KR20120075271A - White organic light emitting device - Google Patents

Abstract

PURPOSE: A white organic light emitting device is provided to improve color sense by including a second light emitting layer containing phosphorescence yellow dopant and fluorescence orange dopant. CONSTITUTION: A first electrode(110) is formed on a substrate(100). A hole injection layer(112) and a hole-transport layer(114) are formed on the first electrode. A first light emitting layer(122) and a second light-emitting layer(124) are formed on the hole-transport layer. The first light emitting layer is a single light emitting layer in which fluorescence normal blue dopant is doped on a host. The second light-emitting layer is a single light emitting layer in which phosphorescence yellow dopant and fluorescence orange dopant are doped on a host. An electron-transport layer(116) and an electron injection layer(118) are formed on the second light-emitting layer. A second electrode(119) is formed on the electron injection layer.

Description

White organic light emitting element {WHITE ORGANIC LIGHT EMITTING DEVICE}

The present invention relates to a white organic light emitting device, and more particularly, to a white organic light emitting device capable of improving lifetime and efficiency.

In recent years, the display field for visually expressing electrical information signals has been rapidly developed as the information age has been developed, and various flat panel display devices having excellent performance of thinning, light weight, and low power consumption have been developed. Flat Display Device has been developed and is rapidly replacing the existing Cathode Ray Tube (CRT).

Specific examples of such a flat panel display include a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), and an organic light emitting display. (Organic Light Emitting Device: OLED) and the like.

Among them, the organic light emitting diode display is considered as a competitive application for the compactness of the device and the vivid color display without requiring a separate light source.

Formation of an organic light emitting layer is essential for the organic light emitting diode display, and a deposition method using a shadow mask has been conventionally used for the formation thereof.

However, in the case of a large area, the shadow mask has a drooping phenomenon due to its load, which makes it difficult to use it several times, and a defect occurs in the formation of the organic light emitting layer pattern, and thus an alternative method is required.

There is a white organic light emitting display device as one of several methods that have been proposed to replace the shadow mask.

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

The white organic light emitting diode display is a method of depositing each layer between an anode and a cathode without a mask when forming a light emitting diode, and forming organic layers including an organic light emitting layer in a vacuum state by sequentially changing their components.

A white organic light emitting diode display is a device having various uses, such as a thin light source, a backlight of a liquid crystal display, or a full color display employing a color filter. The white organic light emitting diode display is largely classified into wavelength modification and color mixing to realize white light emission. First, the wavelength conversion method is based on the principle that blue or purple light emitted from the OLED excites the phosphor. The wavelengths are mixed to form a wide spectrum of wavelengths to form white light. This technique is called down conversion by phosphors.

The color mixing method is a technique of mixing white light using various light emitters in one device. This technology includes a multilayer structure of red, green, and blue light emitting layers, a microcavity structure, a stacked structure of devices vertically and horizontally, mixing various phosphors into a single layer structure, and a doping method, depending on the structure of the device.

Among them, a white organic light emitting diode display having a multi-layered structure is obtained by stacking two or more layers of light emitting layers of different colors to obtain white light. This structure is based on the principle that light is emitted from different light emitting layers at the same time, and light of various colors is mixed, resulting in white light. At least three layers of light emitting layers emitting different colors may be stacked. However, as the number of layers increases, the cost increases, and white light is generally realized using two layers of light emitting layers.

In order to realize such white light, phosphorescent yellow dopant is doped in one of two light emitting layers, and deep blue dopant is doped in another light emitting layer. Accordingly, the yellow light emitted from the phosphorescent yellow dopant-doped light emitting layer and the blue light emitted from the fluorescent deep blue dopant-doped light emitting layer are mixed to realize white light. However, when the deep blue dopant is used, the life and efficiency of the white organic light emitting device are deteriorated.

The present invention has been made to solve the above problems, to provide a white organic light emitting device that can improve the life and efficiency.

To this end, the white organic light emitting diode according to the present invention is formed between a first electrode and a second electrode facing each other on a substrate, and between the first electrode and the second electrode, and has a wavelength band of 460 nm to 465 nm in one host. A first light emitting layer doped with a fluorescent normal blue dopant having a range, a phosphorescent yellow dopant formed on or under the first light emitting layer having a wavelength range of 560 nm to 570 nm in one host, and a range of wavelength range of 570 nm to 580 nm The branch includes a second light emitting layer doped with a fluorescent orange dopant.

Further, a hole injection layer and a hole transport layer are further included between the first light emitting layer and the first electrode, and an electron transport layer and an electron injection layer are further included between the second light emitting layer and the second electrode.

In addition, the doping ratio of the phosphorescent yellow is formed to 3 to 20% based on the thickness of the second light emitting layer, the doping ratio of the fluorescent orange is formed to 0.1 to 5% based on the thickness of the second light emitting layer.

The second light emitting layer is formed by co-deposition of the phosphorescent yellow dopant and the fluorescent orange dopant in one host.

The organic light emitting device may further include an interlayer organic layer between the first light emitting layer and the second light emitting layer to compensate an energy level between the first light emitting layer and the second light emitting layer.

The white organic light emitting diode according to the present invention includes a first electrode and a second electrode facing each other on a substrate, a hole injection layer, a first hole transport layer, a first light emitting layer, and a first electron between the first electrode and the second electrode. A first stack in which the transport layers are sequentially stacked; a second stack in which a second hole transport layer, a second light emitting layer, a second electron transport layer, and an electron injection layer are sequentially stacked between the first stack and the second electrode; And a charge generating layer formed between the first stack and the second stack to control charge balance between the stacks, wherein the first light emitting layer is doped with a fluorescent normal blue dopant having a wavelength range of 460 nm to 465 nm in one host. The second light emitting layer is doped with a phosphorescent yellow dopant having a wavelength range of 560 nm to 570 nm and a fluorescent orange dopant having a wavelength range of 570 nm to 580 nm in one host.

Here, the doping ratio of the phosphorescent yellow is formed to 3 to 20% based on the thickness of the second light emitting layer, the doping ratio of the fluorescent orange is formed to 0.1 to 5% based on the thickness of the second light emitting layer.

The second light emitting layer is formed by co-deposition of the phosphorescent yellow dopant and the fluorescent orange dopant in one host.

The white organic light emitting diode according to the present invention includes a first light emitting layer doped with a fluorescent normal blue dopant having a wavelength range of 460 nm to 465 nm in one host, and a 560 nm to 570 nm formed in an upper or lower portion of the first light emitting layer. And a second light emitting layer doped with a phosphorescent yellow dopant having a wavelength range of and a fluorescent orange dopant having a range of 570 nm to 580 nm.

In this case, the doping ratio of the phosphorescent yellow is formed at 3 to 20% based on the thickness of the second light emitting layer, and the doping ratio of the fluorescent orange is formed at 0.1 to 5% based on the thickness of the second emitting layer.

The life and efficiency of the device may be improved through the first light emitting layer having the above-described conditions. The second light emitting layer having the above-described conditions may improve the lifetime and efficiency of the device through the phosphorescent yellow dopant, and may improve the color through the fluorescent orange dopant.

1A to 1C are perspective views illustrating a white organic light emitting diode according to a first embodiment of the present invention.
FIG. 2 is a color coordinate for explaining implementing white light using a normal blue dopant, a deep blue dopant, a yellow dopant, and an orange dopant.
3 is a perspective view illustrating a driving principle in a second light emitting layer according to the first embodiment of the present invention illustrated in FIG. 1A.
4A and 4B are perspective views illustrating a white organic light emitting diode according to a second exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The configuration of the present invention and the operation and effect thereof will be clearly understood through the following detailed description. Before describing the present invention in detail, the same components are denoted by the same reference symbols as possible even if they are displayed on different drawings. In the case where it is judged that the gist of the present invention may be blurred to a known configuration, do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 1A to 4.

1A to 1C are perspective views illustrating a white organic light emitting diode according to a first embodiment of the present invention.

Referring to FIG. 1A, a white organic light emitting diode according to a first embodiment of the present invention may have holes formed between a first electrode 110 and a second electrode 119, and a first electrode 110 and a second electrode 119. Hole Injection Layer (HIL) 112, Hole Transport Layer (HTL) 114, First Light Emitting Layer 122, Second Light Emitting Layer 124, Electron Transport Layer (ETL) ( 116 and an Electron Injection Layer (EIL) 118 are stacked and formed. The white organic light emitting diode according to the first exemplary embodiment of the present invention is a white organic light emitting diode having a multi-layered structure, in which two or more light emitting layers of different colors are stacked to obtain white light. In this structure, light is emitted from different light emitting layers at the same time, and light of various colors is mixed. As a result, white light is the principle.

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

The second electrode 119 is formed of gold (Au), aluminum (AL), molybdenum (MO), chromium (Cr), copper (Cu), or the like as a reflective metal material, such as aluminum.

As illustrated in FIG. 1A, the first light emitting layer 122 may be formed of a single light emitting layer doped with a fluorescence normal blue dopant in one host, and the second light emitting layer 124 may be one. The host may be a single light emitting layer formed by doping a phosphorescent yellow dopant and a fluorescent orange dopant. Accordingly, blue light emitted from the first light emitting layer 122 and orange light emitted from the second light emitting layer 124 are mixed to realize white light.

Alternatively, as illustrated in FIG. 1B, the first emission layer 122 may be a single emission layer formed by doping a phosphorescent yellow dopant and a fluorescent orange dopant to one host, and a second emission layer 122. The emission layer 124 may be formed as a single emission layer doped with a fluorescence normal blue dopant in one host. Accordingly, orange light emitted from the first light emitting layer 122 and blue light emitted from the second light emitting layer 124 are mixed to realize white light.

As shown in FIG. 1C, an interlayer organic layer 126 may be formed between the first light emitting layer 122 and the second light emitting layer. The interlayer organic layer 126 may display a more enhanced color by adjusting carrier balancing.

The wavelength band of the fluorescent normal blue dopant has a range of 460 nm to 465 nm, the wavelength band of the phosphorescent yellow dopant has a range of 560 nm to 570 nm, and the wavelength band of the fluorescent orange dopant has a range of 570 nm to 580 nm.

In addition, the doping ratio of the phosphorescent yellow is 3-20% based on the thickness of the first or second light emitting layers 122 and 124, and the doping ratio of the fluorescent orange is the first or second light emitting layer. Based on the thickness of 0.1 to 5% is formed. In such a ratio, the phosphorescent yellow dopant and the fluorescent orange dopant are co-depositioned to one host and formed in the first or second light emitting layer.

FIG. 2 is a color coordinate for explaining implementing white light using a normal blue dopant, a deep blue dopant, a yellow dopant, and an orange dopant. 3 is a perspective view showing a driving principle in the second light emitting layer according to the first embodiment of the present invention shown in FIG.

In the white organic light emitting diode, blue light emitted from the first light emitting layer 122 and orange light emitted to the second light emitting layer 124 are mixed to implement white light. In order to display cool white, the first light emitting layer 122 of the white organic light emitting diode is formed of a single light emitting layer doped with a fluorescent deep blue dopant in one host, and the second light emitting layer 124. Is formed as a single light emitting layer doped with a phosphorescent yellow dopant in one host. As such, the white organic light emitting device using the fluorescent deep blue dopant exhibits poor life and efficiency characteristics. A detailed description thereof will be described with reference to FIG. 2.

Specifically, the first curve 162 illustrated in FIG. 2 is a white organic material including a first light emitting layer doped with a fluorescent deep blue dopant in one host and a second light emitting layer doped with a phosphorescent yellow dopant in one host. A color coordinate graph showing a white region displayed when the light emitting device is driven, and the second curve 160 shows a first light emitting layer doped with a fluorescent normal blue dopant in one host, a phosphorescent yellow dopant and a fluorescent orange dopant in one host. Is a color coordinate graph showing a white region displayed when driving a white organic light emitting diode according to the present invention including a doped second light emitting layer.

In this case, the fluorescent normal blue dopant means a dopant having a wavelength range of 460 nm to 465 nm, and the fluorescent deep blue dopant means a dopant having a wavelength range of 450 nm to 455 nm, and phosphorescent yellow. (Yellow) Dopant means a dopant having a wavelength range of 560nm ~ 570nm, fluorescent orange dopant (orange) dopant means a dopant having a wavelength range of 570nm ~ 580nm.

On the other hand, the color coordinates will be described briefly. The lifetime and efficiency of the device depend on the value of CIEy for the blue region, and the color of the device depends on the value of CIEx for the orange and yellow regions.

In other words, the larger the value of CIEy for the blue region of the color coordinate, the higher the efficiency and lifetime of the device. Accordingly, since the value of CIEy for the fluorescent deep blue region is lower than that of the fluorescent normal blue region according to the present invention, the efficiency and lifetime thereof are low. In addition, the larger the CIEx value for the orange region and the yellow region of the color coordinates, the more the color of the device is improved. Accordingly, since the value of CIEx for the phosphorescent yellow region is smaller than the value of CIEx than the phosphorescent yellow dopant and fluorescent orange dopant regions according to the present invention, the resulting color is low.

As described above, according to the present invention, the first light emitting layer 122 is doped with a fluorescent normal blue dopant to increase efficiency and lifetime. In addition, the lifespan and efficiency were improved by doping the second light emitting layer 124 with the phosphorescent yellow dopant, and at the same time, the color light was improved by doping the fluorescent orange dopant in the second light emitting layer 124.

As shown in [Table 1], the external quantum efficiency (EQE) and the current efficiency (cd / A) are increased, and the color of the color coordinates (CIEx, CIEy) is also improved.

Light emitting layer cd / A EQE (%) CIEx CIEy Phosphorescent Yellow +
Fluorescent Oragne 28.2 10.1 0.48 0.509

[Table 1] shows that the phosphorescent yellow dopant having a wavelength range of 560 nm to 570 nm is doped at 3 to 20% based on the thickness of the second light emitting layer, and the fluorescent orange dopant having a wavelength range of 570 nm to 580 nm is second. This is a result for the case of doping at 0.1 to 5% based on the thickness of the light emitting layer.

3 is an energy diagram illustrating a driving principle in a second light emitting layer according to the first embodiment of the present invention.

As shown in FIG. 3, the energy level level in the second light emitting layer 124 is lower unoccupied molecular orgital (LUMO) energy level (Ph.HOST LUMO)> phosphorescent yellow (YELLOW) dopant of the phosphorescent host HOST. LUMO energy level (Ph.DOPANT LUMO) of> orange fluorescent (ORANGE) dopant LUMO energy (Fl.DOPANT LUMO) in the order of high. In addition, the HOMO (Highest Occupied Molecular Orbital (HOMO)) energy level (Ph.HOST HOMO) of the phosphorescent host> LUMO energy level (Ph.DOPANT HOMO) of the phosphorescent yellow dopant> LUMO energy (Fl.DOPANT HOMO) of the fluorescent orange dopant Low)

The driving principle in the second light emitting layer 124 having such an energy level is that the excitons formed from Ph. YEOLLOW DOPNAT, which has high efficiency and lifetime, transfer energy to ORANGE DOPNAT, which has good color. do. Accordingly, excitons having improved efficiency and lifespan are transferred to orange dopants to emit orange light having improved color. As described above, the white organic light emitting diode according to the first exemplary embodiment of the present invention has improved lifespan and efficiency and improved color.

4A and 4B are perspective views illustrating a white organic light emitting diode according to a second exemplary embodiment of the present invention.

Referring to FIG. 4A, a white organic light emitting diode according to a second exemplary embodiment of the present invention may include a first electrode 110, a second electrode 119, and a first electrode 110 facing each other on a substrate 100. A first stack 130, a charge generation layer 140, and a second stack 150 stacked between the second electrodes 119 are included. The multi-stack white organic light emitting device includes a light emitting layer having a different color in each stack, and light of different colors emitted from the light emitting layer of each stack is mixed to realize white light.

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

The second electrode 119 is formed of gold (Au), aluminum (AL), molybdenum (MO), chromium (Cr), copper (Cu), or the like as a reflective metal material, such as aluminum.

The first stack 130 includes a hole injection layer (HIL) 132 and a first hole transport layer (HTL) 134 between the first electrode 110 and the charge generation layer 140. The first light emitting layer 136 and the first electron transport layer (ETL) 138 are stacked in this order.

As illustrated in FIG. 4A, the first emission layer 136 may be formed as a single emission layer doped with a fluorescence normal blue dopant in one host. At this time, the wavelength range of the fluorescent normal blue dopant has a range of 460 nm to 465 nm.

A charge generation layer (CGL) 140 is formed between the stacks to control charge balance between the stacks. The charge generation layer 140 is positioned adjacent to the first stack 130 and adjacent to the N type organic layer 142 and the second stack 150 which inject electrons into the first stack 130. It is made of a P-type organic layer 144 positioned to inject holes into the second stack 150.

The second stack 150 includes a second hole transport layer 152, a second light emitting layer 154, a second electron transport layer 156, and an electron injection layer 158 between the second electrode 119 and the charge generation layer 140. ) Are stacked one by one.

As shown in FIG. 4A, the second emission layer 154 may be a single emission layer formed by doping a phosphorescent yellow dopant and a fluorescent orange dopant to one host. The wavelength range of the phosphorescent yellow dopant has a range of 560 nm to 570 nm, and the wavelength range of the fluorescent orange dopant has a range of 570 nm to 580 nm. The doping ratio of the phosphorescent yellow is 3-20% based on the thickness of the second emitting layer, and the doping ratio of the fluorescent orange is 0.1-5% based on the thickness of the second emitting layer. Is formed. In such a ratio, the phosphorescent yellow dopant and the fluorescent orange dopant are co-depositioned to one host and formed in the second emission layer. Accordingly, blue light emitted from the first light emitting layer 136 and orange light emitted from the second light emitting layer 154 are mixed to realize white light.

As shown in FIG. 4A, a first light emitting layer 136 doped with a fluorescent normal blue dopant in one host and a second light emitting layer 154 doped with a phosphorescent yellow dopant and a fluorescent orange dopant in one host may be formed. 4B, a first light emitting layer 136 doped with a phosphorescent yellow dopant and a fluorescent orange dopant in one host, and a second light emitting layer 154 doped with a fluorescent normal blue dopant in one host. can do. Accordingly, orange light is emitted from the first light emitting layer 136, and blue light is emitted from the second light emitting layer 154 to implement white light. In addition, the dopant concentration and the wavelength range are the same as described in Figure 4a and will be omitted.

The foregoing description is merely illustrative of the present invention, and various modifications may be made by those skilled in the art without departing from the spirit of the present invention. Accordingly, the embodiments disclosed in the specification of the present invention are not intended to limit the present invention. The scope of the present invention should be construed according to the following claims, and all the techniques within the scope of equivalents should be construed as being included in the scope of the present invention.

100 substrate 110: first electrode
112: hole injection layer 114: hole transport layer
116: electron transport layer 118: electron injection layer
119: second electrode 122: first light emitting layer
124: second light emitting layer 126: interlayer organic layer
130: first stack 132: first hole injection layer
134: first hole transport layer 136: first light emitting layer
138: first electron transport layer 140: charge generating layer
142: N type organic layer 144: P type organic layer
150: second stack 152: second hole transport layer
154: second emission layer 156: second electron transport layer
158: electron injection layer

Claims (8)

First and second electrodes opposed to each other on a substrate;
A first light emitting layer formed between the first electrode and the second electrode and doped with a fluorescent normal blue dopant having a wavelength range of 460 nm to 465 nm in one host;
A white organic light emitting layer including a phosphorescent yellow dopant formed on the first emission layer or under the first emission layer and doped with a phosphorescent yellow dopant having a wavelength range of 560 nm to 570 nm and a fluorescent orange dopant having a wavelength range of 570 nm to 580 nm device. The organic light emitting diode of claim 1, further comprising a hole injection layer and a hole transport layer between the first light emitting layer and the first electrode, and further comprising an electron transport layer and an electron injection layer between the second light emitting layer and the second electrode. device. According to claim 1, wherein the doping ratio of the phosphorescent yellow is formed to 3 to 20% based on the thickness of the second light emitting layer, the doping ratio of the fluorescent orange is 0.1 to 5% based on the thickness of the second light emitting layer A white organic light emitting element formed of. The white organic light emitting diode of claim 3, wherein the second emission layer is formed by co-deposition of the phosphorescent yellow dopant and the fluorescent orange dopant in one host. The white organic light emitting device of claim 1, further comprising an interlayer organic layer between the first light emitting layer and the second light emitting layer to compensate an energy level between the first light emitting layer and the second light emitting layer. First and second electrodes opposed to each other on a substrate;
A first stack in which a hole injection layer, a first hole transport layer, a first light emitting layer, and a first electron transport layer are sequentially stacked between the first electrode and the second electrode;
A second stack in which a second hole transport layer, a second light emitting layer, a second electron transport layer, and an electron injection layer are sequentially stacked between the first stack and the second electrode;
A charge generation layer formed between the first stack and the second stack to control charge balance between the stacks;
The first light emitting layer is doped with a fluorescent normal blue dopant having a wavelength range of 460nm to 465nm in one host,
The second light emitting layer is a white organic light emitting device doped with a phosphorescent yellow dopant having a wavelength range of 560nm ~ 570nm and a fluorescent orange dopant having a wavelength range of 570nm ~ 580nm in one host. The method of claim 6, wherein the doping ratio of the phosphorescent yellow is formed to 3 to 20% based on the thickness of the second light emitting layer, the doping ratio of the fluorescent orange is 0.1 to 5% based on the thickness of the second light emitting layer A white organic light emitting element formed of. The white organic light emitting diode of claim 7, wherein the second emission layer is formed by co-deposition of the phosphorescent yellow dopant and the fluorescent orange dopant in one host.

Images