KR100796593B1 - Organic Electroluminescence Display Device - Google Patents

Abstract

The present invention discloses an organic electroluminescent device. An organic light emitting display device according to the present invention, comprising: a substrate; First electrodes spaced apart from each other on the substrate; Organic film layers on the first electrodes and including at least a blue light emitting layer; And a second electrode disposed on the organic layer, wherein the blue light emitting layer is formed of a host and a dopant, the peak wavelength of the emission spectrum of the dopant is 450 to 475 nm, and an area of a main peak. It is characterized by consisting of more than 80% of the light emitting material. As a result, it is possible to provide an organic light emitting device having high color purity and long life and high efficiency.

Organic light emitting diode, blue light emitting material, emission spectrum

Description

Organic Electroluminescence Display Device

1 is a cross-sectional view for explaining the structure of an organic light emitting display device according to the prior art.

2 is a cross-sectional view illustrating a structure of an organic light emitting display device according to an embodiment of the present invention.

3 is a graph showing an emission spectrum of a blue light emitting material according to Experimental Example 2 of the present invention.

4 is a graph showing an emission spectrum of a blue light emitting material according to Comparative Example 2 of the present invention.

* Description of the symbols for the main parts of the drawings *

100: substrate 110: buffer layer

120: semiconductor layers 120a and 120c; Source and drain regions

120c: channel region 130: gate insulating film

140: gate electrode 150: interlayer insulating film

160a and 160b source and drain electrodes

170: planarization film 175: via hole

180: first electrode 190: pixel defining layer

200: organic film layer 210: second electrode

The present invention relates to an organic light emitting device, and more particularly to an organic light emitting device comprising a blue light emitting layer having a long life and high efficiency.

Among flat panel display devices, an organic electroluminescence display device is a self-luminous display device that electrically excites an organic compound to emit light. In addition, the process can be simplified, low temperature production is possible, response speed is 1ms or less, high speed response speed, low power consumption, wide viewing angle, high contrast, and the like.

The organic light emitting device includes an organic light emitting layer between an anode electrode and a cathode electrode, so that holes supplied from the anode electrode and electrons received from the cathode electrode are combined in the organic light emitting layer to form an exciton, a hole-electron pair, and again. The excitons emit light by energy generated when the excitons return to the ground state.

Here, the organic light emitting diode may be divided into a bottom emission type and a top emission type according to a direction in which light generated from the organic light emitting layer is emitted. When the organic light emitting diode having the pixel driving circuit is a bottom emission type, the pixel driving circuit occupies the substrate. Due to its area, it is inevitably severely limited by the opening ratio. Therefore, the concept of the front light emitting organic light emitting device has been introduced to improve the aperture ratio.

1 is a cross-sectional view for explaining the structure of a top-emitting organic light emitting display device according to the prior art.

Referring to FIG. 1, a reflective metal film 11a and a transparent conductive film 11b are sequentially formed on a substrate 10 made of glass or plastic. The reflective metal film 11a is formed of a metal having good reflective properties such as aluminum (Al), aluminum alloy (Al alloy), silver (Ag), silver alloy (Ag alloy), and the transparent conductive film has a high work function. It is formed of indium tin oxide (ITO) or indium zinc oxide (IZO).

Subsequently, a photoresist pattern is formed on the transparent conductive film 11b, and the transparent conductive film 11b and the reflective metal film 11a are sequentially etched using the photoresist pattern as a mask. As a result, the first electrode 12 in which the reflective metal film 12a and the transparent conductive film 12b are sequentially stacked is formed. Then, the photoresist pattern is removed using a strip solution.

Next, a pixel defining layer 12 having an opening for exposing a part of the surface of the first electrode 11 is formed on the first electrode 11. Subsequently, an organic layer 13 is formed in the opening of the pixel definition layer 12. The organic layer 13 may include at least an organic light emitting layer, and may further include any one or more layers of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.

Subsequently, when the second electrode 14 made of Mg, Ag, Al, Ca, an alloy thereof, or the like is formed on the organic layer 13, the manufacture of the organic light emitting diode is completed.

In order to realize full-color with the organic light emitting device as described above, light emitting devices emitting three kinds of light of red, green, and blue are required, and a light emitting material is used differently when the organic light emitting layer is formed. To implement this.

Among the organic light emitting devices, green light emitting devices have been evaluated to have reached the level of practical use. However, red light emitting devices have low luminous efficiency. In particular, blue light emitting devices have diphenyl as a light emitting material. Although compounds such as anthracene, tetraphenylbutadiene and distyrylbenzene derivatives have been developed, there is a problem in that luminous efficiency, lifetime and color purity are poor. This is due to the increase in the shoulder of the emission spectrum due to the structure of the blue light emitting material, that is, the presence of isomers and the vibrational energy level.

As described above, the conventional organic EL device is difficult to realize full-color due to the difference in luminous efficiency and color purity of each light emitting device. In particular, the light emitting layers corresponding to the red, green, and blue colors have different lifetime characteristics. Therefore, it is difficult to maintain the white balance when driving for a long time.

The above problems are more prominent in the front light emitting organic light emitting device, and the front light emitting organic light emitting device has a transmittance of only 20 to 30%, which lowers the characteristics of the blue light emitting device than in the bottom light emitting organic light emitting device. Full-color implementation is a more difficult problem.

Accordingly, an object of the present invention is to provide an organic light emitting display device including a blue light emitting layer having a long lifetime and high efficiency, which is devised to solve the above problems.

In order to achieve the above object, the present invention is a substrate; First electrodes spaced apart from each other on the substrate; Organic film layers on the first electrodes and including at least a blue light emitting layer; And a second electrode disposed on the organic layer, wherein the blue light emitting layer is formed of a host and a dopant, the peak wavelength of the emission spectrum of the dopant is 450 to 475 nm, and an area of a main peak. Provided is an organic light emitting display device comprising at least 80% of a light emitting material.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view illustrating the structure of an organic light emitting display device according to an embodiment of the present invention.

Referring to FIG. 2, an insulating substrate 100 having red (a), green (b), and blue (c) pixel regions is provided. The buffer layer 110 may be formed over the entire surface of the insulating substrate 100. The buffer layer 110 serves to protect the thin film transistor formed in a subsequent process from impurities flowing out of the substrate 100.

The semiconductor layers 120 including source regions 120a, drain regions 120b, and channel regions 120c are formed on the buffer layer 110 for each of the pixel regions a, b, and c. .

Gate insulating layers 130 are formed on the semiconductor layers 120, and gates 140 are formed on the gate insulating layers 130 to correspond to the channel regions 120c, respectively.

Subsequently, source interlayers 150 may be formed to cover the gates 140, and source electrodes electrically contacting the source regions 120a and the drain regions 120b on the interlayer insulating layer 150, respectively. 160b and drain electrodes 160a are formed.

The semiconductor layers 120, the source electrodes 160b, the drain electrodes 160a, and the gates 140 each include thin film transistors positioned on the pixel regions a, b, and c, respectively. Form.

Subsequently, a planarization layer 170 is formed to cover the thin film transistors, and via holes 175 are formed in the planarization layer 170 to expose the drain electrodes 160b.

First electrodes 180 spaced apart from each other are formed on each of the pixel areas a, b, and c on the substrate on which the via holes 175 are formed. Thus, the first electrodes 180 are electrically connected to the drain electrodes 160b, that is, the thin film transistors, respectively, through the via holes 175. In the present exemplary embodiment, the first electrodes 180 may be formed on the reflective metal film and the reflective metal film by using a reflective electrode that reflects light, that is, silver, aluminum, silver alloy, aluminum alloy, etc. having high reflectance. It can be formed in a laminated structure of a transparent conductive film having a high work function. The first electrode 180, which is the reflective electrode, may be formed as an anode or a cathode.

A pixel definition layer 190 having an opening that exposes a portion of the surface of the first electrodes 180 is formed on a substrate on which the first electrodes 180 are formed. The pixel definition layer 190 is formed of, for example, an acrylic organic layer.

Subsequently, organic layers 200 including at least red, green, and blue light emitting layers are formed in the openings, respectively.

The light emitting layer may be formed of only a host or a dopant, but is preferable because the efficiency and brightness are very low, and the excimer characteristic occurs simultaneously in addition to the unique characteristics of each molecule due to self-packing between the molecules. I can't. Therefore, the light emitting layer is preferably formed by doping a dopant to the host.

The red light emitting layer may use a carbazole-based organic material as a host material. More preferably, the carbazole type may be CBP (carbazole biphenyl). The dopant material forming the red light emitting layer may be a phosphorescent dopant, a fluorescent dopant, or a mixed dopant thereof. For example, the phosphorescent dopant may be one selected from the group consisting of PIQIr (acac), PQIr (acac), PQIr (tris (1-phenylquinoline) iridium) and PtOEP. In addition, the fluorescent dopant may be one selected from the group consisting of DCJTB, DCDDC, AAAP, DPP and BSN.

The green light emitting layer may be formed using a tris-8-hydroxyquinolinate aluminum (hereinafter, referred to as Alq3) or stilbene derivative as a host material, and a dopant such as C545t.

The blue light emitting layer may use an anthracene-based material as a host material. Typical examples include MADN (binaphthyl-methylanthracene), TBDN (binaphthyl- (t-butylanthracene) and the like.

The dopant material of the blue light emitting layer may be formed of a light emitting material having a peak wavelength of 450 to 475 nm and an area of a main peak of 80% or more in order to increase color purity and luminous efficiency.

When the emission spectrum is a single spectrum, that is, when the light emitting material is composed of a single material, the maximum resonance effect can be obtained, so that the color purity and luminous efficiency are excellent, and the effect of collection life can be obtained. However, since most of the light emitting materials are isomers, when analyzing the emission spectrum, two or more peaks are synthesized to show a single peak. The two or more peaks may be divided into a main peak and a side peak according to their contents, and the two or more peaks may have different peak wavelengths and have different distributions and areas. It can represent the spectrum. The peak wavelength, distribution, and area of these two or more peaks are synthesized to determine the peak wavelength, distribution, and area of a single peak. Therefore, the larger the area of the main peak is closer to the single spectrum, so that the maximum resonance effect can be obtained. In the present invention, a light emitting material having an area of 80% or more of the main peak is used.

If the peak wavelength of the blue dopant is less than 450 nm or more than 475 nm, color coordinates of deep blue having excellent color purity are difficult to obtain. In addition, when the area of the main peak of the dopant is less than 80%, the change in characteristics according to the resonance distance is large, and the color purity is lowered by the destructive interference phenomenon. In addition, since the top emission type organic light emitting display device has a resonance structure with respect to a specific wavelength, there is a problem in that lifetime and luminous efficiency are deteriorated.

The blue dopant includes two or more aromatic amine units, and satisfies the above conditions among perylene-based, ananthanthrene-based, stilbene-based and non-stilbene-based. A material to be selected may be selected, and preferably a non-stilbene-based dopant may be used.

The organic layer 200 may further include at least one of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer.

The second electrode 210 is formed on the organic layer 200. In the present embodiment, the second electrode 210 is a transparent electrode and light emitted from the organic light emitting layer is emitted through the second electrode 210. The second electrode 210 is a cathode when the first electrodes 180 are an anode and an anode when the first electrodes 180 are a cathode.

The second electrode 210 may be formed of a transparent electrode such as ITO or IZO, or may be selected from the group consisting of Mg, Ag, Al, Ca, and alloys having a low work function to transmit light having a small thickness. It is formed of an electrode, preferably MgAg. Through the above process, the organic electroluminescent device including the blue light emitting layer having high color purity and high efficiency and long life is completed.

As described above, the present invention can improve the luminous efficiency of the device by using a light emitting material having a peak wavelength of 450 to 475 nm and an area of a main peak of 80% or more as a dopant of the blue light emitting layer. have. In addition, according to the present invention, by providing a blue organic electroluminescent device having excellent color purity and long life, it is easy to implement full-color.

Experimental Example 1

An anode having a reflective metal film and a transparent conductive film was formed on a substrate, and a blue light emitting layer was formed on the anode using BD119 (idemitsu). An organic light emitting diode was manufactured by forming a cathode on the blue light emitting layer.

Experimental Example 2

An organic light emitting diode device was manufactured under the same condition as Experimental Example 1, except that BD118 (idemitsu) was used as the blue light-emitting layer.

Comparative example  One

An organic light emitting diode was manufactured according to the same condition as Experimental Example 1 except that BD105 (idemitsu) was used as the blue light-emitting layer.

Comparative Example 2

An organic light emitting diode was manufactured according to the same condition as Experimental Example 1 except that BD052 (idemitsu) was used as the blue light emitting layer.

TABLE 1

Experimental Example 1 Experimental Example 2 Comparative Example 1 Comparative Example 2 Peak wavelength 460 472 453 452 % Of area of the main peak 90 80 60 65 Color coordinates (0.15,0.09) (0.14,0.11) (0.15.0.09) (0.15, 0.09) Efficiency (cd / A) 2.5 5.5 2 1.7

Table 1 is a table measuring color coordinates and luminous efficiency after the organic light emitting device was manufactured according to Experimental Examples 1 and 2 and Comparative Examples 1 and 2 as described above, and FIGS. 3 and 4 are Experimental Examples 2 and 2 It is a graph showing the emission spectrum according to.

Referring to Table 1 and Figure 3, according to Experimental Example 1 and Experimental Example 2, the organic electroluminescent device was manufactured using a light emitting material having an area ratio of 80% or more of the main peak of the emission spectrum is excellent in color purity, It can be seen that the efficiency is also excellent. (The graph shown in Fig. 3 is the emission spectrum of Experimental Example 2, where A shows a synthesized single peak, B represents the main peak, C represents the minor peak, and the area ratio of the main peak is 80%.)

However, looking at the experimental results of Comparative Example 1 and Comparative Example 2, the area ratio of the main peak of the emission spectrum is about 60 to 65%, it can be seen that the color purity is relatively good but the luminous efficiency is low. (The graph shown in Fig. 4 is the emission spectrum of Comparative Example 2, where D shows a synthesized single peak, E represents the main peak, F represents the minor peak, and the area ratio of the main peak is 65%.)

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not so limited, and the invention is not limited to the spirit and scope of the invention as defined by the following claims. It will be readily apparent to one of ordinary skill in the art that various modifications and variations can be made.

As described above, the present invention can provide an organic light emitting display device having an excellent color purity and including a blue light emitting layer having a light emitting efficiency and a long lifespan.

Claims (8)

Board; First electrodes spaced apart from each other on the substrate; Organic film layers on the first electrodes and including a blue light emitting layer; And A second electrode on the organic layer; The blue light emitting layer is composed of a host and a dopant, and the peak wavelength of the emission spectrum of the dopant is 450 to 475 nm, the area of the main peak (main peak) of the organic light emitting device, characterized in that made of a light emitting material. The method of claim 1, The dopant is organic electroluminescence, characterized in that any one selected from the group consisting of perylene-based, ananthrene-based, stilbene-based and bistilbene-based aromatic amine device. The method of claim 2, The dopant is an organic light emitting device, characterized in that the bistilbene (non-stilbene) aromatic amine. The method of claim 1, The first electrode is an organic light emitting display device, characterized in that consisting of a reflective metal film and a transparent conductive film. The method of claim 1, The host is an organic light emitting device, characterized in that the anthracene (anthracene) -based material. The method of claim 5, The host is an organic light emitting display device, characterized in that MADN (binaphthyl-methylanthracene) or TBDN (binaphthyl- (t-butylanthracene). The method of claim 1, The organic layer may further include a red light emitting layer and a green light emitting layer. The method of claim 1, The organic light emitting device of claim 1, further comprising thin film transistors connected to the first electrodes.

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