KR20170123557A - Organic Light Emitting Element and Organic Light Emitting Display Device - Google Patents

Abstract

The present invention relates to an organic light emitting element where two or more adjacent light emitting layers are applied to a stack, and an organic light emitting display using the same. The organic light emitting element of the organic light emitting display device includes a reflective electrode and a transparent electrode facing each other, and a stack of a plurality of layers between the reflective electrode and the transparent electrode, and a charge generation layer between the stacks. At least one of the stacks of the plurality of layers is in contact with each other, and may include first and second light emitting layers having different emission peaks. The light emitting efficiency and the lifetime of the light emitting layer can be increased.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device, and more particularly, to a white organic light emitting device in which two or more adjacent light emitting layers are stacked on one stack and an OLED display using the same.

Recently, the field of display that visually expresses electrical information signals has rapidly developed as the information age has come to a full-fledged information age. In response to this, various flat panel display devices (flat display devices) having excellent performance such as thinning, light- Display Device) has been developed to replace CRT (Cathode Ray Tube).

Specific examples of such flat panel display devices include a liquid crystal display device (LCD), a plasma display panel (PDP), a field emission display (FED) (Organic Light Emitting Device: OLED).

Among these, an organic light emitting display is considered as a competitive application for not requiring a separate light source, compacting the device, and displaying a clear color image.

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

However, in the case of a large area of the shadow mask, a phenomenon of sagging occurs due to the load, which makes it difficult to use the shadow mask many times, and the formation of the pattern of the organic light emitting layer is defective.

A white organic light emitting device (hereinafter, referred to as a 'white organic light emitting device') of a tandem type is one of the various methods that have been proposed in place of such a shadow mask. Hereinafter, As follows.

The white organic light emitting device is formed by depositing each layer between an anode and a cathode without forming a mask when a light emitting diode is formed, and the organic layers including the organic light emitting layer are sequentially deposited in a vacuum state with different components. The white organic light emitting device includes different light emitting layers for emitting light of a plurality of colors between the anode and the cathode, and a charge generating layer is provided between each light emitting layer. Each light emitting layer has a basic structure, do.

Such a white organic light emitting device may emit light at different positions in the device, rather than emitting light using one material, but a plurality of light emitting layers including a light emitting material having different PL peaks (wavelengths) Lt; / RTI > For example, a stack including a fluorescent light-emitting layer and a stack including a phosphorescent light-emitting layer may be stacked to realize a white organic light-emitting device.

However, the stack structure known to date does not have sufficient efficiency as a white organic light emitting device, and there is a problem in that color characteristics are changed in long driving due to the difference in efficiency by color. In addition, there is a problem that a sufficient color reproduction rate can not be realized in the display.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a white organic light emitting device having a plurality of stack structures capable of increasing light emitting efficiency and lifetime of a light emitting layer and an organic light emitting display using the same.

The white organic light emitting device of the present invention includes a plurality of layers of a reflective electrode and a transparent electrode facing each other, a stack of a plurality of layers between the reflective electrode and the transparent electrode, and a charge generation layer between the stacks, At least one of the stacks of stacks includes first and second emission layers of different emission peaks.

In addition, the first and second light-emitting layer _{-0.36≤ (2n 1 d) / λ} 1 - (2n 2 d) / λ 2 ≤ 0.31 (n1 is the refractive index of the first light-emitting layer, n2 is the refractive index of the second light-emitting layer, λ ₁ is the luminescence peak wavelength of the first light emitting layer, luminescence peak wavelength of the second light emitting layer, and d is the distance from the reflective electrode to the interface between the first and second light emitting layers).

Here, the first light emitting layer may have an emission peak of 510 nm to 590 nm.

The first light emitting layer close to the reflective electrode preferably has an emission peak at a shorter wavelength than the second light emitting layer.

The first dopant content of the first light emitting layer may be greater than the second dopant content of the second light emitting layer.

The second light emitting layer may include a first host and a first dopant, and the first host may have a hole conductivity greater than an electron conductivity.

A stack adjacent to the stack having the first and second light emitting layers may have a single light emitting layer of a third light emitting layer having an emission peak different from that of the first and second stacks.

The third light emitting layer may have an emission peak of a shorter wavelength than the first and second light emitting layers.

And a second common layer in contact with the light emitting layer in each of the stacks, the first common layer being close to the transparent electrode, and the second common layer being in contact with the light emitting layer and being close to the reflective electrode.

Here, the first light emitting layer may be a yellow light emitting layer, the second light emitting layer may be a red light emitting layer, and the third light emitting layer may be a blue light emitting layer.

(λ는 각 스택의 중심 발광 피크, n^a과 d^a는 제 1 전극, 제 2 전극 중 투명 전극의 굴절률과 두께, n^w해당층의 굴절률,d^w는 각각 반사 전극의 안쪽 표면에서부터의 거리)의 조건을 만족할 수 있다.The layers up to the inner surface of the reflective electrode, including the transparent electrode,

(λ is a center of the emission peak of each stack, n ^a and d ^a is the first electrode, a second distance of refractive index, from the inside surface of the reflective electrode d ^w are each a transparent electrode refractive index and thickness, n ^w the layer of the electrode ) Can be satisfied.

According to another aspect of the present invention, there is provided an OLED display device including a substrate having a plurality of sub-pixels, a driving transistor provided on each sub-pixel and a driving transistor, And a plurality of stacked layers between the reflective electrode and the transparent electrode, and an organic light emitting diode including a charge generation layer between the stacks, wherein at least one of the stacks of the plurality of stacks includes (2n ₁ d) / λ _{1 -} (2n ₂ d) / λ ₂ ≦ 0.31 (n1 is an integer of 0 or ₁ ), and the first and second light emitting layers the refractive index of the first light-emitting layer, n2 is the refractive index, λ ₁ is the emission peak wavelength of the emission peak wavelength, the second light-emitting layer of the first light-emitting layer of the second light-emitting layer, d is the interface to the between the first and second light-emitting layer from the reflective electrode Street) Satisfied.

The organic light emitting device of the present invention and the organic light emitting display using the same have the following effects.

In the tandem-type organic light emitting device having a plurality of stacks, the position of the light emitting layer and the material of the light emitting layer can be selected so that the resonance period of each light emitting layer is maximized in a stack including a plurality of light emitting layers having adjacent light emitting peaks . Therefore, the efficiency of light of a specific color is not lowered, and excellent white light emission can be performed for a long time.

Further, in the provision of the adjacent luminescent layer, the main luminescent layer may be a yellow luminescent layer or a green luminescent layer, the luminescent layer adjacent to the luminescent layer may be a complementary luminescent layer as a red luminescent layer, The color reproducibility can be improved by adding an additional light emitting layer of a portion in which the relative color display is insufficient without affecting the light emitting function.

In addition, the auxiliary light emitting layer among the adjacent light emitting layers may functionally improve the color reproducibility and transport the holes supplied from the adjacent stacks as the main light emitting layer, thereby improving the hole transporting property.

1 is a block diagram schematically showing an organic light emitting diode display of the present invention
2 is a circuit diagram showing a circuit configuration for the sub-pixel of FIG.
3 is a sectional view showing a schematic structure of the sub-pixel of FIG.
4 is a cross-sectional view of a white organic light emitting device according to the present invention
5 is a cross-sectional view illustrating a white organic light emitting device according to a first embodiment of the present invention
6 is a cross-sectional view illustrating a white organic light emitting device according to a second embodiment of the present invention
7 is a cross-sectional view of a sub-pixel of the organic light-
8 is a graph showing light intensities according to wavelengths when the white organic light emitting display device of the embodiment of the present invention and the comparative example are applied.
Fig. 9 is an enlarged view of the light intensity according to the red wavelength of Fig. 8 compared with the comparative example and the embodiment of the present invention
10 is a band diagram of a white organic light emitting device according to an embodiment of the present invention.
11 is a graph showing the red lifespan of Examples and Comparative Examples of the present invention
12 is a graph showing the green lifespan of Examples and Comparative Examples of the present invention
13 is a graph showing the blue lifetime of the example of the present invention and the comparative example

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, when it is determined that a detailed description of a technique or configuration related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. The component names used in the following description are selected in consideration of easiness of specification, and may be different from the parts names of actual products.

The following description will first explain the basic structure of an organic light emitting diode display, and explain a white organic light emitting diode applied thereto.

1 is a block diagram schematically showing an organic light emitting diode display of the present invention.

1, the OLED display of the present invention includes an image processing unit 115, a data conversion unit 114, a timing control unit 113, a data driving unit 112, a gate driving unit 111, and a display panel .

The image processing unit 115 performs various image processing such as setting a gamma voltage to realize the maximum luminance according to the average image level using the RGB data signals RGB, and then outputs RGB data signals RGB. The image processor 115 generates a driving signal including at least one of the RGB data signal RGB as well as the vertical synchronizing signal Vsync, the horizontal synchronizing signal Hsync, the data enable signal DES and the clock signal CLK Output.

The timing controller 113 receives one or more of the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, the data enable signal DES and the clock signal CLK from the image processing unit 115 or the data conversion unit 114 And is supplied with a drive signal. The timing control section 113 generates a gate timing control signal GCS for controlling the operation timing of the gate driving section 111 and a data timing control signal DCS for controlling the operation timing of the gate driving section 112, .

The timing controller 113 outputs the data signal DATA corresponding to the gate timing control signal GCS and the data timing control signal DCS.

The data driver 112 samples and latches the data signal DATA supplied from the timing controller 113 in response to the data timing control signal DCS supplied from the timing controller 113 and converts the sampled data signal into a gamma reference voltage . The data driver 112 outputs the converted data signal DATA through the data lines DL1 to DLm. The data driver 1112 is formed in the form of an IC (Integrated Circuit).

The gate driving unit 111 outputs the gate signal while shifting the level of the gate voltage in response to the gate timing control signal GCS supplied from the timing control unit 113. [ The gate driver 111 outputs a gate signal through the gate lines GL1 to GLn. The gate driver 111 may be formed in the form of an IC or a gate-in-panel type in the display panel 150.

The display panel 110 includes a sub-pixel structure including a red sub-pixel SPr, a green sub-pixel SPg, and a blue sub-pixel SPb, for example. That is, one pixel P is composed of red, green, and blue sub-pixels. In some cases, it may further include a white sub-pixel WPg.

2 is a circuit diagram showing a circuit configuration for the sub-pixel of FIG.

As shown in FIG. 2, each sub-pixel has a basic structure of a 2T1C structure including a switching transistor, a driving transistor, a capacitor, and an organic light emitting diode, and further, a transistor and a capacitor may be additionally provided. This circuit configuration is provided between the gate line GL in the first direction and the data line DL and driving power supply line VDDL in the direction crossing the gate line GL in the first direction.

The organic light emitting display includes an organic light emitting diode that emits light to each individual sub-pixel, and may further include a compensation circuit CC for each individual sub-pixel to prevent deterioration thereof.

The switching transistor SW operates in response to the gate signal supplied through the gate line GL so that the data signal supplied through the data line DL is stored as a data voltage in the capacitor Cst.

The driving transistor DR operates so that a driving current flows between the driving power supply line VDDL and the ground line GND in accordance with the data voltage stored in the capacitor Cst.

The compensation circuit CC compensates the threshold voltage of the driving transistor DR and the like. The compensation circuit CC may be composed of one or more transistors and capacitors. Since the configuration of the compensation circuit CC can be variously configured, a detailed description thereof will be omitted.

The organic light emitting display having the above-described sub-pixel structure may be implemented by a top emission type, a bottom emission type, or a full-emission type, depending on a direction in which light is emitted.

3 is a cross-sectional view showing a schematic structure of the sub-pixel of FIG.

The organic light emitting display device of the present invention includes a white organic light emitting device WOLED that emits light in one direction among the light emitting modes and each sub pixel commonly emits white light and includes red, The color filters CFr, CFg, and CFb of the corresponding colors may be applied to each of the first and second color filters. As described above, the individual sub-pixel is provided with a circuit including a driving transistor (TFT), etc. for driving the organic light emitting diode.

When a white organic light emitting device that emits white light is commonly provided in each sub pixel of the present invention, an organic material of the organic light emitting device is deposited on each sub pixel to form an organic light emitting device, It is not necessary to use a metal mask for deposition, which makes it easy to increase the size. In addition, since the organic light emitting device has uniform characteristics without distinguishing the regions, a structure in which a light emitting layer of each color is applied by dividing each color sub-pixel including a specific dopant, There is an advantage that life can be improved and power consumption can be reduced.

Hereinafter, the white organic light emitting device of the present invention will be described. The white organic light emitting device of the present invention corresponds to the organic light emitting diode (OLED) of FIG. 2 and corresponds to the WOLED of FIG. 3 commonly provided for each sub-pixel.

4 is a cross-sectional view illustrating a white organic light emitting device of the present invention.

4, the white organic light emitting device of the present invention includes a transparent electrode 61 and a reflective electrode 62, which are opposed to each other in a basic structure, and a plurality of stacks 50 and 70 , 80, ... and a charge generation layer (91, 92) between the stacks (50, 60, 70).

The white organic light emitting device of the present invention includes a plurality of stacks between the transparent electrode 61 and the reflective electrode 62, and each stack has a different center emission peak.

At least one stack 70 of the stack is in contact with each other and includes first and second light emitting layers 72 and 73 having different emission peaks.

Here, the first and second light emitting layers 72 and 73 satisfy the condition of -0.36? (2n ₁ d) /? ₁ - (2n ₂ d) /? ₂ ? n ₁ is the refractive index of the first light-emitting layer, n ₂ is the refractive index, λ ₁ is the emission peak wavelength of the emission peak wavelength, the second light-emitting layer of the first light-emitting layer, d is a second light-emitting layer of the first, from the reflective electrode of the second light-emitting layer (72, 73).

One of the first light emitting layer 72 and the second light emitting layer 73 is a main light emitting layer for determining the light emitting property of the stack 70 and the light emitting layer having a long wavelength far from the reflective electrode 62 . ≪ / RTI > Therefore, when the first light emitting layer 72 is a yellow light emitting layer and the second light emitting layer 73 is a red light emitting layer as the auxiliary light emitting layer, the second light emitting layer 73, which is an auxiliary light emitting layer having a longer wavelength, As shown in FIG. That is, the first light emitting layer 72 and the second light emitting layer 73 are disposed above and below the drawing, respectively. However, this means a more preferable structure, and does not exclude the structure in which the main luminescent layer of the adjacent luminescent layer is provided on the side remote from the reflective electrode 62.

In the present invention, the first and second light emitting layers 72 and 73 having different emission peak characteristics are provided in one stack because the first light emitting layer 72 as the main light emitting layer has a peak emission in the range of 510 nm to 590 nm Green luminescent layer belonging to the main luminescent layer, the efficiency of the remaining colors is prevented from being lowered, and the luminescent layer of another luminescent peak other than the luminescent peak of the main luminescent layer is added to increase the color gamut.

The 2n /? Values of the respective first and second light emitting layers 72 and 73 are obtained through the refractive indexes and the wavelengths of the corresponding light emitting layers and are obtained by the difference between the first and second light emitting layers 72 and 73, (2n ₁ d) / λ ₁ - (2n ₂ d) / λ ₂ ', wherein the first and second light emitting layers are arranged in a predetermined range, The value obtained by multiplying the difference in 2n /? Value by the distance from the reflective electrode 62 to the interface of the first and second light emitting layers 72 and 73 is within a certain range, that is, in the range of -0.36 to 0.31 The white organic light emitting element can be determined between the reflective electrode 62 and the transparent electrode 61 in the region where the interface between the first and second light emitting layers 72 and 73 is located.

The reason why the relationship of the adjacent first and second light emitting layers 72 and 73 is specified in the white organic light emitting device of the present invention is that the positions of the adjacent first and second light emitting layers are different from each other in the light emitting layer And is intended to be set in accordance with the peak characteristics of the resonated light. That is, in the white organic light emitting device of the present invention, in the structure having two or more adjacent light emitting layers, the first light emitting layer 72, as the main light emitting layer, And the second light emitting layer 73 as the auxiliary light emitting layer can be set in a proportional relation to the first light emitting layer 72 of the first light emitting layer 72. [

On the other hand, as the main light emitting layer, it is preferable that the light emitting layer of the stack different from the first light emitting layer 72 has a position corresponding to the most efficient resonance characteristic in the stack, and has the following optical path conditions.

<Light path conditions>

Here, λ is the first stack 50 or the second stack 70, or the third emission peak wavelength of the stack (80), n ^a is the refractive index of the transparent electrode 61, d ^a is the thickness of the transparent electrode 61 and n ^w and d ^w are the refractive index and thickness of the layer positioned between the reflective electrode 62 and the transparent electrode 61, respectively.

In this case, the first light emitting layer 72, which is the main light emitting layer, in the stack including the light emitting layers 52 and 82 of the other stack having the single light emitting layer and the adjacent two light emitting layers, The following conditions are met directly for distance:

<Distance condition between the light emitting layer and the reflective electrode>

Here, m is an integer (positive integer), n is the refractive index of the light emitting layer, and d is the distance between the reflective electrode 62 and the light emitting region of the light emitting layer. This means that each luminescent layer has the maximum luminescence intensity at the corresponding distance. When the luminescent layer is designed under such conditions, each luminescent layer will have the maximum intensity at a viewing angle of 0 deg., And even if the viewing angle increases, Or the light intensity is reduced to a similar level, so that the degradation of the luminous efficiency has the same or similar level.

In this case, by controlling the thicknesses of the common layers 51, 53, 71, 74, 81 and 83, a single light emitting layer 52 corresponding to the light emitting peaks of the first stack 50 and the second stack 70 , 82 and the first light emitting layer 72 can be adjusted. On the other hand, in each of the stacks, the common layers 51, 71, and 81 located on the lower side with respect to the light emitting layer are the hole transporting layers, and the common layers 53, Lt; / RTI &gt;

(2n ₁ d) / λ ₁ - (2n ₂ d), which depends on the refractive index and the wavelength characteristics of the material of the adjacent first and second light emitting layers, as shown in Table 1, / lambda _2d ', and the white efficiency of the light emitting layer in this range is shown.

lambda 1 lambda 2 n (? 1) n (? 2) d (2n ₁ d) /? ₁ - (2n ₂ d) /? ₂ W Efficiency (%) Experiment 1 556 556 1.8 1.8 220 0.00 100 620 1.8 1.78 220 0.16 95 630 1.8 1.77 220 0.19 91 640 1.8 1.77 220 0.21 85 456 1.8 1.85 220 -0.36 79 Experiment 2 520 520 1.81 1.81 220 0.00 100 556 1.81 1.8 220 0.11 96 620 1.81 1.78 220 0.27 85 630 1.81 1.77 220 0.30 80 640 1.81 1.77 220 0.31 75 456 1.81 1.85 220 -0.25 71

Table 1 shows that the first light emitting layer 72 of the adjacent first and second light emitting layers 72 and 73 has a white efficiency of 71% or more. The first light emitting layer 72 has two sets of 520 nm and 556 nm (2n ₁ d) / λ ₁ - (2n ₂ d), wherein the first light emitting layer 72 is the same as the first light emitting layer 73, the wavelength range of the second light emitting layer 73 is from 456 nm to 630 nm, / [lambda] ₂ 'was calculated. For convenience, experiments were conducted by fixing the distance from the inner surface of the reflective electrode 62 to the interface between the first and second light emitting layers 72 and 73 at 220 nm. However, in the above experiment, the distance from the inner surface of the reflective electrode 62 to the interface between the first and second light-emitting layers 72 and 73 can be varied according to the above-described conditions in accordance with the wavelength and material of the light- But is not limited to a specific distance.

In the above stack structure, the first and second light emitting layers 72 and 73 are positioned adjacent to each other. When the first light emitting layer 72 is the main light emitting layer, the remaining second light emitting layer 73 serves as an auxiliary light emitting layer At this time, the dopant content included in the first light-emitting layer 72 and the second light-emitting layer 73 is separately designated for the main / auxiliary light emission. For example, the first light emitting layer 72 may include a dopant for the emission peak at a higher concentration, and the second light emitting layer 73 may include a lower dopant than the first light emitting layer 72. The content of the dopant included in any one of the light emitting layers 72 and 73 does not exceed 30% of the host in each light emitting layer. It is preferable that the dopant content of the second light emitting layer 73 is not more than 10% with respect to the internal host.

On the other hand, a structure not described in the white organic light emitting device of the present invention will be described.

A single third light emitting layer 52 and 82 may be formed on and under the stack including the first and second light emitting layers 72 and 73 adjacent to each other. Here, the emission peak of the first and second light emitting layers 72 and 73 is applied together with the emission peak of the third light emitting layers 52 and 82, And the emission peak of the third emission layer 52, 82 has an emission peak different from the emission peak of the stack including the first and second emission layers 72, 73. For example, when the first emission layer 72 has a yellow-green emission peak, the second emission layer 73 may have a red emission peak, and the third emission layers 52 and 82 may have a blue emission peak.

Between the stacks, charge generation layers 91 and 92 may be formed. The charge generation layers 91 and 92 function to inject electrons into the lower stack, and inject holes into the upper stack. Function. In some cases, the charge generation layers 91 and 92 may each be a single layer or may include an n-type charge generation layer and a p-type charge generation layer separately performing functions of electron injection and hole injection. The charge generation layer controls the balance of charge between adjacent stacks.

Hereinafter, an example in which the white organic light emitting device of the present invention is applied to the bottom emission type and the top emission type will be described.

In the stack having the adjacent light emitting layer described below, the first light emitting layer is the main light emitting layer and the second light emitting layer is the auxiliary light emitting layer. When the main light-emitting layer is taken as a light-emitting layer having a middle wavelength range of, for example, 510 nm to 590 nm, the light-emitting layer having a long wavelength is located farther from the reflective electrode regardless of the positions of the main light- In this case, the second light emitting layer which is the auxiliary light emitting layer is located far from the reflective electrode. According to these rules, the position of the first light emitting layer which is the main light emitting layer can be changed to the upper and lower portions.

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

5, the white organic light emitting device according to the first embodiment of the present invention is a bottom light emitting method. The white organic light emitting device according to the first embodiment of the present invention includes a transparent electrode 118, a first stack 210, A second stack 220 on the first charge generation layer 130, a second charge generation layer 140 on the second stack 220, A third stack 230 on the second charge generating layer 140 and a reflective electrode 128 on the third stack 230.

Here, the first and second charge generating layers 130 and 140 function to connect the respective stacks on the surfaces that function to inject electrons into adjacent lower and upper stacks and to supply holes.

Further, in the above-described first embodiment, the two adjacent first and second light emitting layers 223 and 222 of the second stack 220 are respectively a sulfur green light emitting layer and a red light emitting layer, And has a long wavelength light emitting layer.

Here, the first light emitting layer 223 may include at least one mixed host and at least one dopant as a yellow light emitting layer. Specifically, a phosphorescent host material made of a carbazole-based compound or a metal complex may be doped with a phosphorescent green green dopant. The carbazole-based compound may include CBP (4,4'-bis (carbazole-9-yl) -biphenyl), CBP derivative, mCP (N, N'-dicarbazolyl-3,5benzene) , The metal complex may include ZnPBO (phenyloxazole) metal complex or ZnPBT (phenylthiazole) metal complex, and the like. The emission peak corresponding to the first light emitting layer 223 is in the range of 510 nm to 590 nm, which corresponds to the sulfur green emission and sometimes shifts to the green emission to emit light.

The second light emitting layer 222 functioning as the auxiliary light emitting layer may replace the function of the hole transporting layer in some cases. In this case, the hole transport layer 211 may be omitted in the second stack 220. In some cases, as shown in the figure, the second light emitting layer 222 is positioned above the hole transport layer 211 and functions as a second hole transport layer, and may function as a function of emitting red light. For this, the second light emitting layer 222 includes at least one host and at least one dopant having the same or similar energy level as the hole transport layer 211 of the adjacent lower layer.

For reference, the light emitting material is divided into a host material and a guest material in terms of function. In general, it is difficult to control the purity of light emission at a specific wavelength band, although it is sometimes possible to emit light only for a host or a guest. However, it is difficult to control the purity of light emission by using a host / guest system in which the emission spectrum of the host matches the absorption spectrum of the guest. Can be increased.

The red host included in the second light emitting layer 222 has a bipolar property, and a hole transporting host having a strong hole characteristic is used. For example, the red host has a Lowest Unoccupied Molecular Orbital (LUMO) energy level of -1.0 to -3.0 eV and a HOMO (Highest Occupied Molecular Orbital) energy level of -4.9 eV to -6.0 eV.

Since the second light emitting layer 222 is located between the first charge generating layer 150 and the first light emitting layer 223, electrons leaked from the first light emitting layer 223 as a main light emitting layer are trapped to contribute to red light emission Thereby increasing the red color efficiency and contributing to the improvement of the color recall ratio and the luminance of the device. Here, the wavelength range of the second light emitting layer 222 has a wavelength range of 600 nm to 650 nm.

The host material used for the second light emitting layer 222 may be a host material in which the aryl group is a core and the aryl group is a substituted or unsubstituted aryl group having 6 to 24 carbon atoms or a substituted or unsubstituted heteroaryl group, A substituted or unsubstituted heteroaryl group having 2 to 24 carbon atoms, a substituted or unsubstituted alkyl group having 1 to 24 carbon atoms, a substituted or unsubstituted heteroalkyl group having 1 to 24 carbon atoms, a substituted or unsubstituted A substituted or unsubstituted alkyl group having 1 to 24 carbon atoms, a cycloalkyl group having 3 to 24 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 24 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 24 carbon atoms, a substituted or unsubstituted alkylsilyl group having 1 to 24 carbon atoms, Or an unsubstituted arylsilyl group having 6 to 24 carbon atoms, a cyano group, a halogen group, deuterium, and hydrogen, and R to R14 may be selected from the group consisting of Ring can be formed.

The constituent of the core is an aryl group and is preferably an aryl group selected from phenyl, naphthalene, fluorene, carbazole, phenazine, phenanthroline, phenanthridine, acridine, Pyridine, pyrazine, pyridine, pyrazole, imidazole, pyrrolyl, pyrrolidine, pyrazine, quinoline, indole, indazole, pyridazine, pyrazine, pyrimidine, pyridine, pyrazole, imidazole and pyrroly.

Examples of the host material of the second light emitting layer 222 include CBP, CDBP, mCP, BCP, BAlq, and TAZ. One or more of these materials may be included.

The phosphorescent dopant may be Ir (piz) 3 (Tris (1-phenylisoquinoline) iridium (III), Ir (piq) Ir (bip) 2 (acac) (Bis) 2-benzolbithiophen-2-yl-pyridime (acetylacetonate) iridium (III), Ir (BT) 2 acetic acid (Bis (2-pheylbenzothazolato) (accetylacetonate) iridium (III), and the like.

Examples of the fluorescent dopant that can be included in the second light emitting layer 222 include rubrene (5,6,11,12-tetraphenylnaphthacene), DCJTB (4- (dicyanlmethylene) -2-tert- , 7,7, -tetramethyljuloidin-4-yl-viyl) -4H), and the like.

The first light emitting layer 223 may include a yellow or green dopant at a concentration of 30% or less as a main light emitting layer, and the second light emitting layer 222 may include red light at a concentration of 10% Dopants.

Meanwhile, although the second light emitting layer 222 has been described as an example of a red light emitting layer, a different substituent may be added. The material described above is known, but is not limited thereto. If the material is developed, it may be changed to another red light emitting material if it functions as the above-described auxiliary light emitting layer and functions as red light emitting and hole transporting.

The third light emitting layers 211 and 232 of the first stack 210 and the third stack 230 are blue light emitting layers. Such a blue light emitting layer emits light having a wavelength in the range of 440 nm to 480 nm, and can be selected from fluorescent or phosphorescent materials.

The material of the blue light emitting layer may include at least one host and at least one dopant. Specifically, at least one fluorescent host material selected from the group consisting of an anthracene derivative, a pyrene derivative, and a perylene derivative may be doped with a fluorescent blue dopant. If there is development of a stable phosphorescent blue material, substitution will be possible.

The first charge generation layer 150 and the second charge generation layer 160 that connect the respective stacks include n-type charge generation layers 151 and 161 and p-type charge generation layers 152 and 162, respectively .

Commonly, each stack includes hole transporting layers 211, 221, and 231 and electron transporting layers 223, 224, and 233 on the lower and upper portions of the light emitting layer. However, these layers are not necessarily provided, And may be omitted in the layered structure. In this case, each luminescent layer may contact the electrode in the stack or directly contact the charge generating layer.

In addition, although the transparent electrode 118 is directly disposed on the substrate 101 in the drawing, when the white organic light emitting device is implemented as an OLED display device, each sub-pixel includes a driving transistor, The transparent electrode 118 may be positioned in a form connected to the thin film transistor and the transparent electrode 118 may be patterned to be divided into sub pixels and the transparent electrode 370 on the upper side may be an active region including a plurality of sub- As shown in FIG.

The transparent electrode located on the lower side of the white organic light emitting device according to the first embodiment may be a transparent oxide film such as a Tin Oxide, Indium Tin Oxide, Zinc Oxide, Indium Zinc Oxide, Indium Gallium Zinc Oxide, In some cases, a reflective electrode and a different kind of metal may be stacked in a double layer or more. In this case, the transparent electrode 118 functions as an anode, and the reflective electrode 128 functions as a cathode.

In addition, in the first embodiment of the present invention, in addition to the three stacks shown in the drawing, a single light emitting layer is additionally provided on the third stack 230 or the lower portion of the first stack 210, respectively, and the electron transporting layer and the hole transporting layer In this case, the light emitting layer of the additional stack may have a wavelength different from that of the first to third light emitting layers, or may include a light emitting layer having the same wavelength as any one of the first to third light emitting layers . &Lt; / RTI &gt; Further, the structure of the light emitting layer adjacent to the added stack may be provided. For the maximum resonance characteristic of each luminescent layer, a specific relationship between the above-mentioned optical path conditions or adjacent luminescent layers can be satisfied. In some cases, in the case of an organic light-emitting device that emits light with a deflection of blue or a different color instead of white, a combination of light-emitting layers of the corresponding color is selected accordingly.

6 is a cross-sectional view illustrating a white organic light emitting device according to a second embodiment of the present invention.

The white organic light emitting device according to the second embodiment of the present invention according to the present invention shown in FIG. 6 has a transparent electrode 370 at the upper side and a lower edge of the reflective electrode 310 at a position adjacent to the substrate 101 The remaining structure is the same as that of the first embodiment.

In addition, in the second embodiment, a transparent auxiliary electrode 311 may be additionally provided in addition to the reflective electrode 310.

The white organic light emitting device according to the second embodiment of the present invention is a top organic light emitting device according to a top emission method and includes a reflective electrode 310, a transparent auxiliary electrode 311, a first stack A second stack 330 on the first charge generation layer 350; a second charge generation layer 360 on the second stack 330; A third stack 340 on the second charge generation layer 360, and a reflective electrode 370 on the third stack 340.

Here, the first and second charge generating layers 350 and 360 function to connect the respective stacks in a plane that injects electrons into adjacent lower and upper stacks and supplies holes, respectively.

In the above-described second embodiment, the two adjacent first and second light emitting layers 332 and 323 of the second stack 330 are respectively a yellow and green light emitting layer and a red A light emitting layer having a longer wavelength is provided.

The third light emitting layers 322 and 342 of the first stack 320 and the third stack 340 are blue light emitting layers.

Each of the first charge generating layer 350 and the second charge generating layer 360 connecting the respective stacks may be a single layer or may include an n-type charge generating layer and a p-type charge generating layer.

Commonly, each stack includes hole transporting layers 321, 331, and 341 and electron transporting layers 323, 334, and 343 on the lower and upper portions of the light emitting layer. These layers are not necessarily provided, And may be omitted in the layered structure. In this case, each luminescent layer may contact the electrode in the stack or directly contact the charge generating layer.

Although the reflective electrode 310 is directly disposed on the substrate 101 in the drawing, when the organic light emitting display device is implemented as an OLED display device, each sub-pixel includes a driving transistor, The reflective electrode 310 may be positioned in a form connected to the thin film transistor. The reflective electrode 310 may be patterned to be divided into sub-pixels. The transparent electrode 370 may include an active region including a plurality of sub- As shown in FIG.

Materials and wavelength characteristics of the respective light emitting layers are the same as those of the first embodiment described above, and a description of the same description is omitted.

Meanwhile, the form of the white organic light emitting device of the present invention when used in an organic light emitting display device will be described.

7 is a cross-sectional view of a sub-pixel of the organic light emitting diode display according to the present invention.

Although the organic light emitting display of FIG. 7 is shown as a back light emitting method in which light is emitted toward the substrate on which the sub-pixels are arranged, the present invention is not limited thereto. That is, the present invention is also applicable to a top emission organic light emitting display in which light is emitted in a direction opposite to that of a substrate on which sub-pixels are arranged.

7 shows an organic light emitting display device using a thin film transistor having a coplanar structure as an example, but the present invention is not limited thereto. A thin film transistor having a staggered structure is also applicable.

As shown in FIG. 7, the organic light emitting diode display of the present invention may include a transistor (TFT), a white organic light emitting diode (WOLED), and a color filter (CF) formed on a substrate 101 in one sub pixel.

First, a driving transistor including a transistor (TFT) includes a semiconductor layer 124, a gate electrode 121, a source electrode 122, and a drain electrode 123.

The semiconductor layer 124 is formed on the substrate 101 made of an insulating material such as a transparent plastic or a polymer film.

The semiconductor layer 124 may be formed of an amorphous silicon film, a polycrystalline silicon film crystallized from amorphous silicon, an oxide semiconductor, an organic semiconductor, or the like.

At this time, a buffer layer is further formed between the substrate 101 and the semiconductor layer 124 to protect the transistor (TFT) formed in the subsequent process from impurities such as alkali ions flowing out from the substrate 101.

On the semiconductor layer 124, a gate insulating film 115a made of a silicon nitride film, a silicon oxynitride film or the like is formed. A gate line including the gate electrode 121 and a first sustain electrode are formed thereon.

The gate electrode 121 and the gate line and the first sustain electrode are formed of a first metal material having a low resistance property such as a single layer made of aluminum, copper, molybdenum, chromium, gold, titanium, nickel, neodymium, Layer or multiple layers.

An interlayer insulating film 115 made of a silicon nitride film, a silicon oxide film, or the like is formed on the gate electrode 121, the gate line, and the first sustain electrode. A data line, a driving voltage line, and source / drain electrodes 122 and 123 and a second sustain electrode (not shown) are formed thereon.

The source electrode 122 and the drain electrode 123 are spaced apart from each other by a predetermined distance and are electrically connected to the semiconductor layer 124. More specifically, the gate insulating film 115a and the interlayer insulating film 115b are provided with a semiconductor layer contact hole exposing the semiconductor layer 124. Source / drain electrodes 122 and 123 are formed through the semiconductor layer contact holes And is electrically connected to the semiconductor layer 124.

At this time, the second sustain electrode overlaps a part of the first sustain electrode below the interlayer insulating film 115b to form a storage capacitor.

The data line, the driving voltage line, the source / drain electrodes 122 and 123 and the second sustain electrode are formed of a second metal material having a low resistance property such as aluminum, copper, molybdenum, chrome, gold, titanium, Or a single layer or multiple layers of alloys thereof.

A protective layer 115c is formed on the substrate 101 on which the data lines, the driving voltage lines, the source / drain electrodes 122 and 123, and the second sustain electrodes are formed.

A color filter is formed on the protective film 115c. The color filter is a color conversion material for converting white light emitted from a white organic light emitting diode into red, green and blue.

An overcoat layer 115d covering the color filter CF and exposing a part of the drain electrode 123 is formed on the protective film 115c. The overtot layer 115d may be formed of an organic material, but may be formed of an inorganic material or a mixture of organic and inorganic materials.

Then, a white organic light emitting device similar to the above-described embodiment can be formed.

The white organic light emitting device is electrically composed of a first electrode, a light emitting portion, and a second electrode. The patterned transparent electrode or reflective electrode of FIGS. 5 and 6 functions as a first electrode, Is a reflective electrode or a transparent electrode formed across the plurality of sub-pixels. And, the light emitting portion in between can correspond to the above-mentioned plural stacks.

In the following experiments, the white light emitting device of the present invention is applied to an organic light emitting diode, and the light intensity and lifetime of the organic light emitting display device are examined.

In an embodiment of the present invention, a single light emitting layer of a blue light emitting layer is used for the first stack and a red light emitting layer and a sulfur green light emitting layer are used for the second stack. And a single luminescent layer of a blue luminescent layer is used for the third stack.

In the comparative example, the first and third stacks are used in the same manner as the embodiment, and a single yellow-green light-emitting layer is used in the second stack.

FIG. 8 is a graph showing light intensities according to wavelengths when the organic light emitting display device of the embodiment of the present invention and the comparative example are applied. FIG. 9 is a graph comparing light intensities according to the red wavelengths of FIG. 8 with those of the comparative example and the present invention It is an enlarged view.

As shown in FIGS. 8 and 9, when the organic light emitting diode display according to the embodiment of the present invention is implemented, the light emission intensity having a peak characteristic in a red region band can be obtained.

The evaluation of the color reproducibility of these comparative examples and examples will be described with reference to Table 2.

division Color recall rate _DCI
(Digital Cinema Initiative) Comparative Example (B / YG / B) 95% Example (B / R + YG / B) 98%

For reference, the color gamut (or color gamut) refers to the range of colors that an input and output device can reproduce, depending on how the color space is defined.

The color reproduction rate in the above table is the satisfaction of the color gamut which can be expressed by digital cinema (Digital Cinema Initiatives), and expansion of the DCI overlap ratio means that the TV can provide a clearer image quality in a large-sized TV. It can be seen from Table 2 that the DCI superposition ratio is wider when the embodiment of the present invention is applied, and the color reproducibility is higher than that of the comparative example.

10 is a band diagram of a white organic light emitting device according to an embodiment of the present invention.

FIG. 10 is a graph showing the relationship between the hole mobility and the hole mobility of a host in the white organic light emitting device of the present invention, in which one host 1 dopant is used for the red light emitting layer among two light emitting layers adjacent to each other, Material is used.

In this case, the red light emitting layer not only helps the host of the hole transporting property to overflow from the adjacent charge generation layer, but also transports the holes to the main light emitting layer and also contributes to the red light emission as well as the light emission of the yellow green light emitting layer. That is, the red light emitting layer improves the color reproducibility and improves the hole transporting property to improve the hole / electron coupling ability in the sulfur green light emitting layer, thereby improving the internal light emitting efficiency of the sulfur green light emitting layer itself.

FIG. 11 is a graph showing the red lifespan of Examples and Comparative Examples of the present invention, FIG. 12 is a graph showing the green lifespan of Examples and Comparative Examples of the present invention, and FIG. 13 is a graph showing the blue lifespan of Examples and Comparative Examples of the present invention Fig.

Especially when the embodiment of the present invention is applied, it can be seen that the lifetime of the red light emission is remarkably improved as compared with the comparative example, particularly as shown in FIG. Numerically, it was confirmed that the lifespan of the red color was improved by 140%, the life of the green color was improved to 101%, and the lifespan of the blue color was substantially the same level when the present invention was applied.

That is, when the embodiment of the present invention is applied, it is expected that a remarkable improvement in the color gamut of red color and an improvement in the lifetime can be expected, which means that display can be made to meet the demands of the viewer than in an organic light emitting display .

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Will be apparent to those of ordinary skill in the art.

50: first stack 61: transparent electrode
62: reflective electrode 70: second stack
80: Third stack 72: First light emitting layer
73: second light emitting layer 52, 82: third light emitting layer

Claims (11)

A reflective electrode and a transparent electrode facing each other; And
An organic light emitting device including a stack of a plurality of layers between the reflective electrode and the transparent electrode, and a charge generation layer between the stacks,
Wherein at least one stack of the stacks of the plurality of layers includes first and second light emitting layers of different emission peaks,
The first and second light-emitting layer _{-0.36≤ (2n 1 d) / λ} 1 - (2n 2 d) / λ 2 ≤ 0.31 (n 1 is the refractive index, n ₂ is the refractive index of the second light-emitting layer of the first light-emitting layer, λ ₁ is a light emission peak wavelength of the first light emitting layer, a light emitting peak wavelength of the second light emitting layer, and d is a distance from the reflective electrode to an interface between the first and second light emitting layers). The method according to claim 1,
Wherein the first light emitting layer has an emission peak of 510 nm to 590 nm. 3. The method of claim 2,
Wherein the first light emitting layer close to the reflective electrode has an emission peak at a shorter wavelength than the second light emitting layer. The method of claim 3,
Wherein the first dopant content of the first light emitting layer is greater than the second dopant content of the second light emitting layer. The method of claim 3,
Wherein the second light emitting layer includes a first host and a first dopant, and the first host has a hole conductivity higher than the electron conductivity. 5. The method of claim 4,
Wherein a single light emitting layer of the third light emitting layer having the same emission peak as that of the first and second stacks is provided in the upper and lower stacks adjacent to the stack having the first and second light emitting layers. The method according to claim 6,
Wherein the third light emitting layer has an emission peak at a shorter wavelength than the first and second light emitting layers. The method according to claim 1,
A first common layer in contact with the respective light emitting layers in the stack, the first common layer being close to the transparent electrode, and the second common layer being in contact with the light emitting layer and being close to the reflective electrode. 8. The method of claim 7,
The first light emitting layer is a yellow light emitting layer,
The second light emitting layer is a red light emitting layer,
And the third light emitting layer is a blue light emitting layer. The method according to claim 1,
The layers up to the inner surface of the reflective electrode, including the transparent electrode,

(λ is a center of the emission peak of each stack, n ^a and d ^a is the first electrode, a second distance of refractive index, from the inside surface of the reflective electrode d ^w are each a transparent electrode refractive index and thickness, n ^w the layer of the electrode ). &Lt; / RTI &gt; A substrate having a plurality of sub-pixels;
A driving transistor provided in each sub-pixel on the substrate; And
An organic light emitting diode (OLED) display including a plurality of layers stacked between the reflective electrode and the transparent electrode, and an organic light emitting diode including a charge generation layer between the stacks, In the apparatus,
Wherein at least one stack of the stacks of the plurality of layers includes first and second light emitting layers of different emission peaks,
The first and second light-emitting layer _{-0.36≤ (2n 1 d) / λ} 1 - (2n 2 d) / λ 2 ≤ 0.31 (n1 is the refractive index of the first light-emitting layer, n2 is the refractive index of the second light-emitting layer, λ ₁ is The emission peak wavelength of the first light emitting layer, the light emitting peak wavelength of the second light emitting layer, and d is the distance from the reflective electrode to the interface between the first and second light emitting layers).

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