KR100964228B1 - Organic light-emitting device and manufacturing method thereof - Google Patents

Abstract

The present invention is a metal reflective film; A first electrode; Buffer layer; Hole transport layer; Light emitting layer; Provided is an organic light emitting device, comprising: a second electrode; wherein the buffer layer includes a carbon-based compound; and the first electrode includes nitrogen (N). In the organic light emitting device of the present invention, the lifespan and progressive driving voltage increase suppression effect of the blue organic light emitting device is improved compared with the case of performing the UV or oxygen plasma treatment by performing nitrogen plasma treatment before forming the buffer layer on the first electrode. do.

Description

Organic light-emitting device and method for manufacturing same

The present invention relates to an organic light emitting device and a method of manufacturing the same, and more particularly, to an organic light emitting device and a method of manufacturing the improved driving voltage and lifetime characteristics.

The organic light emitting device is a self-luminous display device using a phenomenon in which light is generated by combining electrons and holes in an organic film when a current is applied to an organic film inserted between an anode and a cathode. It has the advantage of enabling the implementation of a lightweight, thin information display device having characteristics of the viewing angle. Such organic electroluminescent devices have been extended not only to mobile phones but also to other high quality information display devices.

Among the red, green, and blue, there is a problem in that the power consumption and life of the organic light emitting diode are increased due to the increase in the driving voltage of the blue organic light emitting diode. In order to solve this problem, a technique for forming a buffer layer between the anode and the hole transport layer has been proposed (Domestic Patent Publication 2006-0032099).

On the other hand, in the top-emitting organic light emitting device, a metal reflective film is formed on one surface of the anode in the aforementioned organic light emitting device, and oxygen plasma treatment or UV irradiation is performed on one surface of the anode on which the metal reflective film is not formed before the buffer layer is formed. It is common to undergo surface treatment.

However, in the case of performing the oxygen plasma treatment on one surface of the anode, in particular, the surface-treated organic light emitting diode having undergone the surface treatment, oxygen penetrates into the metal reflective film to form a metal oxide constituting the reflective film, thereby degrading the lifetime of the device and driving voltage. There is a lot of room for improvement.

The technical problem to be achieved by the present invention is to solve the above problems and to provide an organic light emitting device and a method of manufacturing the improved life and progressive driving voltage characteristics.

The technical problem is a metal reflective film; A first electrode; Buffer layer; Hole transport layer; Light emitting layer; A second electrode,

The buffer layer includes a carbon-based compound, and the first electrode includes nitrogen (N).

A hole injection layer may be further formed between the buffer layer and the hole transport layer.

Another technical problem of the present invention is to form a first electrode on the metal reflective film, and performing a nitrogen plasma treatment on the first electrode;

And a hole transport layer, a light emitting layer, and a second electrode sequentially formed on the nitrogen plasma treated product.

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

The organic light emitting device according to the present invention includes a metal reflective film, a first electrode, a buffer layer containing a carbon-based compound, a hole transport layer, a light emitting layer, and a second electrode, wherein the first electrode is nitrogen treated by nitrogen plasma treatment on the surface of the first electrode. (N). Due to such nitrogen plasma treatment, the surface of the first electrode is made uniform, thereby stabilizing the interface between the first electrode and the buffer layer. In this case, the progressive driving voltage increase refers to a phenomenon in which the driving voltage gradually increases during operation by applying a constant current to the organic light emitting diode.

The metal reflective film is made of a metal material having reflective characteristics such as silver (Ag) and aluminum (Al).

The thickness of the first electrode is 10-500 kPa, and the thickness of the metal reflective film is 100-5000 kPa.

As described above, when oxygen plasma treatment is performed on the surface of the first electrode having a thin film thickness according to the prior art, oxygen penetrates into silver oxide (AgO) when the metal reflective film is silver at the lower portion of the first electrode. The lifetime of the device and the progressive drive voltage characteristics are very degraded.

However, the present invention not only solves the problem of deterioration of characteristics due to oxidation of the metal reflective film by subjecting the surface of the first electrode to nitrogen plasma treatment before forming the buffer layer, but also controls the work function and surface characteristics of the first electrode by surface treatment. As a result, when the buffer layer containing the carbon-based compound is directly formed on the first electrode, a problem that is very difficult to uniformly apply may be solved.

The first electrode of the present invention is at least one selected from the group consisting of ITO (Iindium Tin Oxide), IZO (Iindium Zinc Oxide), nickel (Ni), platinum (Pt), gold (Au), iridium (Ir) and nitrogen It may contain (N), and may contain the compound produced by reaction between these as needed.

In the present invention, the nitrogen contained in the first electrode can be confirmed by an analytical method such as ion ooupled plasma-mass spectrometry (ICP-MS).

The organic light emitting device of the present invention may be a top emission organic light emitting device.

In the present invention, the nitrogen plasma treatment may use nitrogen gas as the plasma discharge gas, and may use a mixed gas of nitrogen, at least one gas selected from argon and hydrogen gas.

The nitrogen plasma treatment according to the present invention can be performed by the following non-limiting examples.

Into the RF plasma reactor, a first electrode with a metal reflection film, for example, an ITO film with an Ag film, was put therein, and a vacuum pump was used to extract a vacuum to a vibration (1 × 10 ^-6 torr) vacuum, followed by 10 to 30 sccm nitrogen MFC (Mass). After maintaining the vacuum degree for a predetermined time by flowing nitrogen using a flow controller, the RF output may be set using an RF generator and a regulator to generate nitrogen plasma. At this time, the plasma processing conditions include pressure, power, processing time, and flow rate. In the nitrogen plasma treatment according to the present invention, the range of the nitrogen plasma output is preferably 10 to 400W. If the range of nitrogen plasma output is less than 10W, the effect of nitrogen plasma treatment is insignificant. If the output exceeds 400W, the thickness of the first electrode is thin, which may damage the first electrode, which may lower the uniformity and electrode characteristics. In the case of lifespan is severely undesired.

1 is a cross-sectional view illustrating a structure of an organic light emitting diode according to an exemplary embodiment of the present invention.

Referring to this, a first electrode 10 is formed on the metal reflective film 17 made of silver (Ag), a buffer layer 11 is formed on the first electrode 10, and a hole transport layer (above). 12), the light emitting layer 13, the electron transport layer 14 and the electron injection layer 15 are sequentially formed. The second electrode 16 is formed on the electron injection layer 15.

The surface of the first electrode 10 is stabilized by the nitrogen plasma treatment, so that the interface property between the first electrode 10 and the buffer layer 11 is stabilized, thereby improving the service life and the progressive driving voltage characteristics. That is, for example, when the first electrode is ITO, the oxygen distribution on the surface of the ITO is replaced with a small amount of nitrogen by the nitrogen plasma treatment, thereby reducing the possibility of oxidation of the metal reflective film, thereby explaining that the interfacial characteristics are stabilized. In addition, although not shown in the drawings, hole blocking may be further stacked, and in addition, an intermediate layer may be further formed to improve interfacial properties between the layers.

Hereinafter, a method of manufacturing the top-emitting organic light emitting diode according to the present invention will be described. For convenience, the method of manufacturing the organic light emitting diode of FIG. 1 will be described as an example.

First, the reflective film 17 is formed on the substrate (not shown). At this time, at least one selected from silver (Ag) and aluminum (Al) is used as the material for forming the metal reflective film 17, and the thickness of the reflective film is preferably 100 to 5000 kPa. If the thickness of the reflective film is out of the above range, the processability and the like are lowered, which is not preferable.

Subsequently, a patterned first electrode 10 is formed on the metal reflective layer 17. Here, the substrate is a substrate used in a conventional organic electroluminescent device, preferably a glass substrate or a transparent plastic substrate excellent in transparency, surface flatness, ease of handling and waterproof. And the thickness of the substrate is preferably 0.3 to 1.1 mm.

The first electrode 10 may be formed of a conductive metal or an oxide thereof that facilitates hole injection. Specific examples thereof include indium tin oxide (ITO), indium zinc oxide (IZO), nickel (Ni), and platinum. (Pt), gold (Au), iridium (Ir) and the like are used. In the present invention, in particular, ITO is used as an example.

After cleaning the substrate on which the first electrode 10 is formed, nitrogen plasma treatment is performed. At this time, an organic solvent such as isopropanol (IPA) or acetone is used as the washing method. The nitrogen plasma treatment conditions are as described above. By depositing a carbon-based compound on the nitrogen plasma treated first electrode 10 to form a buffer layer 11 to a thickness of 1 to 100Å.

As the carbon-based compound, one or more selected from the group consisting of fullerenes, metal-containing fullerene-based complexes, carbon nanotubes, carbon fibers, carbon black, graphite, carbines, MgC60, SrC60, CaC60, and C60 may be used. Preference is given to using.

Subsequently, the hole transport material 12 is vacuum-deposited or spin-coated on the buffer layer 11 to form the hole transport layer 12.

The hole transport material is not particularly limited, and 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, N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine: α-NPD) Etc. are used.

It is preferable that the thickness of a positive hole transport layer is 10-3000 GPa here. If the thickness of the hole transport layer is less than 10 kV, the hole transport capacity is too thin, and if the hole transport layer is more than 3000 kV, it is not preferable because of the increase in driving voltage.

[Formula 4]

A hole injection layer may be further formed between the buffer layer and the hole transport layer. However, the improvement of the device characteristics depends on the device structure. The hole injection material is not particularly limited, and copper phthalocyanine (CuPc) or starburst type amines such as TCTA and m-MTDATA may be used as the hole injection layer.

(3)

The emission layer 13 is formed on the hole transport layer 12 formed by the above process.

The light emitting layer material is a conventionally used one, and is not particularly limited. Specific examples thereof include aluminum complexes such as Alq3 (tris (8-quinolinolato) -aluminium), BAlq, SAlq, Almq3, gallium complexes (e.g. Gaq ' ₂ OPiv, Gaq' ₂ OAc, 2 (Gaq ' ₂ )), fluorene polymers, polyparaphenylene vinylene or derivatives thereof, biphenyl derivatives And spiro polyfluorene polymers.

     Alq3 BAlq

    SAlq Almq3

Gaq ' ₂ OPiv Gaq' ₂ OAc, 2 (Gaq'2)

In the present invention, the thickness of the light emitting layer 13 is preferably 300 to 500 kPa. If the thickness range of the light emitting layer is determined, the case of 150 to 600 kPa is most preferable. The thicker the light emitting layer, the higher the driving voltage is.

Although not shown in FIG. 1, a hole blocking layer may be selectively formed by vacuum deposition or spin coating a hole blocking material on the light emitting layer 13. The hole blocking material used in this case is not particularly limited, but should have ionization potential higher than that of the light emitting compound while having electron transport ability, and typically, Balq, BCP, TPBI, and the like are used. If the thickness of the hole blocking layer is preferably 30 to 70 kPa. If the thickness of the hole blocking layer is less than 30 kW, the hole blocking property may not be well implemented, and if the hole blocking layer is more than 70 kW, it is not preferable to increase the driving voltage.

Subsequently, the electron transporting material 14 is vacuum deposited or spin coated on the light emitting layer 13 to form the electron transporting layer 14. The electron transporting material is not particularly limited and Alq 3 may be used.

In the present invention, the carbon compound may be doped into the hole injection layer and / or the hole transport layer or the electron transport layer together with the buffer layer of the carbon compound formed between the anode and the hole injection layer. That is, when the buffer layer of the carbon compound is formed between the anode and the hole injection layer, and the hole injection layer and / or the hole transport layer or the electron transport layer are formed, the carbon compound is vacuum-deposited together with the hole injection material and / or the hole transport material. It can be formed by co-deposition. In this case, the content of the carbon-based compound is 0.005 to 99.95 parts by weight based on 100 parts by weight of the total weight of each of the hole injection layer, the hole transport layer, or the electron transport layer. If the content of the carbon-based compound is less than 0.005 parts by weight, the effect on the improvement of the characteristics of the organic EL device is insignificant, which is not preferable.

In the case of the electron transport layer 14, the thickness is preferably 150 to 600 kPa. If the thickness of the electron transporting layer is less than 150 kV, the electron transporting capacity is lowered.

In addition, an electron injection layer 15 may be stacked on the electron transport layer 24. As the electron injection layer forming material, materials such as LiF, NaCl, CsF, Li ₂ O, BaO, and Liq can be used. It is preferable that the thickness of the said electron injection layer is 5-20 GPa. If the thickness of the electron injection layer is less than 5 kV, the electron injection layer may not serve as an effective electron injection layer.

Subsequently, the organic light emitting device is completed by forming a cathode as the second electrode 16 by vacuum thermal evaporation of a cathode metal as the second electrode on the electron injection layer.

The cathode metal is lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag ) And the like are used.

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited only to the following examples.

Example  One

A 1000 mm thick silver (Ag) film and a 100 mm thick ITO film were sequentially formed on the glass substrate, the glass substrate was washed with distilled water, and then ultrasonically cleaned in isopropyl alcohol and pure water for 5 minutes, followed by vacuum. Dry in oven for 1 hour.

The resultant was transferred to a nitrogen plasma treatment apparatus, and plasma treatment was performed on the substrate for 2 minutes under a condition of 40 W at a pressure of 30 mtorr using nitrogen plasma, and then the substrate was transferred to a vacuum evaporator.

C60 was vacuum-deposited on the substrate to form a buffer layer having a thickness of 30 μm, and then NPB was vacuum-heat-deposited on the buffer layer to form a hole transport layer having a thickness of 200 μm.

Blue light emitting layer by mixing a concentration of 2 wt% perylene (Perylene) as a dopant in DPVBi (4,4'-bis (2,2'-diphenyl vinyl) -1,1'-biphenyl) as a host on the hole transport layer Was formed to a blue light emitting layer to a thickness of 200 kHz. Subsequently, Alq3, which is an electron transporting material, was deposited on the emission layer to form an electron transporting layer having a thickness of 250 Å.

LiF 10 Å (electron injection layer) and Mg: Ag 500 Å (cathode) were sequentially vacuum deposited on the electron transport layer to form a LiF / Mg: Ag electrode, thereby manufacturing a top emission type organic light emitting device. At this time, the atomic ratio of MgAg may be any range as long as it can act as a cathode, and is 9: 1 to 1: 9, preferably 8: 2 to 2: 8.

Comparative example  One

Except for performing a UV treatment process described later instead of nitrogen plasma treatment, it was carried out in the same manner as in Example 1 to prepare a top-emitting organic light emitting device.

Comparative example  2

Except that the C60 was vacuum-deposited on the ITO film to form a buffer layer having a thickness of 30 kPa without the nitrogen plasma treatment, and the hole injection layer was formed to have a thickness of 1000 kPa by vacuum thermal evaporation of NPB on the buffer layer. A light emitting organic light emitting diode was manufactured by the same method as in (1).

In the organic light emitting diode according to Example 1 and Comparative Examples 1-2, the accelerated life was evaluated and the results are shown in FIG. In this case, the acceleration life was applied to a constant current of 20mA to evaluate the rate of decrease in luminance over time. FIG. 2 shows a luminance reduction rate with time when a constant current is applied at 20 mA, in which the x-axis unit represents time (hr) and the y-axis unit represents luminance reduction rate (%).

Referring to FIG. 2, it can be seen that the front emission type organic light emitting diode according to Example 1 has an improved acceleration life compared to that of Comparative Example 1 and Comparative Example 2.

In the top emission type organic light emitting diode according to Example 1 and Comparative Examples 1-2, the amount of change in the progressive driving voltage was evaluated and the results are shown in FIG. 3. Here, the progressive driving voltage variation is a measure of the variation of the driving voltage according to the decrease in luminance during the constant current application. 3 is a graph showing the amount of change in driving voltage according to time when a constant current is applied to 20 mA, in which the x-axis unit represents a time (hr) and the y-axis unit represents a drive voltage variation (Voltage, V).

Referring to FIG. 3, it was confirmed that the organic light emitting diode according to Example 1 was suppressed from increasing the progressive driving voltage as compared with those of Comparative Examples 1 and 2.

The organic light emitting device according to the present invention has a life improvement and a progressive driving voltage increase suppression effect of the blue organic light emitting device as compared with the UV or oxygen plasma treatment by performing nitrogen plasma treatment before forming the buffer layer on the first electrode. have.

Although the present invention has been described with reference to the embodiments shown in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a cross-sectional view showing the structure of a top-emitting organic light emitting diode according to an embodiment of the present invention.

2 is a graph illustrating an evaluation of an accelerated lifetime in a top emission organic light emitting diode according to Example 1 and Comparative Examples 1-2 of the present invention.

3 is a graph illustrating an evaluation of a driving voltage variation in the top emission organic light emitting diode according to Example 1 and Comparative Examples 1-2 of the present invention.

<Brief description of the major symbols in the drawings>

10 ... first electrode 11 ... buffer layer

12 .. Hole transport layer 13 ... Light emitting layer

14 .. electron transport layer 15 .... electron injection layer

16. Second electrode 17 ... Metal reflective film

Claims (10)

Metal reflective film; A first electrode; Buffer layer; Hole transport layer; Light emitting layer; Electron transport layer; Electron injection layer; A second electrode, The buffer layer comprises a carbon-based compound, The first electrode includes nitrogen (N), The thickness of the first electrode is 50 to 100Å, And the metal reflective film comprises at least one metal selected from silver (Ag) and aluminum (Al). delete delete The method of claim 1, wherein the first electrode is one selected from the group consisting of indium tin oxide (ITO), indium zinc oxide (IZO), nickel (Ni), platinum (Pt), gold (Au), and iridium (Ir). The organic light emitting device comprising the above and nitrogen (N). The method of claim 1, wherein the carbon-based compound is at least one selected from the group consisting of fullerenes, metal-containing fullerene complexes, carbon nanotubes, carbon fibers, carbon black, graphite, carbine, MgC60, SrC60, CaC60, C60 An organic light emitting element. The organic light emitting device of claim 1, further comprising a hole injection layer formed between the buffer layer and the hole transport layer. The organic light emitting device of claim 1, further comprising a hole blocking layer between the light emitting layer and the electron transport layer. Forming a first electrode on the metal reflective film, and performing nitrogen plasma treatment on the first electrode; A buffer layer, a hole transport layer, and a light emitting layer on the nitrogen plasma treated product; Electron transport layer; Electron injection layer; A method of manufacturing an organic light emitting device, comprising the steps of sequentially forming a second electrode, the organic light emitting device of any one of claims 1, 4 to 7. delete delete

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