KR102272053B1 - White organic light emitting device - Google Patents

Abstract

A white organic light emitting diode according to the present invention includes a first light emitting part between a first electrode and a second electrode, a second light emitting part on the first light emitting part, and a third light emitting part on the second light emitting part, The third light emitting unit includes a red light emitting layer and a blue light emitting layer, and the host of the red light emitting layer includes a hole transport layer, thereby providing a white organic light emitting device capable of improving light emitting intensity and light emitting efficiency of the light emitting layer.

Description

White organic light emitting device {WHITE ORGANIC LIGHT EMITTING DEVICE}

The present invention relates to an organic light emitting device, and more particularly, to a white organic light emitting device capable of improving light emission intensity, luminance, and color gamut of the device.

Recently, as we enter the information age, the field of display that visually expresses electrical information signals has developed rapidly, and in response to this, various flat display devices with excellent performance such as thinness, light weight, and low power consumption (Flat Display) have been developed. device) is being developed.

Specific examples of such a flat panel display device 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.

In particular, the organic light emitting diode display is a self-luminous device, and has advantages in that the response speed is fast and luminous efficiency, luminance, and viewing angle are large compared to other flat panel displays.

In the organic light emitting diode display, an organic light emitting layer is formed between two electrodes. Electrons and holes are respectively injected from the two electrodes into the organic light emitting layer to generate excitons according to the combination of electrons and holes. And, it is a device using the principle that light is generated when the generated exciton falls from an excited state to a ground state.

1. [White organic light emitting device] (Patent Application No. 10-2009-0092596)

Conventional organic light emitting devices have limitations in light emitting characteristics and lifetime performance due to the material and device structure of the organic light emitting layer, and thus various methods for improving the efficiency of the light emitting layer in the white organic light emitting device have been proposed.

As a method, two light-emitting layers having a complementary color relationship may be stacked to have a structure emitting white light. However, in this structure, when white light passes through the color filter, a difference occurs between the wavelength region of the emission peak of each light emitting layer and the transmission region of the color filter. Therefore, it is difficult to realize a desired color gamut because the color range that can be expressed is narrowed.

For example, when the blue light emitting layer and the yellow light emitting layer are stacked, white light is emitted while the wavelength of the emission peak is formed in the blue wavelength region and the yellow wavelength region. When the white light passes through the red, green, and blue color filters, respectively, the transmittance of the blue wavelength region is lower than that of the red or green wavelength region, so that luminous efficiency and color gamut are lowered.

In addition, the luminous efficiency of the yellow phosphorescent emitting layer is relatively higher than that of the blue fluorescence emitting layer, thereby reducing panel efficiency and color gamut due to the difference in efficiency between the phosphorescent emitting layer and the fluorescent emitting layer.

Accordingly, the inventors of the present invention recognized the above-mentioned problems, and conducted various experiments to increase the luminous efficiency of the light emitting layer and increase the color gamut of the device. Through various experiments, a white organic light emitting device having a new structure capable of improving luminance and color gamut was invented.

An object to be solved according to an embodiment of the present invention is to provide a white organic light-emitting device capable of improving light-emitting intensity and light-emitting efficiency by adjusting the characteristics of the light-emitting layer.

A problem to be solved according to an embodiment of the present invention is a white organic light emitting diode capable of improving luminance and color gamut by applying a TER-TEP (Three Emission Region-Three Emission Peak) structure having three emission peaks to three light emitting units. is to provide

The problems to be solved according to the embodiment of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A white organic light emitting diode according to an embodiment of the present invention includes a first light emitting part positioned between a first electrode and a second electrode, a second light emitting part positioned on the first light emitting part, and a third light emitting part positioned on the second light emitting part. It provides a white organic light emitting device including a light emitting unit, wherein the third light emitting unit is composed of a red light emitting layer and a blue light emitting layer, and the host of the red light emitting layer includes a hole transport layer, thereby improving the light emitting intensity and luminous efficiency of the light emitting layer .

The blue light emitting layer of the third light emitting part is characterized in that it is one of a blue light emitting layer, a deep blue light emitting layer, or a sky blue light emitting layer.

The energy gap of the hole transport layer is characterized in that the range of 2.8eV to 3.5eV.

The emission peak of the third emission part has a first emission peak and a second emission peak.

The first emission peak is characterized in that the range of 600 nm to 650 nm.

The second emission peak is characterized in that the range of 440 nm to 480 nm.

A white organic light emitting diode according to an embodiment of the present invention includes a first light emitting part positioned between a first electrode and a second electrode, a second light emitting part positioned on the first light emitting part, and a third light emitting part positioned on the second light emitting part. It includes a light emitting unit, and the first light emitting unit, the second light emitting unit and the third light emitting unit apply a TER-TEP (Three Emission Region-Three Emission Peak) structure having three emission peaks, thereby increasing luminance and color gamut. To provide a white organic light emitting device that can be improved.

The first light emitting unit may include a light emitting layer made of one of a blue light emitting layer, a deep blue light emitting layer, and a sky blue light emitting layer.

The second light emitting unit may include a light emitting layer made of one of a yellow-green light emitting layer or a green light emitting layer.

The third light emitting unit is characterized in that the third light emitting unit includes a first light emitting layer including a red light emitting layer and a second light emitting layer including one of a blue light emitting layer, a deep blue light emitting layer, or a sky blue light emitting layer.

The host included in the first light emitting layer is characterized in that it includes a hole transport layer.

The energy gap of the hole transport layer is characterized in that the range of 2.8eV to 3.5eV.

The second light emitting layer is configured to be closer to the second electrode than the first light emitting layer.

The emission peak of the first light emitting part is in the range of 440 nm to 480 nm, the emission peak of the second light emitting part is in the range of 520 nm to 590 nm, and the emission peak of the third light emitting part is in the range of 600 nm to 650 nm and 440 nm to It is characterized in that it is in the range of 480 nm.

A white organic light emitting diode according to an embodiment of the present invention includes first and second electrodes facing each other on a substrate, and at least two light emitting units positioned between the first and second electrodes, the at least two At least one light emitting unit of the above light emitting units includes two light emitting layers, and one of the at least two light emitting layers includes a hole transport layer as a host, thereby providing a white organic light emitting device capable of improving the light emitting intensity and luminous efficiency of the light emitting layer do.

The two light emitting layers are characterized in that they are a red light emitting layer and a blue light emitting layer.

The hole transport layer is characterized in that the host of the red light emitting layer.

The blue light emitting layer is configured to be closer to the second electrode than the red light emitting layer.

The details of other embodiments are included in the detailed description and drawings.

In the present invention, two light emitting layers in one light emitting part are composed of a red light emitting layer and a blue light emitting layer, and the blue light emitting layer is configured close to the second electrode, so that the red light emitting layer and the blue light emitting layer are formed close to the second electrode. Blue) has the effect of improving the luminous intensity and luminous efficiency of the light emitting layer.

In addition, by configuring a red light emitting layer and a blue light emitting layer in one light emitting part, and applying a hole transport layer as a host of the red light emitting layer, the luminous efficiency of the blue light emitting layer and the red light emitting layer has the effect of improving

In addition, since both the blue light emitting layer and the red light emitting layer, which are two light emitting layers in one light emitting part, contribute to light emission of the organic light emitting device, the luminance and color gamut of the organic light emitting diode display may be improved.

In addition, it is possible to provide an organic light emitting device in which an increase in driving voltage or a decrease in quantum efficiency generated when two light emitting layers are configured in one light emitting unit.

In addition, by applying a TER-TEP (Three Emission Region-Three Emission Peak) structure having three emission peaks to the three light emitting units, the luminance and color gamut of the organic light emitting diode display may be improved.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

Since the content of the invention described in the problems to be solved above, the means for solving the problems, and the effects do not specify the essential characteristics of the claims, the scope of the claims is not limited by the matters described in the content of the invention.

1 is a schematic cross-sectional view showing a white organic light emitting device according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a change rate of a color viewing angle according to a viewing angle at a light emitting position of a light emitting unit according to a second exemplary embodiment of the present invention.
3 is a view showing the light emission intensity of the light emitting unit according to the second embodiment of the present invention.
4 is a diagram illustrating emission intensity of a white organic light emitting diode according to a first embodiment and a second embodiment of the present invention.
5 is a diagram illustrating an energy band diagram of a light emitting unit according to a second embodiment of the present invention.
6 is a diagram illustrating an energy band diagram of a light emitting unit according to a third embodiment of the present invention.
7 is a view showing the emission intensity of a light emitting unit according to a second embodiment of the present invention and a third embodiment of the present invention.
8 is a schematic cross-sectional view illustrating a white organic light emitting diode according to a third exemplary embodiment of the present invention.
FIG. 9 is a view showing emission intensity of white organic light emitting diodes according to the first and third embodiments of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and thus the present invention is not limited to the illustrated matters. Like reference numerals refer to like elements throughout. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless otherwise explicitly stated.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, one or more other parts may be positioned between the two parts unless 'directly' is used.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described with 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless this is used.

Although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship. may be

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings and examples.

1 is a schematic cross-sectional view showing a white organic light emitting device according to a first embodiment of the present invention.

The white organic light emitting diode 100 illustrated in FIG. 1 includes a first electrode 102 and a second electrode 104 on a substrate 101 , and a first light emitting unit 110 between the first and second electrodes 102 and 104 . ), a second light emitting unit 120 and a third light emitting unit 130 are provided.

The first electrode 102 is an anode for supplying holes, and may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), etc., which are transparent conductive materials such as transparent conductive oxide (TCO), but it must be It is not limited.

The second electrode 104 is a cathode for supplying electrons, and is formed of a metallic material such as gold (Au), silver (Ag), aluminum (Al), molybdenum (Mo), magnesium (Mg), or the like, or It may be formed of an alloy, but is not necessarily limited thereto.

The first electrode 102 and the second electrode 104 may be referred to as an anode or a cathode, respectively. In addition, the first electrode 102 may be referred to as a transflective electrode, and the second electrode 104 may be referred to as a reflective electrode.

Here, a bottom emission method in which the first electrode 102 is a transflective electrode and the second electrode 104 is a reflective electrode will be described.

The first light emitting unit 110 includes a first hole transport layer (HTL) 112, a first emitting layer (EML) 114, a first electron transport layer (HTL) on the first electrode 102 ( It may include an Electron Transporting Layer (ETL) 116 .

The first light emitting layer (EML) 114 includes a blue light emitting layer.

A first charge generating layer (CGL) 140 may be further formed between the first light emitting unit 110 and the second light emitting unit 120 . The first charge generation layer (CGL) 140 adjusts the charge balance between the first light emitting unit 110 and the second light emitting unit 120 . The first charge generation layer 140 may include an N-type charge generation layer (N-CGL) and a P-type charge generation layer (P-CGL).

The second light emitting part 120 includes a second hole transporting layer (HTL) 122 , a first emitting layer (EML) 124 , and a second electron transporting layer (ETL) 126 . ) can be included

The first light emitting layer (EML) 124 of the second light emitting unit 120 is formed of a yellow-green light emitting layer.

The third light emitting unit 130 includes a third electron transporting layer (ETL) 136 , a first emitting layer (EML) 134 , and a third hole transporting layer under the second electrode 104 . (HTL; Hole Transporting Layer) 132 may be included.

The first light emitting layer (EML) 134 of the third light emitting unit 130 is formed of a blue light emitting layer.

A second charge generating layer (CGL) 150 may be further formed between the second light emitting unit 120 and the third light emitting unit 130 . The second charge generation layer 150 adjusts the charge balance between the second light emitting unit 120 and the third light emitting unit 130 . The second charge generation layer (CGL) 150 may include an N-type charge generation layer (N-CGL) and a P-type charge generation layer (P-CGL).

In this structure, since the yellow-green light-emitting layer, which is the first light-emitting layer (EML) 124 of the second light-emitting unit 120 , must emit light in both red and green regions, red The luminous efficiency of (Red) and Green (Green) is decreased. In particular, since the emission intensity of red, which is a long wavelength region, is low, red efficiency is further lowered.

In addition, since the wavelength at which the transmittance of the color filter is maximum and the emission peak of the yellow-green emission layer do not coincide, the efficiency of red and green decreases.

In addition, in a white organic light emitting device that implements red, green, and blue colors through a color filter, red and green regions are formed as a yellow-green light emitting layer. Since they must all be implemented, the color purity of Red and Green is reduced.

In addition, in order to increase red efficiency, when a light emitting unit including a red light emitting layer is additionally configured in one light emitting unit in the structure shown in FIG. 1 , the driving voltage increases as the thickness of the device increases. occurs

Accordingly, the inventors of the present invention conducted several experiments to improve the efficiency of the blue light emitting layer and the red light emitting layer.

Accordingly, the inventors of the present invention confirmed the color viewing angle change rate (Δu'v') according to the viewing angle with respect to the position of the red light emitting layer when a blue light emitting layer and a red light emitting layer are configured in one light emitting part. , which is shown in FIG. 2 .

FIG. 2 is a diagram illustrating a change rate of a color viewing angle according to a viewing angle at a position of a light emitting unit according to a second exemplary embodiment of the present invention.

In FIG. 2 , the horizontal axis represents the viewing angle angle, and the vertical axis represents the color viewing angle change rate Δu'v'.

2 is a view showing the change rate of the color viewing angle according to the viewing angle at positions ① below the blue light emitting layer and ② above the blue light emitting layer of the red light emitting layer constituting the third light emitting unit 130. .

As shown in FIG. 2 , it can be seen that the change rate of the color viewing angle according to the viewing angle is smaller at the position ① than at the position ②, so that the change in white is small. For example, at a viewing angle of 60 ‹, position ① has a color viewing angle change rate (Δu'v') of 0.0167, and position ② has a color viewing angle change rate (Δu'v') of 0.0224. It can be seen that (Δu'v') is small.

Accordingly, as a result of confirming the rate of change of the color viewing angle according to the viewing angle (Δu'v'), in the third light emitting unit 130 , the position of the red light emitting layer under the blue light emitting layer is the rate of change of the color viewing angle according to the viewing angle. (Δu'v') was confirmed to be small. In addition, since the color viewing angle change rate Δu'v' is small, color shift can be prevented, and it can be seen that the effect on display quality is small.

In addition, the inventors of the present invention confirmed that only the red light emitting layer emits light when two light emitting layers, a red light emitting layer and a blue light emitting layer, are formed in the third light emitting unit 130 through various experiments. there was. This will be described with reference to FIG. 3 .

3 is a view showing the light emission intensity of the light emitting unit according to the second embodiment of the present invention.

FIG. 3 shows light emission intensity when a red light emitting layer and a blue light emitting layer are formed in the third light emitting unit 130 . As shown in FIG. 3 , it can be confirmed that only the emission peak of the red light emitting layer appears.

Accordingly, the inventors of the present invention have recognized that when a red light emitting layer and a blue light emitting layer are configured in one light emitting unit, the efficiency of the blue light emitting layer decreases and the luminance of the organic light emitting display device decreases. . This will be described with reference to FIG. 4 .

4 is a diagram illustrating emission intensity of the organic light emitting diode display according to the first and second exemplary embodiments of the present invention. 4 , in the first embodiment, a blue light emitting layer is configured as the first light emitting layer (EML) of the first light emitting part, and a yellow-green light emitting layer is configured as the first light emitting layer (EML) of the second light emitting part. and a blue light emitting layer as the first light emitting layer EML of the third light emitting part. In the second embodiment of the present invention, a blue light emitting layer is configured as the first light emitting layer (EML) of the first light emitting unit, and a yellow-green light emitting layer is formed as the first light emitting layer (EML) of the second light emitting unit. and a red light emitting layer as the first light emitting layer EML of the third light emitting unit and a blue light emitting layer as the second light emitting layer EML.

As shown in FIG. 4 , in the second embodiment of the present invention, it can be seen that the emission peak appears at 600 nm to 650 nm, which is the emission peak of the red emission layer, compared to the first embodiment. . That is, according to the second embodiment of the present invention, it can be seen that the TER-TEP (Three Emission Region-Three Emission Peak) structure has three emission peaks in three light emitting portions.

In the second embodiment of the present invention, it can be seen that the emission intensity of the blue light emitting layer is decreased at 440 nm to 480 nm, which is the emission peak of the blue light emitting layer, as compared with that of the first embodiment.

And, the results of measuring DCI (Digital Cinema Initiatives) color gamut and luminance are shown in Table 1 below.

As shown in Table 1, it can be seen that the color gamut is increased by 9% compared to the first embodiment because the luminous efficiency of the red light emitting layer is increased in the second embodiment.

Also, since the emission intensity of the blue light emitting layer is decreased in the second embodiment, it can be seen that the luminance of the organic light emitting diode display decreases by 14% compared to the first embodiment.

Accordingly, it can be seen that when two light emitting layers are configured in one light emitting part, the light emission intensity of the red light emitting layer is increased, but the light emission intensity of the blue light emitting layer is decreased. In addition, it can be seen that the color gamut is increased, but the luminance is decreased because the emission intensity of the blue light emitting layer is decreased. This will be described with reference to FIG. 5 .

5 is a diagram illustrating a band diagram of a light emitting unit according to a second embodiment of the present invention.

5 is a diagram in which two light emitting layers are configured in the third light emitting unit in an organic light emitting device including three light emitting units, and among the two light emitting layers, a first light emitting layer (EML) is a red light emitting layer (EML) 234 and a second light emitting layer The light emitting layer EML is formed of a blue light emitting layer (EML) 235 .

로 표시)의 결합에 의한 에너지로 유기 발광층의 발광 물질이 여기 상태(excited state, S1)가 되고 그 여기 상태(S1)에서 다시 기저 상태(ground state)로 돌아갈 때에 빛을 발생한다. 도 5에서 실선은 전자(electron)와 정공(hole)의 이동을 나타낸 것이다. Luminescence refers to a phenomenon in which a material receives energy by electromagnetic waves, heat, or friction and is excited, and emits light of a specific wavelength with the received energy. In the case of an organic light emitting device, electrons (indicated by θ in FIG. 5) and holes (in FIG. 5)

The light emitting material of the organic light emitting layer becomes an excited state (S1) with energy due to the combination of ) and generates light when it returns to the ground state from the excited state (S1). In FIG. 5, the solid line represents the movement of electrons and holes.

When the two light emitting layers of the red light emitting layer and the blue light emitting layer are configured, only the red light emitting layer emits light because of the difference in the band gap between the red light emitting layer and the blue light emitting layer. Occurs. A band gap of a host included in the red emission layer is 2.4 eV, and a band gap of a host included in the blue emission layer is 3.0 eV. Since the excited state 234S1 of the red light emitting layer, that is, the singlet energy level, is lower than the energy level 235S1 of the blue light emitting layer, the red light emitting layer and the blue The energy of the exciton E formed at the interface of the light emitting layer is lowered. Therefore, excitons do not move to the blue light emitting layer, but the excitons move to the stable red light emitting layer to emit light, so that only the red light emitting layer emits light.

Accordingly, the inventors of the present invention have recognized that when a red light emitting layer and a blue light emitting layer are configured in one light emitting unit, only the red light emitting layer emits light. Therefore, the inventors of the present invention conducted various experiments to emit light of both the red light emitting layer and the blue light emitting layer when the red light emitting layer and the blue light emitting layer are configured in one light emitting part. .

The inventors of the present invention through various experiments, rather than controlling the blue light emitting layer having a large singlet energy level, control the characteristics of the red light emitting layer having a relatively low energy level compared to the blue light emitting layer. found to be more effective. This is because when the singlet energy level of the blue light emitting layer is reduced, light emission of the blue light emitting layer becomes more difficult. Therefore, in order for the blue light emitting layer to emit light, the singlet energy level must be 2.8 eV or higher.

Therefore, the inventors of the present invention improve the luminous efficiency of the red light emitting layer and the blue light emitting layer by controlling the characteristics of the red light emitting layer having a lower singlet energy level than the blue light emitting layer, and , invented a white organic light emitting device having a new structure capable of improving luminance.

The white organic light emitting diode according to the exemplary embodiment of the present invention has three emission peaks in three emission portions of the first light emitting unit, the second light emitting unit, and the third light emitting unit. In the three emission peaks, a blue emission peak, which is a first emission peak, appears by the first emission layer included in the first emission portion. In addition, a second emission peak, a yellow-green emission peak, appears by the first emission layer included in the second emission portion. In addition, a red emission peak, which is a third emission peak, appears by the red emission layer among the two emission layers included in the third emission part. Accordingly, by applying a Three Emission Region-Three Emission Peak (TER-TEP) structure having three emission peaks to the three light emitting units, the luminance and color gamut of the organic light emitting diode display may be improved.

And, in the organic light emitting device including at least three light emitting units according to an embodiment of the present invention, a red light emitting layer and a blue light emitting layer are configured in one light emitting unit, and the blue light emitting layer is the second light emitting layer. placed close to the electrode. With this configuration, since the blue light emitting layer and the red light emitting layer can emit light at the emission peak of the desired light emitting region, the emission intensity and color gamut of the red light emitting layer and the blue light emitting layer can be reduced. can be improved

And, by adjusting the characteristics of the red light emitting layer, both the red light emitting layer and the blue light emitting layer can emit light at an emission peak of a desired light emitting region. Accordingly, the color reproducibility of the red light emitting layer and the blue light emitting layer may be improved, and the luminance of the organic light emitting diode display may be improved.

Through various experiments for controlling the characteristics of the red light emitting layer, it was found that applying a hole transport layer (HTL) to the red light emitting layer can improve device characteristics. This will be described with reference to FIG. 6 .

6 is a diagram illustrating an energy band diagram of a light emitting unit according to a third embodiment of the present invention.

6 is a diagram in which two light emitting layers are configured in the third light emitting unit in an organic light emitting device including three light emitting units, and the two light emitting layers are a red light emitting layer (EML) 334 and a blue light emitting layer (EML) ( 335) was constructed. In addition, a hole transport layer (HTL) is applied as a host of the red light emitting layer.

As shown in FIG. 6 , a hole transport layer (HTL) is configured as a host of the red light emitting layer (EML) 334 . Since the band gap of the hole transport layer (HTL) in the third embodiment has a larger value than that of the host included in the red light emitting layer (EML) 334 , the red light emitting layer (EML) It can be seen that the difference between the band gap of ) 334 and the band gap of the blue light emitting layer (EML) 335 is small. Accordingly, it can be seen that the singlet energy level 334S1 of the red light emitting layer and the singlet energy level 335S1 of the blue light emitting layer are substantially the same. For example, the band gap of the hole transport layer (HTL) may be in a range of 2.8 eV to 3.5 eV.

In addition, since the hole transport layer (HTL) has higher hole mobility compared to the host of the red light emitting layer (EML) 334 , the red light emitting layer (EML) 334 . light emission can be suppressed.

In addition, since the hole mobility of the hole transport layer HTL is greater than the electron mobility, the hole transport layer HTL is formed between the red light emitting layer (EML) 334 and the blue light emitting layer (EML) 334 . Blue) A large number of holes may be formed at the interface of the light emitting layer (EML) 335 .

로 표시)이 결합하여 엑시톤(exciton)(E)이 형성되는 재결합 영역(Recombination Zone)을 상기 청색(Blue) 발광층(EML)(335)으로 이동시킬 수 있으므로, 상기 청색(Blue) 발광층(EML)(335)의 발광을 가능하게 하는 것이다. 도 6에서 실선은 전자(electron)와 정공(hole)의 이동을 나타낸 것이다.Accordingly, since the hole transport layer (HTL) increases the number of holes at the interface between the red light emitting layer (EML) 334 and the blue light emitting layer (EML) 335 , electrons (Fig. 6 in θ) and holes (in FIG. 6)

Since the recombination zone in which exciton (E) is formed by combining) can be moved to the blue light emitting layer (EML) 335, the blue light emitting layer (EML) It is to enable the emission of (335). In FIG. 6, the solid line represents the movement of electrons and holes.

The host of the red emission layer (EML) 334 may be configured as a mixed host including a hole transport layer (HTL). For example, the host of the red light emitting layer (EML) 334 may be made of a material containing CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl), etc., but is limited thereto. The hole transport layer (HTL) may be formed of, for example, a benzidine series, a biphenyl series, an amine series, etc., but is not limited thereto. When the host of (EML) 334 is configured as a mixed host, it can be configured by mixing the host material of the red light emitting layer (EML) 334 and the hole transport layer (HTL) material. , but is not limited thereto.

7 is a view showing the emission intensity of a light emitting unit according to a second embodiment of the present invention and a third embodiment of the present invention.

7 , in the second embodiment of the present invention, a red light emitting layer includes a red host and a red dopant, and a blue light emitting layer includes a blue host and a blue dopant. According to a third embodiment of the present invention, the red light emitting layer includes the host of the hole transport layer and the red dopant, and the blue light emitting layer includes the blue host and the blue dopant.

7, in the second embodiment of the present invention, the emission peak of the blue light emitting layer does not appear, and the emission intensity at 600 nm to 650 nm, which is the emission peak of the red light emitting layer, is can be seen to appear. In the third embodiment of the present invention, it can be seen that the emission intensity is increased at 600 nm to 650 nm, which are the emission peaks of the red emission layer, as compared with the second embodiment. And, in the third embodiment, it can be seen that the emission intensity appears at 440 nm to 480 nm, which is the emission peak of the blue light emitting layer. Therefore, by applying the host of the hole transport layer to the red light emitting layer according to the third embodiment of the present invention, both of the red light emitting layer and the blue light emitting layer emit light, and the red light emitting layer and the It can be seen that the luminous efficiency of the blue light emitting layer is increased.

Table 2 below shows the measurement results of driving voltage, quantum efficiency, and color coordinates according to the second embodiment and the third embodiment of the present invention.

As shown in Table 2, it can be seen that in the third embodiment of the present invention, the driving voltages Volt, V are maintained almost the same as in the second embodiment. It can be seen that the driving voltage does not change even when the hole transport layer is configured as the host of the red light emitting layer.

And, EQE (External quantum efficiency) is external quantum efficiency, which refers to luminous efficiency when light exits the organic light emitting device. It can be seen that this quantum efficiency (EQE) is also the same as in the second embodiment. It can be seen that the quantum efficiency (EQE) does not change even when the hole transport layer is configured as the host of the red light emitting layer.

As for the color coordinates, in the second embodiment, CIE_x was 0.632 and CIE_y was 0.341, and in the third embodiment, CIE_x was 0.193 and CIE_y was 0.137. It can be seen that this represents the color coordinate value of the desired color in the third embodiment when compared with the second embodiment.

Accordingly, by applying the hole transport layer (HTL) as the host of the red light emitting layer, the efficiency of the red light emitting layer and the blue light emitting layer can be improved, and the color gamut can be improved. In addition, by applying the hole transport layer (HTL) as the host of the red emission layer, it is possible to provide a device in which a driving voltage does not increase and quantum efficiency does not decrease.

8 is a schematic cross-sectional view of a white organic light emitting diode according to a third exemplary embodiment of the present invention.

The white organic light emitting diode 300 illustrated in FIG. 8 includes a first electrode 302 and a second electrode 304 on a substrate 301 , and a first light emitting part 310 between the first and second electrodes 302 and 304 . ), a second light emitting unit 320 and a third light emitting unit 330 are provided.

The first electrode 302 is an anode for supplying holes, and may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), etc. which are transparent conductive materials such as transparent conductive oxide (TCO), but must be It is not limited.

The second electrode 304 is a cathode for supplying electrons, and is formed of a metallic material, such as gold (Au), silver (Ag), aluminum (Al), molybdenum (Mo), magnesium (Mg), or the like. It may be formed of an alloy, but is not necessarily limited thereto.

The first electrode 302 and the second electrode 304 may be referred to as an anode or a cathode, respectively.

The first electrode 302 may be a transmissive electrode, and the second electrode 304 may be a reflective electrode. Also, the first electrode 302 may be a reflective electrode, and the second electrode 304 may be a transflective electrode.

Here, a bottom emission method in which the first electrode 302 is a transflective electrode and the second electrode 304 is a reflective electrode will be described.

The first light emitting part 310 may include a first hole transport layer (HTL) 312 , a first emission layer (EML) 314 , and a first electron transport layer (ETL) 316 .

Although not shown in the drawing, a hole injection layer HIL may be additionally formed on the first electrode 302 . The hole injection layer HIL is formed on the first electrode 302 and serves to smoothly inject holes from the first electrode 302 .

The first hole transport layer (HTL) 312 supplies holes from the hole injection layer (HIL) to the first emission layer (EML) 314 . The first electron transport layer (ETL) 316 supplies electrons from the second electrode 304 to the first emission layer (EML) 314 of the first light emitting part 310 .

The hole injection layer (HIL) is made of MTDATA (4,4',4"-tris(3-methylphenylphenylamino)triphenylamine), CuPc (copper phthalocyanine), or PEDOT/PSS (poly(3,4-ethylenedioxythiphene, polystyrene sulfonate), etc.). It can be done, but is not necessarily limited thereto.

In the first emission layer (EML) 314 , holes supplied through the hole transport layer (HIL) and electrons supplied through the electron transport layer (ETL) 316 are recombined to generate light.

The first hole transport layer (HTL) 312 may be formed by applying two or more layers or two or more materials. The first hole transport layer (HTL) 312 is N,N-dinaphthyl-N,N'-diphenylbenzidine (NPD), N,N'-bis-(3-methylphenyl)-N,N'-bis- (phenyl)-benzidine), s-TAD and MTDATA (4,4',4"-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine) may consist of any one or more selected from the group consisting of It is not limited to this.

The first electron transport layer (ETL) 316 may be formed by applying two or more layers or two or more materials. The first electron transport layer (ETL) 316 is Alq3 (tris(8-hydroxyquinolino)aluminum), PBD, TAZ, spiro-PBD, BAlq, Liq (lithium quinolate), BMB-3T, PF-6P, TPBI, COT. And it may consist of any one or more selected from the group consisting of SAlq, but is not limited thereto.

The first light emitting layer (EML) 314 may include a blue light emitting layer, a deep blue light emitting layer, or a sky blue light emitting layer. In addition, an emission peak of the emission region of the first emission layer (EML) 314 may be in a range of 440 nm to 480 nm. The first light emitting layer (EML) 314 may have a different color depending on the configuration of the organic light emitting device.

A first charge generating layer (CGL) 340 may be further formed between the first light emitting part 310 and the second light emitting part 320 . The first charge generating layer (CGL) 340 adjusts the charge balance between the first light emitting part 310 and the second light emitting part 320 . The charge generation layer 340 may include an N-type charge generation layer (N-CGL) and a P-type charge generation layer (P-CGL).

The N-type charge generation layer (N-CGL) may be formed of an organic layer doped with an alkali metal such as Li, Na, K, or Cs, or an alkaline earth metal such as Mg, Sr, Ba, or Ra, respectively, but it must be It is not limited.

Each of the P-type charge generation layers (P-CGL) may be formed of an organic layer including a P-type dopant, but is not limited thereto. In addition, the first charge generating layer (CGL) 140 may be formed as a single layer.

The second light emitting part 320 includes a second hole transport layer (HTL) 322 , a first light emitting layer (EML) 324 and a second electron transport layer (ETL) 326 of the second light emitting part 320 . can be configured. Although not shown in the drawings, an electron injection layer (EIL) may be additionally formed on the second electron transport layer (ETL) 326 . In addition, a hole injection layer (HIL) may be additionally configured.

The second hole transport layer (HTL) 322 may be made of the same material as the first hole transport layer (HTL) 312 , but is not limited thereto.

The second hole transport layer (HTL) 322 may be formed by applying two or more layers or two or more materials.

The second electron transport layer (ETL) 326 may be made of the same material as the first electron transport layer (ETL) 316 , but is not limited thereto.

The second electron transport layer (ETL) 326 may be formed by applying two or more layers or two or more materials.

The first light emitting layer (EML) 324 of the second light emitting unit 320 may be formed of a yellow-green light emitting layer or a green light emitting layer. In addition, an emission peak of the emission region of the first emission layer (EML) 324 may be in a range of 520 nm to 590 nm. The first light emitting layer (EML) 324 may have a different color depending on the configuration of the organic light emitting device.

In addition, a first charge generation layer (CGL) 340 may be formed between the first light emitting unit 310 and the second light emitting unit 320 .

The third light emitting unit 330 includes a third hole transport layer (HTL) 332 , a first light emitting layer (EML) 334 , a second light emitting layer (EML) 335 and a third of the third light emitting unit 330 . An electron transport layer (ETL) 336 may be included. Although not shown in the drawings, an electron injection layer (EIL) may be additionally formed on the third electron transport layer (ETL) 336 . In addition, a hole injection layer (HIL) may be additionally configured.

The third hole transport layer (HTL) 332 is TPD (N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-bi-phenyl-4,4'-diamine) or It may be made of NPB (N,N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine), but is not necessarily limited thereto.

The third hole transport layer (HTL) 332 may be formed by applying two or more layers or two or more materials.

The third electron transport layer (ETL) 336 may be made of oxadiazole, triazole, phenanthroline, benzoxazole or benzthiazole, etc. It is not necessarily limited to this.

The third electron transport layer (ETL) 336 may be formed by applying two or more layers or two or more materials.

A second charge generating layer (CGL) 350 may be further formed between the second light emitting unit 320 and the third light emitting unit 330 . The second charge generation layer 350 adjusts the charge balance between the second light emitting unit 320 and the third light emitting unit 330 . The second charge generation layer (CGL) 350 may include an N-type charge generation layer (N-CGL) and a P-type charge generation layer (P-CGL).

The N-type charge generation layer (N-CGL) serves to inject electrons into the second light-emitting part 320 , and the P-type charge generation layer (P-CGL) serves as the third light-emitting part 330 . It serves to inject holes. The present invention is not limited thereto, and the second charge generating layer (CGL) 350 may be formed as a single layer.

The N-type charge generation layer (N-CGL) may be formed of an organic layer doped with an alkali metal such as Li, Na, K, or Cs, or an alkaline earth metal such as Mg, Sr, Ba, or Ra, respectively, but it must be It is not limited.

Each of the P-type charge generation layers (P-CGL) may be formed of an organic layer including a P-type dopant, but is not limited thereto.

The first charge generation layer (CGL) 340 may be made of the same material as the N-type charge generation layer and the P-type charge generation layer of the second charge generation layer (CGL) 350 , but is not necessarily limited thereto. no.

In addition, the first light emitting layer (EML) 334 of the third light emitting unit 330 is formed of a red light emitting layer. The second light emitting layer (EML) 335 includes a blue light emitting layer, a deep blue light emitting layer, or a sky blue light emitting layer. The emission peaks of the emission regions of the first emission layer (EML) 334 and the second emission layer (EML) 335 of the third emission part are in the range of 600 nm to 650 nm and 440 nm to 4800 nm. can

Accordingly, in the white organic light emitting device according to the third exemplary embodiment of the present invention, a blue light emitting layer and a red light emitting layer are configured in the third light emitting part. In addition, by applying the hole transport layer (HTL) as the host of the red light emitting layer, the luminous efficiency of the blue light emitting layer and the red light emitting layer can be improved, and the luminance or color gamut of the panel can be improved.

The white organic light emitting diode according to the third embodiment of the present invention is a bottom emission method, but the white organic light emitting diode according to another embodiment of the present invention is a top emission method or a dual light emission method. Emission) method can also be applied.

In addition, in the organic light emitting diode display including the organic light emitting diode according to the third exemplary embodiment of the present invention, a gate line and a data line that cross each other on a substrate and define each pixel area, and a power supply extending parallel to any one of them Wiring is positioned, and a switching thin film transistor connected to a gate line and a data line and a driving thin film transistor connected to the switching thin film transistor are positioned in each pixel area. The driving thin film transistor is connected to the first electrode 302 .

In the third embodiment of the present invention, three light emitting units have been described as an example, but at least two light emitting units are configured, and at least one light emitting unit among the two or more light emitting units may include two light emitting layers. One of the at least two light emitting layers may include the hole transport layer as a host, thereby improving light emitting intensity and luminous efficiency of the light emitting layer.

The results of manufacturing the white organic light-emitting device shown in FIG. 8 and measuring device characteristics will be described with reference to Tables 3 and 9 .

Table 3 shows the results of measuring DCI color gamut and luminance according to the first and third embodiments of the present invention.

In Table 3 and FIG. 9, in the first embodiment, a blue light emitting layer is configured as the first light emitting layer (EML) of the first light emitting part, and yellow-green is formed as the first light emitting layer (EML) of the second light emitting part. ) constitutes a light emitting layer, and a blue light emitting layer is formed as the first light emitting layer EML of the third light emitting part.

As shown in Table 3, DCI color gamut was measured to be 88% in Example 1 and 91% in Example 3. It can be seen that since the luminous efficiency of both the red light emitting layer and the blue light emitting layer of the present invention is improved, the DCI color gamut is increased compared to the first embodiment.

And, as a result of comparing the luminance, it can be seen that the third embodiment is improved by about 18% compared to the first embodiment. It can be seen that since both the red light emitting layer and the blue light emitting layer contribute to light emission of the organic light emitting device, the luminance of the panel is improved.

FIG. 9 is a view showing emission intensity of white organic light emitting diodes according to the first and third embodiments of the present invention. In FIG. 9 , the horizontal axis indicates the wavelength, and the vertical axis indicates the emission intensity.

As shown in FIG. 9 , it can be seen that the third embodiment of the present invention is a TER-TEP (Three Emission Region-Three Emission Peak) structure having three emission peaks in three light emitting portions. It can be seen that the emission peak appears at 600 nm to 650 nm, which is the emission peak of the red light emitting layer, by the red light emitting layer among the two light emitting layers of the third light emitting unit as compared with the first embodiment.

And, as shown in FIG. 9, the emission intensity of the third embodiment at 440 nm to 480 nm, which is the emission peak of the emission region of the blue light emitting layer, is slightly decreased compared to that of the first embodiment. Able to know. In addition, it can be seen that the emission intensity of the third embodiment appears at 600 nm to 650 nm, which is the emission peak of the emission region of the red emission layer.

In addition, it can be seen that the first embodiment and the third embodiment have the same emission peak at 520 nm to 590 nm, which is the emission peak of the emission region of the yellow-green emission layer. have.

Therefore, when a white organic light emitting device is composed of three light emitting units and a red light emitting layer and a blue light emitting layer are applied to one of the three light emitting units, TER-TEP (Three) having three emission peaks Emission Region-Three Emission Peak) structure can be seen. In addition, when a red light emitting layer and a blue light emitting layer are applied to one of the three light emitting units, since both the red light emitting layer and the blue light emitting layer can emit light, the red light emitting layer It can be seen that the luminescence intensity of

As described above, as two light emitting layers in one light emitting part, the red light emitting layer and the blue light emitting layer are configured, and the blue light emitting layer is configured close to the second electrode, so that the red light emitting layer and the There is an effect of improving the luminous intensity and luminous efficiency of the blue light emitting layer.

In addition, by configuring a red light emitting layer and a blue light emitting layer in one light emitting part, and applying a hole transport layer as a host of the red light emitting layer, the luminous efficiency of the blue light emitting layer and the red light emitting layer has the effect of improving

In addition, since both the blue light emitting layer and the red light emitting layer, which are two light emitting layers in one light emitting part, contribute to light emission of the organic light emitting device, the luminance and color gamut of the organic light emitting diode display may be improved.

In addition, it is possible to provide an organic light emitting device in which an increase in driving voltage or a decrease in quantum efficiency generated when two light emitting layers are configured in one light emitting unit.

In addition, by applying a TER-TEP (Three Emission Region-Three Emission Peak) structure having three emission peaks to the three light emitting units, the luminance and color gamut of the organic light emitting diode display may be improved.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made within the scope without departing from the technical spirit of the present invention. . Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The protection scope of the present invention should be construed by the claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100, 300: white organic light emitting device
101, 301: substrate 102, 302: first electrode
104, 304: second electrode 110, 310: first light emitting part
120, 320: second light-emitting unit 130, 330: third light-emitting unit
140, 340: first charge generation layer 150, 350: second charge generation layer
112, 312: first hole transport layer 122, 322: second hole transport layer
132, 332: third hole transport layer 116, 316: first electron transport layer
126, 326: second electron transport layer 136, 336: third electron transport layer
114 and 314: the first light emitting layer of the first light emitting part
124 and 324: the first light emitting layer of the second light emitting part
134 and 334: the first light emitting layer of the third light emitting part
335: the second light emitting layer of the third light emitting part

Claims (18)

a first light emitting unit positioned between the first electrode and the second electrode;
a second light emitting unit positioned above the first light emitting unit; and
and a third light emitting unit located on the second light emitting unit,
The third light emitting part consists of a red light emitting layer and a blue light emitting layer, and the host of the red light emitting layer includes a hole transport layer,
The white organic light emitting device, characterized in that the band gap of the hole transport layer is larger than the band gap of the host included in the red light emitting layer. The method of claim 1,
The blue light emitting layer of the third light emitting part is a white organic light emitting device, characterized in that it is one of a blue light emitting layer, a deep blue light emitting layer, or a sky blue light emitting layer. The method of claim 1,
The energy gap of the hole transport layer is a white organic light emitting device, characterized in that in the range of 2.8eV to 3.5eV. The method of claim 1,
The emission peak of the third emission part has a first emission peak and a second emission peak. 5. The method of claim 4,
The first emission peak is a white organic light-emitting device, characterized in that in the range of 600㎚ to 650㎚. 5. The method of claim 4,
The second emission peak is a white organic light emitting device, characterized in that in the range of 440㎚ to 480㎚. a first light emitting unit positioned between the first electrode and the second electrode;
a second light emitting unit positioned above the first light emitting unit; and
and a third light emitting unit located on the second light emitting unit,
The first light emitting part, the second light emitting part, and the third light emitting part have a TER-TEP (Three Emission Region-Three Emission Peak) structure having three emission peaks,
The third light-emitting unit includes a first light-emitting layer made of a red light-emitting layer, and a second light-emitting layer made of one of a blue light-emitting layer, a deep blue light-emitting layer, or a sky blue light-emitting layer,
The host included in the first light emitting layer includes a hole transport layer,
A band gap of the hole transport layer is larger than a band gap of a host included in the red light emitting layer. 8. The method of claim 7,
The first light emitting part is a white organic light emitting device comprising a light emitting layer made of one of a blue light emitting layer, a deep blue light emitting layer, and a sky blue light emitting layer. 8. The method of claim 7,
The second light emitting part is a white organic light emitting device comprising a light emitting layer made of one of a yellow-green light emitting layer or a green light emitting layer. delete delete 8. The method of claim 7,
The energy gap of the hole transport layer is a white organic light emitting device, characterized in that in the range of 2.8eV to 3.5eV. 8. The method of claim 7,
The second light emitting layer is a white organic light emitting device, characterized in that configured to be closer to the second electrode than the first light emitting layer. 8. The method of claim 7,
The emission peak of the first light emitting part is in the range of 440 nm to 480 nm, the emission peak of the second light emitting part is in the range of 520 nm to 590 nm, and the emission peak of the third light emitting part is in the range of 600 nm to 650 nm and 440 nm to 440 nm A white organic light emitting device, characterized in that in the range of 480 nm. a first electrode and a second electrode facing each other on the substrate; and
At least two or more light emitting units located between the first electrode and the second electrode,
At least one of the at least two light emitting units includes two light emitting layers, and one of the two light emitting layers includes a hole transport layer as a host,
A band gap of the hole transport layer is larger than a band gap of a host included in a light emitting layer including the hole transport layer as a host. 16. The method of claim 15,
The two light emitting layers are a red light emitting layer and a blue light emitting layer, characterized in that the white organic light emitting layer. 17. The method of claim 16,
The hole transport layer is a white organic light emitting device, characterized in that the host of the red light emitting layer. 17. The method of claim 16,
The white organic light emitting diode according to claim 1, wherein the blue light emitting layer is closer to the second electrode than the red light emitting layer.

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