KR101730555B1 - Organic light emitting diode and organic light emitting display device having the same, and method of fabricating the same - Google Patents

Abstract

The organic light emitting diode of the present invention, the organic light emitting display having the organic light emitting diode, and the method of manufacturing the organic light emitting diode are characterized in that, in the organic light emitting diode manufactured using the soluble process, To thereby form a multilayered light emitting material layer.
According to the present invention, as the electron transport increases, the efficiency and lifetime are improved, and the electron injection layer and the electron transport layer to which the deposition process is applied can be removed, thereby ensuring the processability.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting diode (OLED), an organic light emitting diode (OLED) display having the organic light emitting diode, a method of manufacturing the organic light emitting diode,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode and an organic light emitting display having the organic light emitting diode. More particularly, the present invention relates to an organic light emitting diode manufactured using a soluble process, To a method of manufacturing a diode.

In recent years, there has been a growing interest in information display and a demand for a portable information medium has increased, and a lightweight flat panel display (FPD) that replaces a cathode ray tube (CRT) And research and commercialization are being carried out.

In the field of flat panel displays, a liquid crystal display device (LCD), which is light and consumes less power, has attracted the greatest attention, but a liquid crystal display device is not a light emitting device but a light receiving device. ) And a viewing angle. Therefore, a new display device capable of overcoming such drawbacks is actively developed.

Since the organic light emitting display device, which is one of the new display devices, is self-emitting type, the viewing angle and the contrast ratio are superior to the liquid crystal display device. In addition, since a backlight is not required, it is possible to make a light-weight thin type, and it is also advantageous in terms of power consumption. It has the advantage of being able to drive DC low voltage and has a fast response speed.

Hereinafter, the basic structure and operating characteristics of the organic light emitting display will be described in detail with reference to the drawings.

1 is a diagram for explaining the principle of light emission of a general organic light emitting diode.

In general, an organic light emitting display device includes an organic light emitting diode as shown in FIG.

The organic light emitting diode includes an anode 18 as a pixel electrode, a cathode 28 as a common electrode, and organic layers 30a, 30b, 30c, 30d and 30e formed therebetween.

The organic layers 30a, 30b, 30c, 30d and 30e are formed of a hole transport layer (HTL) 30b, an electron transport layer (ETL) 30d, a hole transport layer 30b and an electron transport layer And an emission material layer (EML) 30c interposed between the emission layers 30a and 30d.

In this case, a hole injection layer (HIL) 30a is interposed between the anode 18 and the hole transport layer 30b to enhance the emission efficiency, and electrons are injected between the cathode 28 and the electron transport layer 30d. An electron injection layer (EIL) 30e is interposed.

When the positive and negative voltages are applied to the anode 18 and the cathode 28, the organic light emitting diode having the above structure passes through the hole transporting layer 30b and the electron transporting layer 30d One electron is moved to the light emitting material layer 30c to form an exciton, and light is generated when the exciton transitions from an excited state to a ground state, that is, a stable state.

An organic light emitting display displays an image by arranging sub-pixels having organic light emitting diodes of the above-described structure in a matrix form and selectively controlling the sub-pixels with a data voltage and a scan voltage.

At this time, the organic light emitting display device is divided into an active matrix method using a passive matrix or a thin film transistor as a switching element. The active matrix method selectively turns on the thin film transistor, which is an active element, to select a sub-pixel and maintain the emission of the sub-pixel with the voltage held in the storage capacitor.

Such organic light emitting diodes are generally formed using vacuum deposition. Vacuum deposition is a method of vaporizing a material of a layer to be formed in a vacuum chamber and depositing the material on the substrate.

However, when the vacuum chamber is used, the size of the chamber must be at least larger than the size of the substrate on which the vacuum deposition is performed. Further, it is necessary to secure a sufficient space for the inflow of the substrate in the chamber, so that there is a limit to increase in size, and other methods have been considered.

One example of such a method is a method using a soluble process, which will be described with reference to the drawings.

2 is an exemplary view schematically showing the structure of a general organic light emitting diode. Here, FIG. 2 schematically shows the structure of an organic light emitting diode manufactured using a solution process.

Referring to FIG. 2, the organic light emitting diode includes a first electrode 18 formed on a substrate 1, a light emitting portion 30, and a second electrode 28, as described above.

The light emitting portion 30 includes a hole transporting layer 30b and an electron transporting layer 30d and a light emitting material layer 30c interposed between the hole transporting layer 30b and the electron transporting layer 30d.

A hole injection layer 30a is interposed between the first electrode 18 and the hole transport layer 30b and an electron injection layer 30b is formed between the second electrode 28 and the electron transport layer 30d 30e are interposed.

The light emitting portion 30 is divided into red, green, and blue sub-pixels R, G, and B to be formed through a solution process.

The hole injection layer 30a, the hole transport layer 30b and the light emitting material layer 30c are formed by a solution process, but the electron transport layer 30d, the electron injection layer 30e, and the second The electrode 128 is formed by a vacuum deposition method.

This is because the electron transporting layer 30d and the electron injecting layer 30e are poor in material stability and the solution process is difficult.

The electron transport layer 30d and the electron injection layer 30e are essentially applied to improve the efficiency of the organic light emitting diode by transferring electrons into the light emitting material layer 30c.

Generally, when the organic light emitting diode includes the low molecular weight light emitting material layer 30c, the electron transporting layer 30d using the deposition method is used. When the organic light emitting diode includes the polymer light emitting material layer 30c, 30d) or an electron injection layer 30e such as NaF is used.

In the case of the polymer organic light emitting diode, the electron injection layer 30e is diffused into the light emitting material layer 30c to increase electron injection, but the diffused region acts as a non-light emitting region, (30c) should be more than a certain thickness. However, the driving voltage increases as the thickness of the light emitting material layer 30c increases, and there is a limit in which the thickness of the light emitting material layer 30c can not be applied to a solution process.

That is, when the electron injection layer 30e such as NaF is used, Na + diffuses into the light emitting material layer 30c to improve the electron transferring ability. However, when the diffused region is overlapped with the light emitting region, the device efficiency is reduced. To prevent this, it is necessary to design the thickness of the light emitting material layer 30c to a certain level or more. However, as the thickness of the light emitting material layer 30c increases, the driving voltage increases. Also, in the solution process, there is a problem that the jetting property is lowered due to the increase of the viscosity of the solution, and thus there is a limit to the thickness increase.

An object of the present invention is to provide an organic light emitting diode manufactured using a solution process, an organic light emitting display having the organic light emitting diode, and a method of manufacturing the organic light emitting diode.

Another object of the present invention is to provide an organic light emitting diode in which an electron transport layer and an electron injection layer are removed by forming a multilayered light emitting material layer, an organic light emitting display having the same, and a method of manufacturing an organic light emitting diode.

Other objects and features of the present invention will be described in the following description of the invention and the claims.

According to an aspect of the present invention, there is provided an organic light emitting diode and an organic light emitting display including the same, wherein an electron injection material is added to form a multi-layered light emitting material layer .

For this, an organic light emitting diode and an organic light emitting display including the organic light emitting diode according to an embodiment of the present invention are sequentially disposed on a first electrode and a first electrode, and include a hole injection layer, a hole transport layer, And a second electrode located on the light emitting portion.

At this time, the light emitting material layer may have a multi-layer structure including a first light emitting layer and a second light emitting layer to which an electron injecting material is added.

The present invention also provides an organic light emitting display device including the above-described organic light emitting diode.

The present invention also provides a method of manufacturing the above-described organic light emitting diode.

In another aspect, the present invention is characterized in that the electron injecting material is added (or doped) to the electron transporting layer, and the electron injecting material is different in concentration (or density) depending on the region.

That is, the electron injecting material may have a first density in the lower region of the electron transporting layer adjacent to the luminescent material layer and a second density higher than the first density in the upper region of the electron transporting layer adjacent to the second electrode.

The present invention also provides an organic light emitting display device including the above-described organic light emitting diode.

As described above, according to the organic light emitting diode and the organic light emitting display having the same according to the embodiment of the present invention, efficiency and lifetime are improved as electron transfer is increased, And the electron transport layer can be removed, so that the processability can be secured.

Meanwhile, in the organic light emitting diode and the organic light emitting display device including the organic light emitting diode according to another embodiment of the present invention, the electron transfer characteristic of the electron transport layer is improved and the degradation of the characteristic of the light emitting material layer by the electron injecting material is minimized .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a principle of light emission of a general organic light emitting diode. FIG.
FIG. 2 is an exemplary view schematically showing the structure of a general organic light emitting diode. FIG.
3 is a block diagram schematically illustrating an organic light emitting display according to a first embodiment of the present invention.
4 is an exemplary diagram showing a circuit configuration for a sub-pixel of an organic light emitting display device.
5 is a schematic cross-sectional view of an organic light emitting display according to a first embodiment of the present invention.
FIG. 6 is an exemplary view schematically showing the structure of an organic light emitting diode in an organic light emitting display according to a first embodiment of the present invention shown in FIG. 5;
7A and 7B are exemplary views showing an example of a solution process.
8 is a graph showing current density according to a voltage as an example.
9 is a graph showing current efficiency according to current density as an example.
10 is a graph showing an example of light intensity according to a wavelength.
11 is a schematic cross-sectional view of an organic light emitting display device according to a second embodiment of the present invention.
FIG. 12 is an exemplary view schematically showing the structure of an organic light emitting diode in an organic light emitting display according to a second embodiment of the present invention; FIG.
13 is an enlarged view of a portion "A" in FIG.
14 is a graph showing current density according to a voltage as an example.

The light emitting device includes a first electrode, a light emitting portion sequentially located on the first electrode, the light emitting portion including a hole injecting layer, a hole transporting layer, and a light emitting material layer, and a second electrode located on the light emitting portion, Layer structure including a first light emitting layer and a second light emitting material layer to which an electron injection material is added.

In the organic light emitting diode of the present invention, the electron injecting material may include a water-soluble or oil-soluble alkali metal.

In the organic light emitting diode of the present invention, the second light emitting layer has a lowest unoccupied molecular orbital (LUMO) energy level of -3.0 eV to -2.6 eV and a triplet energy (T1) level of 2.0 eV to 2.5 eV Lt; / RTI >

In the organic light emitting diode of the present invention, the second light emitting layer may have an electron mobility of 10 ^-6 cm ² / Vs to 10 ^-4 cm ² / Vs.

In another aspect, the present invention provides a semiconductor device comprising:

And an organic light emitting diode (OLED) connected to the transistor.

In another aspect, the present invention provides a method of manufacturing a light emitting device, comprising: forming a first electrode on a substrate; forming a hole transport layer on each of the red, green and blue sub-pixels on the first electrode; Forming a second light emitting layer by adding an electron injecting material to the first light emitting layer, and forming a second electrode on the second light emitting layer, wherein the hole transporting layer, the first light emitting layer, The present invention also provides a method of manufacturing an organic light emitting diode formed through a solution process.

In the organic light emitting diode manufacturing method of the present invention, the solution process may be an inkjet printing process, a nozzle printing process, a transferring process, a slit coating process, a gravure printing process, And thermal jet printing.

In the organic light emitting diode manufacturing method of the present invention, the first light emitting layer may be formed using an organic solvent, and the second light emitting layer may be formed using a water-soluble material in which an electron injecting material of an alkali metal, have.

In the organic light emitting diode manufacturing method of the present invention, the first light emitting layer may be formed using a water-soluble material, and the second light emitting layer may be formed using an organic solvent in which an electron injecting material of an alkali metal, have.

According to another aspect of the present invention, there is provided a light emitting device including a first electrode, a second electrode facing the first electrode, a light emitting material layer positioned between the first and second electrodes, Wherein the electron injecting material has a first density in a lower region of the electron transporting layer adjacent to the light emitting material layer and a second density in the lower region of the electron transporting layer adjacent to the second electrode, And an organic light emitting diode having a second density higher than the first density in the upper region.

In the organic light emitting diode of the present invention, the electron injecting material may include an alkali metal.

In the organic light emitting diode of the present invention, the electron injecting material in the upper region has a weight ratio of 150% with respect to the electron transporting material, and the electron injecting material in the lower region has a weight ratio of 50% Lt; / RTI >

The organic light emitting diode of the present invention may further include a hole injection layer disposed between the first electrode and the light emitting material layer, and a hole transport layer disposed between the first electrode and the hole injection layer.

In another aspect, the present invention provides an organic light emitting display including a transistor provided on a substrate and the above-described organic light emitting diode connected to the transistor.

Hereinafter, preferred embodiments of the organic light emitting diode and the organic light emitting display including the organic light emitting diode and the organic light emitting diode according to the present invention will be described with reference to the accompanying drawings, Will be described in detail so as to be easily carried out.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification. The dimensions and relative sizes of the layers and regions in the figures may be exaggerated for clarity of illustration.

It will be understood that when an element or layer is referred to as being another element or "on" or "on ", it includes both intervening layers or other elements in the middle, do. On the other hand, when a device is referred to as "directly on" or "directly above ", it does not intervene another device or layer in the middle.

The terms spatially relative, "below," "lower," "above," "upper," and the like, And may be used to easily describe the correlation with other elements or components. Spatially relative terms should be understood to include, in addition to the orientation shown in the drawings, terms that include different orientations of the device during use or operation. For example, when inverting an element shown in the figures, an element described as "below" or "beneath" of another element may be placed "above" another element. Thus, the exemplary term "below" can include both downward and upward directions.

The terminology used herein is for the purpose of describing embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprise "and / or" comprising ", as used in the specification, means that the presence of stated elements, Or additions.

3 is a block diagram schematically showing an organic light emitting display according to a first embodiment of the present invention.

3, the organic light emitting display according to the first exemplary embodiment of the present invention includes an image processing unit 115, a data conversion unit 114, a timing control unit 113, a data driving unit 112, a gate driving unit 111 And a display panel 110 may be included.

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

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

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

The data driver 112 samples and latches the data signal DATA supplied from the timing controller 113 in response to the data timing control signal DCS supplied from the timing controller 113, And outputs it. The data driver 112 outputs the converted data signal DATA through the data lines DL1 to DLm. The data driver 112 is formed in the form of an IC (Integrated Circuit).

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

The display panel 110 may be implemented in a sub-pixel structure including, for example, a red sub-pixel SPr, a green sub-pixel SPg, and a blue sub-pixel SPb. That is, one pixel P is composed of RGB sub-pixels SPr, SPg, SPb. However, the present invention is not limited thereto, and may further include a white sub-pixel.

4 is an exemplary diagram showing a circuit configuration for a sub-pixel of an organic light emitting display device.

In this case, the sub-pixel shown in FIG. 4 is configured as a 2T (Transistor) 1C (Capacitor) structure including a switching transistor, a driving transistor, a capacitor, and an organic light emitting diode. However, the present invention is not limited to this, and when a compensation circuit is added, it can be configured in various ways such as 3T1C, 4T2C, 5T2C, and the like.

4, the organic light emitting display includes a gate line GL arranged in a first direction and a data line DL spaced apart from each other in a second direction crossing the first direction and a driving power line VDDL Sub-pixel region is defined by the sub-pixel region.

One sub-pixel may include a switching transistor SW, a driving transistor DR, a capacitor Cst, a compensation circuit CC and an organic light emitting diode OLED.

The organic light emitting diode OLED operates to emit light in accordance with the driving current generated by the driving transistor DR.

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

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

The compensation circuit CC compensates the threshold voltage of the driving transistor DR and the like. The compensation circuit CC may consist of one or more transistors and capacitors. The configuration of the compensation circuit (CC) is very various, and a detailed illustration and description thereof are omitted.

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

FIG. 5 is a schematic cross-sectional view of an organic light emitting display according to a first embodiment of the present invention. Referring to FIG.

At this time, FIG. 5 illustrates one pixel made up of red, green and blue sub-pixels, that is, RGB sub-pixels. The RGB sub-pixels may be formed by dividing the light emitting material included in each organic light emitting diode into RGB colors.

In addition, the organic light emitting display shown in FIG. 5 exemplifies a back light emitting type organic light emitting display in which light is emitted in the direction of a substrate on which pixels are arranged. However, the present invention is not limited thereto. The present invention can be applied to an organic light emitting display device of a both-side emission type as well as a top emission type organic light emitting display device in which light is emitted in a direction opposite to a substrate on which pixels are arranged.

5 illustrates an organic light emitting display device using a thin film transistor having a coplanar structure. However, the present invention is not limited to a thin film transistor having a coplanar structure.

FIG. 6 is a schematic view illustrating the structure of an organic light emitting diode in the organic light emitting display according to the first embodiment of the present invention shown in FIG.

5 and 6, the organic light emitting display device according to the first embodiment of the present invention may include a transistor (TFT) formed on a substrate 101 and an organic light emitting diode (OLED).

In this case, for example, the substrate 101 may be divided into red, green and blue sub-pixels R, G and B, and red, green and blue sub-pixels R, G and B may be regularly repeated . This regularity can be line-by-line or diagonal.

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

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

The semiconductor layer 124 may be an amorphous silicon film, a polycrystalline silicon film obtained by crystallizing amorphous silicon, an oxide semiconductor, an organic semiconductor, or the like.

At this time, a buffer layer (not shown) may be further formed between the substrate 101 and the semiconductor layer 124. The buffer layer may be formed to protect a transistor (TFT) formed in a subsequent process from an impurity such as alkali ions flowing out from the substrate 101. [

And the semiconductor layer a gate insulating film (125a) made of such as silicon nitride (SiNx) or silicon oxide (SiO ₂₎ formed on (124) are formed, and on the gate line including a gate electrode 121 (not shown) and the first A sustain electrode (not shown) is formed.

The gate electrode 121 and the gate line and the first sustain electrode may be formed of a first metal material having low resistance characteristics such as aluminum (Al), copper (Cu), molybdenum (Mo), chrome (Cr) ), Titanium (Ti), nickel (Ni), neodymium (Nd), or alloys thereof.

An interlayer insulation layer 125b made of a silicon nitride film, a silicon oxide film or the like is formed on the gate electrode 121, the gate line and the first sustain electrode. A data line (not shown), a driving voltage line (Not shown), a source electrode 122, a drain electrode 123, and a second sustain electrode (not shown).

The source electrode 122 and the drain electrode 123 are spaced apart from each other by a predetermined distance and are electrically connected to the semiconductor layer 124. For example, first and second semiconductor layer contact holes exposing both sides of the semiconductor layer 124 are formed in the gate insulating film 125a and the interlayer insulating film 125b, and the first and second semiconductor layer contact holes The source electrode 122 and the drain electrode 123 are electrically in contact with the semiconductor layer 124, respectively.

At this time, the second sustain electrode overlaps with a part of the first sustain electrode below the interlayer insulating film 125b to form a storage capacitor.

The data line, the driving voltage line, the source electrode 122, the drain electrode 123 and the second sustain electrode may be formed of a second metal material having a low resistance property such as aluminum (Al), copper (Cu), molybdenum ), Chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd) or alloys thereof.

A protective film (or a planarization film) 125c is formed on the substrate 101 on which the data lines, the driving voltage lines, the source / drain electrodes 122 and 123 and the second sustain electrodes are formed.

An overcoat layer 125d exposing a part of the drain electrode 123 is formed on the protective film 125c. The overcoat layer 125d may be formed of an organic material, but may be formed of an inorganic material or a mixture of organic and inorganic materials. At this time, if the protective film 125c serves as the overcoat layer 125d, the overcoat layer 125d may not be formed.

Next, the organic light emitting diode OLED may include a first electrode 118, a light emitting portion 130, and a second electrode 128.

The organic light emitting diode OLED is electrically connected to the driving thin film transistor TFT. More specifically, in the protective film 125c and the overcoat layer 125d formed on the driving thin film transistor TFT, a drain contact hole exposing the drain electrode 123 of the driving thin film transistor TFT is formed. The organic light emitting diode OLED is electrically connected to the drain electrode 123 of the driving thin film transistor TFT through the drain contact hole.

That is, the first electrode 118 is formed on the overcoat layer 125d and is electrically connected to the drain electrode 123 of the driving thin film transistor TFT through the drain contact hole.

The first electrode 118 supplies current (or voltage) to the light emitting unit 130, and defines a light emitting region having a predetermined area.

In addition, the first electrode 118 serves as an anode. Accordingly, the first electrode 118 is made of a transparent conductive material having a relatively large work function. For example, indium tin oxide (ITO) or indium zinc oxide (IZO) . However, the present invention is not limited thereto.

5 illustrates a case where the first electrode 118 is patterned by being divided into red, green and blue sub-pixels R, G and B, but the present invention is not limited thereto. The first electrode 118 may be formed as one layer connected across all the pixels.

A bank 125e is formed on the substrate 101 on which the first electrode 118 is formed. At this time, the bank 125e surrounds the edge of the first electrode 118 to define an opening, and is made of an organic insulating material.

The bank 125e may also be made of a photosensitizer containing a black pigment, in which case the bank 125e serves as a light shielding member.

The light emitting portion 130 and the second electrode 128 are sequentially formed on the substrate 101 on which the bank 125e is formed.

That is, the light emitting portion 130 is formed between the first electrode 118 and the second electrode 128. The light emitting unit 130 emits light by the combination of the holes supplied from the first electrode 118 and the electrons supplied from the second electrode 128.

The light emitting unit 130 may have a multilayer structure including auxiliary layers 130a and 130b for improving light emission efficiency of the light emitting material layer 130c in addition to the light emitting material layer 130c.

That is, the light emitting unit 130 includes a hole transport layer 130b and a light emitting material layer 130c.

A hole injecting layer 130a may be interposed between the first electrode 118 and the hole transporting layer 130b in order to improve luminous efficiency according to the configuration of the device.

The hole transporting layer 130b may be composed of a single layer or two layers.

The light emitting unit 130 according to the first embodiment of the present invention may include a first light emitting layer 130c 'and an electron injection material for improving the interface characteristics with the hole transporting layer 130b, And a light emitting material layer 130c having a laminated structure of the second light emitting layer 130c "

That is, the first light emitting layer 130c 'can be formed of a material which improves the interface property with the hole transporting layer 130b to increase the lifetime of the device. The second light emitting layer 130c "may be made of a material that improves efficiency by increasing electron injection by adding an electron injecting material.

Here, the second light emitting layer 130c "uses a solvent that does not damage the first light emitting layer 130c 'and is doped with an electron injecting material. Therefore, the second light emitting layer 130c" The injection characteristics are improved and the efficiency can be improved without the electron transport layer and the electron injection layer.

As an example of the electron injecting material, a water-soluble or oil-soluble alkali metal may be included.

When an organic solvent is used for the first light emitting layer 130c ', the second light emitting layer 130c' 'can form a multi-layer structure that does not damage the first light emitting layer 130c' using a water soluble material Alternatively, when a water-soluble material is used for the first light-emitting layer 130c ', the second light-emitting layer 130c' 'may form a multi-layer structure using an organic solvent.

The second light emitting layer 130c '' may have a lowest unoccupied molecular orbital (LUMO) energy level of about -3.0 eV to -2.6 eV and a triplet energy (T1) level of about 2.0 eV to 2.5 eV .

The second light emitting layer 130c "may have an electron mobility of about 10 ^-6 cm ² / Vs to 10 ^-4 cm ² / Vs.

As described above, the present invention can smoothly transfer electrons while removing the electron transport layer and the electron injection layer of the conventional evaporation method, thereby securing the efficiency and lifetime of the organic light emitting diode.

That is, the phenomenon of diffusion into the light emitting material layer 130c does not occur due to the removal of the electron transporting layer and the electron injecting layer, and the formation of the light emitting region in the light emitting material layer 130c is not limited.

The light emitting unit 130 may be divided into red, green, and blue sub-pixels R, G, and B to be formed through a soluble process. Which can be formed by selectively coating a solution-processable material of low molecular weight or high molecular weight on the first electrode 118.

At this time, the hole injection layer 130a may be omitted, or the hole injection layer 130a and the hole transport layer 130b may be formed of one layer by mixing materials. In addition, the hole injection layer 130a and the hole transport layer 130b may be formed by dividing into two or more layers.

Here, the material forming the light emitting material layer 130c of the red, green and blue sub-pixels R, G and B formed by the solution process may be a fluorescent light emitting material or a phosphorescent light emitting material, respectively. These light emitting material layers 130c may include one or more dopants capable of expressing the luminescent color in one or more hosts.

The solution process can be selected from inkjet printing, nozzle printing, transferring process, thermal jet printing, or spin coating.

Such a solution process may proceed without a separate mask or chamber. Therefore, the solution process has a simpler process and a lower process cost than the deposition process, thereby reducing the processing time and manufacturing cost of the organic light emitting diode (OLED).

Particularly, in the present invention, the electron injecting layer and the electron transporting layer using the existing deposition process can be removed and the processability can be secured.

Hereinafter, a method of a solution process applied to manufacture the light emitting unit 130 according to the first embodiment of the present invention will be described as an example.

7A and 7B are illustrations showing examples of a solution process.

Fig. 7A relates to inkjet printing, in which printing is performed through a head 140 having a jetting port capable of dropping ink 145 on a substrate 101. Fig.

In this case, the head 140 or the substrate 101 moves during printing. In this case, fine control for each area is easy. That is, selective coating of each sub-pixel of the organic light emitting display device can be easily performed.

In addition to inkjet printing, nozzle printing is a process of preparing a slit-shaped nozzle and printing on the substrate 101. [ A plurality of such nozzles may be provided. It is relatively easy to print a pattern distributed over a wider area than the ink-jet printing method. For example, in the case of an organic light emitting display device in which a bank is formed on a substrate 101, when a predetermined layer is formed by the front nozzle printing method, it is possible to divide the organic light emitting display device by the bank.

7B illustrates roll printing in which a main roller 150 on which a pattern 155 is formed is rotated to form a print pattern on the substrate 101. FIG. In this case, the sub-roller 151 is connected to the head to which the printing solution is supplied, thereby guiding the printing solution from the head to be continuously supplied onto the pattern 155 of the main roller 150. In some cases, when the pattern 155 is not formed on the main roller 150, the entire substrate 101 can be coated.

Additional examples of such solution processes include transferring processes, gravure printing and thermal jet printing.

However, the above-mentioned examples are limited to the solution process, and may be performed by solution process of other equipment or other process depending on development of equipment and the like.

Referring again to FIGS. 5 and 6, the second electrode 128 is formed on the light emitting portion 130 to provide electrons to the light emitting portion 130.

The second electrode 128 may be formed to cover the entire substrate 101. That is, the second electrode 128 may be formed as one layer connected to all the pixels.

Hereinafter, characteristics of the organic light emitting diode according to the first embodiment of the present invention will be described with reference to the drawings.

8 is a graph showing the current density J according to the voltage as an example.

9 is a graph showing current efficiency according to the current density as an example.

10 is a graph showing an example of light intensity according to a wavelength. Here, FIG. 10 shows an example of the light intensity according to the wavelength of the red light emitting material layer.

In this case, Comparative Example 1 shown in FIGS. 8 to 10 shows a general light emitting diode having an electron injecting layer, and Comparative Example 2 shows a general light emitting diode having an electron injecting layer and an electron transporting layer.

Referring to FIG. 8, Comparative Example 1 having an electron transport layer as well as an electron injection layer shows a larger current density at the same voltage as that of Comparative Example 1 having only an electron injection layer.

It can be seen that the first embodiment of the present invention including the light emitting portion having the multilayer structure without the electron injecting layer and the electron transporting layer (Test Example 1) exhibits a larger current density than the above-described Comparative Example 1 and Comparative Example 2 . This may mean that the efficiency is improved as well as it is possible to drive at a lower voltage.

Referring to FIG. 9, it can be seen that the current efficiency is improved according to the current density. In the first embodiment of the present invention (Experimental Example 1), the current efficiency is improved as compared with Comparative Example 1 and Comparative Example 2.

In addition, a high efficiency at the same current may mean that the lifetime is improved.

Referring to FIG. 10, in the case of Comparative Example 1, a peak occurs at a wavelength band higher than the red light wavelength (600 to 650 nm) due to the movement of the emission region as the electron injection layer material diffuses into the light emitting material layer. .

On the other hand, in the case of Comparative Example 2 and Experimental Example 1, the tendency is reduced and color purity is improved.

FIG. 11 is a schematic cross-sectional view of an organic light emitting display according to a second embodiment of the present invention. FIG. 12 is a cross-sectional view of an organic light emitting display according to a second embodiment of the present invention. And Fig.

11 and 12, the organic light emitting display according to the second exemplary embodiment of the present invention may include a transistor (TFT) formed on a substrate 201 and an organic light emitting diode (OLED).

The substrate 201 may include red, green and blue sub-pixels R, G and B and the red, green and blue sub-pixels R, G and B may be regularly repeated. For example, the substrate 201 is made of an insulating material such as glass, a transparent plastic or a polymer film, and can have a flexible characteristic.

The transistor (TFT) which is a driving element includes a semiconductor layer 224, a gate electrode 221, a source electrode 222 and a drain electrode 223.

A semiconductor layer 224 is formed over the substrate 201. For example, the semiconductor layer 224 may be formed of polycrystalline silicon, an oxide semiconductor material, or an organic semiconductor material crystallized from amorphous silicon or amorphous silicon.

At this time, a buffer layer (not shown) may be further formed between the substrate 201 and the semiconductor layer 224. The buffer layer may be formed to protect a transistor (TFT) formed in a subsequent process from impurities such as alkali ions flowing out from the substrate 201. [

On the semiconductor layer 224, a gate insulating film 225a is formed. A gate insulating film (225a) it may be made of an inorganic insulating material such as silicon nitride (SiNx) or silicon oxide (SiO _2).

A gate electrode 221, a gate line (not shown) and a first sustain electrode (not shown) are formed on the gate insulating film 225a.

The gate electrode 221, the gate line, and the first sustain electrode are made of a first metal material having low resistance characteristics. For example, the first metal material may be at least one selected from the group consisting of Al, Cu, Mo, Cr, Au, Ti, Ni, . ≪ / RTI > Further, each of the gate electrode 221, the gate line, and the first sustain electrode may have a single-layer or multi-layer structure.

An interlayer insulation layer 225b is formed on the gate electrode 221, the gate line, and the first sustain electrode. For example, the interlayer insulating film 225b may be formed of an inorganic insulating material such as a silicon nitride film or a silicon oxide film.

A data line (not shown), a driving voltage line (not shown), a source electrode 222, a drain electrode 223, and a second sustain electrode (not shown) are formed on the interlayer insulating film 225b.

The source electrode 222 and the drain electrode 223 are spaced apart from each other by a predetermined distance and are electrically connected to the semiconductor layer 224. For example, first and second semiconductor layer contact holes exposing both sides of the semiconductor layer 224 are formed in the gate insulating film 225a and the interlayer insulating film 225b, and the first and second semiconductor layer contact holes The source electrode 222 and the drain electrode 223 are in electrical contact with the semiconductor layer 224. [

At this time, the second sustain electrode overlaps with a part of the first sustain electrode below the interlayer insulating film 125b to form a storage capacitor.

The data line, the driving voltage line, the source electrode 222, the drain electrode 223, and the second sustain electrode are made of a second metal material having low resistance characteristics. For example, the second metal material may be aluminum (Al), copper (Cu), molybdenum (Mo), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium . ≪ / RTI > Each of the data line, the driving voltage line, the source electrode 222, the drain electrode 223, and the second sustain electrode may have a single layer structure or a multilayer structure.

Although not shown, a switching element having substantially the same shape as a thin film transistor (TFT) as a driving element is further formed in each of the red, green and blue sub-pixels R, G and B. The switching element is electrically connected to a gate line, a data line, and a thin film transistor (TFT) which is a driving element.

A protective film (or a flattening film) 225c and an overcoat layer 225d are stacked on a substrate 201 on which a data line, a driving voltage line, a source electrode 222, a drain electrode 223 and a second sustain electrode are formed. A drain contact hole exposing the drain electrode 223 is formed in the protective film 225c and the overcoat layer 225d.

Each of the passivation layer 225c and the overcoat layer 225d may be formed of an inorganic insulating material such as silicon oxide or silicon nitride or an organic insulating material such as photo-acryl and the passivation layer 225c and the overcoat layer 225d. Can be omitted.

The organic light emitting diode OLED is located on the overcoat layer 225d and electrically connected to the thin film transistor TFT. The organic light emitting diode OLED may include a first electrode 218, a light emitting portion 230, and a second electrode 228.

The first electrode 218 is formed on the overcoat layer 225d for red, green and blue sub-pixels R, G and B and is electrically connected to the drain electrode 223 of the driving thin film transistor TFT through the drain contact hole And is electrically connected. The first electrode 218 supplies current (or voltage) to the light emitting unit 230, and defines a light emitting region having a predetermined area.

In addition, the first electrode 218 may be made of a transparent conductive material having a relatively large work function and function as an anode. For example, the first electrode 218 may be formed of indium tin oxide (ITO) or indium zinc oxide (IZO). However, the present invention is not limited thereto.

When the organic electroluminescent display device is a top emission type, a reflective electrode or a reflective layer may be further formed on a lower portion and / or an upper portion of the first electrode 218. For example, the reflective electrode or the reflective layer may be formed of an aluminum-palladium-copper (APC) alloy. That is, the first electrode 218 may have a two-layer structure of a transparent conductive electrode, a reflective electrode, or a reflective layer, or may have a triple-layer structure in which a reflective electrode or a reflective layer is positioned above and below the transparent conductive electrode.

A bank 225e is formed on the substrate 201 on which the first electrode 218 is formed. The bank 225e covers an edge of the first electrode 218 and has an opening exposing the center of the first electrode 218. [ The bank 225e may be made of a transparent organic insulating material. Meanwhile, the bank 225e may be formed of a photosensitive material including a black pigment and may serve as a light shielding member.

The light emitting portion 230 and the second electrode 228 are sequentially formed on the first electrode 218. That is, the light emitting portion 230 is located between the first electrode 218 and the second electrode 228. The light emitting unit 230 emits light by the combination of the holes supplied from the first electrode 218 and the electrons supplied from the second electrode 228.

The light emitting unit 230 includes a light emitting material layer 230c that emits light and an electron transporting layer 230d that is positioned between the light emitting material layer 230c and the second electrode 228. [ The light emitting unit 230 may further include a hole transport layer 230a and a hole transport layer 230b which are sequentially stacked between the first electrode 218 and the light emitting material layer 230c.

At this time, the electron transporting layer 230d includes an electron transporting material and an electron injecting material 232 having an excellent electron injecting property. The electron transport material may have a LUMO energy level of -3.0 to -2.0 eV and an electron mobility of about 10 ^-5 cm ² / Vs to 10 ^-3 cm ² / Vs. In addition, the electron-transporting layer 230d doped with the electron injecting material 232 may have a triplet energy (T1) level of about 2.0 eV to 2.5 eV.

For example, the electron injecting material 232 may be selected from water-soluble or oil-soluble alkali metals.

The electron injection material 232 has a concentration gradient (or density gradient) along the vertical direction.

13, the electron injecting material 232 in the lower region 240 of the electron transporting layer 230d adjacent to the light emitting material layer 230c has a first concentration or density And the electron injecting material 232 in the upper region 250 of the electron transporting layer 230d adjacent to the second electrode 228 has a second concentration (or density) greater than the first concentration (or density).

For example, in the upper region 250, the electron injecting material 232 has a weight ratio of 150% with respect to the electroconductive material, and the electron injecting material 232 in the lower region 240 has a weight ratio of 50 with respect to the electroconductive material. % ≪ / RTI > by weight.

The electron injection material 232 has a concentration gradient in the lower region 230 and the upper region 240, respectively. That is, in each of the lower region 230 and the upper region 240, the concentration (or density) of the electron injecting material 232 decreases from the upper region 240 toward the lower region 230. Alternatively, the electron injecting material 232 may have the same concentration (or density) in the lower region 230 and the upper region 240, respectively.

The electron transporting layer 230d includes the electron injecting material 232 to improve the electron injecting property. Therefore, a thin organic light emitting diode having a simple structure without an electron injection layer can be provided.

In addition, since the electron injecting material 232 has a concentration gradient in the electron transporting layer 230d, diffusion of the electron injecting material 232 into the light emitting material layer 230c can be minimized. That is, in order to obtain desired electron injection characteristics, a certain concentration of the electron injecting material 232 must be doped in the electron transporting layer 230d. The electron injecting material 232 is doped in the lower region 240 adjacent to the light emitting material layer 230c Since the electron injection material 232 has a low concentration (or density), diffusion of a certain concentration of the electron injecting material 232 into the light emitting material layer 230c is minimized.

In other words, it is possible to prevent the problem of device efficiency and life span reduction due to the diffusion of the electron injecting material 232 while improving the electron injecting property.

Experimental Example 2

ITO and a hole blocking layer (Liq, 1 nm) were deposited on a glass substrate, and then an electron transporting layer (50 nm) doped with an electron injecting material and a cathode (Al, 100 nm) were sequentially laminated. (electron only device)

Comparative Example 3

ITO and a hole blocking layer (Liq, 1 nm) were deposited on a glass substrate, and then an electron-transporting layer (50 nm) without doping of an electron injecting material and a cathode (Al, 100 nm) were sequentially laminated.

The current density according to the voltages of Experimental Example 3 and Comparative Example 2 was measured and shown in FIG.

As shown in FIG. 14, the characteristics of the organic light emitting diode using the electron transporting layer including the electron injecting material are improved.

While a great many are described in the foregoing description, it should be construed as an example of preferred embodiments rather than limiting the scope of the invention. Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

118, 218: first electrode 128, 228: second electrode
130, 230: light emitting portion 130a, 230a: hole injection layer
130b, 230b: Hole transport layer 130c, 230c: Light emitting material layer
130c ': first light emitting layer 130c': second light emitting layer
230d: electron transport layer 232: electron injection material
240: lower region 250: upper region

Claims (14)

A first electrode;
A light emitting portion sequentially disposed on the first electrode, the light emitting portion including a hole injection layer, a hole transport layer, and a light emitting material layer; And
And a second electrode
/ RTI >
Wherein the light emitting material layer has a multi-layer structure including a first light emitting layer and a second light emitting layer to which an electron injection material is added,
Wherein the first light emitting layer is in contact with the hole transporting layer, and the second light emitting layer is in contact with the first light emitting layer and the second electrode.
The method according to claim 1,
Wherein the electron injecting material comprises a water-soluble or oil-soluble alkali metal.
The method according to claim 1,
Wherein the second light emitting layer has a lowest unoccupied molecular orbital (LUMO) energy level of -3.0 eV to -2.6 eV and a triplet energy (T1) level of 2.0 eV to 2.5 eV.
The method according to claim 1,
And the second light emitting layer has a value of electron mobility of 10 ^-6 cm ² / Vs to 10 ^-4 cm ² / Vs.
A transistor provided on a substrate;

The organic light emitting diode according to any one of claims 1 to 4, which is connected to the transistor
And an organic electroluminescent display device.
Forming a first electrode on the substrate;
Forming a hole transport layer on each of the red, green and blue sub-pixels on the first electrode;
Forming a first light emitting layer on the hole transport layer;
Forming a second light emitting layer by adding an electron injecting material to the first light emitting layer; And
Forming a second electrode on the second light emitting layer
/ RTI >
The hole transport layer, the first light emitting layer and the second light emitting layer are formed through a solution process,
Wherein the first light emitting layer is in contact with the hole transporting layer and the second light emitting layer is in contact with the first light emitting layer and the second electrode.
The method according to claim 6,
The solution process may be performed by any one of inkjet printing, nozzle printing, transferring process, slit coating, gravure printing and thermal jet printing Wherein the organic light-emitting diode is formed on the substrate.
The method according to claim 6,
Wherein the first light emitting layer is formed using an organic solvent and the second light emitting layer is formed using a water soluble material in which an electron injecting material of an alkali metal is soluble and water soluble.
The method according to claim 6,
Wherein the first light emitting layer is formed using a water-soluble material, and the second light emitting layer is formed using an organic solvent in which an electron injecting material of an alkali metal is soluble and water soluble.


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