KR102277563B1 - White organic light emitting device - Google Patents

Abstract

The present invention discloses a white organic light emitting device. The disclosed white organic light emitting device of the present invention includes: a first electrode and a second electrode facing each other on a substrate; a first stack in which a hole injection layer, a first hole transport layer, a first emission layer, and a first electron transport layer are sequentially stacked between the first electrode and the second electrode; a second stack in which a second hole transport layer, a second emission layer, a third emission layer, a second electron transport layer, and an electron injection layer are sequentially stacked between the first stack and the second electrode; and a charge generation layer formed between the first stack and the second stack to control a charge balance between the stacks, and the first light emitting layer of the first stack is formed of a fluorescent blue light emitting layer having an emission peak of 1-Peak. and the second light emitting layer and the third light emitting layer of the second stack have an emission peak of 2-Peak and are formed in contact with each other, and any one of the second light emitting layer and the third light emitting layer is a phosphorescent green light emitting layer or a phosphorescent yellow green light emitting layer is formed, and the other is formed of a phosphorescent red light emitting layer.
Accordingly, in the white organic light emitting device according to the present invention, the light emitting layer of the white organic light emitting device including the first stack and the second stack is formed to have an emission peak of 3-Peak, and in the light emitting layer of the second stack adjacent to the hole transport layer By using the material of the hole transport layer as a host, hole injection is facilitated, and by optimizing the thickness and doping concentration of the light emitting layer of the second stack, power consumption can be improved, and panel efficiency and color gamut can be improved.

Description

White organic light emitting device

The present invention relates to an organic light emitting device, and more particularly, to provide a white organic light emitting device capable of improving characteristics of efficiency and color reproducibility or increasing power consumption.

Recently, as we enter the information age in earnest, the field of display that visually expresses electrical information signals has developed rapidly, and in response to this, various flat panel display devices ( Flat Display Device) has been developed and is rapidly replacing the existing cathode ray tube (CRT).

Specific examples of the flat panel display include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an organic light emitting display device. (Organic Light Emitting Device: OLED) etc. are mentioned.

Among them, an organic light emitting diode display is considered as a competitive application for compactness and vivid color display without requiring a separate light source.

In such an organic light emitting display device, it is essential to form an organic light emitting layer, and a deposition method using a shadow mask is used to form the organic light emitting layer in the related art.

However, in the case of a large area, the shadow mask sags due to its load, making it difficult to use it several times, and an alternative method is required because a defect occurs in the formation of the organic light emitting layer pattern.

A white organic light emitting diode display is one of several methods that have been proposed to replace the shadow mask.

Hereinafter, a white organic light emitting diode display will be described.

The white organic light emitting diode display is characterized in that each layer between the anode and the cathode is deposited without a mask when the light emitting diode is formed, and organic layers having different components including the organic light emitting layer are sequentially deposited in a vacuum state. Such a white organic light emitting display device is a device used for various purposes, such as a thin light source, a backlight of a liquid crystal display device, or a full color display device employing a color filter.

These days, a white organic light emitting diode display uses a puppet light stack structure in which a first stack using a blue fluorescent device as a light emitting layer and a second stack structure using a yellow-green phosphor as a light emitting layer are stacked. is becoming In such a white organic light emitting device, white light is realized by a mixing effect of blue light emitted from a blue fluorescent device and yellow light emitted from a yellow phosphorescent device.

The white organic light emitting display device having the doll light stack structure needs to improve luminous efficiency and color gamut when white light is emitted, and to improve power consumption.

The present invention provides a white organic light emitting device in which a light emitting layer of a white organic light emitting device including a first stack and a second stack or a white organic light emitting device including the first to third stacks is formed to have an emission peak of 3-Peak but it has a purpose.

Another object of the present invention is to provide a white organic light emitting device that facilitates hole injection by using the material of the hole transport layer as a host in the light emitting layer of the second stack adjacent to the hole transport layer.

Another object of the present invention is to provide a white organic light emitting device that improves power consumption and improves panel efficiency and color gamut by optimizing the thickness and doping concentration of the light emitting layer of the second stack of the present invention.

The present invention provides a white organic light emitting device that increases the red luminance achievement rate and increases the color gamut by forming the light emitting layer of the second stack of the white organic light emitting device including the first to third stacks in a double light emitting layer structure. There is another purpose.

In order to solve the problems of the prior art as described above, a white organic light emitting device of the present invention includes: a first electrode and a second electrode facing each other on a substrate; a first stack in which a hole injection layer, a first hole transport layer, a first emission layer, and a first electron transport layer are sequentially stacked between the first electrode and the second electrode; a second stack in which a second hole transport layer, a second emission layer, a third emission layer, a second electron transport layer, and an electron injection layer are sequentially stacked between the first stack and the second electrode; and a charge generation layer formed between the first stack and the second stack to control a charge balance between the stacks, and the first light emitting layer of the first stack is formed of a fluorescent blue light emitting layer having an emission peak of 1-Peak. and the second light emitting layer and the third light emitting layer of the second stack have an emission peak of 2-Peak and are formed in contact with each other, and any one of the second light emitting layer and the third light emitting layer is a phosphorescent green light emitting layer or a phosphorescent yellow green light emitting layer is formed, and the other is formed of a phosphorescent red light emitting layer.

In the white organic light emitting device according to the present invention, the light emitting layer of the white organic light emitting device including the first stack and the second stack or the white organic light emitting device including the first to third stacks has an emission peak of 3-Peak. There is a first effect of being

In addition, the white organic light emitting device according to the present invention has a second effect of facilitating hole injection by using the material of the hole transport layer as a host in the light emitting layer of the second stack adjacent to the hole transport layer.

In addition, the white organic light emitting device according to the present invention has a third effect of improving power consumption and improving panel efficiency and color gamut by optimizing the thickness and doping concentration of the light emitting layer of the second stack.

In addition, in the white organic light emitting device according to the present invention, the light emitting layer of the second stack of the white organic light emitting device including the first stack to the third stack is formed in a double light emitting layer structure, thereby increasing the red luminance achievement rate and increasing the color gamut. There is a fourth effect that makes

1 is a view showing a white organic light emitting diode according to a first embodiment of the present invention.
2 is a view showing experimental results comparing the conventional white organic light emitting device and the white organic light emitting device of the present invention.
3 is a view showing emission wavelengths and intensity of a conventional white organic light emitting device and a white organic light emitting device of the present invention.
4 is a view showing experimental results according to the ratio of the host of the green light emitting layer of the second stack of the present invention.
5 is a view showing experimental results according to the host ratio of the red light emitting layer of the second stack of the present invention.
6 is a diagram illustrating experimental results according to a doping ratio of a green light emitting layer of a second stack of the present invention.
7 is a diagram illustrating a white organic light emitting diode according to a second exemplary embodiment of the present invention.
8 is a view showing emission wavelength and intensity of a conventional white organic light emitting device and a white organic light emitting device of the present invention.
9 is a view showing experimental results comparing the conventional white organic light emitting device and the white organic light emitting device of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And in the drawings, the size and thickness of the device may be exaggerated for convenience. Like reference numerals refer to like elements throughout.

1 is a view showing a white organic light emitting diode according to a first embodiment of the present invention.

Referring to FIG. 1 , in the white organic light emitting diode of the present invention, a first electrode 110 and a second electrode 130 facing each other are formed on a substrate 100 . Between the first electrode 110 and the second electrode 130 , a first stack 200 , a charge generation layer 120 , and a second stack 300 are disposed on the first electrode 110 . These are sequentially stacked and formed. The first stack 200 and the second stack 300 each include light-emitting layers of different colors, and light of different colors emitted from the light-emitting layers of each stack is mixed to realize white light.

The substrate 100 may include a thin film transistor formed on an insulating substrate, wherein the insulating substrate is formed of insulating glass, metal, plastic, polyimide (PI), or the like, and the thin film transistor includes a gate electrode, a semiconductor layer, It consists of a source electrode and a drain electrode.

The first electrode 110 may be formed of a transparent conductive material as an anode, and may include, for example, any one selected from the group consisting of Indum Tin Oxide (ITO), Indum Zinc Oxide (IZO), and ZnO. .

The second electrode 130 may be formed of a metal material as a cathode, and for example, a group consisting of Mg, Ca, Al, Al-alloy, Ag, Ag-alloy, Au, and Au-alloy having a low work function. It may include any one selected from.

The charge generating layer 120 is formed between the first stack 200 and the second stack 300 to supply electrons to the first stack 200 and holes to the second stack 300, Controls the charge balance between each stack. The charge generation layer 120 may be formed as a thin metal layer such as aluminum (Al) or as a single layer using a transparent electrode such as indum tin oxide (ITO), so that the device configuration is simple and manufacturing is easy. In addition, it may be formed as a plurality of layers, which is a junction structure of an organic material layer by impurity doping.

When it is formed in a plurality of layers, it is advantageous in improving efficiency and prolonging life by forming suitable for electron transport and hole transport, respectively. In this case, a region of the charge generation layer 120 in contact with the first stack 200 may be N-type doped to facilitate electron supply. In addition, a region in contact with the second stack 300 may be formed by P-type doping to facilitate hole supply.

The first stack 200 includes a hole injection layer (HIL) 202 and a first hole transport layer (HTL) 203 between the first electrode 110 and the charge generation layer 120 . ), a first light emitting layer 204 and a first electron transport layer (ETL) 205 are sequentially stacked.

The hole injection layer HIL may be formed of a material having excellent hole injection capability, and may be doped with P-type doping to facilitate hole injection.

The first emission layer 204 is a fluorescent blue emission layer and may be formed as a single emission layer having an emission peak of 1-Peak. In this case, the first light emitting layer 204 may be formed by doping one host with a fluorescent blue dopant, or by doping two hosts with a fluorescent blue dopant. The fluorescent blue dopant of the first emission layer 204 is formed of a dopant having a wavelength band of an emission peak in a range of 420 nm to 490 nm.

The second stack 300 includes a second hole transport layer (HTL) 302 , a second emission layer 303 , and a third emission layer 304 between the charge generation layer 120 and the second electrode 130 . ), a second electron transport layer (ETL) 305 and an electron injection layer (EIL) 306 are sequentially stacked.

The electron injection layer EIL may be formed of a material having excellent electron injection capability, and may be doped with N-type doping to facilitate electron injection.

The second stack 300 is formed by contacting the second light emitting layer 303 and the third light emitting layer 304 without a charge generating layer or a buffer layer therebetween. In addition, the second light-emitting layer 303 and the third light-emitting layer 304 are stacked to form one second stack light-emitting layer 301 .

The second stack emission layer 301 may be formed by stacking a phosphorescent red emission layer and a phosphorescent green emission layer to form a dual emission layer having an emission peak of 2-Peak. In addition, the second stack light emitting layer 301 may be formed by stacking a phosphorescent red light emitting layer and a phosphorescent yellow green light emitting layer.

That is, when the second light emitting layer 303 is a phosphorescent red light emitting layer, the third light emitting layer 304 is formed of a phosphorescent green light emitting layer or a phosphorescent yellow green light emitting layer. Alternatively, when the second light emitting layer 303 is a phosphorescent green light emitting layer or a phosphorescent yellow green light emitting layer, the third light emitting layer 304 is formed of a phosphorescent red light emitting layer. Preferably, the second light-emitting layer 303 may be formed of a phosphorescent red light-emitting layer, and the third light-emitting layer 304 may be formed of a phosphorescent green light-emitting layer.

The phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is formed of a phosphorescent green dopant or a phosphorescent yellow green dopant having a wavelength band of an emission peak in a range of 500 nm to 580 nm, and the phosphorescent red emission layer has a wavelength band of an emission peak in a range of 580 nm to 680 nm. It is formed of a phosphorescent red dopant having Also, the dopant doping ratio of the phosphorescent green emission layer or the phosphorescent yellow green emission layer may be higher than that of the phosphorescent red emission layer.

In addition, the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer may be formed to have a thickness greater than that of the phosphorescent red light emitting layer. Preferably, the thickness of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer may be three times the thickness of the phosphorescent red light emitting layer.

The second light emitting layer 303 is formed by being stacked in contact with the second hole transport layer 302 , and includes a phosphorescent red dopant, a phosphorescent green dopant, or a phosphorescent yellow green dopant on two hosts. (dopant) may be formed by doping. The two hosts may include a hole type host and an electron type host. In this case, the hole host may be formed in 20% to 80% by volume of the total host, and the electron host may be formed in 80% by volume to 20% by volume of the entire host.

Also, the hole host may be formed of the same material as the second hole transport layer 302 . When the host includes a hole host and the hole host is formed of the same material as the second hole transport layer 302 , injection of holes into the light emitting layer may be facilitated.

The third light emitting layer 304 is formed on the second light emitting layer 303, and two hosts are doped with a phosphorescent green dopant, a phosphorescent yellow green dopant, or a phosphorescent red dopant. can be formed. In this case, the two hosts may include a hole type host and an electron type host. In this case, the hole host may be formed in 20% to 80% by volume of the total host, and the electron host may be formed in 80% by volume to 20% by volume of the entire host.

In addition, the third light emitting layer 304 may be formed by doping one host with a phosphorescent green dopant, a phosphorescent yellow green dopant, or a phosphorescent red dopant. In this case, the one host is formed as a bipolar host.

When the first stack 200 is formed as a fluorescent unit in a configuration adjacent to the anode and the second stack 300 is formed as a phosphorescent unit in a configuration adjacent to the cathode, luminous efficiency may be higher.

In addition, in order to improve power consumption and panel efficiency of the white organic light emitting diode, it is necessary to optimize the host ratio of the second and third light emitting layers, the thickness of each light emitting layer, and the doping concentration.

2 is a view showing experimental results comparing the conventional white organic light emitting device and the white organic light emitting device of the present invention.

3 is a view showing emission wavelengths and intensity of a conventional white organic light emitting device and a white organic light emitting device of the present invention.

2 and 3 , the panel efficiency and color gamut of 2-Peak including a blue light emitting layer in a conventional first stack and a yellow-green light emitting layer in a second stack and the present invention It is an experimental result comparing panel efficiency and color gamut of 3-Peak including a blue light emitting layer in the first stack according to , and a red light emitting layer and a green light emitting layer in the second stack. 2 and 3, the 3 Peak reddish is a configuration in which the red emission peak (B) intensity is greater than the 3 Peak greenish, and the 3 Peak greenish is the green emission peak (A) intensity ( intensity) is formed largely.

Comparing Experiment I, Experiment II, and Experiment IV, it can be seen that the white organic light emitting diode of the present invention is superior to the conventional white organic light emitting diode in color reproducibility by 10% or more. In particular, 3 peak greenish is characterized in that color gamut can be improved without reducing panel efficiency. In addition, comparing Experiment I and Experiment V, it can be seen that the white organic light emitting device of the present invention has the characteristics of improving panel efficiency at the same color reproducibility and thus power consumption as compared to the conventional white organic light emitting device. have.

That is, the present invention has an effect of improving color gamut or improving panel efficiency and power consumption compared to the conventional invention. In particular, it can be seen that the greater the intensity of the green emission peak A is, the greater the effect is.

Although not shown in the drawings, as the thickness of the red or green emission layer increases, the red emission peak (B) and the green emission peak (A) are formed to be higher, respectively. As discussed in FIG. 2 , as the intensity of the green light emitting peak A increases, panel efficiency and color gamut are further improved, so the thickness of the green light emitting layer may be preferably formed to be thicker than the thickness of the red light emitting layer. More preferably, the thickness of the green light emitting layer may be three times the thickness of the red light emitting layer.

4 is a view showing experimental results according to the ratio of the host of the green light emitting layer of the second stack of the present invention.

Referring to FIG. 4 , the green light emitting layer of the second stack is formed by doping the electron host and the hole host with a green dopant. 4 is a diagram illustrating a green emission peak (A) and a red emission peak (B) of the second stack according to the volume ratio of the electron host and the hole host of the green emission layer.

When the conditions of the red emission layer are the same, when the volume ratio of the hole host of the green emission layer is greater than that of the electron host, the intensity of the green emission peak (A) is the highest and the intensity of the red emission peak (B) is the lowest. do. In addition, it can be seen that when the volume ratio of the hole host is smaller than that of the electron host, the intensity of the green emission peak (A) is the lowest and the intensity of the red emission peak (B) is the highest. As discussed in FIG. 2 , as the intensity of the green emission peak A increases, panel efficiency and color gamut are further improved. Therefore, the volume ratio of the hole host and the electron host is formed so that the intensity of the green emission peak (A) is high in order to include an improved effect compared to the related art.

5 is a view showing experimental results according to the ratio of the host of the red light emitting layer of the second stack of the present invention.

Referring to FIG. 5 , the red light emitting layer of the second stack is formed by doping the electron host and the hole host with a red dopant. 5 is a diagram illustrating a green emission peak (A) and a red emission peak (B) of the second stack according to the volume ratio of the electron host and the hole host of the red emission layer.

When the conditions of the green emission layer are the same, when the volume ratio of the hole host of the red emission layer is greater than that of the electron host, the intensity of the green emission peak (A) is the highest and the intensity of the red emission peak (B) is the lowest. do. In addition, it can be seen that when the volume ratio of the hole host is smaller than that of the electron host, the intensity of the green emission peak (A) is the lowest and the intensity of the red emission peak (B) is the highest. As discussed in FIG. 2 , as the intensity of the green emission peak A increases, panel efficiency and color gamut are further improved. Therefore, the volume ratio of the hole host and the electron host is formed so that the intensity of the green emission peak (A) is high in order to include an improved effect compared to the related art.

6 is a diagram illustrating experimental results according to a doping ratio of a green light emitting layer of a second stack of the present invention.

Referring to FIG. 6 , the green light emitting layer of the second stack is formed by doping a host with a green dopant. 6 is a diagram illustrating a green emission peak (A) and a red emission peak (B) of the second stack according to the doping ratio of the green dopant of the green emission layer.

As shown in FIG. 6 , it can be seen that as the doping ratio of the green dopant increases, the intensity of the green emission peak A increases. In addition, although not shown in the drawings, the red emission layer of the second stack is also formed so that the intensity of the red emission peak B increases as the doping ratio of the red dopant increases. Accordingly, as discussed in FIG. 2 , as the intensity of the green emission peak A increases, panel efficiency and color gamut are further improved. Preferably, the doping ratio of the green dopant of the green emission layer is the red dopant of the red emission layer. It may be formed to be larger than the doping ratio of .

7 is a diagram illustrating a white organic light emitting diode according to a second exemplary embodiment of the present invention.

Referring to FIG. 7 , in the white organic light emitting diode of the present invention, a first electrode 110 and a second electrode 130 facing each other are formed on a substrate 100 . Between the first electrode 110 and the second electrode 130, on the first electrode 110, a first stack 400, a first charge generation layer 220, a second stack ( 500), the second charge generation layer 320, and the third stack 600 are sequentially stacked.

The first stack 400 and the third stack 600 may include a light emitting layer having the same color. Also, the second stack 500 may include a light emitting layer having a different color from that of the first stack 400 and the third stack 600 . At this time, the light of different colors emitted from the light emitting layer of each stack is mixed to realize white light.

Preferably, the first stack 400 and the third stack 600 may emit blue light. In addition, the second stack 500 may include a light emitting layer emitting red and yellow-green light, or may include a light emitting layer emitting red and green light. Also, the first stack 400 and the third stack 600 may be formed of a fluorescent unit, and the second stack 500 may be formed of a phosphorescent unit.

The substrate 100 may include a thin film transistor formed on an insulating substrate, wherein the insulating substrate is formed of insulating glass, metal, plastic, polyimide (PI), or the like, and the thin film transistor includes a gate electrode, a semiconductor layer, It consists of a source electrode and a drain electrode.

The first electrode 110 may be formed of a transparent conductive material as an anode, and may include, for example, any one selected from the group consisting of Indum Tin Oxide (ITO), Indum Zinc Oxide (IZO), and ZnO. . The second electrode 130 may be formed of a metal material as a cathode, and for example, a group consisting of Mg, Ca, Al, Al-alloy, Ag, Ag-alloy, Au, and Au-alloy having a low work function. It may include any one selected from.

The first charge generating layer 220 is formed between the first stack 400 and the second stack 500 to supply electrons to the first stack 400 and holes to the second stack 500 . Thus, the charge balance between each stack is adjusted. In addition, the second charge generation layer 320 is formed between the second stack 500 and the third stack 600 to supply electrons to the second stack 500 and holes to the third stack 600 . to adjust the charge balance between each stack.

The first charge generation layer 220 and the second charge generation layer 320 are formed of a thin metal layer such as aluminum (Al) or a single layer formed of a transparent electrode such as ITO (Indum Tin Oxide), so that the device configuration is simple. and can be easily manufactured. In addition, it may be formed as a plurality of layers, which is a junction structure of an organic material layer by impurity doping.

In the case of forming a plurality of layers, it is advantageous in improving efficiency and prolonging life by forming suitable for electron transport and hole transport, respectively. At this time, the region in contact with the first stack 400 of the first charge generation layer 220 and the region in contact with the second stack 500 of the second charge generation layer 320 are formed to facilitate electron supply. It may be N-type doped. In addition, a region in contact with the second stack 500 of the first charge generation layer 220 and a region in contact with the third stack 600 of the second charge generation layer 320 are formed to facilitate hole supply. It may be formed by P-type doping.

The first stack 400 includes a hole injection layer (HIL) 402 and a first hole transport layer (HTL) between the first electrode 110 and the first charge generation layer 220 . 403, a first light emitting layer 404, and a first electron transport layer (ETL) 405 are sequentially stacked and formed. The hole injection layer (HIL) 402 may use a material having excellent hole injection capability, and may be doped with P-type doping to facilitate hole injection.

The first emission layer 404 is a fluorescent blue emission layer and may be formed as a single emission layer having an emission peak of 1-Peak. In this case, the first light emitting layer 404 may be formed by doping one host with a fluorescent blue dopant, or by doping two hosts with a fluorescent blue dopant. The fluorescent blue dopant of the first emission layer 204 is formed of a dopant having a wavelength band of an emission peak in the range of 420 nm to 490 nm.

The second stack 500 is interposed between the first charge generation layer 220 and the second charge generation layer 320 , a second hole transport layer (HTL) 502 , a second emission layer 503 , and a third emission layer 504 . ) and a second electron transport layer (ETL) 505 are sequentially stacked. The second stack 300 is formed by contacting the second light emitting layer 503 and the third light emitting layer 504 in contact with each other without a charge generating layer or a buffer layer therebetween. In addition, the second light emitting layer 503 and the third light emitting layer 504 are stacked to form one second stack of light emitting layers 501 .

The second stack light emitting layer 501 may be formed by stacking a phosphorescent red light emitting layer and a phosphorescent yellow green light emitting layer to form a dual light emitting layer having an emission peak of 2-Peak. In addition, the second stack emission layer 501 may be formed by stacking a phosphorescent red emission layer and a phosphorescent green emission layer.

That is, when the second light-emitting layer 503 is a phosphorescent red light-emitting layer, the third light-emitting layer 504 is formed of a phosphorescent yellow-green light-emitting layer or a phosphorescent green light-emitting layer. Alternatively, when the second light-emitting layer 503 is a phosphorescent yellow-green light-emitting layer or a phosphorescent green light-emitting layer, the third light-emitting layer 504 is formed of a phosphorescent red light-emitting layer. Preferably, the second light-emitting layer 503 may be formed of a phosphorescent red light-emitting layer, and the third light-emitting layer 504 may be formed of a phosphorescent yellow-green light-emitting layer.

The phosphorescent yellow green light emitting layer or the phosphorescent green light emitting layer is formed of a phosphorescent yellow green dopant or a phosphorescent green dopant having a wavelength band of an emission peak in the range of 500 nm to 580 nm, and the phosphorescent red emission layer has a wavelength band of an emission peak at 580 nm It is formed with a phosphorescent red dopant having a range of ~680 nm. In addition, the dopant doping ratio of the phosphorescent yellow-green emission layer or the phosphorescent green emission layer may be higher than that of the phosphorescent red emission layer.

In addition, the phosphorescent yellow-green light-emitting layer or the phosphorescent green light-emitting layer may be formed to have a thickness greater than that of the phosphorescent red light-emitting layer. Preferably, the thickness of the phosphorescent yellow-green light-emitting layer or the phosphorescent green light-emitting layer may be three times the thickness of the phosphorescent red light-emitting layer.

The second light emitting layer 503 is formed by being stacked in contact with the second hole transport layer 502 , and includes a phosphorescent red dopant, a phosphorescent yellow green dopant, or a phosphorescent green dopant on two hosts. (dopant) may be formed by doping. The two hosts may include a hole type host and an electron type host.

In this case, the hole host may be formed in 20% to 80% by volume of the total host, and the electron host may be formed in 80% by volume to 20% by volume of the entire host. In addition, the hole host may be formed of the same material as the second hole transport layer 502 to facilitate hole injection.

The third light-emitting layer 504 is formed on the second light-emitting layer 503, and two hosts are doped with a phosphorescent yellow-green dopant, a phosphorescent green dopant, or a phosphorescent red dopant. can be formed.

In this case, the two hosts may include a hole type host and an electron type host. In this case, the hole host may be formed in 20% to 80% by volume of the total host, and the electron host may be formed in 80% by volume to 20% by volume of the entire host.

In addition, the third emission layer 504 may be formed by doping one host with a phosphorescent yellow-green dopant, a phosphorescent green dopant, or a phosphorescent red dopant. In this case, the one host is formed as a bipolar host.

The third stack 600 includes a third hole transport layer (HTL) 601 , a fourth emission layer 602 , and a third electron transport layer (ETL) between the second charge generation layer 320 and the second electrode 130 . 603 and an electron injection layer (EIL) 604 are sequentially stacked and formed. The electron injection layer EIL may be formed of a material having excellent electron injection capability, and may be doped with N-type doping to facilitate electron injection.

The fourth emission layer 602 is a fluorescent blue emission layer and may be formed as a single emission layer having an emission peak of 1-Peak. In this case, the fourth light emitting layer 602 may be formed by doping one host with a fluorescent blue dopant, or by doping two hosts with a fluorescent blue dopant. The fluorescent blue dopant of the fourth light emitting layer 602 is formed of a dopant having a wavelength band of an emission peak in the range of 420 nm to 490 nm.

8 is a view showing emission wavelength and intensity of a conventional white organic light emitting device and a white organic light emitting device of the present invention.

Referring to FIG. 8 , a conventional white organic light emitting device is a white organic light emitting device including a blue light emitting layer in a first stack and a third stack and a yellow-green light emitting layer in a second stack. In addition, the white organic light emitting device of the present invention includes a blue light emitting layer in a first stack and a third stack, and a white organic light emitting layer including a red light emitting layer and a yellow-green light emitting layer in a second stack. It is a light emitting device.

The region shown in FIG. 8 is a red region, and it can be seen that, in the conventional invention, only two peaks exist, so that no peak is formed in the red region. In addition, in the present invention, it can be seen that the intensity of red is formed to be larger in the red region compared to the conventional invention as the three-peak structure. The luminance achievement rate, panel efficiency, and color gamut will be described in more detail as follows.

9 is a view showing experimental results comparing the conventional white organic light emitting device and the white organic light emitting device of the present invention.

Referring to FIG. 9 , the red luminance achievement rate of the conventional invention is 88% when the luminance target value is 100%, and there is a problem in that the red luminance is insufficient. This is because, in the conventional invention, a separate red light emitting layer does not exist, and a peak is not formed in the red region.

Accordingly, in the white organic light emitting device according to the present invention, a red light emitting layer and a yellow green light emitting layer are stacked in a second stack to form a second stack light emitting layer. For this reason, in the red wavelength region, the intensity of the white organic light emitting diode according to the present invention is stronger than that of the conventional invention.

Comparing the luminance achievement rate of the present invention and the conventional invention, the present invention increased by about 13% to 101%. In addition, it can be seen that the red luminance achievement rate of the present invention exceeds 100%, the luminance target value. In addition, it can be seen that the green and blue luminance achievement rates of the present invention also exceed the luminance target value of 100%.

In addition, it can be confirmed that the panel efficiency is also equal to or improved compared to the conventional invention. As the intensity increases in the red wavelength region, it can be seen that the color gamut also increases.

Accordingly, in the white organic light emitting device according to the present invention, the light emitting layer of the white organic light emitting device including the first stack and the second stack or the white organic light emitting device including the first to third stacks has an emission peak of 3-peak. is formed to In this case, by using the material of the hole transport layer as a host in the light emitting layer of the second stack adjacent to the hole transport layer, hole injection may be facilitated. By optimizing the thickness and doping concentration of the light emitting layer of the second stack, power consumption can be improved, and panel efficiency and color gamut can be improved. In addition, by forming the light emitting layer of the second stack of the white organic light emitting diode including the first stack to the third stack in a double light emitting layer structure, there is an effect of increasing red luminance achievement and increasing color gamut.

Those skilled in the art from the above description will be able to see that various changes and modifications can be made without departing from the technical spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

100: substrate 205: first electron transport layer
110: first electrode 300: second stack
120: charge generation layer 301: second stack light emitting layer
130: second electrode 302: second hole transport layer
200: first stack 303: second light emitting layer
202: hole injection layer 304: third light emitting layer
203: first hole transport layer 305: second electron transport layer
204: first light emitting layer 306: electron injection layer

Claims (35)

a first electrode and a second electrode facing each other on the substrate;
a first stack including at least one organic layer including a blue light emitting layer between the first electrode and the second electrode; and
A first stack comprising a plurality of organic layers including a phosphorescent red light emitting layer and a plurality of light emitting layers including a phosphorescent green light emitting layer or a phosphorescent yellow green light emitting layer disposed between the first stack and the second electrode in direct contact with the phosphorescent red light emitting layer contains 2 stacks,
The blue light emitting layer includes at least one host and a blue dopant having a wavelength band of an emission peak of 420 nm to 490 nm,
The phosphorescent red light emitting layer includes at least one host and a phosphorescent red dopant having a wavelength band of an emission peak of 580 nm to 680 nm,
and a thickness of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is thicker than a thickness of the phosphorescent red light emitting layer. The method of claim 1,
The phosphorescent green light emitting layer includes at least one host and a phosphorescent green dopant having a wavelength band of an emission peak of 500 nm to 580 nm,
The phosphorescent yellow-green emission layer is a white organic light-emitting device comprising at least one host and a phosphorescent yellow-green dopant having a wavelength band of an emission peak of 500 nm to 580 nm. delete delete The method of claim 1,
The phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is disposed on the phosphorescent red light emitting layer so as to be adjacent to the second electrode. delete 3. The method of claim 2,
A dopant doping ratio of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is higher than that of the phosphorescent red light emitting layer. The method of claim 1,
The white organic light-emitting device further comprising a charge generation layer formed between the first stack and the second stack to adjust a charge balance between the respective stacks. The method of claim 1,
The first stack includes a hole injection layer, a first hole transport layer, the blue light emitting layer and a first electron transport layer sequentially stacked on the first electrode,
The second stack may include a second hole transport layer sequentially stacked on the first stack, the plurality of emission layers, a second electron transport layer, and an electron injection layer. an anode and a cathode opposed to each other on the substrate;
a first stack disposed on the anode and comprising at least one organic layer comprising a first light emitting layer; and
a second stack disposed on the first stack, the second stack comprising a plurality of organic layers comprising a second light-emitting layer and a third light-emitting layer;
The first light emitting layer is a blue light emitting layer including at least one host and a blue dopant having a wavelength band of an emission peak of 420 nm to 490 nm,
The third light-emitting layer is disposed in direct contact with the second light-emitting layer,
The second light emitting layer is a phosphorescent green light emitting layer or a phosphorescent yellow green light emitting layer comprising at least one host and a phosphorescent green dopant or a phosphorescent yellow green dopant having an emission peak wavelength of 500 nm to 580 nm, and the third light emitting layer includes one host and 580 nm A phosphorescent red light emitting layer comprising a phosphorescent red dopant having a wavelength band of an emission peak of ~680 nm,
A thickness of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is greater than a thickness of the phosphorescent red light emitting layer. delete delete 11. The method of claim 10,
A dopant doping ratio of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is higher than that of the phosphorescent red light emitting layer. 11. The method of claim 10,
The white organic light-emitting device further comprising a charge generation layer formed between the first stack and the second stack to adjust a charge balance between the respective stacks. 11. The method of claim 10,
The second light emitting layer and the third light emitting layer each include a hole host and an electron host. 16. The method of claim 15,
A white organic light-emitting device, characterized in that the hole host of each of the second light-emitting layer and the third light-emitting layer is formed in 40% to 60% by volume of the total host. 16. The method of claim 15,
The third light emitting layer is a white organic light emitting device including a bipolar host. a first electrode and a second electrode facing each other on the substrate;
a first stack comprising at least one organic layer comprising a first blue light emitting layer, between the first and second electrodes;
a second stack including a plurality of organic layers including a plurality of light emitting layers including a phosphorescent red light emitting layer between the first stack and the second electrode;
a third stack comprising at least one organic layer comprising a second blue light emitting layer between the second stack and the second electrode; and
a first charge generation layer formed between the first stack and the second stack and a second charge generation layer formed between the second stack and the third stack to adjust the charge balance between the respective stacks;
a plurality of light emitting layers of the second stack are disposed between the first charge generation layer and the second charge generation layer;
Each of the first blue light emitting layer and the second blue light emitting layer includes at least one host and a blue dopant having a wavelength band of an emission peak of 420 nm to 490 nm,
The phosphorescent red emission layer includes at least one host and a phosphorescent red dopant having an emission peak wavelength of 580 nm to 680 nm. 19. The method of claim 18,
The plurality of light emitting layers is a phosphorescent green light emitting layer comprising at least one host and a phosphorescent green dopant having a wavelength band of an emission peak of 500 nm to 580 nm; or
A white organic light-emitting device further comprising a phosphorescent yellow-green emission layer comprising at least one host and a phosphorescent yellow-green dopant having an emission peak wavelength of 500 nm to 580 nm. 20. The method of claim 19,
The phosphorescent red light emitting layer is a white organic light emitting device in direct contact with the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer. 21. The method of claim 20,
The phosphorescent red light emitting layer is a white organic light emitting device disposed on the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer. 21. The method of claim 20,
The phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is a white organic light emitting device disposed on the phosphorescent red light emitting layer. 20. The method of claim 19,
A thickness of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is greater than a thickness of the phosphorescent red light emitting layer. 20. The method of claim 19,
A dopant doping ratio of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is higher than that of the phosphorescent red light emitting layer. delete 20. The method of claim 19,
The first stack and the third stack each have at least one emission peak, and the second stack has at least two emission peaks. 20. The method of claim 19,
The first stack includes a hole injection layer, a first hole transport layer, the first blue light emitting layer and a first electron transport layer sequentially stacked on the first electrode,
The second stack includes a second hole transport layer sequentially stacked on the first stack, the plurality of light emitting layers and a second electron transport layer,
wherein the third stack includes a third hole transport layer, the second blue light emitting layer, a third electron transport layer, and an electron injection layer sequentially stacked on the second stack. an anode and a cathode opposed to each other on the substrate;
a first stack disposed on the anode and comprising at least one organic layer comprising a first light emitting layer;
a second stack disposed on the first stack and including a plurality of organic layers including a second light-emitting layer and a third light-emitting layer;
a third stack disposed on the second stack and comprising at least one organic layer comprising a fourth light emitting layer; and
a first charge generation layer formed between the first stack and the second stack and a second charge generation layer formed between the second stack and the third stack to adjust the charge balance between the respective stacks;
a second light-emitting layer and a third light-emitting layer of the second stack are disposed between the first charge generation layer and the second charge generation layer;
Each of the first light emitting layer and the fourth light emitting layer is a blue light emitting layer including at least one host and a blue dopant having a wavelength band of an emission peak of 420 nm to 490 nm,
The third light-emitting layer is disposed on the second light-emitting layer,
The second light emitting layer is a phosphorescent green light emitting layer or a phosphorescent yellow green light emitting layer comprising at least one host and a phosphorescent green dopant or a phosphorescent yellow green dopant having an emission peak wavelength of 500 nm to 580 nm, and the third light emitting layer includes one host and 580 nm A white organic light emitting device as a phosphorescent red light emitting layer including a phosphorescent red dopant having a wavelength band of an emission peak of ~680 nm. 29. The method of claim 28,
The second light emitting layer and the third light emitting layer are formed in direct contact with each other. 29. The method of claim 28,
A thickness of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is thicker than that of the phosphorescent red light emitting layer. 29. The method of claim 28,
A dopant doping ratio of the phosphorescent green light emitting layer or the phosphorescent yellow green light emitting layer is higher than that of the phosphorescent red light emitting layer. delete 29. The method of claim 28,
The second light emitting layer and the third light emitting layer each include a hole host and an electron host. 34. The method of claim 33,
A white organic light-emitting device, characterized in that the hole host of each of the second light-emitting layer and the third light-emitting layer is formed in 40% to 60% by volume of the total host. 34. The method of claim 33,
The third light emitting layer is a white organic light emitting device including a bipolar host.

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