KR102295796B1 - Organic light emitting device and display device having thereof - Google Patents

Abstract

In the organic electroluminescent device according to the present invention, the first and second charge generating layers are disposed between the anode and the cathode, the first stack including the blue organic light emitting layer is disposed between the anode and the first charge generating layer, and the first charge generating layer is disposed. A second stack having a yellow-green organic light emitting layer is disposed between the layer and the second charge generating layer, and a third stack having a blue organic light emitting layer is disposed between the second charge generating layer and the cathode. A charge control layer is configured in the third electron transport layer of the third stack to control the amount of electrons flowing into the third organic light emitting layer and block the inflow of holes from the third electron transport layer from the third organic light emitting layer to the device lifespan and improve the luminous efficiency.

Description

Organic light emitting device and display device having the same

The present invention relates to an organic electroluminescent device, and more particularly, to an organic electroluminescent device having improved luminous efficiency and improved lifespan, and a display device having the same.

The organic electroluminescent device is a device that converts electric energy into light by applying an electric field to an organic material. Research on these organic light emitting devices has been mainly focused on technologies for realizing blue, green, and red display devices. applied.

However, currently, research on the possibility of a white organic light emitting device utilizing the characteristics of organic materials including various colors and a wide range of visible regions has been recognized and research is being conducted. Such a white organic light emitting device is recognized as a major device because its application fields such as lighting, backlight, and display devices are wide.

The development of such a white organic light emitting diode is mainly focused on high efficiency, life extension, color purity improvement, color stability according to changes in current and voltage, and ease of manufacture, and research and development are in progress according to each method. The structure of the white organic light emitting display device can be largely divided into a single layer light emitting structure, a multilayer structure, and a down conversion structure.

The single layer light emitting structure is a structure that emits mixed light within a single layer using R, G, B or complementary color relationship. . The down-conversion structure uses blue light emission and uses color conversion through a red phosphor to realize white color, and although the structure is simple, the efficiency is low.

The multilayer light emitting layer structure is a tandem structure including a blue fluorescent light emitting layer and a yellow-green phosphorescent light emitting layer, and has an advantage in that it has a long lifespan. However, the white organic light emitting diode of such a tandem structure has a problem in that the driving voltage is high and the efficiency is low. In addition, since the light emitting region is not formed in the light emitting layer, there is a problem in that device efficiency and lifespan are lowered.

An object of the present invention is to solve the above problems, and an object of the present invention is to provide an organic electroluminescent device having improved luminous efficiency and lifespan.

Another object of the present invention is to provide an organic electroluminescent display device including the organic electroluminescent device.

In order to achieve the above object, the organic electroluminescent device according to the present invention has a first stack having first and second charge generating layers disposed between the anode and the cathode and having a blue organic light emitting layer between the anode and the first charge generating layer. is disposed, a second stack having a yellow-green organic light emitting layer is disposed between the first charge generating layer and the second charge generating layer, and a third stack having a blue organic light emitting layer between the second charge generating layer and the cathode are placed

A charge control layer is configured in the third electron transport layer of the third stack to control the amount of electrons flowing into the third organic light emitting layer and block the inflow of holes from the third electron transport layer from the third organic light emitting layer. Therefore, by preventing an excessive amount of electrons from flowing into the third organic light emitting layer and holes from flowing into the third electron transporting layer, lifespan is improved, and excitons due to the combination of holes and electrons are reduced by controlling the amount of holes and electrons to be combined. 3 It is possible to improve the luminous efficiency by generating in the organic light emitting layer.

In this case, the blue dopant is a blue phosphor material or a blue phosphor material, and is doped at the boundary between the third organic light emitting layer and the third electron transport layer.

The third electron transport layer is an electron transport material having an energy level of HOMO of about -5.6 to -6.6 eV, LUMO of -2.1 to -3.1 eV, and electron mobility of 1×10 ⁻⁴ ∼ 1×10 ⁻⁶ HOMO is about -5.5 to -6.5 eV, LUMO has an energy level of -2.5 to -3.5 eV, and may be composed of an electron transport material having an ^{electron mobility of 1×10 -3 to} 1×10 ^-5, It may be composed of a mixture of In addition, the thickness of the charge control layer is 10-50 Å.

In addition, in the organic light emitting display device, a color filter layer and the organic light emitting device having the above structure are provided in a pixel including W, R, G, and B pixels, so that white light emitted from the organic light emitting device passes through the color filter layer to provide color to implement

In the present invention, by configuring the charge control layer in the electron transport layer, the amount of electrons flowing into the organic light emitting layer is controlled and holes are prevented from flowing into the third electron transport layer, and the supply of an excessive amount of electrons and penetration of holes It is possible to prevent device deterioration, thereby improving the lifespan of the device.

In addition, in the present invention, by controlling the amount of electrons and holes flowing into the organic light emitting layer so that both holes and electrons are combined in the organic light emitting layer, the luminous efficiency of the organic light emitting device can be improved.

1 is a cross-sectional view showing the structure of an organic light emitting display device according to the present invention.
2 is a diagram schematically showing the 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.
4 is a view showing the structure of a third electron transport layer of the organic electroluminescent device according to the present invention.
FIG. 5 is a graph showing the results of luminance versus time of an organic electroluminescent device having a charge control layer on a sperm transport layer and an organic electroluminescent device not having a charge control layer.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

The shapes, sizes, proportions, angles, numbers, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and thus the present invention is not limited to the illustrated matters. Like reference numerals refer to like elements throughout. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the case in which the plural is included is included unless otherwise explicitly stated.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship of two parts is described as 'on', 'on', 'on', 'beside', etc., 'right' Alternatively, one or more other parts may be positioned between the two parts unless 'directly' is used.

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal relationship is described with 'after', 'following', 'after', 'before', etc. It may include cases that are not continuous unless this is used.

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

Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship. may be

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

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

As shown in FIG. 1 , the organic light emitting display device according to the present embodiment includes a W pixel emitting white light, an R pixel emitting red light, a G pixel emitting green light, and a B pixel emitting 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 unit as light of a specific color. is output as is.

As described above, in the present invention, it is possible to improve the overall luminance of the organic light emitting display device by outputting white light including the W pixel. However, in the present invention, the W pixel is not provided and may be formed only of the R, G, and B pixels.

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

The driving thin film transistor includes gate electrodes 11W, 11R, 11G, and 11B respectively formed in the W, R, G, and B pixels on the first substrate 10 and the gate electrodes 11W, 11R, 11G, and 11B. A semiconductor layer (12W, 12R, 12G, 12B) formed over the entire formed first substrate 10, and source electrodes (14W, 14R, 14G, 14B) formed on the semiconductor layer (12W, 12R, 12G, 12B), and and drain electrodes 15W, 15R, 15G, and 15B. Although not shown in the drawing, an etching stopper is formed on a portion of the upper surface of the semiconductor layers 12W, 12R, 12G, and 12B to form the source electrodes 14W, 14R, 14G, and 14B and the drain electrodes 15W, 15R, 15G, and 15B. It is also possible to prevent the semiconductor layers 12W, 12R, 12G, and 12B from being etched during the etching process.

Although not shown in the drawing, a gate line is formed on the first substrate 10 at the same time as the gate electrodes 11W, 11R, 11G, and 11B are formed.

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, and the gate insulating layer 22 may be formed of SiO ₂ or SiNx. It may be a single layer made of an inorganic insulating material or a double layer made of _{SiO 2 and SiNx.} The semiconductor layers 12W, 12R, 12G, and 12B are formed of an amorphous semiconductor material such as amorphous silicon or a polycrystalline semiconductor material. In addition, the semiconductor layers 12W, 12R, 12G, and 12B may be formed of an oxide semiconductor such as indium gallium zinc oxide (IGZO). 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 not shown in the drawing, a data line is formed on the gate insulating layer 22 at the same time as the source electrodes 14W, 14R, 14G, 14B and the drain electrodes 15W, 15R, 15G, and 15B are formed, so that the gate line together with W, R, G, and B pixels

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 respectively formed in the R, G, and B pixels of the first insulating layer 24 . In this case, the color filter layer is not formed in the W pixel.

As a signal is applied to the gate electrodes 11W, 11R, 11G, and 11B, the semiconductor layers 12W, 12R, 12G, and 12B are activated to activate the source electrodes 14W, 14R, 14G, and 14B and the drain electrode 15W. A channel layer is formed in the semiconductor layers 12W, 12R, 12G, and 12B between , 15R, 15G, and 15B.

Meanwhile, in the above detailed 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 the gate electrodes 11W, 11R, 11G, and 11B. ) formed on the bottom gate (bottom gate) type thin film transistor is exemplified, but the present invention is not limited to the thin film transistor of such a specific structure.

For example, a top gate type thin film transistor in which semiconductor layers 12W, 12R, 12G, and 12B are formed on the first substrate 10 and gate electrodes 11W, 11R, 11G, and 11B are formed thereon. will also be applicable.

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 laminated with an organic insulating material such as photo-acryl.

Pixel electrodes 64W, 64R, 64G, and 64B are respectively formed in the W, R, G, and B pixels on the second insulating layer 26 . At this time, contact holes ( 29) is formed, and pixel electrodes 64W, 64R, 64G, and 64B are formed in the contact hole 29 and are electrically connected to the exposed drain electrodes 15W, 15R, 15G, and 15B of the driving thin film transistor, respectively. . 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 type of barrier rib, which divides each pixel and prevents light of a specific color output from adjacent pixels from being mixed and output. In addition, since the bank layer 28 fills a part of the contact hole 29, the step difference is reduced. deterioration can be prevented.

The organic light emitting part 23 is formed over the entire first substrate 16 on the pixel electrodes 64W, 64R, 64G, and 64B and the bank layer 28 . The organic light emitting unit 23 includes a white organic light emitting layer emitting white light.

The white organic light emitting layer has a tandem structure including a blue light emitting layer and a yellow-green light emitting layer, and an electron injection layer and a hole injection layer for injecting electrons and holes into the organic light emitting layer as well as the light emitting layer, respectively, and injected electrons and holes The organic light emitting layer may include an electron transport layer and a hole transport layer, respectively, and a charge generation layer for generating charges such as electrons and holes.

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

The organic light emitting part 23, the common electrode 25, and the pixel electrodes 64W, 64R, 64G, and 64B form an organic light emitting diode. At this time, the common electrode 25 is a cathode of the organic light emitting device, and the pixel electrodes 64W, 64R, 64G, and 64B are an anode, and the common electrode 25 and the pixel electrodes 64W, 64R, When a voltage is applied to 64G and 64B, electrons from the common electrode 25 are injected into the organic light emitting part 23 and holes are injected into the organic light emitting part 23 from the pixel electrodes 64W, 64R, 64G, and 64B. When injected, excitons are generated in the organic light emitting layer, and as these excitons decay, light corresponding to the energy difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of the light emitting layer is generated. As a result, it diverges to the outside (toward the first substrate 10 in the drawing). At this time, white light is emitted from the organic light emitting layer, and while the white light passes through the R, G, and B-color filter layers 17R, 17G, and 17B, only light of a color corresponding to the pixel is output.

At this time, white light is output from the W pixel. Since this white light does not pass through the color filter layer, the luminance is higher than that of the light transmitted through the color filter layers 17R, 17G, and 17B. It is possible to improve the luminance of

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

As the adhesive, any material can be used as long as it has good adhesion and good heat resistance and water resistance, but in the present invention, thermosetting resins such as epoxy compounds, acrylate compounds, or acrylic rubbers are mainly used. use At this time, the adhesive layer 42 is applied to a thickness of about 5-100 μm, and is cured at a temperature of about 80-170 degrees. The adhesive layer 42 not only bonds the first substrate 10 and the second substrate 50 together, but also serves as an encapsulant for preventing moisture from penetrating into the organic light emitting display device. Accordingly, in the detailed description of the present invention, the term of reference numeral 42 is expressed as an adhesive, but this is for convenience, and this adhesive layer may be expressed as an encapsulant.

The second substrate 50 may be made of glass or plastic. In addition, the second substrate 50 may be formed of 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 showing the structure of an organic light emitting device applied to the organic light emitting display device according to the present invention.

As shown in FIG. 2 , the organic light emitting diode includes an anode 102 and a cathode 104 , and first to 3 stacks 110 , 130 and 150 are stacked between the anode 102 and the cathode 104 . and between each of the stacks 110 , 130 , and 150 , respectively, charge generation layers 120 and 140 are disposed. Hereinafter, although described, each of the stacks 110 , 130 , and 150 includes a plurality of layers including an organic light emitting layer, wherein the first stack 110 and the third stack 150 include a blue organic light emitting layer that emits blue light, and the second The two stacks 130 include yellow-green organic light-emitting layers emitting yellow-green light.

The blue organic light emitting layer of the first stack 110 and the third stack 150 is doped with a blue fluorescent material to emit blue light, and the yellow-green light organic light emitting layer of the second stack 130 is doped with yellow and green phosphors. It emits yellow-green light.

As described above, in the present invention, the organic electroluminescent device is formed in a plurality of stacked structures for the following reasons.

First, by forming the organic light emitting device in a plurality of stacked structures, the luminous efficiency of the organic light emitting device can be improved. In an organic electroluminescent device having a stacked structure, both fluorescence and phosphorescence can be emitted by controlling the recombination regions of holes and electrons to be formed in both the fluorescent layer and the phosphorescent layer. Therefore, the luminous efficiency is improved compared to the single-layer structure.

Second, by forming the organic light emitting device in a plurality of stacked structures, the lifespan of the organic light emitting device can be extended. When emitting white light of the same luminance as that of a single-layer structure in an organic electroluminescent device having a stacked structure, the luminance of white light emitted from each layer of the stacked structure can be reduced by the number of stacked layers, so that the lifetime is proportional to the number of stacked layers. can be extended.

Third, as the organic light emitting device is formed in a plurality of stacked structures, the driving voltage of the organic light emitting device can be reduced. In an organic light emitting diode having a stacked structure, since a charge generating layer is provided between each stack, driving power can be reduced compared to an organic light emitting diode that emits white light of the same luminance.

Since the first charge generating layer (CGL1; 120) and the second charge generating layer (CGL2; 140) play a charge balance control role between the stacks 110, 130, and 150 adjacent to each other, it is also referred to as an intermediate connector layer. . Also, the first charge generating layer CGL1 120 and the second charge generating layer CGL2 140 generate holes and electrons, respectively, and inject them into the 1-3 stacks 110 , 130 , and 150 . Although not shown in the drawings, the first charge generating layer (CGL1; 120) and the second charge generating layer (CGL2; 140) are composed of an electron generating layer and a hole generating layer for injecting electrons, respectively, and the 1-3 stacks 110, 130, and 150 ) to inject electrons and holes, respectively.

The electron generating layer may be made of an organic material layer doped with an alkali metal material having good electron injection characteristics, and the hole generating layer may be made of an organic semiconductor layer including a P-type organic material. The layer and the hole-generating layer are not limited to these specific materials.

3 is a view showing one structure of an organic light emitting diode in which the structures of the 1-3 stacks 110 , 130 , and 150 are specifically illustrated.

As shown in FIG. 3 , the first stack 110 of the organic light emitting diode according to the present invention is disposed between the anode 102 and the first charge generation layer 120 . The first stack 110 includes a hole injection layer 112 formed on the anode 102, a first hole transport layer formed on the hole injection layer 112 to transport the injected holes; 114), a first organic light-emitting layer (Emitting Layer; 116) disposed on the first hole transport layer 114, and a first electron transport layer (Electron Transporting Layer; 118) disposed on the first organic light-emitting 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 light emitting layer 116 . At least one of the hole injection layer 112 , the first hole transport layer 114 , and the first electron transport layer 118 may be omitted depending on the structure or characteristics of the device, or another layer may be further configured. It is not limited.

In general, it is known that holes are generally higher than electrons due to reasons such as ionization potential and electron affinity in carrier mobility in an organic material. That is, since electrons do not easily move in the organic material, excitons are generated near the electrode, but the quantum efficiency of the organic light emitting device is lowered because non-luminous extinction is large near the electrode. Therefore, in order to improve the efficiency of the device, electrons and holes are sufficiently injected into the organic light emitting layer, and the injected electrons and holes must be balanced. An ideal light emitting device should match 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 and the HOMO and LUMO levels of the light emitting material, the structure of the light emitting device is formed as a heterostructure using two or more organic materials with different band gaps. In order to form a heterojunction structure, a first hole injection layer 112 as a charge injection layer, a first hole transport layer 114 as a charge transport layer, and a first electron transport layer 118 are provided.

Since the first hole transport layer 114 is made of an organic material and the anode 102 is made of inorganic ITO, the interface characteristics between the first hole transport layer 114 and the anode 102 are poor due to the difference between the inorganic material and the organic material, As a result, holes are not smoothly injected from the anode 102 to the first hole transport layer 114 . The hole injection layer 112 improves the interface characteristics by reducing the surface energy difference between the first hole transport layer 114 and the anode 102 , and the work function level of the hole injection layer 112 is adjusted to the work function level of the anode 102 . The energy difference between the work function level of the anode 102 and the HOMO level of the first hole transport layer 114 is reduced by setting it to the middle of the function level and the HOMO level of the first hole transport layer 114 . As such, by improving the interface characteristics between the first hole transport layer 114 and the anode 102 and reducing the energy difference between the work function level of the anode 102 and the HOMO level of the first hole transport layer 114, Holes are smoothly injected from the anode 102 to the first hole transport layer 114 .

The first hole transport layer 114 and the first electron transport layer 118 adjust the hole and electron bonding region by controlling 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 greater than that of holes. , increase the luminous efficiency by allowing electrons to quickly enter within the collision radius where they can recombine with holes.

As the hole injection material for forming the hole injection layer 112, an organic material such as the following Chemical Formula 1 is used, but the hole injection material of the present invention is not limited to this specific organic material.

In addition, as the hole transport material forming the first hole transport layer 114, an organic material such as the following Chemical Formula 2 is used, but the hole transport material of the present invention is not limited to this specific organic material.

In addition, as the electron transport material forming the first electron transport layer 118, an organic material such as the following Chemical Formula 3 is used, but the electron transport material of the present invention is not limited to this specific organic material.

Although not shown in the drawings, an electron blocking layer may be formed between the first hole transport layer 114 and the first organic light emitting layer 116 , and a hole between the first organic light emitting layer 116 and the first electron transport layer 118 . A blocking layer may be constructed. The electron-blocking layer does not flow electrons from the first organic light-emitting layer 116 to the first hole transport layer 114 and traps electrons 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 a dopant of a blue fluorescent material is included in one host to emit blue light.

The host and the dopant of the first organic light emitting layer 116 use organic materials represented by the following Chemical Formulas 4 and 5, respectively, but the material of the present invention is not limited to these specific organic materials.

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

As described above, the second hole transport layer 132 and the second electron transport layer 134 are provided to improve the luminous efficiency of the second organic light emitting layer 134 . At least one of the second hole transport layer 132 and the second electron transport layer 134 may be omitted depending on the structure or characteristics of the device, or another layer may be further configured, but is not limited thereto.

The second organic light emitting layer 134 of the second stack 130 is composed of one host, a yellow phosphor and a green phosphor doped with the host, and yellow-green light is emitted.

Although not shown in the drawings, an electron blocking layer may be formed between the second hole transport layer 132 and the second organic light emitting layer 134 . As described above, since the energy level of the second hole transport layer 132 is higher than the energy level of the excited state of the triplet excitons of the second organic light emitting layer 134 , the triplet excitons of the second organic light emitting layer 134 are second Although the possibility of inflow into the hole transport layer 132 is small, in the present invention, by configuring a hole blocking layer, electrons and holes are not combined in the second organic light emitting layer 134 and by preventing the inflow into the second hole transport layer 132 . It is possible to prevent a decrease in luminous efficiency. Similarly, a hole blocking layer may be formed between the second organic light emitting layer 134 and the second electron transport 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 light emitting layer (EML3; 154) disposed on the third hole transport layer 152, and the It includes a third electron transport layer (ETL3) 156 disposed on the third organic light emitting 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 dopant of a blue fluorescent material is included in one host to emit blue light. In this case, the host and the dopant may be made of the same material as the first organic light emitting layer 154 (ie, the materials described in Chemical Formulas 4 and 5 are used).

The electron injection layer 158 improves the interface characteristics by reducing the difference in surface energy between the third electron transport layer 156 and the cathode 104 , and sets the work function level of the electron injection layer 158 to that of the cathode 104 . The energy difference between the work function level of the cathode 104 and the LUMO level of the third electron transport layer 156 is reduced by setting it to the middle of the function level and the LUMO level of the third electron transport layer 156 . As such, by improving the interface characteristics between the third electron transport layer 156 and the cathode 104 and reducing the energy difference between the work function level of the cathode 104 and the LUMO level of the third electron transport layer 156, Electrons are smoothly injected from the cathode 102 to the third electron transport layer 156 .

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 . In addition, although not shown in the drawings, an electron blocking layer may be formed between the third hole transport layer 152 and the third organic light emitting layer 154 , and between the third organic light emitting layer 154 and the third electron transport layer 156 . The hole blocking layer may be configured. 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 or characteristics of the device, or another layer may be further configured, and must be The present invention is not limited thereto.

As described above, in the organic light emitting diode of the present invention, blue light is emitted from the first stack 110 and the third stack 150 and yellow-green light is emitted from the second stack 130, and these lights are mixed to form a lower portion. It is output as white light through the direction.

Each of 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 includes a dopant of a blue fluorescent material in one host to emit blue light. On the other hand, the second organic light emitting layer of the second stack 130 contains a dopant of a yellow-green phosphorescent material in one host so that yellow-green light is emitted. The reason for doping phosphorescent material is as follows.

Fluorescent materials have excellent device stability, but have limitations in obtaining high efficiency. On the other hand, although phosphor materials can achieve high efficiency, there is no material capable of emitting stable blue light. In order to complement the advantages and disadvantages of such a fluorescent material and a phosphorescent material, a hybrid structure including a fluorescent light emitting layer and a phosphorescent light emitting layer is used in the present invention. , it is possible to maximize the luminous efficiency while emitting stable blue light.

However, the present invention is not limited to a structure in which the blue light emitting layer is doped with a fluorescent material and the yellow-green light emitting layer is doped with a phosphor, but the blue light emitting layer is doped with a phosphor and the yellow-green light emitting layer is doped with a fluorescent material.

Meanwhile, the third electron transport layer 156 of the third stack 150 is doped with a blue fluorescent material to form a charge control layer 157 inside the third electron transport layer 156 . As the charge control layer 157 is formed on the third electron transport layer 156, the amount of electrons injected from the cathode 104 to the third electron transport layer 156 is controlled to prevent an excessive amount of electrons from being injected. . In addition, the charge control layer 157 blocks holes flowing into the third electron transport layer 156 from the third organic light emitting layer 154 . As described above, the charge control layer 157 doped with the blue dopant controls the injection of electrons and holes flowing into the third electron transport layer 156 so that an excessive amount of electrons from the cathode 104 is removed from the third organic light emitting layer 154 . ) to prevent the deterioration of the third organic light emitting layer 154 and at the same time block the inflow of holes from the third organic light emitting layer 154 to the third electron transport layer 156, so that the third electron transport layer 156 is formed. deterioration can be prevented.

In addition, the charge control layer 157 controls the injection of electrons and holes flowing into the third electron transport layer 156 so that excitons due to the combination of holes and electrons are generated in the third organic light emitting layer 154 . The luminous efficiency of the organic light emitting layer 154 is improved.

The third electron transport layer 156 may be composed of two or more layers. Alternatively, the third electron transport layer 156 may be configured as a single layer by co-depositing at least two layers. The first electron transport material of the third electron transport layer 156 injects smooth electrons into the host of the third organic light emitting layer 154 and the holes diffused from the third organic light emitting layer 154 to the third electron transport layer 156 It can be made of materials that prevent it. For example, the first electron transport material has a HOMO of about -5.6 to -6.6 eV, an energy level of LUMO of -2.1 to -3.1 eV, and an electron mobility of 1×10 ^{-4 to} 1×10 ^-6 It can be composed of phosphorus material. In addition, the second electron transport material of the third electron transport layer 156 may be made of a material having smooth electron injection and high electron mobility from the cathode 104 . For example, the second electron transport material has a HOMO of about -5.5 to -6.5 eV, an energy level of LUMO of -2.5 to -3.5 eV, and an electron mobility of 1×10 ^{-3 to} 1×10 ^-5 It may be composed of a phosphorus second electron transport material. Accordingly, the third electron transport layer 156 may be configured as a single layer by co-depositing the first electron transport material and the second electron transport material. For example, in the present invention, the first electron transport material and the second electron transport material may be mixed in a ratio of 30:70-50:50 or 70:30-50:50. Of course, the third electron transport layer 156 may be formed by mixing three or more electron transport materials. Of course, the first and second electron transport materials are not limited to specific organic materials, and various organic materials satisfying the characteristics of HOMO, LUMO, and electron mobility described above may be used.

Accordingly, in the present invention, after the third electron transport layer 156 is made of a single material, the third electron transport layer 156 of a single material may be doped with a blue dopant to form the charge control layer 157 . The doping of the blue dopant is performed by depositing the blue dopant simultaneously with the deposition of the first electron transport material or the second electron transport material.

After the third electron transport layer 156 is formed of a plurality of materials, the charge control layer 157 may be formed by doping with a blue dopant. The blue dopant may be made of a material having a wavelength of 420 nm to 480 nm.

When the electron transport layer is formed of a plurality of materials, the charge control layer 157 may be formed by co-deposition of the plurality of electron transport materials. Accordingly, a blue dopant is formed between the first electron transport material and the second electron transport material of the third electron transport layer 156 to constitute the charge control layer 157 .

4 is a view showing the structure of the third electron transport layer 156 in which the charge control layer 157 is configured.

As shown in FIG. 4 , the third electron transport layer 156 is formed to have a width of about a, and a blue dopant is doped therein to form a charge control layer 157 . The charge control layer 157 is formed at the interface between the third electron transport layer 156 and the third organic light emitting layer 154, and the thickness (a) of the third electron transport layer 156 may be 600 Å or less. , preferably 400-550 Å. In addition, the thickness (b) of the charge control layer 157 doped with the blue dopant is formed to a thickness of about 10-50 Å, in this case, the doping ratio of the blue dopant is 0.5-8 wt% with respect to the third electron transport layer 156. . The blue dopant may be made of a material having a wavelength of 420 nm to 480 nm.

In the drawings, the charge control layer 157 is described as a layer disposed in the third electron transport layer 156 because the same material as the third electron transport layer 156 is doped with a blue dopant. This doping of the blue dopant is carried out by a separate process after the third electron transport layer 156 is formed. This may be achieved by injection or by simultaneously depositing an electron transport material and a blue dopant.

In this regard, in the above description, the charge control layer 157 is described as being disposed in the third electron transport layer 156 , but the charge control layer 157 is separate from the third electron transport layer 156 . It may consist of layers.

In addition, although it is illustrated that the first electron transport material or the second electron transport material of the third electron transport layer 156 and the blue dopant are formed in the drawings, the present invention is not limited thereto. As described above, when the first electron transport material and the second electron transport material of the third electron transport layer 156 are formed together, the blue dopant may be formed between the first electron transport material and the second electron transport material. can In this case, the first electron transport material and the second electron transport material may be mixed in a ratio of 30:70-50:50. Alternatively, the first electron transport material and the second electron transport material may be mixed in a ratio of 70:30-50:50. In addition, the thickness of the third electron transport layer 156 may be 600 Å or less, preferably 400-550 Å. The blue dopant has a thickness of about 10-50 Å, and the doping ratio of the blue dopant is 0.5-8 wt% with respect to the third electron transport layer 156 . The blue dopant may be made of a material having a wavelength of 420 nm to 480 nm.

As described above, in the present invention, a blue dopant is doped into the third electron transport layer 156 to control the inflow of holes and electrons injected into the third organic light emitting layer 154, so that the combination of holes and electrons is achieved through the third organic light emitting layer ( 154), the luminous efficiency of the organic light emitting diode can be improved, and the lifespan can be improved.

On the other hand, Table 1 is a table showing the comparison of the characteristics of the organic electroluminescent device having a structure in which the charge control layer is formed on the third electron transport layer and the organic electroluminescent device in which the charge control layer is not formed (Comparative Example) as in the present invention.

V Im/W cd/m2 EQE CIEx CIEy comparative example 11.6 23.5 8726.8 43.4 0.282 0.307 Example 11.7 23.5 8740.2 43.6 0.282 0.308

As shown in Table 1, in the case of the organic electroluminescent device (Comparative Example) in which the charge control layer is not configured in the third electron transport layer, the driving voltage (V) is 11.6 V, whereas the charge control layer in the third electron transport layer is 11.6 V In the case of the configured organic electroluminescent device (Example) according to the present invention, the driving voltage is 11.7V, which is almost similar to the driving voltage in the organic electroluminescent device of Comparative Example and the organic electroluminescent device of Example. In addition, the luminance (Im/W) of the comparative example and the example is also the same as 23.5 Im/W.

In the case of luminous efficiency (cd/m ² ), the organic electroluminescent device of the comparative example is 8726.8cd/m ² and the organic electroluminescent device of the example is 8740.2 cd/m ² , and the organic electroluminescent device of the example is the organic electroluminescence of the comparative example. The luminous efficiency is improved compared to the device.

In addition, the external luminous efficiency (EQE) is 43.4 and 43.6, respectively, which is slightly improved in the organic electroluminescent device of the embodiment, and the color coordinates (CIE) are almost the same.

In other words, when comparing the organic electroluminescent device in which the charge control layer is not formed in the third electron transport layer and the organic electroluminescent device in the present invention in which the charge control layer is configured in the third electron transport layer, other characteristics are almost similar, but the present invention The luminous efficiency of the organic electroluminescent device is improved.

FIG. 5 is a graph showing results of luminance versus time of an organic electroluminescent device having a charge control layer configured on an electron transport layer and an organic electroluminescent device not configured with a charge control layer.

As shown in FIG. 5 , the luminance of both the organic electroluminescent device including the charge control layer on the electron transport layer and the organic electroluminescent device without the charge control layer decreases over time. However, the luminance of the organic electroluminescent device in which the charge control layer is not formed is lower than in the organic electroluminescent device in which the configuration control layer is formed.

The luminance is lowered with time, and when the luminance is lowered to more than a threshold value, the organic light emitting diode cannot be used. That is, the decrease in luminance with time means a decrease in the lifespan of the organic light emitting diode. Therefore, the fact that the luminance of the organic EL device without the charge control layer is smaller than the luminance of the organic EL device with the charge control layer is lower than that of the organic EL device without the charge control layer. This means that the lifetime of the electroluminescent device is longer.

As described above, in the present invention, as the third electron transport layer is doped with a blue dopant as the charge control layer, the lifespan can be improved while maintaining the same characteristics as the organic electroluminescent device not doped with the blue dopant.

Although the above detailed description describes the configuration of the present invention as a specific configuration, the present invention is not limited to this specific configuration. For example, in the above description, it is described that the organic light emitting layer of the first stack and the third stack is doped with a blue fluorescent material and the organic light emitting layer of the second stack is doped with a yellow-green phosphor, but the first stack and the third stack are doped with a yellow-green phosphor. The organic light emitting layer of the stack may be doped with a blue phosphor, and the organic light emitting layer of the second stack may be doped with a yellow-green phosphor.

If a blue light emitting material is doped into the electron transport layer of the third stack, which is a basic feature of the present invention, it will be applicable to organic light emitting devices of all known structures and display devices employing the same.

10, 50: substrate 17W, 17R, 17G, 17B: color filter layer
11W, 11R, 11G, 11B: gate electrode 14W, 14R, 14G, 14B: source electrode
15W, 15R, 15G, 15B: drain electrode 23: organic light emitting part
24,26: insulating layer 25: common electrode
28: bank layer 64W, 64R, 64G, 64B: pixel electrode
110,130,150: stack 120,140: charge generation layer

Claims (23)

positive and negative electrodes;
first and second charge generating layers disposed on the anode;
a first stack disposed between the anode and the first charge generating layer and including a first organic light emitting layer doped with a first blue dopant;
a second stack disposed between the first charge generating layer and the second charge generating layer and including a second organic light emitting layer doped with yellow-green dopants;
a third stack disposed between the second charge generating layer and the cathode and including a third organic light emitting layer doped with the first blue dopant and a third electron transport layer; and
and a charge control layer disposed in the third stack,
The charge control layer is an organic electroluminescent device, characterized in that formed by doping a second blue dopant inside the third electron transport layer. According to claim 1,
a first hole transport layer and a first electron transport layer included in the first stack;
a second hole transport layer and a second electron transport layer included in the second stack; and
The organic electroluminescent device, characterized in that it further comprises a third hole transport layer included in the third stack. The organic electroluminescent device according to claim 1, wherein the first blue dopant is made of a blue fluorescent material or a blue phosphorescent material. The organic electroluminescent device according to claim 1, wherein the yellow-green dopant is made of a yellow-green fluorescent material or a yellow-green phosphorescent material. delete delete The organic electroluminescent device according to claim 1, wherein the charge control layer is disposed at a boundary of the third electron transport layer. delete According to claim 1, wherein the third electron transport layer has an energy level of HOMO of -5.6 to -6.6 eV, LUMO of -2.1 to -3.1 eV, and electron mobility of 1×10 ^{-4 to} 1×10 ^-6 An organic electroluminescent device comprising a phosphorus first electron transport material. According to claim 1, wherein the third electron transport layer has an energy level of HOMO of -5.5 to -6.5 eV, LUMO of -2.5 to -3.5 eV, and electron mobility of 1×10 ^{-3 to} 1×10 ^-5 An organic electroluminescent device comprising a phosphorus second electron transport material. According to claim 1, wherein the third electron transport layer,
a first electron transporting material having an HOMO of -5.6 to -6.6 eV, an LUMO of -2.1 to -3.1 eV, and an electron mobility of 1×10 ^{-4 to} 1×10 ^-6; and
HOMO is -5.5 to -6.5 eV, LUMO has an energy level of -2.5 to -3.5 eV, and an electron mobility of 1×10 ^{-3 to} 1×10 ^-5 is characterized in that it contains a second electron transport material. organic electroluminescent device. The organic electroluminescent device according to claim 11, wherein a mixing ratio of the first electron transport material and the second electron transport material is 30:70-50:50 or 70:30-50:50. The organic electroluminescent device according to claim 11, wherein the charge control layer is disposed between the first electron transport material and the second electron transport material. The organic electroluminescent device according to claim 1, wherein the second blue dopant is a blue fluorescent material or a blue phosphorescent material. The organic electroluminescent device according to claim 1, wherein a doping ratio of the second blue dopant is 0.5-8 wt% with respect to the third electron transport layer. The organic electroluminescent device according to claim 1, wherein the thickness of the third electron transport layer is 600 Å or less. The organic electroluminescent device according to claim 16, wherein the thickness of the third electron transport layer is 400-550 Å. The organic electroluminescent device according to claim 16, wherein the charge control layer has a thickness of 10-50 Å. an organic light emitting display panel including a pixel electrode and a common electrode; and
Consists of an organic light emitting unit disposed inside the organic light emitting display panel,
The organic light emitting unit includes first and second charge generating layers disposed on the pixel electrode, a first organic light emitting layer disposed between the pixel electrode and the first charge generating layer and doped with a first blue dopant, and holes in the first organic light emitting layer. a first stack including a first hole transport layer for transporting , a third stack disposed between the second charge generating layer and the common electrode and comprising a third organic light emitting layer doped with a first blue dopant and a third electron transport layer, and a charge control layer disposed within the third electron transport layer. is composed,
and the charge control layer is formed by doping a second blue dopant inside the third electron transport layer. The organic light emitting display device of claim 19, wherein the pixel electrode is made of indium tin oxide (ITO) or indium zinc oxide (IZO). The organic light emitting display device according to claim 19, wherein the common electrode is made of a material selected from a group consisting of Ca, Ba, Mg, Al, and Ag. 20. The method of claim 19, wherein the organic light emitting display panel comprises:
a first substrate and a second substrate;
a thin film transistor disposed on each pixel of the first substrate; and
The organic light emitting display device, characterized in that it further comprises a color filter layer disposed on each pixel. The organic light emitting display device of claim 19 , wherein the second blue dopant is a blue phosphor material or a blue phosphor material.

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