An organic light emitting device and display apparatus

Abstract

The application relates to an organic light-emitting device and a display device, the organic light-emitting device comprising an anode layer and a cathode layer arranged oppositely, a first light-emitting layer and a second light-emitting layer stacked and arranged in close contact between the anode layer and the cathode layer, the first light-emitting layer being located on a side of the second light-emitting layer close to the anode layer; the material of the first light-emitting layer comprising a first host material, the material of the second light-emitting layer comprising a second host material, the first host material and the second host material satisfying the size relationship of HOMO energy levels, LUMO energy levels and hole mobility shown in formulas (1) to (3), and the formulas (1) to (3) not taking equal signs at the same time. The application can realize the separation of the triplet-triplet fusion process and the hole-electron recombination process to form an exciton, thereby being beneficial to reducing the triplet exciton quenching caused by the excessively large carrier concentration, and further being beneficial to significantly improving the light-emitting efficiency and service life of the organic light-emitting device.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to an organic light-emitting device and a display apparatus. Background Technology

[0002] In recent years, Organic Light Emitting Diode (OLED) display technology has gradually attracted more attention. Due to its characteristics such as active light emission, high brightness, high resolution, wide viewing angle, fast response speed, color saturation, thinness, low power consumption, and flexibility, it is hailed as the dream display and has become a popular mainstream display product in the current market.

[0003] Currently, in blue OLED devices, triplet-polaron quenching (TPQ) caused by excess carriers in the emissive layer makes it difficult to achieve the theoretical internal quantum efficiency of 62.5%. Device efficiency can typically be improved by compressing the recombination region of the emissive layer or by selecting high-efficiency blue fluorescent guest materials. However, progress in improving efficiency through high-efficiency blue fluorescent guest materials is slow and difficult to iterate; while compressing the recombination region leads to a severe trade-off between device efficiency and lifetime, which is detrimental to meeting the requirements for high white light efficiency and long lifetime OLED panels. Summary of the Invention

[0004] This application provides an organic light-emitting device and a display device that can separate the triplet-triplet fusion process from the hole-electron recombination process to form excitons. This helps to reduce triplet exciton quenching caused by excessive carrier concentration, and thus significantly improves the luminous efficiency and lifespan of the organic light-emitting device.

[0005] To achieve the above objectives, according to a first aspect of this application, an organic light-emitting device is provided, comprising:

[0006] Anode layer;

[0007] A cathode layer is disposed opposite to the anode layer;

[0008] At least one light-emitting unit is disposed between the anode layer and the cathode layer; the at least one light-emitting unit includes a first light-emitting layer and a second light-emitting layer stacked and attached together, the first light-emitting layer being located on the side of the second light-emitting layer closer to the anode layer; the material of the first light-emitting layer includes a first main material, the material of the second light-emitting layer includes a second main material, the first main material and the second main material satisfy the size relationship shown in equations (1) to (3), and equations (1), (2) and (3) are not simultaneously equal:

[0009] |HOMO Host1 |≥|HOMO Host2 | (1);

[0010] |LUMO Host1 |≤|LUMO Host2 | (2);

[0011] μ Host1 ≤μ Host2 (3);

[0012] Among them, HOMO Host1 and HOMO Host2 LUMO represents the highest occupied molecular orbital energy levels of the first and second host materials, respectively. Host1 and LUMO Host2 μ represents the lowest unoccupied molecular orbital energy levels of the first host material and the second host material, respectively. Host1 and μ Host2 These represent the hole mobility rates of the first and second main materials, respectively.

[0013] According to a second aspect of this application, a display device is provided, the display device comprising the organic light-emitting device described above.

[0014] In the organic light-emitting device and display device of this application embodiment, at least one light-emitting unit in the organic light-emitting device is composed of a first light-emitting layer and a second light-emitting layer stacked and bonded together. The first light-emitting layer is disposed near the anode layer, and the second light-emitting layer is disposed near the cathode layer. When the first host material (Host1) in the first light-emitting layer has a deeper HOMO energy level than the second host material (Host2) in the second light-emitting layer, the injection barrier when holes provided by the anode layer enter the first light-emitting layer increases, thereby slowing down the hole injection rate. This is beneficial for electrons and holes to recombine and form excitons on the side of the first light-emitting layer away from the second light-emitting layer. When the second host material in the second light-emitting layer has a deeper LUMO energy level than the first host material in the first light-emitting layer, electrons provided by the cathode layer are more easily injected from the second light-emitting layer into the first light-emitting layer. This is beneficial for electrons and holes to recombine and form excitons on the side of the first light-emitting layer away from the second light-emitting layer. When the hole mobility μ of the first host material in the first light-emitting layer... Host1 The hole mobility μ of the second host material in the second light-emitting layer is less than that in the second light-emitting layer. Host2 At this time, the hole transport rate in the first light-emitting layer is relatively small, which increases the difference between the hole and electron transport rates in the first light-emitting layer. This makes the electron transport rate in the first light-emitting layer even greater than the hole transport rate, which is conducive to the recombination of electrons and holes on the side of the first light-emitting layer away from the second light-emitting layer to form excitons.

[0015] Therefore, when the first host material of the first light-emitting layer and the second host material of the second light-emitting layer satisfy any one or more of the magnitude relationships shown in equations (1) to (3), and equations (1), (2) and (3) are not simultaneously equal, electrons and holes can recombine on the side of the first light-emitting layer away from the second light-emitting layer to form excitons. Furthermore, a large number of excitons can be transferred to the second light-emitting layer, thus separating the triplet-triplet fusion process from the hole-electron recombination process to form excitons. This helps to reduce the triplet exciton quenching caused by excessive carrier concentration, and thus significantly improves the luminous efficiency and lifespan of organic light-emitting devices.

[0016] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0019] Figure 1 This is a schematic diagram of the structure of an organic light-emitting device provided in an embodiment of this application;

[0020] Figure 2 This is a schematic diagram of carrier migration in an organic light-emitting device provided in an embodiment of this application;

[0021] Figure 3 This is a schematic diagram of carrier migration for another organic light-emitting device provided in an embodiment of this application;

[0022] Figure 4 This is a schematic diagram of the structure of a display device provided in an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures: 1. Organic light-emitting device; 2. Anode layer; 3. Cathode layer; 4. Light-emitting unit; 5. First light-emitting layer; 6. Second light-emitting layer; 7. Hole transport layer; 8. Hole injection layer; 9. Electron transport layer; 10. Electron injection layer; 11. Display device; 12. Array substrate; 13. Encapsulation layer; A. Exciton recombination region; B. Exciton utilization region. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0025] In organic electroluminescence, when a voltage is applied to the anode and cathode layers, singlet and triplet excitons are generated in the luminescent layer. Traditional fluorescent materials can only utilize singlet excitons for luminescence, with a theoretical upper limit of 25% for internal quantum efficiency. However, triplet-triplet annihilation (TTA) type blue light-emitting host materials can utilize triplet excitons. Through the TTA process, two triplet excitons interact and annihilate, producing a singlet exciton and a ground-state molecule. The generated singlet exciton can emit light, theoretically increasing the exciton utilization rate to 62.5%, thereby improving the luminescence efficiency.

[0026] However, in conventional blue OLED devices, the carrier recombination region and the triplet-triplet fusion (TTF) region in the emitting layer are not separated. Excessive carriers will quench the triplet excitons (TPQ), making it difficult for the internal quantum efficiency of blue OLED devices to reach the theoretical value of 62.5%, which in turn results in low luminous efficiency and short lifetime of the devices.

[0027] To simultaneously improve the luminous efficiency and lifespan of organic light-emitting devices (OLEDs), this application improves the structure of the OLED's emissive layer by transforming the conventional single-layer emissive layer into a double-layer emissive layer. Furthermore, different host materials are selected for the two emissive layers. By controlling the relationship between the highest occupied molecular orbital (HOMO) level, the lowest unoccupied molecular orbital (LUMO) level, and the hole mobility μ of the host materials of the two emissive layers, the injection and transport rates of holes and electrons are regulated. This allows for the separation of the region where holes and electrons recombine to form excitons (also known as the exciton recombination region) from the TTF region (also known as the exciton utilization region), thereby reducing triplet exciton quenching caused by excessive carrier concentration and significantly improving the luminous efficiency and lifespan of the OLED. See the following description of specific embodiments.

[0028] like Figure 1As shown, this application provides an organic light-emitting device 1, which includes an anode layer 2 and a cathode layer 3 disposed opposite to each other, and at least one light-emitting unit 4 disposed between the anode layer 2 and the cathode layer 3. At least one light-emitting unit 4 includes a first light-emitting layer 5 and a second light-emitting layer 6 stacked and bonded together. The first light-emitting layer 5 is located on the side of the second light-emitting layer 6 closer to the anode layer 2. That is, at least one light-emitting unit 4 has a double-layer light-emitting structure, with the first light-emitting layer 5 disposed closer to the anode layer 2 and the second light-emitting layer 6 disposed closer to the cathode layer 3.

[0029] It is understandable that the first light-emitting layer 5 and the second light-emitting layer 6 are in direct contact and are stacked together to form a double-layer light-emitting structure.

[0030] The material of the first light-emitting layer 5 includes a first host material (Host1), and the material of the second light-emitting layer 6 includes a second host material (Host2). The first host material and the second host material satisfy the magnitude relationship shown in equations (1) to (3), and equations (1), (2), and (3) do not simultaneously hold the equality sign:

[0031] |HOMO Host1 |≥|HOMO Host2 | (1);

[0032] |LUMO Host1 |≤|LUMO Host2 | (2);

[0033] μ Host1 ≤μ Host2 (3);

[0034] Among them, HOMO Host1 and HOMO Host2 LUMO represents the highest occupied molecular orbital energy levels of the first and second host materials, respectively. Host1 and LUMO Host2 μ represents the lowest unoccupied molecular orbital energy levels of the first and second host materials, respectively. Host1 and μ Host2 These represent the hole migration rates of the first and second main materials, respectively.

[0035] It is understandable that, according to equation (1), the first luminescent material has the same or deeper HOMO energy level compared with the second host material; according to equation (2), the second host material has the same or deeper LUMO energy level compared with the first host material; according to equation (3), the hole transmission rate in the first luminescent layer 5 is less than or equal to the transmission rate in the second luminescent layer 6.

[0036] It should be noted that the aforementioned deeper HOMO energy level refers to the HOMO energy level of organic materials having a larger absolute value, and the aforementioned deeper LUMO energy level refers to the LUMO energy level of organic materials having a larger absolute value.

[0037] In one specific embodiment, the first light-emitting layer 5 and the second light-emitting layer 6 emit light of the same color.

[0038] It should be noted that when multiple light-emitting units 4 are connected in series between the anode layer 2 and the cathode layer 3, at least one of the light-emitting units 4 is a double light-emitting layer. That is, when there are multiple light-emitting units 4 in the organic light-emitting device 1, some of the light-emitting units 4 are double light-emitting layers, and the other part of the light-emitting units 4 are single light-emitting layers; or, all the light-emitting units 4 are formed by stacking the first light-emitting layer 5 and the second light-emitting layer 6 as described in the embodiments of this application.

[0039] In this embodiment, at least one light-emitting unit 4 in the organic light-emitting device 1 is composed of a first light-emitting layer 5 and a second light-emitting layer 6 stacked and bonded together. The first light-emitting layer 5 is disposed near the anode layer 2, and the second light-emitting layer 6 is disposed near the cathode layer 3. The anode layer 2 provides holes to the first light-emitting layer 5, and the cathode layer 3 provides electrons to the second light-emitting layer 6. Unlike conventional single-layer light-emitting layers, the light-emitting layers provided in this embodiment are double-layer light-emitting layers that are in contact with each other and stacked together, and the main materials in the double-layer light-emitting layers are different.

[0040] When equation (1) is not equal, the first host material in the first light-emitting layer 5 has a deeper HOMO energy level than the second host material in the second light-emitting layer 6. The injection barrier when the hole provided by the anode layer 2 enters the first light-emitting layer 5 increases, thereby slowing down the hole injection rate. This is beneficial for electrons and holes to recombine and form excitons on the side of the first light-emitting layer 5 away from the second light-emitting layer 6.

[0041] When equation (2) is not equal, the second host material in the second light-emitting layer 6 has a deeper LUMO energy level than the first host material in the first light-emitting layer 5. Electrons provided by the cathode layer 3 are more easily injected from the second light-emitting layer 6 into the first light-emitting layer 5, which is conducive to the recombination of electrons and holes on the side of the first light-emitting layer 5 away from the second light-emitting layer 6 to form excitons.

[0042] When equation (3) does not hold the equality sign, the hole mobility μ of the first host material in the first light-emitting layer 5 Host1 The hole mobility μ of the second host material in the second light-emitting layer 6 is less than that in the second light-emitting layer 6. Host2 The hole transport rate in the first light-emitting layer 5 is relatively small, which increases the difference between the transport rates of holes and electrons in the first light-emitting layer 5. This makes the electron transport rate in the first light-emitting layer 5 even greater than the hole transport rate, which is conducive to the recombination of electrons and holes on the side of the first light-emitting layer 5 away from the second light-emitting layer 6 to form excitons.

[0043] Therefore, when the first host material of the first light-emitting layer 5 and the second host material of the second light-emitting layer 6 satisfy the magnitude relationship shown in equations (1) to (3), and equations (1), (2) and (3) are not simultaneously equal, electrons and holes can recombine on the side of the first light-emitting layer 5 away from the second light-emitting layer 6 to form excitons; and a large number of excitons can be transferred to the second light-emitting layer 6, so that the triplet-triplet fusion (TTF) process is separated from the hole-electron recombination process to form excitons, thereby helping to reduce the triplet exciton quenching caused by excessive carrier concentration, and thus significantly improving the luminous efficiency and lifespan of the organic light-emitting device 1.

[0044] It should be noted that, as Figure 2 and Figure 3 As shown, the process of hole-electron recombination to form excitons can be called the exciton recombination process, and the region where this process occurs is called the exciton recombination region A. The TTF process refers to the process of triplet excitons fusing to form singlet excitons, and the region where the TTF process occurs is called the TTF region, i.e., the exciton utilization region B. Therefore, in the organic light-emitting device 1 provided in this application embodiment, the exciton recombination region A and the exciton utilization region B are separated, which can reduce or avoid the collision between excess charge carriers in the exciton recombination region A and triplet excitons in the exciton utilization region B, resulting in triplet exciton annihilation, thereby improving the luminous efficiency and lifespan of the organic light-emitting device 1.

[0045] In a preferred embodiment, the first host material and the second host material satisfy the magnitude relationship shown in equations (1) to (3), and equations (1), (2), and (3) are not equal. In this case, the first host material has a deeper HOMO energy level, the second host material has a deeper LUMO energy level, and the hole mobility of the first host material is less than that of the second host material. This allows for maximum control of the exciton recombination region A to be located on the side of the first light-emitting layer 5 away from the second light-emitting layer 6, which is more conducive to achieving the separation of the exciton recombination region A and the exciton utilization region B, thereby more effectively improving the luminous efficiency and lifespan of the organic light-emitting device 1.

[0046] In some embodiments, the organic light-emitting device 1 further includes a hole transport layer 7 located on the side of the first light-emitting layer 5 near the anode layer 2, and the hole transport layer 7 is disposed adjacent to the first light-emitting layer 5. Electrons and holes recombine in the region near the interface between the hole transport layer 7 and the first light-emitting layer 5 to form excitons.

[0047] It is understood that the adjacent arrangement of the hole transport layer 7 and the first light-emitting layer 5 in the embodiments of this application means that the two are in direct contact.

[0048] In some embodiments, the hole transport layer 7 also has an electron blocking function, but is not limited thereto.

[0049] like Figure 2 As shown, when the HOMO energy level of the first host material of the first light-emitting layer 5 is comparable to the HOMO energy level of the second host material of the second light-emitting layer 6, the exciton recombination region A is confined to the region where the first light-emitting layer 5 is located, and the exciton utilization region B is confined to the region where the second light-emitting layer 6 is located. However, the adjacent arrangement of the exciton recombination region A and the exciton utilization region B still leads to the quenching of some triplet excitons, which is not conducive to further improving the luminous efficiency and lifespan of the organic light-emitting device 1. Figure 3 As shown, when the HOMO energy level of the first host material in the first light-emitting layer 5 is deeper, the exciton recombination region A is confined to the side of the first light-emitting layer 5 away from the second light-emitting layer 6, and the exciton utilization region B is confined in the second light-emitting layer 6, so that there is a certain gap between the exciton recombination region A and the exciton utilization region B, which can further reduce the quenching of triplet excitons, thereby helping to improve the luminous efficiency and lifespan of the organic light-emitting device 1 to a greater extent.

[0050] Therefore, the relationship between the HOMO energy levels of the first and second host materials plays a crucial role in improving the luminous efficiency and lifespan of the organic light-emitting device 1.

[0051] In some embodiments, the HOMO and LUMO energy levels can be measured using any one of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), atmospheric photoemission spectroscopy (AC-3), cyclic voltammetry (CV), and ultraviolet-visible absorption spectroscopy (UV-Vis). Of course, quantum chemical methods, such as density functional theory (DFT), are also effective methods for calculating molecular orbital energy levels.

[0052] Understandably, both X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) belong to photoelectron spectroscopy (also known as ionization potential spectroscopy or escape function spectroscopy).

[0053] In some embodiments, the method for measuring hole mobility is as follows: an organic material is used to fabricate a hole-only device (HOD), and then an impedance spectroscopy (IS) impedance meter is used to analyze the impedance response (such as dielectric relaxation or carrier diffusion) of the HOD device at different frequencies to extract its hole mobility.

[0054] Of course, hole mobility can also be measured using the Hall effect method, time-of-flight (TOF) method, or field-effect transistor (FET) method.

[0055] In some embodiments, the thickness of the first light-emitting layer 5 is less than or equal to the thickness of the second light-emitting layer 6.

[0056] In one specific embodiment, the thickness of the first light-emitting layer 5 is greater than 0 and less than or equal to 0. The thickness of the second light-emitting layer 6 is greater than 0 and less than or equal to 190 angstroms.

[0057] Since the dual-emitting layer involves exciton energy transfer, this energy transfer is divided into Forster energy transfer and Dexter energy transfer. The Forster energy transfer distance is typically within... Within a certain range, the Dexter energy transfer distance is typically within... Furthermore, considering the diffusion effect, the thickness of the first light-emitting layer 5 is controlled within [specific range]. The optimal range is determined by considering the thickness of the first light-emitting layer 5. The thickness of the second light-emitting layer 6 cannot be too high, otherwise it will lead to excessively high operating voltage of the organic light-emitting device 1. Therefore, while simultaneously considering the trade-off between operating voltage and luminous efficiency, the thickness of the second light-emitting layer 6 is controlled within a certain range. The range is most suitable.

[0058] Furthermore, by controlling the thickness of the first light-emitting layer 5 to be less than or equal to the thickness of the second light-emitting layer 6, it is beneficial for triplet excitons to transfer from the exciton recombination region A of the first light-emitting layer 5 to the second light-emitting layer 6, and to complete the TTF process in the second light-emitting layer 6, thereby realizing the separation of the exciton recombination region A and the exciton utilization region B.

[0059] In some embodiments, the first host material includes at least one first cyclic plexiform group, and the second host material includes at least one second cyclic plexiform group; any two adjacent rings in the first cyclic plexiform group are interconnected by two shared adjacent atoms, and any two adjacent rings in the second cyclic plexiform group are interconnected by two shared adjacent atoms. At least one first cyclic plexiform group has a greater number of rings than any one of the second cyclic plexiform groups.

[0060] In other words, the largest tandem ring structure in the first main material needs to be larger than the largest tandem ring structure in the second main material.

[0061] It should be noted that the number of rings in the first and second fused cyclic groups refers to the number of rings connected by two shared adjacent atoms. For example, the naphthyl group, phenanthrene group, anthracene group, and pyrene group are all fused cyclic groups. Among them, the naphthyl group has 2 rings, the phenanthrene group and the anthracene group have 3 rings, and the pyrene group has 4 rings.

[0062] In some embodiments, the first fused ring group with the most rings in the first host material does not contain heteroatoms. The more heteroatom-free conjugations (the number of rings in the fused ring group) an organic material has, the deeper its HOMO level. However, the LUMO level of an organic material requires side-chain modification, and the side chains lack groups that facilitate hole hopping. Therefore, compared to the second host material, a larger fused ring structure molecular core generally exhibits a deeper HOMO level and slower hole mobility.

[0063] Of course, the molecular structure design of organic materials needs to take into account the entire molecular skeleton, and cannot be limited to the structural design of the molecular core. Every part of the molecular skeleton contributes to the energy level.

[0064] In some embodiments, the number of first fused cyclic groups in the first host material is greater than or equal to the number of second fused cyclic groups in the second host material. A larger number of first fused cyclic groups in the first host material results in more conjugated groups in the first host material, and conjugation extension (expansion of the conjugation range) leads to enhanced electron delocalization, thereby deepening the HOMO energy level of the first host material and making the absolute value of the HOMO energy level of the first host material larger.

[0065] Of course, in other embodiments, when the number of rings in at least one first cyclic group is greater than the number of rings in any one second cyclic group, the energy level relationship or mobility relationship shown in equations (1) to (3) can be realized, the number of first cyclic groups in the first host material can be less than the number of second cyclic groups in the second host material.

[0066] Understandably, the first and second host materials are different. The first host material can be a single compound or a mixture of two compounds. Similarly, the second host material can be a single compound or a mixture of two compounds.

[0067] In some embodiments, the first host material is selected from at least one of the compounds represented by general formula I:

[0068]

[0069] Among them, R1 to R 10 It is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted aryl group, substituted or unsubstituted heteroaryl group, and substituted or unsubstituted alkyl group.

[0070] Understandably, heteroaryl refers to a group formed when one or more carbon atoms in an aryl group are replaced by heteroatoms (such as nitrogen, oxygen, sulfur, etc.).

[0071] In some embodiments, R1 to R 10 The substituted group is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted anthracel, substituted or unsubstituted trefyl, substituted or unsubstituted benzofuranyl, substituted or unsubstituted naphthuryl, wherein the substituted or unsubstituted substituted group includes protium atom, deuterium atom or tritium atom.

[0072] In some embodiments, R1 is selected from any one or more combinations of phenyl, deuterated phenyl, trefyl, naphthyl, deuterated naphthyl, dibenzofuranyl, anthraceneyl and benzonaphthofuranyl;

[0073] R3, R4, R5, R7, and R8 are selected from hydrogen atoms or phenyl groups;

[0074] R6 is selected from any one or more combinations of hydrogen atoms, phenyl groups, and deuterated phenyl groups;

[0075] R2, R9 and R 10 Selected from hydrogen atoms.

[0076] It should be noted that deuterated phenyl means that at least one hydrogen atom in a phenyl group is replaced by a deuterium atom, and deuterated naphthyl means that at least one hydrogen atom in a naphthyl group is replaced by a deuterium atom.

[0077] In one specific embodiment, the first host material is selected from at least one of the following compounds:

[0078]

[0079]

[0080] In a preferred embodiment, the first host material is selected from any one of the compounds shown in BH1 to BH6:

[0081]

[0082] In some embodiments, the second host material is selected from at least one of the compounds represented by general formula II:

[0083]

[0084] Among them, R 11 To R 20 It is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted aryl group, substituted or unsubstituted heteroaryl group, and substituted or unsubstituted alkyl group.

[0085] In some embodiments, R 11 To R 20The substituted group is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted phenyl group, substituted or unsubstituted naphthyl group, substituted or unsubstituted benzofuranyl group, and substituted or unsubstituted naphthylfuranyl group, wherein the substituted or unsubstituted substituted group includes protium atom, deuterium atom or tritium atom.

[0086] In some embodiments, R 11 Selected from any one or more combinations of phenyl, naphthyl, biphenyl, deuterated phenyl, and deuterated naphthyl;

[0087] R 16 It is selected from any one or more combinations of phenyl, naphthyl, dibenzofuranyl, benzonaphthofuranyl, deuterated phenyl, deuterated biphenyl, deuterated dibenzofuranyl and deuterated benzonaphthofuranyl;

[0088] R 12 To R 15 and R 17 To R 20 It is selected from hydrogen atoms or deuterium atoms.

[0089] Understandably, deuterated biphenyl means that at least one hydrogen atom in a biphenyl group is replaced by a deuterium atom, deuterated dibenzofuranyl means that at least one hydrogen atom in a dibenzofuranyl group is replaced by a deuterium atom, and deuterated benzonaphthofuranyl means that at least one hydrogen atom in a benzonaphthofuranyl group is replaced by a deuterium atom.

[0090] In one specific embodiment, the second host material is selected from at least one of the following compounds:

[0091]

[0092]

[0093] In a preferred embodiment, the second host material is selected from the compound shown in BHO:

[0094]

[0095] It should be noted that by selecting appropriate first and second host materials from the compounds represented by general formulas I and II, it is beneficial for a large number of excitons in the first luminescent layer 5 to be transferred to the second luminescent layer 6, thereby achieving the separation of exciton recombination region A and exciton utilization region B.

[0096] In some embodiments, the material of the first luminescent layer 5 further includes a first guest material, and the material of the second luminescent layer 6 further includes a second guest material. The first guest material and the second guest material are selected from any one of non-thermally activated delayed fluorescence materials, phosphorescent materials, and thermally activated delayed fluorescence materials.

[0097] It should be noted that the first object material and the second object material can be the same or different.

[0098] In a preferred embodiment, the first guest material and the second guest material are selected from non-thermally activated delayed fluorescence materials.

[0099] In some embodiments, when the first guest material and the second guest material are selected from non-thermally activated delayed fluorescence materials, the first guest material and / or the second guest material are selected from at least one of the compounds represented by Formula III:

[0100]

[0101] Where X is selected from N, O, S or Se;

[0102] R 21 To R 25 It is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted aryl group, substituted or unsubstituted heteroaryl group, and substituted or unsubstituted alkyl group.

[0103] In one specific embodiment, the first guest material and / or the second guest material are selected from at least one of the following compounds:

[0104]

[0105]

[0106] In some embodiments, the light emitted by the first light-emitting layer 5 and the second light-emitting layer 6 is any one of red light, green light, and blue light. That is, the organic light-emitting device 1 can be any one of a red light device, a green light device, and a blue light device.

[0107] In a preferred embodiment, the light emitted by the first light-emitting layer 5 and the second light-emitting layer 6 is blue light, that is, the organic light-emitting device 1 is a blue light device.

[0108] In some embodiments, the hole transport layer 7 is disposed adjacent to the first light-emitting layer 5, and the triplet energy levels of the first host material, the second host material, and the hole transport layer 7 satisfy the magnitude relationship shown in equation (4):

[0109] |T1 prime |≥|T1 Host2 |+0.4≥|T1 Host1 |≥|T1 Host2 | (4);

[0110] Among them, T1 Host1 T1 Host2 and T1 primeThese represent the triplet energy levels of the first host material, the second host material, and the hole transport layer 7, respectively.

[0111] Since the exciton recombination region A in this embodiment is close to the hole transport layer 7, when the triplet energy level of the hole transport layer 7 satisfies equation (4), the triplet energy level in the hole transport layer 7 can block the triplet exciton, thus confining the triplet exciton within the first light-emitting layer 5 and the second light-emitting layer 6, which is beneficial to improving the exciton utilization rate, thereby improving the luminous efficiency and lifespan of the organic light-emitting device 1.

[0112] In some embodiments, the organic light-emitting device 1 further includes a hole injection layer 8 disposed between the anode layer 2 and the hole transport layer 7, an electron transport layer 9 disposed between the second light-emitting layer 6 and the cathode layer 3, and an electron injection layer 10, wherein the electron injection layer 10 is located between the electron transport layer 9 and the cathode layer 3.

[0113] Of course, the organic light-emitting device 1 can also have other organic functional layers that are beneficial to improving luminous efficiency and lifespan between the anode layer 2 and the first light-emitting layer 5, the second light-emitting layer 6 and the cathode layer 3, or a light extraction layer can be provided on the surface of the cathode layer 3 to improve light extraction efficiency.

[0114] In some embodiments, the organic light-emitting device 1 is an OLED device, but it is not limited thereto.

[0115] In some embodiments, the first light-emitting layer 5 and the second light-emitting layer 6 in the organic light-emitting device 1 are prepared by vacuum evaporation or inkjet printing. Of course, other organic film layers in the organic light-emitting device 1 can also be prepared by vacuum evaporation or inkjet printing.

[0116] This application also provides Comparative Examples 1 to 7, and Examples 1 to 6. Comparative Examples 1 to 7 provide comparative devices OLED-ref1 to OLED-ref7, and Examples 1 to 6 provide experimental devices OLED-1 to OLED-6. OLED-ref1 to OLED-ref7 and OLED-1 to OLED-6 are all blue light-emitting devices. The effects of the first light-emitting layer 5 and the second light-emitting layer 6 on the luminous efficiency and lifespan of the organic light-emitting device 1 were verified through the comparative examples and examples.

[0117] In this embodiment, the device structure of OLED-1 to OLED-6 is ITO / HIL (HTL: PD, 3% / HTL, / Prime, / EML1(BH 1st :BD, 2%) / EML2(BH2nd :BD, 2% / EICL, / ETL(ET:LiQ,50%) ) / Yb, / Mg:Ag, / CPL, Wherein, ITO represents indium tin oxide, i.e., the anode layer material; HIL represents the hole injection layer; PD represents the p-type dopant; HTL represents the hole transport layer; Prime represents the electron blocking material; EML1 represents the first light-emitting layer; and BH represents the first light-emitting layer. 1st BD represents the primary material, BD represents the secondary material, EML2 represents the secondary light-emitting layer, and BH represents the secondary light-emitting layer. 2nd The second main material is indicated by: EICL (Electron Injection and Hole Blocking Layer or Electron Injection Contact Layer); ETL (Electron Transport Layer); ET (Electron Transport Material); Yb (Ytterbium) represents the electron injection layer material or cathode modification material; Mg:Ag represents the cathode layer material; CPL represents the light extraction layer; 3% in HIL refers to the molar percentage of PD in the HIL material, and 2% in EML refers to the molar percentage of BD in EML1 or EML2.

[0118] Correspondingly, the device structures of OLED-ref1 to OLED-ref7 are ITO / HIL (HTL: PD, 3% / HTL, / Prime, / EML2(BH:BD, 2% / EICL, / ETL(ET:LiQ,50%) ) / Yb, / Mg:Ag, / CPL,

[0119] Understandably, the OLEDs ref1 to ref7 provided in Comparative Examples 1 to 7 all have only one emissive layer, and the thickness of the emissive layer is... The host materials in the emissive layers of OLED-ref1 to OLED-ref7 are selected from compounds shown in BH0 to BH6, respectively. The emissive layers of OLED-1 to OLED-6 provided in Examples 1 to 6 each have two layers, namely the first emissive layer 5 and the second emissive layer 6 as described in the aforementioned examples. The thickness of the first emissive layer 5 is... The thickness of the second light-emitting layer 6 is The first host material of the first light-emitting layer 5 of OLED-1 to OLED-6 is selected from the compounds shown in BH1 to BH6, and the second host material of the second light-emitting layer 6 of OLED-1 to OLED-6 is selected from the compound shown in BH0.

[0120] It is understandable that OLED-ref1 to OLED-ref7 and OLED-1 to OLED-6 differ only in the number of light-emitting layers and the main material, while the structures and materials of other layers are the same.

[0121] The HOMO level, LUMO level, and hole mobility (μ) of the compounds shown in Comparative Examples 1 to 7 and Examples 1 to 6 of this application, represented by BH0 to BH6. h The test results are shown in Table 1. The hole mobility in Table 1 was measured using the IS impedance meter described above, and the HOMO and LUMO energy levels were measured using the UPS method.

[0122] Specifically, when testing the hole mobility of the host material (BH), the HOD device structure used is ITO / HIL (HT:PD, 3% / HTL / prime / BH / HATCN / Mg:Ag(20:200). Different host materials (e.g., compounds shown in BH0 to BH6) were used to prepare corresponding HOD devices according to the above device structure, and the hole mobility of compounds shown in BH0 to BH6 was measured by an IS impedance meter.

[0123] Specifically, the structures of some of the compounds involved in OLED and HOD devices are shown below:

[0124]

[0125] Specifically, the HOMO level was measured using an IPS3 photoelectron spectrometer. The IPS3 photoelectron spectrometer operates on the principle of photoelectron emission, with ultraviolet light as the excitation source. Typically, ultraviolet light (such as He I 21.22 eV or He II 40.8 eV) is used to irradiate the sample (e.g., compounds shown in BH0 to BH6) to excite valence band electrons, and the HOMO level is obtained through energy analysis. The LUMO level is calculated based on the measured HOMO level and the band gap Eg.

[0126] In Table 1, the light-emitting layers of OLED-ref1 to OLED-ref7 provided by Comparative Examples 1 to 7 are represented by EML2, and the first light-emitting layer 5 and the second light-emitting layer 6 in OLED-1 to OLED-6 provided by Examples 1 to 6 are represented by EML1 and EML2, respectively.

[0127] Table 1

[0128]

[0129]

[0130] According to Table 1, the first and second host materials in OLED-1 provided in Example 1 do not satisfy any of the size relationships shown in Equations (1) to (3); the first and second host materials in OLED-2 provided in Example 2 do not satisfy the size relationships of HOMO energy levels and hole mobility shown in Equations (1) and (3), but only satisfy the size relationship of LUMO energy levels shown in Equation (2), and Equation (2) is not equal; the first and second host materials in OLED-3 provided in Example 3 satisfy the size relationships of HOMO energy levels and LUMO energy levels shown in Equations (1) and (2), respectively, but do not satisfy the size relationship of hole mobility shown in Equation (3), where Equation (1) is equal while Equation (2) is not; the OLED-4 provided in Example 4 The first and second host materials in the OLED-5 provided in Example 5 satisfy the magnitude relationships of HOMO and LUMO energy levels shown in Equations (1) and (2), respectively, but do not satisfy the magnitude relationship of hole mobility shown in Equation (3), and Equations (1) and (2) are not equal. The first and second host materials in the OLED-6 provided in Example 6 satisfy the magnitude relationships of HOMO and LUMO energy levels shown in Equations (1) and (2), respectively, but do not satisfy the magnitude relationship of hole mobility shown in Equation (3), and Equations (1) and (2) are not equal. The first and second host materials in the OLED-6 provided in Example 6 satisfy the magnitude relationships of HOMO energy levels, LUMO energy levels, and hole mobility shown in Equations (1) to (3), respectively, and Equations (1), (2), and (3) are not equal. Furthermore, the hole mobility of the first host material in Example 4 is relatively close to that of the second host material, while the hole mobility of the first host material in Example 5 is significantly greater than that of the second host material.

[0131] The current-voltage (JV) characteristics of OLED-ref1 to OLED-ref7 provided in Comparative Examples 1 to 7 and OLED-1 to OLED-6 provided in Examples 1 to 6 of this application were characterized using a characterization device. Important parameters such as luminous efficiency and lifetime were recorded, and the results are shown in Table 2. The device efficiency in Table 2 refers to the efficiency of organic light-emitting device 1 at 10 mA / cm². 2 The current efficiency and device lifetime of an organic light-emitting device (OLED) at 30 mA / cm² are discussed. 2 The time it takes for the brightness to decay to 97% of the initial brightness.

[0132] Specifically, the voltage in Table 2 refers to the voltage applied between the anode layer 2 and the cathode layer 3 of the organic light-emitting device 1, and the voltage and luminous efficiency are obtained by testing using the IVL automated optical testing system. The IVL automated optical testing system includes a PR735 spectrometer, a KEITHLEY 2420 DC power supply, and auxiliary tools such as fixtures.

[0133] Specifically, the luminous efficiency in Table 2 is calculated using equation (5):

[0134] CE = Lum * S / (I * Tr) (5);

[0135] Wherein, CE represents the luminous efficiency of organic light-emitting device 1; Lum represents the luminous brightness of organic light-emitting device 1; S represents the luminous area of ​​organic light-emitting device 1; I represents the current driving organic light-emitting device 1 to achieve the luminous brightness; and Tr represents the transmittance of the light-emitting side of organic light-emitting device 1.

[0136] Specifically, the lifespan in Table 2 was obtained by testing with an OLED lifespan testing system, which includes a KEITHLEY3706A DC power supply.

[0137] Table 2

[0138] Devices Voltage Luminous efficiency Service life Comparative Example 1 OLED-ref1 100％ 100％ 100％ Comparative Example 2 OLED-ref2 107％ 99％ 35％ Comparative Example 3 OLED-ref3 108％ 98％ 43％ Comparative Example 4 OLED-ref4 109％ 99％ 24％ Comparative Example 5 OLED-ref5 108％ 100％ 45％ Comparative Example 6 OLED-ref6 107％ 97％ 52％ Comparative Example 7 OLED-ref7 110％ 100％ 16％ Example 1 OLED-1 103％ 105％ 120％ Example 2 OLED-2 104％ 108％ 134％ Example 3 OLED-3 104％ 110％ 156％ Example 4 OLED-4 104％ 118％ 168％ Example 5 OLED-5 103％ 115％ 146％ Example 6 OLED-6 105％ 125％ 175％

[0139] As shown in Table 2, the voltage, luminous efficiency, and lifespan of Comparative Examples 2 to 7 and Examples 1 to 6 are all referenced to the voltage, luminous efficiency, and lifespan of OLED-ref1 provided in Comparative Example 1. Compared with OLED-ref1 to OLED-ref7 provided in Comparative Examples 1 to 7, the operating voltage of OLED-1 to OLED-6 provided in Examples 1 to 6 of this application is relatively small, and the luminous efficiency and lifespan are significantly improved. Compared with a single-layer light-emitting layer, using a double-layer light-emitting layer can reduce the power consumption of the organic light-emitting device 1 and improve the luminous efficiency and lifespan of the organic light-emitting device 1.

[0140] Furthermore, compared with Examples 1 to 5, the OLED-6 provided in Example 6 has the most significant improvement in luminous efficiency and lifespan. This indicates that when the first host material and the second host material simultaneously satisfy the magnitude relationship of HOMO energy level, LUMO energy level and hole mobility shown in Equations (1) to (3), and Equations (1), (2) and (3) are not equal, the improvement in luminous efficiency and lifespan of the device is the most significant.

[0141] Furthermore, comparing Examples 4 and 5, it can be seen that when the hole mobility of the first host material is significantly greater than that of the second host material, it is not conducive to improving the luminous efficiency and lifespan of the device.

[0142] As can be seen from the above, when the first main material of the first light-emitting layer 5 and the second main material of the second light-emitting layer 6 satisfy the size relationship shown in equations (1) to (3), and equations (1), (2) and (3) do not simultaneously take the equal sign, the luminous efficiency and service life of the organic light-emitting device 1 can be effectively improved.

[0143] like Figure 4 As shown, this application embodiment also provides a display device 11, which includes the organic light-emitting device 1 described in the above embodiments.

[0144] In some embodiments, the display device 11 further includes an array substrate 12 and an encapsulation layer 13. A driving circuit is provided in the array substrate 12, and a plurality of organic light-emitting devices 1 are disposed between the array substrate 12 and the encapsulation layer 13 and electrically connected to the driving circuit. It is understood that the driving circuit is used to provide driving voltages to the anode layer 2 and cathode layer 3 in the organic light-emitting devices 1, thereby achieving light emission.

[0145] In some embodiments, the display device 11 includes a red OLED device, a green OLED device, and a blue OLED device, and at least one of the red OLED device, green OLED device, and blue OLED device has the same structure as the organic light-emitting device 1 in the foregoing embodiments.

[0146] For example, in some embodiments, the light-emitting layers of the red OLED device, green OLED device and blue OLED device in the display device 11 are all the double-layer light-emitting layer structure described in the embodiments of this application; in other embodiments, the light-emitting layers of the red OLED device and green OLED device in the display device 11 are single-layer light-emitting layers, while the light-emitting layer of the blue OLED device is the double-layer light-emitting layer structure described in the embodiments of this application, but not limited thereto.

[0147] In this embodiment, since the luminous efficiency and lifespan of the organic light-emitting device 1 are improved, it is beneficial to improve the display effect of the display device 11 and extend the lifespan of the display device 11.

[0148] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0149] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0150] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0151] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. An organic light-emitting device, characterized in that, include: Anode layer; A cathode layer is disposed opposite to the anode layer; At least one light-emitting unit is disposed between the anode layer and the cathode layer; At least one of the light-emitting units includes a first light-emitting layer and a second light-emitting layer stacked and bonded together, wherein the first light-emitting layer is located on the side of the second light-emitting layer closer to the anode layer; the material of the first light-emitting layer includes a first main material, and the material of the second light-emitting layer includes a second main material, wherein the first main material and the second main material satisfy the size relationship shown in equations (1) to (3), and equations (1), (2), and (3) are not simultaneously equal: |HOMO Host1 |≥|HOMO Host2 | (1); |LIGHT Host1 |≤|LIGHT Host2 | (2); m Host1 ≤μ Host2 (3); Among them, HOMO Host1 and HOMO Host2 LUMO represents the highest occupied molecular orbital energy levels of the first and second host materials, respectively. Host1 and LUMO Host2 μ represents the lowest unoccupied molecular orbital energy levels of the first host material and the second host material, respectively. Host1 and μ Host2 These represent the hole mobility rates of the first and second main materials, respectively.

2. The organic light-emitting device according to claim 1, characterized in that, The thickness of the first light-emitting layer is less than or equal to the thickness of the second light-emitting layer.

3. The organic light-emitting device according to claim 2, characterized in that, The thickness of the first light-emitting layer is greater than 0 and less than or equal to 150 angstroms, and the thickness of the second light-emitting layer is greater than 0 and less than or equal to 190 angstroms.

4. The organic light-emitting device according to claim 1, characterized in that, The first host material includes at least one first cyclic group, and the second host material includes at least one second cyclic group; any two adjacent rings in the first cyclic group are connected to each other by two shared adjacent atoms, and any two adjacent rings in the second cyclic group are connected to each other by two shared adjacent atoms. At least one of the first cyclic groups has a greater number of rings than any of the second cyclic groups.

5. The organic light-emitting device according to claim 4, characterized in that, The number of the first cyclic groups in the first host material is greater than or equal to the number of the second cyclic groups in the second host material.

6. The organic light-emitting device according to claim 4, characterized in that, The first host material is selected from at least one of the compounds represented by general formula I: Among them, R1 to R 10 It is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted aryl group, substituted or unsubstituted heteroaryl group, and substituted or unsubstituted alkyl group.

7. The organic light-emitting device according to claim 6, characterized in that, R1 to R 10 The substituted group is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted anthracel, substituted or unsubstituted trefyl, substituted or unsubstituted benzofuranyl, substituted or unsubstituted naphthuryl, wherein the substituted or unsubstituted substituted group includes protium atom, deuterium atom or tritium atom.

8. The organic light-emitting device according to claim 7, characterized in that, R1 is selected from any one or more combinations of phenyl, deuterated phenyl, trefyl, naphthyl, deuterated naphthyl, dibenzofuranyl, anthraceneyl and benzonaphthofuranyl; R3, R4, R5, R7, and R8 are selected from hydrogen atoms or phenyl groups; R6 is selected from any one or more combinations of hydrogen atoms, phenyl groups, and deuterated phenyl groups; R2, R9 and R 10 Selected from hydrogen atoms.

9. The organic light-emitting device according to claim 8, characterized in that, The first host material is selected from at least one of the following compounds:

10. The organic light-emitting device according to claim 4, characterized in that, The second host material is selected from at least one of the compounds represented by general formula II: Among them, R 11 To R 20 It is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted aryl group, substituted or unsubstituted heteroaryl group, and substituted or unsubstituted alkyl group.

11. The organic light-emitting device according to claim 10, characterized in that, R 11 To R 20 The substituted group is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted phenyl group, substituted or unsubstituted naphthyl group, substituted or unsubstituted benzofuranyl group, and substituted or unsubstituted naphthylfuranyl group, wherein the substituted or unsubstituted substituted group includes protium atom, deuterium atom or tritium atom.

12. The organic light-emitting device according to claim 11, characterized in that, R 11 Selected from any one or more combinations of phenyl, naphthyl, biphenyl, deuterated phenyl, and deuterated naphthyl; R 16 It is selected from any one or more combinations of phenyl, naphthyl, dibenzofuranyl, benzonaphthofuranyl, deuterated phenyl, deuterated biphenyl, deuterated dibenzofuranyl and deuterated benzonaphthofuranyl; R 12 To R 15 and R 17 To R 20 It is selected from hydrogen atoms or deuterium atoms.

13. The organic light-emitting device according to claim 12, characterized in that, The second host material is selected from at least one of the following compounds:

14. The organic light-emitting device according to any one of claims 1 to 13, characterized in that, The material of the first luminescent layer further includes a first guest material, and the material of the second luminescent layer further includes a second guest material; the first guest material and the second guest material are selected from any one of non-thermally activated delayed fluorescence materials, phosphorescent materials and thermally activated delayed fluorescence materials.

15. The organic light-emitting device according to claim 14, characterized in that, The first guest material and the second guest material are selected from non-thermally activated delayed fluorescence materials, and the first guest material and / or the second guest material are selected from at least one of the compounds represented by Formula III: Where X is selected from N, O, S or Se; R 21 To R 25 It is selected from any one or more combinations of hydrogen atom, protium atom, deuterium atom, tritium atom, substituted or unsubstituted aryl group, substituted or unsubstituted heteroaryl group, and substituted or unsubstituted alkyl group.

16. The organic light-emitting device according to claim 15, characterized in that, The first guest material and / or the second guest material are selected from at least one of the following compounds:

17. The organic light-emitting device according to claim 1, characterized in that, The light emitted by the first light-emitting layer and the second light-emitting layer is blue light.

18. The organic light-emitting device according to claim 1, characterized in that, The organic light-emitting device further includes a hole transport layer located on the side of the first light-emitting layer near the anode layer, and the hole transport layer is disposed adjacent to the first light-emitting layer; The triplet energy levels of the first host material, the second host material, and the hole transport layer satisfy the magnitude relationship shown in equation (4): |T1 prime |≥|T1 Host2 |+0.4≥|T1 Host1 |≥|T1 Host2 | (4); Among them, T1 Host1 T1 Host2 and T1 prime These represent the triplet energy levels of the first host material, the second host material, and the hole transport layer, respectively.

19. A display device, characterized in that, Including the organic light-emitting device as described in any one of claims 1 to 18.

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