KR102107472B1 - White Organic Light Emitting Device - Google Patents

Abstract

In the white organic light emitting device according to an embodiment of the present invention, an intermediate layer is formed between the first electrode and the second electrode disposed to face each other, and between the first electrode and the intermediate layer, a first emission layer including a first host And a second light emitting layer including a second host, and a second light emitting unit between the intermediate layer and the second electrode. According to an embodiment of the present invention, a white organic light emitting device capable of improving light emission efficiency and color gamut of a device is provided by forming the first light emitting layer and the second light emitting layer in an EDR structure or an EHS structure.

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 color gamut and light emission efficiency.

The organic light emitting device forms an organic light emitting layer between two electrodes, and injects electrons and holes into the organic light emitting layer from the two electrodes, respectively, to generate excitons according to the combination of electrons and holes, It is a device that uses the principle that light is generated when the generated exciton falls from an excited state to a ground state.

The white organic light emitting device refers to an organic light emitting device that emits white light. When two light emitting layers of complementary colors are stacked to emit white light, when white light passes through a color filter, there may be difficulty in realizing a desired color gamut by a difference between a peak wavelength region of each light emitting layer and a transmission region of the color filter. Can be. For example, when the blue light emitting layer and the yellow light emitting layer are stacked, white light is emitted while peak wavelengths are formed in the blue wavelength region and the yellow wavelength region. When the white light passes through the red, green, and blue color filters, red or green The transmittance of the wavelength region becomes lower than that of blue, thereby reducing color reproduction and luminous efficiency.

1. [White organic light emitting device] (Patent application No. 10-2009-0113752)

Therefore, in order to realize a high color gamut of the device, when the white light passes through the color filter, an emission layer of a color corresponding to a wavelength region having a relatively low transmittance is additionally formed to approximately match the transmission region of the color filter and the peak wavelength region of the emission layer. You can make up for it. In the above-mentioned example, the color reproduction rate can be increased by further forming a red or green light emitting layer on the blue light emitting layer and the yellow light emitting layer.

However, when increasing the number of light emitting layers included in the organic light emitting device to increase the color reproducibility, a phenomenon in which light emission efficiency and color reproducibility may be reduced may be caused by a difference in energy level between the light emitting layer and the light emitting layer. .

Specifically, it is as follows. In the light emitting layer, a combination of a host and a dopant used according to a peak wavelength is changed. That is, according to the peak wavelength of the light emitting layer or the characteristics of the dopant, a suitable combination can be made to improve the light emitting efficiency of the light emitting layer by using a hole-type host, an electron-type host, or a mixture of the two. For example, the red emission layer may emit light efficiently by combining an electronic host and a red dopant, and the yellow emission layer may emit light using an electron host and a hole-type host together with a yellow dopant.

The problem is that when two light emitting layers are directly contacted and disposed, the light emitting efficiency of the light emitting layer may be reduced due to a difference between a host and a dopant selected in consideration of the light emitting efficiency of each light emitting layer. In other words, the energy level difference between hosts optimized for each light-emitting layer interferes with the flow of holes or electrons transferred from one light-emitting layer to another, and thus the combination of holes and electrons generated in each light-emitting layer is affected. A difference in emission intensity at the peak wavelengths of the two emission layers occurs. For this reason, when the white light passes through the color filter, light in a wavelength region having a relatively low transmittance is generated, and as a result, luminous efficiency and color reproduction are reduced.

Accordingly, the inventors of the present invention recognized the above-mentioned problems, and devised a new structure of a white organic light emitting device capable of improving color reproducibility and luminous efficiency by considering ways to reduce the difference in luminescence intensity at the peak wavelength of the luminescent layers. .

The problem according to an embodiment of the present invention is to provide a white organic light emitting device capable of reducing a difference in emission intensity of the emission layers by applying an EDR structure to the emission layer.

Another problem according to an embodiment of the present invention is to provide a white organic light emitting device capable of improving luminous efficiency and lifetime by applying an EHS structure to a light emitting layer.

Another solution according to an embodiment of the present invention is to provide a white organic light emitting device capable of improving power consumption by reducing voltage rise due to heterogeneous interfaces caused by direct contact of a plurality of light emitting layers.

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

In the white organic light emitting device according to an embodiment of the present invention, an intermediate layer is formed between the first electrode and the second electrode disposed to face each other, and between the first electrode and the intermediate layer, a first emission layer including a first host And a second light emitting layer including a second host, and a second light emitting unit between the intermediate layer and the second electrode. According to an embodiment of the present invention, a white organic light emitting device capable of improving light emission efficiency and color gamut of a device is provided by forming the first light emitting layer and the second light emitting layer in an EDR structure or an EHS structure.

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

According to an embodiment of the present invention, by reducing the difference in the light emission intensity at the peak wavelength of the light emitting layer, there is an effect that can improve the color reproducibility and light emission efficiency.

In addition, there is an effect that can improve the life and luminous efficiency of the device.

In addition, there is an effect that power consumption can be improved by reducing the voltage rise due to the heterogeneous interface.

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

The subject matter to be solved above, the problem solving means, and the contents of the invention described in the effects do not specify the essential features of the claims, so the scope of the claims is not limited by the contents described in the contents of the invention.

1 is a cross-sectional view showing a white organic light emitting device according to an embodiment of the present invention.
2 is a view showing an energy band diagram of a first light emitting unit to which an EDR structure is applied, according to an embodiment of the present invention.
3A and 3B are diagrams illustrating an energy band diagram of a first light emitting unit to which an EHS structure is applied, according to an embodiment of the present invention.
4A and 4B are according to an embodiment of the present invention, and according to Table 1, are graphs showing emission intensity of Comparative Examples and Examples.
5 is a cross-sectional view showing a white organic light emitting device according to an embodiment of the present invention.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and the general knowledge in the technical field to which the present invention pertains. It is provided to fully inform the holder of the scope of the invention, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for describing the embodiments of the present invention are exemplary and the present invention is not limited to the illustrated matters. The same reference numerals refer to the same components throughout the specification. In addition, in the description of the present invention, when it is determined that detailed descriptions of related known technologies may unnecessarily obscure the subject matter of the present invention, detailed descriptions thereof will be omitted. When 'include', 'have', 'consist of', etc. mentioned in the specification are used, other parts may be added unless '~ man' is used. When a component is expressed as a singular number, the plural number is included unless otherwise specified.

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

In the case of the description of the positional relationship, for example, when the positional relationship of two parts is described as '~ top', '~ upper', '~ bottom', '~ side', etc., 'right' Alternatively, one or more other parts may be located between the two parts unless 'direct' is used.

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

Each of the features of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving is possible, and each of the embodiments may be independently performed with respect to each other or may be implemented together in an association relationship. It might be.

Hereinafter, a white organic light emitting device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a white organic light emitting device according to an embodiment of the present invention. The white organic light emitting device 100 according to an embodiment of the present invention, as shown in FIG. 1, between the anode 110 and the cathode 120, the first light emitting unit 140, the second light emitting unit 150 ) And the intermediate layer 130 are disposed.

The anode 110 is an anode that supplies holes and may be formed of ITO (Indum Tin Oxide), IZO (Indum Zinc Oxide), and the like, which are transparent conductive materials such as TCO (Transparent Conductive Oxide).

The cathode 120 is a cathode that supplies electrons, and may be formed of metallic materials such as gold (Au), silver (Ag), aluminum (Al), molybdenum (Mo), magnesium (Mg), or an alloy thereof. have.

The anode 110 and the cathode 120 may be referred to as a first electrode or a second electrode, respectively.

The intermediate layer 130 is a layer that serves to control the charge balance between the first light emitting unit 140 and the second light emitting unit 150, and may be composed of a layer that assists hole injection and a layer that assists electron injection, but is not limited thereto. Instead, it may be formed of a single layer.

The first light emitting unit 140 and the second light emitting unit 150 include at least one light emitting layer, and the white organic light emitting device 100 includes light of the first light emitting unit 140 and light of the second light emitting unit 150. Light is mixed to emit white light.

The first light emitting part 140 is composed of a first light emitting layer 142 and a second light emitting layer 144, and the first light emitting layer 142 and the second light emitting layer 144 are disposed in direct contact, and have different peak wavelengths. Have The first light emitting layer 142 and the second light emitting layer 144 may be variously selected in consideration of the combination of the emission wavelength ranges of the first light emitting unit 140 and the second light emitting unit 150 and the resonance distance, for example. For example, a red light emitting layer, a green light emitting layer, a yellow light emitting layer, a yellow-green light emitting layer, or a blue light emitting layer may be different from each other. The peak wavelength region of the red emission layer may be located between 600 and 640 nm, and the peak wavelength region of the green emission layer may be located between 510 and 540 nm. In addition, the peak wavelength region of the yellow emission layer may be located between 540 to 570 nm, the peak wavelength region of the yellow-green emission layer may be between 510 to 570 nm, and the peak wavelength of the blue emission layer may be between 440 to 470 nm.

However, it may be difficult for the first emission layer 142 and the second emission layer 144 to be composed of a green emission layer and a blue emission layer, respectively. Specifically, when considering the resonance (Micro-cavity) effect generated between two electrodes, since the resonance distance between the wavelength region of the blue light emitting layer and the wavelength region of the green light emitting layer is similar, energy transfer occurs easily, so A problem that the luminous efficiency of at least one of greens decreases may occur.

In FIG. 1, although the first light emitting unit 140 is illustrated as including the first light emitting layer 142 and the second light emitting layer 144 disposed in direct contact, the second light emitting unit 150 is disposed in direct contact. It may also include two light emitting layers. Also, depending on the device configuration, both the first light emitting unit 140 and the second light emitting unit 150 may include two light emitting layers.

Although not shown in FIG. 1, between the anode 110 and the second light emitting unit 150, between the second light emitting unit 150 and the intermediate layer 130, between the intermediate layer 130 and the first light emitting unit 140, the first 1 A common layer may be formed between the light emitting unit 140 and the cathode 120. The common layer may be one of a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer, but is not limited thereto, and may be selectively disposed according to the configuration and characteristics of the device.

2 is a view showing an energy band diagram of the first light emitting unit 140 to which the EDR structure is applied, according to an embodiment of the present invention. Specifically, when the first light-emitting layer 142 and the second light-emitting layer 144 of the first light emitting unit 140 are formed with EDR (Emission layers-Difference between the energy levels of the emission layers-Reduction; EDR) structure Shows the energy band diagram.

The EDR structure is a light emitting layer-energy level difference-reducing structure, and when each light emitting layer includes a host having the same characteristics when forming two light emitting layers, the energy level difference between hosts having the same characteristics It refers to a device structure for reducing the difference in emission intensity at the peak wavelength of each light emitting layer by reducing. The energy level is the lowest Unoccupied Molecular Orbital (LUMO) level in the region where the electron cannot participate in the binding and the highest energy in the region where the electron can participate in the binding (highest) Occupied Molecular Orbital (HOMO) level. Referring to the drawings, the upper surface of the square of the energy level means the LUMO level, the lower surface means the HOMO level, and the energy level may have a positive or negative value. Further, it means that the energy level is gradually increased as it goes from the HOMO level to the LUMO level, and in the opposite case, it is gradually lowered.

The first emission layer 142 includes a first hole-type host H1, a first electron-type host E1, and a first dopant D1, and the second emission layer 144 includes a second hole-type host H2. And a second electronic host E2 and a second dopant D2.

The hole-type host is TCTA [4,4 ', 4' '-tris (N-carbazolyl) -triphenylamine], CBP [4,4'-bis (carba zol-9-yl) biphenyl],

NPB [N, N'-bis (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine]

It may include one of the materials, but is not limited thereto.

The electronic host is TAZ [3-phenyl-4- (1-naphthyl) -5-phenyl-1,2,4-triazole], TPBI [1,3,5-tris (N-phenyl benzimidazole-2-yl) benzene], Balq [bis (8-bydroxyquinaldine) aluminum biphenoxide], Bphen [4,7-diphenyl-1,10-phenanthroline],

Bebq2 [bis (10-hydroxybenzo [h] quinolinato) beryllium], Alq3 [tris (8-hydroxyquinoline) aluminum] may include, but is not limited to.

Referring to FIG. 2, holes move from the first hole-type host H1 of the first light-emitting layer 142 to the second hole-type host H2 of the second light-emitting layer 144, and the former is the second light-emitting layer 144 ) Moves from the second electron-type host E2 to the first electron-type host E1 of the first light-emitting layer 142, and the moved holes and electrons combine in each light-emitting layer to generate light.

In order to describe the movement of holes, holes injected from the anode 110 pass through the first light emitting layer 142 to the second light emitting layer 144, and the HOMO level and the second hole of the first hole type host H1. When the difference A of the HOMO level of the type host H2 is large, the movement of holes becomes difficult. Specifically, when the HOMO level of the second hole-type host H2 is lower than a certain interval than the HOMO level of the first hole-type host H1, holes in the first light emitting layer 142 are removed by a barrier. 2 It is difficult to pass to the light emitting layer 144. Then, since the second light emitting layer 144 does not receive enough holes, light emission intensity and light emission efficiency are reduced. In addition, when the supply of electrons is similar, the first emission layer 142 has a higher number of holes and electrons than the second emission layer 144, so the intensity of emission may be increased, but it is necessary for the first dopant D1. The above bonding occurs, and the life of the first light emitting layer 142 is reduced. In summary, due to the difference in HOMO level between the first hole-type host H1 and the second hole-type host H2, a difference occurs in the light emission intensities of the first light-emitting layer 142 and the second light-emitting layer 144, and the desired wavelength. Since it does not emit enough light, the color gamut is reduced. In addition, due to a difference in the lifespan of the first light-emitting layer 142 and the second light-emitting layer 144, the possibility of color abnormality increases as time passes.

Similarly, to describe the movement of electrons, electrons injected from the cathode 120 pass through the second light emitting layer 144 to the first light emitting layer 142, and the second electron type host E2 and the first electron type When the difference (B) of the LUMO level of the host E1 is large, the movement of electrons becomes difficult. Specifically, when the LUMO level of the first electronic host E1 is higher than a predetermined interval than the LUMO level of the second electronic host E2, electrons of the second light emitting layer 144 are removed by a barrier. 1 It is difficult to pass to the light emitting layer 142. Then, since the first emission layer 144 does not receive enough electrons, emission intensity and emission efficiency are reduced. In addition, when the supply of holes is similar, the second emission layer 144 has a higher number of holes and electrons than the first emission layer 142, so the intensity of emission may be increased, but it is necessary for the second dopant D2. The above bonding occurs, and the life of the second light emitting layer 144 is reduced. As a result, a difference occurs in the light emission intensity of the first light emitting layer 142 and the second light emitting layer 144 due to the difference in LUMO level between the first electronic host E1 and the second electronic host E2, and the desired wavelength. Since it does not emit enough light, the color gamut is reduced. In addition, due to a difference in the lifespan of the first light-emitting layer 142 and the second light-emitting layer 144, the possibility of color abnormality increases as time passes.

Of course, the number of holes supplied to the second light emitting layer 144 is reduced, and the number of electrons supplied to the first light emitting layer 142 is reduced, and as a result, the frequency of combining holes and electrons in the first light emitting layer 142 and the second light emitting layer 144. The intensity of the light emission can be controlled by similarly controlling the light emission intensity and the light emission efficiency of the first light emitting layer 142 and the second light emitting layer 144 as a whole.

 Depending on the characteristics of the host and the dopant included in each light emitting layer, the EDR structure is applied to the device to selectively reduce the difference in the HOMO level of the hole-type hosts or the difference in the LUMO level of the electronic-type hosts, thereby improving the color reproducibility and light emission of the device. Efficiency can also be increased. In addition, since the barrier that hinders the flow of holes and electrons is lowered, the voltage consumed at the heterogeneous interface can also be lowered.

When the HOMO level of the first hole-type host H1 is lower than the HOMO level of the second hole-type host H2, the movement of the holes is easy, but when the HOMO level of the first hole-type host H2 is lower than a certain interval, the movement of the holes increases more than necessary. 1 The above-mentioned problems may occur, such as the efficiency of the light emitting layer 142 is reduced, and as a result, the color gamut is lowered. Similarly, if the LUMO level of the first electronic host E1 is lower than the LUMO level of the second electronic host E2, the movement of the electrons is easy, but if the LUMO level is lower than a certain interval, the electron movement increases more than necessary. The aforementioned problems can arise.

The difference between the HOMO level of the first hole-type host H1 and the HOMO level of the second hole-type host H2 (A) and the LUMO level of the first electronic-type host E1 and the second electronic-type host E2 The difference (B) of the LUMO level is preferably formed at about 0.3 eV or less in consideration of characteristics of the host and the dopant material of the organic light emitting device. In addition, the difference between the light emission intensities of the first light emitting layer 142 and the second light emitting layer 144 is preferably formed at about 30% or less, based on the light emission intensity of the first light emitting layer 142.

At least one of the HOMO level of the first electronic host E1 and the HOMO level of the second electronic host E2 is the HOMO level of the first hole host H1 and the HOMO level of the second hole host H2. It can be made equal or higher to facilitate the movement of holes between hole-type hosts. Further, the HOMO level of the first electronic host E1 and the HOMO level of the second electronic host E2 may be formed lower than the HOMO level of the first dopant D1 and the second dopant D2. .

Further, at least one of the LUMO level of the first hole-type host H1 and the LUMO level of the second hole-type host H2 may be selected from the HOMO level of the first electronic-type host E1 and the second electronic-type host E1. It can be formed equal or lower than the HOMO level to facilitate the movement of electrons between electronic hosts. In addition, the LUMO level of the first hole-type host H1 and the LUMO level of the second hole-type host H2 may be formed higher than the LUMO level of the first dopant D1 and the LUMO level of the second dopant D2. have.

As illustrated in FIG. 2, when one light emitting layer includes two hosts having different characteristics, there is an advantage in that it is easy to control holes and electrons with adjacent layers, but may include only one host depending on device configuration. have.

3A and 3B are diagrams illustrating an energy band diagram of a first light emitting unit 140 to which an EHS structure is applied, according to an embodiment of the present invention. Specifically, the energy band when the first light emitting layer 142 and the second light emitting layer 144 of the first light emitting unit 14 are formed of EHS (Emission layers-Hosts of the same type-Same material; EHS) structure Show the diagram.

The EHS structure is a light emitting layer-same property host-same material structure, and when forming two light emitting layers, if each light emitting layer includes a host having the same properties, a device structure using hosts having the same properties as the same material Speak.

3A is an embodiment in which the EHS structure is applied to the first light emitting layer 142 and the second light emitting layer 144, and the first hole host H1 and the second light emitting layer 144 of the first light emitting layer 142 are formed. 2 The HOMO level of the first hole-type host H1 and the HOMO level of the second hole-type host H2 are adjusted to the same by using the hole-type host H2 as the same material.

Similarly, FIG. 3B shows the first electronic host E1 using the first electronic host E1 of the first light emitting layer 142 and the first electronic host E2 of the second light emitting layer 144 as the same material. The LUMO level of and the LUMO level of the second electronic host E2 are adjusted in the same way.

In this case, since the movement of holes passing from the first emission layer 142 to the second emission layer 144 or the movement of electrons passing from the second emission layer 144 to the first emission layer 142 is facilitated, the emission intensity of the emission layers is It becomes similar and the color gamut increases. That is, the difference in emission intensity between the first emission layer 142 and the second emission layer 144 is less than the difference in emission intensity between the first emission layer 142 and the second emission layer 144 when the EHS structure is not formed. can do. In other words, the difference in emission intensity between the first emission layer 142 and the second emission layer 144 may be reduced than the difference in intensity when hosts having the same characteristics are not used with the same material. In addition, the difference in lifespan may be reduced, and color abnormality defects over time may be reduced, and the difference due to heterogeneous interfaces may be reduced to reduce the voltage consumption.

The difference between the light emission intensities of the first light emitting layer 142 and the second light emitting layer 144 may be less than about 30% based on the light emission intensity of the first light emitting layer 142.

The host characteristics of the first emission layer 142 and the host characteristics of the second emission layer 144 may be selected in consideration of a wavelength region of the emission layer and a combination with a dopant material. For example, when the first light-emitting layer 142 is a red light-emitting layer and the second light-emitting layer 144 is a yellow-green light-emitting layer, the first light-emitting layer 142 and the second light-emitting layer 144 are hole-type hosts and electronic types, respectively. A host may be included, and at this time, by applying two hole-type hosts with the same material, the emission intensity of the red emission layer and the yellow-green emission layer are similar, thereby improving color reproducibility and emission efficiency.

4A and 4B are according to an embodiment of the present invention, and according to Table 1, are graphs showing emission intensity of Comparative Examples and Examples. More specifically, it is the result when the EDR structure is applied to the light emitting part and when the EHS structure is applied.

Table 1 compares the consumption voltage and luminous efficiency according to the difference between the HOMO level of the hole-type host of the red emission layer and the HOMO level of the hole-type host of the yellow-green emission layer when the red emission layer and the yellow-green emission layer are placed in direct contact. Content. The red light emitting layer was composed of a hole-type host, an electronic host, and a dopant, and the yellow-green light-emitting layer was composed of a hole-type host, an electronic host, and a dopant.

Voltage [Volt, V] EQE ① Comparative Example 1 4.0 24.7 ② Comparative Example 2 3.9 24.7 ③ Comparative Example 3 3.8 24.2 ④ Example 1 3.6 25.3 ⑤ Example 2 3.8 24.6

Comparative Examples 1 to 3 are graphs corresponding to a case in which the difference between the HOMO levels of the hole-type host in the red emission layer and the hole-type host in the yellow-green emission layer is greater than 0.3 eV. As shown in FIG. 4A, when the HOMO level difference between hole-type hosts is large, the emission intensity and the peak wavelength when the peak wavelength is about 540 nm, based on the emission intensity when the peak wavelength is about 615 nm, The difference in emission intensity at about 610 nm is about 40 to 75% difference.

On the other hand, Example 1 is a structure in which an EHS structure is applied to a red light emitting layer and a yellow-green light emitting layer, and specifically, a structure using a hole-type host of the red light-emitting layer and a hole-type host of the yellow-green light-emitting layer as the same material. Referring to FIG. 4B, since the emission intensity when the peak wavelength is about 540 nm and the emission intensity when the peak wavelength is about 610 nm are almost similar, it is sufficiently predictable that the color reproduction rate will be improved compared to the comparative example. In addition, referring to Table 1, the voltage consumption of Example 1 was reduced by about 0.4 V to 0.2 V compared to Comparative Example, and the external quantum efficiency (EQE) was increased by about 0.6 to 1.1. EQE is the external light efficiency, and refers to the light emission efficiency when light exits the organic light emitting element, and corresponds to an integrated value of the graph in FIGS. 4A and 4B, that is, an area. Compared to the comparative example, the emission intensity when the peak wavelength was about 610 nm was slightly decreased, but when the EQE of the device was increased, it can be seen that the luminous efficiency of the device was increased.

Example 2 is a structure in which the EDR structure is applied to the red light emitting layer and the yellow-green light emitting layer. Specifically, when the difference between the HOMO level of the hole-type host of the red light-emitting layer and the HOMO level of the hole-type host of the yellow-green light-emitting layer is lower than 0.3 eV It is a graph corresponding to. As shown in FIG. 4B, when the peak wavelength is about 610 nm, the difference in emission intensity when the peak wavelength is about 540 nm and the emission intensity when the peak wavelength is about 610 nm is about 30. It can be confirmed that the%, the difference in the light emission intensity compared to the comparative example is expected to be improved color reproduction. In addition, referring to Table 1, the voltage consumption of Example 2 was reduced by about 0.2 V compared to Comparative Example, and the EQE was increased by about 0.4. In the case of Example 2, some of the comparative examples have the same power consumption or a portion in which EQE decreases slightly, which can be seen as the error range of the dispersion in the experiment, and when the overall trend of the experiment was determined, the aforementioned The effect of reducing the difference in luminescence intensity, increasing luminous efficiency, and reducing the consumption voltage can be sufficiently confirmed.

5 is a cross-sectional view showing a white organic light emitting device 500 according to an embodiment of the present invention. In describing the present embodiment, descriptions of the same or corresponding components as the previous embodiment will be omitted. More specifically, the anode 510, the cathode 520, the first light emitting unit 540, the intermediate layer 530, and the second light emitting unit 550 constituting the white organic light emitting device 500 of the present embodiment are shown in FIG. It may correspond to the anode 110, the cathode 120, the first light emitting unit 140, the intermediate layer 130, and the second light emitting unit 150 described with reference to 1. That is, the white organic light emitting device 500 according to an embodiment of the present invention with reference to FIG. 5 may further include a third light emitting unit 560 and an intermediate layer 532.

The third light emitting unit 560 includes at least one light emitting layer, and the white organic light emitting device 500 includes light from the first light emitting unit 540, the second light emitting unit 550, and the third light emitting unit 560. Mixed to emit white light. Also, the third light emitting unit 560 may include two light emitting layers disposed in direct contact with an EDR structure or an EHS structure. By additionally forming the third light emitting unit 560, the number of light emitting layers to be included increases, so that the light emission efficiency of the white organic light emitting device 500 increases, and it may be advantageous to improve the color reproducibility by combining the light emitting layers.

The intermediate layer 130 is a layer that serves to control the charge balance between the first light emitting unit 540 and the third light emitting unit 560, and may be composed of a layer that assists hole injection and a layer that assists electron injection, but is not limited thereto. Instead, it may be formed of a single layer.

In addition, a common layer is additionally formed between the first light emitting unit 540 and the intermediate layer 532, between the intermediate layer 532 and the third light emitting unit 560, and between the third light emitting unit 560 and the cathode 520. It may be.

The above-described embodiment has been described as two light emitting layers disposed in direct contact, but may be extended to three or more light emitting layers. In other words, when forming three or more light emitting layers arranged in direct contact, when each light emitting layer includes a host having the same characteristics, the difference in the HOMO level or the LUMO level between the hosts is reduced, or the same material is used. By configuring the device, it is possible to reduce the difference in light emission intensity of each light emitting layer, improve the color reproducibility and light emission efficiency of the device, and reduce the voltage consumed by heterogeneous interfaces.

The first light emitting layer and the second light emitting layer may be arranged to directly contact.

The first emission layer and the second emission layer may be one of a red emission layer, a green emission layer, a yellow emission layer, a yellow-green emission layer, and a blue emission layer, respectively, and the first emission layer and the second emission layer may be different layers.

When the first emission layer is a green emission layer, the second emission layer may be a layer other than the blue emission layer.

The difference between the intensity at the peak wavelength of the first emission layer and the intensity at the peak wavelength of the second emission layer may be reduced than the difference in intensity when the first emission layer and the second emission layer are not formed of an EHS structure. .

Based on the intensity at the peak wavelength of the first emission layer, the difference between the intensity at the peak wavelength of the first emission layer and the intensity at the peak wavelength of the second emission layer may be 30% or less.

When the first emission layer is a red emission layer and the second emission layer is a yellow-green emission layer, the first hole-type host and the second hole-type host may be the same material.

The first host of the first emission layer and the second host of the second emission layer may be hole-type hosts.

The difference between the HOMO level of the first host of the first emission layer and the HOMO level of the second host of the second emission layer may be 0.3 eV or less.

Based on the intensity at the peak wavelength of the first emission layer, the difference between the intensity at the peak wavelength of the first emission layer and the intensity at the peak wavelength of the second emission layer may be 30% or less.

The first host of the first light emitting layer and the second host of the second light emitting layer may be electronic hosts.

The difference between the LUMO level of the first host of the first emission layer and the LUMO level of the second host of the second emission layer may be 0.3 eV or less.

The embodiments of the present invention have been described in more detail with reference to the accompanying drawings, but the present invention is not necessarily limited to these embodiments, and may be variously modified 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 scope of protection of the present invention should be interpreted by the claims, and all technical spirits within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

100, 500: white organic light emitting device
110, 510: anode
120, 520: cathode
130, 530, 532: middle floor
140, 540: first light emitting unit
150, 550: second light emitting unit
560: third light emitting unit
H1: 1st hole type host
H2: 2nd hole type host
E1: first electronic host
E2: Second electronic host
D1: first dopant
D2: second dopant
A: The difference between the HOMO level of the first hole-type host and the HOMO level of the second hole-type host
B: The difference between the LUMO level of the first electronic host and the LUMO level of the second electronic host

Claims (17)

A first light emitting unit located between the anode and the cathode, and comprising a first light emitting layer including a first hole host and a first electron host and a second light emitting layer including a second hole host and a second electron host; and
The second light emitting unit is located between the anode and the cathode and includes at least one light emitting layer.
The first light emitting layer and the second light emitting layer,
It is formed of a light emitting layer-Emission layers-Hosts of the same type-Same material structure,
The difference between the emission intensity at the peak wavelength of the first emission layer and the emission intensity at the peak wavelength of the second emission layer does not form the first emission layer and the second emission layer as the emission layer-same characteristic host-same material structure. White organic light emitting device, which is reduced than the difference in light emission intensity in the case. According to claim 1,
A white organic light emitting device, in which the first light emitting layer and the second light emitting layer are disposed in direct contact. According to claim 2,
The first light emitting layer and the second light emitting layer, respectively,
A white organic light emitting device, wherein the red light emitting layer, the green light emitting layer, the yellow light emitting layer, the yellow-green light emitting layer, or the blue light emitting layer is one of the first light emitting layers and the second light emitting layers being different layers. According to claim 3,
When the first light emitting layer is a green light emitting layer,
The second emission layer is a layer other than the blue emission layer, a white organic light emitting device. delete According to claim 1,
Based on the light emission intensity at the peak wavelength of the first light emitting layer,
A white organic light emitting device having a difference between an emission intensity at a peak wavelength of the first emission layer and an emission intensity at a peak wavelength of the second emission layer is 30% or less. According to claim 3,
When the first light emitting layer is a red light emitting layer and the second light emitting layer is a yellow-green light emitting layer, the first hole-type host and the second hole-type host are the same material, a white organic light emitting device. An intermediate layer formed between the first electrode and the second electrode disposed opposite to each other;
A first light emitting unit formed between the first electrode and the intermediate layer, and comprising a first light emitting layer including a first host and a second light emitting layer including a second host; and
It includes; a second light-emitting portion formed between the intermediate layer and the second electrode;
The first light emitting layer and the second light emitting layer,
Emission layers-Difference between the energy levels of the emission layers-Reduction structure is formed,
Based on the light emission intensity at the peak wavelength of the first light emitting layer,
A white organic light emitting device having a difference between an emission intensity at a peak wavelength of the first emission layer and an emission intensity at a peak wavelength of the second emission layer is 30% or less. The method of claim 8,
A white organic light emitting device, in which the first light emitting layer and the second light emitting layer are disposed in direct contact. The method of claim 9,
The first light emitting layer and the second light emitting layer, respectively,
Red light emitting layer, green light emitting layer, yellow light emitting layer, yellow-green light emitting layer, one of the blue light emitting layer,
The first light emitting layer and the second light emitting layer are different layers, a white organic light emitting device. The method of claim 10,
When the first light emitting layer is a green light emitting layer,
The second emission layer is a layer other than the blue emission layer, a white organic light emitting device. The method of claim 11,
The first host of the first light emitting layer and the second host of the second light emitting layer are hole-shaped hosts, a white organic light emitting device. The method of claim 12,
The difference between the HOMO level of the first host of the first emission layer and the HOMO level of the second host of the second emission layer is 0.3 eV or less. delete The method of claim 11,
The first host of the first light emitting layer and the second host of the second light emitting layer are electronic hosts. The method of claim 15,
The difference between the LUMO level of the first host of the first emission layer and the LUMO level of the second host of the second emission layer is 0.3 eV or less. delete

Images