KR101576834B1 - Organic electro-luminescence device and method for fabricating of the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top emission type organic electroluminescent device, and more particularly to an auxiliary electrode for preventing a voltage drop of a second electrode.

A feature of the present invention is that the second electrode is electrically connected to the auxiliary electrode wiring through the auxiliary electrode contact hole in the non-emitting region.

Accordingly, since the second electrode has poor film quality and high resistivity, the same negative voltage is not applied for each pixel position, but a voltage difference occurs in a region near the voltage input region due to a voltage drop (IR drop) Thus, it is possible to prevent unevenness of luminance and image characteristics, and to cause a problem of raising the power consumption of the OLED.

Organic electroluminescent device, auxiliary electrode wiring, voltage drop

Description

TECHNICAL FIELD [0001] The present invention relates to an organic electroluminescent device and a method for fabricating the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top emission type organic electroluminescent device, and more particularly to an auxiliary electrode for preventing a voltage drop of a second electrode.

Until recently, CRT (cathode ray tube) was mainly used as a display device. However, in recent years, flat panel displays such as a plasma display panel (PDP), a liquid crystal display device (LCD), and an organic electro-luminescence device (OLED) Display devices have been widely studied and used.

Of the above flat panel display devices, an organic electroluminescent element (hereinafter referred to as OLED) is a self-luminous element and can be lightweight and thin because it does not require a backlight used in a liquid crystal display device which is a non-light emitting element.

In addition, it has a better viewing angle and contrast ratio than liquid crystal display devices, is advantageous in terms of power consumption, can be driven by DC low voltage, has a fast response speed, is resistant to external impacts due to its solid internal components, It has wide advantages.

Particularly, since the manufacturing process is simple, it is advantageous in that the production cost can be saved more than the conventional liquid crystal display device.

OLEDs having such characteristics are largely divided into a passive matrix type and an active matrix type. In a passive matrix type, a device is formed in a matrix form while crossing signal lines, whereas an active matrix type is a pixel A thin film transistor which is a switching element for on / off switching, a driving thin film transistor for flowing a current, and a capacitor for holding a voltage for one frame in a driving thin film transistor are provided for each pixel.

In recent years, passive matrix type has many limitations such as resolution, power consumption and lifetime, and active matrix type OLED capable of realizing high resolution and large screen is actively being studied.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view of a general OLED. FIG.

As shown in the drawing, a driving thin film transistor DTr is formed in the OLED 10 on the first substrate 1 for each pixel region P, and the first electrode 1 constituting the organic electroluminescent diode E 11, an organic light emitting layer 13, and a second electrode 15 are sequentially formed.

The driving thin film transistor DTr includes an active layer 21 and a gate electrode 23 and source and drain electrodes 27 and 29. An insulating film 25 is formed on the driving thin film transistor DTr, And the organic electroluminescent diode E is positioned.

The first electrode 11 of the organic electroluminescent diode E is connected to the drain electrode 29 of the driving thin film transistor DTr and the first electrode 11 is formed for each pixel region P, A bank (bank) 26 is located between the first electrodes 11.

The common voltage wiring 31 for applying a common voltage to the second electrode 15 is composed of the same layer and the same material as the gate electrode 23 of the driving thin film transistor DTr.

The common voltage wiring 31 is brought into contact with the second electrode 15 through the contact hole 33 in which a plurality of insulating films 25 formed on the upper part are etched.

The OLED 10 is divided into a top emission type and a bottom emission type according to a transmission direction of light emitted through the organic emission layer 13. There is a problem that it is difficult to apply to a high-resolution product due to the limitation of the aperture ratio.

In recent years, studies have been actively made on an upper light emitting method having a high aperture ratio and a high resolution.

As described above, in the case of the OLED 10 of the top emission type, the first electrode 11 is made of a transparent conductive material having a relatively large work function value and functions as an anode electrode, and the second electrode 15 is formed of a first electrode 11), and serves as a cathode electrode.

At this time, the light emitted from the organic light emitting layer 13 must pass through the second electrode 15, but the second electrode 15 has opaque characteristics due to the metallic material having a low work function value.

The second electrode 15 is formed by depositing a transparent conductive material thick on the semitransparent metal film thinly deposited on the second electrode 15. The second electrode 15 may be damaged by damage to the organic light- Temperature deposition is performed to minimize the thickness of the film.

Thus, the second electrode 15 has poor film quality and high resistivity.

Here, the high specific resistance of the second electrode 15 means that not the same negative voltage is applied for each pixel position but a voltage difference occurs in a region close to a voltage input region due to a voltage drop (IR drop) do.

This results in unevenness of luminance and image characteristics, and raises a problem of increasing the power consumption of the OLED 10.

SUMMARY OF THE INVENTION It is a first object of the present invention to provide an organic electroluminescent device capable of preventing a voltage drop.

It is a second object of the present invention to provide a uniform signal to improve luminance and image characteristics.

According to an aspect of the present invention, there is provided a light emitting device including a first substrate on which a light emitting region and a non-emitting region are defined; An auxiliary electrode line formed in the non-emission region on the first substrate; A driving thin film transistor formed in the light emitting region of the first substrate and including a semiconductor layer, a gate electrode, and a source and a drain electrode; An insulating layer formed on the source and drain electrodes and the auxiliary electrode wiring, the insulating layer including a contact hole such that a part of the auxiliary electrode wiring is exposed; A first electrode formed to be in contact with the drain electrode; An organic light emitting layer formed on the exposed first electrode; And a second electrode formed on the organic light emitting layer over the entire surface of the first substrate and electrically connected to the auxiliary electrode wiring, wherein light emitted from the organic light emitting layer is transmitted through the upper light emitting method An organic electroluminescent device is provided.

At this time, the auxiliary electrode line is formed of the same layer and the same material as the gate electrode, and the auxiliary electrode line is formed of the same layer and the same material as the source and drain electrodes.

Here, the first electrode is a selected one of indium-tin-oxide (ITO) and indium-zinc-oxide (IZO), and the second electrode overlaps a translucent metal film and a transparent conductive material.

As described above, the second electrode is electrically connected to the auxiliary electrode line through the auxiliary electrode contact hole in the non-emitting region according to the present invention, thereby preventing the voltage drop of the cathode electrode.

Therefore, a uniform signal can be applied to the organic electroluminescent device, and the brightness and image characteristics can be made uniform.

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

FIG. 2A is a plan view schematically showing an auxiliary electrode wiring formed on an OLED substrate according to an embodiment of the present invention, and FIG. 2B is a cross-sectional view schematically showing a cross section of FIG. 2A.

2A, a driver IC in which a driving circuit is mounted is formed on one edge of the first substrate 101 of the OLED 100, and an auxiliary electrode wiring 335 connected to the driver IC is formed on the first substrate 101 As shown in Fig.

The auxiliary electrode wiring 335 is electrically connected to the second electrode 115 which is the cathode electrode of the organic light emitting diode and the auxiliary electrode wiring 334 is electrically connected to the left and / And is disposed along the longitudinal direction of the first substrate 101 in advance by a meter.

The auxiliary electrode wiring 335 serves to apply the same voltage to all the pixels arranged in the pixel portion without generating a voltage drop (IR drop). Let me take a closer look at this later.

Referring to FIG. 2B, a driving TFT DTr is formed on the first substrate 101 for each pixel region P, and an organic electroluminescence diode E A first electrode 111 which is an anode electrode, an organic light emitting layer 113 and a second electrode 115 which is a cathode electrode are sequentially formed.

The first electrode 111 is electrically connected to the driving thin film transistor DTr.

A circuit portion 333 on which the scan driver and the gate driving circuit are mounted is positioned on both sides of the first substrate 101 and an auxiliary electrode wiring 335 is disposed on one side of the circuit portion 333.

The auxiliary electrode wiring 335 may be formed of the same layer and the same material as the gate electrode (23 in FIG. 1) of the driving element, or the same layer as the source and drain electrodes (27 and 29 in FIG. 1) It can be composed of the same material.

Thus, the auxiliary electrode wiring 335 is formed outside the circuit portion 333 by the gate line (38 in FIG. 1) connected to the gate driving circuit of the circuit portion 333.

The second electrode 115 is deposited on the entire surface of the first substrate 101. The second electrode 115 is electrically connected to the auxiliary electrode wiring 335 through a plurality of contact holes (not shown).

The first substrate 101 and the second substrate 102 are spaced apart from each other by a predetermined distance. The edge portions of the first substrate 101 are sealed and adhered to each other through a seal pattern 120 so as to be encapsulated The OLED 100 is completed.

In the OLED 100 according to the present invention, the light emitted from the organic light emitting layer 113 is emitted toward the second substrate 102 in the top emission type, so that the second electrode 115 must be made of a transparent conductive material.

However, the transparent conductive material uses a material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO), but such a transparent conductive material has a high work function and is difficult to use as a cathode electrode.

The second electrode 115 is formed by depositing a transparent conductive material thick on the semitransparent metal film thinly deposited with a metal material having a low work function. The second electrode 115 is formed by using an organic light emitting layer 113 are formed by low-temperature deposition in order to minimize damage, the film quality is poor and the resistivity is high.

Accordingly, not only the same negative voltage is applied to each pixel P but also a voltage difference is generated in a region far from a region where a voltage is input due to a voltage drop (IR drop) Which causes a problem of raising the power consumption of the OLED 100.

However, in the present invention, the auxiliary electrode wiring 335 is further formed, and the second electrode 115 is electrically connected to the auxiliary electrode wiring 335 through the contact hole (not shown) to prevent such a problem .

Here, the manner in which the auxiliary electrode wiring 335 and the second electrode 115 are electrically connected to each other will be described in detail with reference to FIG.

3 is a schematic cross-sectional view of an OLED according to an embodiment of the present invention.

As shown, the OLED 100 according to the present invention is divided into a light emitting region PA and a non-light emitting region NA. In the light emitting region PA, a plurality of driving thin film transistors DTr, An electroluminescent diode E is formed and an auxiliary voltage wiring 335 is formed in the non-emission area NA.

A semiconductor layer 201 is formed on the first substrate 101 of the light emitting area PA of the OLED 100. The semiconductor layer 201 is made of silicon and the center of the semiconductor layer 201 is made of active And source and drain regions 201a and 201c doped with a high concentration of impurities on both sides of the region 201b and the active region 201b.

A gate insulating layer 203 is formed on the semiconductor layer 201.

Gate electrodes 223 corresponding to the active region 201b of the semiconductor layer 201 are formed on the gate insulating film 203 and gate wirings extending in one direction although not shown in the figure.

A common voltage wiring 331 for applying a common voltage to the second electrode 115 is formed on the gate insulating film 203 in the same layer and the same material as the gate electrode 223.

A first interlayer insulating film 207a and a gate insulating film 203 under the first interlayer insulating film 207a are formed on the entire upper surface of the gate electrode 223 and the gate wiring and the common voltage wiring 331. In this case, The first and second semiconductor layer contact holes 208a and 208b exposing the source and drain regions 201a and 201c located on both sides of the active region 201b.

Next, upper portions of the first interlayer insulating film 207a including the first and second semiconductor layer contact holes 208a and 208b are separated from each other by a source exposed through the first and second semiconductor layer contact holes 208a and 208b, And source and drain electrodes 227 and 229 which are in contact with the source and drain regions 201a and 201c, respectively.

At this time, an auxiliary electrode wiring 335 is formed in the non-emission area NA of the substrate 101. The auxiliary electrode wiring 335 may be formed of the same layer and the same material as the gate electrode 223, Drain electrodes 227 and 229, and the same material.

In the present invention, the auxiliary electrode wiring 335 is composed of the same layer and the same material as the source and drain electrodes 227 and 229.

The first interlayer insulating film 207a exposed between the source and drain electrodes 227 and 229 and the two electrodes 227 and 229 and the drain contact hole 227 exposing the drain electrode 229 over the auxiliary electrode wiring 335 A common voltage contact hole 331a exposing the common voltage wiring line 331 and a second interlayer insulating film 207b having an auxiliary electrode contact hole 335a exposing the auxiliary electrode wiring 335 are formed.

The semiconductor layer 201 including the source and drain electrodes 227 and 229 and the source and drain regions 201b and 201c in contact with the electrodes 227 and 229 and the gate insulating film The gate electrode 203 and the gate electrode 223 constitute a driving thin film transistor DTr.

At this time, although not shown in the drawing, data lines (not shown) are formed which cross the gate wiring (not shown) and define the pixel region P. The switching thin film transistor (not shown) has the same structure as the driving thin film transistor DTr and is connected to the driving thin film transistor DTr.

The switching and driving thin film transistor (not shown) DTr is shown as an example of a top gate type in which the semiconductor layer 201 is a polysilicon semiconductor layer. As a variation thereof, the amorphous Or may be formed of a bottom gate type made of silicon nitride.

The first electrode 111, the organic light emitting layer 113 and the second electrode 115 constituting the organic electroluminescent diode E are sequentially formed on the second interlayer insulating film 207b, Respectively.

The first and second electrodes 111 and 115 and the organic light emitting layer 113 formed therebetween form an organic light emitting diode E.

The first electrode 111 is connected to the drain electrode 229 of the driving thin film transistor DTr through the drain contact hole 215 of the second interlayer insulating film 207b and the second electrode 115 is connected to the drain electrode 229 of the second thin film transistor DTr, The common voltage wiring 331 and the auxiliary electrode wiring 335 are connected through the common voltage contact hole 331a and the auxiliary electrode contact hole 335a of the common electrode wiring 207b.

In this case, the first electrode 111 is formed of indium-tin-oxide (ITO), which is a relatively high work function value, to serve as an anode electrode, and the second electrode 115 is formed of a cathode cathode is made of a metal material having a relatively low work function value.

The light emitted from the organic light emitting layer 113 is driven by the upper light emitting method that is emitted toward the second electrode 115.

The organic light emitting layer 113 may be a single layer made of a light emitting material and may include a hole injection layer, a hole transporting layer, an emitting material layer, and an electron transporting layer an electron transporting layer, and an electron injection layer.

Since the light emitted from the organic light emitting layer 113 has to be transmitted through the second electrode 115, the second electrode 115 may be formed by forming a transparent conductive material on the semi-transparent metal film thinly deposited with a metal material having a low work function, Respectively.

 Since the second electrode 115 is connected to the auxiliary electrode wiring 335 at this time, the second electrode 115 has poor film quality and high resistivity, so that the same negative voltage is not applied to each pixel P, A voltage difference is generated between the region where the voltage is input by the IR drop and the region far from the region where the voltage is input. This causes a variation in brightness and image characteristics, and raises the power consumption of the OLED 100 And it is possible to prevent it from being caused.

When a predetermined voltage is applied to the first electrode 111 and the second electrode 115 in accordance with a selected color signal, the OLED 100 emits a positive voltage, which is injected from the first electrode 111, The excited electrons are transported to the organic light emitting layer 113 to form an exciton. When the excitons transit from the excited state to the ground state, light is generated and emitted in the form of visible light.

At this time, the emitted light passes through the transparent second electrode 115 and exits to the outside, so that the OLED 100 realizes an arbitrary image.

The first electrode 111 is formed for each pixel region P and a bank 221 is located between the first electrodes 111 formed for each pixel region P.

That is, the banks 221 are formed in a matrix type of a grid structure as a whole on the substrate 101, and the first electrodes 111 are divided into the pixel regions P with the banks 221 as boundary portions for the respective pixel regions Respectively.

Hereinafter, a method of manufacturing the top emission type OLED according to the embodiment of the present invention will be briefly described.

In the embodiment of the present invention, since all the components are formed on the first substrate, the manufacturing method of the first substrate will be mainly described.

Hereinafter, a method of manufacturing a top emission type OLED in which a first electrode connected to a drain electrode of a driving thin film transistor serves as an anode electrode and a second electrode serves as a cathode electrode will be described as an example.

4A to 4F are cross-sectional views illustrating one pixel region of a top emission OLED according to an exemplary embodiment of the present invention.

4A, an amorphous silicon layer (not shown) is formed by depositing amorphous silicon on the light emitting region PA of the insulating substrate 101, and a laser beam is irradiated thereto or heat treatment is performed The amorphous silicon layer is crystallized with a polysilicon layer (not shown).

Thereafter, a mask process is performed to pattern a polysilicon layer (not shown) to form a semiconductor layer 201 in a pure polysilicon state. A buffer layer (not shown) may be formed by depositing an inorganic insulating material such as silicon oxide (SiO ₂ ) or silicon nitride (SiN x) on the entire surface of the insulating substrate 101 before forming an amorphous silicon layer (not shown) .

Next, silicon oxide (SiO ₂ ) is deposited on the semiconductor layer 201 of pure polysilicon to form a gate insulating film 203.

Thereafter, a first metal layer (not shown) is formed by depositing a low resistance metal material such as aluminum (Al), aluminum alloy (AlNd), copper (Cu), or copper alloy on the gate insulating film 203, The mask process is performed to form the gate electrode 223 corresponding to the central portion of the semiconductor layer 201. [

At this time, gate wirings (not shown) connected to a gate electrode (not shown) formed in a switching region (not shown) of the gate electrode 223 and extending in one direction and gate wirings (not shown) Thereby forming the common voltage wiring 331.

Next, impurities, that is, a trivalent element or a pentavalent element are doped on the entire surface of the substrate 101 by using the gate electrode 223 as a blocking mask, thereby forming impurities on the portion of the semiconductor layer 201 located outside the gate electrode 223 Doped source and drain regions 201a and 201c and a portion corresponding to the doped gate electrode 223 forms an active region 201b of pure polysilicon.

Next, an inorganic insulating material such as silicon nitride (SiNx) or silicon oxide (SiO ₂ ) is deposited on the entire surface of the substrate 101 on which the semiconductor layer 201 is formed to form a first interlayer insulating film 207a on the entire surface, To expose the source and drain regions 201a and 201c of the semiconductor layer 201 by simultaneously or collectively patterning the first interlayer insulating film 207a and the underlying gate insulating film 203, Layer contact holes 208a and 208b are formed.

Then, one of a metal material such as aluminum (Al), aluminum alloy (AlNd), copper (Cu), copper alloy, chromium (Cr) and molybdenum (Mo) is deposited on the first interlayer insulating film 207a, The source and drain electrodes 227 (227) and 227 (227) which contact the source and drain regions 201a and 201c through the first and second semiconductor layer contact holes 208a and 208b by forming a metal layer (not shown) , 229 are formed.

At the same time, an auxiliary electrode wiring 335 is formed on the first interlayer insulating film 207a in the non-light emitting area NA of the substrate 101. [

The source and drain electrodes 227 and 229 spaced apart from the semiconductor layer 201, the gate insulating layer 203, the gate electrode 223 and the first interlayer insulating layer 207a constitute a driving thin film transistor DTr.

Next, as shown in Figure 4b, the source and drain electrodes 227 and 229 and the auxiliary electrode wiring 335 over the inorganic insulating material, for example deposited, or organic silicon oxide (SiO ₂₎ or silicon nitride (SiNx) A second interlayer insulating film 207b is formed by applying an insulating material such as photo acryl or benzocyclobutene (BCB), and the second interlayer insulating film 207b is patterned to expose the drain electrode 229 of the driving thin film transistor DTr A drain contact hole 215 and a common voltage contact hole 331a exposing the common voltage wiring 331 are formed.

An auxiliary electrode contact hole 335a exposing the auxiliary electrode wiring 335 in the non-emission area NA of the substrate 101 is formed.

Next, as shown in FIG. 4C, on the second interlayer insulating film 207b having the drain contact hole 215, indium-tin-oxide (ITO) or indium-zinc-oxide (IZO) is deposited to have a thickness of about several thousand angstroms and patterned to form a first electrode 111 (111) which contacts the drain electrode 229 of the driving thin film transistor DTr through the drain contact hole 215 for each pixel region P ).

4D, a first organic insulating material such as photo acryl or benzocyclobutene (BCB) is applied on the first electrode 111 to form a first organic insulating material layer (not shown) And the bank 221 having the second common electrode contact hole 331b which rims the respective pixel regions P and exposes the common electrode wiring 331 is formed by patterning the same.

Next, as shown in FIG. 4E, the organic light emitting layer 113 is formed over the first electrode 111. [ The organic light emitting layer 113 may include red, green, and blue organic light emitting patterns (not shown) that emit red, green, and blue light, or white organic light emitting patterns 113 that emit white light. have.

In the case where the organic light emitting device is composed of red, green, and blue organic light emission patterns (not shown), thermal evaporation is performed using three shadow masks. In the case of forming only the white organic light emitting patterns 113, thermal shadowing using a single shadow mask is performed .

Next, as shown in FIG. 4F, a metal material having a relatively low work function value such as aluminum (Al), an aluminum alloy, silver (Ag), magnesium (Mg) The second electrode 115 is formed on the entire surface of the substrate 101 to have a relatively thin thickness of about 5 to 50 angstroms by performing one of thermal deposition and ion beam deposition.

At this time, the second electrode 115 is in contact with the common electrode wiring 331 through the second common electrode contact hole 331b, and the auxiliary electrode contact hole 335a in the non- (Not shown).

 Accordingly, the second electrode 115 has a structure in which the common signal voltage is applied to each pixel region P through the auxiliary electrode wiring 335, so that the voltage drop due to the internal resistance hardly occurs. It is possible to prevent the uneven luminance phenomenon in the display area.

Although not shown in the drawing, a transparent conductive material such as indium-tin-oxide (ITO) is formed on the second electrode 115 in order to protect the second electrode 115 having a relatively thin thickness and to prevent moisture penetration into the organic light- An auxiliary second electrode (not shown) having a thickness of about 500 Å to 2000 Å may be further formed of ITO or indium-zinc-oxide (IZO).

On the other hand, a sealing pattern (not shown) is formed along the edge of the light-emitting region with respect to the completed first substrate 101 as described above, the second substrate (102 of Fig. 2B) It is possible to complete the top emission type OLED 100 according to the embodiment of the present invention by bonding the first and second substrates 101 (102 of FIG. 2B) in a gas atmosphere or a vacuum atmosphere.

The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a cross section of a typical OLED. FIG.

FIG. 2A is a plan view schematically showing a state in which an auxiliary electrode wiring is formed on an OLED substrate according to an embodiment of the present invention; FIG.

FIG. 2B is a cross-sectional view schematically showing the section of FIG. 2A. FIG.

3 schematically illustrates a cross-section of an OLED according to an embodiment of the present invention.

FIGS. 4A through 4F are cross-sectional views illustrating steps of manufacturing a pixel region of a top emission OLED according to an exemplary embodiment of the present invention; FIGS.

Claims (5)

A first substrate on which a light emitting region and a non-emitting region are defined; An auxiliary electrode line formed in the non-emission region on the first substrate; A driving thin film transistor formed in the light emitting region of the first substrate and including a semiconductor layer, a gate electrode, and a source and a drain electrode; An insulating layer formed on the source and drain electrodes and the auxiliary electrode wiring, the insulating layer including a contact hole such that a part of the auxiliary electrode wiring is exposed; A first electrode formed to be in contact with the drain electrode; An organic light emitting layer formed on the exposed first electrode; A second electrode formed on the organic light emitting layer over the entire surface of the first substrate and electrically connected to the auxiliary electrode wiring, / RTI > Wherein the second electrode comprises a semitransparent metal film and a transparent conductive material film, Wherein the semitransparent metal film is located between the organic light emitting layer and the transparent conductive material film, the thickness of the transparent conductive material film is greater than the thickness of the semitransparent metal film, and the work function of the semi- Lt; / RTI > Wherein the light emitted from the organic light emitting layer is transmitted to an upper portion of the second electrode. The method according to claim 1, Wherein the auxiliary electrode wiring is formed of the same material and the same material as the gate electrode. The method according to claim 1, Wherein the auxiliary electrode wiring is formed of the same material and the same material as the source and drain electrodes. The method according to claim 1, Wherein the first electrode is a selected one of indium-tin-oxide (ITO) and indium-zinc-oxide (IZO). 5. The method of claim 4, Wherein the transparent conductive material layer is made of indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).

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