiment of the present invention.

Referring to FIG. 5A, the auxiliary electrode 520 for preventing the voltage drop of the upper electrode according to the exemplary embodiment of the present invention is connected to the lead terminal 510 of the pad part of the insulating substrate 500.

Referring to FIG. 5B, an upper electrode voltage drop preventing auxiliary electrode 520 has a grid shape, and a lower electrode 530, which is a pixel electrode, is formed in each grid of the upper electrode voltage drop preventing auxiliary electrode 520. It is formed to have an island shape. At this time, when the upper electrode voltage drop prevention auxiliary electrode 520 has a lattice shape, the cathode voltage drop is smaller.

Reference numeral 540 in the drawings is a via hole.

Referring to FIG. 5C, the island-like lower electrodes 530 are arranged in a matrix form of columns and rows, and have an upper portion in a line form between neighboring lower electrodes 530 arranged in a column direction. An auxiliary electrode 520 for preventing an electrode voltage drop is formed.

Referring to FIG. 5D, an auxiliary electrode 520 for preventing the voltage drop of the upper electrode is arranged in a row direction between the island-shaped neighboring lower electrodes 530 arranged in a matrix of rows and columns.

According to the embodiment of the present invention as described above, by forming the upper electrode voltage drop prevention auxiliary electrode at the same time with the lower electrode, to form the upper electrode voltage drop prevention auxiliary electrode to prevent the voltage drop of the cathode electrode without additional mask process. can do. In addition, by preventing the voltage drop of the cathode electrode, there is an advantage that can form a medium to large organic electroluminescent display device.

According to the present invention as described above, by forming the auxiliary electrode for preventing the voltage drop of the upper electrode, it is possible to provide an organic electroluminescent display device in which the voltage drop of the cathode electrode is prevented to prevent the unevenness of brightness and image characteristics.

In addition, by forming the upper electrode voltage drop prevention auxiliary electrode simultaneously with the lower electrode, it is possible to form a cathode bus line without an additional mask process.

In addition, it is possible to provide an organic light emitting display device having reduced power consumption by preventing a cathode voltage drop.

In addition, by preventing the cathode voltage drop, it is possible to provide a medium to large organic light emitting display device.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

Claims (23)

A lower electrode formed on an insulating substrate having a thin film transistor and electrically connected to the thin film transistor; An auxiliary electrode formed on the same layer as the lower electrode; A pixel defining layer which is not formed on the auxiliary electrode and has an opening formed only at an edge of the lower electrode to expose a portion of the lower electrode; An organic film formed on the opening; An upper electrode formed on an entire surface of the insulating substrate and electrically connected to the auxiliary electrode; The taper angle of the edge portion of the auxiliary electrode is 90 ° or more and less than 180 °. The method of claim 1, The taper angle of the edge portion of the auxiliary electrode is 90 ° or more and 135 ° or less. The method of claim 1, And the auxiliary electrode is an auxiliary electrode for preventing voltage drop of the upper electrode. The method of claim 1, And the upper electrode is electrically connected to at least one side of the auxiliary electrode and the auxiliary electrode. The method of claim 1, And the lower electrode and the auxiliary electrode are made of a conductive material having a work function larger than that of the upper electrode material. delete The method of claim 1, The lower electrode and the auxiliary electrode may be formed of a single layer or multiple layers. The method of claim 1, And the lower electrode and the auxiliary electrode are made of any one of Al, Mo, MoW, Ti, Ag / ITO, Ag / MoW, and MoW / Al (Nd) / ITO. The method of claim 1, The lower electrode and the auxiliary electrode are thicker than the organic layer. delete The method of claim 1, And the auxiliary electrode has a linear structure. The method of claim 1, The auxiliary electrode has a grid structure. The method of claim 1, And the auxiliary electrode is connected to a cathode lead terminal of a pad part. A lower electrode formed on an insulating substrate having a thin film transistor and electrically connected to the thin film transistor; An auxiliary electrode formed on the same layer as the lower electrode; A pixel defining layer which is not formed on the auxiliary electrode and has an opening formed only at an edge of the lower electrode to expose a portion of the lower electrode; An organic film formed on the opening; An upper electrode formed on an entire surface of the insulating substrate and electrically connected to the auxiliary electrode; The length of the upper surface of the auxiliary electrode is greater than the length of the lower surface of the organic light emitting display device. The method of claim 14, And the auxiliary electrode is an auxiliary electrode for preventing voltage drop of the upper electrode. The method of claim 14, The length of the upper surface of the auxiliary electrode is a sum of the length of the lower surface to twice the thickness of the auxiliary electrode and the length of the lower surface. The method of claim 14, The lower electrode and the auxiliary electrode are thicker than the organic layer. delete Simultaneously forming an auxiliary electrode and a lower electrode electrically connected to the thin film transistor on an insulating substrate including the thin film transistor; Forming a pixel defining layer that is not formed on the auxiliary electrode, the pixel defining layer having an opening formed only at an edge of the lower electrode to expose a portion of the lower electrode; Forming an organic layer on the opening; And forming an upper electrode formed over an entire surface of the insulating substrate and electrically connected to the auxiliary electrode. The method of claim 19, And the auxiliary electrode is an auxiliary electrode for preventing a voltage drop of an upper electrode, and is electrically connected to the upper electrode through a side surface of the auxiliary electrode. The method of claim 19, The lower electrode and the auxiliary electrode are thicker than the organic layer, wherein the organic light emitting display device is manufactured. delete The method of claim 19, And the upper electrode is electrically connected to at least one side of the auxiliary electrode and the auxiliary electrode.

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