KR20120072815A - White organic emitting device - Google Patents

Abstract

PURPOSE: A white organic light emitting device is provided to improve a viewing angle by applying a blue light emitting layer with two peaks to a blue light emitting unit. CONSTITUTION: An anode(100) and a cathode(140) are formed on a substrate(50) to face each other. A charge generating layer(120) is formed between the anode and the cathode. A blue light emitting layer(110) with two peaks is formed between the anode and the charge generating layer. A phosphorescent light emitting layer(130) is formed between the cathode and the charge generating layer. First to fourth common layers(105,115,125,135) are successively formed between the phosphorescent light emitting layer and the cathode.

Description

White Organic Emitting Device

The present invention relates to an organic light emitting device, and more particularly, to a white organic light emitting device in which a blue light emitting layer having two peaks is applied to a blue light emitting unit in a stack structure of a blue light emitting unit and a phosphorescent unit to improve a viewing angle and efficiency.

In recent years, as the information age has entered, the display field for visually expressing electrical information signals has been rapidly developed. In response, various flat panel displays having excellent performance of thinning, light weight, and low power consumption have been developed. Display Device has been developed and is rapidly replacing the existing Cathode Ray Tube (CRT).

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

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

In the organic light emitting diode display, it is necessary to form an organic light emitting layer, and a deposition method using a shadow mask is conventionally used to form the organic light emitting layer.

However, in the case of a large area, the shadow mask is drooped due to its load, which makes it difficult to use it several times and causes defects in the formation of the organic light emitting layer pattern. Therefore, an alternative method is required.

There is a white organic light emitting display device as one of several methods that have been proposed to replace the shadow mask.

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

The white organic light emitting diode display is a method of depositing each layer between an anode and a cathode without a mask when forming a light emitting diode, and forming organic layers including an organic light emitting layer in a vacuum state by sequentially changing their components.

The white organic light emitting diode display is a device having various uses, such as a thin light source, a backlight of a liquid crystal display, or a full color display employing a color filter.

In consideration of the lifespan and the power consumption, the white organic light emitting diode has a structure in which all of the light emitting layers stacked are fluorescent structures or stack structures of fluorescent units and light emitting units. Common to both structures is the use of a blue fluorescent layer using only singlet exciton.

Although the efficiency of the blue phosphor layer has reached a satisfactory level in recent years, improvements in terms of lifespan are still urgent. For this reason, a white organic light emitting device to which a blue fluorescent layer is applied has been mainly developed. However, life and power consumption improvement is limited due to the efficiency problem of the above-mentioned blue fluorescence. In particular, to solve this problem, there is a need for a method of improving the efficiency and lifetime of the blue fluorescent layer having an internal quantum efficiency of 25%.

In addition, since blue fluorescence is less efficient than phosphorescent materials of the remaining colors, in a two-stacked white organic light emitting device in which a blue light emitting unit including a blue fluorescent layer and a phosphorescent unit are stacked, the white fluorescence is white depending on the viewing angle due to the difference in efficiency according to the light emission color. There is a problem that the color change of the organic light emitting device is large.

The present invention has been made to solve the above problems, in the stack structure of the blue light emitting unit and the phosphorescent unit, by applying a blue light emitting layer having two peaks to the blue light emitting unit provides a white organic light emitting device that improves the viewing angle and efficiency There is a purpose.

The white organic light emitting device of the present invention for achieving the above object includes an anode and a cathode facing each other on a substrate; and a charge generation layer formed between the anode and the cathode; and between the anode and the charge generation layer, A first stack comprising a blue light emitting layer having two light emission peaks; And a second stack comprising a phosphorescent layer between the charge generating layer and the cathode.

The first light emission peak of the two light emission peaks of the blue light emitting layer is 430 nm to 470 nm, the second light emission peak is 470 nm to 490 nm, and the difference between the first light emission peak and the second light emission peak is 1 nm to 40 nm.

The blue light emitting layer includes a fluorescent light emitting material.

The phosphorescent layer may be a light emitting layer doped with phosphorescent red and green dopants in one host or a light emitting layer doped with a yellow-green dopant in one host.

In addition, first to fourth common layers may be sequentially formed between the anode and the blue light emitting layer, between the blue light emitting layer and the charge generating layer, between the charge generating layer and the phosphorescent light emitting layer, and between the phosphorescent light emitting layer and the cathode.

Here, the first common layer and the second common layer have a triplet energy level higher than that of the host of the blue light emitting layer, and the third common layer has a triplet energy level higher than that of the host of the phosphorescent light emitting layer.

The second common layer includes first and second electron transport layers, and the first electron transport layer has a triplet energy level higher than that of the blue light emitting layer and minimizes diffusion of alkali metal into the blue light emitting layer. The second electron transport layer may be selected from a bphen-based organic material capable of injecting electrons through doping of an alkali metal.

In addition, the first common layer and the third common layer are respectively adjacent to the blue light emitting layer and the phosphorescence generating layer, and include a first hole transport layer and a second hole transport layer. Here, the first hole transport layer and the first electron transport layer is 0.01 eV to 1.0 eV triplet energy level higher than the host of the blue light emitting layer, the second hole transport layer is 0.01 eV to 1.0 eV triplet than the host of the phosphorescent light emitting layer It is preferable that the energy level is high.

And it is preferable that the said alkali metal is Li.

Meanwhile, the charge generation layer includes an N-type charge generation layer adjacent to the first stack and a P-type charge generation layer adjacent to the second stack. In addition, a buffer layer may be further included between the N-type charge generation layer and the P-type charge generation layer.

In addition, the total thickness from the upper portion of the substrate to the lower portion of the cathode is 3000 kPa to 3400 kPa, the distance between the blue light emitting layer and the cathode is 1600 kPa to 2000 kPa, and the distance between the phosphorescent light emitting layer and the cathode is 200 kPa to 600 kPa. can do. Alternatively, the total thickness from the upper part of the substrate to the lower part of the cathode may be 4000 to 4500 m, the distance between the blue light emitting layer and the cathode may be 1600 to 2000 m and the distance between the phosphorescent layer and the cathode electrode may be 200 to 600 mW. Can be.

The white organic light emitting diode of the present invention as described above has the following effects.

When the tandem element is implemented by applying two-peak blue fluorescent unit, the position of the emission peak of the blue region decreases to a similar degree of the emission peak of the phosphorescent unit according to the viewing angle, thereby reducing the color change of white.

Therefore, the degree of luminous degradation can be prevented according to the change of the viewing angle.

1 is a cross-sectional view showing a white organic light emitting device of the present invention
2 is a graph showing the light intensity according to the wavelength of the fluorescent unit applied to FIG.
3A and 3B are cross-sectional views illustrating the configuration of a fluorescent unit including a blue light emitting layer having wavelengths of 1 and 2 peaks, respectively.
4 is a graph illustrating quantum efficiency according to luminance of FIGS. 3A and 3B;
5A and 5B are sectional views showing the structure of a comparative example and an experimental example of a white organic light emitting device of the present invention;
6 is a graph showing light intensity according to wavelengths for FIGS. 5A and 5B;
7A and 7B are graphs showing wavelength vs. light intensity characteristics when applying comparative examples and experimental examples of the white organic light emitting diode of the present invention.
8 is a graph showing Δu'v 'according to a viewing angle in Comparative Examples and Experimental Examples of the white organic light-emitting device of the present invention.

Hereinafter, with reference to the accompanying drawings showing an embodiment of the present invention, the white organic light emitting device of the present invention more fully disclosed.

However, the invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In this figure, the size and relative size of layers and regions may be exaggerated for clarity.

1 is a cross-sectional view illustrating a white organic light emitting diode according to an exemplary embodiment of the present invention, and FIG. 2 is a graph showing light intensity according to a wavelength of a fluorescent unit applied to FIG. 1.

As shown in FIG. 1, the white organic light emitting diode of the present invention includes a positive electrode 100 and a negative electrode 140 facing each other on a substrate 50, and a charge generation layer formed between the positive electrode 100 and the negative electrode 140 ( 120 and a first stack including a blue light emitting layer 110 having two emission peaks between the anode 100 and the charge generation layer 120 and between the charge generation layer 120 and the cathode 140. And a second stack including a phosphorescent light emitting layer 130.

In FIG. 2, the emission peak of the blue emission layer 110 is represented by the first peak at 458 nm and the second emission peak at 480 nm. However, the present invention is not necessarily limited thereto, and the first emission peak may be 430 nm to 470 nm, and the second emission peak may be applied in the range of 470 nm to 490 nm. At this time, the difference between the first emission peak and the second emission peak is 1 nm to 40 nm.

As such, when the blue light emitting layer in the first stack is within the ranges of the first and second light emission peaks, the blue light emission efficiency decreases close to the decrease in the phosphorescence efficiency of the second stack according to the viewing angle. It occurs at a similar level in phosphorescent light emission, making it impossible to recognize deterioration in image quality.

The blue light emitting layer 110 may be formed of any fluorescent material or a phosphorescent light emitting material. In this case, the blue light emitting layer 110 includes a dopant of blue fluorescent or blue phosphorescent components in one host.

In the following experiment, the blue light emitting layer 110 is an example using a fluorescent light emitting material.

The phosphorescent light emitting layer 130 is a material that emits white light together with the blue light emitting layer of the lower first stack. The phosphorescent light emitting layer 130 may be a light emitting layer doped with a red dopant and a green dopant of phosphorescent in one host, or yellow green in one host. yellow-green) may be a light emitting layer doped with a dopant. In some cases, it may be used as a combination of other emission colors.

The anode 100 is made of a material such as indium tin oxide (ITO) or indium zinc oxide (IZO) as a transparent conductive material.

The cathode 140 is formed of aluminum and a reflective metal material, such as metals such as gold (Au), aluminum (Al), molybdenum (Mo), chromium (Cr), and copper (Cu). Through this structure, white light is emitted by mixing blue light in the first stack and "red light + green light" or "yellow green" light in the second stack in a bottom emission method.

In addition, between the anode 100 and the blue light emitting layer 110, between the blue light emitting layer 110 and the charge generating layer 120, between the charge generating layer 120 and the phosphorescent light emitting layer 130 and the phosphorescent light emitting layer 130. ) And the cathode 140, the first to fourth common layers 105, 115, 125, and 135 are sequentially formed.

Here, the first common layer 105 may be a first hole injection layer (HIL) and a first hole transport layer (HTL) formed sequentially from the bottom. Only one layer of the first hole transport layer may be formed as the first common layer 105.

The first common layer 105 may be set to have a triplet energy level higher than that of the host of the blue light emitting layer 110. This is to trap excitons of the blue light emitting layer 110 in the blue light emitting layer without using the adjacent first hole transport layer, and to use the same for light emission. In this case, the triplet energy state of the first hole transport layer of the common layer 105 may be set to be 0.01 eV to 1.0 eV triplet energy level higher than that of the blue layer host.

Similarly, the third common layer 125 may include a second hole injection layer and a second hole transport layer, and in particular, the second hole transport layer may have a triplet energy level higher than that of the host of the phosphorescent layer 130. The triplet energy level of the second hole transport layer is preferably 0.01 eV to 1.0 eV higher than the triplet energy level of the host of the phosphorescent light emitting layer 130.

The second common layer 115 may include first and second electron transport layers sequentially formed from the bottom.

Here, the first electron transport layer has a triplet energy level higher than that of the blue light emitting layer 110, and is selected from a material that minimizes diffusion of alkali metal into the blue light emitting layer 110, and the second electron transport layer is an alkali metal. It is preferable to select from bphen-based organic materials that can inject electrons through doping.

Here, the alkali metal may be Li.

In addition, the fourth common layer 135 includes a third electron transport layer. In some cases, the same configuration as that of the second common layer 115 may be adopted.

In addition, the fourth common layer 135 may further include an electron injection layer adjacent to the cathode 140.

Meanwhile, the charge generation layer (CGL) 120 may include an N-type charge generation layer 120a adjacent to the first stack and a P-type charge generation layer 120b adjacent to the second stack. Include. In addition, a buffer layer may be further included between the N-type charge generation layer 120a and the P-type charge generation layer 120b.

Here, the charge generation layer 120 is to control the charge balance between the first stack and the second stack, it may be formed as a single layer in some cases. The N-type charge generation layer 120a adjacent to the first stack functions as an electron injection layer of the first stack, and the P-type charge generation layer 120b functions as a hole injection function of the second stack.

On the other hand, the reason why two peak light emitting materials are used for the blue light emitting layer included in the first stack of the white organic light emitting device of the present invention will be described.

In the two-stack white organic light emitting device of the lower blue unit and the upper phosphorescent unit, the peak of photoluminescence (PL) of the blue light emitting layer included in the blue unit and the emission peak of the organic laminate in the white organic light emitting device structure ( The efficiency of the light emitting device is determined by the product of the emission peak).

However, as the viewing angle becomes larger gradually from the front (viewing angle 0 °), the emission peak shifts, and the area where the blue photoluminescence peak and the red and green phosphorescence photoluminescence peaks overlap with each other is different. When the overlap area is reduced, the efficiency decreases, and when the decreasing ratios are different, the viewing angle characteristic shows poor results. In particular, as the viewing angle is increased, the optical peak is lowered at the blue wavelength with low luminous efficiency, and through this, the luminous intensity of colors other than blue is more prominent.

In order to improve the deterioration in image quality due to the change in viewing angle, the material of the blue light emitting layer used for the blue light emitting unit has a 2 peak blue characteristic, and as shown in FIG. 2, the first peak is selected at a lower wavelength than the general blue peak, The two peaks were chosen at higher wavelengths, allowing the blue spectrum to be more widely distributed. As a result, by reducing the optical peak change of the blue wavelength in accordance with the change in the viewing angle, the blue light emission efficiency and the phosphorescence light emission efficiency are maintained to a similar degree. As a result, by reducing the change in the color coordinates of the displayed white, the viewer is prevented from deteriorating the visual sense that the other color is noticeable due to the lack of a specific color even when the viewing angle is changed.

Meanwhile, the white organic light emitting device of the present invention is a high efficiency long life device using triplet extinction (TTA: Triplet-triplet-Annihilation, hereinafter TTA).

In this case, the device's limited internal quantum efficiency (IQE) of 25%, but theoretically improved to about 50% due to the contribution of delayed fluorescence through the TTA.

In order to contribute to efficiency through TTA, it is necessary to design the device structure so that the efficiency of Trip-triplet annihilation (TTA) can be easily generated in each light emitting layer (blue light emitting layer and phosphorescent light emitting layer).

Accordingly, in order to contribute to the TTA, it is important to select the first and third common layers adjacent to each light emitting layer (in particular, the hole transport layer (HTL)) and the second and fourth common layers (electron transport layer (ETL)). That is, in order to effectively trap triplet excitons in each light emitting layer, the triplet energy of the first and second common layers must be higher than the host triplet energy of each light emitting layer.

In this case, these hole transport layers consider high triplet energy characteristics compared to the host of each light emitting layer and high Occupied Molecular Orbital (HOMO) level with the hole injection layer.

In addition, these electron transport layers consider high triplet energy characteristics and hole blocking characteristics of the host of each light emitting layer.

ΔEst (exchange energy between singlet and triplet) of each host and dopant of each light emitting layer is small to facilitate the transition of triplet to singlet through the TTA phenomenon.

When the carrier mobility of the first and second common layers is optimized while the above conditions are satisfied, a high efficiency light emitting device can be obtained.

On the other hand, the thickness of each layer in the white organic light emitting device described above is considered as follows.

For example, referring to FIG. 1, the total thickness from the top of the substrate 50 to the bottom of the cathode 140 is 3000 m 3400 m 3, and the distance between the blue light emitting layer 110 and the cathode 140 is 1600 m 3. The distance between the phosphorescent light emitting layer 130 and the cathode 140 may be 200 mW to 600 mW. In this case, the thickness of the anode 100 is about 300 to 1000 mW, preferably 500 mW. In this thickness, the first common layer 105, which has an important meaning, was observed to have a high luminous efficiency as an organic laminate of a white organic light emitting element when thinned.

Alternatively, the total thickness from the upper part of the substrate to the lower part of the cathode may be 4000 to 4500 m, the distance between the blue light emitting layer and the cathode may be 1600 to 2000 m and the distance between the phosphorescent layer and the cathode electrode may be 200 to 600 mW. It may be. In this case, the thickness of the anode 100 is applied in the same manner as described above, which means that the luminous efficiency is high when the thickness of the first common layer 105 is thicker than that of other layers.

Hereinafter, the example which experimented using the blue light emitting material which has one peak and the blue light emitting material which has two peaks of this invention is demonstrated.

3A and 3B are cross-sectional views illustrating a fluorescent unit including a blue light emitting layer having wavelengths of 1 and 2 peaks, respectively, and FIG. 4 is a graph showing quantum efficiency according to luminance of FIGS. 3A and 3B. .

3A and 3B show a blue light emitting unit of a white organic light emitting diode, respectively, B1 indicates that the material characteristic of the blue light emitting layer 250 is one peak, and B2 indicates that the material characteristic of the blue light emitting layer 150 is two peaks. Indicates a difference in cognition.

The devices B1 and B2 are each formed on the substrates 70 and 50 in turn, and are formed sequentially between the anodes 200 and 100 and the cathodes 280 and 180, and between the anodes 200 and 100 and the cathodes 280 and 180, respectively. The first common layer 245 and 145, the blue light emitting layers 250 and 150, and the second common layer 255 and 155 are included.

The devices B1 and B2 have the same configuration and characteristics except that the peaks of the blue light emitting layers 250 and 150 are one peak or two peaks.

As shown in FIG. 4, it can be seen that in device B2 having 2 peak blue light emission, External Quantum Efficincy (EQE) is improved over device B1 having 1 peak blue light emission. In particular, in the low luminance region 0 ~ 3000 [Cd / m2], it can be seen that the external quantum efficiency is relatively improved.

Device Blue emission characteristics Volt (V) Cd / A QE (%) CIEx CIEy λp (nm) B1 1 peak 3.7 10.0 9.9 0.127 0.152 464 B2 2 peak 3.6 11.5 10.7 0.140 0.155 456, 480

In addition, it can be seen from Table 1 that the structure of the device B2 has low driving voltage consumption and improved luminance, quantum efficiency and color coordinates.

Hereinafter, an example in which the white organic light emitting diode is applied by applying the aforementioned B1 and B2 to the first stack will be described.

5A and 5B are cross-sectional views illustrating the structure of a comparative example and an experimental example of a white organic light emitting diode according to the present invention, and FIG. 6 is a graph showing light intensity according to wavelengths of FIGS. 5A and 5B.

FIG. 5B follows the structure of FIG. 1 described above, wherein the phosphorescent light emitting layer of the second stack is a light emitting layer doped with phosphorescent red and green dopants together in one host, and the blue light emitting layer has two peak characteristics. It is characterized by being a material. FIG. 5A shows a difference in that the blue light emitting layer has one peak characteristic compared to FIG. 5B. Respectively, the structure of FIG. 5A is referred to as A1, and the structure of FIG. 5B is referred to as A2.

As shown in FIG. 6, in the A2 structure compared to the A1 structure, although the highest light intensity is low at the blue wavelength, two peaks occur at the blue wavelength, indicating that the spectrum is broader.

Device Volt (V) Cd / A QE (%) CIEx CIEy A1 7.1 49.4 28.0 0.308 0.316 A2 7.0 54.7 31.3 0.314 0.315

On the other hand, the devices A1 and A2 have a two-stack structure compared to the devices B1 and B2 described above, and the driving voltage, the generated luminance, and the quantum efficiency are all relatively high.

In addition, in Table 2, in the white organic light emitting device A2 including the blue light emitting layer having 2 peaks, the driving voltage is low, but the luminance, the quantum efficiency, and the CIE coordinate system are all improved.

Hereinafter, the light intensity change for each wavelength of the actual viewing angle in the apparatuses A1 and A2 will be described.

7A and 7B are graphs showing wavelength vs. light intensity characteristics when applying comparative examples and experimental examples of the white organic light emitting diode of the present invention.

As shown in FIG. 7A, in the white organic light emitting device having the blue light emitting layer having 1 peak, the light intensity is remarkably decreased as the viewing angle increases, particularly in the blue wavelength band. At this time, the change in light intensity is not large in the remaining wavelength band.

The change in the emission intensity of the blue wavelength band according to the change of the viewing angle is such that the PL area of the blue wavelength band having a small FWHM (full width at half maximum) having a small emission peak moving in accordance with the viewing angle is greatly reduced. Because.

On the other hand, as shown in FIG. 7B, in the white organic light emitting device having the blue light emitting layer having 2 peaks, the light intensity is reduced to a similar level in the blue wavelength band or the remaining wavelength band, even if the viewing angle is increased.

That is, by applying the device A2 element, the two-peak blue unit having a larger half-value width results in a smaller reduction ratio of the overlapping area and a decrease in luminous efficiency even when the emission peak changes depending on the viewing angle.

The comparative examples and the experimental examples described above were measured by tilting at 0 ° viewed from the front at 15 °, 30 °, 45 °, and 60 °, and the change in wavelength band according to the change in the viewing angle is uniform in the wavelength range. This means that the light intensity is reduced so much that there is no deterioration in the visibility of a particular color due to the change in viewing angle.

8 is a graph showing Δu'v 'according to the viewing angle in the comparative example and the experimental example of the white organic light emitting diode of the present invention.

Referring to Δu'v 'results according to the viewing angles of the device A1 and the device A2 as shown in FIG. 8, it can be seen that the viewing angle improvement effect of the device A2 is remarkable after the viewing angle is 30 degrees.

Particularly, in the case of 60 degrees, in A2 having 2 peaks compared to A1 having 1 peak, it can be seen that the result is improved from 0.046 to 0.025.

This is similar to the decrease in phosphorescence efficiency even in the blue wavelength range, resulting in a reduction in the color coordinate change of white.

That is, in the white organic light emitting diode of the present invention, a broad blue unit having two peaks is applied to reduce the blue efficiency close to the efficiency reduction width of phosphorescence according to the viewing angle, thereby improving the viewing angle of the tandem type white organic light emitting diode.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

50: substrate 100: anode
105: first common layer 110: blue light emitting layer
115: second common layer 120: charge generating layer
125: third common layer 130: phosphorescent light emitting layer
135: fourth common layer 140: cathode

Claims (15)

An anode and a cathode opposed to each other on a substrate;
A charge generation layer formed between the anode and the cathode;
A first stack comprising a blue light emitting layer having two emission peaks between the anode and the charge generating layer; And
And a second stack including a phosphorescent light emitting layer between the charge generating layer and the cathode. The method of claim 1,
The first emission peak of the two emission peaks of the blue light emitting layer is 430nm to 470nm, the second emission peak is 470nm to 490nm, the difference between the first emission peak and the second emission peak is 1nm to 40nm Light emitting element. The method of claim 1,
The blue light emitting layer is a white organic light emitting device comprising a fluorescent light emitting material. The method of claim 1,
The phosphorescent light emitting layer is a white organic light emitting device, characterized in that the phosphorescent red and green dopant doped together in one host. The method of claim 1,
The phosphorescent light emitting layer is a white organic light emitting device, characterized in that the light emitting layer doped with a yellow-green dopant in one host. The method of claim 1,
First to fourth common layers are sequentially formed between the anode and the blue light emitting layer, between the blue light emitting layer and the charge generating layer, between the charge generating layer and the phosphorescent light emitting layer, and between the phosphorescent light emitting layer and the cathode. Light emitting element. The method according to claim 6,
The first common layer and the second common layer have a triplet energy level higher than that of the host of the blue light emitting layer, and the third common layer has a triplet energy level higher than that of the host of the phosphorescent light emitting layer. . 8. The method of claim 7,
The second common layer includes first and second electron transport layers,
The first electron transport layer has a triplet energy level higher than that of the blue light emitting layer, and is selected from a material that minimizes diffusion of alkali metal into the blue light emitting layer.
The second electron transport layer is a white organic light emitting device, characterized in that selected from the organic material of the bphen series capable of electron injection through the doping of alkali metal. The method of claim 8,
And the first common layer and the third common layer are adjacent to the blue light emitting layer and the phosphorescent layer, respectively, and include a first hole transport layer and a second hole transport layer. The method of claim 9,
The first hole transport layer and the first electron transport layer are 0.01 eV to 1.0 eV triplet energy level higher than the host of the blue light emitting layer,
The second hole transport layer is a white organic light emitting device, characterized in that the triplet energy level of 0.01eV to 1.0eV higher than the host of the phosphorescent layer. The method of claim 8,
The alkali metal is a white organic light emitting device, characterized in that Li. The method of claim 1,
And the charge generation layer comprises an N-type charge generation layer adjacent to the first stack and a P-type charge generation layer adjacent to the second stack. 13. The method of claim 12,
The white organic light emitting device of claim 1, further comprising a buffer layer between the N-type charge generating layer and the P-type charge generating layer. The method of claim 1,
The total thickness from the upper part of the substrate to the lower part of the cathode is 3000 kPa to 3400 kPa, the distance between the blue light emitting layer and the cathode is 1600 kPa to 2000 kPa, and the distance between the phosphorescent light emitting layer and the cathode is 200 kPa to 600 kPa. A white organic light emitting device. The method of claim 1,
The total thickness from the upper part of the substrate to the lower part of the cathode is 4000 to 4500 m, the distance between the blue light emitting layer and the cathode is 1600 to 2000 m and the distance between the phosphorescent layer and the cathode is 200 to 600 mW. White organic light emitting element.

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