Light emitting device and display panel

Abstract

The application discloses a light-emitting device and a display panel. The light-emitting device comprises a first electrode, a second electrode, and at least one light-emitting layer arranged between the first electrode and the second electrode. The light-emitting layer comprises a host material, a sensitizer and a fluorescent guest material. The light-emitting peak wavelength range of the light-emitting layer is 430 nm-470 nm. The thickness of the light-emitting layer is defined as D. The thickness value of the side surface of the light-emitting layer close to the first electrode is defined as 0. The thickness value of the side surface of the light-emitting layer close to the second electrode is defined as D. In the thickness range of 0-0.4D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10-100. In the thickness range of 0.4D-0.6D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 0.5-15 or 80-100. In the thickness range of 0.6D-D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10-100. The application can improve the blue light-emitting efficiency.

Description

Technical Field

[0001] This application relates to the field of display device technology, and in particular to light-emitting devices and display panels. Background Technology

[0002] OLED (Organic Light-Emitting Diode) display panels are receiving increasing attention due to their advantages such as self-illumination, low power consumption, high brightness, high response speed, and flexible display capabilities.

[0003] Among numerous OLED light-emitting technologies, phosphorescent-assisted thermally activated delayed fluorescence (pTSF) devices are considered an important technological approach to improve the overall performance of light-emitting devices due to their ability to achieve efficient energy transfer and high external quantum efficiency. Patent CN119604124A discloses relevant technical information about pTSF for reference. Summary of the Invention

[0004] To address the above-mentioned or other problems, this application provides the following technical solutions.

[0005] To solve the above-mentioned technical problems, the first technical solution adopted in this application is to provide a light-emitting device, including: a first electrode; a second electrode; at least one light-emitting layer disposed between the first electrode and the second electrode, the light-emitting layer including a host material, a sensitizer, and a fluorescent guest material; the emission peak wavelength range of the light-emitting layer is 430nm~470nm; the thickness of the light-emitting layer is defined as D, the thickness of the surface of the light-emitting layer near the first electrode is defined as 0, the thickness of the surface of the light-emitting layer near the second electrode is defined as D, in the thickness region of 0~0.4D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100; and / or, in the thickness region of 0.4D~0.6D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 0.5~15 or 80~100; and / or, in the thickness region of 0.6D~D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100.

[0006] Specifically, in the 0~0.4D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to increase; and / or, in the 0.6D~D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to decrease.

[0007] Specifically, in the 0.4D~0.5D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to decrease; and / or, in the 0.5D~0.6D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to increase.

[0008] Specifically, in the 0~0.4D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase; and / or, in the 0.6D~D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease.

[0009] Specifically, in the 0.4D~0.5D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease; and / or, in the 0.5D~0.6D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase.

[0010] The sensitizer includes a phosphorescent material or a TADF-type material; and / or, the host material includes at least one material; wherein the sensitizer includes a phosphorescent material; wherein the sensitizer includes platinum; wherein the glass transition temperature of the host material is greater than 110 degrees Celsius; wherein the host material contains silicon and / or deuteration; wherein the host material includes a first host material and a second host material; wherein the hole mobility of the first host material is higher than that of the second host material, and the electron mobility of the second host material is higher than that of the first host material; wherein the volume ratio of the first host material to the second host material is between 2:8 and 8:2; wherein the first host material and the second host material form an excimer complex, and the excimer complex is TADF-type.

[0011] The total doping concentration of the sensitizer is 2% to 20%, and / or the total doping concentration of the fluorescent guest material is 0.2% to 4%; the total doping concentration of the sensitizer is 3% to 15%, and / or the total doping concentration of the fluorescent guest material is 0.2% to 2%; the total doping concentration of the sensitizer is 8% to 12%, and / or the total doping concentration of the fluorescent guest material is 0.5% to 1%.

[0012] The light color of the sensitizer is the same as that of the fluorescent guest material.

[0013] The sensitizer has a first concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and a second concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the first and second concentration distribution lines symmetrically distributed; and / or, the fluorescent guest has a third concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and a fourth concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the third and fourth concentration distribution lines symmetrically distributed.

[0014] The sensitizer includes a phosphorescent material, wherein the triplet exciton energy level of the phosphorescent material is greater than or equal to the singlet exciton energy level of the fluorescent guest material; wherein the energy level difference between the singlet exciton energy level of the fluorescent guest material and the triplet exciton energy level of the fluorescent guest material is less than or equal to 0.2 eV.

[0015] The fluorescent guest material contains deuterated and / or tert-butyl groups.

[0016] The thickness of the light-emitting layer ranges from 10 to 35 nm.

[0017] The thickness of the light-emitting layer ranges from 13 to 30 nm.

[0018] The light-emitting device further includes an electron blocking layer with a thickness ranging from 2 to 10 nm; or a thickness ranging from 3 to 8 nm; the host material includes a first host material and a second host material, wherein the first host material is either a P-type host material or an N-type host material, and the second host material is either a P-type host material or an N-type host material, and the material of the electron blocking layer is the same as the P-type host material; it also includes a hole transport layer, wherein the HOMO energy level of the electron blocking layer material is located between the HOMO energy level of the host material and the HOMO energy level of the hole transport layer material.

[0019] The light-emitting device further includes an electron transport layer, a hole blocking layer, an electron injection layer, and a hole transport layer; the thickness of the electron transport layer ranges from 10 to 50 nm; and / or, the thickness of the hole blocking layer ranges from 0 to 10 nm; and / or, the thickness of the electron injection layer ranges from less than 2 nm; and / or, the thickness of the hole transport layer ranges from 100 to 140 nm; wherein, the thickness of the electron transport layer ranges from 20 to 40 nm; and / or, the thickness of the hole blocking layer ranges from 2 to 8 nm; and / or, the thickness of the electron injection layer ranges from less than 1 nm; and / or, the thickness of the hole transport layer ranges from 110 to 130 nm.

[0020] The light-emitting device further includes a light extraction layer with a refractive index between 1.8 and 2.5; and / or, the thickness of the light extraction layer is between 50 nm and 100 nm; wherein the refractive index of the light extraction layer is between 2.1 and 2.3, and the thickness of the light extraction layer is between 60 nm and 75 nm.

[0021] The light-emitting device includes a light-emitting functional layer, which includes at least two light-emitting units. The at least two light-emitting units are stacked in a direction perpendicular to the light-emitting layer, and a charge-generating layer is disposed between two adjacent light-emitting units. At least one light-emitting unit includes a light-emitting layer. The light-emitting functional layer of all light-emitting devices includes at least two light-emitting units. The number of light-emitting units contained in the at least two light-emitting devices is different. All light-emitting units include at least one light-emitting layer.

[0022] Specifically, in the 0~0.4D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to decrease; and / or, in the 0.6D~D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to increase.

[0023] Specifically, in the 0.4D~0.5D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to increase; and / or, in the 0.5D~0.6D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to decrease.

[0024] To solve the above-mentioned technical problems, the second technical solution adopted in this application is to provide a light-emitting device, including: a first electrode; a second electrode; at least one light-emitting layer disposed between the first electrode and the second electrode, the light-emitting layer including a host material, a sensitizer, and a fluorescent guest material; the emission peak wavelength range of the light-emitting layer is 430nm~470nm; the thickness of the light-emitting layer is defined as D, the thickness of the surface of the light-emitting layer near the first electrode is defined as 0, the thickness of the surface of the light-emitting layer near the second electrode is defined as D, in the thickness region of 0~0.4D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material shows an increasing trend; and / or, in the thickness region of 0.6D~D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material shows a decreasing trend.

[0025] Specifically, in the 0~0.4D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10~100; and / or, in the 0.4D~0.6D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 80~100; and / or, in the 0.6D~D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10~100.

[0026] The sensitizer has a first concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and a second concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the first and second concentration distribution lines symmetrically distributed; and / or, the fluorescent guest has a third concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and a fourth concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the third and fourth concentration distribution lines symmetrically distributed.

[0027] To solve the above-mentioned technical problems, the third technical solution adopted in this application is to provide a display panel including the above-mentioned light-emitting device.

[0028] The beneficial effects of this application are as follows: Unlike related technologies, this application provides a light-emitting device and a display panel. By making the light-emitting layer include a host material, a sensitizer, and a fluorescent guest material, and limiting the emission peak wavelength range of the light-emitting layer to 430nm~470nm, the sensitizer can be introduced as an energy transfer bridge to fully capture and efficiently transfer excitons in the light-emitting layer to the narrow-spectrum fluorescent guest material for emission. This achieves a high exciton utilization rate while maintaining the narrow spectrum and high color purity of the fluorescent material itself, thereby improving the blue light emission efficiency of the blue light-emitting device. Meanwhile, by setting the ratio of sensitizer doping concentration to fluorescent guest material doping concentration to 10-100 in the 0-0.4D thickness region of the luminescent layer; and / or, setting the ratio of sensitizer doping concentration to fluorescent guest material doping concentration to 0.5-15 or 80-100 in the 0.4D-0.6D thickness region of the luminescent layer; and / or, setting the ratio of sensitizer doping concentration to fluorescent guest material doping concentration to 10-100 in the 0.6D-D thickness region of the luminescent layer, the relative concentration ratio of sensitizer to fluorescent guest material can be flexibly adjusted in different thickness regions of the luminescent layer, achieving differentiated exciton capture and energy transfer modes. This improves blue light emission efficiency while also meeting the comprehensive performance requirements of high color purity and device lifetime. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the example description will be briefly introduced below. Obviously, the accompanying 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.

[0030] Figure 1 This is a schematic diagram of the structure of a display panel according to one embodiment of this application; Figure 2 yes Figure 1 A schematic diagram of a partial film layer cross-section in the BB direction of a local area of ​​a display panel fabricated by the VIP process; Figure 3 yes Figure 1 A schematic diagram of a partial film layer cross-section in the BB direction of a local area of ​​a display panel fabricated by the FMM process; Figure 4 yes Figure 2 or Figure 3 A schematic diagram of a specific structure of the light-emitting functional layer; Figure 5 yes Figure 2 or Figure 3 Another specific structural diagram of the light-emitting functional layer; Figure 6 yes Figure 5 A schematic diagram of a specific structure of the first light-emitting layer in the middle; Figure 7 yes Figure 2 or Figure 3 A schematic diagram of a specific structure of a light-emitting device; Figure 8 This is a schematic diagram showing the changing trend of the doping concentration ratio of the sensitizer to the fluorescent guest material in the first embodiment of the first embodiment of this application; Figure 9 This is a schematic diagram showing the changing trend of the doping concentration ratio of the sensitizer to the fluorescent guest material in the second embodiment of the first embodiment of this application; Figure 10 This is a schematic diagram showing the trend of doping concentration changes of the sensitizer and the fluorescent guest material in the third embodiment of the first embodiment of this application; Figure 11a This is a schematic diagram of the concentration distribution lines corresponding to the sensitizer and the fluorescent guest material in the fourth embodiment of the first embodiment of this application; Figure 11b This is a schematic diagram of the concentration distribution lines corresponding to the sensitizer and the fluorescent guest material in the fourth embodiment of the first embodiment of this application; Figure 12This is a schematic diagram showing the changing trend of the doping concentration ratio of the sensitizer to the fluorescent guest material in the first embodiment of the second embodiment of this application; Figure 13 This is a schematic diagram showing the trend of doping concentration changes of the sensitizer and the fluorescent guest material in the second embodiment of the second embodiment of this application; Figure 14a This is a schematic diagram of the concentration distribution lines corresponding to the sensitizer and the fluorescent guest material in the second embodiment of the first embodiment of this application; Figure 14b This is a schematic diagram of the concentration distribution lines corresponding to the sensitizer and the fluorescent guest material in the second embodiment of the first embodiment of this application. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] It should be noted that similar reference numerals 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. It should be noted that, unless otherwise specified, different features in the embodiments of this application can be combined with each other.

[0034] For ease of understanding, the accompanying diagram shows the mutually orthogonal X-axis, Y-axis, and Z-axis. The direction along the X-axis is called the X-direction, the direction along the Y-axis is called the Y-direction, and the direction along the Z-axis is called the Z-direction. The Z-direction is the normal direction relative to the plane containing the X and Y directions. Furthermore, a view where various elements are observed parallel to the plane containing the X and Y directions is called a top view. Alternatively, the planes in the X and Y directions can be planes parallel to the display surface of the display panel, and the Z-direction can be a direction parallel to the thickness direction of the display panel.

[0035] Figure 1This is a schematic diagram of the structure of a display panel according to one embodiment of this application. The display panel 100 can be an organic light-emitting diode (OLED) display panel or a quantum dot light-emitting diode (QLED) display panel. The display panel 100 includes a display area AA with display function and a non-display area NA.

[0036] The display area AA of the display panel 100 can be rectangular, square, circular, oval, or other shapes.

[0037] The display area AA includes a plurality of pixels PX arranged in the X and Y directions. Each pixel PX includes a plurality of sub-pixels SPX displaying different colors. In some embodiments, a pixel PX includes a first sub-pixel SPX1, a second sub-pixel SPX2, and a third sub-pixel SPX3. For example, the first sub-pixel SPX1 is a blue sub-pixel, the second sub-pixel SPX2 is a green sub-pixel SPX2, and the third sub-pixel SPX3 is a red sub-pixel SPX3. In some embodiments, in addition to sub-pixels SPX1, SPX2, and SPX3, a pixel PX also includes sub-pixels SPX that emit white or other colors of light.

[0038] A sub-pixel (SPX) includes a pixel circuit and a light-emitting device driven by the pixel circuit to emit light of the corresponding color. The first sub-pixel (SPX1) includes a first light-emitting device, the second sub-pixel (SPX2) includes a second light-emitting device, and the third sub-pixel (SPX3) includes a third light-emitting device. One pixel circuit drives at least one light-emitting device to emit light. For example, the display area AA includes a normal display area and a light-transmitting display area. The light-transmitting display area is a display area set according to a corresponding sensor and has light-transmitting properties, while the normal display area is a display area not set according to a corresponding sensor. In the normal display area, one pixel circuit drives one light-emitting device to emit light, and in the light-transmitting display area, one pixel circuit drives one or more light-emitting devices to emit light.

[0039] In this embodiment, the display panel 100 is fabricated using either VIP (Vertical Integration Process) or FMM (Fine Metal Mask) technology.

[0040] Please see Figure 2 and Figure 3 , Figure 2 yes Figure 1 A schematic diagram of a partial film layer cross-section in the BB direction of a local area of ​​a display panel fabricated using the VIP process. Figure 3 yes Figure 1A schematic diagram of a partial film layer cross-section in the BB direction of a local area of ​​a display panel fabricated by the FMM process.

[0041] like Figure 2 As shown, the display panel 100 includes a substrate 10, a pixel defining layer 20, an isolation structure 40, and a plurality of light-emitting devices 30.

[0042] In one embodiment, a pixel defining layer 20 is disposed on a substrate 10, and an isolation structure 40 is disposed on the pixel defining layer 20, forming a plurality of isolation openings. These isolation openings include a plurality of first isolation openings 41, a plurality of second isolation openings 42, and a plurality of third isolation openings 43. The pixel defining layer 20 has pixel openings communicating with the isolation openings. Specifically, the pixel defining layer 20 has a first pixel opening communicating with the first isolation opening 41, a second pixel opening communicating with the second isolation opening 42, and a third pixel opening communicating with the third isolation opening 43. A plurality of light-emitting devices 30 are located on one side of the substrate 10, and the plurality of light-emitting devices 30 include a plurality of first light-emitting devices 30a, a plurality of second light-emitting devices 30b, and a plurality of third light-emitting devices 30c. The first light-emitting devices 30a are disposed corresponding to the first isolation opening 41, the second light-emitting devices 30b are disposed corresponding to the second isolation opening 42, and the third light-emitting devices 30c are disposed corresponding to the third isolation opening 43. In one embodiment, one light-emitting device 30 is correspondingly disposed with one isolation opening. For example, a first light-emitting device 30a is correspondingly disposed with a first isolation opening 41, a second light-emitting device 30b is correspondingly disposed with a second isolation opening 42, and a third light-emitting device 30c is correspondingly disposed with a third isolation opening 43. At least a portion of the first light-emitting device 30a is disposed within the corresponding first isolation opening 41, at least a portion of the second light-emitting device 30b is disposed within the corresponding second isolation opening 42, and at least a portion of the third light-emitting device 30c is disposed within the corresponding third isolation opening 43. In another embodiment, multiple light-emitting devices 30 are correspondingly disposed with one isolation opening. For example, multiple light-emitting devices 30 with the same emission color are corresponding to one isolation opening.

[0043] like Figure 3 As shown, the display panel 100 includes a substrate 10, a pixel defining layer 20, and a plurality of light-emitting devices 30.

[0044] In one embodiment, a pixel defining layer 20 is disposed on a substrate 10, and the pixel defining layer 20 has a plurality of pixel openings, including a plurality of first pixel openings 21, a plurality of second pixel openings 22, and a plurality of third pixel openings 23. A plurality of light-emitting devices 30 are located on one side of the substrate 10, and the plurality of light-emitting devices 30 include a plurality of first light-emitting devices 30a, a plurality of second light-emitting devices 30b, and a plurality of third light-emitting devices 30c. In one embodiment, one light-emitting device 30 is correspondingly disposed to one pixel opening. For example, the first light-emitting device 30a is correspondingly disposed to one first pixel opening 21, the second light-emitting device 30b is correspondingly disposed to one second pixel opening 22, and the third light-emitting device 30c is correspondingly disposed to one third pixel opening 23. At least a portion of the first light-emitting device 30a is disposed within the corresponding first pixel opening 21, at least a portion of the second light-emitting device 30b is disposed within the corresponding second pixel opening 22, and at least a portion of the third light-emitting device 30c is disposed within the corresponding third pixel opening 23. In another embodiment, multiple light-emitting devices 30 are configured to correspond to the same pixel opening. For example, multiple light-emitting devices 30 with the same light emission color are configured to correspond to the same pixel opening.

[0045] In one embodiment, the first light-emitting device 30a, the second light-emitting device 30b, and the third light-emitting device 30c emit light of different colors. Each of the three devices includes a first electrode 31, a light-emitting functional layer 32, and a second electrode 33 stacked together. The first electrode 31 is disposed on the substrate 10, and a pixel defining layer 20 covers the end of the first electrode 31. A pixel opening is provided on the pixel defining layer 20, and the first electrode 31 is located within the pixel opening, exposed through it. The light-emitting functional layer 32 of the first light-emitting device 30a, the second light-emitting device 30b, and the third light-emitting device 30c covers the sidewall of the pixel opening of the pixel defining layer 20 and the side of the pixel defining layer 20 facing away from the substrate 10. Each light-emitting functional layer 32 is located within the pixel opening and is in contact with the first electrode 31.

[0046] The first electrode 31 can be an anode, and the second electrode 33 can be a cathode. The first electrode 31 of each light-emitting device 30 can be connected to the pixel circuit through a via, so that the pixel circuit drives the light-emitting device 30 to emit light.

[0047] In order for the light-emitting functional layer 32 to emit light, a pixel voltage is provided to the first electrode 31 and a common voltage is provided to the second electrode 33, forming a potential difference between the first electrode 31 and the second electrode 33, so that the light-emitting functional layer 32 disposed between the first electrode 31 and the second electrode 33 emits light. In one embodiment, if a potential difference is formed between the first electrode 31 and the second electrode 33 of the first light-emitting device 30a, the light-emitting layer of the light-emitting functional layer 32 emits blue light; if a potential difference is formed between the first electrode 31 and the second electrode 33 of the second light-emitting device 30b, the light-emitting layer of the light-emitting functional layer 32 emits green light; and if a potential difference is formed between the first electrode 31 and the second electrode 33 of the third light-emitting device 30c, the light-emitting layer of the light-emitting functional layer 32 emits red light.

[0048] In some embodiments, the emission peak wavelength range of the emission layer of the first light-emitting device 30a (blue light-emitting device) is 430nm to 470nm, for example, 430, 440, 450, 460, or 470nm. The emission peak wavelength range of the emission layer of the second light-emitting device 30b (green light-emitting device) is 500nm to 560nm, for example, 500, 510, 520, 530, 540, 550, or 560nm. The emission peak wavelength range of the emission layer of the third light-emitting device 30c (red light-emitting device) is 600nm to 650nm, for example, 600, 610, 620, 630, 640, or 650nm.

[0049] In some embodiments, the light-emitting functional layer 32 may include a single light-emitting layer or a stacked light-emitting structure comprising multiple light-emitting layers.

[0050] In some embodiments, the light-emitting functional layer 32 includes a light-emitting unit, and the light-emitting unit includes a light-emitting layer. Specifically, please refer to... Figure 4 , Figure 4 yes Figure 2 or Figure 3 A schematic diagram of a specific structure of the light-emitting functional layer 32. The light-emitting functional layer 32 includes a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), an emitting layer (EML), a hole blocking layer (HBL), an electron transport layer (ETL), and an electron injection layer (EIL) stacked along the direction away from the substrate 10 (i.e., the Z direction).

[0051] In some embodiments, the thickness of the hole injection layer in the light-emitting functional layer 32 is 5~15nm, for example 5, 8, 10, 12 or 15nm.

[0052] In some embodiments, the thickness of the hole transport layer in the light-emitting functional layer 32 is 100~140nm, for example 100, 110, 120, 130 or 140nm. In some specific embodiments, the thickness of the hole transport layer is 110~130nm.

[0053] In some embodiments, the thickness of the electron blocking layer in the light-emitting functional layer 32 of the first light-emitting device 30a is 2~10nm, for example 2, 3, 4, 5, 6, 7, 8 or 10nm.

[0054] In some embodiments, the electron blocking layer in the light-emitting functional layer 32 of the first light-emitting device 30a has a thickness of 3-8 nm, for example, 3, 4, 5, 6, 7, or 8 nm. In other embodiments, the electron blocking layer in the light-emitting functional layer 32 of the second light-emitting device 30b has a thickness of 30-60 nm, for example, 30, 40, 50, or 60 nm. In still other embodiments, the electron blocking layer in the light-emitting functional layer 32 of the third light-emitting device 30c has a thickness of 70-130 nm, for example, 70, 80, 9, 0, 100, 11, 120, or 130 nm.

[0055] In some embodiments, the thickness of the light-emitting functional layer 32 of the first light-emitting device 30a is 10~35nm, for example 10, 13, 15, 17, 20, 22, 25, 28, 30 or 35nm.

[0056] In some embodiments, the thickness of the light-emitting functional layer 32 of the first light-emitting device 30a is 13-30 nm, for example, 13, 15, 17, 20, 22, 25, 28, or 30 nm. In other embodiments, the thickness of the light-emitting functional layer 32 of the second light-emitting device 30b is 25-50 nm, for example, 25, 27, 30, 35, 40, 45, or 50 nm. In still other embodiments, the thickness of the light-emitting functional layer 32 of the third light-emitting device 30c is 30-50 nm, for example, 30, 35, 40, 45, or 50 nm.

[0057] In some embodiments, the thickness of the hole blocking layer in the light-emitting functional layer 32 is 0~10nm, for example 2, 4, 6, 8 or 10nm. In some specific embodiments, the thickness of the hole blocking layer is 2~8nm.

[0058] In some embodiments, the thickness of the electron transport layer in the light-emitting functional layer 32 is 10~50 nm, for example 10, 15, 17, 20, 22, 25, 28, 30, 35, 40, 45 or 50 nm. In some specific embodiments, the thickness of the electron transport layer is 20~40 nm.

[0059] In some embodiments, the thickness of the electron injection layer in the light-emitting functional layer 32 is less than 2 nm, for example, 0.5, 1, 1.5, or 2 nm. In some specific embodiments, the thickness of the electron injection layer in the light-emitting functional layer 32 is less than 1 nm.

[0060] In some embodiments, the light-emitting functional layer 32 includes at least two light-emitting units, which are stacked in a direction perpendicular to the light-emitting layer, and a charge-generating layer is disposed between two adjacent light-emitting units. Each light-emitting unit includes at least one light-emitting layer.

[0061] Specifically, please refer to Figure 5 , Figure 5 yes Figure 2 or Figure 3 Another specific structural diagram of the light-emitting functional layer. The light-emitting functional layer 32 includes a hole injection layer (HIL), a first hole transport layer (HTL1), a first electron blocking layer (EBL1), a first light-emitting layer (EML1), a first hole blocking layer (HBL1), a first electron transport layer (ETL1), a charge generation layer (CGL), a second hole transport layer (HTL2), a second electron blocking layer (EBL2), a second light-emitting layer (EML2), a second hole blocking layer (HBL2), a second electron transport layer (ETL2), and an electron injection layer (EIL) stacked along the direction away from the substrate 10 (i.e., the Z direction).

[0062] The light-emitting functional layer 32 includes a first light-emitting unit 321 and a second light-emitting unit 322. The first light-emitting unit 321 includes a hole injection layer, a first hole transport layer, a first electron blocking layer, a first light-emitting layer, a first hole blocking layer, and a first electron transport layer. The second light-emitting unit 322 includes a second hole transport layer, a second electron blocking layer, a second light-emitting layer, a second hole blocking layer, a second electron transport layer, and an electron injection layer. The first light-emitting layer and the second light-emitting layer emit light of the same color.

[0063] In some specific embodiments, both the first light-emitting layer and the second light-emitting layer are single light-emitting layers.

[0064] In other embodiments, at least one of the first and second light-emitting layers includes a first and a second light-emitting sub-layer stacked together, and the first and second light-emitting sub-layers emit light of the same color. For details, please refer to... Figure 6 , Figure 6 yes Figure 5 A schematic diagram of a specific structure of the first light-emitting layer. In this embodiment, the first light-emitting layer EML1 includes a first sublayer EML1a and a second sublayer EML1b stacked together.

[0065] In some specific embodiments, the light-emitting functional layer 32 of all light-emitting devices 30 of the display panel 100 includes at least two light-emitting units. That is, all first light-emitting devices 30a (blue light-emitting devices), all second light-emitting devices 30b (green light-emitting devices), and all third light-emitting devices 30c (red light-emitting devices) in the display panel 100 adopt a stacked structure, and each light-emitting device 30 has at least two light-emitting units.

[0066] In some specific embodiments, at least two light-emitting devices 30 contain different numbers of light-emitting units. In some embodiments, light-emitting devices 30 of different colors can use different numbers of light-emitting units. For example, the first light-emitting device 30a (blue light-emitting device) has a shorter lifespan, so three light-emitting units can be connected in series to improve its lifespan; while the third light-emitting device 30c (red light-emitting device) and the second light-emitting device 30b (green light-emitting device) have better lifespans and can be configured with only two light-emitting units. This differentiated design can optimize power consumption and performance.

[0067] Please see Figure 7 , Figure 7 yes Figure 2 or Figure 3 A schematic diagram of a specific structure of a light-emitting device. The light-emitting device 30 is provided with a first electrode 31, a light-emitting functional layer 32, a second electrode 33, a light extraction layer 34 and an encapsulation layer 35 stacked sequentially along the direction away from the substrate 10 (i.e., the Z direction).

[0068] In some embodiments, the refractive index of the light extraction layer is between 1.8 and 2.5, such as 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5, and / or the thickness of the light extraction layer 34 is between 50 nm and 100 nm, such as 50, 60, 70, 80, 90 or 100 nm.

[0069] In some specific embodiments, the thickness of the light extraction layer 34 is between 60nm and 75nm, for example, 60, 62, 65, 67, 69, 71, 73, and 75nm.

[0070] In some specific embodiments, the refractive index of the light extraction layer 34 is between 2.1 and 2.3, for example 2.1, 2.15, 2.2, 2.25 or 2.3.

[0071] In some specific embodiments, the thickness of the encapsulation layer 35 is 30~120nm, for example 30, 40, 50, 60, 70, 80, 90, 100, 110 or 120nm.

[0072] In related technologies, blue OLED devices typically use fluorescent materials as luminescent dopants and utilize a triplet-triplet annihilation (TTA) mechanism to partially recover triplet (T1) excitons. Specifically, the host material and fluorescent dopant are co-deposited to form the luminescent layer. Electrons and holes recombine within the host material to generate excitons, and the exciton energy is transferred to the fluorescent dopant for radiative emission. The TTA mechanism generates a singlet (S1) exciton through the collision and fusion of two triplet (T1) excitons, theoretically increasing the exciton utilization rate from 25% in traditional fluorescence to 62.5%.

[0073] However, even with the TTA fluorescence emission mechanism, the theoretical upper limit of exciton utilization in blue OLED devices is only 62.5%, with the remaining approximately 37.5% of exciton energy dissipated in a non-radiative form and unable to be effectively utilized, thus affecting the blue light emission efficiency.

[0074] Unlike related technologies, in this embodiment, the light-emitting layer of the first light-emitting device 30a includes a host material, a sensitizer, and a fluorescent guest material. The emission peak wavelength range of the light-emitting layer is 430nm~470nm, for example, 430, 440, 450, 460 or 470nm.

[0075] The sensitizer and the fluorescent guest material both emit blue light, which is the same color.

[0076] In this process, the sensitizer and the fluorescent guest material are doped into the host material. The host material does not emit light; its role is to transfer energy to the sensitizer, and then the sensitizer fully transfers the energy to the fluorescent guest material, causing the fluorescent guest material to emit light.

[0077] Specifically, under the influence of an electric field, electrons and holes are injected from the cathode and anode of the first light-emitting device 30a, respectively, and recombine in the light-emitting layer to form excitons. Excitons are quasi-particles with a certain amount of energy. According to spin statistics, 25% of these excitons are singlet (S1) excitons, and 75% are triplet (T1) excitons. The host material collects and concentrates energy, transferring all the energy of its generated singlet and triplet excitons to the sensitizer. The sensitizer effectively captures the excitons and concentrates all the received energy, achieving a near 100% exciton utilization rate. Subsequently, the sensitizer efficiently transfers the exciton energy to the singlet state of the fluorescent guest material. After the molecules of the fluorescent guest material transition to the excited singlet state, they return to the ground state through radiative transition, emitting blue photons.

[0078] Understandably, since the final blue light emission originates from the S1→S0 radiative transition of the fluorescent guest material, it possesses the advantages of narrow spectrum and high color purity of fluorescent materials, thus achieving high-purity blue light emission. Furthermore, by fully capturing excitons through the sensitizer, the energy of triplet excitons, which would otherwise be unusable, can be effectively recovered through the sensitization effect of the sensitizer and efficiently transferred to the narrow-spectrum fluorescent guest material for luminescence. Therefore, while maintaining the narrow spectrum and high color purity of the fluorescent material itself, it breaks through the theoretical upper limit of 62.5% exciton utilization in the traditional TTA fluorescence mechanism and achieves nearly 100% exciton utilization, thereby significantly improving the luminous efficiency of the first light-emitting device 30a (blue light-emitting device).

[0079] In this application, the thickness of the light-emitting layer is defined as D, the thickness of the surface of the light-emitting layer near the first electrode is defined as 0, and the thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0~0.4D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100; and / or, in the thickness region of 0.4D~0.6D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 0.5~15 or 80~100; and / or, in the thickness region of 0.6D~D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100.

[0080] The doping concentrations and their ratios can be measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS). TOF-SIMS is a highly sensitive surface analysis technique. Its working principle is as follows: a primary ion beam bombards the sample surface, and the sputtered secondary ions are analyzed by a time-of-flight mass spectrometer to obtain the mass spectral signals of each element. As the ion beam continues to bombard, the sample surface is peeled off layer by layer, thus obtaining the depth distribution curve of each component concentration along the film thickness direction. Because TOF-SIMS has sub-nanometer peeling precision, tens or even hundreds of data points can be obtained in a light-emitting layer with a thickness of tens of nanometers. Each data point corresponds to the doping concentration of a sublayer, and the instantaneous ratio of the sensitizer to the fluorescent guest material doping concentration in each sublayer can be calculated. The ratio ranges defined above for each thickness region refer to the range of values ​​into which the instantaneous ratios of all sublayers within that region fall.

[0081] The sensitizer doping concentration refers to the percentage of the sensitizer's mass relative to the total mass of a specific sublayer of the emitting layer. The fluorescent guest material doping concentration refers to the percentage of the fluorescent guest material's mass relative to the total mass of a specific sublayer of the emitting layer. The ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration (referred to as the doping concentration ratio) is the instantaneous ratio of the sensitizer's mass percentage to the fluorescent guest material's mass percentage within the same sublayer. For example, if the sensitizer's mass percentage is 10% and the fluorescent guest material's mass percentage is 1%, then the ratio of the sensitizer's doping concentration to the fluorescent guest material's doping concentration in that sublayer is 10, meaning the ratio of the sensitizer's doping concentration to the fluorescent guest material's doping concentration in that sublayer is 10.

[0082] The aforementioned doping concentration ratio range refers to the range of values ​​into which the instantaneous ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration falls within a single sublayer in each thickness region, rather than the average ratio of all sublayers in that thickness region.

[0083] Understandably, since the doping concentration of each doped material in the light-emitting layer varies along the thickness direction, the instantaneous ratio of different sublayers within the same thickness range may differ. Using a ratio range can more accurately reflect the overall distribution characteristics and variation range of the doping concentration ratio within that range.

[0084] In this application, within a thickness region of 0~0.4D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100. This means that within a thickness region of 0~0.4D, the instantaneous ratio of all sublayers falls within the range of 10~100, which indicates that the instantaneous ratio of each sublayer in this region is at least 10 and at most 100.

[0085] In some embodiments, within a thickness region of 0 to 0.4D, the instantaneous ratio of the multiple sublayers can be 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100. In still other embodiments, within a thickness region of 0 to 0.4D, the instantaneous ratio of the multiple sublayers can also be any value from 10 to 100.

[0086] In some embodiments, within a thickness region of 0~0.4D, the range of instantaneous ratios of multiple sublayers can be 20~80, meaning the minimum instantaneous ratio of each sublayer within this region is 20 and the maximum is 80, and the instantaneous ratios of multiple sublayers can be any value between 20 and 80. In still other embodiments, within a thickness region of 0~0.4D, the range of instantaneous ratios of multiple sublayers can be 30~70, meaning the minimum instantaneous ratio of each sublayer within this region is 30 and the maximum is 70, and the instantaneous ratios of multiple sublayers can be any value between 30 and 70.

[0087] In this application, in the thickness region of the luminescent layer from 0.4D to 0.6D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 0.5 to 15. This means that in the thickness region of 0.4D to 0.6D, the instantaneous ratio of all sublayers falls within the range of 0.5 to 15, that is, the instantaneous ratio of each sublayer in this region is at least 0.5 and at most 15.

[0088] In some embodiments, within a thickness region of 0.4D to 0.6D, the instantaneous ratio of the multiple sublayers can be 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. In still other embodiments, within a thickness region of 0.4D to 0.6D, the instantaneous ratio of the multiple sublayers can also be any value from 0.5 to 15.

[0089] In some embodiments, within a thickness region of 0.4D to 0.6D, the range of instantaneous ratios of multiple sublayers can be 0.5 to 10, meaning the minimum instantaneous ratio of each sublayer within this region is 0.5 and the maximum is 10, and the instantaneous ratios of the multiple sublayers can be any value between 0.5 and 10. In still other embodiments, within a thickness region of 0.4D to 0.6D, the range of instantaneous ratios of multiple sublayers can be 10 to 15, meaning the minimum instantaneous ratio of each sublayer within this region is 10 and the maximum is 15, and the instantaneous ratios of the multiple sublayers can be any value between 10 and 15.

[0090] In this application, in the thickness region of the luminescent layer of 0.4D to 0.6D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 80 to 100. This means that in the thickness region of 0.4D to 0.6D, the instantaneous ratio of all sublayers falls within the range of 80 to 100, that is, the instantaneous ratio of each sublayer in this region is at least 80 and at most 100.

[0091] In some embodiments, within a thickness region of 0.4D to 0.6D, the instantaneous ratio of the multiple sublayers can be 80, 85, 90, 95, or 100. In still other embodiments, within a thickness region of 0.4D to 0.6D, the instantaneous ratio of the multiple sublayers can also be any value between 80 and 100.

[0092] In some embodiments, within a thickness region of 0.4D to 0.6D, the range of values ​​corresponding to the instantaneous ratios of multiple sublayers can be 80 to 90, meaning the minimum instantaneous ratio of each sublayer within this region is 80 and the maximum is 90, and the instantaneous ratios of multiple sublayers can be any value between 80 and 90. In still other embodiments, within a thickness region of 0.4D to 0.6D, the range of values ​​corresponding to the instantaneous ratios of multiple sublayers can be 85 to 95, meaning the minimum instantaneous ratio of each sublayer within this region is 85 and the maximum is 95, and the instantaneous ratios of multiple sublayers can be any value between 85 and 95.

[0093] In this application, within a thickness region of 0.6D to D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100. This means that within a thickness region of 0.6D to D, the instantaneous ratio of all sublayers falls within the range of 10 to 100, which indicates that the instantaneous ratio of each sublayer in this region is at least 10 and at most 100.

[0094] In some embodiments, within a thickness region of 0.6D to D, the instantaneous ratio of the multiple sublayers can be 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100. In still other embodiments, within a thickness region of 0.6D to D, the instantaneous ratio of the multiple sublayers can also be any value from 10 to 100.

[0095] In some embodiments, within a thickness region of 0.6D to D, the range of instantaneous ratios of multiple sublayers can be 20 to 80, meaning the minimum instantaneous ratio of each sublayer within this region is 20 and the maximum is 80, and the instantaneous ratios of multiple sublayers can be any value between 20 and 80. In still other embodiments, within a thickness region of 0.6D to D, the range of instantaneous ratios of multiple sublayers can be 30 to 70, meaning the minimum instantaneous ratio of each sublayer within this region is 30 and the maximum is 70, and the instantaneous ratios of multiple sublayers can be any value between 30 and 70.

[0096] Understandably, in regions with low doping concentration ratios (e.g., near 0.5), the doping concentration of the fluorescent guest material is relatively high, while the doping concentration of the sensitizer is relatively low. The sensitizer in this region can capture excitons nearby and efficiently transfer energy to the adjacent fluorescent guest material via short-range energy transfer. This short energy transfer path and low loss are beneficial for improving blue light emission efficiency in this region. Conversely, in regions with high doping concentration ratios (e.g., near 100), the doping concentration of the sensitizer is much higher than that of the fluorescent guest material. The sensitizer can fully capture excitons and form an energy buffer before smoothly transferring energy to the fluorescent guest material for luminescence, reducing exciton quenching losses. By varying the doping concentration ratio, which characterizes the instantaneous concentration relationship, along the thickness of the luminescent layer, different doping materials can be made to play dominant roles in different regions, thus balancing the overall performance requirements of blue light emission efficiency and device lifetime.

[0097] Understandably, by limiting the doping concentration ratio of the sensitizer to the fluorescent guest material to 10-100 in the 0-0.4D thickness region and the 0.6D-D thickness region of the emitting layer, a higher doping concentration of the sensitizer relative to the fluorescent guest material can be achieved in both regions of the emitting layer. This allows for the full capture of excitons generated by the host material and efficient energy transfer to the fluorescent guest material. This improves exciton utilization while maintaining the narrow spectrum and high color purity of the fluorescent shell material, thereby increasing the blue light emission efficiency of the first light-emitting device 30a. Simultaneously, since the sensitizer primarily functions as an energy transfer agent rather than a light-emitting agent in the emitting layer, it quickly transfers the captured exciton energy to the adjacent fluorescent guest material and then returns to the ground state. The residence time in the excited state is significantly shortened, reducing degradation reactions such as molecular degradation caused by prolonged exposure to high-energy excited states. Therefore, it does not adversely affect the lifespan of the blue light-emitting device.

[0098] Unlike red and green light-emitting materials, blue light-emitting materials have a wider band gap and higher exciton energy. If excitons remain directly on the host material or fluorescent guest material for a long time, it can easily lead to material degradation. This application sets the upper limit of the doping concentration ratio of the sensitizer to the fluorescent guest material to 100, which allows for the configuration of a higher concentration of sensitizer in the blue light-emitting layer. This enables the construction of a dense energy transfer network in the light-emitting layer. On the one hand, it can quickly capture excitons generated by the host material, shortening the residence time of high-energy excitons on the host material. On the other hand, it can also form an effective buffer protective layer around the fluorescent guest material, preferentially withstanding the impact of high-energy excitons, so as to smoothly transfer energy to the fluorescent guest material. This improves the exciton utilization rate while ensuring the service life of the first light-emitting device 30a (blue light-emitting device).

[0099] Understandably, by limiting the doping concentration ratio of the sensitizer to the fluorescent guest material to 0.5~15 within the 0.4D~0.6D thickness region of the emitting layer, the doping concentration of the sensitizer relative to the fluorescent guest material can be reduced in the central region of the emitting layer compared to the regions on both sides. The relative concentration of the fluorescent guest material in this region is increased, which is beneficial for efficiently receiving the energy transferred by the sensitizer and emitting a narrowband spectrum in the environment of low exciton concentration and low sensitizer concentration in the central region. This reduces the quenching loss that may be caused by high concentration of sensitizer, thereby further extending the device lifetime while improving the blue light emission efficiency.

[0100] Understandably, by limiting the doping concentration ratio of the sensitizer to the fluorescent guest material to 80-100 within the 0.4D-0.6D thickness region of the luminescent layer, the sensitizer can maintain a relatively high doping concentration relative to the fluorescent guest material in the central region of the luminescent layer. This ensures that the sensitizer can fully capture the excitons generated in the central region and form an energy buffer, and then efficiently transfer the energy to the fluorescent guest material. At the same time, it avoids quenching losses caused by the overlap of high-concentration sensitizer and high exciton density, thereby further improving the blue light emission efficiency.

[0101] In this application, the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited within thickness regions of 0~0.4D, 0.4~0.6D, and 0.6D~D of the luminescent layer. Alternatively, the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited within any one or both of these thickness regions.

[0102] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100. In the 0.4D-0.6D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 80-100. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100.

[0103] Understandably, in this embodiment, the doping concentration ratio range across the entire thickness of the luminescent layer is limited. Specifically, by limiting the sensitizer to fluorescent guest material doping concentration ratio to 10-100 in the 0-0.4D and 0.6D-1D thickness regions of the luminescent layer, the sensitizer can have a higher doping concentration relative to the fluorescent guest material in the two outer regions of the luminescent layer, thus fully capturing excitons generated by the host material and efficiently transferring energy to the fluorescent guest material. Simultaneously, by limiting the sensitizer to fluorescent guest material doping concentration ratio to 80-100 in the 0.4D-0.6D thickness region of the luminescent layer, a relatively high doping concentration ratio of the sensitizer relative to the fluorescent guest material can be maintained in the central region, ensuring that the sensitizer fully captures excitons generated in the central region and forms an energy buffer before efficiently transferring energy to the fluorescent guest material. Meanwhile, the higher sensitizer concentration and lower exciton concentration in the central region help mitigate quenching losses that might be caused by the overlap of high-concentration sensitizer and high exciton density, thereby improving exciton utilization. Correspondingly, the fluorescent guest material has a relatively high doping concentration in the interface regions on both sides, enabling efficient utilization of the high-concentration excitons near the interfaces for luminescence. Due to the short energy transfer path and low loss, this facilitates the formation of highly efficient luminescent regions on both sides of the luminescent layer.

[0104] Furthermore, since the doping concentration ratio of the two side regions ranges from 10 to 100, and the doping concentration ratio of the middle region ranges from 80 to 100, there is an overlap in the 80 to 100 range. This allows the doping concentration ratio of the middle region to be smoothly connected with that of the two side regions, so as to construct a continuous gradient change. This reduces exciton quenching caused by interface defects, thereby further improving exciton utilization and further enhancing blue light emission efficiency.

[0105] In other embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100. In the 0.4D-0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 80-100.

[0106] Understandably, in this embodiment, the doping concentration ratio range from the central region of the luminescent layer to the region near the first electrode is limited. The sensitizer has a higher doping concentration relative to the fluorescent guest material near the first electrode, enabling it to effectively capture excitons near this interface and efficiently transfer energy to the fluorescent guest material. In the central region, the sensitizer maintains a relatively high doping concentration ratio, effectively capturing excitons generated in the central region and forming an energy buffer. Since the doping concentration ratio range of 10-100 near the first electrode overlaps with the doping concentration ratio range of 80-100 in the central region, the doping concentration ratios in the central region and the region near the first electrode can be smoothly connected, improving energy transfer interruptions or exciton accumulation caused by abrupt changes in the ratio. The fluorescent guest material has a higher doping concentration near the first electrode, enabling efficient utilization of the high concentration of excitons near this interface for luminescence, which is beneficial for forming a highly efficient luminescent region in the luminescent layer near the first electrode. Meanwhile, the doping concentration ratio range is not limited in the region near the second electrode, which can retain process flexibility and is suitable for scenarios where the exciton distribution on this side is uncertain or where a simplified process is required.

[0107] In some other embodiments, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 80 to 100 in the 0.4D to 0.6D thickness region of the emissive layer. In the 0.6D to D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10 to 100.

[0108] Understandably, in this embodiment, the doping concentration ratio range from the central region of the luminescent layer to the region near the second electrode is limited. The sensitizer maintains a higher doping concentration ratio in the central region, effectively capturing excitons generated in the central region and forming an energy buffer. Near the second electrode, the sensitizer has a higher doping concentration ratio, effectively capturing excitons near this interface. Since the doping concentration ratio range of 80-100 in the central region overlaps with the doping concentration ratio range of 10-100 near the second electrode in the 80-100 range, the doping concentration ratios in the central region and the region near the second electrode can be smoothly connected, improving energy transfer interruptions or exciton accumulation caused by abrupt ratio changes. The fluorescent guest material has a higher doping concentration near the second electrode, enabling efficient utilization of the high concentration of excitons near this interface for luminescence, which is beneficial for forming a highly efficient luminescent region on the side of the luminescent layer near the second electrode. Simultaneously, the doping concentration ratio range is not limited in the region near the first electrode, preserving process flexibility and making it suitable for scenarios where the exciton distribution on this side is uncertain or where simplified processes are required.

[0109] In other embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100. In the 0.6D-D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100.

[0110] Understandably, in this embodiment, the doping concentration ratio of the two sides of the luminescent layer is limited. The sensitizer has a high doping concentration on both sides, enabling it to fully capture excitons near the interfaces and efficiently transfer energy to the fluorescent guest material. The fluorescent guest material has a relatively high doping concentration on both sides of the interface, allowing it to efficiently utilize the high concentration of excitons near the interfaces for luminescence, which is beneficial for forming high-efficiency luminescent regions on both sides of the luminescent layer. The doping concentration ratio in the central region is not limited and can be flexibly set according to actual needs. There are two possible variations in the doping concentration ratio in the central region of the luminescent layer: one is that the sensitizer has a lower proportion in the central region, while the fluorescent guest material occupies a larger proportion, which is beneficial for efficiently receiving energy and emitting a narrow-band spectrum in the low exciton concentration environment of the central region. The high concentration of sensitizer on both sides forms a buffer protective layer, thereby further extending the device lifetime while improving luminescence efficiency; the other is that the sensitizer maintains a high proportion in the central region, which can fully capture excitons generated in the central region and form an energy buffer. The fluorescent guest material has a higher concentration on both sides, resulting in a short energy transfer path and low loss, thereby further improving luminescence efficiency.

[0111] In some other embodiments, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100 in the 0 to 0.4D thickness region of the luminescent layer.

[0112] Understandably, in this embodiment, only the doping concentration ratio of the region of the luminescent layer near the first electrode is limited. The sensitizer dominates on this side, effectively capturing excitons near the interface and transferring them to the fluorescent guest material for luminescence. The fluorescent guest material has a higher doping concentration near the first electrode, enabling efficient utilization of the high concentration of excitons near this interface for luminescence, which is beneficial for forming a highly efficient luminescent region on the side of the luminescent layer near the first electrode. The doping concentration ratio range between the central region and the region near the second electrode is not limited, providing flexible control over exciton distribution.

[0113] In other embodiments, in the 0.6D to D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10 to 100.

[0114] Understandably, in this embodiment, only the doping concentration ratio of the region of the luminescent layer near the second electrode is limited. The sensitizer dominates on this side, effectively capturing excitons near the interface and transferring them to the fluorescent guest material for luminescence. The fluorescent guest material has a higher doping concentration near the second electrode, enabling efficient utilization of the high concentration of excitons near this interface for luminescence, which is beneficial for forming a highly efficient luminescent region on the side of the luminescent layer near the second electrode. Simultaneously, the doping concentration ratio between the central region and the region near the first electrode is not limited, providing flexible control over exciton distribution.

[0115] In some other embodiments, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 80 to 100 in the 0.4D to 0.6D thickness region of the luminescent layer.

[0116] Understandably, in this embodiment, only the doping concentration ratio in the central region of the light-emitting layer is limited, and the sensitizer maintains a high proportion in the central region, enabling it to concentrate and capture excitons and form an energy buffer. Meanwhile, the doping concentration ratio range is not limited in the two side regions, providing adaptability to different interfacial exciton distributions, and the process implementation is the simplest.

[0117] In other embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100. In the 0.4D-0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5-15. In the 0.6D-D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100.

[0118] Understandably, in this embodiment, the doping concentration ratio range across the entire thickness of the luminescent layer is limited. Specifically, by limiting the ratio range to 10-100 in the two side regions, the sensitizer can have a higher doping concentration relative to the fluorescent guest material, thus effectively capturing excitons near the interface and forming a buffer protective layer. By limiting the ratio range to 0.5-15 in the central region, the doping concentration ratio of the sensitizer is lower than in the two side regions, and the relative concentration of the fluorescent guest material in this region is increased. This allows for efficient reception of transferred exciton energy and emission of a narrow-band spectrum in the low exciton and sensitizer concentration environment in the central region, reducing quenching losses that may be caused by high-concentration sensitizers and facilitating the formation of a high-efficiency luminescent region in the central region of the luminescent layer. Simultaneously, the high concentration of sensitizer forming a buffer region near the interfaces on both sides reduces the exposure of the fluorescent guest material to the interface environment, lowering the probability of fluorescent guest material degradation. This, in addition to improving luminous efficiency, further extends the lifespan of the first luminescent device 30c (blue luminescent device).

[0119] Furthermore, since the doping concentration ratio of the two side regions ranges from 10 to 100, and the doping concentration ratio of the middle region ranges from 0.5 to 15, there is an overlap in the range of 10 to 15. Therefore, the doping concentration ratio of the middle region and the two side regions can be smoothly connected to form a continuous gradient change, thereby reducing exciton quenching caused by interface defects, further improving exciton utilization, and thus further improving blue light emission efficiency.

[0120] In other embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100. In the 0.4D-0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5-15.

[0121] Understandably, in this embodiment, the doping concentration ratio range from the central region of the luminescent layer to the region near the first electrode is limited. The sensitizer has a higher doping concentration near the first electrode, which effectively captures excitons near this interface and efficiently transfers energy to the fluorescent guest material. In the central region, the sensitizer doping concentration is lower than near the first electrode, and the relative concentration of the fluorescent guest material in this region is higher. This allows for efficient reception of transferred exciton energy and emission of a narrow-band spectrum in the low exciton and sensitizer concentration environment of the central region, reducing quenching losses that may be caused by high-concentration sensitizers and facilitating the formation of a highly efficient luminescent region in the central region of the luminescent layer. Since the doping concentration ratio range of 10~100 near the first electrode overlaps with the doping concentration ratio range of 0.5~15 in the central region (within the 10~15 range), the doping concentration ratios of the central region and the region near the first electrode can be smoothly connected, improving energy transfer interruptions or exciton accumulation caused by abrupt changes in the ratio. Meanwhile, the doping concentration ratio range is not limited in the region near the second electrode, which can retain process flexibility and is suitable for scenarios where the exciton distribution on this side is uncertain or where a simplified process is required.

[0122] In other embodiments, in the 0.4D to 0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5 to 15. In the 0.6D to D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10 to 100.

[0123] Understandably, in this embodiment, the doping concentration ratio range from the central region of the luminescent layer to the region near the second electrode is limited. The doping concentration ratio of the sensitizer in the central region is lower than that near the second electrode, while the relative concentration of the fluorescent guest material in this region is higher. This allows for efficient reception of transferred exciton energy and emission of a narrow-band spectrum in the low exciton and sensitizer concentration environment of the central region, reducing quenching losses that may be caused by high-concentration sensitizers and facilitating the formation of a highly efficient luminescent region in the central region of the luminescent layer. Near the second electrode, the sensitizer has a higher doping concentration ratio, which can effectively capture excitons near this interface and efficiently transfer energy to the fluorescent guest material. Since the doping concentration ratio range of 10~100 in the region near the second electrode overlaps with the doping concentration ratio range of 0.5~15 in the central region (within the 10~15 range), the doping concentration ratios of the central region and the region near the second electrode can be smoothly connected, improving energy transfer interruptions or exciton accumulation caused by abrupt changes in the ratio. Meanwhile, the doping concentration ratio range is not limited in the region near the first electrode, which can retain process flexibility and is suitable for scenarios where the exciton distribution on this side is uncertain or where process simplification is required.

[0124] In some other embodiments, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5 to 15 in the 0.4D to 0.6D thickness region of the luminescent layer.

[0125] Understandably, in this embodiment, only the doping concentration ratio in the central region of the luminescent layer is limited. The sensitizer doping concentration in the central region is relatively low, while the relative concentration of the fluorescent guest material in this region is higher. This allows for efficient reception of transferred exciton energy and emission of a narrow-band spectrum in the low exciton and sensitizer concentration environment of the central region, reducing quenching losses that may result from high-concentration sensitizers and facilitating the formation of a highly efficient luminescent region in the central area of ​​the luminescent layer. Simultaneously, the ratio range for the two lateral regions is not limited and can be flexibly set according to the actual exciton distribution, making the process relatively simple to implement.

[0126] In the first embodiment of this application, in the thickness region of the luminescent layer from 0 to 0.4D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase; and / or, in the thickness region of the luminescent layer from 0.6D to D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease.

[0127] Specifically, in the 0–0.4D thickness region of the luminescent layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration shows an increasing trend. This means that the ratio of sensitizer to fluorescent guest material doping concentration increases continuously across multiple sublayers corresponding to the 0–0.4D thickness region. Alternatively, the doping concentration ratio increases in some sublayers corresponding to the 0–0.4D thickness region and remains constant in others. For example, the doping concentration ratio increases continuously in multiple sublayers corresponding to the 0–0.1D thickness region, remains constant in multiple sublayers corresponding to the 0.1D–0.2D thickness region, and then increases continuously in multiple sublayers corresponding to the 0.2D–0.4D thickness region.

[0128] Specifically, in the 0.6D~D thickness region of the luminescent layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration shows a decreasing trend. This means that the ratio of sensitizer to fluorescent guest material doping concentration decreases continuously across multiple sublayers corresponding to the 0.6D~D thickness region. Alternatively, the doping concentration ratio decreases in some sublayers corresponding to the 0.6D~D thickness region and remains constant in others. For example, the doping concentration ratio decreases continuously across multiple sublayers corresponding to the 0.6D~0.8D thickness region, remains constant in multiple sublayers corresponding to the 0.8D~0.9D thickness region, and then decreases continuously again across multiple sublayers corresponding to the 0.9D~D thickness region.

[0129] In the first embodiment of this application, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in both the 0~0.4D and 0.6D~D thickness regions of the luminescent layer. Alternatively, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in either of the thickness regions.

[0130] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to increase. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to decrease. For details, please refer to... Figure 8 , Figure 8 This is a schematic diagram showing the changing trend of the doping concentration ratio of the sensitizer to the fluorescent guest material in the first embodiment of the first implementation of this application.

[0131] Understandably, in this embodiment, the variation trend of the doping concentration ratio in both sides of the luminescent layer is limited. The doping concentration ratio of the sensitizer increases from the two side interfaces towards the center, while the doping concentration ratio of the fluorescent guest material decreases from the two side interfaces towards the center. This results in a relatively high doping concentration of the fluorescent guest material at the two side interfaces, enabling efficient utilization of the high-concentration excitons near the two side interfaces for luminescence, which is beneficial for forming a highly efficient luminescent region in both side regions. The range and variation trend of the doping concentration ratio in the central region are not limited, thus preserving process flexibility.

[0132] In other embodiments, in the 0-0.4D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10-100, and the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material shows an increasing trend.

[0133] Understandably, in this embodiment, only the trend of the doping concentration ratio in the region of the light-emitting layer near the first electrode is limited. The proportion of sensitizer doping concentration increases from the side near the first electrode towards the center, while the proportion of fluorescent guest material doping concentration decreases accordingly. The fluorescence concentration is higher near the interface of the first electrode, which can efficiently utilize the exciton energy near this interface to emit a narrow-band spectrum, which is beneficial for forming a high-efficiency light-emitting region on the first electrode side. The proportion of sensitizer doping concentration increases towards the center, providing stronger exciton trapping capability for the central region. At the same time, the range and trend of the doping concentration ratio between the central region and the region near the second electrode are not limited, which can retain process flexibility.

[0134] In some other embodiments, in the 0.6D~D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100, and the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material shows a decreasing trend.

[0135] Understandably, in this embodiment, only the variation trend of the doping concentration ratio in the region of the light-emitting layer near the second electrode is limited. The proportion of sensitizer doping concentration decreases from the middle towards the side near the second electrode, while the proportion of fluorescent guest material doping concentration increases accordingly. The fluorescence concentration is higher near the interface of the second electrode, which can efficiently utilize the exciton energy near this interface to emit a narrow-band spectrum, which is beneficial for forming a high-efficiency light-emitting region on the side of the second electrode. At the same time, the range and variation trend of the doping concentration ratio in the middle region and the region near the first electrode are not limited, which can retain process flexibility.

[0136] Furthermore, in the first embodiment of this application, in the 0.4D~0.5D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to decrease. And / or, in the 0.5D~0.6D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to increase.

[0137] Specifically, in the 0.4D~0.5D thickness region of the luminescent layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration shows a decreasing trend. This means that the ratio of sensitizer to fluorescent guest material doping concentration decreases continuously across multiple sublayers corresponding to the 0.4D~0.5D thickness region. Alternatively, the doping concentration ratio decreases in some sublayers corresponding to the 0.4D~0.5D thickness region and remains constant in others. For example, the doping concentration ratio decreases continuously across multiple sublayers corresponding to the 0.4D~0.45D thickness region, remains constant in multiple sublayers corresponding to the 0.45D~0.47D thickness region, and then decreases continuously across multiple sublayers corresponding to the 0.47D~0.5D thickness region.

[0138] Specifically, in the 0.5D~0.6D thickness region of the luminescent layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration shows an increasing trend. This means that the ratio of sensitizer to fluorescent guest material doping concentration increases continuously across multiple sublayers corresponding to the 0.5D~0.6D thickness region. Alternatively, the doping concentration ratio increases in some sublayers corresponding to the 0.5D~0.6D thickness region and remains constant in others. For example, the doping concentration ratio increases continuously across multiple sublayers corresponding to the 0.5D~0.53D thickness region, remains constant in multiple sublayers corresponding to the 0.53D~0.56D thickness region, and then increases continuously again in multiple sublayers corresponding to the 0.56D~0.6D thickness region.

[0139] In the first embodiment of this application, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in thickness regions of 0.4D~0.5D and 0.5D~0.6D of the luminescent layer. Alternatively, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in thickness regions corresponding to either of these thicknesses.

[0140] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to increase. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 80-100, and this ratio tends to decrease. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 80-100, and this ratio tends to increase. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to decrease. For details, please refer to [link to relevant documentation]. Figure 9 , Figure 9 This is a schematic diagram showing the changing trend of the doping concentration ratio of the sensitizer to the fluorescent guest material in the second embodiment of the first embodiment of this application.

[0141] Understandably, in this embodiment, the variation trend of the doping concentration ratios in the four intervals across the overall thickness of the luminescent layer is defined. The doping concentration of the sensitizer increases from the two side interfaces towards the center, maintaining a high doping concentration in the central region. It first decreases in the 0.4D~0.5D range, then increases again in the 0.5D~0.6D range, maintaining a high proportion in the central region, and forming a relative trough in sensitizer concentration near 0.5D, resulting in a bimodal or plateau structure. The concentration of the fluorescent guest material increases relatively near 0.5D, which is beneficial for improving the luminescence efficiency in the central region. Furthermore, this distribution results in a relatively high doping concentration of the fluorescent guest material in the two side interface regions, enabling efficient utilization of the high-concentration exciton energy near the interface to emit narrow-band spectra, which is beneficial for forming highly efficient luminescent regions on both sides of the luminescent layer. Meanwhile, the doping concentration ratios of the two side regions, ranging from 10 to 100, overlap with the doping concentration ratio of the central region, which ranges from 80 to 100. This overlap in the 80-100 range allows for a smooth transition between the doping concentration ratios of the central and side regions, mitigating energy transfer interruptions or exciton accumulation caused by abrupt changes in ratios. Furthermore, the higher concentration of sensitizer forming an energy buffer in the central and side interface regions effectively shortens the residence time of high-energy excitons on the host material, reducing the risk of material degradation. This balances improved blue light emission efficiency with device lifespan.

[0142] In other embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to increase. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 80-100, with no specific trend specified. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 80-100, and this ratio tends to increase. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to decrease.

[0143] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100, and this ratio tends to increase. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 80-100, and this ratio tends to decrease. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 80-100, without a specific trend. In the 0.6D-D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100, and this ratio tends to decrease.

[0144] Furthermore, in the first embodiment, in the thickness region of the luminescent layer from 0 to 0.4D, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase. And / or, in the thickness region of the luminescent layer from 0.6D to 0.D, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease.

[0145] Specifically, in the 0–0.4D thickness region of the emitting layer, the doping concentration of the fluorescent guest material shows a decreasing trend. This means that the doping concentration of the fluorescent guest material continuously decreases across multiple sublayers corresponding to the 0–0.4D thickness region. Alternatively, the doping concentration of the fluorescent guest material decreases in some sublayers corresponding to the 0–0.4D thickness region and remains constant in others. For example, the doping concentration of the fluorescent guest material continuously decreases in multiple sublayers corresponding to the 0–0.1D thickness region, remains constant in multiple sublayers corresponding to the 0.1D–0.2D thickness region, and then continuously decreases again in multiple sublayers corresponding to the 0.2D–0.4D thickness region.

[0146] Specifically, in the 0–0.4D thickness region of the light-emitting layer, the sensitizer doping concentration shows an increasing trend, meaning that the sensitizer doping concentration continuously increases across multiple sublayers corresponding to the 0–0.4D thickness region. Alternatively, the sensitizer doping concentration increases in some sublayers corresponding to the 0–0.4D thickness region and remains constant in others. For example, the sensitizer doping concentration continuously increases in multiple sublayers corresponding to the 0–0.1D thickness region, remains constant in multiple sublayers corresponding to the 0.1D–0.2D thickness region, and then continuously increases again in multiple sublayers corresponding to the 0.2D–0.4D thickness region.

[0147] Specifically, in the 0.6D~D thickness region of the emitting layer, the doping concentration of the fluorescent guest material shows an increasing trend, meaning that the doping concentration of the fluorescent guest material continuously increases in multiple sublayers corresponding to the 0.6D~D thickness region. Alternatively, the doping concentration of the fluorescent guest material increases in some sublayers corresponding to the 0~0.4D thickness region, and remains constant in some other sublayers.

[0148] Specifically, in the 0.6D~D thickness region of the light-emitting layer, the sensitizer doping concentration shows a decreasing trend, meaning that the sensitizer doping concentration continuously decreases across multiple sublayers corresponding to the 0.6D~D thickness region. Alternatively, the sensitizer doping concentration decreases in some sublayers corresponding to the 0~0.4D thickness region, and remains constant in some other sublayers.

[0149] In the first embodiment of this application, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in both the 0~0.4D and 0.6D~D thickness regions of the luminescent layer. Alternatively, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in either of the thickness regions.

[0150] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration showing a decreasing trend and the sensitizer doping concentration showing an increasing trend. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration showing an increasing trend and the sensitizer doping concentration showing a decreasing trend.

[0151] Understandably, in this embodiment, the doping concentration variation trends on both sides of the luminescent layer are defined. The fluorescent guest material has the highest doping concentration at the interfaces on both sides, decreasing towards the center; the sensitizer concentration increases from the interfaces on both sides towards the center, forming a concentration peak near the central region. This distribution allows the fluorescent guest material at the interfaces on both sides to efficiently utilize the high concentration of excitons near the interfaces for luminescence, which is beneficial for forming highly efficient luminescent regions on both sides. The sensitizer concentration is higher near the central region, which can fully capture the excitons generated in the central region and form an energy buffer. The doping concentration ratio range and variation trend in the central region are not limited, thus preserving process flexibility.

[0152] Furthermore, in the first embodiment, in the 0.4D~0.5D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease. And / or, in the 0.5D~0.6D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase.

[0153] The specific definitions of the increasing and decreasing trends of doping concentration are as described above and will not be repeated here.

[0154] In the first embodiment of this application, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in thickness regions of 0.4D~0.5D and 0.5D~0.6D of the luminescent layer. Alternatively, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in thickness regions corresponding to either of these thicknesses.

[0155] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration decreasing and the sensitizer doping concentration increasing. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 80-100, with the fluorescent guest material doping concentration increasing and the sensitizer doping concentration decreasing. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 80-100, with the fluorescent guest material doping concentration decreasing and the sensitizer doping concentration increasing. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration increasing and the sensitizer doping concentration decreasing. For details, please refer to [link to specific examples]. Figure 10 , Figure 10 This is a schematic diagram showing the trend of doping concentration changes of the sensitizer and the fluorescent guest material in the third embodiment of the first embodiment of this application.

[0156] In this specific embodiment, the overall trend of the doping concentration of the fluorescent guest material in the luminescent layer exhibits a W-shape, meaning that the doping concentration of the fluorescent guest material is higher at the two side interfaces, with a fluorescence concentration trough on each side of the center and a fluorescence concentration peak at the center. Correspondingly, the overall trend of the doping concentration of the sensitizer exhibits an M-shape, with the lowest doping concentration at the two side interfaces, a doping concentration trough at the center, and a doping concentration peak on each side of the center.

[0157] Understandably, in this embodiment, the doping concentration variation trends of the four intervals within the overall thickness region of the luminescent layer are all defined, and these four doping concentration variation intervals can divide the luminescent layer into functionally distinct regions. Specifically, the interface regions on both sides are primarily responsible for efficient luminescence, while the central region is mainly responsible for energy capture and supply. This functional zoning mechanism is beneficial for improving exciton energy utilization and blue light emission efficiency. Specifically, the high-concentration distribution region of the fluorescent guest material is located in the interface regions on both sides where exciton generation is most concentrated. This means that a large number of excitons generated at the EBL / EML and EML / HBL interfaces can be received by the fluorescent guest material located there, receiving energy and converting it into light with the shortest path and fastest speed. This minimizes exciton transmission loss and quenching probability at the interface, which is particularly effective in improving the luminescence efficiency of the interface region. Simultaneously, the fluorescence concentration peak formed at the central position is beneficial for efficiently receiving energy transferred by the sensitizer in the central region and emitting a narrow-band spectrum. Furthermore, because the fluorescent guest material is more concentrated and precise at both interfaces, it can convert excitons at the interface into light output with extremely high efficiency at the optimal doping concentration. This enables the first light-emitting device 30a to have higher blue light emission efficiency. In addition, the energy buffer formed by the higher concentration of sensitizer in the central region and both interface regions can effectively shorten the residence time of high-energy excitons on the host material and reduce the risk of material degradation, thereby improving blue light emission efficiency while also considering device lifespan.

[0158] In a first embodiment of this application, the sensitizer has a first concentration distribution line in the 0-0.5D thickness region of the emissive layer, and a second concentration distribution line in the same region, with the first and second concentration distribution lines symmetrically distributed. And / or, the fluorescent guest has a third concentration distribution line in the 0-0.5D thickness region of the emissive layer, and a fourth concentration distribution line in the same region, with the third and fourth concentration distribution lines symmetrically distributed.

[0159] The first and second concentration distribution lines are symmetrically distributed, meaning that the trend of the sensitizer doping concentration is at least partially symmetrical along the central position (0.5D). The third and fourth concentration distribution lines are symmetrically distributed, meaning that the trend of the fluorescent guest material doping concentration is at least partially symmetrical along the central position (0.5D).

[0160] For some specific embodiments, please refer to Figures 11a-11b , Figures 11a-11bThis is a schematic diagram of the concentration distribution lines corresponding to the sensitizer and the fluorescent guest material in the fourth embodiment of the first embodiment of this application. In this embodiment, the sensitizer has a first concentration distribution line L1 in the 0~0.4D region of the luminescent layer and a second concentration distribution line L2 in the 0.6D~D region of the luminescent layer, and the first concentration distribution line L1 and the second concentration distribution line L2 are symmetrically distributed. The fluorescent guest material has a third concentration distribution line L3 in the 0~0.4D region of the luminescent layer and a fourth concentration distribution line L4 in the 0.6D~D region of the luminescent layer, and the third concentration distribution line L3 and the fourth concentration distribution line L4 are symmetrically distributed.

[0161] In the second embodiment of this application, in the thickness region of the luminescent layer from 0 to 0.4D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease; and / or, in the thickness region of the luminescent layer from 0.6D to D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase.

[0162] The specific definitions of decreasing and increasing trends are provided above and will not be repeated here.

[0163] In the second embodiment of this application, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in both the 0~0.4D and 0.6D~D thickness regions of the luminescent layer. Alternatively, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in either of the thickness regions.

[0164] In some embodiments, in the 0–0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10–100, and this ratio tends to decrease. In the 0.6D–D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10–100, and this ratio tends to increase. For details, please refer to… Figure 12 , Figure 12 This is a schematic diagram showing the changing trend of the doping concentration ratio of the sensitizer to the fluorescent guest material in the first embodiment of the second embodiment of this application.

[0165] Understandably, in this embodiment, the variation trend of the doping concentration ratio on both sides of the luminescent layer is limited. The doping concentration ratio of the sensitizer decreases from the two side interfaces towards the center, while the doping concentration ratio of the fluorescent guest material increases from the two side interfaces towards the center. This results in a relatively high doping concentration of the fluorescent guest material in the central region, enabling it to efficiently receive energy transferred by the sensitizer and emit a narrow-band spectrum in an environment with low exciton and sensitizer concentrations in the central region. This reduces the quenching loss that may be caused by high-concentration sensitizers, thereby improving the blue light emission efficiency in the central region. The higher sensitizer concentration at the two side interfaces can fully capture excitons near the interface and form a buffer protective layer, smoothly transferring energy to the fluorescent guest material in the central region for luminescence, thereby further extending the device lifetime while improving luminescence efficiency. The doping concentration ratio range in the central region is not limited and can be flexibly set according to the actual exciton distribution.

[0166] In other embodiments, in the 0-0.4D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100, and the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration shows a decreasing trend.

[0167] Understandably, in this embodiment, only the trend of the doping concentration ratio in the region of the light-emitting layer near the first electrode is limited. The proportion of sensitizer doping decreases from near the first electrode towards the center, while the proportion of fluorescent guest material increases accordingly. The fluorescence concentration gradually increases towards the center, which is beneficial for efficiently receiving energy and emitting a narrow-band spectrum in the central region, thereby improving the green light emission efficiency in the central region. The higher doping concentration of the sensitizer at the interface near the first electrode can effectively capture excitons near this interface and form a buffer protection.

[0168] In some other embodiments, in the 0.6D~D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100, and the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material shows an increasing trend.

[0169] Understandably, in this embodiment, only the variation trend of the doping concentration ratio in the region of the luminescent layer near the second electrode is limited. The sensitizer doping concentration increases from the center towards the second electrode, reaching a higher concentration at the interface near the second electrode. This effectively captures the high concentration of excitons near the interface and forms a buffer layer, smoothly transferring energy to the adjacent fluorescent guest material for luminescence. The fluorescent guest material concentration decreases from the center towards the second electrode, reaching a higher concentration in the center. This facilitates efficient energy reception and narrowband spectral emission in the central region.

[0170] Furthermore, in the second embodiment of this application, in the 0.4D~0.5D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to increase. And / or, in the 0.5D~0.6D thickness region of the luminescent layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration tends to decrease.

[0171] The specific definitions of decreasing and increasing trends are provided above and will not be repeated here.

[0172] In the second embodiment of this application, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in thickness regions of 0.4D~0.5D and 0.5D~0.6D of the luminescent layer. Alternatively, the variation trend of the doping concentration ratio of the sensitizer to the fluorescent guest material can be limited in thickness regions corresponding to either of these thicknesses.

[0173] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to decrease. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 0.5-15, and this ratio tends to increase. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 0.5-15, and this ratio tends to decrease. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, and this ratio tends to increase.

[0174] Understandably, in this embodiment, the variation trend of the doping concentration ratios in the four intervals across the overall thickness of the luminescent layer is defined. The doping concentration of the sensitizer decreases from the two side interfaces towards the center, dropping to a lower level in the central region. It first increases in the 0.4D~0.5D interval and then decreases again in the 0.5D~0.6D interval, forming a relative peak in sensitizer concentration near 0.5D, creating a double-trough or plateau structure that acts as an energy transfer and buffer. Correspondingly, the doping concentration of the fluorescent guest material increases from the two side interfaces towards the center, occupying a larger proportion in the central region. Concentration peaks are formed on both sides of the center (near 0.4D and near 0.6D), enabling efficient reception of energy transferred by the sensitizer and emission of a narrow-band spectrum in the low exciton and low sensitizer concentration environment of the central region. This reduces the quenching loss that may be caused by high-concentration sensitizers, thereby improving the blue light emission efficiency in the central region. The doping concentration ratios of the two side regions range from 10 to 100, while those of the central region range from 0.5 to 15. There is some overlap in the 10-15 range, allowing for a smooth transition between the doping concentration ratios of each region. Simultaneously, the higher sensitizer concentrations at the side interfaces effectively capture excitons near the interface and form a buffer protective layer, thereby further extending the device lifetime while improving blue light emission efficiency.

[0175] In other embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100, and this ratio tends to decrease. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5-15, with no specific trend specified. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5-15, and this ratio tends to decrease. In the 0.6D-D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100, and this ratio tends to increase.

[0176] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100, and this ratio tends to decrease. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5-15, and this ratio tends to increase. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 0.5-15, without a specific trend. In the 0.6D-D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10-100, and this ratio tends to increase.

[0177] Furthermore, in the second embodiment, in the thickness region of the luminescent layer from 0 to 0.4D, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease. And / or, in the thickness region of the luminescent layer from 0.6D to D, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase.

[0178] The specific definitions of increasing and decreasing trends are provided above and will not be repeated here.

[0179] In the second embodiment of this application, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in the thickness regions of 0~0.4D and 0.6D~D of the light-emitting layer. Alternatively, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in the thickness region corresponding to either of these thicknesses.

[0180] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration showing an increasing trend and the sensitizer doping concentration showing a decreasing trend. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration showing a decreasing trend and the sensitizer doping concentration showing an increasing trend.

[0181] Understandably, in this embodiment, the doping concentration variation trends on both sides of the luminescent layer are defined. The doping concentration of the fluorescent guest material increases from the two side interfaces towards the center, reaching a higher concentration near the center; the doping concentration of the sensitizer decreases from the two side interfaces towards the center, reaching a lower concentration near the center. This distribution allows the fluorescent guest material to concentrate in the central region, enabling it to efficiently receive transferred exciton energy and emit a narrow-band spectrum in an environment with low exciton and sensitizer concentrations, thus improving the luminescence efficiency in the central region. The higher sensitizer concentration at the two side interfaces effectively captures excitons near the interface and forms a buffer protective layer, smoothly transferring energy to the fluorescent guest material in the central region for luminescence, thereby further extending the device lifetime while improving blue light luminescence efficiency.

[0182] Furthermore, in the second embodiment, in the 0.4D~0.5D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase. And / or, in the 0.5D~0.6D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease.

[0183] The specific definitions of increasing and decreasing trends are provided above and will not be repeated here.

[0184] In the second embodiment of this application, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in thickness regions of 0.4D~0.5D and 0.5D~0.6D of the luminescent layer. Alternatively, the variation trend of doping concentration of the sensitizer and the fluorescent guest material can be limited in thickness regions corresponding to either of these thicknesses.

[0185] In some embodiments, in the 0-0.4D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration increasing and the sensitizer doping concentration decreasing. In the 0.4D-0.5D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 0.5-15, with the fluorescent guest material doping concentration decreasing and the sensitizer doping concentration increasing. In the 0.5D-0.6D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 0.5-15, with the fluorescent guest material doping concentration increasing and the sensitizer doping concentration decreasing. In the 0.6D-D thickness region of the emissive layer, the ratio of sensitizer doping concentration to fluorescent guest material doping concentration is 10-100, with the fluorescent guest material doping concentration decreasing and the sensitizer doping concentration increasing. For details, please refer to [link to relevant documentation]. Figure 13 , Figure 13This is a schematic diagram showing the trend of doping concentration changes of the sensitizer and the fluorescent guest material in the second embodiment of the first embodiment of this application.

[0186] In this specific embodiment, the overall trend of the doping concentration of the fluorescent guest material in the luminescent layer exhibits an M-shape, meaning that the doping concentration of the fluorescent guest material is lower at the two side interfaces, forming a fluorescence concentration trough at the center, and a fluorescence concentration peak on each side of the center. Correspondingly, the overall trend of the doping concentration of the sensitizer exhibits a W-shape, with a higher doping concentration at the two side interfaces, forming a doping concentration trough on each side of the center, and a doping concentration peak at the center.

[0187] Understandably, in this embodiment, the doping concentration variation trends of the four intervals within the overall thickness region of the luminescent layer are all defined, and these four doping concentration variation intervals can divide the luminescent layer into functionally distinct regions. Specifically, the interface regions on both sides are high-concentration exciton trapping and buffering layers, while the inward-facing regions are energy transfer layers with gradually increasing fluorescence concentration. This functional zoning mechanism is beneficial for finely controlling interface buffering and improving the luminescence performance of the central region. Specifically, although the fluorescent guest material is concentrated in the central region, the central position itself is a concentration trough. This means that the fluorescent guest material is distributed in two peak regions on either side of the central position, rather than being directly piled up in the central position. This distribution method has two advantages: first, it avoids the aggregation quenching that may be caused by excessive concentration of fluorescent guest material in a single location; second, the two fluorescence concentration peaks are sandwiched between a fluorescence concentration trough with a higher sensitizer concentration. This fluorescence concentration trough can buffer and redistribute the exciton energy transferred from the sensitizers on both sides, ensuring that both fluorescence concentration peaks receive a balanced energy supply, thereby balancing the luminescence performance of the central region. Furthermore, since the concentration of sensitizer is highest at both interfaces, the sensitizer forms the densest protective barrier in the interface region where the exciton concentration is highest and the environment is most severe. This can isolate the fluorescent guest material from the harsh interface environment to the greatest extent, thereby significantly reducing the probability of degradation of the fluorescent guest material. Consequently, on the basis of improving the blue light emission efficiency, the lifespan of the first light-emitting device 30c (blue light-emitting device) is further extended.

[0188] In the second embodiment of this application, the sensitizer has a first concentration distribution line in the 0~0.5D thickness region of the emissive layer, and a second concentration distribution line in the 0.5D~D thickness region of the emissive layer, the first and second concentration distribution lines being symmetrically distributed. And / or, the fluorescent guest has a third concentration distribution line in the 0~0.5D thickness region of the emissive layer, and a fourth concentration distribution line in the 0.5D~D thickness region of the emissive layer, the third and fourth concentration distribution lines being symmetrically distributed.

[0189] The first and second concentration distribution lines are symmetrically distributed, meaning that the trend of the sensitizer doping concentration is at least partially symmetrical along the central position (0.5D). The third and fourth concentration distribution lines are symmetrically distributed, meaning that the trend of the fluorescent guest material doping concentration is at least partially symmetrical along the central position (0.5D).

[0190] Specifically, such as Figures 14a-14b As shown, the first concentration distribution line L1 and the second concentration distribution line L2 are symmetrically distributed. The third concentration distribution line L3 and the fourth concentration distribution line L4 are also symmetrically distributed.

[0191] In the third embodiment of this application, the thickness of the light-emitting layer is defined as D, the thickness of the surface of the light-emitting layer near the first electrode is defined as 0, and the thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0~0.4D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase; and / or, in the thickness region of 0.6D~D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease.

[0192] Furthermore, in the third embodiment, in the thickness region of the luminescent layer from 0 to 0.4D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100; and / or, in the thickness region of the luminescent layer from 0.4D to 0.6D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 80 to 100; and / or, in the thickness region of the luminescent layer from 0.6D to D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100.

[0193] Furthermore, in the third embodiment, the sensitizer has a first concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the sensitizer has a second concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the first and second concentration distribution lines symmetrically distributed; and / or, the fluorescent guest has a third concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the fluorescent guest has a fourth concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the third and fourth concentration distribution lines symmetrically distributed.

[0194] Understandably, for various specific embodiments of the third implementation method and their corresponding technical effects, please refer to various specific embodiments of the first implementation method and their corresponding technical effects.

[0195] In the fourth embodiment of this application, the thickness of the light-emitting layer is defined as D, the thickness of the surface of the light-emitting layer near the first electrode is defined as 0, and the thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0~0.4D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease; and / or, in the thickness region of 0.6D~D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase.

[0196] Furthermore, in the fourth embodiment, in the thickness region of the luminescent layer from 0 to 0.4D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100; and / or, in the thickness region of the luminescent layer from 0.4D to 0.6D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 0.5 to 15; and / or, in the thickness region of the luminescent layer from 0.6D to D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100.

[0197] Furthermore, in the fourth embodiment, the sensitizer has a first concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the sensitizer has a second concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the first and second concentration distribution lines symmetrically distributed; and / or, the fluorescent guest has a third concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the fluorescent guest has a fourth concentration distribution line in the 0.5D~D thickness region of the luminescent layer, with the third and fourth concentration distribution lines symmetrically distributed.

[0198] Understandably, for various specific embodiments of the fourth implementation method and their corresponding technical effects, please refer to various specific embodiments of the second implementation method and their corresponding technical effects.

[0199] In this application, the first light-emitting device 30a can be a single-layer light-emitting device or a multilayer light-emitting device. In the multilayer light-emitting device, the light-emitting functional layer includes at least two light-emitting units, and the ratio of sensitizer to fluorescent material in at least one light-emitting layer of each light-emitting unit exhibits the distribution trend described in the aforementioned embodiments.

[0200] In some embodiments, the total doping concentration of the sensitizer in the light-emitting layer of the first light-emitting device 30a is 2% to 20%, and the total doping concentration of the fluorescent guest material is 0.2% to 4%.

[0201] In some embodiments, the total doping concentration of the sensitizer in the light-emitting layer of the first light-emitting device 30a is 2, 3, 4, 6, 8, 10, 12, 14, 15, 16, 18 or 20%, and the total doping concentration of the fluorescent guest material is 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4%.

[0202] Specifically, the total doping concentration of the same doped material in the emissive layer can be obtained by weighted averaging or integrating the concentration data of all sublayers corresponding to the same doped material. The total doping concentration of the sensitizer is 2%–20%, meaning that after weighted averaging the mass percentage of the sensitizer in all sublayers of the emissive layer, the total mass percentage of the sensitizer in the entire emissive layer falls within the range of 2% to 20%. The total doping concentration of the fluorescent guest material is 0.2%–4%, meaning that after weighted averaging the mass percentage of the fluorescent guest material in all sublayers of the emissive layer, the total mass percentage of the fluorescent guest material in the entire emissive layer falls within the range of 0.2% to 4%.

[0203] Understandably, by setting the total doping concentration of the sensitizer to 2%–20%, a highly efficient sensitized energy transfer system can be constructed in blue light-emitting devices. Specifically, setting the sensitizer doping concentration in a relatively high range is because blue light-emitting materials have a wide bandgap and high photon energy, making them more prone to degradation reactions such as chemical bond breaking in the excited state. A higher concentration of sensitizer can form a dense energy transfer network in the emitting layer, quickly capturing high-energy excitons generated by the host material, shortening the exciton residence time on the host material, and reducing the risk of material degradation. At the same time, a high concentration of sensitizer can form an effective buffer protective layer around the fluorescent guest material, preferentially withstanding high-energy exciton impacts and smoothly transferring energy to the fluorescent guest material, thereby ensuring device lifespan while achieving near 100% exciton utilization. Meanwhile, by controlling the total doping concentration of the fluorescent guest material in a lower range of 0.2%–4%, it is possible to ensure that the fluorescent guest material fully receives the energy transferred by the sensitizer while improving concentration quenching and aggregation degradation caused by excessive doping concentration, thus balancing luminous efficiency and device lifespan.

[0204] In some embodiments, the total doping concentration of the sensitizer is 3% to 15%, and the total doping concentration of the fluorescent guest material is 0.2% to 2%.

[0205] In some specific embodiments, the total doping concentration of the sensitizer is 8% to 12%, and the total doping concentration of the fluorescent guest material is 0.5% to 1%.

[0206] In some embodiments, the total doping concentration of the sensitizer is 8%, and the total doping concentration of the fluorescent guest material is 0.5%. In other embodiments, the total doping concentration of the sensitizer is 8%, and the total doping concentration of the fluorescent guest material is 1.0%. In still other embodiments, the total doping concentration of the sensitizer is 12%, and the total doping concentration of the fluorescent guest material is 0.7%. In still other embodiments, the total doping concentration of the sensitizer is 15%, and the total doping concentration of the fluorescent guest material is 0.5%. In yet other embodiments, the total doping concentration of the sensitizer is 15%, and the total doping concentration of the fluorescent guest material is 1.0%.

[0207] Understandably, by further limiting the total doping concentration of the sensitizer to 8%~12% and the total doping concentration of the fluorescent guest material to 0.5%~1%, a dense and efficient energy transfer network can be constructed in the blue light emitting layer. This allows high-energy excitons to be rapidly captured by the sensitizer and smoothly transferred to the fluorescent guest material, shortening the residence time of excitons on the host material to reduce the risk of material degradation. At the same time, it avoids aggregation quenching caused by excessive concentration of the fluorescent guest material, thus ensuring both high color purity and high luminous efficiency while guaranteeing device lifespan.

[0208] In this application, the sensitizer includes phosphorescent materials or TADF (Thermally Activated Delayed Fluorescence) type materials.

[0209] In some embodiments, the sensitizer includes a phosphorescent material, and the sensitizer includes platinum (Pt).

[0210] Introducing heavy metal atoms Pt into phosphorescent materials can enhance the spin-orbit coupling effect, thereby achieving 100% exciton utilization.

[0211] Specifically, under the influence of an electric field, electrons and holes are injected from the cathode and anode of the second light-emitting device 30b, respectively, and recombine to form excitons in the light-emitting layer. The host material collects and concentrates energy, transferring all the energy of its generated singlet and triplet excitons to the phosphorescent photosensitizer. The phosphorescent material enhances the spin-orbit coupling effect through its platinum content, fully capturing excitons and concentrating all received energy into its triplet state. Subsequently, the phosphorescent material efficiently transfers the energy concentrated in the triplet state to the singlet state of the fluorescent guest material. After the molecules of the fluorescent guest material transition to the excited singlet state, they return to the ground state through radiative transition, emitting blue photons.

[0212] In some embodiments, the sensitizer includes a phosphorescent material, wherein the triplet (T1) exciton level of the phosphorescent material is greater than or equal to the singlet (S1) exciton level of the fluorescent guest material. The energy level difference (ΔEST) between the singlet exciton level of the fluorescent guest material and the triplet exciton level of the fluorescent guest material is less than or equal to 0.2 eV, for example, 0.1, 0.15, or 0.2 eV.

[0213] Understandably, in this embodiment, by ensuring that the triplet exciton energy level of the sensitizer is greater than or equal to the singlet exciton energy level of the fluorescent guest material, it is possible to ensure that the triplet exciton energy of the sensitizer is thermodynamically sufficient to drive the fluorescent guest material to a singlet excited state. This achieves efficient Förster resonance energy transfer from the sensitizer to the fluorescent guest material, avoiding energy backflow or transfer interruption due to energy level mismatch, thereby ensuring the efficiency and directionality of energy transfer. Simultaneously, by ensuring that the energy level difference between the singlet and triplet exciton energy levels of the fluorescent guest material is less than or equal to 0.2 eV, the fluorescent guest material itself can possess TADF properties. Because the energy level difference between the singlet and triplet states of fluorescent guest materials is extremely small, if some exciton energy is transferred through Dexter or other means to form triplet excitons in the fluorescent guest material, these triplet excitons can be efficiently converted into singlet excitons and emit narrowband spectra through the reverse intersystem crossing (RISC) process with the assistance of ambient thermal energy, thereby reducing energy loss and further improving the blue light emission efficiency of the display panel 100.

[0214] In some specific embodiments, the sensitizer is either bis(2,4-difluorophenylpyridine)tetra(1-pyrazolyl)boronic iridium(III) (i.e., Fir6, with an emission peak of approximately 460 nm) or a tetradentate platinum complex (i.e., PtON-TBBI, with an emission peak of approximately 465 nm). The T1 energy level of the above sensitizers is greater than or equal to 2.7 eV, which can effectively match the S1 energy level of most blue narrowband fluorescent guest materials.

[0215] In some specific embodiments, the fluorescent guest material is any one of the following: ultranarrow half-width boron-nitrogen-based multiple resonance blue thermally activated delayed fluorescence material (i.e., ν-DABNA), meta-substituted boron-nitrogen-based multiple resonance blue thermally activated delayed fluorescence material (i.e., m-DABNA), and diboron-nitrogen-doped multiple resonance blue thermally activated delayed fluorescence material (i.e., DABNA-2).

[0216] The emission peak of ν-DABNA is approximately 468 nm, the FWMH is approximately 14 nm, the S1 level is approximately 2.65 eV, and the ΔEST with the T1 level is less than 0.10 eV. The emission peak of m-DABNA is approximately 462 nm, the FWMH is approximately 16 m, the S1 level is approximately 2.68 eV, and the ΔEST with the T1 level is less than 0.12 eV. The emission peak of DABNA-2 is approximately 470 nm, the FWMH is approximately 20 nm, the S1 level is approximately 2.64 eV, and the ΔEST with the T1 level is less than 0.15 eV.

[0217] The above-mentioned sensitizers and fluorescent guest materials can be combined in any two pairs to form pTSF (phosphor-assisted thermally activated delayed fluorescence sensitized fluorescence) combinations, all of which meet the energy level matching conditions. When used in the emitting layer, they can effectively improve the blue light emission efficiency of the first light-emitting device 30a (blue light emitting device).

[0218] In some embodiments, the fluorescent guest material of the first light-emitting device 30a contains deuteration.

[0219] In this context, deuteration refers to replacing some or all of the hydrogen atoms in a fluorescent guest material molecule with deuterium atoms. Because the zero-point vibrational energy of the carbon-deuterium bond is lower than that of the carbon-hydrogen bond, its bond energy is higher and the chemical bond is more stable.

[0220] Understandably, in blue light-emitting devices, photon energies are high, and under prolonged operation, the excited-state energy of fluorescent guest material molecules can easily lead to the breakage of carbon-hydrogen bonds, causing material degradation. By replacing the fragile carbon-hydrogen bonds with more stable carbon-deuterium bonds through deuteration, bond dissociation reactions in the excited state can be effectively suppressed, reducing the material degradation rate and thus significantly extending the lifespan of blue light-emitting devices.

[0221] In other embodiments, the fluorescent guest material of the first light-emitting device 30a contains tert-butyl.

[0222] Tert-butyl is a sterically hindered group. Introducing tert-butyl into fluorescent guest material molecules can increase the intermolecular distance, inhibit π-π stacking and aggregation between molecules, reduce concentration quenching and excitopolymer formation caused by aggregation, thereby improving luminescence efficiency. Simultaneously, the introduction of tert-butyl can also improve the solubility and film-forming properties of the material, which is beneficial to the uniformity and morphological stability of the luminescent layer film, further enhancing the performance and lifespan of blue light-emitting devices.

[0223] In other embodiments, the fluorescent guest material of the first light-emitting device 30a contains deuterated and tert-butyl groups.

[0224] Understandably, when fluorescent guest materials are simultaneously modified with deuterated and tert-butyl groups, the thermal and photochemical stability of the materials can be improved at the molecular level, and the degradation reaction and molecular aggregation initiated by high-energy excitons can be suppressed. Thus, while maintaining high color purity and high luminous efficiency, the lifespan of blue light-emitting devices can be effectively extended.

[0225] In this application, the main material of the first light-emitting device 30a includes at least one material.

[0226] In some embodiments, the glass transition temperature (Tg) of the host material is greater than 110 degrees, specifically 120, 125, 128 or 130 degrees.

[0227] Understandably, a glass transition temperature (Tg) greater than 110°C indicates high thermal stability of the host material. In OLED device fabrication and subsequent encapsulation and dicing processes, multiple thermal shocks are frequently encountered. If the Tg of the host material is low (e.g., below 110°C), its film morphology may transition from a glassy state to a rubbery state, leading to intensified molecular chain segment movement, deterioration of the film surface morphology, and consequently affecting the stability and lifespan of the entire device. Using a host material with a high Tg effectively suppresses film deformation and molecular aggregation under high-temperature conditions, ensuring that the light-emitting layer film maintains a good amorphous morphology and that dopants are uniformly dispersed within the host. This helps stabilize the electrical and optical performance of the device, preventing exciton quenching and efficiency degradation caused by material crystallization or phase separation, thereby improving the process robustness, lifespan, and luminous stability of the third light-emitting device 30c.

[0228] In some embodiments, the main material of the first light-emitting device 30a contains silicon.

[0229] In this process, silicon is introduced into the host material molecules, typically in the form of tetracoordinate silicon (such as triphenylsilyl). This large-volume tetrahedral structure effectively increases the intermolecular distance, suppresses π-π stacking and aggregation between molecules, raises the glass transition temperature of the host material, and enhances the thermal and morphological stability of the thin film. Simultaneously, the introduction of silicon can also modulate the HOMO and LUMO energy levels of the host material, optimize carrier transport performance, and widen the exciton recombination region, reducing exciton accumulation in localized areas. This, in turn, lowers the exciton quenching probability and improves the luminous efficiency and lifetime of blue light-emitting devices.

[0230] In other embodiments, the body material of the first light-emitting device 30a contains deuterated material.

[0231] Deuteration refers to replacing some or all of the hydrogen atoms in the host material molecules with deuterium atoms. Because the zero-point vibrational energy of the carbon-deuterium bond is lower than that of the carbon-hydrogen bond, its bond energy is higher and the chemical bond is more stable. In blue light-emitting devices, photon energies are high, and under prolonged operation, the excited-state energy of the host material molecules easily leads to the breakage of carbon-hydrogen bonds, causing material degradation. By replacing the fragile carbon-hydrogen bonds with more stable carbon-deuterium bonds through deuteration, bond dissociation reactions in the excited state can be effectively suppressed, reducing the degradation rate of the host material and decreasing defect states and quenching centers caused by host material degradation, thereby significantly extending the lifespan of blue light-emitting devices.

[0232] In some other embodiments, the main material of the first light-emitting device 30a contains silicon and deuterated elements.

[0233] Understandably, when silicon and deuteration are introduced into the host material at the same time, the thermal stability, photochemical stability and thin film morphology stability of the material can be improved at the molecular level, the degradation reaction and molecular aggregation initiated by high-energy excitons can be suppressed, and the exciton recombination region can be widened. Thus, while maintaining high luminous efficiency, the lifespan of blue light-emitting devices can be further extended.

[0234] In some embodiments, the host material includes a first host material and a second host material. The first host material is either a P-type host material or an N-type host material, and the second host material is either a P-type host material or an N-type host material. Specifically, the hole mobility of the first host material is higher than that of the second host material, and the electron mobility of the second host material is higher than that of the first host material.

[0235] The first host material is a hole-biased (P-type) material, and the second host material is an electron-biased (N-type) material. The first host material is mainly responsible for hole transport and injection, while the second host material is mainly responsible for electron transport and injection. This results in a more balanced transport of holes and electrons in the luminescent layer, which helps to widen the exciton recombination region and improve the quenching loss caused by excessive exciton concentration at a certain interface, thereby improving luminous efficiency. Simultaneously, the synergistic effect of the two host materials improves carrier balance in the luminescent layer, reduces leakage current, and further enhances the luminous efficiency and stability of the device.

[0236] In some specific embodiments, P-type and N-type materials can be introduced into the light-emitting layer via co-hosting or premixing hosting. Co-hosting involves placing the P-type and N-type materials in two separate evaporation sources, allowing them to evaporate simultaneously during the evaporation process. The mixing ratio in the film is adjusted by controlling the evaporation rates of each material. Premixing hosting involves pre-mixing the P-type and N-type materials in a specific ratio and placing them in the same evaporation source. Only one evaporation source needs to be controlled during evaporation, significantly simplifying the process.

[0237] In some specific embodiments, the volume ratio of the first main material to the second main material is 2:8 to 8:2, for example 2:8, 2:6; 2:4, 2:2, 4:2, 6:2 or 8:2.

[0238] In some specific embodiments, the first host material and the second host material form an excitocomplex, and the excitocomplex has TADF properties.

[0239] Understandably, by endowing the first and second host materials with thermally activated delayed fluorescence properties, the excitocomplex formed by the two-component host materials in the luminescent layer can possess a very small singlet-triplet energy level difference (ΔEST). Under electrical excitation, triplet excitons generated by the host material can be efficiently converted into singlet excitons through a reverse intersystem crossing process with the assistance of ambient thermal energy, thereby recovering and utilizing the energy of the originally non-luminescent triplet excitons. This recovered singlet exciton energy, along with the energy of the directly generated singlet excitons, is transferred to the sensitizer, theoretically enabling the host material to achieve 100% exciton utilization. This ensures the high efficiency of the energy transfer chain's front end, providing a sufficient energy basis for subsequent energy transfer from the sensitizer to the fluorescent guest material, thereby improving the blue light emission efficiency of the first luminescent device 30a.

[0240] In some specific embodiments, the first host material is a polymer based on carbazole or triphenylamine. For example, the first host material can be any one of 4,4',4''-tris(carbazole-9-yl)triphenylamine (i.e., TCTA), 9,9',9''-triphenyl-9H,9'H,9''H-3,3':6',3''-tribicarbazole (i.e., Tris-PCz), 4,4',4''-tris[phenyl(m-tolyl)amino]triphenylamine (i.e., m-MTDATA), and N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (i.e., NPB).

[0241] In some specific embodiments, the second host material is a polymer based on pyrimidine, triazine, or imidazole. For example, the second host material can be 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (i.e., B3PyMPM), 2,4,6-tris[3-(diphenylphosphoxy)phenyl]-1,3,5-triazine (i.e., PO-T2T), 2,4,6-tris(3-(pyridin-3-yl)phenyl)-1,3,5-triazine (i.e., PPT), or 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (i.e., TPBi).

[0242] In the aforementioned combinations of the first and second host materials, the ΔEST of the excitocomplex formed by TCTA (P-type material) and B3PyMPM (N-type material) is less than 0.1 eV; the ΔEST of the excitocomplex formed by TCTA (P-type material) and PO-T2T (N-type material) is less than 0.1 eV; the ΔEST of the excitocomplex formed by Tris-PCz (P-type material) and PPT (N-type material) is less than 0.1 eV; and the ΔEST of the excitocomplex formed by m-MTDATA (P-type material) and TPBi (N-type material) is less than 0.15 eV. All of these two-component host materials possess TADF properties and can be used as highly efficient host materials for green light excitocomplexes.

[0243] In some embodiments, the electron blocking layer of the first light-emitting device 30a (blue light-emitting device) is made of the same material as the P-type host material in the host material.

[0244] In some embodiments, the HOMO (highest occupied molecular orbital) level of the electron blocking layer material of the first light-emitting device 30a (blue light-emitting device) is located between the HOMO level of the host material and the HOMO level of the hole transport layer material.

[0245] Understandably, by using the same material for the electron blocking layer as the P-type host material in the main body, the HOMO energy barrier between the electron blocking layer and the host material of the emissive layer can be eliminated. This allows holes to be injected from the electron blocking layer into the host material of the emissive layer without needing to cross additional energy level steps, resulting in smoother hole injection and thus reducing the driving voltage of the blue light-emitting device. Simultaneously, since the P-type host material in the electron blocking layer and the emissive layer is the same material, the compatibility at their interface is better, which is beneficial for forming a uniform and flat thin film interface, reducing the interface defect state density, suppressing exciton quenching and charge accumulation at the interface, thereby improving the luminous efficiency and stability of the device. Furthermore, using the same material simplifies the material supply chain and evaporation process, reducing mass production costs.

[0246] In some embodiments, the thickness of the light-emitting layer of the first light-emitting device 30a (blue light-emitting device) ranges from 13 to 30 nm, for example, 13, 15, 18, 20, 22, 25, 30 nm.

[0247] In some embodiments, the emissive layer thickness of the blue light-emitting device is 15 nm. In other embodiments, the emissive layer thickness is 20 nm. In still other embodiments, the emissive layer thickness is 25 nm.

[0248] Understandably, by setting the emissive layer thickness of the blue light-emitting device to 13-30 nm, the emissive layer thickness can be matched with the shorter wavelength of blue light, thus meeting the requirement of a shorter cavity length for microcavity resonance in top-emitting devices. Compared to the typically 30-50 nm emissive layer thickness in green and red light-emitting devices, the emissive layer thickness of blue light-emitting devices is thinner. This is based on the optical principle that a thicker emissive layer results in a longer emitted light spectrum. Since the emission peak wavelength of blue light is relatively short, to achieve resonance enhancement in the blue light band within the microcavity, the effective cavity length of the microcavity needs to be shortened accordingly. Therefore, the overall emissive layer thickness of blue light-emitting devices is relatively thin. This embodiment controls the emissive layer thickness within the range of 13 nm to 30 nm, ensuring that the optical position of the emissive layer in the microcavity matches the standing wave conditions of the blue light wavelength, enhancing the light output at specific wavelengths of blue light, and improving light extraction efficiency. This achieves both improved blue light luminescence efficiency and consideration of the device's electrical performance and stability.

[0249] To facilitate understanding of the embodiments of this application, the following non-limiting embodiments are provided to further illustrate the application in detail.

[0250] Example 1 A blue light-emitting device is fabricated, comprising an anode, a cathode, and a light-emitting functional layer located between the anode and cathode. The light-emitting functional layer comprises a host material, a sensitizer, and a fluorescent guest material. The thickness of the light-emitting layer is defined as D. The thickness of the surface of the light-emitting layer near the first electrode is defined as 0, and the thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0–0.4D of the light-emitting layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10–100; in the thickness region of 0.4D–0.6D of the light-emitting layer, the ratio is 80–100; and in the thickness region of 0.6D–D of the light-emitting layer, the ratio is 10–100.

[0251] Example 2 In this embodiment, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is adjusted to 10 to 80 in the 0 to 0.4D thickness region of the luminescent layer; and the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is adjusted to 10 to 80 in the 0.6D to D thickness region of the luminescent layer. The remaining steps and parameters are the same as in Example 1.

[0252] Example 3 In this embodiment, in the thickness region of the luminescent layer from 0 to 0.4D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is controlled to increase; and in the thickness region of the luminescent layer from 0.6D to D, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is controlled to decrease. The remaining steps and parameters are the same as in Example 1.

[0253] Example 3 In this embodiment, the total doping concentration of the sensitizer is controlled at 10%, and the total doping concentration of the fluorescent guest material is controlled at 1%. The remaining steps and parameters are the same as in Example 1.

[0254] Example 4 In this embodiment, the total doping concentration of the sensitizer is controlled at 12%, and the total doping concentration of the fluorescent guest material is controlled at 0.7%. The remaining steps and parameters are the same as in Example 1.

[0255] Example 5 In this embodiment, the total doping concentration of the sensitizer is controlled at 8%, and the total doping concentration of the fluorescent guest material is controlled at 0.5%. The remaining steps and parameters are the same as in Example 1.

[0256] Example 6 In this embodiment, in the 0~0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to increase; in the 0.4D~0.5D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to decrease; in the 0.5D~0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to increase; and in the 0.6D~D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to decrease. The remaining steps and parameters are the same as in Example 1.

[0257] Example 7 A blue light-emitting device is fabricated, comprising an anode, a cathode, and a light-emitting functional layer located between the anode and the cathode. The light-emitting functional layer comprises a host material, a sensitizer, and a fluorescent guest material. The thickness of the light-emitting layer is defined as D. The thickness of the surface of the light-emitting layer near the first electrode is defined as 0, and the thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0–0.4D of the light-emitting layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10–100; in the thickness region of 0.4D–0.6D of the light-emitting layer, the ratio is 0.5–15; and in the thickness region of 0.6D–D of the light-emitting layer, the ratio is 10–100.

[0258] Example 8 In this embodiment, in the 0~0.4D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to decrease; in the 0.4D~0.5D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to increase; in the 0.5D~0.6D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to decrease; and in the 0.6D~D thickness region of the emissive layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is controlled to increase. The remaining steps and parameters are the same as in Example 7.

[0259] Example 9 A blue light-emitting device is fabricated, comprising an anode, a cathode, and a light-emitting functional layer located between the anode and cathode. The light-emitting functional layer comprises two light-emitting units. Each light-emitting layer includes a host material, a sensitizer, and a fluorescent guest material. The thickness of the light-emitting layer is defined as D. The thickness of the surface of the light-emitting layer near the first electrode is defined as 0, and the thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0–0.4D of the light-emitting layer, the ratio of the sensitizer doping concentration to the fluorescent guest material doping concentration is 10–100; in the thickness region of 0.4D–0.6D of the light-emitting layer, the ratio is 80–100; and in the thickness region of 0.6D–D of the light-emitting layer, the ratio is 10–100.

[0260] Comparative Example 1 A blue light-emitting device is fabricated, comprising an anode, a cathode, and a light-emitting functional part located between the anode and the cathode. The light-emitting layer of the light-emitting functional part comprises a host material and a fluorescent dopant material.

[0261] Comparative Example 2 A blue light-emitting device is fabricated, comprising an anode, a cathode, and a light-emitting functional layer located between the anode and the cathode. The light-emitting functional layer comprises a host material and a phosphorescent dopant material.

[0262] Comparative Example 3 A blue light-emitting device is fabricated, comprising an anode, a cathode, and a light-emitting functional layer located between the anode and the cathode. The light-emitting functional layer comprises a host material, a sensitizer, and a fluorescent guest material. Specifically, along the direction from the anode to the cathode, the light-emitting layer is uniformly doped with the sensitizer and the fluorescent guest material, with a total doping concentration of 10% for the sensitizer and 1% for the fluorescent guest material.

[0263] For the blue light-emitting devices corresponding to Examples 1-9 and Comparative Examples 1-3, at a current density of 10 mA / cm² 2 Under these conditions, the luminous efficiency (Eff) of the blue light-emitting device was tested, as well as the device lifetime when the brightness decayed to 95%, and the emission peak (Main Peak) and corresponding full width at half maximum (FWHM) in the emission spectrum were recorded. The test results are shown in Table 1. Table 1

[0264] As shown in Table 1, the luminous efficiency and lifetime of the blue light-emitting devices provided in Examples 1-9 are higher than those provided in Comparative Example 1, indicating that introducing a sensitizer into the doping material of the blue light-emitting layer can effectively improve the luminous efficiency and lifetime of the blue light-emitting device. Examples 1-5 show that the luminous efficiency and lifetime vary under different fluorescence and phosphorescence doping concentrations. At suitable doping concentrations for both, the energy transfer efficiency and buffering protection effect between the phosphorescence sensitizer and the fluorescent guest material can achieve a better balance, simultaneously achieving good luminous efficiency and lifetime. Examples 1-8 also show that by making the doping concentration of the fluorescent guest material approximately W-shaped and the doping concentration of the sensitizer approximately M-shaped, the blue light luminous efficiency is further improved; while by making the doping concentration of the fluorescent guest material approximately M-shaped and the doping concentration of the sensitizer approximately W-shaped, the lifetime of the blue light-emitting device is further improved. As can be seen from Example 9, the blue light emission efficiency can be significantly improved by introducing fluorescent guest materials into the stacked device.

[0265] The test results in Table 1 also show that the luminous efficiency and device lifetime of the blue light-emitting devices provided in Examples 1 to 8 are higher than those of the blue light-emitting devices provided in Comparative Example 2. This indicates that compared to using only phosphorescent dopant in the light-emitting layer for light emission, introducing sensitizers and fluorescent guest materials into the dopant material of the blue light-emitting layer can better improve the luminous efficiency and device lifetime of the blue light-emitting devices.

[0266] The test results in Table 1 also show that the luminous efficiency and device lifetime of the blue light-emitting devices provided in Examples 1 and 3 are higher than those of the blue light-emitting device provided in Comparative Example 3. This indicates that compared with uniformly doping sensitizers and fluorescent guest materials in the light-emitting layer, by flexibly adjusting the relative concentration ratio of sensitizers and fluorescent guest materials in different thickness regions of the light-emitting layer and realizing differentiated exciton capture and energy transfer modes, the luminous efficiency and device lifetime of the blue light-emitting device can be better improved.

[0267] Unlike related technologies, this application makes the luminescent layer include a host material, a sensitizer, and a fluorescent guest material, and limits the emission peak wavelength range of the luminescent layer to 430nm~470nm. It can introduce the sensitizer as an energy transfer bridge, so as to fully capture and efficiently transfer the excitons in the luminescent layer to the narrow-spectrum fluorescent guest material for luminescence. This achieves a high exciton utilization rate while maintaining the narrow spectrum and high color purity of the fluorescent material itself, thereby improving the blue light emission efficiency of the blue light emission device. Meanwhile, by setting the ratio of sensitizer doping concentration to fluorescent guest material doping concentration to 10-100 in the 0-0.4D thickness region of the luminescent layer; and / or, setting the ratio of sensitizer doping concentration to fluorescent guest material doping concentration to 0.5-15 or 80-100 in the 0.4D-0.6D thickness region of the luminescent layer; and / or, setting the ratio of sensitizer doping concentration to fluorescent guest material doping concentration to 10-100 in the 0.6D-D thickness region of the luminescent layer, the relative concentration ratio of sensitizer to fluorescent guest material can be flexibly adjusted in different thickness regions of the luminescent layer, achieving differentiated exciton capture and energy transfer modes. This improves blue light emission efficiency while also meeting the comprehensive performance requirements of high color purity and device lifetime.

[0268] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A light-emitting device, characterized in that, include: First electrode; Second electrode; At least one light-emitting layer is disposed between the first electrode and the second electrode. The light-emitting layer includes a host material, a sensitizer, and a fluorescent guest material. The emission peak wavelength range of the light-emitting layer is 430 nm to 470 nm. The thickness of the light-emitting layer is defined as D. The thickness of the surface of the light-emitting layer near the first electrode is defined as 0. The thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0 to 0.4 D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100. And / or, in the thickness region of 0.4 D to 0.6 D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 0.5 to 15 or 80 to 100. And / or, in the thickness region of 0.6 D to D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10 to 100.

2. The light-emitting device according to claim 1, characterized in that, In the 0~0.4D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase; and / or, in the 0.6D~D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease.

3. The light-emitting device according to claim 2, characterized in that, In the 0.4D~0.5D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease; and / or, in the 0.5D~0.6D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase.

4. The light-emitting device according to claim 1, characterized in that, In the 0~0.4D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase; and / or, in the 0.6D~D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease.

5. The light-emitting device according to claim 4, characterized in that, In the 0.4D~0.5D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to increase, while the doping concentration of the sensitizer tends to decrease; and / or, in the 0.5D~0.6D thickness region of the luminescent layer, the doping concentration of the fluorescent guest material tends to decrease, while the doping concentration of the sensitizer tends to increase.

6. The light-emitting device according to claim 1, characterized in that, The sensitizer includes a phosphorescent material or a TADF-type material; and / or, the host material includes at least one material. Preferably, the sensitizer comprises a phosphorescent material; Preferably, the sensitizer includes platinum. Preferably, the glass transition temperature of the main material is greater than 110 degrees Celsius; Preferably, the host material contains silicon and / or deuteration; Preferably, the host material includes a first host material and a second host material; wherein the hole mobility of the first host material is higher than that of the second host material, and the electron mobility of the second host material is higher than that of the first host material. Preferably, the volume ratio of the first main material to the second main material is between 2:8 and 8:2; Preferably, the first host material and the second host material form an excitocomplex, and the excitocomplex is TADF in nature.

7. The light-emitting device according to claim 1, characterized in that, The total doping concentration of the sensitizer is 2% to 20%, and / or the total doping concentration of the fluorescent guest material is 0.2% to 4%. Preferably, the total doping concentration of the sensitizer is 3% to 15%, and / or the total doping concentration of the fluorescent guest material is 0.2% to 2%. Preferably, the total doping concentration of the sensitizer is 8% to 12%, and / or the total doping concentration of the fluorescent guest material is 0.5% to 1%.

8. The light-emitting device according to claim 1, characterized in that, The light color of the sensitizer is the same as the light color of the fluorescent guest material.

9. The light-emitting device according to claim 1, characterized in that, The sensitizer has a first concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the sensitizer has a second concentration distribution line in the 0.5D~D thickness region of the luminescent layer, the first concentration distribution line and the second concentration distribution line being symmetrically distributed; and / or, the fluorescent guest has a third concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the fluorescent guest has a fourth concentration distribution line in the 0.5D~D thickness region of the luminescent layer, the third concentration distribution line and the fourth concentration distribution line being symmetrically distributed.

10. The light-emitting device according to claim 1, characterized in that, The sensitizer includes a phosphorescent material, wherein the triplet exciton energy level of the phosphorescent material is greater than or equal to the singlet exciton energy level of the fluorescent guest material; Preferably, the energy difference between the singlet exciton level of the fluorescent guest material and the triplet exciton level of the fluorescent guest material is less than or equal to 0.2 eV.

11. The light-emitting device according to claim 1, characterized in that, The fluorescent guest material contains deuterated and / or tert-butyl groups.

12. The light-emitting device according to claim 1, characterized in that, The thickness of the light-emitting layer ranges from 10 to 35 nm; Preferably, the thickness of the light-emitting layer is in the range of 13~30nm.

13. The light-emitting device according to claim 1, characterized in that, The light-emitting device further includes an electron blocking layer, the thickness of which ranges from 2 to 10 nm; Preferably, the thickness of the electron blocking layer is in the range of 3~8 nm; Preferably, the host material includes a first host material and a second host material, wherein the first host material is one of a P-type host material or an N-type host material, and the second host material is the other of a P-type host material or an N-type host material, and the material of the electron blocking layer is the same as the P-type host material; Preferably, it further includes a hole transport layer, wherein the HOMO level of the electron blocking layer material is located between the HOMO level of the host material and the HOMO level of the hole transport layer material.

14. The light-emitting device according to claim 1, characterized in that, The light-emitting device further includes an electron transport layer, a hole blocking layer, an electron injection layer, and a hole transport layer; the thickness of the electron transport layer is in the range of 10~50nm; and / or, the thickness of the hole blocking layer is in the range of 0~10nm; and / or, the thickness of the electron injection layer is less than 2nm; and / or, the thickness of the hole transport layer is in the range of 100~140nm. Preferably, the thickness of the electron transport layer is 20-40 nm; and / or, the thickness of the hole blocking layer is 2-8 nm; and / or, the thickness of the electron injection layer is less than 1 nm; and / or, the thickness of the hole transport layer is 110-130 nm.

15. The light-emitting device according to claim 1, characterized in that, The light-emitting device further includes a light extraction layer, the refractive index of which is between 1.8 and 2.5; and / or, The thickness of the light extraction layer is between 50nm and 100nm; Preferably, the refractive index of the light extraction layer is between 2.1 and 2.3, and the thickness of the light extraction layer is between 60 nm and 75 nm.

16. The light-emitting device according to claim 1, characterized in that, The light-emitting device includes a light-emitting functional layer, the light-emitting functional layer includes at least two light-emitting units, the at least two light-emitting units are stacked along a direction perpendicular to the light-emitting layer, a charge-generating layer is disposed between two adjacent light-emitting units, and at least one light-emitting unit includes the light-emitting layer; Preferably, all of the light-emitting units include at least one light-emitting layer.

17. The light-emitting device according to claim 1, characterized in that, In the 0~0.4D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease; and / or, in the 0.6D~D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase.

18. The light-emitting device according to claim 17, characterized in that, In the 0.4D~0.5D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to increase; and / or, in the 0.5D~0.6D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material tends to decrease.

19. A light-emitting device, characterized in that, include: First electrode; Second electrode; At least one light-emitting layer is disposed between the first electrode and the second electrode. The light-emitting layer includes a host material, a sensitizer, and a fluorescent guest material. The emission peak wavelength range of the light-emitting layer is 430 nm to 470 nm. The thickness of the light-emitting layer is defined as D. The thickness of the surface of the light-emitting layer near the first electrode is defined as 0. The thickness of the surface of the light-emitting layer near the second electrode is defined as D. In the thickness region of 0 to 0.4D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material increases. And / or, in the thickness region of 0.6D to D of the light-emitting layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material decreases.

20. The light-emitting device according to claim 19, characterized in that, In the 0~0.4D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100; and / or, in the 0.4D~0.6D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 80~100; and / or, in the 0.6D~D thickness region of the luminescent layer, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is 10~100.

21. The light-emitting device according to claim 19, characterized in that, The sensitizer has a first concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the sensitizer has a second concentration distribution line in the 0.5D~D thickness region of the luminescent layer, the first concentration distribution line and the second concentration distribution line being symmetrically distributed; and / or, the fluorescent guest has a third concentration distribution line in the 0~0.5D thickness region of the luminescent layer, and the fluorescent guest has a fourth concentration distribution line in the 0.5D~D thickness region of the luminescent layer, the third concentration distribution line and the fourth concentration distribution line being symmetrically distributed.

22. A display panel, characterized in that, Includes the light-emitting device according to any one of claims 1 to 21.

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