KR20140062598A - Organic light emitting diode and organic light emitting display device using the same - Google Patents

Abstract

An organic light emitting diode according to one embodiment of the present invention comprises a first electrode which is formed as a reflective electrode; a second electrode which is positioned to face the first electrode and is formed as a semipermeable electrode; and an organic layer which is formed between the first electrode and the second electrode. The first electrode is a multi layer structure comprising fluorine tin oxide (FTO) and a metal alloy. Therefore, the present invention is provided to maximize a micro cavity effect according to the excellence of a refractive index and improve the efficiency of a device according to brightness.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic electroluminescent device and an organic electroluminescent display device using the same,

The present invention relates to an organic electroluminescent device and an organic electroluminescent display using the same.

The organic light emitting display, which is one of the new flat panel display devices, is a self-luminous type and has a better viewing angle and contrast ratio than a liquid crystal display (LCD), and can be lightweight and thin because of no need for a separate backlight. . In addition, it is possible to drive the DC low voltage, has a high response speed, and is especially advantageous in terms of manufacturing cost.

An organic electroluminescent display device has a structure in which electrons and holes are injected into the light emitting layer from an electron injection electrode (cathode) and a hole injection electrode (anode), respectively, so that excitons, in which injected electrons and holes are combined, And an organic electroluminescent device which emits light when it emits light. In this case, the organic light emitting display device includes a top emission, a bottom emission, and a dual emission according to a direction in which light is emitted. In accordance with a driving method, a passive matrix ) And active matrix (Active Matrix).

Accordingly, when a scan signal, a data signal, a power supply, and the like are supplied to a plurality of subpixels arranged in a matrix form, the organic light emitting display device can display an image by causing the selected subpixel to emit light. At this time, the subpixel includes a thin film transistor (TFT) including a switching thin film transistor, a driving thin film transistor and a capacitor, a first electrode connected to the driving transistor included in the thin film transistor, an organic electroluminescent element including an organic layer and a second electrode .

Typically, the anode, the first electrode, deposits a conductive material to facilitate the flow of charge on the thin film transistor. Such a conductive material uses a material having a low resistance and a high transmittance. Recently, a transparent conductive material having a high work function such as indium-tin-oxide (ITO) has been widely used.

At this time, ITO (Indium-Tin-Oxide) is widely attracted to various applications not only in the display field but also in optical and solar cell. However, there is a problem that the characteristic of the material changes at a high temperature. Especially, when the heat treatment process at 300 ° C or more is included, the conductivity characteristics are reduced due to the volatility of the indium. As described above, ITO has not only poor heat resistance but also low corrosion resistance, which may result in unstable surface properties. In addition, as indium (Indium), which is one of the materials of ITO, is included in rare metals, the price has risen.

Accordingly, it is desired to develop various devices capable of improving the electrophoretic characteristics of the organic electroluminescent device while improving the high-temperature stability of the first electrode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an organic electroluminescent device capable of maximizing a micro cavity effect and improving device efficiency and an organic electroluminescent display device using the same. do.

According to an aspect of the present invention, there is provided an organic electroluminescent device including a first electrode formed as a reflective electrode, a second electrode disposed opposite to the first electrode, the second electrode formed as a transflective electrode, And an organic layer formed between the first electrode and the second electrode. In particular, the first electrode is a multilayer structure including a fluorine tin oxide (FTO) and a metal alloy.

According to another aspect of the present invention, there is provided an organic light emitting display including a substrate defining a display region having a plurality of pixel regions, a driving thin film transistor formed on each of the plurality of pixel regions on the substrate, A first electrode formed of a reflective electrode, an organic layer formed on the first electrode, and a second electrode formed on the organic layer, wherein the first electrode is formed on the first electrode, the protective layer formed on the thin film transistor, the FTO (Fluorine Tin Oxide) And a second electrode facing the first electrode and formed of a transflective electrode.

According to the present invention, since the refractive index is higher than that of the first electrode used in the related art, the micro cavity effect can be maximized and the efficiency characteristics of the device according to the brightness can be improved.

In addition, it is possible to provide an organic electroluminescent device which can improve the high-temperature stability of ITO and the problem of supply and demand of materials and is excellent in all-optical characteristics.

1 is a cross-sectional view schematically illustrating a structure of an organic electroluminescent device according to an embodiment of the present invention;
FIG. 2 is a graph comparing refractive index characteristics according to Comparative Examples and Examples; FIG. And
Figs. 3 to 5 are diagrams comparing emission spectra according to Comparative Examples and Examples. Fig.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

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

1, an organic light emitting display according to an exemplary embodiment of the present invention includes a first electrode 120, a second electrode 140, a first electrode 120 and a second electrode 140 (Not shown). The first electrode 120 has a multilayer structure including a FTO (Fluorine Tin Oxide) 126, a metal alloy 124, and an auxiliary electrode 122 under the first electrode 120.

In one embodiment, the organic electroluminescent device 100 includes a first electrode 120, an organic layer 130, and a second electrode formed on a substrate 110 on which a display region having a plurality of pixel regions is defined.

Accordingly, the organic light emitting display according to an embodiment of the present invention includes a driving TFT (not shown) for each of a plurality of pixel regions on a substrate 110 on which a display region having a plurality of pixel regions is defined, Thereby forming a protective layer (not shown). The organic electroluminescent device 100 is formed on the protective layer. That is, a first electrode connected to a drain electrode exposed by a contact hole formed in a protective layer is formed, an organic layer 130 is formed on the first electrode 120, And is positioned opposite to the electrode 120 to form the second electrode 140 of the transflective electrode.

First, the substrate 110 has a plurality of pixel regions divided by a gate wiring (not shown) and a data wiring (not shown), and a driving thin film transistor is formed in each of the plurality of pixel regions. Here, the substrate 110 may be a transparent glass material, or may be a plastic or polymer film having excellent flexibility in order to realize a flexible display.

A buffer layer (not shown) such as silicon oxide (SiO ₂ ), silicon nitride (SiN x) or the like is formed on the substrate 110 in order to protect a driving element formed in a subsequent process from impurities such as alkaline ions flowing out on the substrate 110 .

The thin film transistor (TFT) includes a driving thin film transistor and a switching thin film transistor. In addition, a compensation circuit for compensating a threshold voltage of the driving thin film transistor, that is, a plurality of capacitors may be additionally formed, . At this time, the driving thin film transistor (not shown) is connected to the switching thin film transistor to be controlled, and the voltage applied to the first electrode 120 can be adjusted according to the ON / OFF state of the driving thin film transistor.

The protective layer (not shown) serves to planarize and protect the thin film transistor, and may be formed in various forms. For example, it may be formed of an organic material such as BCB (benzocyclobutene) or acryl, or an inorganic material such as SiNx, and may be formed as a single layer, a double layer, or a multilayer.

The first electrode 120 is a reflective electrode that is an anode and the first electrode 120 is a FTO (Fluorine Tin Oxide) 126, a metal alloy 124, and an auxiliary electrode 122 ). ≪ / RTI >

That is, the first electrode 120 has a structure in which a metal alloy is disposed under the FTO (Fluorine Tin Oxide), and an auxiliary electrode 122 is further formed under the metal alloy 124 . Here, the FTO (Fluorine Tin Oxide) may be formed to a thickness of 10 to 1000 ANGSTROM.

At this time, as the first electrode 120 is formed of a material having a high work function, the ability to inject holes can be enhanced. That is, since the FTO (Fluorine Tin Oxide) introduced in the present invention has a work function of 5.1 eV, it has an advantage over the ITO (Indium Tin Oxide) having a work function of 4.7 eV.

Accordingly, the first electrode including FTO (Fluorine Tin Oxide) is excellent in the ability to inject holes.

The metal alloy 124 may be at least one selected from silver (Ag), gold (Au), aluminum (Al), nickel (Ni), copper (Cu), tungsten , And may be formed of a silver (Ag) alloy. Also, the auxiliary electrode 122 may be formed using FTO (Fluorine Tin Oxide) or ITO (Indium Tin Oxide), but the present invention is not limited thereto.

FIG. 2 is a graph comparing refractive index characteristics according to Comparative Examples and Examples. Here, the comparative example is the first electrode including ITO, and the embodiment is the first electrode including the FTO.

As shown in FIG. 2, it can be confirmed that the first electrode including FTO has a higher refractive index than ITO. That is, the FTO has the advantage of excellent refractive index compared to ITO at the same wavelength.

Accordingly, the first electrode including FTO (Fluorine Tin Oxide) has an excellent refractive index, thereby maximizing the micro cavity effect of the organic electroluminescent device.

The organic layer 130 is formed on the first electrode 120 and includes a light emitting layer emitting red, green, and blue colors.

Here, the organic layer 130 may be a single layer made of a light emitting material, or 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, and may have a thickness of 150 to 450 ANGSTROM.

The hole injection layer 131 may function to smoothly inject holes from the first electrode 120 into the light emitting layer and may be formed of at least one selected from the group consisting of CuPc (cupper phthalocyanine), PEDOT (poly (3,4) -ethylenedioxythiophene), PANI polyaniline or NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine). However, the present invention is not limited thereto.

The hole transport layer 132 not only transports the holes to the light emitting layer easily but also prevents the electrons generated from the cathode electrode from moving to the light emitting region, thereby enhancing the luminous efficiency. That is, the hole transport layer 132 plays a role of facilitating the transport of holes, and the hole transport layer 132 may be formed of a hole transport material such as NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N, N'-bis- (phenyl) -benzidine), TCTA (4- (9H-carbazol-9-yl) -N, ), CBP (4,4'-N, N'-dicarbazole-biphenyl), s-TAD or MTDATA (4,4 ' But the spirit of the present invention is not limited thereto.

The light emitting layer 133 includes a host and a dopant. The light emitting layer 133 may include a material that emits red, green, blue, and white light, and may be formed using phosphorescent or fluorescent materials.

In the case where the light emitting layer 133 emits red light, it includes a host material containing CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl) (1-phenylquinoline) iridium), and PtOEP (octaethylporphyrin platinum). The present invention also relates to a method for preparing the same, Phosphorescent material, but may alternatively be a fluorescent material including, but not limited to, PBD: Eu (DBM) ₃ (Phen) or Perylene.

When the light emitting layer 133 emits green light, a phosphorescent material containing a dopant material including a host material including CBP or mCP and containing Ir (ppy) ₃ (fac tris (2-phenylpyridine) iridium) Alternatively, it may be a fluorescent material including Alq3 (tris (8-hydroxyquinolino) aluminum), but is not limited thereto.

When the light emitting layer 133 emits blue light, it may be a phosphorescent material including a dopant material including (4,6-F ₂ ppy) ₂ Irpic or L2BD 111, including a host material including CBP or mCP .

Alternatively, the fluorescent material may be a fluorescent material including any one selected from the group consisting of spiro-DPVBi, spiro-6P, distyrylbenzene (DSB), distyrylarylene (DSA), PFO-based polymer and PPV-based polymer.

The electron transport layer 134 serves to smooth the transport of electrons and may include at least one selected from Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq , But the spirit of the present invention is not limited thereto. The electron transporting layer 134 may be formed using an evaporation method or a spin coating method, and the thickness of the electron transporting layer 134 may be 1 to 50 nm.

The electron injection layer 135 serves to smoothly inject electrons and may include at least one selected from Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq , But the spirit of the present invention is not limited thereto. The electron injection layer 135 may further include an inorganic material, and the inorganic material may further include a metal compound. The metal compound may include an alkali metal or an alkaline earth metal. Metal compound containing the alkali metal or alkaline earth metal is LiQ, LiF, NaF, KF, RbF, CsF, FrF, BeF 2, MgF 2, CaF 2, SrF 2, BaF 2 and RaF either be at least a selected one of _two, but But is not limited thereto. The electron injection layer 135 may be formed using an evaporation method or a spin coating method, and the thickness of the electron injection layer 135 may be 1 to 50 nm.

The organic layer 130 includes the hole injecting layer 131, the hole transporting layer 132, the light emitting layer 133, the electron transporting layer 134, and the electron injecting layer 135, At least one of a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injecting layer may be omitted.

On the other hand, the second electrode 140 is formed on the entire surface of the substrate 110 on the organic layer 130. The second electrode 140 may include Mg, Ca, Al, Ag, or an alloy thereof having a low work function. The second electrode 140 may include at least one of IZO, ZnO, or In ₂ O ₃ And an auxiliary electrode or bus electrode line formed of a material for a transparent electrode. For example, the second electrode 140 is made of an alloy of magnesium and silver (Mg: Ag) and has a semi-permeable property. That is, light emitted from the light emitting layer is externally displayed through the second electrode 140. Since the second electrode 140 has a transflective property, a part of the light is reflected by the first electrode 120 Lt; / RTI >

Accordingly, a microcavity effect, which is a repetitive reflection, is generated between the first electrode 120 serving as the reflective electrode and the second electrode 140. That is, light is repeatedly reflected in the cavity between the anode, which is the first electrode, and the cathode, which is the second electrode, thereby increasing the light efficiency.

Accordingly, when a predetermined voltage is applied to the first electrode 120 and the second electrode 140 according to a selected color signal, the organic light emitting display device according to an exemplary embodiment of the present invention transports holes and electrons to the organic layer When the excitons are transited from the excited state to the ground state, light is emitted and emitted in the form of visible light. At this time, the emitted light passes through the transparent second electrode 140 and exits to the outside, thereby realizing an arbitrary image.

Meanwhile, an encapsulation process is required to protect the light emitting diode of the subpixel from the outside. In the present invention, a general thin film encapsulation method can be used. Since such a thin film encapsulation method is a known technique, a detailed description thereof will be omitted in this specification.

Hereinafter, characteristics of an organic light emitting display according to an exemplary embodiment of the present invention will be described. However, the following examples are illustrative of the present invention, and the present invention is not limited to the following examples.

3 to 5 and Table 1 are diagrams comparing emission spectra according to Comparative Examples and Examples. Herein, the comparative example is an organic light emitting display device including a first electrode formed of ITO, and the embodiment relates to a first electrode formed of FTO, that is, an organic light emitting display device according to an embodiment of the present invention.

division result Brightness ( CD / m ² ) efficiency( CD / A) CIE _x CIE _y Blue (B) Comparative Example 338.6 3.386 0.133 0.055 Example 364.0 3.640 0.133 0.055 Green (G) Comparative Example 3077 30.77 0.286 0.694 Example 3220 32.20 0.285 0.695 Red (R) Comparative Example 1346 13.46 0.667 0.332 Example 1387 13.87 0.667 0.332

As shown in Figs. 3 to 5 and Table 1, it can be confirmed that the embodiment is improved by 3% in the red (R) pixel region compared with the comparative example, and the embodiment is improved by 4.6% in the green (G) , And it can be confirmed that the embodiment is improved by 7.5% in the blue (B) pixel region compared with the comparative example.

That is, it can be seen that the efficiency characteristics (cd / A) according to the luminance (cd / m ² ) as compared with the comparative example are improved in the red, green, and blue pixel regions.

Therefore, the organic light emitting display according to the embodiment of the present invention can improve the all-optical characteristic of the organic electroluminescent device by using the FTO, and can realize a high-quality image.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: organic electroluminescent device 110: substrate
120: first electrode 130: organic layer
131: Hole injection layer 132: Hole transport layer
133: light emitting layer 134: electron transporting layer
135: electron injection layer 140: second electrode

Claims (16)

A first electrode formed of a reflective electrode;
A second electrode facing the first electrode and formed as a transflective electrode; And
And an organic layer formed between the first electrode and the second electrode,
Wherein the first electrode comprises an FTO (Fluorine Tin Oxide) and a metal alloy. The method according to claim 1,
Wherein the first electrode comprises:
Layer structure in which the metal alloy is located under the FTO (Fluorine Tin Oxide). 3. The method of claim 2,
Wherein the first electrode comprises:
Wherein an auxiliary electrode is further formed under the metal alloy. The method of claim 3,
The metal alloy may be, for example,
The organic electroluminescent device according to claim 1, wherein the organic electroluminescent material comprises at least one selected from the group consisting of silver (Ag), gold (Au), aluminum (Al), nickel (Ni), copper (Cu), tungsten (W) device. The method of claim 3,
The auxiliary electrode
(FTO) or ITO (Indium Tin Oxide). The method according to claim 1,
The FTO (Fluorine Tin Oxide)
Wherein the first electrode is formed to a thickness of 10 to 1000 ANGSTROM. The method according to claim 1,
The FTO (Fluorine Tin Oxide)
And has a complex refractive index of 1.9 at a wavelength of 550 nm. The method according to claim 1,
The organic layer may include,
Wherein at least one of the hole injecting layer, the hole transporting layer, the electron blocking layer, the light emitting layer, the hole blocking layer, the electron transporting layer, and the electron injecting layer is included. A substrate on which a display region having a plurality of pixel regions is defined;
A driving thin film transistor formed on each of the plurality of pixel regions on the substrate;
A protective layer formed on the driving thin film transistor;
A first electrode formed on the protective layer and including a FTO (Fluorine Tin Oxide) and a metal alloy, the first electrode being formed as a reflective electrode;
An organic layer formed on the first electrode; And
And a second electrode disposed opposite to the first electrode on the organic layer and formed of a transflective electrode. 10. The method of claim 9,
Wherein the first electrode comprises:
And the metal alloy is positioned under the FTO (Fluorine Tin Oxide). 10. The method of claim 9,
Wherein the first electrode comprises:
And an auxiliary electrode is further formed on the lower portion of the metal alloy. 10. The method of claim 9,
The metal alloy may be, for example,
The organic electroluminescent device according to claim 1, wherein the organic electroluminescent material comprises at least one selected from the group consisting of silver (Ag), gold (Au), aluminum (Al), nickel (Ni), copper (Cu), tungsten (W) Display device. 10. The method of claim 9,
The auxiliary electrode
(FTO) or ITO (Indium Tin Oxide). 10. The method of claim 9,
The FTO (Fluorine Tin Oxide)
Wherein the first electrode is formed to a thickness of 10 to 1000 ANGSTROM. 10. The method of claim 9,
The FTO (Fluorine Tin Oxide)
And has a complex refractive index of 1.9 at a wavelength of 550 nm. 10. The method of claim 9,
The organic layer may include,
Wherein at least one of a hole injecting layer, a hole transporting layer, an electron blocking layer, a light emitting layer, a hole blocking layer, an electron transporting layer, and an electron injecting layer is included.

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