Blue light pixel unit and display panel

Abstract

The blue light pixel unit and the display panel provided by the embodiment relate to the technical field of display. In the blue light pixel unit, the blue light pixel light-emitting material layer comprises a phosphorescent light-emitting material layer and a fluorescent light-emitting material layer, the fluorescent light-emitting material layer is arranged close to the anode, and the phosphorescent light-emitting material layer is arranged close to the cathode. In this way, the triplet-triplet annihilation (TTA) effect can be formed in the fluorescent light-emitting material layer, triplet excitons are converted into singlet excitons that can be used by the fluorescent guest, the light-emitting efficiency of the fluorescent light-emitting material layer is improved, and the overall light-emitting efficiency of the blue light pixel unit is improved. In addition, the above structure can form a large number of singlet excitons that can be used by the fluorescent guest through the triplet-triplet annihilation effect, does not need a large hole and electron injection barrier, and can achieve the purpose of reducing the power consumption of the blue light pixel unit.

Description

Technical Field

[0001] This application relates to the field of display technology, and more specifically, to a blue light pixel unit and a display panel. Background Technology

[0002] Organic light-emitting diode (OLED) display panels have gradually gained a foothold in the small-size display panel market due to their advantages such as thinness, flexibility, high contrast, and wide color gamut. However, OLED display panels based on RGB (red, green, and blue) pixel arrangement suffer from low blue light luminous efficiency, and how to improve blue light luminous efficiency has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0003] In order to overcome the technical problems mentioned in the above technical background, this application provides a blue light pixel unit and a display panel.

[0004] A first aspect of this application provides a blue light pixel unit, comprising:

[0005] Anode, cathode, and a blue light-emitting pixel material layer located between the anode and cathode;

[0006] The blue pixel luminescent material layer includes a phosphorescent luminescent material layer doped with a phosphorescent guest and a fluorescent luminescent material layer doped with a fluorescent guest. The phosphorescent luminescent material layer and the fluorescent luminescent material layer are stacked, wherein the fluorescent luminescent material layer is disposed near the anode and the phosphorescent luminescent material layer is disposed near the cathode.

[0007] The aforementioned structure can induce a triplet-triplet annihilation (TTA) effect in the fluorescent luminescent material layer, converting triplet excitons into singlet excitons that can be utilized by fluorescent guests. This improves the luminous efficiency of the fluorescent luminescent material layer and the overall luminous efficiency of the blue light pixel unit. Furthermore, the structure can generate a large number of singlet excitons that can be utilized by fluorescent guests through the triplet-triplet annihilation effect, eliminating the need for large hole and electron injection barriers and thus reducing the power consumption of the blue light pixel unit.

[0008] In one possible embodiment of this application, the blue pixel luminescent material layer further includes a co-doped luminescent material layer formed by co-doping of the phosphorescent guest and the fluorescent guest;

[0009] The co-doped luminescent material layer is located at the junction of the phosphorescent luminescent material layer and the fluorescent luminescent material layer.

[0010] The triplet-triplet annihilation effect occurs in the fluorescent luminescent material layer. Most of the singlet excitons formed by the annihilation of triplet excitons can be used by fluorescent guests for luminescence, while the remaining small number of singlet excitons can be used by phosphorescent guests for luminescence, thus improving the overall luminescence efficiency of the blue light pixel unit.

[0011] In one possible embodiment of this application, the thickness of the fluorescent luminescent material layer accounts for 10% to 50% of the thickness of the blue pixel luminescent material layer, and the thickness of the co-doped luminescent material layer accounts for 1% to 50% of the thickness of the blue pixel luminescent material layer, wherein the thickness of the co-doped luminescent material layer is less than the thickness of the fluorescent luminescent material layer. This design allows the luminescence of the fluorescent luminescent material layer to be closer to the anode, while the luminescence of the phosphorescent luminescent material layer is closer to the cathode.

[0012] In one possible embodiment of this application, the host material of the phosphorescent luminescent material layer and the host material of the fluorescent luminescent material layer are the same. Using the same host material facilitates the co-doping of phosphorescent and fluorescent guest materials into the host material to form a co-doped luminescent material layer.

[0013] In one possible embodiment of this application, the excited state energy of the phosphorescent guest is the same as that of the fluorescent guest, and the excited state energy of the phosphorescent guest and the excited state energy of the fluorescent guest are less than the excited state energy of the host material;

[0014] Preferably, the LUMO energy level difference between the phosphorescent guest and the host material is less than 0.5 eV. This allows for the control of luminescence from the phosphorescent and fluorescent guest while the host material remains non-luminescent, ensuring the uniformity of luminescence in the blue pixel unit.

[0015] In one possible embodiment of this application, the doping ratio of the fluorescent guest is 1-5%, and the doping ratio of the phosphorescent guest is 1-10%.

[0016] In one possible embodiment of this application, the phosphorescent guest and the fluorescent guest have better electron transport performance than hole transport performance.

[0017] The host material exhibits better electron transport performance than hole transport performance.

[0018] This design, with the combination of guest and host materials, allows the recombination region of holes and electrons to be located close to the anode. The excitons formed by the recombination of holes and electrons have a high concentration near the anode and a low concentration near the cathode. Since the phosphorescent material layer is close to the cathode, fewer excitons can be utilized by the phosphorescent guest in the phosphorescent material layer, which can ensure the lifespan of the phosphorescent guest and thus ensure that the entire blue pixel unit has a long lifespan.

[0019] In one possible embodiment of this application, the phosphorescent guest includes at least one of N-heterocyclic carbene blue tetradentate platinum(II) complexes, pyrazole blue tetradentate platinum(II) complexes, and imidazole blue tetradentate platinum(II) complexes; the fluorescent guest includes BN resonant fluorescent luminescent material; and the host material includes anthracene derivatives.

[0020] In one possible embodiment of this application, it further includes:

[0021] Electron blocking layer and hole blocking layer;

[0022] The electron blocking layer is located between the anode and the fluorescent luminescent material layer, and the hole blocking layer is located between the cathode and the phosphorescent luminescent material layer.

[0023] A second aspect of this application provides a display panel that includes blue light pixel units in any of the possible embodiments of the first aspect.

[0024] Compared to existing technologies, in the blue light pixel unit provided in this embodiment, the blue light pixel luminescent material layer includes a phosphorescent luminescent material layer and a fluorescent luminescent material layer. The fluorescent luminescent material layer is disposed near the anode, and the phosphorescent luminescent material layer is disposed near the cathode. This design allows for the formation of a triplet-triplet annihilation (TTA) effect in the fluorescent luminescent material layer, converting triplet excitons into singlet excitons that can be utilized by fluorescent guests, thereby improving the luminous efficiency of the fluorescent luminescent material layer and the overall luminous efficiency of the blue light pixel unit. Furthermore, the above structure can generate a large number of singlet excitons that can be utilized by fluorescent guests through the triplet-triplet annihilation effect, eliminating the need for large hole and electron injection barriers and thus reducing the power consumption of the blue light pixel unit. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic diagram of a film structure of the blue light pixel unit provided in this embodiment is illustrated.

[0027] Figure 2 This embodiment illustrates another film structure of the blue light pixel unit.

[0028] Figure 3-4The chemical structural formula of the phosphorescent guest material provided in this embodiment is illustrated;

[0029] Figure 5 The chemical structural formula of the fluorescent guest material provided in this embodiment is illustrated;

[0030] Figure 6 The chemical structural formula of the main material provided in this embodiment is illustrated;

[0031] Figure 7 This example illustrates another film structure of the blue light pixel unit provided in this embodiment.

[0032] Icons: 10 - Blue light pixel unit; 110 - Anode; 120 - Cathode; 130 - Blue light pixel luminescent material layer; 1301 - Fluorescent luminescent material layer; 1302 - Phosphorescent luminescent material layer; 1303 - Co-doped luminescent material layer; 1401 - Electron blocking layer; 1402 - Hole injection layer; 1403 - Hole transport layer; 1501 - Hole blocking layer; 1502 - Electron transport layer; 1503 - Electron injection layer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] It should be noted that, where there is no conflict, different features in the embodiments of this application can be combined with each other.

[0038] Regarding the technical problems mentioned in the background, the inventors, through long-term research, discovered that one of the main reasons for the low luminous efficiency of blue light is that the luminescent material layer of the blue pixel unit uses blue phosphor material. Since the generation ratio of singlet excitons to triplet excitons in OLED pixel units is 1:3, and blue phosphor material can only utilize 25% of the singlet excitons, there is a problem of low exciton utilization. Furthermore, the wide bandgap of blue phosphor material leads to a large injection barrier for holes and electrons, making it impossible to obtain a high carrier recombination density. Thus, blue pixel units using blue phosphor material as the luminescent material layer suffer from low luminous efficiency. To improve the luminous efficiency of blue pixel units, one approach is to use blue phosphorescent material to fabricate the luminescent material layer. Blue phosphorescent material can utilize both singlet and triplet excitons, thereby improving the luminous efficiency of the blue pixel unit. Another approach is to increase the voltage signals acting on the anode and cathode of the blue pixel unit, thereby increasing the carrier recombination density.

[0039] Regarding the first approach, the short lifespan of the luminescent material layer made from blue phosphorescent materials makes it difficult to meet product requirements, thus hindering its industrial application. Regarding the second approach, increasing the voltage signals acting on the anode and cathode of the blue pixel unit would increase the overall power consumption of the display panel, contradicting the industry's trend of gradually reducing display panel power consumption.

[0040] To address the aforementioned technical problems, the inventors have innovatively designed the following technical solutions, which will be described in detail below with reference to the accompanying drawings. It should be noted that the deficiencies in the existing solutions are the result of the inventors' practical experience and careful research. Therefore, the discovery process of the aforementioned technical problems and the solutions proposed in this embodiment below are contributions made by the inventors to this application during the invention process, and should not be construed as technical content known to those skilled in the art.

[0041] Please refer to Figure 1 , Figure 1 A schematic diagram illustrating a film structure of the blue light pixel unit provided in this embodiment is shown. The blue light pixel unit 10 may include an anode 110, a cathode 120, and a blue light pixel luminescent material layer 130, wherein the blue light pixel luminescent material layer 130 is located between the anode 110 and the cathode 120.

[0042] In this embodiment, the blue pixel luminescent material layer 130 may include a phosphorescent luminescent material layer 1302 doped with a phosphorescent guest and a fluorescent luminescent material layer 1301 doped with a fluorescent guest. The phosphorescent luminescent material layer 1302 and the fluorescent luminescent material layer 1301 are stacked, wherein the fluorescent luminescent material layer 1301 is disposed near the anode 110 and the phosphorescent luminescent material layer 1301 is disposed near the cathode 120.

[0043] The blue light pixel unit structure provided in this embodiment can form a triplet-triplet annihilation (TTA) effect in the fluorescent luminescent material layer, converting triplet excitons into singlet excitons that can be utilized by fluorescent guests, thereby improving the luminescence efficiency of the fluorescent luminescent material layer. The remaining excitons can be utilized by phosphorescent guests for luminescence, improving the overall luminescence efficiency of the blue light pixel unit. In addition, the above structure can form a large number of singlet excitons that can be utilized by fluorescent guests through the triplet-triplet annihilation effect, without the need for large hole and electron injection barriers, thus reducing the power consumption of the blue light pixel unit.

[0044] Further, please refer to Figure 2 , Figure 2 This embodiment illustrates a schematic diagram of a film structure for a blue light pixel unit. In this embodiment, the blue light pixel luminescent material layer 130 may further include a co-doped luminescent material layer 1303 formed by co-doping with phosphorescent and fluorescent guest materials. The co-doped luminescent material layer 1303 is located at the boundary between the phosphorescent luminescent material layer 1302 and the fluorescent luminescent material layer 1301. Figure 2 As shown, the co-doped luminescent material layer 1303 can be represented by the overlapping region between the fluorescent luminescent material layer 1301 and the phosphorescent luminescent material layer 1302 at their interface. ， The co-doped luminescent material layer 1303 is composed of a fluorescent luminescent material layer 1301 and a phosphorescent luminescent material layer 1302. Triplet-Triplet Annihilation (TTA) occurs in the fluorescent luminescent material layer 1301. Most of the singlet excitons formed by triplet exciton annihilation can be utilized by the fluorescent guest for luminescence, while the remaining small portion of singlet excitons can be utilized by the phosphorescent guest for luminescence, thus improving the overall luminous efficiency of the blue pixel unit.

[0045] Furthermore, please refer to again Figure 2 In this embodiment, the thickness d1 of the fluorescent luminescent material layer 1301 can account for 10% to 50% of the thickness d of the blue pixel luminescent material layer 130. For example, the thickness d1 of the fluorescent luminescent material layer 1301 can account for 10%, 12%, 15%, 22%, 28%, 40%, 43%, 46%, 48%, or 50% of the thickness d of the blue pixel luminescent material layer 130. The thickness d2 of the co-doped luminescent material layer 1303 accounts for 1% to 50% of the thickness d of the blue pixel luminescent material layer 130. For example, the thickness d2 of the co-doped luminescent material layer 1303 accounts for 1%, 2%, 4%, 7%, 10%, 20%, 28%, 39%, 43%, 47%, 49%, or 50% of the thickness d of the blue pixel luminescent material layer 130. The thickness d1 of the fluorescent luminescent material layer 1301 is greater than the thickness d2 of the co-doped luminescent material layer 1303. This design allows the light emitted by the fluorescent luminescent material layer 1301 to be closer to the anode 110, while the light emitted by the phosphorescent luminescent material layer 1302 is closer to the cathode 120.

[0046] In this embodiment, the host material of the phosphorescent luminescent material layer 1302 and the host material of the fluorescent luminescent material layer 1301 can be the same. Using the same host material makes it convenient for phosphorescent and fluorescent guests to be co-doped into the host material to form a co-doped luminescent material layer 1303.

[0047] In order to make the blue light pixel unit 10 emit uniform blue light, in this embodiment, phosphorescent guest and fluorescent guest with the same excited state energy can be used so that the two guests can emit blue light of the same wavelength after using excitons.

[0048] Furthermore, the excited-state energies of the phosphorescent guest and the fluorescent guest can be lower than the excited-state energies of the host material. This allows for the control of luminescence from the phosphorescent and fluorescent guests while the host material remains non-luminescent, ensuring the uniformity of luminescence in the blue pixel unit 10. In this embodiment, the LUMO energy level difference between the phosphorescent guest and the host material is less than 0.5 eV.

[0049] Further, in this embodiment, the doping ratio of the fluorescent guest in the fluorescent luminescent material layer 1301 can be 1% to 5%. For example, the doping ratio of the fluorescent guest can be 1%, 1.2%, 1.6%, 2.0%, 2.3%, 2.8%, 3.4%, 3.9%, 4.2%, 4.6%, 4.8%, 4.9%, or 5%. In the phosphorescent luminescent material layer 1302, the doping ratio of the phosphorescent guest can be 1% to 10%. For example, the doping ratio of the phosphorescent guest can be 1%, 1.8%, 2.6%, 3.4%, 3.9%, 4.8%, 5.6%, 6.9%, 7.3%, 8.4%, 8.8%, 9.5%, 9.8%, or 10%.

[0050] In this embodiment, the phosphorescent and fluorescent guest materials are made of materials with electron transport characteristics, meaning that the electron transport performance of the phosphorescent and fluorescent guest materials is better than their hole transport performance. The host material is made of an N-type material, meaning that the host material has better electron transport performance than its hole transport performance. Doping the host material with electron transport characteristics into the host material has little impact on electron transport in the luminescent material layer. The combination of the guest material and the host material allows the recombination region of holes and electrons to be located close to the anode 110. The excitons formed by the recombination of holes and electrons have a high concentration near the anode 110 and a low concentration near the cathode 120. Since the phosphorescent luminescent material layer 1302 is close to the cathode 120, fewer excitons can be utilized by the phosphorescent guest material in the phosphorescent luminescent material layer 1302, thus ensuring the lifespan of the phosphorescent guest material and thereby ensuring a longer lifespan for the entire blue pixel unit 10.

[0051] Furthermore, in this embodiment, the phosphorescent guest may include, but is not limited to, at least one of N-heterocyclic carbene-based blue tetradentate platinum(II) complexes, pyrazole-based blue tetradentate platinum(II) complexes, and imidazole-based blue tetradentate platinum(II) complexes, such as... Figure 3 and Figure 4 The chemical structural formulas of phosphorescent guest materials are illustrated. Fluorescent guests can include, but are not limited to, BN resonant fluorescent luminescent materials, such as... Figure 5 The chemical structural formula of the fluorescent guest material is illustrated. The host material may include, but is not limited to, anthracene derivatives, such as... Figure 6 The chemical structural formulas of anthracene derivatives are shown in the examples.

[0052] In this embodiment, please refer to Figure 7 , Figure 7This embodiment illustrates another film structure of the blue light pixel unit. The blue light pixel unit 10 may further include an electron block layer (EBL) 1401 and a hole block layer (HBL) 1501, wherein the electron block layer 1401 is located between the anode 110 and the fluorescent light-emitting material layer 1301, and the hole block layer 1501 is located between the cathode 120 and the phosphorescent light-emitting material layer 1302.

[0053] Furthermore, in this embodiment, please refer again to... Figure 7 The blue light pixel unit 10 may further include a hole injection layer (HIL) 1402, a hole transport layer (HTL) 1403, an electron injection layer (EIL) 1503, and an electron transport layer (ETL) 1502. The hole injection layer 1402 and the hole transport layer 1403 are located between the anode 110 and the electron blocking layer 1401. The hole injection layer 1402 is disposed on the side of the anode 110 closest to the electron blocking layer 1401, and the hole transport layer 1403 is located between the hole injection layer 1402 and the electron blocking layer 1401. The electron transport layer 1502 and the electron injection layer 1503 are located between the cathode 120 and the hole blocking layer 1501. The electron injection layer 1503 is disposed on the side of the cathode 120 close to the hole blocking layer 1501, and the electron transport layer 1502 is located between the electron injection layer 1503 and the hole blocking layer 1501.

[0054] This embodiment also provides a display panel that uses red, green, and blue pixel units for pixel arrangement. The blue pixel unit of the display panel is the blue pixel unit 10 described earlier in this embodiment. Using the blue pixel unit provided in this embodiment can reduce the power consumption of the display panel.

[0055] The blue light pixel unit and display panel provided in this embodiment include a phosphorescent light-emitting material layer and a fluorescent light-emitting material layer in the blue light pixel unit. The fluorescent light-emitting material layer is disposed near the anode, and the phosphorescent light-emitting material layer is disposed near the cathode. This design allows for the formation of a triplet-triplet annihilation (TTA) effect in the fluorescent light-emitting material layer, converting triplet excitons into singlet excitons that can be utilized by fluorescent guests, thereby improving the luminous efficiency of the fluorescent light-emitting material layer and the overall luminous efficiency of the blue light pixel unit. In addition, the above structure can generate a large number of singlet excitons that can be utilized by fluorescent guests through the triplet-triplet annihilation effect, without the need for a large hole and electron injection barrier, thus reducing the power consumption of the blue light pixel unit.

[0056] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A blue light pixel unit, characterized in that, include: Anode, cathode, and a blue light-emitting pixel material layer located between the anode and cathode; The blue pixel luminescent material layer includes a phosphorescent luminescent material layer doped with a phosphorescent guest and a fluorescent luminescent material layer doped with a fluorescent guest. The phosphorescent luminescent material layer and the fluorescent luminescent material layer are stacked, wherein the fluorescent luminescent material layer is disposed close to the anode and the phosphorescent luminescent material layer is disposed close to the cathode. The blue pixel luminescent material layer further includes a co-doped luminescent material layer formed by co-doping of the phosphorescent guest and the fluorescent guest, wherein the thickness of the co-doped luminescent material layer is less than the thickness of the fluorescent luminescent material layer; The co-doped luminescent material layer corresponds to the overlapping region at the junction of the phosphorescent luminescent material layer and the fluorescent luminescent material layer; The main material of the phosphorescent material layer is the same as the main material of the fluorescent material layer, and the main material is biased towards N-type material; The phosphorescent guest and the fluorescent guest exhibit better electron transport performance than hole transport performance. The host material exhibits better electron transport performance than hole transport performance.

2. The blue light pixel unit as described in claim 1, characterized in that, The thickness of the fluorescent luminescent material layer accounts for 10% to 50% of the thickness of the blue pixel luminescent material layer, and the thickness of the co-doped luminescent material layer accounts for 1% to 49% of the thickness of the blue pixel luminescent material layer.

3. The blue light pixel unit as described in claim 2, characterized in that, The excited state energy of the phosphorescent guest is the same as that of the fluorescent guest, and the excited state energy of the phosphorescent guest and the fluorescent guest is less than that of the host material.

4. The blue light pixel unit as described in claim 3, characterized in that, The difference between the LUMO energy level of the phosphorescent guest and the LUMO energy level of the host material is less than 0.5 eV.

5. The blue light pixel unit as described in claim 3, characterized in that, The doping ratio of the fluorescent guest is 1-5%, and the doping ratio of the phosphorescent guest is 1-10%.

6. The blue light pixel unit as described in claim 1, characterized in that, The phosphorescent guest includes at least one of N-heterocyclic carbene-based blue tetradentate platinum(II) complexes, pyrazole-based blue tetradentate platinum(II) complexes, and imidazole-based blue tetradentate platinum(II) complexes; the fluorescent guest includes BN resonant fluorescent luminescent materials; and the host material includes anthracene derivatives.

7. The blue light pixel unit as described in any one of claims 1-6, characterized in that, Also includes: Electron blocking layer and hole blocking layer; The electron blocking layer is located between the anode and the fluorescent luminescent material layer, and the hole blocking layer is located between the cathode and the phosphorescent luminescent material layer.

8. A display panel, characterized in that, The display panel includes the blue light pixel unit as described in any one of claims 1-7.

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