KR101875740B1 - Organic light emitting diode display device - Google Patents

Abstract

The present invention relates to an organic light emitting diode display.
The organic light emitting diode display according to the present invention includes a first substrate on which a display region having a plurality of pixel regions is defined, a first electrode formed on each of the plurality of pixel regions, an organic light emitting layer formed on the first electrode, A first layer formed on the entire surface of the display region as an upper portion of the organic light emitting layer and made of a first metal material having a first work function value and a first sheet resistance; A first metal material and a second metal material having a second work function value smaller than the first work function value and a second sheet material resistance value larger than the first sheet resistance value, Wherein the first metal material is contained at a ratio smaller than that of the second metal material or smaller than that of the second metal material.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting diode (OLED) display device,

The present invention relates to an organic light emitting diode display, and more particularly to an organic light emitting diode display having a relatively low sheet resistance and thermal stability.

A plasma display panel (PDP), a liquid crystal display device (LCD), an organic light emitting diode display (PDP), and the like, which can replace a CRT in recent years, Flat panel display devices such as organic light emitting diode (OLED) devices have been widely studied and used.

Among such flat panel display devices, liquid crystal display devices are advantageous for moving picture display and exhibit a large contrast ratio, and they are actively used in TVs, monitors, and the like. In optical anisotropy and polarization of liquid crystal, Thereby realizing an image.

In addition, the organic light emitting diode display device is a self-light emitting device and has a feature of being lightweight and thin because it does not require a backlight used in a liquid crystal display device which is a non-light emitting device.

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

Accordingly, researches for using an organic light emitting diode display device in various fields have been actively conducted.

Such an organic light emitting diode display device can be divided into a passive matrix type and an active matrix type, and an active type organic light emitting diode display device capable of low power consumption, fixed size, and large size is widely used.

The organic light emitting diode display device includes a switching and driving thin film transistor and an organic light emitting diode. In general, the organic light emitting diode includes a first electrode connected to the driving thin film transistor and a first electrode connected to the driving thin film transistor. A light emitting layer, and a second electrode located on top of the organic light emitting layer.

The first electrode may be made of a conductive material having a high work function value to serve as an anode electrode and the second electrode may be made of a metal material having a low work function value to serve as a cathode electrode.

Here, a silver (Ag) or an alloy (Ag: Mg) in which silver (Ag) and magnesium (Mg) are mixed is often used as the second electrode.

As described above, when silver (Ag) is used as the second electrode, silver (Ag) itself has a relatively low sheet resistance and good transmittance and absorbability. However, since the work function is high and the thermal property is poor, aggregation phenomenon, shrinkage phenomenon or discoloration occurs. When an alloy (Ag: Mg) mixed with silver (Ag) and magnesium (Mg) is used, the thermal characteristics are improved compared with the case of using only silver There is a disadvantage that the characteristics are not good and the sheet resistance becomes large.

Accordingly, there is a problem that the second electrode having thermal stability is limited while the sheet resistance is relatively low.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an organic light emitting diode (OLED) display device having a relatively low sheet resistance and a second electrode having thermal stability.

According to another aspect of the present invention, there is provided an organic light emitting diode display comprising: a first substrate having a plurality of pixel regions defined therein; A first electrode formed on each of the plurality of pixel regions; An organic light emitting layer formed on the first electrode; A first layer formed on the entire surface of the display region as an upper portion of the organic emission layer and including a first metal material having a first work function value and a first sheet resistance; 1 < / RTI > metal material having a first work function value and a second metal material having a second work function value less than the first work function value and a second sheet material value greater than the first sheet resistance, Wherein the first metal material is contained in a ratio that is equal to or smaller than that of the second metal material.

Wherein the first metal material is silver and the second metal material comprises at least one of magnesium (Mg) and calcium (Ca).

Wherein the first metal material and the second metal material are alloyed at a ratio of 1: 5 to 1:20.

And the second layer of the second electrode is formed to have the same thickness as the third layer or a thickness thinner than the third layer.

And the second and third layers of the second electrode are each formed within a thickness range of 10 Angstroms to 60 Angstroms.

According to another aspect of the present invention, there is provided an organic light emitting diode display comprising: a first substrate on which a display region having a plurality of pixel regions is defined; A first electrode formed on each of the plurality of pixel regions; An organic light emitting layer formed on the first electrode; And a second work function value smaller than the first work function value and a second work function value smaller than the first sheet property value, the first work function value being greater than the first work function value, A first layer of a second metal material having a first surface resistance and a second surface resistance, and a third layer having a third work function value smaller than the first work function value, And a second electrode having a triple layer structure of a second layer and a third layer made of a third metal material having a sheet resistance, wherein the first metal material has a content of at least 50% or more with respect to the second metal material .

Wherein the first metal material is silver, the second metal material is one of magnesium (Mg) or ytterbium (Yb), and the third metal material is ytterbium (Yb).

And the second layer of the second electrode is formed to have the same thickness as the third layer or a thickness thinner than the third layer.

The second layer of the second electrode is formed in a thickness range of 10 to 30 Angstroms and the third layer is formed in a thickness range of 30 to 50 Angstroms.

As described above, according to the present invention, by applying the second electrode having a comparatively low resistivity and the second and third layers having the triple layer structure formed on the upper and lower sides thereof to improve the reliability, the thermal resistance The reliability can be secured, and the electron injecting ability can be improved to improve the luminous efficiency.

In addition, since the second electrode can be realized as an electrode layer having a relatively low specific resistance, the electrooptic characteristics can be improved.

1 is an equivalent circuit diagram of a pixel of an organic light emitting diode display according to a preferred embodiment of the present invention.
2 is a cross-sectional view illustrating a configuration of an organic light emitting diode display device according to a preferred embodiment of the present invention.
3 is a cross-sectional view of an organic light emitting diode according to a first embodiment of the present invention.
FIGS. 4A and 4B are views showing the surface of a second electrode of a general organic light emitting diode to compare before and after high-temperature storage. FIG.
5 is a cross-sectional view of an organic light emitting diode according to a second embodiment of the present invention.

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

1 is an equivalent circuit diagram of a pixel of an organic light emitting diode display according to a preferred embodiment of the present invention.

1, a switching thin film transistor STr, a driving thin film transistor DTr, a storage capacitor StgC, and an organic light emitting diode E are included in each pixel region P of the organic light emitting diode display device do.

A gate line GL is formed in the first direction and a data line DL is formed in a second direction intersecting the first direction to define the pixel region P together with the gate line GL And a power supply line PL for applying a power supply voltage is formed apart from the data line DL.

A switching thin film transistor STr is formed at the intersection of the gate line GL and the data line DL and a driving thin film transistor STr electrically connected to the switching thin film transistor STr is formed in each pixel region P. [ A transistor DTr is formed.

At this time, the first electrode, which is one terminal of the organic light emitting diode E, is connected to the drain electrode of the driving thin film transistor DTr, and the second electrode, which is the other terminal, is grounded.

The power supply line PL is connected to the source electrode of the driving thin film transistor DTr to transmit the power supply voltage to the organic light emitting diode E. A storage capacitor StgC is formed between the gate electrode and the source electrode of the driving thin film transistor DTr.

Therefore, when a signal is applied through the gate line GL, the switching thin film transistor STr is turned on, and the signal of the data line DL is transmitted to the gate electrode of the driving thin film transistor DTr, DTr are turned on, so that light is output through the organic light emitting diode E.

At this time, when the driving thin film transistor DTr is turned on, the level of the current flowing from the power supply line PL to the light emitting diode E is determined, and thereby the light emitting diode E realizes a gray scale . The storage capacitor StgC serves to keep the gate voltage of the driving thin film transistor DTr constant when the switching thin film transistor STr is turned off so that the switching thin film transistor STr is turned off The level of the current flowing through the organic light emitting diode E can be kept constant until the next frame.

FIG. 2 is a cross-sectional view illustrating a configuration of an organic light emitting diode display according to a preferred embodiment of the present invention, FIG. 3 is a cross-sectional view of an organic light emitting diode according to a first exemplary embodiment of the present invention, 4b is a view showing the surface of the second electrode of a general organic light emitting diode for comparison with before and after storage at high temperature.

2, the organic light emitting diode display 100 includes a first substrate 112 on which a driving and switching thin film transistor DTr (not shown) and an organic light emitting diode E are formed, a first substrate 112 The first and second substrates 112 and 114 are spaced apart from each other and the edge portion of the first and second substrates 112 and 114 is sealed with a seal pattern 190, . At this time, a vacuum atmosphere may be provided between the first substrate 112 and the second substrate 114 which are spaced apart from each other, or an inert gas atmosphere may be formed by being filled with an inert gas.

A switching thin film transistor (not shown) and a driving thin film transistor DTr are formed on the first substrate 112 for each pixel region P, and each of the driving thin film transistors DTr A first electrode 147 connected to the first electrode 147 and an organic light emitting layer 155 disposed on the first electrode 147 to emit light of a specific color and a second electrode 158 positioned on the organic light emitting layer 155 ) Is formed on the organic light emitting diode (E).

First, the driving thin film transistor DTr includes a first region 113a made of polysilicon and a channel, and a second region 113b doped with impurities at high concentration on both sides of the first region 113a A semiconductor layer 113 is formed.

At this time, an insulating layer (not shown) made of silicon oxide (SiO ₂ ) or silicon nitride (SiNx), for example, an inorganic insulating material, is formed between the semiconductor layer 113 and the first substrate 112, 112). The reason why the insulating layer (not shown) is provided under the semiconductor layer 113 is that the insulating layer (not shown) is formed below the semiconductor layer 113 due to the release of alkali ions from the inside of the first substrate 112 during crystallization of the semiconductor layer 113 This is to prevent deterioration of characteristics.

A gate insulating layer 116 covering the semiconductor layer 113 is formed on the entire surface of the first substrate 112. A gate insulating layer 116 is formed on the gate insulating layer 116 to correspond to the first region 113a of the semiconductor layer 113, (Not shown).

A gate wiring (not shown) extending in one direction is formed on the gate insulating film 116, which is connected to a gate electrode (not shown) of a switching thin film transistor (not shown). At this time, the gate electrode 120 and the gate wiring (not shown) are formed of a first metal material having a relatively low specific resistance, such as aluminum (Al), aluminum alloy (AlNd), copper (Cu), copper alloy, molybdenum Mo), and molybdenum (MoTi).

An interlayer insulating film 123 made of silicon oxide (SiO ₂ ) or silicon nitride (SiN x), which is an inorganic insulating material, is formed on the entire surface of the first substrate 112 over the gate electrode 120 and the gate wiring Is formed.

The semiconductor layer contact hole 125 exposing the second regions 113b of the semiconductor layer 113 is formed in the interlayer insulating layer 123 and the gate insulating layer 116 under the interlayer insulating layer 123. [

A data line (not shown) is formed on the interlayer insulating film 123 including the semiconductor layer contact hole 125 so as to cross the gate line (not shown) to define the pixel region P and a power line Not shown) are formed.

Here, the data line (not shown) may include a second metal material such as aluminum (Al), aluminum alloy (AlNd), copper (Cu), copper alloy, molybdenum (Mo), molybdenum (MoTi) , Titanium (Ti), or the like.

Source and drain electrodes 133 and 136 are formed on the interlayer insulating film 123 to be in contact with the second region 113b exposed through the semiconductor layer contact hole 125, respectively.

The gate electrode 120 and the interlayer insulating film 123 and the source and drain electrodes 133 and 136 which are formed so as to be spaced apart from each other are formed on the gate insulating film 116, (DTr). A protective layer 140 having a drain contact hole 143 exposing the drain electrode 136 may be formed on the driving thin film transistor DTr.

Although not shown here, a switching thin film transistor (not shown) having the same lamination structure as the driving thin film transistor DTr is also formed on the first substrate 112. The switching thin film transistor (not shown) is electrically connected to a gate wiring (not shown) and a data wiring (not shown) and is also connected to a driving thin film transistor DTr.

A first electrode 147 is formed on the passivation layer 140 to contact the drain electrode 136 through the drain contact hole 143 of the driving TFT DTr.

The first electrode 147 is formed of a transparent conductive material having a relatively large work function value for each pixel region P, that is, a work function value ranging from 4.8 eV to 5.2 eV, for example, indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), or AZO (Al 2 O 3 doped ZnO). It is more preferable to use a double layer structure Lt; / RTI >

The first electrode 147 may be formed of a metal such as silver (Ag), aluminum (Al), gold (Au), platinum (Pt), chromium (Cr) Layer structure of a second conductive layer made of a transparent conductive material having a relatively large work function value in the range of 4.8 eV to 5.2 eV.

An insulating material such as benzocyclobutene (BCB), polyimide resin, or photo acryl is formed on the boundary of each pixel region P over the protective layer 140 by overlapping the edge of the first electrode 147, A bank 150 made of the same organic insulating material is formed.

An organic light emitting layer 155 is formed on the first electrode 147 in each pixel region P surrounded by the bank 150.

At this time, the organic light emitting layer 155 may be formed of a single layer made of an organic light emitting material and may have a multi-layer structure in order to increase the light emitting efficiency.

3, the organic light emitting layer 155 has a hole injecting layer (HIL) 210 sequentially from the top of the first electrode 147 serving as an anode electrode, A hole transporting layer (HTL) 220, an emission layer (EML) 230, an electron transporting layer (ETL) 240 and an electron injecting layer (EIL) And the like. In addition, a hole transporting layer (HTL) 220, an emission layer (EML) 230, an electron transporting layer (ETL) 240, an electron injecting layer , Or a triple layer structure including a hole transporting layer (HTL) 220, an emission layer (EML) 230, and an electron transporting layer (ETL) Structure.

Here, the hole injection layer (HIL) 210 serves to smoothly inject holes from the first electrode 147 serving as an anode electrode into the light emitting layer (EML) 230.

The hole injection layer (HIL) 210 may be formed of at least one of cupper phthalocyanine, PEDOT (poly (3,4) -ethylenedioxythiophene), PANI (polyaniline), and NPD And may be made of one or more selected materials.

The hole transport layer (HTL) 220 plays a role of facilitating the transport of holes. The hole transport layer (HTL) 220 transports holes, such as NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD ), N, N'-bis (phenyl) -benzidine), s-TAD and MTDATA (4,4'4 "-Tris (N-3-methylphenyl- ≪ / RTI >

The electron transport layer (ETL) 240 plays a role of facilitating transport of electrons and may be made of one or more materials selected from Alq3 (tris (8-hydroxyquinoline) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq have.

The electron injection layer (EIL) 250 serves to smooth the injection of electrons.

The electron injection layer EIL 250 may be formed of one or more materials different from the materials of the electron transport layer ETL 240 among Alq3 (tris (8-hydroxyquinoline) aluminum), PBD, TAZ, LiF, spiro- And may further contain an inorganic substance, which may further include a metal compound. Herein, the metal compound may include an alkali metal or an alkaline earth metal, and the metal compound including an alkali metal or an alkaline earth metal may be any one of LiQ, LiF, NaF, KF, RbF, CsF, FrF, BeF2 and RaF2 .

A second electrode 158, which is a semi-transparent electrode, is formed on the organic light emitting layer 155 and the bank 150.

The second electrode 158 is the most characteristic element in the organic light emitting diode display 100 according to the embodiment of the present invention and includes a first layer 158a made of the first and second metal materials A + And a second layer 158b and a third layer 158c, which are respectively formed on the upper and lower portions of the first and second metal materials C and C, respectively.

Here, the first metal material A may correspond to silver (Ag) having a lower sheet resistance and a higher work function value than the second metal material (B), for example, and the second metal material (B) Mg) or ytterbium (Yb) having a relatively low light absorptivity.

Accordingly, the first layer 158a is made of an alloy (Ag: Mg) mixed with silver (Ag) and magnesium (Mg), or an alloy (Ag: Yb ). ≪ / RTI > At this time, the first metal material (A) is included in a ratio of at least 50% or more with respect to the content of the second metal material (B), thereby improving the transmittance of the second electrode (158) .

The third metal material C may be Yb, which is one of the second metal materials B, to improve the element stability of the first layer 158a. All of the metallic materials that can be used are applicable.

The third metallic material C is a material constituting the second layer 158b and the third layer 158c which surround the first layer 158a made up of the first and second metallic materials A + And serves to improve the thermal stability of the second electrode 158.

More specifically, a second layer 158b and a third layer 158c made of a third metallic material C are formed on the upper and lower portions of the first layer 158a, respectively, It is possible to prevent aggregation phenomenon, shrinkage phenomenon or discoloration that may occur as a result of the inclusion of at least 50% or more of the first metal material (A) with respect to the second metal material (B), thereby improving reliability.

Meanwhile, it is preferable that the second electrode 158 having the triple layer structure according to the present invention is formed within the range of the thickness of the second electrode in the range of 120 angstroms (A) to 200 angstroms (A) .

Here, the second layer 158b and the third layer 158c may be formed to have the same thickness, but more preferably, have different thicknesses.

More specifically, the first layer 158a in the center is formed within a thickness range of 80 to 120 angstroms (A), and the second layer 158a formed on the top of the first layer 158a The second layer 158b is formed within a range of 10 angstroms to 30 angstroms and the third layer 158c formed below the first layer 158a is formed within a range of 30 angstroms The second layer 158b can be made thinner than the third layer 158c by forming it within a thickness range of 50 Å strong (Å).

Here, the second layer 158b may serve to improve the thermal stability.

The third layer 158c can serve as an injection layer for facilitating the injection of electrons. As a result, the proportion of electrons and positive spaces in the organic light emitting layer 155 is improved, and the organic light emitting diodes E ) Can be improved, and color stability can be improved.

By constituting the second electrode 158 as described above, the transmittance of the second electrode 158 can be more than 40% at a wavelength of 460 nm, more than 35% at a wavelength of 530 nm, and more than 25% at a wavelength of 620 nm .

This will be described in more detail with reference to Table 1 below.

Table 1 shows the sheet resistance and the transmittance in terms of items in Comparative Examples 1 and 2 and Example 1. In Comparative Example 1, the second electrode is an alloy (Mg: Ag) containing magnesium (Mg) and silver (Ag) in a ratio of 10 to 1 and has a thickness of 160 angstroms (Ag: Yb) containing silver (Ag) and ytterbium (Yb) in a ratio of 9: 1 each and the first layer having a thickness of 160 angstroms and ytterbium (Yb) (Ag) and magnesium (Mg) in a ratio of 9 to 1. The first electrode according to the present invention is a second electrode having a double-layered structure of Ag and Ag. Mg) and a first layer 158a having a thickness of 160 Angstroms and a second layer 158b formed on the top and bottom of the first layer with a thickness of 10 Angstroms (Yb) And a third electrode 158 having a triple layer structure of a third layer 158c. In this case, although the second layer and the third layer have the same thickness in Table 1, they are not limited thereto and may be formed to have different thicknesses as described above.

Item Comparative Example 1
Mg: Ag (10: 1) Comparative Example 2
Yb / Ag: Yb (9: 1) Example 1
Yb / Ag: Mg (9: 1) / Yb Sheet resistance (Ω / □) 29.7 10.2 5.59 Transmittance 460 nm 35.29 49.96 55.24 530 nm 29.13 40.97 45.23 620 nm 23.12 32.26 35.5

As shown in Table 1, Comparative Example 1 had a sheet resistance value of 29.7? /?, Comparative Example 2 had a sheet resistance value of 10.2? /?, Whereas Example 1 had a sheet resistance value of 5.59? / It can be seen that it has a lower sheet resistance value than Comparative Examples 1 and 2.

Also, the transmittance of Comparative Example 1 is 35.29 at 460 nm, 29.13 at 530 nm, 23.12 at 620 nm, 49.96 at 460 nm, 40.97 at 460 nm, and 32.26 at 620 nm , The transmittance of Example 1 was 55.24 at 460 nm, the transmittance at 530 nm was 45.23, and the transmittance at 620 nm was 35.5, which is higher than that of Comparative Examples 1 and 2.

Accordingly, the second electrode 158 of the triple-layer structure according to the first embodiment of the present invention has a low sheet resistance, is excellent in electron injection characteristics, and has a high transmittance to improve the luminous efficiency.

Although not shown, a capping layer may be further formed on the second electrode 158, which is formed of a triple layer, to increase the light extracting effect.

The first electrode 147 and the second electrode 158 described above and the organic light emitting layer 155 interposed between the two electrodes 147 and 158 form the organic light emitting diode E. [ Here, the first electrode 147 serves as a reflective electrode that reflects light, and the second electrode 158 serves as a translucent electrode that passes a part of the light and reflects a part of the light.

Accordingly, a part of the light emitted from the organic light emitting layer 155 passes through the second electrode 158 and is displayed outside, and a part of the light emitted from the organic light emitting layer 155 does not pass through the second electrode 158 And returns to the first electrode 147 again.

In other words, light is repeatedly reflected between the first electrode 147 and the second electrode 158 serving as the reflective layer, and this phenomenon is referred to as a microcavity phenomenon.

That is, in the embodiment of the present invention, optical efficiency is increased and light emission purity of the organic light emitting diode (E) is adjusted by using optical resonance phenomenon of light.

The organic light emitting diode display device 100 having the above-described configuration is configured such that when a predetermined voltage is applied to the first electrode 147 and the second electrode 158 according to a selected color signal, The injected holes and the electrons applied from the second electrode 158 are transported to the organic light emitting layer 155 to form an exciton. When the exciton transitions from the excited state to the ground state, light is generated, It is emitted in the form of a line.

At this time, an arbitrary image can be implemented on the screen of the organic light emitting diode display device 100 through the emitted light.

On the other hand, recently, display devices have been widely used as portable computers such as mobile phones and small computers, as well as desktop computers and wall-mounted televisions, and their use is being widened.

At this time, in order to realize the organic light emitting diode display device in a large area, the second electrode should have a smaller sheet resistance so that the film quality of the second electrode should be excellent, and especially the luminous efficiency should be high by having higher transmittance.

Accordingly, it is most preferable to form the second electrode by silver (Ag) having low sheet resistance and high transmittance. However, as described above, silver (Ag) has a poor thermal property and has a state as shown in FIG. There is a problem that aggregation phenomenon (F) and discoloration occur as shown in FIG. 4B after the storage at a high temperature and contraction phenomenon may occur there.

Hereinafter, an organic light emitting diode display device according to a second embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a view illustrating a structure of an organic light emitting diode according to a second embodiment of the present invention. The structure of the second electrode is the same as that of FIG. 3 except for the detailed structure of the second electrode. A detailed description is omitted, and reference is made to Fig.

As shown in FIG. 5, the organic light emitting diode E includes a first electrode 147 and a second electrode 258, and an organic light emitting layer 155 between the first electrode 147 and the second electrode 258.

The second electrode 258 includes a first layer 258a made of a first metal material A and a second layer 258b made of a first and a second metal material A + Layer structure of the third layer 258c and the third layer 258c.

The first metallic material A may correspond to silver (Ag), which has lower sheet resistance and higher transmittance than the second metallic material D, and the second metallic material D may correspond to magnesium (Mg) or It may correspond to calcium (Ca).

Accordingly, the second layer 258b or the third layer 258c may be an alloy (Mg: Ag) in which magnesium (Mg) and silver (Ag) are mixed or a mixture of calcium (Ca) (Cg: Ag). The second layer 258b and the third layer 258c are preferably made of the same metal materials (A + D), but are not limited thereto. For example, the second layer 258b may include different metal materials, (Ag) mixed with silver (Ag) and magnesium (Mg), and the third layer 258c may be an alloy (Ag: Ca) mixed with silver (Ag) and calcium (Ca).

At this time, the first metal material A and the second metal material D included in the second layer 258b or the third layer 258c may be alloyed at an alloy ratio of 1: 1 to 1:20 .

By forming silver (Ag) having a relatively low sheet resistance and high transmittance as the first layer 258a, it is possible to improve the transmittance while reducing the sheet resistance as much as possible. The upper part and the upper part of the first layer 258a The second layer 258b and the third layer 258c, which complement the characteristics of the silver (Ag), each having a poor thermal property, can be formed.

That is, the first layer 258a functions to lower the sheet resistance value and improve the transmittance, and the second layer 258b and the third layer 258c, respectively formed on the upper and lower portions of the first layer 258a, And improves reliability by preventing the aggregation phenomenon, the shrinking phenomenon, or the discoloration that may occur as the first layer 258a is formed of silver by improving the thermal stability. At this time, the third layer 258c may serve as an injection layer for facilitating electron injection. The proportion of electrons and positive spaces in the organic light emitting layer 155 is improved through the third layer 258c to improve the light emitting efficiency of the organic light emitting diode E and improve color stability.

The second electrode 258 of the triple layer structure according to the second embodiment of the present invention is formed within the range of the thickness of the second electrode 250. [ Is formed.

Here, the second layer 258b and the third layer 258c formed of the first and second metal materials A + D may have the same thickness or may have different thicknesses .

Specifically, the first layer 258a of the center may be formed within a thickness range of 80 to 120 angstroms (A), and the second layer 258b and the third layer 258c may be formed within a thickness range of 80 angstroms Can each be formed within a thickness range of 10 Angstroms (A) to 60 Angstroms (A). At this time, the second layer 258b and the third layer 258c are formed within a thickness range of 10 angstroms (A) to 30 angstroms (A), respectively, so that the first layer 258a is formed to have a thicker thickness Or more. When the second layer 258b and the third layer 258c are formed to have different thicknesses, the second layer 258b may be formed to have a thickness smaller than that of the third layer 258c.

The change characteristics of the second electrode 258 having such a triple layer structure in a high temperature environment will be described with reference to Table 2 below.

Table 2 shows the driving voltage, current luminance efficiency, and external quantum efficiency (EQE) of the second electrode before and after high temperature storage. Comparative Example 1 is a second electrode made of silver (Ag), Comparative Example 2 is a second electrode made of magnesium (Mg) and silver (Ag) in a ratio of 10: Example 3 is a double-layered second electrode composed of a first layer formed of silver (Ag), a second layer formed of magnesium (Mg) and silver (Ag) in a ratio of 10: 1 alloy (Mg: Ag) Example 2 according to the present invention is characterized in that the first layer 258a formed of silver (Ag) and the first layer 258a are formed respectively on the upper and lower sides, and magnesium (Mg) and silver (Ag) Layer structure of a second layer 258b and a third layer 258c made of an alloy (Mg: Ag). EQE is a ratio value representing the amount of photons emitted relative to the number of electrons injected. If the amount of light emitted when the amount of the same electron is large, the EQE is high. This means that the luminous efficiency is improved.

Before high temperature storage
The second electrode Driving voltage Current luminance efficiency
(cd / A) EQE
(%) After high temperature storage
The second electrode Driving voltage Current luminance efficiency
(cd / A) EQE
(%) Comparative Example 1
(Ag) 8.1 4.7 8.7 Comparative Example 1
(Ag) 10.1 4.0 7.6 Comparative Example 2
(Mg: Ag) 4.3 5.3 9.3 Comparative Example 2
(Mg: Ag) 4.2 5.2 9.1 Comparative Example 3
(Ag / Mg: Ag) 4.3 4.8 8.3 Comparative Example 3
(Ag / Mg: Ag) 4.2 4.8 8.2 Example 2
(Mg: Ag / Ag / Mg: Ag) 4.2 5.6 10.4 Example 2
(Mg: Ag / Ag / Mg: Ag) 4.2 5.8 11.1

First, in Comparative Example 1, the driving voltage was high, the driving voltage increased to a relatively large extent after the high temperature storage, and the driving voltage was unstable in Comparative Examples 1 and 2. In Comparative Examples 2 and 3, It can be seen that the second embodiment maintains the same drive voltage value even after storage at a high temperature. Thus, it can be seen that the second embodiment has a low driving voltage as compared with the driving voltages of the first to third comparative examples and does not have a driving voltage fluctuation even after storage at high temperature, and has a characteristic of being stable to heat.

Next, the current luminance efficiency (cd / A) showing the brightness per unit current is as follows. In the comparative example 1, the current luminance efficiency after the high temperature storage was relatively large. In the comparative example 2, Comparative Example 3 shows the same current luminance efficiency even after storage at a high temperature, whereas Example 2 shows that the current luminance efficiency is increased after storage at a high temperature. Thus, it can be seen that Embodiment 2 has the advantage that the current luminance efficiency before and after high-temperature storage is much higher than that of Comparative Examples 1 to 3, and that the efficiency is not reduced even after storage at high temperature, and is stable to heat.

Finally, EQE of Comparative Example 1 was 8.7 before storage at high temperature, 7.6 after storage at high temperature, Comparative Example 2 had EQE of 9.3 before storage at high temperature, 9.1 after storing at high temperature, Comparative Example 3 stored at high temperature The EQE before the high temperature storage was 8.3, the EQE after the high temperature storage was 8.2, and the Comparative Examples 1 and 3 had the EQE after storage at a high temperature, while the EQE before the high temperature storage was 10.4 and the EQE after the high temperature storage was 11.1, It can be seen that the EQE is not decreased and the heat stable property is obtained. In addition, in Example 2, EQE is much higher than in Comparative Examples 1 to 3, so that the light emitting efficiency can be improved.

As described above, the second electrode 258 of the triple-layer structure according to the second embodiment of the present invention is characterized not only in relatively low sheet resistance characteristics, but also in thermal stability and transmittance, thereby improving luminous efficiency.

The embodiments of the present invention as described above are merely illustrative, and those skilled in the art can make modifications without departing from the gist of the present invention. Accordingly, the protection scope of the present invention includes modifications of the present invention within the scope of the appended claims and equivalents thereof.

147: first electrode 158, 258: second electrode
210: Hole injection layer 220: Hole transport layer
230: light emitting layer 240: electron transporting layer
250: electron injection layer E: organic light emitting diode

Claims (9)

A first substrate on which a display region having a plurality of pixel regions is defined;
A first electrode formed on each of the plurality of pixel regions;
An organic light emitting layer formed on the first electrode;
A first layer formed on the entire surface of the display region as an upper portion of the organic emission layer and including a first metal material having a first work function value and a first sheet resistance; 1 < / RTI > metal material having a first work function value and a second metal material having a second work function value less than the first work function value and a second sheet material value greater than the first sheet resistance, Electrode,
Wherein the first metal material is contained in a ratio that is the same as or less than the second metal material,
Wherein the first metal material is silver (Ag), and the second metal material is magnesium (Mg).

delete The method according to claim 1,
Wherein the first metal material and the second metal material are alloyed at a ratio of 1: 5 to 1:20.
The method according to claim 1,
Wherein the second layer of the second electrode is formed to have the same thickness as the third layer or a thickness thinner than the third layer.
5. The method of claim 4,
Wherein the second and third layers of the second electrode are each formed within a thickness range of 10 to 60 Angstroms.
A first substrate on which a display region having a plurality of pixel regions is defined;
A first electrode formed on each of the plurality of pixel regions;
An organic light emitting layer formed on the first electrode;
And a second work function value smaller than the first work function value and a second work function value smaller than the first sheet property value, the first work function value being greater than the first work function value, A first layer of a second metal material having a first surface resistance and a second surface resistance, and a third layer having a third work function value smaller than the first work function value, And a second electrode having a triple layer structure of a second layer and a third layer made of a third metal material having a sheet resistance,
Wherein the first metal material has a content of at least 50% or more with respect to the second metal material,
Wherein the first metal material is silver (Ag), the second metal material is magnesium (Mg), and the third metal material is ytterbium (Yb).

delete The method according to claim 6,
Wherein the second layer of the second electrode is formed to have the same thickness as the third layer or a thickness thinner than the third layer.
9. The method of claim 8,
Wherein the second layer of the second electrode is formed in a thickness range of 10 Angstroms to 30 Angstroms and the third layer is formed in a thickness range of 30 Angstroms to 50 Angstroms.

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