KR101589748B1 - Organic Light Emitting Diode Display Device - Google Patents

Abstract

The organic electroluminescent device includes a substrate, a first electrode and a second electrode opposing each other on the substrate, and an organic layer disposed between the first electrode and the second electrode, the organic layer including at least a hole transport layer and a light emitting layer, And a buffer layer including an electron attracting material and a hole blocking material between the first electrode and the hole transporting layer.

Organic electroluminescent display device

Description

[0001] The present invention relates to an organic light emitting diode display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting display, and more particularly, to an organic light emitting display having a buffer layer formed by mixing an electron attracting material and a hole blocking material.

2. Description of the Related Art In recent years, the importance of flat panel displays (FPDs) has been increasing with the development of multimedia. In response to this, a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), an organic light emitting diode display device A variety of planar displays, such as a liquid crystal display, are being put into practical use.

Particularly, the organic light emitting display device has a response speed of 1 ms or less, a high response speed, low power consumption, and self light emission. In addition, there is no problem in the viewing angle, which is advantageous as a moving picture display medium regardless of the size of the apparatus. In addition, it can be manufactured at a low temperature and has been attracting attention as a next generation flat panel display device because of its simple manufacturing process based on existing semiconductor processing technology.

The organic light emitting display includes a hole injection layer (HIL), a hole transporting layer (HTL), an emission layer (EML), an electron transporting layer Layer, ETL) and an electron injection layer (EIL) are interposed.

However, although the driving voltage and the light emitting efficiency of the organic light emitting display device having such a structure can be increased, there is a problem that the lifetime characteristics are degraded.

Accordingly, the present invention provides an organic electroluminescent display device having a buffer layer formed by mixing an electron attracting material and a hole blocking material, and having excellent driving voltage, light emitting efficiency, and lifetime characteristics.

In order to achieve the above object, an organic light emitting display according to an embodiment of the present invention includes a substrate, a first electrode and a second electrode facing each other on the substrate, And a buffer layer including an electron attracting material and a hole blocking material between the first electrode and the hole transporting layer, the organic layer including at least a hole transporting layer and a light emitting layer.

And a hole injection layer between the first electrode and the buffer layer.

The electron attracting material may include at least one functional group selected from the group consisting of a cyanide group (-CN), a hydroxyl group (-OH) and a halide group (-I, -Br, -F).

Wherein the electron withdrawing material is selected from the group consisting of HAT (CN) ₆ , CuPc, F ₄ -TCNQ, PTCDA, 2,4,7-trinitrofluorenone, 1,4-dicyanobenzene, 9,10-dicyanoanthracene, tetrafluoro-1,4-benzoquinone, and the like.

The hole blocking material may include at least one selected from the group consisting of rubrene, NPB, TBP, TAPC, TCTA and 2-TMATA.

The mixing ratio of the electron attracting material and the hole blocking material may be 1: 1 to 10: 1.

The thickness of the buffer layer may be 1 to 50 nm.

The energy level of the hole blocking material may be smaller than the energy level of the hole transporting layer.

The first electrode may be a transparent electrode or a reflective electrode.

 The organic electroluminescent display device of the present invention has a buffer layer in which an electron attracting material and a hole blocking material are mixed, thereby being capable of simultaneously improving a driving voltage, a luminous efficiency and a lifetime characteristic.

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

1 is a view illustrating an organic light emitting display according to an exemplary embodiment of the present invention.

1, an organic light emitting display device according to an exemplary embodiment of the present invention may have an active matrix structure or a passive matrix structure. In this embodiment, an organic light emitting display having an active matrix structure will be described as an example .

More specifically, the buffer layer 105 is placed on a substrate 100 made of glass, plastic or metal. The buffer layer 105 is formed to protect a thin film transistor (TFT) formed in a subsequent process from impurities such as alkali ions or the like flowing out from the substrate 100. The buffer layer 105 is made of silicon oxide (SiO2), silicon nitride (SiNx) .

The semiconductor layer 110 is located on the buffer layer 105. The semiconductor layer 110 may be formed of amorphous silicon and may be formed of polycrystalline silicon that crystallizes amorphous silicon. A gate insulating layer 115 is formed on the semiconductor layer 110 to cover the semiconductor layer 110. The gate insulating film 115 may be a silicon oxide film, a silicon nitride film, or a double layer thereof.

A gate electrode 120 corresponding to a certain region of the semiconductor layer 110 is located on the gate insulating film 115. The gate electrode 120 may be formed of any one selected from the group consisting of Mo, Al, Cr, Au, Ti, Ni, Alloy. An interlayer insulating film 125 covering the gate electrode 120 is disposed on the gate electrode 120. The interlayer insulating layer 125 may be made of the same material as the gate insulating layer 115, and may be formed of, for example, a silicon oxide layer, a silicon nitride layer, or a double layer thereof.

A source electrode 135a and a drain electrode 135b are located on the interlayer insulating film 125. [ The source electrode 135a and the drain electrode 135b may be connected to the semiconductor layer 110 through the contact holes 130a and 130b penetrating the gate insulating layer 115 and the interlayer insulating layer 125. [ The source electrode 135a and the drain electrode 135b may be formed of a metal such as Mo, Al, Cr, Au, Ti, Ni, Lt; / RTI >

In an embodiment of the present invention, a top gate type thin film transistor (TFT) in which a gate electrode is disposed on a semiconductor layer is disclosed. Alternatively, a bottom gate type thin film transistor (TFT).

The passivation film 140 is located on the source electrode 135a and the drain electrode 135b. The passivation film 140 may be formed of a silicon oxide film, a silicon nitride film, or a multilayer thereof.

A first electrode 150, which is an anode, is located on the passivation film 140. The first electrode 150 may be a transparent conductive film such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). Particularly, in the case of the entire light emission, the first electrode 150 may further include a reflective layer made of aluminum (Al), silver (Ag), gold (Au), magnesium (Mg), calcium (Ca) have.

A bank layer 155 is positioned to isolate adjacent first electrodes on the first electrode 150. The bank layer 155 may be formed of an organic material such as polyimide, benzocyclobutene series resin, or acrylate. The bank layer 155 may have an opening 157 for exposing the first electrode 150.

An organic film layer 160 including at least a light emitting layer may be disposed on the substrate 100 including the bank layer 155. The organic layer 160 may further include at least one of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.

A second electrode 170, which is a cathode, is disposed on the organic layer 160. The second electrode 170 may be formed of a metal having a low work function such as silver (Ag), magnesium (Mg), calcium (Ca), or the like, and may be thin And may have a thickness sufficient to reflect light toward the first electrode 150 when the backlight is emitted.

Hereinafter, embodiments of the present invention with respect to the organic film layer of the organic light emitting display device described above will be described.

2 is a view illustrating an organic light emitting display according to an exemplary embodiment of the present invention.

2, an organic light emitting display 200 according to an exemplary embodiment of the present invention includes an anode 210, a buffer layer 220, a hole transport layer 230, a light emitting layer 240, an electron transport layer 250, The electron injection layer 260 and the cathode 270 may be sequentially stacked.

More specifically, the anode 210 may be made of a material such as ITO having a high work function, as described above.

The hole transport layer 230 plays a role of facilitating the transport of holes and is formed of a hole transport material 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-N-phenylamino) But is not limited thereto.

The light emitting layer 240 may be divided into red, green, and blue light emitting layers. When the light emitting layer 240 is red, it includes a host material including CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl) a dopant comprising at least one selected from the group consisting of acetylacetonate iridium, PQIr (acac) bis (1-phenylquinoline) acetylacetonate iridium, PQIr (tris (1-phenylquinoline) iridium) and PtOEP (octaethylporphyrin platinum) Phosphorescent material. Alternatively, the fluorescent material may include PBD: Eu (DBM) ₃ (Phen) or Perylene. However, the present invention is not limited thereto.

When the light emitting layer 240 is green, the light emitting layer 240 may be made of 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 made of a fluorescent material including Alq3 (tris (8-hydroxyquinolino) aluminum), but is not limited thereto.

When the light emitting layer 240 is blue, it may be made of a phosphorescent material including a host material including CBP or mCP and including a dopant material including (4,6-F ₂ ppy) ₂ Irpic, Alternatively, the fluorescent material may include any one selected from the group consisting of spiro-DPVBi, spiro-6P, distyrylbenzene (DSB), distyrylarylene (DSA), PFO polymer and PPV polymer. It does not.

The electron transport layer 250 serves to smooth the transport of electrons and may be made of any one or more selected from the group consisting of Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq, But are not limited thereto.

The electron injection layer 260 serves to smoothly inject electrons, and may be any one selected from the group consisting of LiF, Li, Ba, and BaF ₂ , but is not limited thereto.

The cathode 270 may be made of a metal having a low work function, such as silver (Ag), magnesium (Mg), calcium (Ca), or the like.

In an embodiment of the present invention, a buffer layer 220 may be further provided between the anode 210, which is the first electrode, and the hole transport layer 230. The buffer layer 220 may control the movement speed of the holes supplied to the light emitting layer 240 by the anode 210.

In general, the charge transfer balance is lowered due to the difference between the movement speed of holes and the movement speed of electrons, and thus the driving voltage and lifetime characteristics of the organic electroluminescence display device are deteriorated. In an embodiment of the present invention, a buffer layer 220 may be further included to compensate for this.

The buffer layer 220 may include an electron attracting material and a hole blocking material. The electron attracting material is a material containing at least one selected from the group consisting of a cyanide group (-CN), a hydroxyl group (-OH) and a halide group (-I, -Br, -F) ₆ , CuPc, F ₄ -TCNQ, PTCDA, 2,4,7-trinitrofluorenone, 1,4-dicyanobenzene, 9,10-dicyanoanthracene, 1,2,4,5-tetracyanobenzene and tetrafluoro-1,4-benzoquinone May be any one or more selected from the group.

The hole blocking material may include at least one selected from the group consisting of rubrene, NPB, TBP, TAPC, TCTA and 2-TMATA, preferably rubrene.

The electron attracting material and the hole blocking material may be mixed at a mixing ratio of 1: 1 to 10: 1. Here, if the ratio of the hole blocking material is smaller than that of the electron attracting material, there is an advantage that the moving speed of holes injected from the anode is decreased, driving voltage is increased, and luminous efficiency is prevented from being lowered. In addition, if the ratio of the electron attracting material to the hole blocking material is less than 10: 1, the hole blocking material ratio becomes small, and the hole moving speed is increased accordingly, so that the lifetime can be prevented from being lowered.

3, electrons injected from the anode (ITO) move toward the light-emitting layer (EML), and electrons injected from the cathode (Al) also travel through the light-emitting layer (EML) The hole and the electron form an exciton in the light emitting layer (EML) to emit light.

Here, the electron attracting material has a very high energy level, and thus plays a role of facilitating hole injection, thereby improving the driving voltage and the luminous efficiency, but the lifetime of the electron attracting material is lowered. Therefore, the hole blocking material can be mixed with the buffer layer. That is, since the energy level of the hole blocking material in the buffer layer is lower than the energy level of the hole transporting layer (HTL), the holes injected from the anode (ITO) are lowered in energy level due to the difference in energy level. Therefore, the lifetime characteristics of the organic film layer can be improved.

Therefore, in an embodiment of the present invention, by providing the buffer layer in which the electron attracting material and the hole blocking material are mixed, it is possible to improve the driving voltage and the light emitting efficiency due to the electron attracting material and to prevent the lifetime characteristic from being deteriorated due to the hole blocking material The effect can be shown.

4 is a view illustrating an organic light emitting display according to another embodiment of the present invention.

4, the OLED display 300 includes an anode 310, a hole injection layer 320, a buffer layer 330, a hole transport layer 340, a light emitting layer 350, , An electron transport layer 360, an electron injection layer 370, and a cathode 380 are stacked in this order.

In the present embodiment, description of the same configuration as that of the above embodiment will be omitted.

Unlike the above-described embodiment, in this embodiment, a hole injection layer 320 may further be interposed between the anode 310 and the buffer layer 330.

The hole injection layer 320 serves to facilitate the injection of holes from the anode 310. In this embodiment, the hole injection layer 320 further includes a hole injection layer 320, 330 can be lowered and the driving voltage and the luminous efficiency of the organic light emitting display device can be further increased.

Hereinafter, a preferred embodiment will be described to facilitate understanding of the present invention. However, the following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

<Comparative Example>

ITO was deposited as a first electrode on the glass substrate to a thickness of 320 Å, CuPc was deposited as a hole injection layer to a thickness of 50 Å, NPD was deposited to a thickness of 700 Å to form a hole transport layer, dopant spiro by mixing -DPVBi deposited to a thickness of 300Å, and the Alq ₃ was formed as the electron transport layer to a thickness of 200Å, a LiF was formed as an electron injection layer to a thickness of 10Å, first by forming an Al electrode as a second to a thickness of 1000Å The device was fabricated.

&Lt; Example 1 >

Except that the HAT (CN) ₆ and rubrene were co-deposited in a ratio of 4: 1 instead of the hole injection layer under the same conditions as the above-described comparative example to form a buffer layer.

&Lt; Example 2 >

Except that the buffer layer was formed by co-deposition of HAT (CN) ₆ and rubrene at a ratio of 3.3: 1 instead of the hole injection layer under the same conditions as the above-described comparative example.

&Lt; Example 3 >

Under the same conditions as the above-described comparative example, a device was fabricated except that a buffer layer was formed by co-depositing HAT (CN) ₆ and rubrene at a ratio of 10: 1 between the hole injection layer and the hole transport layer.

The driving voltage, luminance, efficiency, chromaticity coordinates, external photon efficiency and lifetime of the devices manufactured according to the above-described Comparative Examples and Examples 1 to 3 were measured and shown in the following Table 1, FIG. 5 shows a lifetime graph of a device manufactured according to the present invention.

Driving voltage
(V) Luminance
(cd / A) efficiency
(lm / W) Color coordinates External photon efficiency
(EQE%) Life (hr) (time to reach 50% luminance) CIE_x CIE_y Comparative Example 3.5 4.3 3.9 0.149 0.061 7.8 90 Example 1 3.5 4.6 4.2 0.149 0.061 8.3 120 Example 2 3.5 4.7 4.3 0.149 0.060 8.5 200 Example 3 3.5 4.7 4.3 0.149 0.063 8.7 230

Referring to Table 1 and FIG. 5, it can be seen that the device fabricated according to Examples 1 to 3 exhibits substantially the same driving voltage and color coordinates as the comparative example, and further improved luminance, efficiency, and lifetime characteristics.

As described above, the organic light emitting display device according to embodiments of the present invention has a buffer layer in which an electron attracting material and a hole blocking material are mixed, thereby improving the driving voltage, the light emitting efficiency, and the lifetime characteristics at the same time.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

1 and 2 show an organic light emitting display according to an embodiment of the present invention.

3 is a diagram illustrating an energy band structure of an organic light emitting display according to an exemplary embodiment of the present invention.

4 is a view illustrating an organic light emitting display according to another embodiment of the present invention.

5 is a graph showing the lifetime of the device fabricated according to Comparative Example and Examples 1 to 3;

Claims (9)

Board; A first electrode and a second electrode facing each other on the substrate; And And an organic layer disposed between the first electrode and the second electrode and including at least a hole transporting layer and a light emitting layer, A buffer layer including an electron attracting material and a hole blocking material between the first electrode and the hole transporting layer, The electron withdrawing material may be selected from the group consisting of Copper Phthalocyanine (CuPc), 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanop-quinodimethane (F ₄ -TCNQ), 3,4,9,10 perylenetetracarboxylic dianhydride ), 2,4,7-trinitrofluorenone, 1,4-dicyanobenzene, 9,10-dicyanoanthracene, 1,2,4,5-tetracyanobenzene and tetrafluoro-1,4-benzoquinone, The hole blocking material may be selected from the group consisting of N, N'-bis (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'- diamine (NPB), tributylphosphate bis (di-4-tolylaminophenyl) cyclohexane (TATC), 4,4 ', 4 "-tris (N-carbazolyl) -triphenylamine (TCTA) and 4,4' ] (2-TNATA), &lt; / RTI &gt; Wherein the mixing ratio of the electron attracting material and the hole blocking material is 1: 1 to 10: 1. The method according to claim 1, And a hole injection layer between the first electrode and the buffer layer. delete delete delete delete The method according to claim 1, Wherein the buffer layer has a thickness of 1 to 50 nm. The method according to claim 1, And the energy level of the hole blocking material is smaller than the energy level of the hole transporting layer. The method according to claim 1, Wherein the first electrode is a transparent electrode or a reflective electrode.

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