KR20160067667A - Organic light emitting device and display device having thereof - Google Patents

Abstract

An organic luminescent device of the present invention prevents a decrease in light emitting efficiency and durability due to hole and electron distribution imbalance inside a first organic light emitting layer of a first stack or a second organic light emitting layer of a second stack by thickening the thickness (x) of a first electron generating layer thicker than that of a second electron generating layer (y), and enhancing a quantity of electrons supplied to the first organic light emitting layer of the first stack or the second organic light emitting layer of the second stack.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic electroluminescent device,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent device having improved luminous efficiency and lifetime, and a display device having the same.

An organic electroluminescent device is an element which converts electric energy into light by applying an electric field to an organic material, and is becoming an ideal display device having all elements as self-emission, fast response, wide viewing angle, ultra-thin and high picture quality. Studies on such organic electroluminescent devices have mainly been carried out mainly on techniques for the implementation of display devices such as blue, green and red, and have developed materials with high efficiency and long lifetime with excellent color purity of a single wavelength, Respectively.

However, at present, the possibility of a white organic electroluminescent device utilizing characteristics of an organic material including various colors and a wide visible region is recognized and studies are being conducted. Such a white organic electroluminescent device is recognized as a major element because of its wide application fields such as illumination, backlight, display device and the like.

The development of such a white organic electroluminescent device has been mainly focused on high efficiency, prolongation of life, improvement of color purity, color stability according to current and voltage change, easiness of manufacturing, and research and development is progressing according to each method. The structure of a white organic electroluminescent device can be divided into a single layer light emitting structure, a multi-layer structure, and a down conversion structure.

The single-layered light-emitting structure has a structure in which mixed light emission is performed in a single layer using R, G, B or a complementary color relationship. . The down conversion structure has a disadvantage in that the structure is simple but the efficiency is low because blue light is used and white is realized using color conversion through a red phosphor.

The multilayered light emitting layer structure has a tandem structure including a blue fluorescent light emitting layer and a yellow-green phosphorescent light emitting layer, and has an advantage of a long life. However, the white organic light emitting device having such a tandem structure has a problem that the driving voltage is high and the efficiency is low. Further, since the light emitting region can not be formed in the light emitting layer, the device efficiency and lifetime are reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic electroluminescent device with improved lifetime and efficiency.

It is another object of the present invention to provide an organic electroluminescent display device having the organic electroluminescent device.

In order to achieve the above object, in the present invention, the thickness (x) of the first charge generating layer is made larger than the thickness of the second charge generating layer (y) The amount of electrons supplied to the second organic emission layer in the stack can be increased to prevent the emission efficiency and the lifetime from being unbalanced due to the distribution of holes and electrons in the first organic emission layer.

At this time, the thickness ratio (x: y) of the first charge generation layer and the second charge generation layer y is set to 1.1: 1 or more, preferably 1.1: 1-1.2: 1.

The total thickness (x) of the first charge generation layer is set to 400 ANGSTROM or less when the thickness of the N-CGL layer of the first charge generation layer is 180 ANGSTROM or more and the thickness of the P-CGL layer is 80 ANGSTROM.

The organic electroluminescence display device includes a pixel including W, R, G, and B pixels, and a color filter layer and an organic electroluminescent device having the above structure. The white light emitted from the organic electroluminescent device passes through the color filter layer, .

In the present invention, by controlling the thickness of the first charge generation layer and the second charge generation layer, the amount of the electrons flowing from the first charge generation layer or the second charge generation layer into the hole injected from the anode to the organic emission layer is balanced , It is possible to improve the luminous efficiency and lifetime by optimizing the bonding of holes and electrons in the organic light emitting layer.

By optimally combining the holes and electrons, holes or electrons that are not bonded can be minimized, so that the lifetime of the organic electroluminescent device can be improved.

1 is a cross-sectional view illustrating a structure of an organic light emitting display device according to the present invention.
2 is a view schematically showing a structure of an organic electroluminescent device according to the present invention.
3 is a view showing a specific structure of an organic electroluminescent device according to the present invention.
4A and 4B are graphs each showing a relationship between the lifetime of the first organic emission layer and the thickness of P-CGL and N-CGL in the first charge generation layer of the organic electroluminescent device according to the present invention.
5 is a graph showing the relationship between the thickness ratio (x: y) of the first charge generation layer and the second charge generation layer of the organic electroluminescence device according to the present invention and the lifetime of the device.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, and the like disclosed in the drawings for describing the embodiments of the present invention are illustrative, and thus the present invention is not limited thereto. Like reference numerals refer to like elements throughout the specification. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. In the case where the word 'includes', 'having', 'done', etc. are used in this specification, other parts can be added unless '~ only' is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

In the case of a description of the positional relationship, for example, if the positional relationship between two parts is described as 'on', 'on top', 'under', and 'next to' Or " direct " is not used, one or more other portions may be located between the two portions.

In the case of a description of a temporal relationship, for example, if the temporal relationship is described by 'after', 'after', 'after', 'before', etc., May not be continuous unless they are not used.

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

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other, partially or wholly, technically various interlocking and driving, and that the embodiments may be practiced independently of each other, It is possible.

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

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

As shown in FIG. 1, the organic light emitting display according to the present embodiment includes a W pixel for outputting white light, an R pixel for outputting red light, a G pixel for outputting green light, and a B pixel outputting blue light. A color filter layer is formed in each of the R, G, and B pixels to output white light output from the organic light emitting portion as light of a specific color. However, if W pixels are disposed, .

As described above, in the present invention, the white light including the W pixel is output, thereby improving the overall luminance of the organic light emitting display device. However, in the present invention, the W pixel is not provided, and only the R, G, and B pixels may be formed.

As shown in FIG. 1, a first substrate 10 made of a transparent material such as glass or plastic is divided into R, G, and B pixels, and a driving thin film transistor is formed in each of R, G, and B pixels.

The driving thin film transistor includes gate electrodes 11W, 11R, 11G and 11B formed on the W, R, G and B pixels respectively on the first substrate 10 and the gate electrodes 11W, 11R, 11G and 11B The semiconductor layers 12W, 12R, 12G and 12B formed over the entire first substrate 10 and the source electrodes 14W, 14R, 14G and 14B formed on the semiconductor layers 12W, 12R, 12G and 12B, Drain electrodes 15W, 15R, 15G, and 15B. 14R, 14G, and 14B and the drain electrodes 15W, 15R, 15G, and 15B are formed on the top surface of the semiconductor layers 12W, 12R, 12G, and 12B, It is possible to prevent the semiconductor layers 12W, 12R, 12G, and 12B from being etched during the etching process of FIG.

Although not shown in the drawing, gate lines are formed on the first substrate 10 simultaneously with the formation of the gate electrodes 11W, 11R, 11G, and 11B.

The gate electrodes 11W, 11R, 11G and 11B may be formed of a metal such as Cr, Mo, Ta, Cu, Ti, Al or Al alloy. The gate insulating layer 22 may be made of SiO ₂ or SiN x A single layer made of an inorganic insulating material or a double layer made of SiO ₂ and SiN x. The semiconductor layers 12W, 12R, 12G, and 12B are formed of an amorphous semiconductor material such as amorphous silicon or a polycrystalline semiconductor material. The semiconductor layers 12W, 12R, 12G, and 12B may be formed of an oxide semiconductor such as IGZO (Indium Gallium Zinc Oxide). The source electrodes 14W, 14R, 14G, and 14B and the drain electrodes 15W, 15R, 15G, and 15B may be formed of Cr, Mo, Ta, Cu, Ti, Al, Al alloy or an alloy thereof.

Although data lines are formed in the gate insulating layer 22 and the formation of the source electrodes 14W, 14R, 14G and 14B and the drain electrodes 15W and 15R, 15G and 15B, And define W, R, G, and B pixels together with

A first insulating layer 24 is formed on the first substrate 10 on which the driving thin film transistor is formed. The first insulating layer 24 may be formed of an inorganic insulating material such as SiO ₂ . An R-color filter layer 17R, a G-color filter layer 17G, and a B-color filter layer 17B are formed on the R, G, and B pixels of the first insulating layer 24, respectively. At this time, no color filter layer is formed in the W pixel.

As the signal is applied to the gate electrodes 11W, 11R, 11G and 11B, the semiconductor layers 12W, 12R, 12G and 12B are activated to form the source electrodes 14W, 14R, 14G and 14B and the drain electrodes 15W Channel layers are formed in the semiconductor layers 12W, 12R, 12G, and 12B between the source electrodes 15R, 15G, and 15B.

In the above description, the gate electrodes 11W, 11R, 11G and 11B are formed on the first substrate 10 and the semiconductor layers 12W, 12R, 12G and 12B are formed on the gate electrodes 11W, 11R, 11G and 11B ), But the present invention is not limited to the thin film transistor of this specific structure.

For example, a top gate thin film transistor (TFT) in which semiconductor layers 12W, 12R, 12G and 12B are formed on a first substrate 10 and gate electrodes 11W, 11R, 11G and 11B are formed on the semiconductor layers 12W, .

A second insulating layer 26 is formed on the R-color filter layer 17R, the G color filter layer 17G, and the B color filter layer 17B. The second insulating layer 26 is an overcoat layer for planarizing the first substrate 10 and may be formed of an organic insulating material such as photo-acryl.

Pixel electrodes 64W, 64R, 64G, and 64B are formed on the W, R, G, and B pixels on the first insulating layer 26, respectively. The upper insulating layer 24 and the second insulating layer 26 of the drain electrodes 15W, 15R, 15G and 15B of the driving thin film transistors formed on the W, R, G and B pixels are provided with contact holes The pixel electrodes 64W, 64R, 64G and 64B are formed in the contact holes 29 and are electrically connected to the drain electrodes 15W, 15R, 15G and 15B of the exposed driving thin film transistors . The pixel electrodes 64W, 64R, 64G, and 64B are made of a transparent metal oxide material such as ITO or IZO having good conductivity.

A bank layer 28 is formed in each pixel boundary region on the second insulating layer 26 and the pixel electrodes 64W, 64R, 64G, and 64B. The bank layer 28 is a kind of barrier rib for preventing each pixel from being mixed and outputting light of a specific color outputted from adjacent pixels. Since the bank layer 28 fills a portion of the contact hole 29, the step is reduced. As a result, charge is concentrated on the step of forming the organic light emitting portion 23, so that the life of the organic light emitting portion 23 Can be prevented from deteriorating.

An organic light emitting portion 23 is formed on the entire surface of the first substrate 16 on the pixel electrodes 64W, 64R, 64G, and 64B and the bank layer 28. [ The organic light emitting portion 23 includes a white organic light emitting layer for emitting white light.

The white organic light emitting layer is a tandem structure including a blue light emitting layer and a yellow-green light emitting layer. The tantalum structure includes not only the light emitting layer but also an electron injecting layer and a hole injecting layer for injecting electrons and holes respectively into the organic light emitting layer, An electron transporting layer and a hole transporting layer respectively transported to the organic light emitting layer, and a charge generating layer for generating charges such as electrons and holes.

A common electrode 25 is formed on the entire surface of the first substrate 10 on the organic light emitting portion 23. The common electrode 25 is made of Ca, Ba, Mg, Al, Ag or the like.

The organic light emitting portion 23, the common electrode 25, and the pixel electrodes 64W, 64R, 64G, and 64B form an organic electroluminescent device. At this time, the common electrode 25 is the cathode of the organic electroluminescent device and the pixel electrodes 64W, 64R, 64G and 64B are the anode, and the common electrode 25 and the pixel electrodes 64W, 64R, Electrons are injected from the common electrode 25 into the organic light emitting portion 23 and holes from the pixel electrodes 64W, 64R, 64G and 64B are injected into the organic light emitting portion 23 Excitons are generated in the organic light emitting layer and light corresponding to the energy difference between LUMO (Lowest Unoccupied Molecular Orbital) and HOMO (Highest Occupied Molecular Orbital) of the light emitting layer is generated as the exciton is decayed (Toward the first substrate 10 in the drawing). At this time, white light is emitted from the organic light emitting layer, and the white light passes through the R, G, and B color filter layers 17R, 17G, and 17B, and outputs only light of a color corresponding to the pixel.

Since the white light is not transmitted through the color filter layer, the luminance is higher than the light transmitted through the color filter layers 17R, 17G, and 17B. Therefore, It is possible to improve the luminance of the display device.

An adhesive layer 42 is formed on the upper portion of the common electrode 25 and a second substrate 50 is disposed on the adhesive layer 42. The second substrate 50 is bonded to the first substrate 50 by the adhesive layer 42, (10) are attached to each other.

As the adhesive, any material can be used as long as it is a material having good adhesion and good heat resistance and water resistance. In the present invention, a thermosetting resin such as an epoxy compound, an acrylate compound, or an acryl- Lt; / RTI > At this time, the adhesive layer 42 is applied in a thickness of about 5-100 [mu] m and cured at a temperature of about 80-170 [deg.] C. The adhesive layer 42 not only bonds the first substrate 10 and the second substrate 50, but also acts as an encapsulant for preventing moisture from penetrating into the organic light emitting display device. Therefore, although the term 42 is referred to as an adhesive in the detailed description of the present invention, this is for convenience only, and the adhesive layer may be referred to as an encapsulant.

The second substrate 50 may be made of glass or plastic. The protective layer 50 may be a protective film such as a polystyrene (PS) film, a polyethylene (PE) film, a polyethylene naphthalate (PEN) film, or a polyimide (PI) film. The second substrate 50 may be any material as long as it can protect the components formed on the first substrate 10.

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

2, the organic electroluminescence device includes an anode 102 and a cathode 104, and a first to third stacks 110, 130, and 150 are formed between the anode 102 and the cathode 104 Charge generation layers 120 and 140 are disposed between the stacks 110, 130 and 150, respectively. Hereinafter, as will be described, if each stack 110, 130, 150 comprises a plurality of layers comprising an organic light emitting layer, then the first stack 110 and the third stack 150 comprise a blue organic light emitting layer emitting blue light, 2 stack 130 includes a yellow-green organic light emitting layer emitting yellow-green light.

The blue organic light emitting layers of the first stack 110 and the third stack 150 are doped with blue fluorescent material and emit blue light by fluorescence and the yellow and green organic light emitting layers of the second stack 130 emit yellow and green phosphors Is doped to emit yellow-green light.

As described above, the reason why the organic electroluminescent device is formed into a plurality of laminated structures in the present invention is as follows.

First, by forming the organic electroluminescent device into a plurality of laminated structures, the luminous efficiency of the organic electroluminescent device can be improved. In the organic electroluminescent device having a laminated structure, the recombination region of holes and electrons can be regulated so as to be formed in both the fluorescent layer and the phosphorescent layer, whereby light emission can be obtained from both fluorescence and phosphorescence. Therefore, the luminous efficiency is improved as compared with the single-layer structure.

Second, by forming the organic electroluminescent devices into a plurality of laminated structures, the lifetime of the organic electroluminescent device can be extended. When the white light having the same luminance as that of the single layer structure is emitted in the organic electroluminescent device having the laminated structure, the brightness of the white light emitted from each layer of the laminated structure can be reduced by the number of the laminated layers, So that it can be extended.

Thirdly, by forming the organic electroluminescent device into a plurality of laminated structures, the driving voltage of the organic electroluminescent device can be lowered. In the organic electroluminescent device having a stacked structure, since the charge generation layer is provided between each stack, the driving power can be reduced as compared with the organic electroluminescent device that emits white light of the same luminance.

The first charge generation layer CGL1 120 and the second charge generation layer CGL2 140 may be referred to as an intermediate connector layer since they serve to control charge balance between adjacent stacks 110, . The first charge generation layer (CGL1) 120 and the second charge generation layer (CGL2) 140 generate holes and electrons and inject the electrons into the first to third stacks 110, 130 and 150, respectively.

3 is a view showing the structure of an organic electroluminescent device in which the structure of the first to third stacks 110, 130 and 150 is specifically shown.

3, a first stack 110 of the organic electroluminescent device according to the present invention is disposed between the anode 102 and the first charge generating layer 120. The first stack 110 includes a hole injection layer 112 disposed on the anode 102 and a hole transporting layer 112 disposed on the hole injection layer 112 for transporting injected holes. ; A first organic emission layer 116 disposed on the first hole transport layer 114 and a first electron transport layer 118 disposed on the first organic emission layer 116 .

The hole injection layer 112, the first hole transport layer 114, and the first electron transport layer 118 are provided to improve the luminous efficiency of the first organic emission layer 116. At least one of the hole injecting layer 112, the first hole transporting layer 114 and the first electron transporting layer 118 may be omitted depending on the structure and characteristics of the device, But is not limited thereto.

In general, carrier mobility in organic materials is generally known to be higher than electrons because of ionization potential and electron affinity. That is, the excitons are generated near the electrodes because electrons can not easily move in the organic materials, but the quantum efficiency of the organic light emitting devices is lowered due to the large non-emission disappearance near the electrodes. Accordingly, in order to improve the efficiency of the device, electrons and holes are sufficiently injected into the organic light emitting layer, and the distribution of injected electrons and holes must be balanced. The ideal light emitting device should have a coincidence between the Fermi level of the electrode metal and the HOMO and LUMO levels of the light emitting material.

In order to match the Fermi level of the electrode metal with the HOMO and LUMO levels of the light emitting material, the structure of the light emitting device is formed into a heterostructure by using two or more organic materials having different band gaps. A first hole injection layer 112 which is a charge injection layer, a first hole transport layer 114 which is a charge transport layer and a first electron transport layer 118 are provided for forming a heterojunction structure.

Since the first hole transporting layer 114 is made of an organic material and the anode 102 is made of ITO which is an inorganic material, the interface characteristics between the first hole transporting layer 114 and the anode 102 are poor due to the difference between inorganic and organic materials, As a result, the holes from the anode 102 to the first hole transporting layer 114 are not smoothly injected. The hole injection layer 112 improves the interfacial property by reducing the surface energy difference between the first hole transport layer 114 and the anode 102 and improves the work function of the hole injection layer 112 The energy level difference between the work function level of the anode 102 and the HOMO level of the first hole transport layer 114 is set by setting the intermediate level between the functional level and the HOMO level of the first hole transport layer 114, As described above, by the improvement of the interface characteristics between the first hole transporting layer 114 and the anode 102 and the reduction of the energy difference between the work function level of the anode 102 and the HOMO level of the first hole transporting layer 114, The injection of holes from the first hole transport layer 102 to the first hole transport layer 114 is smooth.

The first hole transporting layer 114 and the first electron transporting layer 118 adjust the mobility of holes and electrons to control the mobility of holes and electrons. Since the mobility of electrons in the organic material is smaller than the mobility of holes, the first hole transport layer 114 and the first electron transport layer 118 control the movement of holes and electrons so that the movement of electrons is larger than the movement of holes , The electrons are quickly introduced into the collision radius capable of recombining with the holes, thereby increasing the luminous efficiency.

Although not shown in the figure, an electron blocking layer may be disposed between the first hole transport layer 114 and the first organic emission layer 116, and a hole (not shown) may be formed between the first organic emission layer 116 and the first electron transport layer 118. [ A blocking layer may be disposed. The electron blocking layer prevents electrons from flowing from the first organic light emitting layer 116 to the first hole transporting layer 114 and is trapped in the first organic light emitting layer 116 to improve the luminous efficiency of the first organic light emitting layer 116.

The first organic light emitting layer 116 of the first stack 110 is a blue light emitting layer, and at least one host includes a dopant of a blue fluorescent material to emit blue light.

The second stack 130 includes a second hole transport layer (HLT2) 132 disposed on the first charge generation layer 120, a second organic emission layer (EML2) 134 disposed on the second hole transport layer 132, And a second electron transport layer (ETL2) 136 disposed on the second organic light emitting layer 134.

As described above, the second hole transporting layer 132 and the second electron transporting layer 136 are provided to improve the luminous efficiency of the second organic light emitting layer 134. At least one of the second hole transporting layer 132 and the second electron transporting layer 134 may be omitted depending on the structure or characteristics of the device, or may be formed by other layers. However, the present invention is not limited thereto.

The second organic light emitting layer 134 of the second stack 130 comprises at least one host, a yellow phosphorescent material doped together with the host, and a green phosphorescent material to emit yellow-green light. Alternatively, the second organic emission layer 134 may be composed of a red phosphorescent material and a green phosphorescent material on at least one host, and red-green light may be emitted. Alternatively, the second organic emission layer 134 may be formed of two emission layers, i.e., a red emission layer and a green emission layer, and red light and green emission may be emitted.

Although not shown in the figure, an electron blocking layer may be disposed between the second hole transporting layer 132 and the second organic emission layer 134. As described above, since the energy level of the second hole transporting layer 132 is higher than the energy level of the excited state of the triplet excitons of the second organic emission layer 134, the triplet excitons of the second organic emission layer 134 reach the second In the present invention, by forming the hole blocking layer, electrons and holes are prevented from being introduced into the second hole transporting layer 132 in the second organic light emitting layer 134 It is possible to prevent the luminous efficiency from being lowered. Similarly, a hole blocking layer may be formed between the second organic luminescent layer 134 and the second electron transporting layer 136.

The third stack 150 includes a third hole transport layer (HTL3) 152 disposed on the second charge generation layer 140, a third organic emission layer (EML3) 154 disposed on the third hole transport layer 152, A third electron transport layer ETL3 156 disposed on the third organic emission layer 154 and an electron injection layer 158 disposed on the third electron transport layer 156. [

The third organic light emitting layer 154 is a blue light emitting layer, and a host contains a dopant of a blue fluorescent material to emit blue light. At this time, the host and the dopant may be made of the same material as the first organic emission layer 116

The electron injection layer 158 improves the interfacial property by reducing the surface energy difference between the third electron transporting layer 156 and the cathode 104 and enhances the work function of the electron injecting layer 158 to the surface of the cathode 104 The energy level difference between the work function level of the cathode 104 and the LUMO level of the third electron transport layer 156 is set by setting the intermediate level between the functional level and the LUMO level of the third electron transport layer 156. [ As described above, by the improvement of the interface characteristics between the third electron transporting layer 156 and the cathode 104 and the reduction of the energy difference between the work function level of the cathode 104 and the LUMO level of the third electron transporting layer 156, The injection from the cathode 104 to the third electron transporting layer 156 is smoothly performed.

As described above, the third hole transport layer 152 and the third electron transport layer 156 are provided to improve the luminous efficiency of the third organic light emitting layer 154. An electron blocking layer may be formed between the third hole transporting layer 152 and the third organic emitting layer 154 and between the third organic emitting layer 154 and the third electron transporting layer 156 A hole blocking layer may be formed. At least one of the third hole transport layer 152, the third electron transport layer 156 and the electron injection layer 158 may be omitted depending on the structure and characteristics of the device, But is not limited thereto.

As described above, the organic electroluminescent device of the present invention emits blue light in the first stack 110 and the third stack 150, emits yellow-green light in the second stack 130, Direction as shown in FIG. Alternatively, the first stack 110 and the third stack 150 emit blue light, and the second stack 130 emits red-green light. These lights are mixed and output as white light through the lower direction.

At least one host may include a dopant of a blue fluorescent material in the first organic light emitting layer 116 of the first stack 110 and the third organic light emitting layer 154 of the third stack 150, The second organic light emitting layer of the second stack 130 includes a dopant of a yellow-green phosphorescent material and emits yellow-green light. At least one of the hosts is doped with a fluorescent material, The reason for doping the phosphorescent material into the green light emitting layer is as follows.

Fluorescent materials have excellent device stability, but they have limitations in achieving high efficiency. On the other hand, the phosphor can achieve high efficiency, but there is no substance capable of emitting stable blue light. In order to complement the advantages and disadvantages of the fluorescent material and the phosphorescent material, a hybrid structure including a fluorescent light emitting layer and a phosphorescent light emitting layer is used in the present invention. In particular, a fluorescent material is doped in a blue light emitting layer and a phosphorescent material is doped in a yellow- , It is possible to emit stable blue light and to maximize the luminous efficiency.

However, the present invention is not limited to a structure in which a blue light emitting layer is doped with a fluorescent material, but a blue light emitting layer may be doped with a phosphorescent material.

3, the first charge generating layer 120 includes a first P type charge generating layer (P-CGL1) 124 and a first N type charge generating layer (N-CGL1) 122, The first charge generating layer 12 is formed to a thickness of x. The P-CGL1 124 is formed of an organic semiconductor layer including a P-type organic material, and the N-CGL1 122 is formed of a host and an organic material layer doped with an electron-deficient metal such as an alkali metal or an alkaline earth metal, Lt; / RTI >

Holes and electrons are generated at the interface between the P-CGL1 124 and the second hole transporting layer 132 of the second stack 130 in the first charge generating layer 120 having the above structure. The generated holes flow into the second organic emission layer 134 through the hole transport layer 132 of the second stack 130. The generated electrons are injected into the first stack 110 through the electron transport layer 118 of the first stack 110, Emitting layer 116 of the light-emitting layer 110.

The second charge generation layer 140 is formed of a first P type charge generation layer (P-CGL2) 144 and a second N type charge generation layer (N-CGL1) 142, 140 are formed with a thickness of y. The P-CGL2 144 is made of an organic semiconductor layer including a P-type organic material, and the N-CGL2 142 is made of an organic material layer in which an electron and a deficient metal such as an alkali metal or an alkaline earth metal are doped with a dopant.

Holes and electrons are generated at the interface between the P-CGL 2 424 and the third hole transporting layer 152 of the third stack 150. The generated holes are introduced into the third organic light emitting layer 154 through the third hole transporting layer 152 of the third stack 150. The generated electrons are injected through the electron transporting layer 136 of the second stack 130 2 stack 110 in the second organic light emitting layer 134. [

As described above, the reason why the first charge generating layer 120 and the second charge generating layer 140 are provided in the present invention is as follows.

When the organic electroluminescent device is driven, holes are injected from the anode 102 into the first stack 110, and electrons are injected from the cathode 102 into the third stack 150.

The holes injected from the anode 102 flow into the first organic light emitting layer 116 through the hole injection layer 112 and the first hole transport layer 114 of the first stack 110. At the same time, electrons and holes are generated in the first charge generating layer 120, and the generated electrons are introduced into the first organic light emitting layer 116 through the first electron transporting layer 118 of the first stack 110. Electrons and holes injected into the first organic emission layer 116 are excited in the first organic emission layer 116 and energy of the LUMO and HOMO of the first organic emission layer 116 is decreased as the excitons decay. The light corresponding to the difference is generated. At this time, since the first organic emission layer 116 is doped with a blue dopant, blue light is emitted.

Electrons injected from the cathode 104 flow into the third organic light emitting layer 154 through the electron injection layer 158 and the third electron transport layer 156 of the third stack 150. At the same time, electrons and holes are generated in the second charge generating layer 140, and the generated holes flow into the third organic light emitting layer 154 through the third hole transporting layer 152 of the third stack 150. Electrons and holes introduced into the third organic emission layer 154 are excited in the third organic emission layer 154. As the exciton decays, the energy of the LUMO and HOMO of the third organic emission layer 154 The light corresponding to the difference is generated. At this time, since the third organic emission layer 154 is doped with a blue dopant, blue light is emitted.

The holes generated in the first charge generation layer 120 are injected into the second organic emission layer 134 through the second hole transport layer 132 of the second stack 130. At the same time, the electrons generated in the second charge generation layer 140 flow into the second organic emission layer 134 through the second electron transport layer 136 of the second stack 130. Electrons and holes injected into the second organic emission layer 134 are excited in the second organic emission layer 134. As excitons are decayed, energy of the LUMO and HOMO of the second organic emission layer 134 The light corresponding to the difference is generated. At this time, since the second organic emission layer 134 is doped with a yellow-green dopant, yellow-green light is emitted.

As described above, in the present invention, blue light is emitted in the first stack 110 and the third stack 150, and yellow-green light is emitted in the second stack 130, and these lights are mixed and output as white light.

In the present invention, the lifetime of the organic electroluminescent device is optimized by controlling the thicknesses of the first charge generating layer 120 and the second charge generating layer 140, for the following reasons.

Electrons are injected from the cathode 104 and holes are injected from the second charge generation layer 140 into the third organic emission layer 154 of the third stack 150. [ In the first organic light emitting layer 116 of the first stack 110, holes are injected from the anode 102 and electrons are injected from the first charge generating layer 120

Electrons flow from the cathode 104 into the third organic luminescent layer 154 and electrons flow into the first organic luminescent layer 116 from the first charge generating layer 120. Therefore, 3 electrons are smoothly and sufficiently supplied to the organic light emitting layer 154.

On the other hand, since holes are introduced into the third organic emission layer 154 from the second charge generation layer 140 and holes are injected into the first organic emission layer 116 from the anode 102, Holes are smoothly and sufficiently supplied to the first organic light-emitting layer 116.

In other words, a large amount of electrons are sufficiently supplied to the third organic emission layer 154, but a relatively small amount of holes are supplied. On the other hand, a large amount of holes are sufficiently supplied to the first organic emission layer 116, Small amounts are supplied. Accordingly, unbalance occurs in the supply of electrons and holes to the first organic light emitting layer 116 and the third organic light emitting layer 154, and due to this imbalance, ) And the third organic light emitting layer 154 decrease. In addition, a large amount of holes and electrons are not present in the first organic light emitting layer 116 and the third organic light emitting layer 154, and these unconjugated holes and electrons cause a decrease in lifetime of the organic electroluminescence device .

The thickness of the first charge generation layer 120 and the second charge generation layer 140 may be controlled to control the amount of electrons injected into the first and third organic emission layers 116 and 154 Thereby preventing problems such as the above-described light emitting efficiency and life span.

In the charge generation layer, electrons and holes are generated at the interface between the P-CGL1 and the hole transport layer of the stack, and the generated charge is pumped to the LUMO of the N-CGL containing the alkali metal. Therefore, when the thickness of the P-CGL and the N-CGL is less than the set value, sufficient charge is not generated, and the charge is not smoothly transferred to the organic light emitting layer, thereby reducing the lifetime. When the thickness of the P-CGL and the N-CGL is more than the set value, a time difference occurs between the holes and the electrons reaching the organic luminescent layer, causing an imbalance between the holes and electrons in the organic luminescent layer, .

As described above, holes are injected into the organic light emitting layer 116 of the first stack 110 from the anode 102 and electrons are injected from the first charge generating layer 120. Accordingly, although a large amount of holes are supplied to the first organic emission layer 116, a relatively small amount of electrons are supplied, so that an imbalance occurs between the holes and the electrons, thereby decreasing the lifetime and the efficiency.

The thickness of the first charge generation layer 120 may be adjusted to increase the amount of electrons supplied to the first organic emission layer 116 to balance the distribution of holes and electrons in the first organic emission layer 116 x is made larger than the thickness y of the second charge generating layer 140 (x> y). That is, the thickness of the N-CGL1 122 of the first charge generation layer 120 is made larger than the thickness of the N-CGL2 142 of the second charge generation layer 140, thereby increasing the number of electrons by pumping To the first organic emission layer (116).

Table 1 and FIG. 4A are graphs each showing the relationship of the lifetime of the first organic emission layer 116 to the thickness of the P-CGL 124 of the first charge generation layer 120. FIG. At this time, the lifetime described in the tables and graphs is a relative value rather than an absolute value. That is, the lifetime of a conventional organic electroluminescent device is set to 100%, and the lifetime of a conventional organic electroluminescent device is shown depending on its thickness.

The thickness of P-CGL1 The lifetime of the first organic light emitting layer The lifetime of the second organic light emitting layer 75 Å 94% 89% 80 Å 100% 100% 90 Å 102% 114%

When the thickness of the P-CGL1 124 of the first charge generating layer 120 is 80 ANGSTROM, the lifetime of the first organic light emitting layer 116 and the second organic light emitting layer 134, as shown in Table 1 and FIG. 4A, Is equal to the lifetime of a general organic electroluminescent device currently used. The lifetime of the first organic light emitting layer 116 and the second organic light emitting layer 134 is reduced to about 94% and 89%, respectively, when the thickness of the P-CGL1 124 is reduced to 75 ANGSTROM, The lifetime of the first organic light emitting layer 116 and the second organic light emitting layer 134 increases to about 102% and 114%, respectively. Therefore, in the present invention, since the P-CGL1 124 of the first charge generation layer 120 is formed to have a thickness of 80 ANGSTROM or more, the lifetime of the organic electroluminescent device can be improved or at least equal to that of a general organic electroluminescent device do.

Of course, the P-CGL1 124 of the first charge generating layer 120 may have a thickness of 80 ANGSTROM or less. However, this is not preferable because the lifetime of the P-CGL1 124 is shorter than that of a conventional organic electroluminescent device.

Table 2 and FIG. 4B are tables and graphs respectively showing the relationship of the lifetime of the first organic emission layer 116 with respect to the thickness of the N-CGL 122 of the first charge generation layer 120.

The thickness of N-CGL1 The lifetime of the first organic light emitting layer The lifetime of the second organic light emitting layer 150 Å 56% 92% 170 Å 69% 95% 180 Å 100% 100% 190 Å 102% 108%

When the thickness of the N-CGL1 122 of the first charge generating layer 120 is 180 Å, the lifetime of the first organic light emitting layer 116 and the second organic light emitting layer 134, as shown in Tables 2 and 4B, Is equal to the lifetime of a general organic electroluminescent device currently used. The lifetime of the first organic light emitting layer 116 and the second organic light emitting layer 134 is greatly reduced to about 56% and 92%, respectively, when the thickness of the N-CGL1 122 is reduced to 150 ANGSTROM, Is reduced to 170 ANGSTROM, the lifetime of the first organic emission layer 116 and the second organic emission layer 134 is reduced to about 69% and 95%, respectively.

When the thickness of the N-CGL1 122 is increased to 190 ANGSTROM, the lifetime of the first organic emission layer 116 and the second organic emission layer 134 increases to about 102% and 108%, respectively.

Accordingly, in the present invention, the N-CGL1 122 of the first charge generation layer 120 is formed to have a thickness of 180 ANGSTROM or more, so that the lifetime of the organic electroluminescent device can be improved as compared with a general organic electroluminescent device.

Table 3 and FIG. 5 are a table showing the lifetime of the device with respect to the ratio (x: y) of the thickness x of the first charge generation layer 120 to the thickness y of the second charge generation layer 140, to be.

Thickness ratio (x: y) The lifetime of the first organic light emitting layer The number of the second organic light emitting layers 0.7: 1 70% 84% 0.9: 1 82% 97% 1: 1 100% 100% 1.1: 1 102% 112% 1.2: 1 93% 103%

When the ratio of the thickness x of the first charge generation layer 120 to the thickness y of the second charge generation layer 140 is 1: 1 as shown in Table 3 and FIG. 5, The lifetime of the first organic light emitting layer 116 and the second organic light emitting layer 134 is the same as the lifetime of a general organic electroluminescent device currently used.

When the ratio (x: y) of the thickness x of the first charge generating layer 120 to the thickness y of the second charge generating layer 140 is 0.7: 1, the first organic luminescent layer 116 and the 2 organic light emitting layer 134 is reduced to 70% and 84%, respectively. When the ratio (x: y) of the thickness x of the first charge generation layer 120 to the thickness y of the second charge generation layer 140 is 0.9: 1, the first organic emission layer 116 and / The lifetime of the second organic emission layer 134 is reduced to 82% and 97%, respectively.

On the other hand, when the ratio (x: y) of the thickness x of the first charge generation layer 120 to the thickness y of the second charge generation layer 140 is 1.1: 1, the first organic emission layer 116 and / The lifetime of the second organic light emitting layer 134 is increased to 102% and 112%, respectively. When the ratio (x: y) of the thickness (x) of the first charge generation layer 120 to the thickness y of the second charge generation layer 140 is 1.2: 1, The lifetime is reduced to 93%, but the lifetime of the second organic light emitting layer 134 is increased to 103%

Accordingly, in the present invention, when the ratio (x: y) of the thickness (x) of the first charge generating layer 120 to the thickness (y) of the second charge generating layer 140 is 1: 1 or less, The ratio (x: y) of the thickness x of the first charge generating layer 120 to the thickness y of the second charge generating layer 140 is 1.1: 1 or more, preferably 1.1: 1-1.2: 1 The lifetime can be extended as compared with a general organic electroluminescent device. Of course, the lifetime of the first organic emission layer 116 is reduced at a thickness ratio of 1.2: 1, but the lifetime of the second organic emission layer 134 is improved, so that the lifetime of the entire device can be improved.

As described above, in the present invention, the ratio (x: y) of the thickness (x) of the first charge generating layer 120 to the thickness (y) of the second charge generating layer 140 is set to 1.1: Emitting layer 116 or the second stack 110 of the first stack 110 by forming the first charge generating layer 120 to be thicker than the second charge generating layer 140 with a ratio of 1.1: The light emitting efficiency and the lifetime can be improved by making the amount of the electrons flowing into the second organic light emitting layer 134 of the light emitting layer 130 sufficiently.

The N-CGL1 122 and the P-CGL1 124 of the first charge generation layer 120 are 180 Å or more and 80 Å or more thick and the N-CGL1 122 and the P- The thickness (x) of the first charge generating layer 120 is preferably set to 400 Å or less.

While the present invention has been described with reference to a specific configuration in the foregoing detailed description, the present invention is not limited to this specific configuration. For example, although in the above description it is described that the organic luminescent layers of the first and third stacks are doped with a blue fluorescent material and the organic luminescent layer of the second stack is doped with a yellow-green phosphorescent material, The organic light emitting layer of the stack may be doped with a blue colorant and the organic light emitting layer of the second stack may be doped with a yellow-green fluorescent substance. Or the organic light emitting layer of the second stack may be doped with a red-green phosphorescent material or a red-green fluorescent material.

As long as the thickness of the first charge generation layer and the second charge generation layer, which are basic features of the present invention, can be adjusted, the present invention can be applied to all the known organic electroluminescent devices and display devices employing the same.

10, 50: substrate 17W, 17R, 17G, 17B: color filter layer
11W, 11R, 11G, 11B: gate electrodes 14W, 14R, 14G, 14B:
15W, 15R, 15G, 15B: drain electrode 23: organic light emitting portion
24, 26: insulating layer 25: common electrode
28: bank layers 64W, 64R, 64G, 64B: pixel electrodes
110, 130, 150 stack 120, 140: charge generation layer
122,142: N-CGL 124,144: P-CGL

Claims (17)

Anode and cathode;
First and second charge generation layers disposed on the anode;
A first stack disposed between the anode and the first charge generating layer;
A second stack disposed between the first charge generating layer and the second charge generating layer; And
And a third stack disposed between the second charge generation layer and the cathode,
Wherein the thickness (x) of the first charge generating layer is greater than the thickness (y) of the second charge generating layer. The method according to claim 1,
A first hole transport layer, a first organic emission layer, and a first electron transport layer included in the first stack;
A second hole transport layer, a second organic emission layer, and a second electron transport layer included in the second stack; And
And a third hole transport layer and a third organic emission layer included in the third stack. The organic electroluminescent device according to claim 2, wherein the first organic light emitting layer and the third organic light emitting layer are doped with a blue fluorescent material or a blue dopant composed of a blue organic material. The organic electroluminescent device according to claim 2, wherein the second organic emission layer is doped with a yellow-green fluorescent material or a yellow-green dopant comprising a yellow-green phosphorescent material. The organic electroluminescent device according to claim 1, wherein the first charge generation layer and the second charge generation layer include N-type and P-type, respectively. The organic electroluminescent device according to claim 5, wherein the N-type dopant of the first charge generation layer and the second charge generation layer comprises an alkali metal or an alkaline earth metal. 6. The organic electroluminescent device according to claim 5, wherein the N-type layer of the first charge generation layer has a thickness of 180 ANGSTROM or more and the P-type layer has a thickness of 80 ANGSTROM or more. The organic electroluminescent device according to claim 7, wherein the thickness of the first charge generation layer is 400 Å or less. The organic electroluminescent device according to claim 1, wherein the thickness ratio (x: y) of the first charge generation layer and the second charge generation layer is 1.1: 1 or more. 11. The organic electroluminescent device according to claim 9, wherein the thickness ratio (x: y) of the first charge generation layer and the second charge generation layer is 1.1: 1-1.2: 1. An organic light emitting display panel including a pixel electrode and a common electrode; And
Wherein the organic light emitting portion includes first and second charge generation layers disposed on the pixel electrode and disposed on the anode, and a second charge generation layer disposed between the pixel electrode and the first charge generation layer A second stack disposed between the first charge generation layer and the second charge generation layer, and a third stack disposed between the second charge generation layer and the common electrode, wherein the first charge generation layer Wherein the thickness (x) of the layer is greater than the thickness (y) of the second charge generation layer. [12] The organic light emitting display device of claim 11, wherein the pixel electrode is made of indium tin oxide (ITO) or indium zinc oxide (IZO). 12. The organic electroluminescent display device according to claim 11, wherein the common electrode is a material selected from the group consisting of Ca, Ba, Mg, Al and Ag. The organic light emitting display according to claim 11,
A first substrate and a second substrate;
A thin film transistor disposed in each pixel of the first substrate; And
Further comprising a color filter layer disposed in each pixel. 12. The organic electroluminescent display device according to claim 11, wherein the first charge generation layer and the second charge generation layer include N-type and P-type, respectively. 12. The organic electroluminescent display device according to claim 11, wherein the thickness ratio (x: y) of the first charge generation layer and the second charge generation layer is 1.1: 1 or more. 17. The organic electroluminescent display device according to claim 16, wherein the thickness ratio (x: y) of the first charge generation layer and the second charge generation layer is 1.1: 1-1.2: 1.

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