WO2015192591A1 - Organic electroluminescence device and organic electroluminescence display apparatus - Google Patents

Abstract

An organic light emitting layer (4) used for an organic electroluminescence device, the organic electroluminescence device, and an organic electroluminescence display apparatus. The organic light emitting layer (4) comprises multiple areas existing in a stacking mode. Each area comprises a host material, a guest material for emitting light, and a dopant capable of adjusting a charge transportation capability of the host material. The amount of the dopant in the organic light emitting layer (4) increases or decreases in a gradient mode. The dopant with a gradient concentration is added to the organic light emitting layer (4) to enable electrons and holes to be combined and form excitons in wider areas of the organic light emitting layer (4), and therefore, the organic electroluminescence device and the organic electroluminescence display apparatus with optimized charge transportation capability and improved luminous efficiency are obtained, disadvantages such as impure color of emitted light and low luminous efficiency caused by an excessive or insufficient amount of the guest material in the host material are overcome, the mass percent of the guest material in the organic light emitting layer (4) has a larger adjusting range and a wider variety of options exist for the materials.

Description

Organic electroluminescent device, organic electroluminescent display device Technical field

The present invention belongs to the field of display technologies, and in particular, to an organic electroluminescence device and an organic electroluminescence display device including the organic electroluminescence device.

Background technique

Organic Light Emitting Diode (OLED) display device has many advantages such as all solid state, active illumination, fast response, high contrast, no viewing angle limitation, and flexible display. It is a kind developed in the middle of the 20th century. The new display technology is widely used in people's daily production and life. Although the current liquid crystal display is the most mainstream flat panel display, especially after the combination of thin film transistor technology, the response speed, brightness, contrast and lightness of the flat panel display have been greatly improved, but the liquid crystal display panel itself cannot In the case of illumination, it is necessary to use a backlight to illuminate the panel to emit light, and thus there is a limit, and no further improvement can be obtained. Therefore, the OLED display device will become the most ideal flat display device for the next generation. Its superior performance and huge market potential attract many manufacturers and scientific research institutions all over the world to invest in the production and research and development of OLED display devices.

The structure of the conventional organic electroluminescent device is as shown in FIG. 1. The anode layer 1, the hole injection layer 2, the hole transport layer 3, the organic light-emitting layer 4, and the electron transport layer 5 are sequentially disposed on the base substrate. Electron injection layer 6 and cathode layer 7. The organic light-emitting layer 4 includes a host material and a guest material for light emission. Under a certain voltage drive, electrons from the cathode and holes from the anode are injected into the electron transport layer 5 and the hole transport layer 3, respectively, and electrons and holes migrate to the organic layer through the electron transport layer 5 and the hole transport layer 3, respectively. The light-emitting layer meets in the organic light-emitting layer to form excitons, and the energy carried by the excitons is transferred from the host material to the guest material, so that the guest material molecules are excited, thereby achieving light emission.

Wherein, the host material as a charge transport material includes a hole transport type material and electricity The sub-transport type material is used to receive energy from the host material to achieve luminescence. For example, for red and green light guest materials, a phosphorescent guest material is often used, and the energy transfer from the host material to the guest material is obtained through the structural design of the host material and the guest material, thereby realizing the luminescence of the phosphorescent guest material. One advantage of phosphorescence is that all excitons formed in a single or triplet excited state (derived by electrons and holes recombined in the luminescent layer) can participate in luminescence. Since the energy of the lowest triplet excited state in organic molecules is slightly lower than the energy of the lowest singlet excited state, for most phosphorescent guest materials (phosphorescent organometallic compounds), singlet to triplet states can be realized. Rapid decay to achieve luminescence. The phosphorescent organic light-emitting layer (host material and guest material) is significantly more efficient than the fluorescent organic light-emitting layer (the host material is a fluorescent material, no guest material) (only 25% of the excitons can achieve light emission).

However, the proportion of the guest material (relative to the mass of the host material) has a great influence on the luminescence spectrum and the luminescence efficiency. When the mass fraction of the guest material is small, the energy of the host material cannot be completely transferred to the guest material. At this time, the host material itself is also There is a certain amount of energy remaining, causing the host material to emit light itself, and finally the spectrum of the light emitted by the organic electroluminescent device has a plurality of peaks, that is, the color of the light emitted by the organic electroluminescent device is impure. When the mass fraction of the guest material is high, exciton quenching occurs, which reduces the luminous efficiency.

Summary of the invention

The object of the present invention is to solve the problems of the organic electroluminescent device and the organic electroluminescent display device in the prior art, because the mass percentage of the guest material is too low or too high, resulting in impure color or low luminous efficiency of the device. The present invention provides an organic light-emitting layer for an organic electroluminescence device, thereby obtaining an organic electroluminescence device and an organic electroluminescence display device in which charge transport capability is optimized and luminous efficiency is improved.

In order to solve the technical problem of the present invention, the present invention provides the following technical solutions.

An aspect of the invention provides an organic light-emitting layer for an organic electroluminescence device, comprising a plurality of regions present in a stacked form, each region comprising a host material, a guest material for emitting light, and a codopant capable of increasing the luminosity of the device, wherein the dopant has a certain charge transporting ability, and the amount of the dopant is adjusted so that the doping amount thereof is The gradient or the gradient of the organic light-emitting layer is increased, so that the electron-transporting ability and the hole transporting ability of the organic light-emitting layer are equivalent.

In one embodiment of the invention, the host material is an electron transport type material, the dopant is a hole transport type material or an electron transport type material having an electron transport capability weaker than the host material.

In this embodiment, the dopant is used to improve the hole transporting ability of the host material by gradient doping such that the electron transporting ability of the host light emitting layer is comparable to its hole transporting ability.

In another embodiment of the present invention, the host material is a hole transporting type material, and the dopant is an electron transporting type material or a hole transporting material having a hole transporting ability weaker than the host material.

In this embodiment, the dopant is used to improve the electron transporting ability of the host material by gradient doping such that the electron transporting ability of the host material is comparable to its hole transporting ability.

Another aspect of the present invention provides an organic electroluminescence device comprising, in order, an anode layer, a hole injection layer, a hole transport layer, an organic light-emitting layer, an electron transport layer, an electron injection layer, and a cathode layer, the organic light-emitting layer The layer includes a host material, a guest material for illuminating, and a dopant for adjusting the ability of the host material to transport charge. Wherein the amount of the dopant increases in a gradient or a gradient in the organic light-emitting layer.

Preferably, the dopant is in a direction from a side where the organic light-emitting layer contacts the hole transport layer to a side where the organic light-emitting layer contacts the electron transport layer, the doping The doping concentration gradient of the dopant increases or the gradient decreases.

Preferably, the amount of the dopant increases linearly or linearly in the organic light-emitting layer.

Preferably, the hole transporting type material is selected from the group consisting of N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine ( NPB), any of 4,4'-bis(N-carbazole)-1,1'-biphenyl (CBP), 5,6,11,12-tetraphenyltetracene (Rubene).

Preferably, the electron transporting type material is selected from the group consisting of tris(8-hydroxyquinoline)aluminum (ALQ), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), any of 4,7-diphenyl-1,10-phenanthroline (Bphen).

Preferably, the dopant is in a mass percentage of the host material of 100%, and the mass percentage of the dopant is 0.1% to 30%, for example, 5% to 15%, or 5% to 30%.

Another aspect of the present invention provides an organic electroluminescence display device comprising the above-described organic electroluminescence device.

The organic electroluminescent device and the organic electroluminescence display device of the present invention have a doping agent for increasing the luminosity of the device in the organic light-emitting layer, and the doping concentration of the dopant in the host material is adjusted to make the The doping concentration changes in a gradient in the organic light-emitting layer, so that the electron-emitting ability and the hole transporting ability of the organic light-emitting layer are equivalent. For example, in the organic electroluminescent device, the concentration of the dopant in the organic light-emitting layer is linear or gradient in the direction from the interface of the electron transport layer/organic light-emitting layer to the interface of the hole transport layer/organic light-emitting layer. Distribution, such that the electron transporting ability of the organic light-emitting layer tends to decrease in the above direction, in which case carriers (electrons or holes) themselves have a gradient-changing concentration, so that electrons and holes can be organic Excitons are formed in a wider region of the luminescent layer, which overcomes the defects of impure color and low luminous efficiency due to too much or too little guest material in the host material; the mass percentage adjustment of the guest material of the organic luminescent layer The range is larger and the choice of materials is wider.

DRAWINGS

1 is a schematic view showing the structure of an organic electroluminescent device.

among them:

1. An anode layer; 2. A hole injection layer; 3. A hole transport layer; 4. An organic light-emitting layer; 5. An electron transport layer; 6. An electron injection layer; 7. A cathode layer.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The organic light-emitting layer for an organic electroluminescence device of the present invention includes a stacked shape A plurality of regions exist in the form, for example, 2, 3 or more regions. Wherein each region comprises a host material, a guest material for emitting light, and a dopant for increasing the luminosity of the device, wherein the amount of the dopant increases or gradients in the organic light-emitting layer. decline.

In one embodiment, the host material is a hole transporting type material, and the dopant is an electron transporting type material or a hole transporting material having a hole transporting ability weaker than the host material.

In this embodiment, the dopant is used to improve the electron transporting ability of the host material such that the electron transporting ability of the host material is comparable to the hole transporting ability.

For example, in the embodiment where the host material is a hole transport type material (ie, the electron transporting ability of the host material is weak), a dopant capable of improving the electron transporting ability of the host material (ie, an electron transporting material, or an empty space) should be selected. The hole transporting ability is weaker than the hole transporting material of the host material, so that the electron transporting ability of the host material is equivalent to the hole transporting ability.

Alternatively, in another embodiment, the host material is an electron transport type material, and the dopant is a hole transport type material or an electron transport material having an electron transport capability weaker than the host material;

In this embodiment, the dopant is used to improve the hole transporting ability of the host material such that the electron transporting ability of the host material is comparable to the hole transporting ability.

For example, in the case where the host material is an electron transport type material (ie, its hole transporting ability is weak), in this case, a dopant capable of improving the hole transporting ability of the host material should be selected (ie, The hole transporting type material or the electron transporting type material having a weaker electron transporting ability than the host material makes the hole transporting ability of the host material comparable to the electron transporting ability.

Preferably, the doping concentration of the dopant increases or decreases from a side where the organic light-emitting layer contacts the hole transport layer to a side where the organic light-emitting layer contacts the electron transport layer.

Preferably, the hole transporting type material is selected from the group consisting of N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), 4,4'-bis(N-carbazole)-1,1'-biphenyl (CBP), 5,6,11,12-tetraphenyltetracene (Rubene) .

Preferably, the electron transporting type material is selected from the group consisting of tris(8-hydroxyquinoline)aluminum (ALQ), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), any of 4,7-diphenyl-1,10-phenanthroline (Bphen).

Preferably, the amount of the dopant is from 0.1% to 30%, for example from 5% to 15%, or from 5% to 30%, based on 100% by mass of the mass of the host material.

Another aspect of the present invention provides an organic electroluminescence device comprising an anode layer, a hole injection layer, a hole transport layer, the organic light-emitting layer, the electron transport layer, the electron injection layer, and the cathode layer of the present invention .

The organic light emitting layer includes a host material, a guest material for emitting light, and a dopant for adjusting a charge transporting ability of the host material.

Preferably, the amount of the dopant in the organic light-emitting layer increases linearly or linearly, or the gradient increases or the gradient decreases.

Another aspect of the present invention provides an organic electroluminescence display device comprising the above-described organic electroluminescence device.

The organic electroluminescent display device of the present invention may be any product or component having an display function such as an OLED panel, a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator, and the like.

The present invention provides an organic electroluminescent device comprising an anode layer 1, a hole injection layer 2, a hole transport layer 3, an organic light-emitting layer 4, an electron transport layer 5, an electron injection layer 6, and a cathode layer 7, the organic The luminescent layer includes a host material, a guest material for illuminating, and the organic luminescent layer 4 further includes a dopant for improving the luminous efficiency of the device.

In the art, an organic light-emitting layer generally comprises a host material and a guest material, and the charge transporting ability exhibited by the organic light-emitting layer mainly depends on the charge transporting ability of the host material, and the guest material is mainly used for light emission.

Therefore, in the present invention, the dopant for the organic light-emitting layer functions to adjust the charge transporting ability of the host material, thereby improving the charge transporting ability of the organic light-emitting layer.

The organic electroluminescent device of the present invention has substantially the same overall structure as the prior art, except that the organic light-emitting layer includes a host material, a guest material for emitting light, and a device for improving luminous efficiency (for example, luminosity) of the device. Dopant.

The present invention adjusts the charge transporting behavior of the organic light-emitting layer by adding a dopant for adjusting the charge transporting ability of the host material in the organic light-emitting layer, so that electrons and holes can be compounded in a wider region of the organic light-emitting layer. The formation of excitons overcomes the disadvantages of excessive or too little luminescent color of the guest material in the host material, and the luminous efficiency is not high; the mass percentage of the guest material of the organic luminescent layer is adjusted to a greater extent, and the material selection range is more wide.

Preferably, the doping concentration of the dopant increases or decreases along a direction from a side where the organic light-emitting layer contacts the hole transport layer to a side where it contacts the electron transport layer.

By adjusting the mass percentage of the dopant in different regions of the organic light-emitting layer, thereby adjusting the charge transporting ability of the organic light-emitting layer, excitons can be formed in a wider region of the organic light-emitting layer.

Preferably, the amount of the dopant in the organic light-emitting layer increases linearly or linearly, or the gradient increases or the gradient decreases.

Preferably, the host material is an electron transport type material, and the dopant is a hole transport type material; or

The host material is a hole transport type material, and the dopant is an electron transport type material.

The choice of the material type of dopant depends primarily on the weaker transmission properties of the host material.

For example, when the host material is an electron transport type material, such a host material has a weak hole transporting ability. Thus, in order to make the electron transporting ability and the hole transporting ability of the host material substantially equivalent, it is possible to use a dopant having a weaker electron transporting ability than the host material, or a dopant having a hole transporting ability stronger than that of the host material. In order to improve the hole transporting ability of the host material.

Similarly, when the host material is a hole transport type material, such host material has a weak electron transporting ability. Thus, in order to make the electron transporting ability and the hole transporting ability of the host material substantially equivalent, a dopant having a hole transporting ability weaker than the host material or a dopant having a higher electron transporting ability than the host material may be used. To improve the electron transport capability of the host material.

Without wishing to be bound by any theory, it is believed that in the case where the host material is an electron transport type material, the electron transporting ability of the host material is much greater than its hole transporting ability when the dopant is not doped, and thus, it is easy to Excitons are formed at the interface close to the organic light-emitting layer/hole transport layer, and the regions where the excitons are recombined are small. In this case, excitons are liable to be quenched by interaction with the hole transporting material of the hole transporting layer.

In this case, by incorporating a dopant of a hole-transporting material having a gradient in the organic light-emitting layer, an energy level step is provided for the organic light-emitting layer, which is advantageous for the energy carried by the excitons. Transmitting from the host material to the guest material, and because the dopant is a hole transporting material, the hole transporting ability is stronger than the hole transporting ability of the host material, thereby enhancing the overall hole transporting ability of the organic light emitting layer, thereby It is possible to recombine electrons and holes in a wider region of the organic light-emitting layer and form excitons.

Preferably, the hole transporting type material is selected from the group consisting of N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine ( NPB), any of 4,4'-bis(9-carbazole)biphenyl (CBP) and 5,6,11,12-tetraphenyltetradecene (Rubrene).

Preferably, the electron transporting type material is selected from the group consisting of tris(8-hydroxyquinoline)aluminum (Alq ₃ ), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), any of 4,7-diphenyl-1,10-phenanthroline (Bephen).

Preferably, the mass percentage of the dopant is from 0.1% to 30%, for example from 5% to 15%, or from 5% to 30%, based on 100% by mass of the mass of the host material.

In the following examples, the amount of the components is in mass%. The compounds listed in the present application and examples are all commercially available products.

For convenience of reference, the chemical names and structural formulas of the organic compounds referred to in the present application are as follows:

Example 1

As shown in FIG. 1, the present embodiment provides an organic electroluminescent device comprising an anode layer 1, a hole injection layer 2, a hole transport layer 3, an organic light-emitting layer 4, an electron transport layer 5, an electron injection layer 6, and A cathode layer 7, which includes a host material, a guest material for emitting light, and the organic light-emitting layer 4 further includes a dopant for adjusting a charge transporting ability of the host material.

The structure of the red organic light emitting layer in this embodiment is as follows:

The dopant rubrene is divided into three regions from the interface of the hole transport layer 3/organic light-emitting layer 4 to the end of the interface of the electron transport layer 5/organic light-emitting layer 4, in which the doping The mass percentage of the ruber rubrene increases with a certain gradient.

Specifically, the red organic electroluminescent device has the following layer structure: ITO (150 nm) / CuPc (40 nm) / NPB (40 nm) / Alq ₃ (100%): rubrene (5%): DCJTB (2%) (15 nm) /Alq ₃ (100%): rubrene (10%): DCJTB (2%) (15 nm) / Alq ₃ (100%): rubrene (15%): DCJTB (2%) (15 nm) / Alq ₃ (40 nm) /LiF (1 nm) / Al (120 nm).

Wherein, ITO (150 nm) is indium tin oxide as an anode layer; CuPc (40 nm) is copper phthalocyanine as a hole injection layer; NPB (40 nm) is a hole transport layer, and Alq ₃ (40 nm) is an electron transport layer; LiF ( 1 nm) is lithium fluoride as an electron injecting layer; Al (120 nm) is used as a cathode layer. "/" indicates the interface between layers and layers, and the numerical value in nm in parentheses indicates the thickness of the layer or region.

The host material of the organic light-emitting layer 4 is Alq ₃ , the guest material is DCJTB, and the dopant is rubrene.

The organic light-emitting layer 4 has three regions in a stacked form, respectively "Alq ₃ (100%): rubrene (5%): DCJTB (2%) (15 nm)", "Alq ₃ (100%): rubrene ( 10%): DCJTB (2%) (15 nm)" and "Alq ₃ (100%): rubrene (15%): DCJTB (2%) (15 nm)".

Obviously, in these three regions, the mass percentage of the dopant rubrene is divided into three gradients: 5 wt%, 10 wt%, 15 wt%, which are incremental.

The application of these layers is carried out by a conventional evaporation method, and the resulting thickness and amount of each component are achieved by controlling the corresponding parameters in the evaporation method.

In the embodiment, the host material Alq ₃ is an electron transport type material, and its hole transporting ability is weak, and the hole transporting ability of the dopant rubrene is stronger than that of Alq ₃ , in order to make the host material Alq ₃ electron transport and hole transport capabilities equivalent to set the doping concentration gradient described above, thereby improving the balance of hole transport capability and electron transport capabilities of the host material Alq _3.

The hole transporting ability of the host material is enhanced by adding a dopant rubrene, so that the obtained organic light-emitting layer exhibits a balance of charge transporting ability, that is, electron transporting ability and hole transporting ability, thereby improving luminous efficiency.

The luminance and current of the red organic electroluminescent device of the present embodiment were measured (luminance meter PR680L and current voltmeter kathely), and the obtained luminescence ratio was 5 cd/A. At the same time, the luminosity of the red organic electroluminescent device which is the same but not doped rubene is measured to be less than 2 cd/A. Obviously, the organic light doped with rubrene is compared with the case of undoped rubrene. The luminous efficiency of the electroluminescent device is more than doubled.

Example 2

This embodiment provides an organic electroluminescent device having a layer structure similar to that of Embodiment 1, but the specific conditions of each layer are as follows:

ITO (150 nm) / fluorocarbon (1 nm) / NPB (120 nm) / Alq ₃ (100%): NPB (5%): C545T (1%) (10 nm) / Alq ₃ (100%): NPB (10%) : C545T (1%) (10 nm) / Alq ₃ (100%): NPB (30%): C545T (1%) (10 nm) / Alq ₃ (40 nm) / LiF (1 nm) / Al (120 nm).

Wherein, the organic light-emitting layer in this embodiment has three regions laminated, respectively, "Alq ₃ (100%): NPB (5%): C545T (1%) (10 nm)""Alq ₃ (100%): NPB (10%): C545T (1%) (10 nm)" and "Alq ₃ (100%): NPB (30%): C545T (1%) (10 nm)"; wherein the host material is an electron transporting material Alq ₃ The guest material is C545T, and the dopant is a hole transport type material NPB. In these three regions, the mass percentage of the dopant NPB is divided into three gradients, 5 wt%, 10 wt%, and 30 wt%.

The luminance and current of the NPB-doped red organic electroluminescent device of this example were measured in the same manner as in Example 1, and it was found that the luminosity was 8.5 cd/A or more. Further, the luminance and current of the device which was the same as the red organic electroluminescent device of the present embodiment but was not doped with NPB were measured, and it was found that the luminosity was less than 7.0 cd/A. Obviously, the luminosity of the organic electroluminescent device is significantly improved after doping with NPB.

Example 3

The present embodiment provides an organic electroluminescence display device which is assembled by using the organic electroluminescence device described in Embodiment 1.

It is to be understood that the above embodiments are merely exemplary embodiments employed to explain the principles of the invention, but the invention is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and scope of the invention. These modifications and improvements are also considered to be within the scope of the invention.

Claims (11)

An organic light-emitting layer for an organic electroluminescent device, comprising a plurality of regions in a stacked form, each region comprising a host material, a guest material for emitting light, and an ability to adjust a charge transfer of the host material a dopant, wherein the amount of the dopant increases in a gradient or a gradient in the organic light-emitting layer. The organic light-emitting layer according to claim 1, wherein the host material is an electron transport type material, the dopant is a hole transport type material or electron transport capability is weaker than electron transport of the host material Type of material. The organic light-emitting layer according to claim 2, wherein the dopant is for improving hole transporting ability of the host material such that the electron transporting ability of the host material is comparable to its hole transporting ability. The organic light-emitting layer according to claim 1, wherein the host material is a hole transport type material, the dopant is an electron transport type material or the hole transporting ability is weaker than the host material Hole transport material. The organic light-emitting layer according to claim 4, wherein the dopant is for improving electron transporting ability of the host material such that the electron transporting ability of the host material is comparable to its hole transporting ability. The organic light-emitting layer according to any one of the preceding claims, wherein the amount of the dopant is from 0.1% by mass to 30% by mass based on 100% by mass of the host material. The organic light-emitting layer according to any one of the preceding claims, wherein the hole transporting type material is selected from the group consisting of N,N'-diphenyl-N,N'-(1-naphthyl)-1,1' - any of biphenyl-4,4'-diamine, 4,4'-bis(N-carbazole)-1,1'-biphenyl, 5,6,11,12-tetraphenyltetracene One. The organic light-emitting layer according to any one of the preceding claims, wherein the electron transporting type material is selected from the group consisting of tris(8-hydroxyquinoline)aluminum, 1,3,5-tris(1-phenyl-1H-benzene Any one of imidazol-2-yl)benzene and 4,7-diphenyl-1,10-phenanthroline. An organic electroluminescent device, comprising: An anode layer, a hole injection layer, a hole transport layer, the organic light-emitting layer according to any one of claims 1 to 8, an electron transport layer, an electron injection layer, and a cathode layer. The organic electroluminescent device according to claim 9, wherein a direction from a side where the organic light-emitting layer contacts the hole transport layer to a side where the electron transport layer is in contact with, The doping concentration gradient of the dopant contained in the organic light-emitting layer is increased or the gradient is decreased. An organic electroluminescence display device comprising the organic electroluminescent device according to any one of claims 9-10.

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