KR101908510B1 - White Organic Emitting Device and Display Device Using the Same - Google Patents

Abstract

The present invention relates to a white display device capable of white display with high color reproducibility by applying a two peak emission characteristic of a phosphorescent dopant in a two stack structure and a display device using the white display device. A blue light emitting unit adjacent to the first electrode and having a first emission peak at 430 nm to 480 nm; and a second electrode adjacent to the second electrode, one A phosphorescent light-emitting unit having a second emission peak and a third emission peak that differ from each other at 530 nm to 630 nm via a phosphorescent dopant; And an intermediate layer between the blue light emitting unit and the phosphorescent light emitting unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a white organic light emitting device and a display device using the white organic light emitting device.

The present invention relates to an organic light emitting device, and more particularly, to a tandem white organic light emitting device having a two stack structure for white display, a phosphorescent dopant which emits two emission peaks with one dopant in a phosphorescent light emitting layer, Efficiency and color reproducibility, and a display device 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 device is considered as a competitive application for not requiring a separate light source, compacting the device, and displaying clear color images.

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.

As one of the various methods for replacing such a shadow mask, there is a white organic light emitting display.

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

The white organic light emitting display device is characterized in that when forming a light emitting diode, each layer between an anode and a cathode is vapor-deposited without a mask, and organic layers including an organic light emitting layer are sequentially deposited in a vacuum state with different components.

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

On the other hand, in general, the spectrum applied to a general white organic light emitting display device has three peaks or more to cause peaks in the RGB region for color implementation. This is to facilitate the RGB color implementation after the light transmitted through the light emitting layer passes through the color filter layer.

In order to reduce the number of layers and reduce the number of processes as a structure of a white organic light emitting display device, two tandem structures in which a blue light emitting unit and a phosphorescent light emitting unit having a longer wavelength are laminated are well known.

In such a two-tandem structure, two different emission peaks are generated in different units. In particular, it is difficult to reproducibly secure the light intensity of the corresponding peak of red and green corresponding to the phosphorescent light-emitting unit.

SUMMARY OF THE INVENTION The present invention has been devised to solve the problems described above, and it is an object of the present invention to provide a white display device capable of displaying a white color with a high color reproduction rate by applying a two peak emission characteristic of a phosphorescent dopant in a two- It has its purpose.

According to an aspect of the present invention, there is provided a white organic light emitting device including: a first electrode and a second electrode opposing each other on a substrate; a first electrode having a first emission peak at 430 nm to 480 nm adjacent to the first electrode; A phosphorescent light emitting unit adjacent to the second electrode and having a second emission peak and a third emission peak that differ from each other at 530 nm to 630 nm via one phosphorescent dopant in one host; And an intermediate layer between the blue light emitting unit and the phosphorescent light emitting unit.

Here, it may be preferable that the second emission peak having a relatively small wavelength has a higher emission intensity than the third emission peak. In this case, the difference between the wavelengths representing the second emission peak and the third emission peak may be preferably 20 nm to 59 nm. More preferably, the panel efficiency and the color reproduction rate are improved when the difference between the second and third emission peaks is about 40 nm to 59 nm.

The efficiency of the third emission peak wavelength region in the phosphorescent dopant is preferably 17% to 38% of the efficiency of the second emission peak wavelength region.

The inventors of the present invention have found from experiments that the efficiency of the phosphorescent second luminescence peak wavelength region has an external quantum efficiency of 16.0% to 19.5% and the efficiency of the third luminescence peak wavelength region has an external quantum efficiency of 3.5% to 6.0% , It was confirmed that the panel efficiency was improved compared with the structure having two peaks of the two stack structure (in the case where the phosphorescent dopant used in the phosphorescent light emitting unit is a dopant having one peak characteristic). Also, the second emission peak may be from 548 nm to 554 nm, and the third emission peak may be from 600 nm to 608 nm.

(λ는 청색 발광 유닛 또는 인광 발광 유닛의 발광 피크 파장, n^a과 d^a는 제 1 전극의 굴절률과 두께, n^w와 d^w는 각각 제 1 전극과 제 2 전극 사이에 위치하는 해당층의 굴절률과 두께)의 광경로 조건을 만족한다. On the other hand, the total thickness from the first electrode to the second electrode immediately before the second electrode including the first electrode is 5000 ANGSTROM to 6000 ANGSTROM,

(lambda represents the luminescence peak wavelength of the blue light emitting unit or the phosphorescence emitting unit, n ^a and d ^a is the refractive index and thickness of the first electrode, and n ^w and d ^w satisfy the optical path conditions of the refractive index and thickness of the corresponding layer located between the first electrode and the second electrode, respectively).

The blue light emitting unit and the phosphorescent emitting unit may each include a light emitting layer, an electron transporting layer and a hole transporting layer above and below the light emitting layer.

According to another aspect of the present invention, there is provided a display device including a substrate on which a cell driver including a thin film transistor is formed, a color filter layer on the substrate, a first electrode connected to the thin film transistor, A blue light emitting unit having a first emission peak at 430 to 480 nm adjacent to one electrode and a second emission peak at 530 nm to 630 nm which are different from each other on the blue light emitting unit through one phosphorescent dopant to one host, A phosphorescent light-emitting unit having a third emission peak; And a second electrode on the phosphorescent-emitting unit.

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

In a white organic light emitting device having a two-stack tandem structure, a phosphorescent light emission is realized. By forming a phosphorescent light emitting layer using one kind of dopant capable of two-color peak emission, the color reproducibility can be improved with a minimum stacking structure.

In particular, it is easy to apply the layer suitable for calculating the optimal cavity number and the process number reduction compared to the three-stack structure, and the doping amount adjustment of the conventional phosphorescent light emitting layer using two phosphorescent dopants, red dopant and green dopant, It is possible to eliminate the use of a hard red dopant and to prevent unevenness in stain caused thereby.

In addition, when using a dopant capable of emitting one peak in the two-stack structure, it is possible to simultaneously improve the panel efficiency and improve the color reproduction rate by suitably giving a difference in the peak emission wavelength of the two-color contrast.

1 is a cross-sectional view of a white organic light emitting device according to the present invention
Fig. 2 is a graph showing the light intensity of each wavelength in Fig. 1
3 is a view showing a panel unevenness which is generated when two dopants are applied to the phosphorescent light emitting unit
4 is a schematic cross-sectional view of a display device to which the white organic light emitting device of the present invention is applied
5 is a circuit diagram showing one pixel of the display device of the present invention.
6 is a vertical sectional view showing R, G, B and W pixels of the display device of the present invention
FIG. 7A is a graph showing the results of the white organic light emitting device of the present invention shown in Table 1,
7B is a graph showing the color reproduction ratio of the white organic light emitting device of the present invention as compared to ATSC
8 is a graph showing the light emission intensities according to the second and third luminescence peak wavelength differences of the white organic light emitting device of the present invention

Hereinafter, a white organic light emitting device and a display device using the same according to the present invention will be described in detail with reference to the accompanying drawings.

The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, this embodiment is provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art. In this figure, the sizes and relative sizes of the layers and regions may be exaggerated for clarity.

FIG. 1 is a cross-sectional view illustrating a white organic light emitting device according to the present invention, and FIG. 2 is a graph illustrating light intensities of respective wavelengths in FIG.

1 and 2, a white organic light emitting diode 1000 according to the present invention includes a first electrode 110 and a second electrode 150 opposed to each other on a substrate 100, A blue light emitting unit 120 having a first emission peak at 430 to 480 nm adjacent to the first electrode 150 and a blue light emission unit 120 adjacent to the second electrode 150, A phosphorescent light-emitting unit 140 having two emission peaks and a third emission peak, and an intermediate layer 130 between the blue light-emitting unit and the phosphorescent light-emitting unit.

Particularly, the blue light emitting unit 120 and the phosphorescent light emitting unit 140 ultimately realize white display by the mixed light of the respective light emission between the first and second electrodes 110 and 150, The white organic light emitting device can realize three peaks even in the two stack structure, and the color reproduction rate becomes high in all color display.

Here, a second emission peak (approximately yellowish green region wavelength - hereinafter referred to as YG wavelength) of a relatively short wavelength among the second and third emission peaks is a third emission peak (hereinafter, referred to as a reddish orange region wavelength-- -). Since the intensity of the second emission peak is relatively strong, the phosphorescent light emitting unit 140 is also referred to as a YG unit.

In this case, the difference between the wavelengths representing the second emission peak and the third emission peak may be preferably 20 nm to 59 nm. More preferably, the panel efficiency and the color reproduction rate are improved when the difference between the second and third emission peaks is about 40 nm to 59 nm.

The efficiency of the third emission peak wavelength region in the phosphorescent dopant is preferably 17% to 38% of the efficiency of the second emission peak wavelength region. When the absolute value of the external quantum efficiency is compared, the efficiency of the phosphorescence second peak wavelength region is 16.0% to 19.5% and the efficiency of the third peak peak wavelength region is 3.5% to 6.0% It is desirable to have an external quantum efficiency of.

The inventors of the present invention have found from experiments that the efficiency of the phosphorescent second luminescence peak wavelength region has an external quantum efficiency of 16.0% to 19.5% and the efficiency of the third luminescence peak wavelength region has an external quantum efficiency of 3.5% to 6.0% , It was confirmed that the panel efficiency was improved compared with the structure having two peaks of the two stack structure (in the case where the phosphorescent dopant used in the phosphorescent light emitting unit is a dopant having one peak characteristic). In this case, the second emission peak may be in the range of 548 nm to 554 nm (A region), and the third emission peak may be in the range of 600 nm to 608 nm (B region). However, this is confirmed in the experimental examples, and it is not limited to this, and it is possible to expand the range of the wavelength difference between the second emission peak and the third emission peak to 20 nm to 59 nm.

The phosphorescent dopant is an iridium complex having external quantum efficiency of 16.0% to 19.5% at the wavelength of the A region and external quantum efficiency of 3.5% to 6.0% at the wavelength of the B region . In this case, the blue external quantum efficiency EQE in the blue light emitting unit 120 is about 8% to 11%.

In brief, the material of the phosphorescent dopant applied to the phosphorescent light-emitting unit 140 of the present invention will be described. As shown in Chemical Formula 1, the central metal is iridium (Ir) (III), and ligands A to C are substituted around the phosphorescent dopant.

Depending on the chemical structure of the material forming the ligands A to C, spectral characteristics of absorption or luminescence may appear differently. That is, the spectrum can be designed differently depending on the distribution of electrons between iridium and ligands A to C. The phosphorescent dopant of the present invention is designed such that the spectrum has two different wavelengths at a wavelength of 530 nm to 630 nm.

The ligands A to C may be the same or different. The ligand A to C chemistry is a compound having a carbon number of 8 to 40 aromatic rings having C, N, S, It can be selected from compounds having a ring (Heterocyclic Ring).

3, the blue light emitting unit 120 and the phosphorescent light emitting unit 140 include the light emitting layers 126 and 144, the upper and lower electron transporting layers 146 and 128, and the hole transporting layers 142 and 124, respectively can do.

(λ는 청색 발광 유닛 또는 인광 발광 유닛의 발광 피크 파장, n^a과 d^a는 제 1 전극의 굴절률과 두께, n^w와 d^w는 각각 제 1 전극과 제 2 전극 사이에 위치하는 해당층의 굴절률과 두께)의 광경로 조건을 만족한다. The total thickness of the first electrode 110 from the first electrode 110 to the second electrode 150 is 5000 ANGSTROM to 6000 ANGSTROM and the layers including the first electrode 110 to the second electrode 150

(lambda represents the luminescence peak wavelength of the blue light emitting unit or the phosphorescence emitting unit, n ^a and d ^a is the refractive index and thickness of the first electrode, and n ^w and d ^w satisfy the optical path conditions of the refractive index and thickness of the corresponding layer located between the first electrode and the second electrode, respectively).

Here, λ is a blue light emitting unit 120 or the emission peak wavelength, n ^a of the phosphorescent light-emitting unit 140 is the refractive index, the first electrode (110), d ^a is the thickness, n ^w of the first electrode (110), d ^{and w} are the refractive index and thickness of the layer positioned between the first electrode 110 and the second electrode 150, respectively.

The light path condition must be satisfied for the emission peak wavelength of the blue fluorescence unit and the phosphorescence emitting unit respectively for the final white implementation. For example, when the blue light emitting unit 120 has a peak wavelength of 456 nm for blue light emission and the phosphorescent light emitting unit 140 is a dual peak emission of 551 nm and 604 nm -, and sub emission peak - redish orange -), the above conditions must be met for each of these wavelengths.

The first light emitting layer (see 126 in FIG. 3) and the second light emitting layer 144 of the phosphorescent light emitting unit 140 in the blue light emitting unit 120 are each directly under the following conditions for a distance from the second electrode 150: .

<Distance condition between the light emitting layer and the second 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 second electrode 150 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, depending on the emission peak of each of the blue light emitting unit 120 and the phosphorescent light emitting unit 140, by controlling the thickness of the charge generating layer 130 or the common layer (hole transporting layer or electron transporting layer) in each light emitting unit, The position of the corresponding light emitting layer in the light emitting unit may be adjusted.

A two-stacked tandem white organic light-emitting device including a phosphorescent dopant that implements the above two peaks in a phosphorescent light-emitting layer has been developed according to the following needs.

FIG. 3 is a view showing a panel unevenness which is generated when two dopants are applied to the phosphorescent light emitting unit. FIG.

In recent years, the color reproduction rate of a white organic light emitting device is about 105 to 109% of that of an Advanced Television System Committee (ATSC) standard. However, since a white organic light emitting device has a higher color reproduction capability through a higher color reproduction rate, It is important to have competitiveness that satisfies

In order to achieve this, a white organic light emitting device having a tandem structure has been required to emit three peaks in order to exhibit colors in the natural world. However, in order to realize this, in the case of providing three light emitting layers for each peak, There is a problem that it is difficult to calculate the position and the thickness in order to have a proper cavity for each light emitting layer as the layer increases.

As another embodiment of the three-peak emission, there is an example in which a heterophasic phosphorescent dopant having different color luminescent characteristics is included in one layer, but the phosphorescent dopant of different kind may not function properly when mixed, The dopant of the red series has a problem that it is difficult to control the dopant so as to cause stains on the panel, and thus it is not suitable for practical display devices. That is, when two kinds of phosphorescent dopants are applied to one light emitting layer, the first phosphorescent dopant acts as a host of the second phosphorescent dopant, and when the amount of the first phosphorescent dopant is about 10%, the second phosphorescent dopant 1% or less, it is possible to obtain an efficiency suitable for panel operation when 1 host 2 dopant structure is applied. In this case, a very small amount of doping is required for the second dopant. This small amount of doping adjustment is very difficult, so that the color uniformity of the panel is changed by a slight amount of doping amount. FIG. 3 shows that the color uniformity characteristic of the panel is deteriorated due to the irregular doping amount of the dopant in actual panel fabrication. In the drawing, two panels are formed on one ledge glass. Two panels are formed around a bisected line on a vertical line. In this case, as the two panels are apart from each other, u'v It can be seen that the value of? U'v corresponding to the distance between the two colors on the coordinate system becomes larger. This means that as the distance from the center line of the glazing glass is increased, the spots in the panel become more severe. As the doping amount control of the second dopant (red dopant), which requires very small doping, fails, such smear tends to be more severe.

In order to solve this problem, the white organic light emitting device of the present invention is designed so that the peak emission of two colors can be expressed by one phosphorescent dopant in the phosphorescent light emitting layer, thereby eliminating the burden on the process, facilitating the cavity design, It is possible to prevent the generation of stains and to improve the panel efficiency and color reproduction ratio.

Hereinafter, an example in which the white organic light emitting device of the present invention is implemented in a display device will be described.

4 is a schematic cross-sectional view of a display device to which the white organic light emitting device of the present invention is applied.

4, the display device of the present invention shows the specific structure of the blue light emitting unit 120 and the phosphorescent light emitting unit 140 in the above-described white organic light emitting device 1000, And a structure of the color filter layer 180 on the substrate 100 is further shown.

The first electrode 110 is formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

The second electrode 150 is formed of a metal such as gold (Au), aluminum (Al), molybdenum (Mo), chrome (Cr), or copper (Cu) With this structure, the blue peak emission in the blue light emitting unit 120 and the two-peak emission "yellowish green-YG-" and " reddish orange) -RO- "is mixed to realize white light emission.

In some cases, the material of the first electrode 110 and the second electrode 150 may be changed and applied in a top emission mode.

Here, one of the first electrode 110 and the second electrode 150 is an anode and the other is a cathode.

The blue light emitting unit 120 includes a first hole injecting layer 122, a first hole transporting layer 124, a blue light emitting layer 126, and a first electron transporting layer 128 on the first electrode 110 in order do.

The phosphorescent light emitting unit 140 includes a second hole transport layer 142, a phosphorescent light emitting layer 144, a second electron transport layer 146, and a first electron injection layer 148 in order from the bottom. As described above, the phosphorescent light-emitting layer 144 has a longer wavelength than that of blue in one host, that is, in a range of 548 nm to 554 nm (A region) and a third emission peak of 600 nm to 608 nm And a phosphorescent dopant capable of emitting light in the region B).

The charge generation layer 130 is formed between the blue light emitting unit 110 and the phosphorescent light emitting unit 140 to control the charge balance between the units. For this purpose, it may be formed of an alkali metal, an alkali metal compound, an organic material serving as an electron injecting or the like, or a compound thereof, which serves as an electron injection adjacent to the blue light emitting unit 110. Adjacent to the phosphorescent light emitting unit 140 And may be formed of an organic material used as a material of the hole injection layer to function as a hole injection. In some cases, the buffer layer may be included in the middle of the hole, so that the lower electron injection function and the upper hole injection function can be smoothly performed.

The first hole transporting layer 124, the first electron transporting layer 128, the second hole transporting layer 142 and the second electron transporting layer 148 adjacent to the respective light emitting layers 124 and 144 may be formed of triplet energy It is preferable to set the triplet energy level higher than the triplet energy state by 0.01 eV to 1.2 eV. This is to confine the triplet exciton used for luminescence in each luminescent layer, so that the luminescent layer can be used for luminescence with high efficiency.

The color filter layer 180 is formed on the substrate 100 on which one pixel is divided by a red subpixel R, a green subpixel G and a blue subpixel B, The color filters 180a, 180b and 180c of different colors correspond to each other. The illustrated example shows a separate white pixel, in which case the pixel design could be, for example, R, G, B, W in quad. The white pixel may be designed without a color filter layer, or may further include a transparent organic film corresponding to a white pixel in order to align layers with other color filter layers.

The structure shown is a structure of R, G, B, and W, and it is possible to exclude a white pixel and to have only R, G, and B pixels. In this case, it is possible to arrange R, G, and B pixels in a stripe shape.

The color filter layer 180 is disposed between the substrate 100 and the first electrode 110 and emits light radiated downward from the second electrode 150 to the first electrode 110, (180a, 180b, 180c), and transmits light of a corresponding color for each sub-pixel through the substrate 100. [ The white pixel transmits the white light emitted from the upper white organic light emitting device to the lower substrate 100 as it is.

Meanwhile, the charge generating layer 130 may be omitted in some cases. In this case, the lower electron transport layer 128 and the upper second hole transport layer 142 can also function as a charge generation layer.

The second electron transport layer 146 and the electron injection layer 148 may be formed as a first common layer in the same layer as the first common hole injection layer 122 and the first hole transport layer 124, And may be formed as a single layer with a common layer. In this case, the first electron transport layer 128 serves as a second common layer, and the second hole transport layer 142 serves as a third common layer.

FIG. 5 is a circuit diagram showing one pixel of the display device of the present invention, and FIG. 6 is a vertical sectional view showing R, G, B, and W pixels of the display device of the present invention.

5, one pixel of the display device of the present invention includes a cell driver 310 connected to a gate line GL, a data line DL and a power supply line PL, a cell driver 310 connected to the cell driver 310, And a white organic light emitting device WOLED connected equivalently as a diode.

The cell driver 310 includes a switch TFT T1 connected to the gate line GL and the data line DL and a switch TFT T1 connected to the power line PL and the white organic light emitting diode WOLED A driving thin film transistor T2 connected to one electrode and a storage capacitor C connected between the power supply line PL and the drain electrode of the switch thin film transistor T1.

The gate electrode of the switch thin film transistor T1 is connected to the gate line GL, the source electrode thereof is connected to the data line DL and the drain electrode thereof is connected to the gate electrode of the driving TFT T2 and the storage capacitor C . The source electrode of the driving thin film transistor T2 is connected to the power supply line PL and the drain electrode thereof is connected to the first electrode of the white organic light emitting diode WOLED. The storage capacitor C is connected between the power supply line PL and the gate electrode of the driving thin film transistor T2.

The switch thin film transistor T1 is turned on when a scan pulse is supplied to the gate line GL to supply the data signal supplied to the data line DL to the gate electrode of the storage capacitor C and the drive thin film transistor T2 do. The driving thin film transistor T2 controls the current I supplied from the power supply line PL to the white organic light emitting element WOLED in response to the data signal supplied to the gate electrode to reduce the amount of light emitted from the white organic light emitting element WOLED . Even if the switch thin film transistor T1 is turned off, the driving thin film transistor T2 supplies a constant current I until the data signal of the next frame is supplied by the voltage charged in the storage capacitor C, Thereby maintaining the light emission of the organic light emitting device WOLED.

6, the thin film transistor array substrate 2000 including the driving thin film transistor T2 includes a substrate 100 made of an insulating material, a gate electrode 101 formed on the substrate 100, a gate electrode 101 formed on the substrate 100, A semiconductor layer 103 formed on the gate insulating film 102; an etch stopper 104 provided on the semiconductor layer 103 on the gate electrode 101; And a source electrode 105a and a drain electrode 105b formed on both sides of the gate electrode 103, respectively.

A first protective film 107 of an inorganic film is formed to cover the source electrode 105 and the drain electrode 105b and R, G and B color filters are formed in the remaining pixel regions except for the driving TFT T2. 109b and 109c are formed on the first protective film 107 and the second protective film 108 of the organic film component which covers the entire surface of the first protective film 107 and the color filter layers 109a, Is formed.

Then, the second protective film 108 and the first protective film 107 are selectively removed to form a contact hole 108a.

Here, the semiconductor layer 103 is, for example, formed of an oxide semiconductor. The oxide semiconductor is formed of, for example, an oxide containing at least one metal selected from Zn, Cd, Ga, In, Sn, Hf and Zr. A thin film transistor including such an oxide semiconductor has advantages of a higher charge mobility and a lower leakage current characteristic than a thin film transistor including a silicon semiconductor layer. Further, a thin film transistor including an oxide semiconductor can be subjected to a low temperature process, and advantageously has a large area. In some cases, the semiconductor layer 103 may also be formed of a silicon semiconductor layer, in which case the etch stopper may be omitted.

The white organic light emitting device WOLED 1000 includes a first electrode 110 connected to the drain electrode 105b through the contact hole 108a on the thin film transistor substrate 1000 including the driving thin film transistor T2, A charge generation layer 130, a phosphorescent emission unit 140, and a second electrode 150. The blue emission unit 120 includes a blue emission layer that is formed without a mask in order.

7A and 7B and Table 1, the effect of the color recall ratio on the structure including one kind of dopant phosphorescent light emitting layer with iridium complex (Iridium complex) will be described.

In the comparative example (2 stack Ref), a two-stack tandem white organic light emitting device is provided with a phosphorescent light emitting unit and a blue fluorescent unit, each of which exhibits one emission peak. In the white organic light emitting device of the present invention, Emitting unit and a blue fluorescent unit are stacked.

Here, in the present invention and the comparative example, the external quantum efficiency of the blue fluorescent unit was matched at 9.5%.

In Table 1, the external quantum efficiency in the phosphorescent light-emitting layer of the phosphorescent light-emitting unit of the present invention is 18.5% for the YG wavelength and 4% for the RO wavelength, In the second embodiment, the YG wavelength is 16.9% and the RO wavelength is 5.6%. In the third embodiment, the YG wavelength is 15.0% and the RO wavelength is 7.5%.

FIG. 7A is a graph showing the embodiments of the white organic light emitting device of the present invention shown in Table 1 and the intensities of the two stack two-peak structures by wavelength.

As shown in FIG. 7A, in the first to third embodiments of the white organic light emitting device of the present invention, the emission peak corresponding to the green wavelength is about 548 nm to 554 nm, and the emission wavelength of the red light (near orange light emission rather than pure red light emission) The peak is in the range of 600 nm to 608 nm. The difference between the wavelengths representing the second emission peak and the third emission peak is 47 nm to 59 nm, which is approximately 50 nm.

7B is a graph showing the color reproduction rate of the present invention as compared with ATSC.

As shown in FIG. 7B and Table 1, the color gamut of the present invention is about 116.7% in the first embodiment, about 117.4% in the second embodiment, and 118.1% in the third embodiment, compared with the ATSC standard (shown as Ref).

Table 1 shows that the panel efficiency is lowered as the color reproducibility is relatively increased. Therefore, the panel efficiency and the color reproduction ratio of the appropriate phosphorescent dopant are selected to be superior to the comparative example and the ATSC standard. In the proposed embodiment, the first and second embodiments show that both panel efficiency and color gamut are superior to the comparative example and the ATSC standard.

Hereinafter, efficiency and luminescence characteristics according to the change of the difference between the second and third emission peaks will be described with reference to Table 2 and FIG.

8 is a graph showing the emission intensities of the white organic light emitting device according to the second and third emission peak wavelength differences of the present invention.

8 and Table 2, characteristics were observed with the second emission peak set to the same wavelength, and the wavelength difference between the second and third emission peaks set to 40 nm, 50 nm, and 60 nm, respectively, by changing the third emission peak. The external quantum efficiency of the blue light emission in the blue light emitting unit was 9.5%, and the external quantum efficiency in the phosphorescent light emitting layer in the phosphorescent light emitting unit was 18.5% for the YG wavelength and 4% for the RO wavelength.

Here, the color reproducibility is improved at each wavelength band, but when the thickness exceeds 60 nm, the panel efficiency is inferior to the structure of two stacks of two peaks (using a phosphorescent dopant having one peak emission characteristic in a phosphorescence emitting unit) structure. Therefore, the wavelength difference between the second and third emission peaks is set to less than 60 nm.

In the experimental example, the color reproduction ratio and the panel efficiency are most improved when the wavelength difference of the second and third emission peaks is about 50 nm. However, the present inventors have experimentally confirmed that the wavelength difference between the second and third emission peaks is at least 40 nm to 59 nm, and the panel efficiency is improved as compared with the two-stack peak structure. As the wavelength difference between the second emission peak and the third emission peak is relatively small, the decrease in the panel efficiency is relatively small. The difference between the second emission peak and the third emission peak is at least about 20 nm. Can be expected to have the same level of efficiency or higher.

As described above, the white organic electroluminescent device and the display device of the present invention are formed by two tandem devices of a blue fluorescent light emitting unit and a phosphorescent light emitting unit of longer wavelength than blue, and two light emitting peaks are possible as one dopant in the phosphorescent light emitting unit Thus, the color reproducibility improvement and the quantum efficiency of the corresponding emission peak of the dopant are suitably designed through the implementation of three peaks, and the panel efficiency is also improved.

In addition, by using one phosphorescent dopant, it is possible to solve the problem that the lifetime is reduced due to different lifetimes and luminescence characteristics when using different kinds of phosphorescent dopants, and it is possible to realize 3 peaks even in a two stack structure, Design is easy.

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.

100: substrate 110: first electrode
120: blue light emitting unit 130: charge generating layer
140: phosphorescent light emitting unit 150: second electrode
1000 (WOLED): white organic light emitting device

Claims (12)

Board;
A driving thin film transistor provided on the substrate and including a gate electrode, a source electrode, and a drain electrode;
An inorganic film protective layer covering the driving thin film transistor;
A color filter layer provided in a pixel region other than the driving thin film transistor;
An organic film protective layer covering the inorganic film protective layer and the color filter layer and having an upper surface formed flat;
A first electrode connected to the driving thin film transistor, the first electrode overlapping the color filter layer and positioned on the organic film protective layer;
A second electrode facing the first electrode;
A blue light emitting unit adjacent to the first electrode, the blue light emitting unit having a first emission peak at 430 nm to 480 nm;
A phosphorescent light-emitting unit adjacent to the second electrode and having a second emission peak and a third emission peak that differ from each other at 530 nm to 630 nm via a phosphorescent dopant of a single iridium complex in a single host; And
And an intermediate layer between the blue light emitting unit and the phosphorescent light emitting unit,
Wherein the second emission peak having a smaller wavelength in the phosphorescent light emitting unit is higher in emission intensity than the third emission peak and the wavelength difference between the second emission peak and the third emission peak is 40 nm to 59 nm. .
delete delete The method according to claim 1,
And the efficiency of the third emission peak wavelength region in the phosphorescent dopant is 17% to 38% of the efficiency of the second emission peak wavelength region. 5. The method of claim 4,
Wherein the efficiency of the second luminescence peak wavelength region has an external quantum efficiency of 16.0% to 19.5%, and the efficiency of the third luminescence peak wavelength region has an external quantum efficiency of 3.5% to 6.0% . The method according to claim 1,
Wherein the second emission peak is 548 nm to 554 nm, and the third emission peak is 600 nm to 608 nm. The method according to claim 1,
The total thickness from the first electrode to the second electrode immediately before the second electrode is 5000 ANGSTROM to 6000 ANGSTROM,
The layers including the first electrode and just before the second electrode

(lambda represents the luminescence peak wavelength of the blue light emitting unit or the phosphorescence emitting unit, n ^a and d ^a is the refractive index and thickness of the first electrode, and n ^w and d ^w are the refractive index and thickness of the layer positioned between the first electrode and the second electrode, respectively) device. The method according to claim 1,
Wherein the blue light emitting unit and the phosphorescent light emitting unit each include a light emitting layer, and an electron transporting layer and a hole transporting layer above and below the light emitting layer, respectively. Board;
A driving thin film transistor provided on the substrate and including a gate electrode, a source electrode, and a drain electrode;
An inorganic film protective layer covering the driving thin film transistor;
A color filter layer provided in a pixel region other than the driving thin film transistor;
An organic film protective layer covering the inorganic film protective layer and the color filter layer and having an upper surface formed flat;
A first electrode connected to the driving thin film transistor, the first electrode overlapping the color filter layer and contacting the organic film protective layer;
A blue light emitting unit adjacent to the first electrode, the blue light emitting unit having a first emission peak at 430 nm to 480 nm;
A phosphorescent light-emitting unit having, on the blue light-emitting unit, a second luminescence peak and a third luminescence peak which are different from each other at 530 nm to 630 nm through a phosphorescent dopant of a single iridium complex in a single host;
An intermediate layer between the blue light emitting unit and the phosphorescent light emitting unit; And
And a second electrode on the phosphorescent-emitting unit,
The second emission peak having a smaller wavelength in the phosphorescent light-emitting unit has a luminescence intensity higher than that of the third emission peak, and the wavelength difference between the second emission peak and the third emission peak is 40 nm to 59 nm.
delete delete 10. The method of claim 9,
And the efficiency of the third emission peak wavelength region in the phosphorescent dopant is 17% to 38% of the efficiency of the second emission peak wavelength region.

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