KR20090061395A - Fabrication method of luminescent display panel and method for fabricating the same - Google Patents

Abstract

A luminescent display panel and a manufacturing method thereof are provided to improve an adhesive property and stability of an interface between an anode and a hole injection layer by forming a buffer layer between the anode and the hole injection layer. An anode(148) is formed on a substrate(100). A cathode(170) forms an electric field with the anode. An organic layer is formed between the anode and the cathode. The organic layer includes a hole injection layer(152), a hole transport layer(154), a light emitting layer(160), an electron transport layer(162), and an electron injection layer(164). A buffer layer(150) is formed between the anode and the hole injection layer. The buffer layer includes an inorganic compound, a first organic compound, and a second organic compound. The inorganic compound stabilizes the interface between the anode and the hole injection layer. The first organic compound injects a hole into the organic layer. The second organic compound transports a hole into the organic layer.

Description

Light emitting display panel and its manufacturing method {FABRICATION METHOD OF LUMINESCENT DISPLAY PANEL AND METHOD FOR FABRICATING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting display panel, and more particularly, to a light emitting display panel capable of improving interface stabilization, low voltage driving, and lifespan, and a method of manufacturing the same.

The organic electroluminescent display is a kind of display using organic light emission. Since it is a self-luminous type, it has better viewing angle, contrast, etc. than a liquid crystal display, and is light in weight because it does not require a backlight, thus enabling low voltage driving. Realization is also advantageous in terms of power consumption.

In general, an organic light emitting display device has a multilayer organic layer formed between an anode and a cathode, which are opposite electrodes, and the organic layer includes a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. Is formed. In this case, indium tin oxide (ITO), which is a transparent material, is generally used to emit light emitted from the organic light emitting display to the outside. The anode formed of the transparent material is an inorganic material, and the adhesion between the hole injection layer and the interface of the organic material formed on the anode is poor, causing instability in durability. As a result, a surface potential difference occurs at the junction interface between the anode and the hole injection layer, and thus the hole movement is not stable.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting display panel and a method of manufacturing the same, which can improve interface stabilization, low voltage driving, and lifespan.

In order to achieve the above technical problem, a light emitting display panel according to an aspect of the present invention comprises an anode formed on a substrate, a cathode for forming an electric field with the anode, an organic layer formed between the anode and the cathode, and And a buffer layer formed between the hole injection layers of the organic layer, wherein the buffer layer includes an inorganic compound for interfacial stabilization, a first organic compound for injecting holes into the organic layer, and a second organic compound for transporting holes to the organic layer. Characterized in that formed.

According to another aspect of the present invention, a method of manufacturing a light emitting display panel includes forming an anode on a substrate, forming a cathode forming an electric field with the anode, and forming an organic layer between the anode and the cathode; And forming a buffer layer between the anode and the hole injection layer of the organic layer, wherein the buffer layer includes an inorganic compound for interfacial stabilization, a first organic compound for injecting holes into the organic layer, and holes into the organic layer. It is characterized in that it is formed of a second organic compound for transporting.

The light emitting display panel and its manufacturing method according to the present invention has the following effects.

By forming a buffer layer between the anode and the hole injection layer, the inorganic compound of the buffer layer improves the stabilization and adhesion of the interface between the anode and the hole injection layer which is an organic material. In addition, the hole mobility is improved by the interfacial stabilization between the anode and the hole injection layer and the first and second organic compounds, thereby improving the low-voltage driving, lifetime, and luminous characteristics (IVL) for current / voltage. have.

Hereinafter, a light emitting display panel and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1A and 1B are cross-sectional views schematically illustrating an organic electroluminescent device according to the present invention.

The organic electroluminescent device shown in FIG. 1A is composed of an anode 148 and a cathode 170 formed on the substrate 100, and an organic layer formed between the anode 148 and the cathode 170. . The organic layer is a hole injection layer (HIL) 152, a hole transporting layer (HTL) 154, an emission layer (EML) 160, and an electron transporting layer (HIL) 152 sequentially from the anode 148. An electron transporting layer (ETL) 162 and an electron injection layer (EIL) 164 are formed. Here, an inorganic compound, a first organic compound, and a second organic compound are mixed between the anode 148 and the hole injection layer 152 to form a buffer layer 150 through vacuum thermal deposition. The inorganic compound is made of any one of LiF, NaF, KF, RbF, CsF, FrF, MgF 2, Caf 2, SrF 2 , or BaF _2. The first organic compound is a hole injection material, copper phthalocyanine (CuPc) or starburst amines TCTA, m-MTDATA or a soluble conductive polymer Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid: polyaniline / dodecylbenzene Sulfonic acid). The second organic compound is a hole transporting material, 4,4'-biscarbazolylbiphenyl, polyvinylcarbazole, m-biscarbazolylphenyl, 4,4'-biscarbazolyl-2,2'-dimethylbiphenyl , 4,4 ', 4 "-tri (N-carbazolyl) triphenylamine, 1,3,5-tri (2-carbazolylphenyl) benzene, 1,3,5-tris (2-carbazolyl-5 -Methoxyphenyl) benzene, bis (4-carbazolylphenyl) silane, N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] -4,4 ' Diamine (TPD), N, N'-di (naphthalen-1-yl) -N, N'-diphenyl benzidine (α-NPD), N, N'-diphenyl-N, N'-bis (1- Naphthyl)-(1,1'-biphenyl) -4,4'-diamine (NPB) poly (9,9-dioctylfluorene-co-N- (4-butylphenyl) diphenylamine) (poly (9,9-dioctylfluorene-co-N- (4-butylphenyl) diphenylamine) (TFB) or poly (9,9-dioctylfluorene-co-bis-N, N '-(4-butylphenyl) -bis -N, N'-phenyl-1,4-phenylenediamine) (poly (9,9-dioctylfluorene-co-bis-N, N ', (4-butylphenyl) -bis-N, N'-phenyl-1 , Consisting of any one of compounds consisting of 4-phenylenediamine (PFB) All.

HOMO energy levels of the first organic compound are 5.0 eV to 5.3 eV, and HOMO energy levels of the second organic compound are 5.3 eV to 5.5 eV.

The inorganic compound stabilizes the interface between the anode 148 and the hole injection layer 152 which is an organic material, the first organic compound serves as a hole injection into the organic layer, and the second organic compound serves as a hole transport to the organic layer. Do it.

The anode 148 may be formed of indium tin oxide (ITO), tin oxide (TO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO). It is formed of a transparent conductive material.

The cathode 170 is formed of a metal having high reflectance such as Al, Al / Li, Ma / Ag, Al / Nd, or the like.

In the organic electroluminescent device as shown in FIG. 1B, when a driving voltage is applied to the anode 148 and the cathode 170, an electric field is generated in the organic electroluminescent device such that electrons are formed in the cathode 170 and holes are formed in the anode 148. It is injected and emits light through a process of recombination in the light emitting layer 160. That is, in the organic layer, holes are injected into the light emitting layer 160 through the buffer layer 150, the hole injection layer 152, and the hole transport layer 154 formed on the anode 148 to transfer holes well, and the electrons are cathode 170. Electrons are injected into the light emitting layer 160 through the electron injection layer 164 and the electron transport layer 162 formed on the side of the substrate. When electrons and holes are injected into the emission layer 160, excitons are generated, and the excitons fall from the excited state to the ground state to generate visible light corresponding to the energy difference. In this way, the visible light generated from the emission layer 160 implements an image on the principle that the light exits through the transparent anode 148.

As such, by forming the buffer layer 150 between the anode 148 and the hole injection layer 152, the inorganic compound of the buffer layer 150 is used to form an interface between the anode 148 and the hole injection layer 152, which is an organic material. Improves stabilization and adhesion. In addition, the interfacial stabilization between the anode 148 and the hole injection layer 152 and the hole movement are excellent due to the first and second organic compounds. Accordingly, light emission characteristics with respect to low voltage driving, lifetime, and current / voltage IVL) can be improved.

2 is a cross-sectional view for describing a method of manufacturing the buffer layer 150 of the organic electroluminescent device.

2, a first crucible 190 containing an inorganic compound, a second crucible 192 containing a first organic compound, and a third crucible 1194 containing a second organic compound are respectively seated in the chamber 180. Let's do it. The substrate 100 having the anode 148 formed thereon is disposed to face the first to third crucibles 190, 192, and 193. The vacuum atmosphere of the chamber 180 has a vacuum degree of 1 × 10 ⁻⁶ Torr.

When each crucible 190, 192, 193 is heated, that is, each material is evaporated at a constant temperature and deposited on the anode 148 on the substrate 100. As a result, a buffer layer 150 having a thickness of 25 to 100 μs is formed in which the inorganic compound, the first organic compound, and the second organic compound each have a ratio of 2: 2: 1. At this time, each deposition rate during the deposition process also maintains a ratio of 2: 2: 1. For example, in the case of forming the buffer layer 150 having a thickness of 50 ms, the inorganic compound has a deposition rate of 0.2 ms / sec, the first organic compound is 0.2 ms / sec, and the second organic compound is 0.1 ms / sec. After that, the deposition process is performed for 10 seconds. Herein, the inorganic compound has a lower volatilization property than the hole injection material and the hole transport material, which are the first and second organic compounds, to perform the deposition process at a higher temperature than the hole injection material and the hole transport material. For example, the inorganic compound may be evaporated at 650 to 750 ° C., the first organic compound to 250 to 350 ° C., and the second organic compound to be deposited on the substrate 100. This deposition temperature is not limited to the above temperature, but may vary depending on the respective materials, the degree of vacuum, and the like.

3 is a table illustrating driving voltage, power efficiency, and lifespan of the organic EL device depending on the presence or absence of the buffer layer 150.

As shown in FIG. 3, in the case of the organic electroluminescent device having the buffer layer 150 (A), the driving voltage (V) It can be seen that the efficiency (lm / W) and the lifetime (T ₅₀ ) are improved. Here, as shown in FIG. 4, the lifetime is a time taken when the luminance decreases from 100% to 50%, that is, in the case of the organic electroluminescent device (B) in which the lifetime Hr is not formed in the buffer layer 150. It is 2500hr, and in the case of the organic electroluminescent device in which the buffer layer 150 is formed (A), the lifespan is improved to 3200hr.

By forming the buffer layer 150 between the anode 148 and the hole injection layer 152 in this manner, the inorganic compound of the buffer layer 150 forms an interface between the anode 148 and the hole injection layer 152 which is an organic material. Improves stabilization and adhesion. In addition, the interfacial stabilization between the anode 148 and the hole injection layer 152 and the hole movement are excellent due to the first and second organic compounds. Accordingly, light emission characteristics with respect to low voltage driving, lifetime, and current / voltage IVL) can be improved.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be apparent to those who have knowledge.

1A and 1B are cross-sectional views schematically illustrating an organic electroluminescent device according to the present invention.

2 is a cross-sectional view for describing a method of manufacturing a buffer layer of an organic electroluminescent device.

3 is a table showing driving voltage, power efficiency, and lifespan of an organic electroluminescent device depending on the presence or absence of a buffer layer.

4 is a graph showing the lifespan of an organic electroluminescent device with or without a buffer layer.

<Description of Symbols for Main Parts of Drawings>

100: substrate 148: anode

150 buffer layer 152 hole injection layer

154 hole transport layer 160 light emitting layer

162: electron transport layer 164: electron injection layer

170: cathode 180: chamber

190, 192, 194: Crucible

Claims (7)

An anode formed on the substrate, A cathode forming an electric field with the anode, An organic layer formed between the anode and the cathode; A buffer layer formed between the anode and the hole injection layer of the organic layer, The buffer layer is formed of an inorganic compound for interfacial stabilization, a first organic compound for injecting holes into the organic layer and a second organic compound for transporting holes to the organic layer. The method of claim 1, The inorganic compound, the first and the second organic compound is a light emitting display panel, characterized in that formed in a ratio of 2: 2: 1. The method of claim 1, The inorganic compounds are LiF, NaF, KF, RbF, CsF, FrF, MgF _{second, Caf. 2,} SrF _2, or BaF is formed in any of _two to one, wherein the first organic compound is copper phthalocyanine (CuPc) or a starburst (Starburst) It is formed of any one of the type amines TCTA, m-MTDATA or soluble conductive polymer Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid: polyaniline / dodecylbenzenesulfonic acid), the second organic compound is 4,4'-biscarba Zolylbiphenyl, polyvinylcarbazole, m-biscarbazolylphenyl, 4,4'-biscarbazolyl-2,2'-dimethylbiphenyl, 4,4 ', 4 "-tri (N-carbazolyl) tree Phenylamine, 1,3,5-tri (2-carbazolylphenyl) benzene, 1,3,5-tris (2-carbazolyl-5-methoxyphenyl) benzene, bis (4-carbazolylphenyl) silane, N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] -4,4'diamine (TPD), N, N'-di (naphthalen-1-yl ) -N, N'-diphenyl benzidine (α-NPD), N, N'-diphenyl-N, N'-bis (1-naphthyl)-(1,1'-biphenyl) -4,4 '-Diamine (NPB) poly (9,9-dioctylfluorene-co-N- (4-butylphenyl) diphenylamine) (poly (9,9-dioctylfluorene-co-N- (4-butylphenyl) diphenylamine) (TFB Or poly (9,9-dioctylfluorene-co-bis-N, N '-(4-butylphenyl) -bis-N, N'-phenyl-1,4-phenylenediamine) (poly (9 , 9-dioctylfluorene-co-bis-N, N ', (4-butylphenyl) -bis-N, N'-phenyl-1,4-phenylenediamine) (PFB) . Forming an anode on the substrate, Forming a cathode constituting an electric field with the anode; Forming an organic layer between the anode and the cathode; Forming a buffer layer between the anode and the hole injection layer of the organic layer, And the buffer layer is formed of an inorganic compound for interfacial stabilization, a first organic compound for injecting holes into the organic layer, and a second organic compound for transporting holes into the organic layer. The method of claim 4, wherein The inorganic compound, the first and the second organic compound is a method of manufacturing a light emitting display panel, characterized in that formed in a ratio of 2: 2: 1. The method of claim 4, wherein Forming the buffer layer, Providing a first crucible comprising said inorganic compound, a second crucible comprising said first organic compound, and a third crucible comprising said second organic compound, Mounting an anode formed on the substrate to face the first to third crucibles; The inorganic compound, the first and the second organic compound is a method of manufacturing a light emitting display panel comprising the step of depositing on the anode at a deposition rate of 2: 2: 1. The method of claim 4, wherein The inorganic compound is a method of manufacturing a light emitting display panel, characterized in that deposited at a higher temperature than the first and second organic compounds.

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