Organic light-emitting devices and displays

Abstract

The present application provides an organic light-emitting device and a display screen, which solves the problem of low light-emitting efficiency of organic light-emitting devices in the prior art. The organic light-emitting device includes a light-emitting layer, the light-emitting layer includes a host material and a guest material, the host material is mixed with a part of the guest material to form at least one mixed material layer, and the other part of the guest material constitutes at least one guest material layer.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor devices, and in particular to an organic light-emitting device and a display screen. Background Art

[0002] Organic light-emitting diodes (OLEDs) are gradually entering people's field of vision as a new generation of flat panel display technology. At present, in order to meet different needs, OLEDs have a variety of structures, and the more common ones are the use of two technical means: multilayer structure and host-guest doping system. Among them, the multilayer structure includes, for example, an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode. The host-guest doping system refers to a light-emitting layer that is a mixture of a host material and a guest material that is doped into the host material as a dopant, that is, each guest material molecule is surrounded by the host material, and the holes injected from the anode and the electrons injected from the cathode are compounded on the host material to form triplet and singlet excitons. The excitons transfer energy to the guest material. After the guest material is excited, its triplet or singlet state is unstable, and the excitons return from the excited state to the ground state and release photons to emit light. The performance of OLEDs with this structure has been significantly improved. However, how to further improve the luminous efficiency of OLEDs has always been one of the problems that technicians in this field continue to explore. Summary of the invention

[0003] In view of this, the embodiments of the present application provide an organic light-emitting device and a display screen to solve the problem of low light-emitting efficiency of OLED in the prior art.

[0004] In a first aspect, the present application provides an organic light-emitting device, including a light-emitting layer, the light-emitting layer including a host material and a guest material, the host material and part of the guest material are mixed to form at least one mixed material layer, and the other part of the guest material constitutes at least one guest material layer.

[0005] In one embodiment, the light-emitting layer includes a recombination zone, the relative exciton concentration in the recombination zone is not less than 20% of the highest relative exciton concentration in the light-emitting layer, and at least one guest material layer includes a first guest material layer, and the first guest material layer is located in the recombination zone.

[0006] In one embodiment, at least one mixed material layer includes a first mixed material layer and a second mixed material layer, the first mixed material layer, the first guest material layer and the second mixed material layer are stacked in sequence, and the thickness ratio of the first mixed material layer and the second mixed material layer is greater than or equal to 3:7 and less than or equal to 7:3.

[0007] In one embodiment, the main body material includes a first main body material and a second main body material, the first main body material is located in the first mixed material layer, and the second main body material is located in the second mixed material layer.

[0008] In one embodiment, the thickness of the first guest material layer is less than or equal to 1 / 80 of the sum of the thicknesses of the first mixed material layer and the second mixed material layer.

[0009] In one embodiment, the sum of the thicknesses of the first mixed material layer and the second mixed material layer is greater than or equal to 300 angstroms and less than or equal to 500 angstroms, and the thickness of the guest material layer is greater than or equal to 1 angstrom and less than or equal to 5 angstroms.

[0010] In one embodiment, the at least one guest material layer further includes a second guest material layer spaced apart from the first guest material layer, and the second guest material layer and the first guest material layer are respectively located at two side edge regions of the composite region.

[0011] In one embodiment, at least one mixed material layer includes a first mixed material layer, a second mixed material layer and a third mixed material layer, and the first mixed material layer, the first guest material layer, the second mixed material layer, the second guest material layer and the third mixed material layer are stacked in sequence.

[0012] In one embodiment, the host material is a premixed material of a P-type organic material and an N-type organic material, and the guest material is a phosphorescent material.

[0013] A second aspect of the present application provides a display screen, comprising an organic light-emitting device provided by any of the above embodiments.

[0014] According to the organic light-emitting device and display provided by the present application, by implementing part of the guest material in the light-emitting layer as at least one guest material layer, the molecular concentration of the guest material at the location of the guest material layer in the light-emitting layer is increased, thereby ensuring that the location of the guest material layer has a higher energy conversion efficiency and the energy conversion position is more concentrated, so that the guest material can convert as much energy transferred by the host material as possible into light energy, thereby improving the luminous efficiency of the organic light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic structural diagram of an organic light-emitting device provided in the first embodiment of the present application.

[0016] Figure 2 An embodiment of the present application provides Figure 1 The luminous efficiency curve of the organic light-emitting device shown.

[0017] Figure 3 An embodiment of the present application provides Figure 1 Lifetime curve of the organic light-emitting device shown.

[0018] Figure 4 A schematic structural diagram of an organic light-emitting device provided in the second embodiment of the present application.

[0019] Figure 5 A flow chart of a method for preparing an organic light-emitting device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0020] As described in the background art, the luminous efficiency of OLEDs using a multilayer structure and a host-guest doping system in the prior art needs to be further improved. The inventors found that by optimizing the position of the guest material in the light-emitting layer, implementing part of the guest material in the light-emitting layer as a guest material layer can further improve the luminous efficiency of the OLED. Based on this, the present application provides an organic light-emitting device and a display screen using the organic light-emitting device, which achieves the technical effect of improving the luminous efficiency of the OLED by implementing at least part of the guest material in the light-emitting layer as a guest material layer, that is, providing a guest material layer in the light-emitting layer, rather than forming a mixed material layer with all the guest materials and the host material.

[0021] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] Figure 1 This is a schematic diagram of the structure of an organic light-emitting device provided in the first embodiment of the present application. Figure 1 As shown, the organic light-emitting device 10 includes a first electrode layer, a hole injection layer, a hole transport layer, a light-emitting layer 11, an electron transport layer, an electron injection layer and a second electrode layer stacked in sequence. Among them, the first electrode layer is, for example, an anode, and the second electrode layer is, for example, a cathode. The light-emitting layer 11 includes a host material and a guest material, the host material and part of the guest material are mixed to form at least one mixed material layer, and the other part of the guest material constitutes at least one guest material layer 111. In this case, the light-emitting layer 11 includes a guest material layer 111, and a mixed material layer 112 composed of the host material and the guest material. The number of each film layer and the positional relationship between the film layers can be reasonably set according to actual needs. Among them, the guest material layer 111 refers to a film layer formed by a guest material, the host material layer refers to a film layer formed by a host material, and the mixed material layer 112 refers to a mixed material film layer formed by the guest material being doped into the host material in the form of an impurity.

[0023] For example, Figure 1As shown, the organic light-emitting device 10 includes a first guest material layer 111, a first mixed material layer 1121 and a second mixed material layer 1122, and the first mixed material layer 1121, the first guest material layer 111 and the second mixed material layer 1122 are stacked in sequence, that is, the light-emitting layer 11 includes one guest material layer 111 and two mixed material layers 112, and the two side surfaces of the guest material layer 111 are covered by the mixed material layer 112.

[0024] The energy level of the host material is greater than that of the guest material, so that the singlet and triplet exciton energies of the host material can be effectively transferred to the guest material. At the same time, the emission spectrum of the host material overlaps greatly with the absorption spectrum of the guest material, reducing the quenching effect of the host material on the exciton energy of the guest material. The guest material is used to receive the energy of the host material and convert the energy into light energy. The host material and the guest material can be selected from any one of a phosphorescent material, a fluorescent material or a thermally delayed fluorescent material.

[0025] The main material includes one material or multiple materials. When the main material includes multiple materials, the multiple materials can be arranged in layers, that is, different main materials are located in different layers, and the same layer only contains one main material; the multiple materials can also form a mixed material.

[0026] The guest material includes one material or multiple materials. When the guest material includes multiple materials, the multiple materials can be arranged in layers, that is, different guest materials are located in different layers, and the same layer contains only one guest material; the multiple materials can also form a mixed material.

[0027] According to the organic light-emitting device provided in this embodiment, by implementing part of the guest material in the light-emitting layer 11 as at least one guest material layer 111, the molecular concentration of the guest material at the position where the guest material layer 111 is located in the light-emitting layer is increased, thereby ensuring that the position where the guest material layer 111 is located has a higher energy conversion efficiency, and the energy conversion position is more concentrated, so that the guest material can convert the energy of the host material into light energy as much as possible, thereby improving the luminous efficiency of the organic light-emitting device. The improvement of the luminous efficiency, that is, the reduction of the current density at the corresponding brightness, so that the device life is improved and the power consumption of the OLED is reduced.

[0028] like Figure 1As shown, the light-emitting layer 11 includes a recombination region Q, and the relative exciton concentration of the recombination region Q is not less than 20% of the highest relative exciton concentration in the light-emitting layer 11, that is, the exciton energy is mainly concentrated in the recombination region Q. The recombination region Q is located at any position of the light-emitting layer 11, for example, in the first mixed material layer 1121, in the second mixed material layer 1122, in the first guest material layer, partially located in the first mixed material layer 1121 and the rest located in the first guest material layer, partially located in the second mixed material layer 1122 and the rest located in the first guest material layer, etc. In one embodiment, the guest material layer 111 is located in the recombination region Q. Since the exciton energy is mainly concentrated in the recombination region Q, by arranging the guest material layer 111 to be located in the recombination region Q, it can be ensured that more energy is transferred to the guest material, further improving the energy conversion efficiency, thereby improving the luminous efficiency of the organic light-emitting device.

[0029] Figure 2 An embodiment of the present application provides Figure 1 The luminous efficiency curve of the organic light-emitting device shown. Figure 3 An embodiment of the present application provides Figure 1 The life curve of the organic light-emitting device shown in the figure is as follows. The life of the organic light-emitting device is measured by the percentage of brightness decay within the same time. During the test, the main material selected is a pre-mixed material of a P-type organic material and an N-type organic material, and the guest material is a green phosphorescent material with a doping ratio of 6%-14%. In this case, in the direction from the first electrode layer to the second electrode layer, the light-emitting layer 11 is divided into 10 equal parts, and positions 0, 1, 3, 5, 7, 9, and 10 are selected as the insertion positions of the guest material layer 111, respectively, to obtain seven types of OLEDs. The test results show that the luminous efficiency of the seven types of OLEDs is approximately 100%, 102.5%, 109%, 110.4%, 111.3%, 105.9%, and 105.6%, respectively; the device life is approximately 96%, 95.5%, 97.8%, 97.2%, 97.2%, 97.2%, 97.2%, and 97.9%, respectively.

[0030] It can be seen that under the above test conditions, the OLEDs corresponding to positions 3, 5, and 7 as the insertion positions of the guest material layer 111 have high luminous efficiency and lifespan, and the thickness ratio of the first mixed material layer 1121 to the second mixed material layer 1122 is greater than or equal to 3:7 and less than or equal to 7:3, for example, the thickness ratio of the first mixed material layer 1121 to the second mixed material layer 1122 is 7:3, 6:4, 5:5, etc. The thickness mentioned here refers to the width in the direction from the first mixed material layer 1121 to the second mixed material layer 1122 (the same below).

[0031] In one embodiment, Figure 1As shown, the main body material includes different first main body materials and second main body materials, the first main body material is located in the first mixed material layer 1121, and the second main body material is located in the second mixed material layer 1122. For example, when the main body material is a pre-mixed material, the N-type organic material in the first main body material is different from the N-type organic material in the second main body material, or the P-type organic material in the first main body material is different from the P-type organic material in the second main body material, or the N-type organic material and the P-type organic material in the first main body material are different from the N-type organic material and the P-type organic material in the second main body material.

[0032] In one embodiment, the thickness of the guest material layer 111 is less than or equal to 1 / 80 of the sum of the thicknesses of the first mixed material layer 1121 and the second mixed material layer 1122. For example, the sum of the thicknesses of the first mixed material layer 1121 and the second mixed material layer 1122 is greater than or equal to 300 angstroms and less than or equal to 400 angstroms, and the thickness of the guest material layer 111 is greater than or equal to 1 angstrom and less than or equal to 5 angstroms. In one embodiment, the sum of the thicknesses of the first mixed material layer 1121 and the second mixed material layer 1122 is any one of 350 angstroms, 360 angstroms, 365 angstroms, and 370 angstroms, and the thickness of the guest material layer 111 is any one of 1 angstrom, 2 angstroms, 3 angstroms, 3.5 angstroms, and 4 angstroms. In this way, the guest material in the guest material layer 111 has little effect on the volume percentage of the guest material in the light-emitting layer 11, so there will be no problem of quenching due to excessive doping concentration.

[0033] Figure 4 This is a schematic diagram of the structure of an organic light-emitting device provided in the second embodiment of the present application. Figure 4 As shown, the organic light emitting device 20 and Figure 1 The difference of the organic light-emitting device 10 shown is that, in this embodiment, the number of guest material layers is two, and the two guest material layers are arranged at intervals and are located at the edge regions on both sides of the recombination region Q respectively.

[0034] Specifically, part of the guest material is distributed in the structure of the first guest material layer 2111 and the second guest material layer 2112, and the remaining guest material and the host material are distributed in the structure of the first mixed material layer 1121, the second mixed material layer 1122 and the third mixed material layer 1123. The first mixed material layer 1121, the first guest material layer 2111, the second mixed material layer 1122, the second guest material layer 2112 and the third mixed material layer 1123 are stacked in sequence. The composite region Q is composed of the first guest material layer 2111, the second mixed material layer 1122 and the second guest material layer 2112. In other examples, the composite region Q may also include part of the first mixed material layer 1121 and / or part of the third mixed material layer 1123.

[0035] In one embodiment, the spacing between the first guest material layer 2111 and the second guest material layer 2112, i.e., the thickness of the second mixed material layer 1122 is less than 70% of the sum of the thicknesses of the first mixed material layer 1121, the second mixed material layer 1122, and the third mixed material layer 1123, and is greater than or equal to 30% of the sum of the thicknesses. For example, the thickness of the second mixed material layer 1122 is 30 angstroms, 40 angstroms, 50 angstroms, etc.

[0036] The thickness of the first guest material layer 2111 and the second guest material layer 2112 may be equal or different. In one embodiment, the sum of the thickness of the first guest material layer 2111 and the second guest material layer 2112 is greater than or equal to 1 angstrom and less than or equal to 5 angstroms. In one embodiment, the ratio of the thickness of the first guest material layer 2111 to the second guest material layer 2112 is greater than or equal to 1:4 and less than or equal to 4:1.

[0037] According to the organic light-emitting device provided in this embodiment, by setting two guest material layers in the light-emitting layer, and setting the two guest material layers to be respectively located at the edge regions on both sides of the recombination region, the contact probability between the excitons and the guest material layers can be increased, thereby further improving the luminous efficiency of the organic light-emitting device.

[0038] To more clearly describe the technical solution of this application, refer to Figure 5 for Figure 1 The main flow chart of the preparation method of the organic light-emitting device 10 is shown in FIG. The preparation method comprises:

[0039] Step S510: forming a first mixed material layer on a pre-deposited substrate.

[0040] The pre-fabricated substrate includes a first electrode layer, such as an anode. In one embodiment, the pre-fabricated substrate also includes a substrate stacked with the first electrode layer and a hole injection layer, a hole transport layer, and an electron blocking layer stacked sequentially on a side of the first electrode layer away from the substrate.

[0041] The first mixed material layer refers to a film layer formed by a host material and a guest material doped as a dopant. The host material is, for example, a premixed material of a P-type organic material and an N-type organic material, and the guest material is, for example, a green phosphorescent material. In one embodiment, the first mixed material layer is formed on a pre-prepared substrate by a doping evaporation process.

[0042] Step S520 , forming a guest material layer on the first mixed material layer.

[0043] The guest material layer refers to a film layer formed by the guest material. For example, the guest material layer is formed on the first mixed material layer by an evaporation process.

[0044] Step S530, forming a second mixed material layer on the guest material layer. For example, the second mixed material layer is formed on the guest material layer by an evaporation process.

[0045] Step S540, forming a second electrode layer on the second mixed material layer to obtain an organic light-emitting device. The second electrode layer is, for example, a cathode. In one embodiment, before forming the second electrode layer, an electron transport layer, an electron injection layer, and a hole blocking layer are sequentially formed on the second mixed material layer, and then the second electrode layer is formed on the hole blocking layer.

[0046] The present application also provides a display screen, comprising the organic light-emitting device provided by any of the above embodiments.

[0047] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. An organic light-emitting device, characterized in that: The invention comprises a light-emitting layer, wherein the light-emitting layer comprises a main material and a guest material, wherein the main material is mixed with a part of the guest material to form at least one mixed material layer, and another part of the guest material constitutes at least one guest material layer, wherein the light-emitting layer comprises a recombination region, wherein the relative concentration of excitons in the recombination region is not less than 20% of the highest relative concentration of excitons in the light-emitting layer, and wherein the at least one guest material layer comprises a first guest material layer, and the first guest material layer is located in the recombination region.

2. The organic light-emitting device according to claim 1, characterized in that: The at least one mixed material layer includes a first mixed material layer and a second mixed material layer, the first mixed material layer, the first guest material layer and the second mixed material layer are stacked in sequence, and the thickness ratio of the first mixed material layer and the second mixed material layer is greater than or equal to 3:7 and less than or equal to 7:

3.

3. The organic light-emitting device according to claim 2, characterized in that: The main body material includes a first main body material and a second main body material, the first main body material is located in the first mixed material layer, and the second main body material is located in the second mixed material layer.

4. The organic light-emitting device according to claim 2, characterized in that: The thickness of the first guest material layer is less than or equal to 1 / 80 of the sum of the thicknesses of the first mixed material layer and the second mixed material layer.

5. The organic light-emitting device according to claim 1, characterized in that: The overall thickness of the light-emitting layer is greater than or equal to 300 angstroms and less than or equal to 500 angstroms; the thickness of the first guest material layer is greater than or equal to 1 angstrom and less than or equal to 5 angstroms.

6. The organic light-emitting device according to claim 1, characterized in that: The at least one guest material layer further includes a second guest material layer spaced apart from the first guest material layer, and the second guest material layer and the first guest material layer are respectively located at two side edge regions of the composite region.

7. The organic light emitting device according to claim 6, characterized in that: The at least one mixed material layer includes a first mixed material layer, a second mixed material layer and a third mixed material layer, and the first mixed material layer, the first guest material layer, the second mixed material layer, the second guest material layer and the third mixed material layer are stacked in sequence.

8. The organic light-emitting device according to any one of claims 1 to 7, characterized in that: The host material is a premixed material of a P-type organic material and an N-type organic material, and the guest material is a phosphorescent material.

9. A display screen, characterized in that: An organic light-emitting device comprising any one of claims 1 to 8.

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