KR20130066743A - Organic light emitting diode display device - Google Patents

Abstract

PURPOSE: An organic light emitting diode display device is provided to maximize a light extraction effect by forming a capping layer including silver on the upper part of a second electrode. CONSTITUTION: A first electrode(147) is formed on the upper part of a substrate. A hole transport layer includes a first material. A light emitting layer includes a second material. An electron transport layer includes a third material. A capping layer(250) is formed on the upper part of a second electrode(158).

Description

Organic light emitting diode display device

The present invention relates to an organic light emitting diode display device, and more particularly, to an organic light emitting diode display device in which a capping layer containing silver is formed on an upper portion of a second electrode.

2. Description of the Related Art Flat panel displays having excellent characteristics such as thinning, lightening, and low power consumption have been widely developed and applied to various fields.

In an organic light emitting diode (OLED) display device, electrons and holes are injected into a light emitting layer formed between a cathode, which is an electron injection electrode, and a cathode, which is a hole injection electrode, It is a device that emits light while paired and disappears. Such an organic light emitting display device can be formed on a flexible substrate such as plastic, and has excellent color by self-luminous and can be driven at a low voltage (10V or less). There is this.

The organic light emitting display includes red, green, and blue light emitting layers corresponding to red, green, and blue sub pixel regions, respectively.

A description with reference to FIG. 1 is as follows. 1 is a schematic cross-sectional view of a conventional OLED display.

As shown in FIG. 1, a hole transport layer 2 is formed on the first electrode 1 in common in the red, green, and blue subpixel regions R, G, and B.

The green auxiliary hole transport layer 3 and the red auxiliary hole transport layer 4 are formed on the hole transport layer 2, and then the red light emitting layer 5, the green light emitting layer 6, and the blue light emitting layer 7 are red and green, respectively. And blue subpixel regions (R, G, B).

The electron transport layer 8 is formed on the red, green, and blue light emitting layers 5, 6, and 7. In addition, a second electrode 9 is formed on the electron transport layer 8.

In the general organic light emitting display device, since the second electrode 9 is exposed to the outside, the second electrode 9 is easily damaged.

In addition, the light generated in the light emitting layers 5, 6 and 7 is not efficiently extracted, there is a problem that the light is lost by passing through a plurality of layers. Accordingly, there is a problem that the color is dropped.

An object of the present invention is to provide a capping layer containing silver on an upper portion of the second electrode, thereby preventing the damage of the second electrode and reducing the light extraction effect.

The present invention, the first electrode formed on the substrate; A hole transport layer formed on the first electrode and comprising a first material; An emission layer formed on the hole transport layer and including a second material; An electron transport layer formed on the emission layer and including a third material; A second electrode formed on the electron transport layer; An organic light emitting diode display device is formed on the second electrode and includes a capping layer including an organic material and a metal material.

The metal material is characterized in that silver (Ag).

The content of silver (Ag) is characterized in that less than 10%.

The organic material is any one of the first to third materials.

The thickness of the capping layer is characterized in that 500 ~ 800Å.

The organic light emitting display device according to the embodiment of the present invention provides an effect of maximizing light extraction by forming a capping layer including silver on the second electrode.

Accordingly, an organic light emitting display device having excellent bar color that can reduce light loss is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a cross-sectional view of a general organic light emitting display device. FIG.
2 is an example of a cross-sectional view of a subpixel area of an organic light emitting display device according to an exemplary embodiment of the present invention.
3 is a cross-sectional view schematically illustrating a part of an organic light emitting display device according to an exemplary embodiment of the present invention, and schematically illustrates a light emitting diode formed in red, green, and blue subpixel regions.
4 is a view showing that light is absorbed and scattered by silver nanoparticles.
5 shows surface plasmon resonance caused by silver nanoparticles.
6 is a photograph of the surface of the capping layer is changed according to the silver content.
7 is a schematic diagram illustrating a process of forming a capping layer by mounting a substrate in a chamber.

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

2 is an example of a cross-sectional view of a subpixel area of an organic light emitting display device according to an exemplary embodiment of the present invention.

First, as shown in FIG. 2, the subpixel area SP is defined in the substrate 110.

Here, the substrate 110 may be made of a transparent glass material or a transparent plastic or a polymer film having excellent flexibility.

The subpixel area SP may include, for example, red, green, and blue subpixel areas (R, G, and B of FIG. 3) that emit red, green, and blue light.

A switching thin film transistor (not shown) and a driving transistor DTr are formed in the sub pixel area SP and connected to the drain electrode 136 of the driving transistor DTr to form a first electrode 147, An anode is formed.

The light emitting material layer 155 is formed on the first electrode 147, and the light emitting material layer 155 has different patterns corresponding to the red, green, and blue subpixel regions (R, G, and B of FIG. 3). It may have, and will be described in more detail with reference to FIG.

The substrate 110 has a high concentration on both sides of the first region 113a and the first region 113a formed of polysilicon at a position where the subpixel region SP and the driving transistor DTr are to be formed. The semiconductor layer 113 including the second region 113b doped with impurities is formed. At this time, an insulating layer (not shown) made of, for example, silicon oxide (SiO 2) or silicon nitride (SiN x), which is an inorganic insulating material, may be disposed between the semiconductor layer 113 and the substrate 110. It may be further formed on the entire surface. The insulating layer is provided under the semiconductor layer to prevent deterioration of the characteristics of the semiconductor layer 113 due to the release of alkali ions from the inside of the substrate 110 during crystallization of the semiconductor layer 113.

A gate insulating film 116 is formed on the entire surface of the substrate 110 so as to cover the semiconductor layer 113 and a gate electrode (corresponding to the first region 113a of the semiconductor layer 113) 120 are formed.

A gate wiring (not shown) extending in one direction is formed on the gate insulating film 116, which is connected to the gate electrode 230 of the switching transistor. At this time, the gate electrode 120 and the gate wiring (not shown) may be formed of a first metal material having a low resistance characteristic such as aluminum (Al), an aluminum alloy (AlNd), copper (Cu), a copper alloy, molybdenum ), And molybdenum (MoTi).

Meanwhile, an interlayer insulating film 123 formed of an insulating material, for example, silicon oxide (SiO 2) or silicon nitride (SiN x), which is an inorganic insulating material on the entire surface of the substrate 110 over the gate electrode 120 and the gate wiring (not shown). ) Is formed. In this case, the interlayer insulating layer 123 and the gate insulating layer 116 below are provided with a semiconductor layer contact hole 125 that exposes each of the second regions 113b of the semiconductor layer.

On the upper surface of the interlayer insulating film 123 including the semiconductor layer contact hole 125, a sub-pixel region SP is defined to intersect with a gate wiring (not shown), and a second metal material, for example, aluminum (Not shown) made of any one or more of aluminum alloy (AlNd), copper (Cu), copper alloy, molybdenum (Mo), molybdenum (MoTi), chromium (Cr), titanium And a power supply wiring (not shown) is formed therebetween. At this time, power supply wiring (not shown) may be formed on the layer on which the gate wiring (not shown) is formed, that is, on the gate insulating film 116 so as to be spaced apart from the gate wiring (not shown).

The second interlayer insulating film 123 is formed on the interlayer insulating film 123 so as to be in contact with the second region 113b exposed through the semiconductor layer contact hole 125 and made of the same second metal material as the data interconnection Source and drain electrodes 133 and 136 are formed.

The gate electrode 120 and the interlayer insulating film 123 are sequentially formed with the source and drain electrodes 133 and 136 spaced apart from each other and the driving transistor DTr ).

Here, although not shown, a switching transistor having the same lamination structure as the driving transistor DTr is formed on the substrate 110 as well.

A protective layer 140 having drain contact holes 143 exposing the drain electrodes 136 of the driving thin film transistor DTr is formed on the driving transistor DTr.

The first electrode 147 is formed on the passivation layer 140 via the drain electrode 136 and the drain contact hole 143 of the driving transistor DTr.

Next, a bank (not shown) made of an insulating material, for example, an organic insulating material such as benzocyclobutene (BCB), polyimide resin, or photo acryl is formed at the boundary of the sub- 150 are formed. At this time, the bank 150 may be formed so as to overlap the edge of the first electrode 147 in a form surrounding the sub pixel region SP.

A light emitting material layer 155 is formed on the first electrode 147 in the sub pixel area SP surrounded by the bank 150.

A second electrode 158 is formed on the light emitting material layer 155 and the bank 150.

At this time, the first electrode 147, the light emitting material layer 155, and the second electrode 158 constitute a light emitting diode E.

Hereinafter, the light emitting diodes E formed in the red, green, and blue subpixel regions will be described in more detail with reference to FIG. 3.

3 is a cross-sectional view schematically illustrating a part of an organic light emitting display device according to an exemplary embodiment of the present invention, and schematically illustrates a light emitting diode formed in red, green, and blue subpixel regions.

As shown in FIG. 3, for example, red, green, and blue subpixel regions R, G, and B are defined in the substrate (110 of FIG. 2).

In addition, each of the red, green, and blue subpixel regions R, G, and B is formed between the first electrode 147 and the second electrode 158, and the first and second electrodes 147, 158. The light emitting material layer 155 and a capping layer CPL 250 formed on the second electrode 158 are included.

Specifically, the first electrode 147 is formed corresponding to red, green, and blue sub-pixel regions R, G, and B on the substrate 110, respectively.

Here, the first electrode 147 is a reflective electrode, and includes a reflective metal layer such as silver (Ag), aluminum (Al), gold (Au), platinum (Pt), chromium (Cr) or an alloy containing them, and the like. A transparent conductive material formed of a material having a high work function, such as indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), or AZO (Al2O3 doped ZnO) on top of the type metal layer Layer.

The second electrode 158 is a translucent electrode and may be made of an alloy of Mg and Ag or may be made of Ag, Al, Au, Pt) or chromium (Cr), or an alloy containing such a metal.

At this time, it is preferable that the second electrode 158 has a thickness capable of achieving, for example, a reflectance of 5% or more and a transmittance of 50%.

The first electrode 147 serves as a reflective electrode for reflecting light, and the second electrode 158 serves as a translucent electrode that allows a part of light to pass through and reflects a part of the light.

Accordingly, a part of the light emitted from the light emitting material layer 155 is emitted to the outside through the second electrode 158, and a part of the light emitted from the light emitting material layer 155 is transmitted through the second electrode 158 It 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, the optical resonance phenomenon of the light is used to increase the light efficiency and to adjust the light emitting purity of the light emitting diode E.

Since the wavelengths of light emitted from the light emitting material layers 155 of the red, green, and blue sub-pixel regions R, G, and B are different from each other, The thickness of the microcavity defined by the distance is different.

Specifically, the distance between the first and second electrodes 147 and 158 in the red subpixel area R is the first distance d1 and the first and second electrodes 147 in the green subpixel area G. When the distance between 158 is defined as the second distance d2 and the distance between the first and second electrodes 147 and 158 in the blue subpixel area B is defined as the third distance d3, the wavelength The first distance d1 of the red subpixel area R emitting long red light has the largest value, and the third distance d3 of the blue subpixel area B emitting the blue light having the shortest wavelength. Has the shortest value. That is, the first distance d1> the second distance d2> the third distance d3. As described above, in order to adjust the first distance d1, the second distance d2, and the third distance d3, a red auxiliary hole transport layer R′HTL 221 is formed in the red subpixel area R. In the green subpixel area G, a green auxiliary hole transport layer G'HTL 222 is formed.

The light emitting material layer 155 includes a hole injecting layer (HIL) 210, a hole transporting layer (HTL) 220, a light emitting layer 230, and an electron transporting layer 240 sequentially stacked .

In addition, the light emitting material layer 155 may include the red auxiliary hole transport layer 221 formed under the light emitting layer 230 of the red subpixel area R and the green auxiliary formed under the light emitting layer 230 of the green subpixel area G. The hole transport layer 222 may be included.

Hereinafter, the hole injection layer 210 and the hole transport layer 220 are formed in common in the red, green, and blue sub-pixel regions R, G, and B, respectively, . At this time, any one of the hole injection layer 210 and the hole transport layer 220 may be omitted.

Here, the hole transport layer 220 is, for example, NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N'-bis- (3-methylphenyl) -N, N'-bis ( phenyl) -benzidine), s-TAD and MTDATA (4, 4 ', 4 ″ -Tris (N-3-methylphenyl-N-phenyl-amino) -triphenylamine). .

The electron transport layer 240 formed in common to the red, green, and blue sub-pixel regions R, G, and B on the emission layer 230 serves to smooth the transport of electrons.

For example, the electron transport layer 240 may be formed of any one or more selected from the group consisting of Alq 3, PBD, TAZ, spiro-PBD, BAlq, and SAlq.

On the other hand, although not shown, an electron injection layer may be further formed on the electron transport layer (ETL) 240 to facilitate the injection of electrons.

The light emitting layer 230 corresponds to the red, green, and blue subpixel regions R, G, and B, and includes the red light emitting layers R-EML 231, the green light emitting layers G-EML 232, and the blue light emitting layer ( B-EML, 233).

In addition, the emission layer 230 may include a host and a dopant. The emission layer 230 may include, for example, a material that emits red, green, and blue light corresponding to the red subpixel area R, the green subpixel area G, and the blue subpixel area B. Phosphorescent or fluorescent materials can be used as such light emitting materials.

Here, for example, CBP (carbazole biphenyl) or mCP (1, 3-bis (carbazol-9-yl)) may be used as the host material of the emission layer 230.

Meanwhile, the red auxiliary hole transport layer 221 and the green auxiliary hole transport layer 222 formed under each of the red light emitting layer 231 and the green light emitting layer 232 adjust the distance between the first and second electrodes 147 and 158. To implement the microcavity.

Hereinafter, the capping layer 250 will be described in more detail.

The capping layer 250 according to an embodiment of the present invention is to increase the light extraction effect and may include an organic material (OM) and a metal material (MM).

The organic material OM is, for example, a material having excellent hole mobility characteristics, that is, the hole transport layer 220, the red and green auxiliary hole transport layers 221 and 222, and the red, green and blue light emitting layers 231, 232, and the like. It may be made of the same material as any one of the host material of 233). Alternatively, the organic material OM may be made of a material having excellent electron mobility characteristics, for example, the electron transport layer 240.

The metal material (MM) may be composed of, for example, transition metals, alkali metals, alkaline earth metals, rare earth metals, and alloys thereof, and specifically, silver (Ag), magnesium-silver alloy (Mg: Ag), samarium (samarium, Sm), and may be made of silver.

The reason for including the metal material (MM) in the capping layer 250 is that the surface plasmon resonance phenomenon occurs in the capping layer 250, thereby increasing light scattering and absorption at the same time to further improve the light extraction effect. To make it work.

First, the surface plasmon resonance phenomenon is demonstrated.

Here, plasmon is a phenomenon in which electrons in a material vibrate simultaneously, meaning waves of electrons.

Metals containing a large number of free electrons have a unique optical property by exhibiting surface plasmon resonance characteristics due to the behavior of free electrons when they become nano.

Specifically, surface plasmon resonance refers to a phenomenon in which free electrons of a metal surface vibrate collectively due to resonance between a surface of a metal nanoparticle of metal and a dielectric such as water or air due to resonance of a specific energy of light. Say

In other words, surface plasmon resonance is a collective charge density oscillation of free electrons occurring on the surface of the metal thin film, and the surface plasmon waves generated by this process travel along the interface between the metal and the dielectric material adjacent to the metal. Surface electromagnetic waves.

Here, with reference to Figures 4 and 5 looks at the surface plasmon resonance phenomenon by the silver nanoparticles.

4 is a view showing that light is absorbed and scattered by silver nanoparticles, and FIG. 5 is a view showing that surface plasmon resonance occurs by silver nanoparticles.

First, as shown in FIG. 4, the silver nanoparticles AN strongly absorb light L that has passed through the organic material OM. In addition, the light L absorbed by the silver nanoparticles AN becomes scattered light SL by being scattered in all directions when it comes into contact with the surface of the silver nanoparticles AN.

That is, the silver nanoparticles (AN) resonates strongly with light in the visible light region, thereby absorbing light strongly and scattering the absorbed light to emit more photons. Therefore, silver (Ag) is an excellent metal capable of efficiently inducing surface plasmon resonance.

Referring to FIG. 5, first, the capping layer 250 includes, for example, an organic material (OM) and silver nanoparticles (AN).

Here, the free electrons of the silver nanoparticles (AN) are collectively vibrated by the light L1 incident between the organic material (OM) and the surface of the silver nanoparticles (AN), and by the collective vibrations of the free electrons. The generated surface plasmon wave (SPW) proceeds along the surface of the silver nanoparticle (AN) and the organic material (OM), which is a dielectric adjacent thereto. Accordingly, surface plasmon resonance occurs, whereby light extraction is increased.

At this time, the silver (Ag) contained in the capping layer 250 is preferably less than 10%.

The reason will be described with reference to FIG. 6 together. FIG. 6 is a photographed image of the surface of the capping layer 250 which is changed according to the silver content.

First, (A) of FIG. 6 has a content of silver of 0%, (B) has a content of silver of 5%, and (C) has a content of silver of 10%.

When the content of silver reaches 5%, the convex pattern LP starts to appear as shown in FIG. 6B, and when the content of silver reaches 10%, the convex pattern as shown in FIG. 6C. (LP) gets worse. Due to the convex pattern LP, the surface of the capping layer 250 becomes rough, and the roughened surface interferes with the light propagation path, and thus reduces the light extraction effect.

In addition, when the silver content is 10% or more or when silver is formed as a thin film, a blue shift phenomenon occurs. This is because silver is a metal material having high reflectance and high absorption, and when the content of silver is high, the light emitted from the light emitting layer (230 of FIG. 3) loses its original wavelength, for example, changes its wavelength according to the reflectance and absorption of silver. to be. That is, when the content of silver is 10% or more, the light emitted from the light emitting layer 230 is absorbed and reflected very strongly by the silver, thereby causing a blue shift phenomenon.

Thus, to increase the light efficiency of the light, the capping layer 250 preferably contains less than 10% silver.

On the other hand, the thickness of the capping layer 250 may be, for example, 500 ~ 800Å.

Hereinafter, with reference to [Table 1], looks at the effects according to the embodiment of the present invention. Table 1 shows simulation results showing the characteristics of each of the subpixel regions Ref of the organic light emitting display and the subpixel regions of the organic light emitting display according to the exemplary embodiment of the present invention.

Where V is the driving voltage, cd / A is the light intensity, Im / W is the power efficiency, and CIE_x and CIE_y are the x- and y-axis values of the color coordinates, respectively, and the SPR effect is increased in the embodiment than in the comparative example. This figure shows the resonance effect.

In addition, the thickness of the capping layer 250 is 630 kPa, the numerical value in parentheses is 5% of the silver content.

As shown in Table 1, the color coordinate values of each of the red, green, and blue subpixel regions of the organic light emitting display according to the exemplary embodiment of the present invention are similar to those of the general organic light emitting display.

In addition, in the case of the blue subpixel area, the intensity of light is 0.5 (cd / A), power efficiency is 0.4 (Im / W), and surface plasmon resonance effect is increased by about 12% in comparison with the comparative example (Ref).

In the case of the green subpixel area, the light intensity is increased by about 7.3 (cd / A), the power efficiency is about 0.7 (Im / W), and the surface plasmon resonance effect is increased by 7.6% in comparison with the comparative example (Ref).

Similarly, in the case of the red subpixel area, the light intensity is about 1 (cd / A), the power efficiency is about 1 (Im / W), and the surface plasmon resonance effect is increased by 5.6% in comparison with the comparative example (Ref).

In other words, in the embodiment of the present invention by including less than 10% silver in the capping layer 250, not only increases the light intensity and power efficiency, but also increases the surface plasmon resonance effect. Accordingly, the light extraction effect of the capping layer 250 is further increased.

Referring to FIG. 7, a brief description will be given of a method of forming the capping layer 250 according to an exemplary embodiment of the present invention.

7 is a schematic diagram illustrating a process of forming a capping layer by mounting a substrate in a chamber.

First, the substrate 110 on which the second electrode 158 of FIG. 3 is formed is mounted in the chamber 300.

The silver nanoparticle injection unit 310 injects silver nanoparticles AN, and the organic material injection unit 320 injects the organic material OM. Accordingly, the silver nanoparticles (AN) and the organic material (OM) are deposited together on the substrate 110 to form the capping layer 250.

In this case, the content of the silver nanoparticles (AN) may be less than 10% of the capping layer 250.

As described above, in the embodiment of the present invention by depositing less than 10% silver nanoparticles with an organic material to form a capping layer, it is possible to maximize the light extraction effect. Accordingly, an organic light emitting display device having excellent color is provided.

In addition, by forming a capping layer on the second electrode, the second electrode can be protected from the outside, thereby extending the life of the organic light emitting display device.

The present invention is not limited to the embodiment, and various changes and modifications are possible without departing from the spirit of the present invention.

147: first electrode 158: second electrode 210: hole injection layer
220: Hole transport layer 230: Light emitting layer 240: Electron transport layer
250: capping layer

Claims (5)

A first electrode formed on the substrate;
A hole transport layer formed on the first electrode and comprising a first material;
An emission layer formed on the hole transport layer and including a second material;
An electron transport layer formed on the emission layer and including a third material;
A second electrode formed on the electron transport layer;
A capping layer formed on the second electrode and including an organic material and a metal material.
An organic light emitting diode display device comprising a.
The method of claim 1,
And the metal material is silver (Ag).
3. The method of claim 2,
The organic light emitting diode display device, characterized in that the content of silver (Ag) is less than 10%.
The method of claim 1,
And the organic material is any one of the first to third materials.
The method of claim 1,
The capping layer is an organic light emitting diode display device, characterized in that the thickness of 500 ~ 800Å.

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