KR20050028564A - Efficient white organic light emitting devices with three primary colors and the fabrication of the same - Google Patents

Abstract

A structure and a fabrication method of an efficient white organic electroluminescence device with three primary colors are provided to accumulate 3 RGB colors of organic luminous layers, thereby emitting high-brightness white color over 3 wavelength areas of the RGB colors with few changes of color coordinates. A blue luminous layer(6) where electrons and holes are recombined together is formed. Green and red colors are doped on a partial area or entire areas of a hole transfer layer(4) and an electron transfer layer(8) located at an upper end and a lower end of the blue luminous layer(6). The blue luminous layer(6) is divided into three areas, and wherein a middle one of the three areas is 5 to 15nm in thickness while the red or green color is doped on upper/lower areas.

Description

Structure and manufacturing method of high efficiency three wavelength white organic electroluminescent device {Efficient White Organic Light emitting devices with three primary colors and the fabrication of the same}

The present invention relates to a structure and a manufacturing method of a white organic electroluminescent device, and more particularly, to a high efficiency, high brightness white organic electroluminescent device having a structure in which an organic light emitting layer having three primary colors of red green blue (RGB) is laminated.

Organic Electroluminescence (Organic EL), which uses an organic compound as a light emitting layer, can not only drastically reduce the driving voltage, but also it can easily be miniaturized, has low power consumption, and emits surface light. It is possible to emit light and tri-color light emission is easy, so research and development have been carried out as the next generation light emitting device. In particular, by optimizing the electrode type, the carrier injection efficiency from the electrode is increased, and the organic EL device having a laminated structure provided with a hole transport layer made of an aromatic diamine and a light emitting layer made of an aluminum complex of 8-hydroxyquinoline is provided. In comparison with the EL element using a single crystal such as anthracene or the like, the luminous efficiency was greatly improved.

In order to increase the life of the device, various kinds of materials are also searched. For example, porphyrin derivatives, phthalocyanine compounds, starburst-type aromatic triamines, hydrazone compounds, alkoxy substituted aromatic diamines as the material of the hole injection layer. Derivatives, p- (9-anthryl) -N, N-di-p-tolyl aniline, and the like have been developed and are approaching practicality.

In the case of producing a white light emitting device using the above low molecular weight organic material, a plurality of light emitting layers are generally laminated to obtain white color. The stacked structure of the white organic EL device can be classified into a three wavelength white organic EL device structure having a structure of laminating a layer emitting red light blue (RGB) and a two wavelength white organic EL device structure using a complementary color relationship. In the case of using complementary colors, a combination of blue / yellow or cyan / orange colors has been studied. However, it is easy to achieve high efficiency since light emission in a wavelength region with a relatively high visibility can be used as compared to the red-green-blue (RGB) three wavelength light emitting layer stacked type. However, the two-wavelength white organic EL device has an advantage of high efficiency. However, since white is obtained by using a complementary color relationship, it is disadvantageous to implement full color using a color filter. have. However, it was difficult to obtain a uniform spectrum of three colors due to the intermolecular energy transfer. In addition, a method of doping a plurality of light emitting dyes in the light emitting layer has many difficulties in terms of processes such as doping amount control and reproducibility.

It is therefore an object of the present invention to provide a method for solving the above problems of the prior art.

Another object of the present invention is to provide a structure and a manufacturing method of an organic electroluminescent device which emits light uniformly in three wavelength regions of red, green, and blue, and whose color coordinates are stable.

According to an aspect of the present invention for achieving the objects of the present invention as described above

Organic electricity including forming a blue light emitting layer in which electrons and holes are recombined, and doping some or all of the hole transport layer and the electron transport layer positioned at the top and bottom of the blue light emitting layer with green and red pigments. Disclosed is a method of manufacturing a light emitting device.

In addition, according to another aspect of the present invention, the process of forming a blue light emitting layer in which recombination of electrons and holes occurs, and the blue light emitting layer is divided into three areas to form a thickness of the middle region of 5 to 15nm, the top and bottom regions Disclosed is a method of manufacturing an organic electroluminescent device comprising a step of doping red or green pigments, respectively.

In addition, according to another aspect of the present invention, a process of forming a blue light emitting layer in which recombination of electrons and holes occurs, and a process of doping any one of red and green pigments in one region by dividing the blue light emitting layer into two regions And a thickness of an undoped region of the two regions is 5 to 15 nm, and the method of manufacturing an organic electroluminescent device comprising the step of doping a doped pigment and a dye having a different emission color to an organic layer in contact with the doped pigment. Is initiated.

Then, the structure of the white organic light emitting device manufactured by the above-described manufacturing method is provided.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that reference numerals and like elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In the following, the principles of the present invention will first be described. Next, embodiments according to the principles of the present invention will be described.

Principle of the Invention

In the prior art, one of the biggest problems in manufacturing a red-green-blue (RGB) three-wavelength type white organic EL device is that red, green, and blue color energy are sequentially generated from blue to green and green to red. It was difficult to make uniform light emission in the three wavelength region. In addition, electron-hole recombination occurs over several light emitting layers, and thus the color coordinate is not stable because the light emission spectrum is largely changed according to a change in driving voltage (or current density) or temperature. The principle of the present invention to solve these problems is to center the blue light emitting layer where the recombination of electrons and holes takes place, and at least the exciton energy transfer range (approximately 10 nm) in the organic layer above and below the layer of green and red Doping with a dye to emit light.

Therefore, the white light emitting organic EL device according to the principle of the present invention has a structure in which a light emitting layer of green / blue / red or red / blue / green is present. The electrons and holes injected from the cathode and anode electrodes, respectively, are recombined in the blue light emitting layer to form excitons, and transmit energy to adjacent green and red light emitting layers, thereby enabling excellent light emission in the red and green regions as well as blue.

In addition, the light emitting device according to the principles of the present invention is a light emitting layer located in the center, the thickness of the blue light emitting layer having a large energy band gap is greater than the energy transfer range of excitons (at least 5 nm, about 15 nm or less) excitons from the green light emitting layer to the red light emitting layer The energy transfer is solved by sequential blue-> green-> red energy. That is, in the conventional method, due to the sequential energy transition that occurs from blue to green and again from green to red, the blue and green light emitting layers have a lower luminous efficiency than the red color. It was solved through proper thickness control. In addition, in the conventional device structure, the light emitting layer of each color is 20 nm or more and has a thickness of at least 40 nm or more in order to form three light emitting layers. However, the light emitting device according to the principles of the present invention is characterized in that Recombination is performed, and red and green colors may be manufactured by doping a portion of the adjacent hole transport layer, thereby lowering a driving voltage at the same luminance, thereby improving luminous efficiency.

<Examples>

1 is a view showing the structure of a white organic light emitting diode according to a first embodiment of the present invention. In FIG. 1, the parts are marked for easy recognition, and are different from the actual film thickness.

Referring to FIG. 1, a transparent electrode 2 such as indium tin oxide (hereinafter, referred to as “ITO”) is used as an anode on the substrate 1, and a hole injection layer 3, a hole transport layer 4, and a red color are used as the anode. A light emitting layer 5a doped with a light emitting color, a blue light emitting layer 6, a light emitting layer 7a doped with a green light emitting color, an electron transporting layer 8, an electron injection layer 8, and a cathode 10 are sequentially formed. .

Here, glass or an amorphous thermoplastic resin is used as the material of the substrate 1 on which the organic light emitting element is formed. Examples of amorphous thermoplastic resins are AS resins, ABS resins, polypropylene (PP), polystyrene (HIPS), polymethyl methacrylic acid (PMMA), polycarbonate (PC) and polyoxymethylene (POM).

The hole injection layer 3 may be formed of a material such as PEDOT / PSS or copper phthalocyanine (hereinafter referred to as "Cu-PC"), 4,4 ', 4 "-tris (3-methylphenylphenylamino) triphenylamine (hereinafter referred to as m-MTDATA). Form about 5nm ~ 40nm.

As the hole transport layer 4, 4,4'-bis [N- (1-napthyl) -N-phenyl-amino] -biphenyl (hereinafter α-NPD) or N, N'-diphenyl-N, N'-bis A material such as (3-methyphenyl) -1,1'-biphenyl-4,4'-diamin (hereinafter referred to as 'TPD') is used at about 20 to 60 nm. The doped red light-emitting layer 5a has a hole transport layer as a host material and 4-Dicyanomethylene-2-methyl-6- [2- (2,3,6,7-tetrahydro-1H as a dopant). , 5H-benzo [ij] quinolizin-8-yl) viny] -4H-pyran) (hereinafter referred to as 'DCM2') or 5,6,11,12-tetraphenylnaphthacene (hereinafter referred to as 'Rubrene'), 4- ( dicyanomethylene) -2-t-butyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (hereinafter referred to as 'DCJTB'), Pt (II) Octaethylporphine (hereinafter referred to as 'PtOEP' Doping 0.1 to 10% of red pigment, etc.) and use about 0.5 to 10nm.

As the blue light emitting layer 6, a blue light emitting material such as 1,4-bis (2,2-diphenyl vinyl) benzene (hereinafter referred to as 'DPVBi') is used at about 4-20 nm, and the doped green light emitting layer 7a is The parent material is tris- (8-hydroxyquinoline) aluminum (hereinafter referred to as 'Alq3'), which is an electron transport layer, and Benzo [h] benzo [7,8] quino [2,3-b] acridine-7, Green pigments such as 16-dione, 9,18-dihydro (hereinafter referred to as 'Quinacridone'), Coumarin, and Ir (ppy) ₃ are doped by 0.1 to 10% and used at about 0.5 to 20 nm.

Alq3 is used as the electron transport layer 8 and the green light emitting layer, LiF is used as the electron injection layer 9, and a metal having a low work function, such as Al, Ca, Mg: Ag, is used as the cathode 10.

The structure of the materials used to fabricate the white light emitting device described above is as shown in Figures 2a to 2h. Here, FIG. 2A shows CuPC, FIG. 2B shows DPVBi, FIG. 2C shows α-NPD, FIG. 2D shows TPD, FIG. 2E shows Rubrene, FIG. 2F shows DCM2, FIG. 2G shows Alq3, and FIG. 2H shows Quinacridone.

The electroluminescence spectrum of the device according to the first embodiment of the present invention described above is as shown in FIG. 3A. Referring to FIG. 3A, the peaks of the spectrum appear at 472 nm, 506 nm and 562 nm, and the ClExy coordinates are (0.30, 0.37). 3B is a view showing quantum efficiency and luminous efficiency of a device according to a first embodiment of the present invention.

4 is a view showing the structure of a white organic light emitting diode according to a second embodiment of the present invention;

Referring to FIG. 4, in the structure of the second embodiment, the green and red dopants are doped into the hole transport layer 4 and the electron transport layer 8, respectively, in the basic structure of the first embodiment. Is a structure in which the doped light emitting layer is replaced. In the green and red dopants, Quinacridone and DCM2 were used as in the first embodiment.

The electroluminescence spectrum of the device according to the second embodiment of the present invention described above is as shown in FIG. 5A. Referring to FIG. 5A, the peaks of the spectrum appear at 472 nm, 498 nm, and 584 nm, and the ClExy coordinates are (0.33, 0.36). 5B is a diagram illustrating quantum efficiency and light emission efficiency of a device according to a second exemplary embodiment of the present invention.

6 is a view showing the structure of a white organic light emitting diode according to a third embodiment of the present invention;

Referring to FIG. 6, the structure of the third embodiment is a structure in which a yellow 5c and a red dopant 7c are doped into the hole transport layer 4 and the electron transport layer 8, respectively, around the blue light emitting layer 6. . Yellow and red dopants use Rubrene and DCM2, respectively.

Electroluminescence spectrum of the device according to the third embodiment of the present invention described above is as shown in Figure 7a. Referring to FIG. 7A, the peaks of the spectrum appear at 472 nm, 552 nm, and 592 nm, and the ClExy coordinates are (0.33, 0.36). 7B is a diagram illustrating quantum efficiency and light emission efficiency of a device according to a third exemplary embodiment of the present invention.

As described above, in each of the embodiments, the doping of the green, yellow, and red dopants in the hole transport layer 4 and the electron transport layer 8 around the blue light emitting layer irrespective of the doping position, respectively, is highly efficient in three wavelengths. It can be seen that a white organic light emitting device can be manufactured. By changing the type of dopant, the doping position, and the doping concentration, a three-wavelength white organic light emitting diode can be manufactured. Table 1 shows a result of comparing the characteristics of the white organic light emitting diode with respect to the structure according to each embodiment.

In Table 1, Device 1 refers to the structure according to the first embodiment, Device 2 refers to the structure according to the second embodiment, and Device 3 refers to the structure according to the third embodiment. The composition of materials in each device is as follows.

* Device 1

ITO / PEDOT: PSS / α-NPD (50nm) / α-NPD: DCM2 (5nm, 0.1%) / DPVBi (12nm) / Alq3: Quinacridone (5nm, 0.2%) / Alq3 (40nm) / LiF (0.5nm) / Al (120 nm)

* Device 2

ITO / PEDOT: PSS / α-NPD (50nm) / α-NPD: Quinacridone (5nm, 0.1%) / DPVBi (6nm) / Alq3: DCM2 (5nm, 0.2%) / Alq3 (40nm) / LiF (0.5nm) / Al (120 nm)

* Device 3

ITO / PEDOT: PSS / α-NPD (50nm) / α-NPD: Rubrene (5nm, 0.2%) / DPVBi (10nm) / Alq3: DCM2 (5nm, 0.3%) / Alq3 (40nm) / LiF (0.5nm) / Al (120 nm)

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention is an organic electroluminescent device structure capable of emitting white light having excellent efficiency over three wavelength regions of red, green, and blue, which are three primary colors. According to the present invention, unlike the conventional white light emitting organic electroluminescent device, there is little change in color coordinates according to current density or temperature, and emits white light of high luminance over three wavelength regions of red, green, and blue, and a driving voltage. It is low and is excellent in luminous efficiency characteristics.

1 is a view showing the structure of a white organic electroluminescent device according to a first embodiment of the present invention;

2A to 2H are structural diagrams of materials used for manufacturing a white organic light emitting diode;

3A is a view showing an electroluminescence spectrum of a device according to a first embodiment of the present invention;

3b is a view showing quantum efficiency and luminous efficiency of a device according to a first embodiment of the present invention;

4 is a view showing the structure of a white organic electroluminescent device according to a second embodiment of the present invention;

5A is a view showing an electroluminescence spectrum of a device according to a second embodiment of the present invention;

5B is a view showing quantum efficiency and luminous efficiency of a device according to a second embodiment of the present invention;

6 is a view showing the structure of a white organic light emitting diode according to a third embodiment of the present invention;

7A is a view showing an electroluminescence spectrum of a device according to a third embodiment of the present invention;

7B is a diagram illustrating quantum efficiency and light emission efficiency of a device according to a third exemplary embodiment of the present invention.

* Description of the main parts of the drawing *

1: substrate 2: anode

3: hole injection layer (HIL) 4: hole transport layer (HTL)

5: green and red light emitting layer 6: blue light emitting layer

7: red and green light emitting layer 8: electron transport layer (ETL)

9: electron injection layer (EIL) 10: cathode

Claims (6)

As a method of manufacturing an organic electroluminescent device, Forming a blue light emitting layer in which recombination of electrons and holes occurs; Method of manufacturing a white organic electroluminescent device comprising the step of doping the green and red pigments in part or all of the hole transport layer and the electron transport layer located on the top and bottom of the blue light emitting layer. As a method of manufacturing an organic electroluminescent device, Forming a blue light emitting layer in which recombination of electrons and holes occurs; The blue organic light emitting layer is divided into three regions, and the intermediate region has a thickness of 5 to 15 nm. Way. As a method of manufacturing an organic electroluminescent device, Forming a blue light emitting layer in which recombination of electrons and holes occurs; Dividing the blue light emitting layer into two regions and doping one of red and green pigments in one region; The thickness of the undoped region of the two regions is 5 to 15nm, and comprising the step of doping the doped pigment and a pigment of a different emission color to the organic layer in contact with the white organic electroluminescent device, characterized in that Manufacturing method. As a method of manufacturing an organic electroluminescent device, Forming a blue light emitting layer in which recombination of electrons and holes occurs; And forming a green light emitting layer and a red light emitting layer in a region within at least an exciton energy transfer range at the top and bottom of the blue light emitting layer. The white organic light emitting device manufactured by the method of any one of claims 1 to 4. In an organic electroluminescent device having a substrate, an anode electrode and a cathode electrode formed on the top of the substrate, A blue light emitting layer in which recombination of electrons and holes occurs, A hole transport layer doped with at least one of green, yellow and red pigments, A white organic electroluminescent device comprising an electron transport layer doped with any one of the pigments different from the doped color among green, yellow, and red, and at least one of the anode electrode and the cathode electrode is a transparent or translucent electrode.