Light-emitting substrate, preparation method thereof and display device

Abstract

The invention discloses a light-emitting substrate, a preparation method thereof and a display device. The light-emitting substrate comprises a substrate body, a light-emitting unit and a light extraction piece. The light-emitting unit is located on one side of the substrate. The light emitting unit includes at least one blue light emitting device. The blue light-emitting device comprises a first electrode, at least one blue light-emitting layer and a second electrode which are stacked in sequence. The light-emitting unit further comprises a first light enhancement layer and a second light enhancement layer which are located on the side, away from the substrate, of the blue light-emitting device, and the first light enhancement layer is located between the blue light-emitting device and the second light enhancement layer. The light extraction piece is located on the side, away from the substrate, of the second light enhancement layer. And the orthographic projection of the light extraction piece on the substrate is at least partially overlapped with the orthographic projection of the blue light-emitting device on the substrate. Wherein the absolute value of the difference value between the wavelength corresponding to the transmittance peak value of the light extraction piece and the wavelength corresponding to the emission spectrum peak value of the blue light-emitting device is smaller than or equal to 10 nm.

Description

Luminescent substrate, preparation method thereof, and display device Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a light-emitting substrate, a method for preparing a light-emitting substrate, and a display device having the light-emitting substrate. Background Art

[0002] Currently, organic light-emitting diode (OLED) display devices have the advantages of self-luminescence, high luminous efficiency, energy saving, good flexibility, and adaptability to a wide range of ambient temperatures. Therefore, they are widely used in various occasions. In the blue light-emitting device of an OLED display device, the luminescent material of the blue light-emitting layer can be a blue phosphorescent material or a blue fluorescent material. Among them, blue fluorescent materials have better stability than blue phosphorescent materials, so blue fluorescent materials are more widely used in the blue light-emitting layer of OLED display devices.

[0003] Summary of the Invention

[0004] In one aspect, a light-emitting substrate is provided. The light-emitting substrate includes a base substrate, a light-emitting unit, and a light extraction element. The light-emitting unit is located on one side of the base substrate. The light-emitting unit includes at least one blue light-emitting device. The blue light-emitting device includes a first electrode, at least one blue light-emitting layer, and a second electrode, stacked in sequence along a direction away from the base substrate. The light-emitting unit also includes a first light-enhancing layer and a second light-enhancing layer, located on the side of the blue light-emitting device away from the base substrate, with the first light-enhancing layer located between the blue light-emitting device and the second light-enhancing layer. The second light-enhancing layer includes a first inorganic layer, an organic layer, and a second inorganic layer, stacked in sequence along a direction away from the base substrate from the first light-enhancing layer. The refractive index of the organic layer is lower than that of the first inorganic layer and lower than that of the second inorganic layer. The light extraction element is located on the side of the second light-enhancing layer away from the base substrate. The orthographic projection of the light extraction element on the base substrate at least partially overlaps with the orthographic projection of the blue light-emitting device on the base substrate. The absolute value of the difference between the wavelength corresponding to the transmittance peak of the light extraction element and the wavelength corresponding to the emission spectrum peak of the blue light-emitting device is less than or equal to 10 nm.

[0005] In some embodiments, the absolute value of the difference between the wavelength corresponding to the transmittance peak of the light extraction element and the wavelength corresponding to the emission spectrum peak of the blue light-emitting device is less than or equal to 3 nm.

[0006] In some embodiments, the orthographic projection of the light extraction member on the base substrate covers the orthographic projection of the light emitting portion of the blue light emitting device on the base substrate.

[0007] In some embodiments, the light extraction member is a cholesteric liquid crystal film layer.

[0008] In some embodiments, the second light enhancement layer further comprises a third inorganic layer disposed between the first light enhancement layer and the first inorganic layer, wherein the third inorganic layer has a refractive index less than that of the first light enhancement layer and less than that of the first inorganic layer.

[0009] In some embodiments, the blue light-emitting layer includes a first host material and a first guest material, wherein a ratio of an electron mobility of the first host material to a hole mobility of the first host material in the blue light-emitting layer is greater than or equal to 80.

[0010] In some embodiments, the first guest material is a metal complex comprising any one of iridium, platinum, palladium, or cerium metal elements and at least two nitrogen heterocyclic carbene ligands.

[0011] In some embodiments, in the blue light-emitting layer, the triplet energy level of the first host material is greater than the triplet energy level of the first guest material.

[0012] In some embodiments, the blue light-emitting layer includes a second host material, a sensitizer, and a second guest material, wherein the ratio of the electron mobility of the second host material to the hole mobility of the second host material in the blue light-emitting layer is less than or equal to 0.2.

[0013] In some embodiments, a ratio between the electron mobility of the sensitizer and the hole mobility of the sensitizer is greater than or equal to 8.

[0014] In some embodiments, the absolute value of the difference between the singlet energy level of the sensitizer and the triplet energy level of the sensitizer is less than or equal to 0.5 eV.

[0015] In some embodiments, the weight of the sensitizer accounts for less than or equal to 30% of the sum of the weight of the second host material and the weight of the sensitizer.

[0016] In some embodiments, the ratio of the weight of the second guest material to the sum of the weight of the second host material and the weight of the sensitizer is less than or equal to 5%.

[0017] In some embodiments, the ratio of the overlapping area between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer to the emission spectrum area of ​​the sensitizer is greater than or equal to 8%.

[0018] In some embodiments, the overlap area between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer accounts for less than or equal to 80% of the emission spectrum area of ​​the sensitizer.

[0019] In some embodiments, the second guest material is selected from any one of the structures represented by the following general formula:

[0020] Wherein, the substituents R1 to R18 are the same or different and are independently selected from any one of hydrogen, alkyl, aryl or heteroaryl. Adjacent substituents R1 to R18 may form a condensed ring or not.

[0021] In some embodiments, the wavelength corresponding to the peak of the emission spectrum of the blue light-emitting device is within the range of 440 nm to 480 nm, and the full width at half maximum of the emission spectrum of the blue light-emitting device is less than or equal to 50 nm.

[0022] In some embodiments, the light emitting substrate further includes an anti-reflection layer, and the anti-reflection layer is disposed on a side of the light extraction member away from the base substrate.

[0023] In another aspect, a method for preparing a light-emitting substrate is provided. The light-emitting substrate is a top-emitting type light-emitting substrate. The method comprises: providing a base substrate; forming a light-emitting unit on one side of the base substrate; the light-emitting unit comprising at least one blue light-emitting device. The blue light-emitting device comprises a first electrode, at least one blue light-emitting layer, and a second electrode, stacked in sequence along a direction away from the base substrate. The light-emitting unit further comprises a first light-enhancing layer and a second light-enhancing layer located on a side of the blue light-emitting device away from the base substrate, with the first light-enhancing layer located between the blue light-emitting device and the second light-enhancing layer. The second light-enhancing layer comprises a first inorganic layer, an organic layer, and a second inorganic layer, stacked in sequence along a direction away from the base substrate. The refractive index of the organic layer is less than the refractive index of the first inorganic layer and less than the refractive index of the second inorganic layer. A light extraction element is formed on a side of the second light-enhancing layer away from the base substrate. The orthographic projection of the light extraction element on the base substrate at least partially overlaps with the orthographic projection of the blue light-emitting device on the base substrate, and the absolute value of the difference between the wavelength corresponding to the transmittance peak of the light extraction element and the wavelength corresponding to the emission spectrum peak of the blue light-emitting device is less than or equal to 10 nm.

[0024] In another aspect, a display device is provided, comprising a circuit board and a light-emitting substrate according to any one of the above embodiments, wherein the light-emitting substrate is coupled to the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions of the present disclosure, the following briefly introduces the drawings required for use in some embodiments of the present disclosure. Obviously, the drawings described below are only drawings of some embodiments of the present disclosure, and those skilled in the art can also derive other drawings based on these drawings. Furthermore, the drawings described below are schematic diagrams and are not intended to limit the actual dimensions of the products, actual processes of the methods, actual timing of signals, and the like involved in the embodiments of the present disclosure.

[0026] FIG1 is a structural diagram of a display device according to some embodiments;

[0027] FIG2 is a structural diagram of a light-emitting substrate according to some embodiments;

[0028] FIG3 is a cross-sectional view of the light-emitting substrate along line AA′ according to the embodiment shown in FIG2 ;

[0029] 4 to 8 are diagrams showing the arrangement structures of sub-pixels in a light-emitting substrate according to some embodiments;

[0030] 9A to 9C are cross-sectional views of the light-emitting substrate along line AA' in FIG. 2 according to some embodiments;

[0031] FIG10 is a structural diagram of an emission spectrum of a blue light-emitting device according to some embodiments;

[0032] FIG11 is a structural diagram of a blue light emitting device according to some embodiments;

[0033] FIG12 is a schematic diagram of energy transfer of a superfluorescent material in a blue light-emitting layer according to some embodiments;

[0034] FIG13 is a general structural diagram of a second guest material according to some embodiments;

[0035] FIG14 is a structural diagram of an absorption spectrum of a second guest material and an emission spectrum of a sensitizer according to some embodiments;

[0036] FIG15 is a comparison diagram between a transmittance curve of a light extraction member according to some embodiments (Example 1) and an emission spectrum of a blue light-emitting device;

[0037] FIG16 is a structural diagram of the absorption spectrum of the second guest material C3 and the emission spectrum of the sensitizer B3 in Example 2;

[0038] FIG17 is a structural diagram of the absorption spectrum of the second guest material C4 and the emission spectrum of the sensitizer B3 in Example 3;

[0039] FIG18 is a structural diagram of the absorption spectrum of the second guest material C5 and the emission spectrum of the sensitizer B4 in Example 4;

[0040] FIG19 is a comparison diagram of the transmittance curves of the light extraction member and the emission spectrum of the blue light emitting device in Example 2, Example 5, and Comparative Example 3;

[0041] FIG20 is a flow chart of a method for preparing a light-emitting substrate according to some embodiments;

[0042] FIG. 21 is a flow chart of a method for preparing a light-emitting substrate according to some embodiments. DETAILED DESCRIPTION

[0043] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0044] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and its other forms, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to indicate that the particular features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0045] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0046] When describing some embodiments, the expressions "coupled" and "connected" and their derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The term "coupled" indicates, for example, that two or more components are in direct physical or electrical contact. The term "coupled" or "communicatively coupled" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0047] “At least one of A, B and C” has the same meaning as “at least one of A, B or C” and both include the following combinations of A, B and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B and C.

[0048] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0049] As used herein, the term "if" is optionally interpreted to mean "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined that" or "if [stated condition or event] is detected" are optionally interpreted to mean "upon determining" or "in response to determining" or "upon detecting [stated condition or event]" or "in response to detecting [stated condition or event]," depending on the context.

[0050] The use of "adapted to" or "configured to" herein is intended to be open and inclusive language that does not exclude devices adapted or configured to perform additional tasks or steps.

[0051] Additionally, the use of “based on” is meant to be open and inclusive, as a process, step, calculation, or other action “based on” one or more stated conditions or values ​​may, in practice, be based on additional conditions or values ​​beyond those stated.

[0052] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0053] As used herein, "parallel", "perpendicular", and "equal" include the situations described and situations similar to the situations described, and the range of the similar situations is within an acceptable deviation range, wherein the acceptable deviation range is as determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, wherein the acceptable deviation range of approximate parallelism can be, for example, a deviation within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, wherein the acceptable deviation range of approximate perpendicularity can also be, for example, a deviation within 5°. "Equal" includes absolute equality and approximate equality, wherein the acceptable deviation range of approximate equality can be, for example, that the difference between the two equals is less than or equal to 5% of either one.

[0054] It will be understood that when a layer or element is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may be present therebetween.

[0055] Exemplary embodiments are described herein with reference to cross-sectional and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and the area of ​​regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include deviations in shape due to, for example, manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0056] Currently, in the blue light-emitting layer of an OLED display device, blue phosphorescent materials have poor stability and short lifespan, while blue fluorescent materials have good stability. Therefore, blue fluorescent materials are more widely used in the blue light-emitting layer.

[0057] However, the inventors of this disclosure have discovered that, in blue light-emitting devices, the exciton utilization rate of the blue fluorescent material is low, resulting in low luminous efficiency of the blue light-emitting devices in the light-emitting substrate. To increase the light output of the blue light-emitting devices, it is necessary to increase the operating load (including operating current and / or operating voltage) of the blue light-emitting devices. Furthermore, due to leakage current between adjacent light-emitting devices, a higher operating load can easily illuminate red and / or green light-emitting devices adjacent to the blue light-emitting devices, thereby increasing the display light of other colors and reducing the color display effect of the light-emitting substrate.

[0058] Based on this, the embodiments of the present disclosure provide a light-emitting substrate and a method for manufacturing the same, as well as a display device, to overcome the above-mentioned problems, which are described below.

[0059] FIG. 1 is a structural diagram of a display device according to some embodiments.

[0060] Referring to FIG1 , some embodiments of the present disclosure provide a display device 3000. The display device 3000 can be used to display images or pictures. For example, the display device 3000 can be a small or medium-sized display device such as a tablet computer, a smart phone, a head-mounted display, a car navigation unit, a camera, an in-vehicle center information display (CID), a watch-type display device or other wearable device, a personal digital assistant (PDA), a portable multimedia player (PMP), and a game console, as well as medium or large electronic devices such as televisions, external billboards, monitors, home appliances including display screens, personal computers, and laptop computers. The above electronic devices may represent simple examples of application display devices, so those skilled in the art will recognize that the display device 3000 may also be other electronic devices without departing from the spirit and scope of the present disclosure.

[0061] As shown in FIG1 , a display device 3000 may include a light-emitting substrate 1000 and a circuit board 2000, wherein the light-emitting substrate 1000 is coupled to the circuit board 2000. The circuit board 2000 may be located on the backlight side of the light-emitting substrate 1000 (i.e., the side opposite the display side of the light-emitting substrate 1000). For example, the circuit board 2000 may be a flexible printed circuit board (FPC) or a printed circuit board. The circuit board 2000 may provide a light-emitting data signal, and the light-emitting substrate 1000 emits light based on the light-emitting data signal provided by the circuit board 2000.

[0062] Figure 2 is a structural diagram of a light emitting substrate provided by some embodiments of the present disclosure. Figure 3 is a cross-sectional view of the light emitting substrate along line AA' according to the embodiment shown in Figure 2 .

[0063] Referring to Figures 2 and 3 , some embodiments of the present disclosure provide a light-emitting substrate 1000. Light-emitting substrate 1000 is a display component capable of emitting display light. Light-emitting substrate 1000 can emit monochromatic light (single-color light) or colored light. Light-emitting substrate 1000 can be used in the aforementioned display device 3000 or lighting device.

[0064] In some embodiments, as shown in FIG3 , the light emitting substrate 1000 may be a top-emitting light emitting substrate, which can be understood as the direction in which the light emitting substrate 1000 emits light toward the display side of the light emitting substrate 1000 .

[0065] The light-emitting substrate 1000 may include a base substrate 100, a light-emitting unit 200, and a light extraction member 300. The light-emitting unit 200 is located on one side of the base substrate 100, and the light extraction member 300 may be located on a side of the light-emitting unit 200 away from the base substrate 100. Light emitted from the light-emitting unit 200 may sequentially pass through the light extraction member 300 and the anti-reflection layer 400 to reach the outside of the light-emitting substrate 1000.

[0066] The following is a detailed description of the base substrate 100 , the light emitting unit 200 , and the light extraction member 300 in the light emitting substrate 1000 .

[0067] As shown in FIG3 , the substrate 100 may include a plurality of pixel unit regions PU arranged in a repeated pattern. Each pixel unit region PU may include a first sub-pixel region P1, a second sub-pixel region P2, and a third sub-pixel region P3 that display different colors. For example, the first sub-pixel region P1 is configured to display blue light, the second sub-pixel region P2 is configured to display green light, and the third sub-pixel region P3 is configured to display red light.

[0068] In addition, the pixel unit area PU may further include a non-emission area P4 located between the first sub-pixel area P1 and the second sub-pixel area P2, between the second sub-pixel area P2 and the third sub-pixel area P3, and between the third sub-pixel area P3 and the first sub-pixel area P1.

[0069] 4 to 8 are diagrams showing the arrangement structures of sub-pixels in a light-emitting substrate according to some embodiments.

[0070] In some examples, as shown in Figures 4 to 6, a pixel unit region PU includes a first sub-pixel region P1, a second sub-pixel region P2, and a third sub-pixel region P3. The first sub-pixel region P1, the second sub-pixel region P2, and the third sub-pixel region P3 can be spaced apart and repeatedly arranged.

[0071] In some examples, as shown in Figures 7 and 8, a pixel unit area PU may include two sub-pixel areas displaying the same color, and the two sub-pixel areas displaying the same color may be arranged adjacent to each other. For example, a pixel unit area PU includes a red sub-pixel area R, two green sub-pixel areas G, and one blue sub-pixel area B, wherein the two green sub-pixel areas G in a pixel unit area PU may be arranged adjacent to each other.

[0072] In some examples, a pixel unit area PU includes a first sub-pixel area P1, two second sub-pixel areas P2, and a third sub-pixel area P3. The first sub-pixel area P1, the two second sub-pixel areas P2, and the third sub-pixel area P3 can be spaced apart and arranged repeatedly. In this case, the non-luminous area P4 can also be located between the two second sub-pixel areas P2.

[0073] 9A to 9C are cross-sectional views of the light emitting substrate along line AA′ in FIG. 2 , respectively, according to some embodiments.

[0074] As shown in Figures 9A to 9C , the light-emitting substrate 1000 may include multiple pixel circuits located on the base substrate 100. A pixel unit area PU may include a first pixel circuit S1, a second pixel circuit S2, and a third pixel circuit S3. For example, the first pixel circuit S1 is located in the first sub-pixel area P1, the second pixel circuit S2 is located in the second sub-pixel area P2, and the third pixel circuit S3 is located in the third sub-pixel area P3. For another example, the thin film transistor of at least one of the first pixel circuit S1, the second pixel circuit S2, and the third pixel circuit S3 may be located in the non-light-emitting area P4.

[0075] There are many structures of pixel circuits, which can be selected and set according to actual needs. For example, the pixel circuit may include: at least two transistors and at least one capacitor. For example, the pixel circuit may have a structure such as "2T1C", "6T1C", "7T1C", "6T2C" or "7T2C". Among them, "T" represents a thin film transistor, the number before "T" represents the number of thin film transistors, "C" represents a storage capacitor, and the number before "C" represents the number of storage capacitors.

[0076] As shown in Figures 9A to 9C, the thin film transistor in at least one of the first pixel circuit S1, the second pixel circuit S2, and the third pixel circuit S3 may be a thin film transistor including polycrystalline silicon or a thin film transistor including an oxide semiconductor. For example, when the thin film transistor is a thin film transistor including an oxide semiconductor, it may have a top-gate thin film transistor structure. The thin film transistor may be connected to signal lines, including but not limited to gate lines, data lines, and power lines.

[0077] As shown in Figures 9A to 9C, the light-emitting substrate 1000 may include an insulating layer INL, which may be located on the first pixel circuit S1, the second pixel circuit S2, and the third pixel circuit S3. The insulating layer INL may have a planarized surface. The insulating layer INL may be formed of an organic layer. For example, the material of the insulating layer INL may include acrylic resin, epoxy resin, imide resin, or ester resin. The insulating layer INL may have through holes for exposing the electrodes of the first pixel circuit S1, the second pixel circuit S2, and the third pixel circuit S3 to achieve electrical connection.

[0078] As shown in Figures 9A to 9C , the light-emitting substrate 1000 may include a pixel definition layer (PDL) located on a base substrate 100. The pixel definition layer (PDL) may be formed on an insulating layer (INL) and may have a plurality of light-emitting openings. For example, the pixel definition layer (PDL) may include a first light-emitting opening (K1) located in a first sub-pixel region (P1), a second light-emitting opening (K2) located in a second sub-pixel region (P2), and a third light-emitting opening (K3) located in a third sub-pixel region (P3).

[0079] The light-emitting unit 200 may be located on a side of the insulating layer INL away from the base substrate 100. The light-emitting unit 200 may include multiple light-emitting devices, each of which covers a plurality of light-emitting openings, and each of the multiple light-emitting devices is connected to a plurality of pixel circuits in a one-to-one correspondence. The multiple light-emitting devices include at least one blue light-emitting device 210. For example, within a pixel unit area PU of the light-emitting unit 200, the light-emitting devices include a red light-emitting device, a green light-emitting device, and a blue light-emitting device 210. The blue light-emitting device 210 may cover the first light-emitting opening K1, the green light-emitting device may cover the second light-emitting opening K2, and the red light-emitting device may cover the third light-emitting opening K3.

[0080] FIG. 10 is a structural diagram illustrating an emission spectrum of a blue light-emitting device according to some embodiments.

[0081] In some embodiments, as shown in FIG10 , the wavelength λ corresponding to the peak emission spectrum of the blue light-emitting device 210 is within the range of 440 nm to 480 nm, such as 440 nm, 450 nm, 460 nm, 470 nm, or 480 nm. Limiting the wavelength corresponding to the peak emission spectrum of the blue light-emitting device 210 to the range of 440 nm to 480 nm can reduce the irritation and damage to the human eye caused by the blue light emitted by the blue light-emitting device 210.

[0082] In this embodiment, as shown in FIG10 , the full width at half maximum (FWHM) d of the emission spectrum of the blue light-emitting device 210 is less than or equal to 50 nm, such as 15 nm, 20 nm, 22 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm. The full width at half maximum (d) of the emission spectrum of the blue light-emitting device 210 represents the width (i.e., the difference) of the wavelength corresponding to half the peak value of the emission spectrum of the blue light-emitting device 210. The narrower the full width at half maximum of the emission spectrum of the blue light-emitting device 210, the higher the color purity of the blue light emitted by the blue light-emitting device 210. Therefore, limiting the full width at half maximum of the emission spectrum of the blue light-emitting device 210 to a smaller range can improve the color purity of the blue light emitted by the blue light-emitting device 210.

[0083] As shown in Figures 9A to 9C , the blue light-emitting device 210 may include a first electrode AE, at least one blue light-emitting layer 21, and a second electrode CE, stacked sequentially in a direction away from the base substrate 100. For example, the light-emitting substrate 1000 may be a top-emitting light-emitting substrate. The first electrode AE ​​is a reflective electrode that reflects light, such as an anode. The second electrode CE is a transmissive electrode that transmits light, such as a cathode. Thus, a microcavity structure is formed between the anode and cathode. The blue light-emitting device 210 may include one or more blue light-emitting layers 21. For example, the blue light-emitting device 210 may be a stacked light-emitting device including two or three blue light-emitting layers 21.

[0084] In some examples, the first electrode AE ​​may include a laminated composite structure of transparent conductive oxide / metal / transparent conductive oxide. The transparent conductive oxide material may be, for example, ITO or IZO, and the metal material may be, for example, Au, Ag, Ni, or Pt. For example, the anode structure may be: ITO / Ag / ITO. The average reflectivity of the first electrode AE ​​for visible light may be in the range of 85% to 95%. The second electrode CE may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, or compounds or mixtures thereof, such as a mixture of Ag and Mg.

[0085] FIG. 11 is a structural diagram of a blue light-emitting device according to some embodiments.

[0086] In some embodiments, as shown in FIG11 , a blue light-emitting device 210 may include a first transport layer TL1, a blue light-emitting layer 21, and a second transport layer TL2. The first transport layer TL1 may be located between the blue light-emitting layer 21 and the first electrode AE, and may be configured to transport holes from the first electrode AE ​​to the blue light-emitting layer 21. The second transport layer TL2 may be located between the blue light-emitting layer 21 and the second electrode CE, and may be configured to transport electrons from the second electrode CE to the blue light-emitting layer 21. Thus, holes and electrons may recombine in the blue light-emitting layer 21, causing the blue light-emitting layer 21 to emit light.

[0087] For example, as shown in FIG11 , the first transport layer TL1 may include a first hole injection layer HIL1 and a first hole transport layer HTL1. The first hole injection layer HIL1 is located between the first electrode AE ​​and the first hole transport layer HTL1 and is configured to inject holes from the first electrode AE ​​into the first hole transport layer HTL1. The first hole transport layer HTL1 is located between the first hole injection layer HIL1 and the blue light-emitting layer 21 and is configured to transport holes injected by the first hole injection layer HIL1 to the blue light-emitting layer 21, allowing the holes to recombine with electrons within the blue light-emitting layer 21, thereby emitting light from the blue light-emitting layer 21.

[0088] In some examples, as shown in FIG11 , the first transport layer TL1 may further include a first exciton blocking layer BL1. The first exciton blocking layer BL1 may be located between the first hole transport layer HTL1 and the blue light-emitting layer 21. The first exciton blocking layer BL1 is configured to block electrons in the blue light-emitting layer 21 from moving toward the first electrode AE. Therefore, the first exciton blocking layer BL1 may also be referred to as an electron blocking layer EBL.

[0089] In some examples, as shown in FIG11 , the second transport layer TL2 may include a first electron transport layer ETL1 and a first electron injection layer EIL1. The first electron injection layer EIL1 is located between the first electron transport layer ETL1 and the second electrode CE, and is configured to inject electrons provided by the second electrode CE into the first electron transport layer ETL1. The first electron transport layer ETL1 is located between the first electron injection layer EIL1 and the blue light-emitting layer 21, and is configured to transport electrons injected by the first electron injection layer EIL1 to the blue light-emitting layer 21, allowing the electrons to recombine with holes in the blue light-emitting layer 21, thereby achieving light emission from the blue light-emitting layer 21.

[0090] In some examples, as shown in FIG11 , the second transport layer TL2 may further include a second exciton blocking layer BL2. The second exciton blocking layer BL2 may be located between the first electron transport layer ETL1 and the blue light-emitting layer 21. The second exciton blocking layer BL2 is configured to block holes in the blue light-emitting layer 21 from moving toward the second electrode CE. Therefore, the second exciton blocking layer BL2 may also be referred to as a hole blocking layer HBL.

[0091] In some embodiments, the blue light emitting layer 21 may include a blue phosphorescent light emitting material. The blue light emitting layer 21 may include a first host material and a first guest material.

[0092] The first host material may include a hole injection and transport material and an electron injection and transport material, and have excellent hole transport performance and electron transport performance. Exemplarily, the first host material may include at least one triazine group and at least one carbazole group. For example, the first host material may include one triazine group and one carbazole group. For another example, the first host material may include one triazine group and two carbazole groups.

[0093] In the blue light-emitting layer 21, the ratio of the electron mobility of the first host material to the hole mobility of the first host material is greater than or equal to 80, for example, 80, 82, 86, 90, 92, 95, 98, 100, 110, or 120. By limiting the ratio of the electron mobility of the first host material to the hole mobility of the first host material to a relatively large range, that is, limiting the electron mobility of the first host material to be much greater than the hole mobility of the first host material, the electron transport rate in the blue light-emitting layer 21 can be made greater than the hole transport rate, so that the first host material has good triplet exciton confinement ability, thereby preventing excitons in the blue light-emitting layer 21 from being transmitted to the second electrode CE (i.e., the cathode), confining the excitons within the blue light-emitting layer 21, and ensuring carrier balance, thereby improving the luminous efficiency of the blue light-emitting layer 21.

[0094] The first guest material may be a blue phosphorescent material having better luminescence performance.

[0095] In some examples, the first guest material may be a metal complex comprising any one of iridium, platinum, palladium, or cerium metal elements and at least two nitrogen heterocyclic carbene ligands. For example, the first guest material may be a metal complex comprising iridium metal element and two nitrogen heterocyclic carbene ligands. For another example, the first guest material may be a metal complex comprising platinum metal element and two nitrogen heterocyclic carbene ligands.

[0096] The metal complex selected for the first guest material has good compatibility between the iridium, platinum, palladium or cerium metal elements and the nitrogen heterocyclic carbene ligand. The metal complex has a high internal quantum efficiency and a higher triplet energy level than existing blue phosphorescent materials and blue fluorescent materials, which can improve the luminous efficiency of the blue light-emitting layer 21.

[0097] In some examples, in the blue light-emitting layer 21, the triplet energy level of the first host material is greater than the triplet energy level of the first guest material. The difference between the triplet energy levels of the first host material and the first guest material is greater than or equal to 0.1 eV, such as 0.1 eV, 0.12 eV, 0.15 eV, 0.2 eV, 0.3 eV, 0.5 eV, 0.8 eV, or 1 eV.

[0098] In this way, the triplet excitons in the first host material with a higher triplet energy level can confine and block the triplet excitons with relatively low energy levels in the blue light-emitting layer 21 from being transmitted to the second electrode CE (i.e., the cathode), thereby confining the triplet excitons in the blue light-emitting layer 21 and improving the luminous efficiency of the blue light-emitting layer 21.

[0099] In some examples, in the blue light-emitting layer 21, the weight ratio of the first host material to the weight ratio of the blue light-emitting layer 21 is greater than or equal to 70%, such as 70%, 75%, 80%, 85%, 90%, or 95%. The weight ratio of the first guest material to the weight ratio of the blue light-emitting layer 21 is less than or equal to 30%, such as 5%, 8%, 10%, 15%, 20%, 25%, or 30%.

[0100] The luminescence performance of the first guest material (i.e., blue phosphorescent material) is better than that of the first host material. By respectively limiting the weight ratio of the first host material in the blue light-emitting layer 21 and the weight ratio of the first guest material in the blue light-emitting layer 21, the doping ratio of the weight of the first guest material in the weight of the first host material can be limited to an appropriate range, so that the luminescence efficiency of the blue light-emitting layer 21 is higher.

[0101] In this way, the working load (including driving voltage and working current) of the blue light-emitting device 210 can be reduced on the basis of improving the luminous efficiency of the blue light-emitting layer 21, thereby extending the service life of the blue light-emitting device 210, and reducing the probability of the red light-emitting device and / or green light-emitting device adjacent to the blue light-emitting device 210 being lit, thereby improving the color display effect of the light-emitting substrate 1000 and the display device 3000.

[0102] In other embodiments, the blue light-emitting layer 21 may include a blue superfluorescent light-emitting material, and the blue light-emitting layer 21 may include a second host material, a sensitizer, and a second guest material.

[0103] The second host material may include a hole injection and transport material and an electron injection and transport material, and have excellent hole transport performance and electron transport performance. Exemplarily, the second host material may include at least one triazine group and at least one carbazole group. For example, the first host material may include one triazine group and one carbazole group. For another example, the first host material may include one triazine group and two carbazole groups.

[0104] In the blue light-emitting layer 21 , a ratio between the electron mobility of the second host material and the hole mobility of the second host material is less than or equal to 0.2, for example, 0.05, 0.1, 0.15 or 0.2.

[0105] By limiting the ratio between the electron mobility of the second main material and the hole mobility of the second main material to a smaller range, the electron transport performance and hole transport performance of the blue light-emitting layer 21 can be improved, and the electrons and holes in the blue light-emitting layer 21 can be evenly distributed to ensure carrier balance, thereby improving the utilization rate of electrons and holes in the blue light-emitting layer 21, and further improving the luminous efficiency of the blue light-emitting layer 21.

[0106] The sensitizer may be a thermally activated delayed fluorescent material having luminescent properties. For example, the sensitizer may include at least one carbazole group and at least one cyano group. For example, the sensitizer may include two carbazole groups and one cyano group. For another example, the sensitizer may include four carbazole groups and one cyano group.

[0107] FIG12 is a schematic diagram illustrating energy transfer of a superfluorescent material in a blue light-emitting layer according to some embodiments.

[0108] As shown in Figure 12, thermally activated delayed fluorescent materials utilize purely organic building blocks to effectively separate the lowest occupied molecular orbital (HOMO) and the highest unoccupied molecular orbital (LUMO), reducing the energy difference between the singlet and triplet states of the lowest excited carrier. Thermally activated delayed fluorescent material molecules can convert triplet excitons into singlet excitons through reverse intersystem crossing, and then return to the ground state through radiative transition, thereby emitting fluorescence, which can improve the exciton utilization rate of the blue light-emitting layer.

[0109] In some examples, the ratio between the electron mobility of the sensitizer and the hole mobility of the sensitizer is greater than or equal to 8, eg, 8, 10, 12, 15, or 20.

[0110] By limiting the ratio between the electron mobility of the sensitizer and the hole mobility of the sensitizer within a larger range, that is, limiting the electron mobility of the sensitizer to be much greater than the hole mobility of the sensitizer, the electron transfer rate of the carriers in the blue light-emitting layer 21 can be greater than the hole transfer rate, so that the sensitizer has good triplet exciton confinement ability, so as to block the excitons in the blue light-emitting layer 21 from being transmitted to the second electrode CE (i.e., the cathode), confine the excitons within the blue light-emitting layer 21, and at the same time ensure carrier balance, thereby improving the luminous efficiency of the blue light-emitting layer 21.

[0111] In some examples, the absolute value of the difference between the singlet energy level of the sensitizer and the triplet energy level of the sensitizer is less than or equal to 0.5 eV, such as 0.1 eV, 0.2 eV, 0.3 eV, 0.4 eV, or 0.5 eV.

[0112] The difference between the singlet energy level of the sensitizer and the triplet energy level of the sensitizer is limited to a smaller range, that is, the singlet energy level of the sensitizer is closer to the triplet energy level of the sensitizer, which reduces the difficulty of converting the triplet excitons of the sensitizer into singlet excitons through the reverse intersystem crossing process. Therefore, the exciton utilization rate in the blue light-emitting layer 21 can be improved, thereby improving the luminous efficiency of the blue light-emitting layer 21.

[0113] In some examples, the weight of the sensitizer accounts for less than or equal to 30% of the sum of the weight of the second host material and the weight of the sensitizer, such as 5%, 10%, 15%, 20%, 25%, or 30%.

[0114] Since the sum of the weight of the sensitizer and the weight of the second main material accounts for a high proportion (close to 100%) in the weight of the blue light-emitting layer 21, limiting the weight ratio of the sensitizer to the weight ratio of the blue light-emitting layer 21 is equivalent to limiting the weight ratio of the second main material to the weight ratio of the blue light-emitting layer 21, which can ensure that the blue light-emitting layer 21 has higher electron transport performance and higher hole transport performance, and thus ensure that the blue light-emitting layer 21 has higher luminous efficiency; at the same time, limiting the weight ratio of the sensitizer to the weight ratio of the blue light-emitting layer 21 can also prevent energy quenching when electrons and holes recombine under the action of a sensitizer with too high a weight ratio (i.e., a sensitizer with too high a concentration).

[0115] In this embodiment, the second guest material may be a multiple resonance fluorescent material. The second guest material may include at least one boron atom and at least two nitrogen atoms. For example, the second guest material may include three boron atoms and three nitrogen atoms.

[0116] FIG. 13 is a general structural diagram of a second guest material according to some embodiments.

[0117] In some examples, the second guest material is selected from any of the general structures shown in Figure 13. Substituents R1-R18 are the same or different and are independently selected from any of hydrogen, alkyl, aryl, or heteroaryl groups; and adjacent substituents R1-R18 may or may not form a fused ring. For example, in the general structure of the second guest material shown in Figure 13, substituents R1-R18 may be independently selected from any of hydrogen, C1-C12 alkyl, C6-C30 aryl, or C3-C30 heteroaryl groups.

[0118] The second guest material is a multi-resonance material with a general structural formula as shown in FIG13 , which can form a multi-resonance type thermally activated delayed fluorescent material with a sensitizer. Since the multi-resonance type thermally activated delayed fluorescent material has a multi-resonance effect within the molecule, its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels can be effectively separated to different atoms, thereby promoting the radiation rate and minimizing the energy level difference between the singlet state and the triplet state of the excitons in the blue light-emitting layer 21, which can improve the utilization rate of the excitons and thereby improve the luminous efficiency of the blue light-emitting layer 21.

[0119] In some examples, the weight of the second guest material is less than or equal to 5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, based on the weight of the second host material and the weight of the sensitizer.

[0120] Since the second guest material is a multi-resonance fluorescent material, the higher the weight ratio of the multi-resonance fluorescent material to the weight ratio of the blue light-emitting layer 21 (i.e., the concentration), the stronger the energy quenching and sensitivity are. Therefore, limiting the weight ratio of the second guest material to the weight ratio of the blue light-emitting layer 21 can reduce the energy quenching of the multi-resonance fluorescent material, thereby improving the luminous efficiency of the blue light-emitting layer 21.

[0121] 14 is a structural diagram of an absorption spectrum of a second guest material and an emission spectrum of a sensitizer according to some embodiments.

[0122] In some examples, as shown in FIG14 , the overlapping area S between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer accounts for greater than or equal to 8% of the emission spectrum area A of the sensitizer, for example, 8%, 10%, 15%, 20%, 30%, or 50%.

[0123] The larger the ratio of the overlapping area S between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer to the emission spectrum area A of the sensitizer, the more conducive it is to the transfer of exciton energy on the sensitizer to the second guest material, which can improve the luminous efficiency of the second guest material, thereby improving the luminous efficiency of the blue light-emitting layer 21, and further improving the luminous efficiency of the blue light-emitting device 210. On the basis of improving the luminous efficiency of the blue light-emitting device 210, the working load of the blue light-emitting device 210 can be reduced, thereby extending the life of the blue light-emitting device 210.

[0124] In some examples, as shown in FIG. 14 , the overlapping area S between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer accounts for less than or equal to 80% of the emission spectrum area A of the sensitizer, for example, 10%, 15%, 20%, 30%, 50%, 60%, 70%, or 80%.

[0125] By limiting the ratio of the overlapping area S between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer to the emission spectrum area A of the sensitizer within a suitable range, the exciton energy transfer efficiency between the sensitizer and the second guest material can be greatly improved, thereby improving the luminous efficiency of the blue light-emitting layer 21, and further improving the luminous efficiency of the blue light-emitting device 210.

[0126] In this embodiment, the singlet energy level of the second host material is greater than the singlet energy level of the sensitizer and greater than the triplet energy level of the sensitizer, and the triplet energy level of the second host material is also greater than the singlet energy level of the sensitizer and greater than the triplet energy level of the sensitizer; the singlet energy level of the sensitizer is greater than the singlet energy level of the second guest material and greater than the triplet energy level of the second guest material, and the triplet energy level of the sensitizer is also greater than the singlet energy level of the second guest material and greater than the triplet energy level of the second guest material. This facilitates the transfer of exciton energy from the second host material to the sensitizer, and then the transfer of exciton energy from the sensitizer to the second guest material, reducing losses during the exciton energy transfer process and thereby improving the luminous efficiency of the blue light-emitting layer 21.

[0127] In this way, on the basis of improving the luminous efficiency of the blue light-emitting device 210, the working load (including driving voltage and / or working current) of the blue light-emitting device 210 can be reduced, thereby extending the service life of the blue light-emitting device 210, and also reducing the probability of the red light-emitting device and / or green light-emitting device adjacent to the blue light-emitting device 210 being lit, thereby improving the color display effect of the light-emitting substrate 1000 and the display device 3000.

[0128] As shown in FIG3 and FIG9A to FIG9C , the light-emitting unit 200 further includes a first light-enhancing layer 220 located on a side of the blue light-emitting device 210 away from the base substrate 100. For example, the first light-enhancing layer 220 may be located on a surface of the second electrode CE away from the blue light-emitting layer 21. It can be understood that the first light-enhancing layer 220 may directly contact the surface of the second electrode CE away from the blue light-emitting layer 21.

[0129] The light emitted from the blue light emitting layer 21 may pass through the second electrode CE and then transmit into the first light enhancement layer 220 . The first light enhancement layer 220 is configured to increase the amount of displayable light emitted from the blue light emitting layer 21 .

[0130] The first light enhancement layer 220 may also be referred to as a light extraction layer or a light coupling layer. For example, the first light enhancement layer 220 may be a single-layer structure within the same pixel unit area PU. Within the same pixel unit area PU, the thickness of the first light enhancement layer 220 corresponding to the first sub-pixel area P1, the second sub-pixel area P2, and the third sub-pixel area P3 may be the same or different. For another example, the first light enhancement layer 220 may be a patterned structure within different pixel unit areas PU. The thickness of the first light enhancement layer 220 may be the same or different within different pixel unit areas PU.

[0131] Illustratively, the refractive index of the first light enhancement layer 220 may be greater than or equal to 1.8, such as 1.8, 1.9, or 2.0.

[0132] Since the refractive index of the first light enhancement layer 220 is relatively large, the light emitted from the blue light-emitting layer 21 is refracted after passing through the first light enhancement layer 220, and the refraction angle of the light is smaller than the incident angle, so that the propagation direction of the light emitted from the blue light-emitting layer 21 can be deflected toward a direction close to perpendicular to the base substrate 100, thereby increasing the amount of light emitted from the blue light-emitting layer 21, thereby improving the light extraction efficiency and display effect of the light-emitting substrate 1000 and the display device 3000.

[0133] In some embodiments, as shown in Figures 9A to 9C, the light-emitting unit 200 may further include a second light-enhancing layer 230. The second light-enhancing layer 230 may be located on a side of the first light-enhancing layer 220 away from the base substrate 100. The second light-enhancing layer 230 may include a first inorganic layer 24, an organic layer 25, and a second inorganic layer 26 stacked sequentially along a direction from the first light-enhancing layer 220 away from the base substrate 100. The refractive index of the first inorganic layer 24 and the refractive index of the second inorganic layer 26 are relatively large, and the refractive index of the organic layer 25 is smaller than the refractive index of the first inorganic layer 24 and the refractive index of the second inorganic layer 26.

[0134] The light emitted from the blue light-emitting layer 21 is constrained in sequence by the first inorganic layer 24 with a larger refractive index, the organic layer 25 with a smaller refractive index, and the second inorganic layer 26 with a larger refractive index, which can reduce the impact of blue light on color deviation under a wide viewing angle, thereby improving the display effect of the light-emitting substrate 1000 and the display device 3000.

[0135] In some examples, the second light enhancement layer 230 may have the ability to isolate water and oxygen, and may be configured to encapsulate the light emitting device in the light emitting unit 200 and the first light enhancement layer 220. Therefore, the second light enhancement layer may also be called an encapsulation layer.

[0136] For example, the material of the first inorganic layer 24 and the second inorganic layer 26 can be selected from at least one of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, silicon oxynitride, or lithium fluoride. The material of the organic layer 25 can be at least one of acrylic resin, methacrylic resin, polyisoprene, vinyl resin, epoxy resin, polyurethane resin, cellulose resin, or perylene resin. Those skilled in the art can modify the number of layers, materials, and structure of the thin film encapsulation layer as needed, and the present disclosure is not limited thereto.

[0137] 9A and 9B , the second light enhancement layer 230 may further include a third inorganic layer 27. The third inorganic layer 27 may be disposed between the first light enhancement layer 220 and the first inorganic layer 24. The refractive index of the third inorganic layer 27 is lower than that of the first light enhancement layer 220 and lower than that of the first inorganic layer 24.

[0138] For example, the refractive index of the first light enhancement layer 220 may be greater than or equal to 1.8 (e.g., 1.8, 1.9, or 2.0), the refractive index of the third inorganic layer 27 may be less than or equal to 1.5 (e.g., 1.3, 1.4, or 1.5), and the refractive index of the first inorganic layer 24 may also be greater than or equal to 1.8 (e.g., 1.8, 1.9, or 2.0).

[0139] Light emitted from the blue light-emitting layer 21 is sequentially constrained by the first light-enhancing layer 220 (with a relatively high refractive index), the third inorganic layer 27 (with a relatively low refractive index), and the first inorganic layer 24 (with a relatively high refractive index). This reduces the effect of blue light on color shift at wide viewing angles, thereby improving the display quality of the light-emitting substrate 1000 and the display device 3000. Furthermore, the sequentially stacked first inorganic layer 24, organic layer 25, and second inorganic layer 26 can also be configured to encapsulate the light-emitting device in the light-emitting unit 200 and the first light-enhancing layer 220.

[0140] In some embodiments, as shown in FIG3 and FIG9A-9C , the light extraction element 300 can be located on a side of the second light enhancement layer 230 away from the base substrate 100. The orthographic projection of the light extraction element 300 on the base substrate 100 at least partially overlaps with the orthographic projection of the blue light-emitting device 210 on the base substrate 100. It can be understood that the orthographic projection of the light extraction element 300 on the base substrate 100 partially overlaps with the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the base substrate 100; alternatively, the orthographic projection of the light extraction element 300 on the base substrate 100 covers the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the base substrate 100. The light-emitting portion of the blue light-emitting device 210 is the effective light-emitting area in the blue light-emitting layer 21 defined by the first light-emitting opening K1 and the first electrode AE ​​(anode) that the blue light-emitting device 210 covers.

[0141] At least part of the light emitted from the blue light-emitting device 210 can enter the light extraction element 300. Since the refractive index of the light extraction element 300 is relatively large, the propagation direction of at least part of the light emitted from the blue light-emitting device 210 can be deflected toward a direction close to perpendicular to the base substrate 100, which can increase the light output of the blue light-emitting device 210, thereby improving the light output efficiency and display effect of the light-emitting substrate 1000 and the display device 3000.

[0142] In some examples, the orthographic projection of the light extraction element 300 on the base substrate 100 partially overlaps with the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the base substrate 100. For example, as shown in FIG9A , the blue light-emitting device 210 may cover the first light-emitting opening K1, the green light-emitting device may cover the second light-emitting opening K2, and the red light-emitting device may cover the third light-emitting opening K3. The light extraction element 300 may be a patterned structure, and the orthographic projection of the light extraction element 300 on the base substrate 100 may only cover a portion of the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the base substrate 100, with the light extraction element 300 exposing the green and red light-emitting devices.

[0143] Among them, other parts of the light emitting substrate 1000 that are in the same layer as the patterned light extraction member 300 can be made into a flat surface by filling optically transparent adhesive, so as to facilitate the production of components in subsequent processes.

[0144] Part of the light emitted from the blue light-emitting device 210 enters the light extraction element 300, deflecting the propagation direction of the light emitted from the blue light-emitting device 210 toward a direction perpendicular to the base substrate 100. This improves the light extraction efficiency of the portion of the blue light-emitting device 210 corresponding to the light extraction element 300. Furthermore, the light extraction element 300 exposes the green and red light-emitting devices, ensuring that the light emitted by these devices is not blocked, thereby ensuring the luminous efficiency of these devices.

[0145] In other examples, the orthographic projection of the light extraction element 300 on the substrate 100 covers the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the substrate 100. Exemplarily, the orthographic projection of the light extraction element 300 on the substrate 100 covers the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the substrate 100 and is larger than the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the substrate 100. For example, as shown in FIG9C , the light extraction element 300 can be a whole-layer structure. The orthographic projection of the light extraction element 300 on the substrate 100 covers the orthographic projection of the light-emitting unit 200 on the substrate 100. It can be understood that the orthographic projection of the light extraction element 300 on the substrate 100 covers the orthographic projections of the blue light-emitting device 210, the green light-emitting device, and the red light-emitting device on the substrate 100.

[0146] For example, as shown in FIG9B , the light extraction element 300 can be a patterned structure. The orthographic projection of the light extraction element 300 on the base substrate 100 completely overlaps with the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the base substrate 100. Furthermore, the light extraction element 300 exposes the green and red light-emitting devices.

[0147] Nearly all light emitted from the blue light-emitting device 210 enters the light extraction element 300, deflecting the propagation direction of the light emitted from the blue light-emitting device 210 toward a direction nearly perpendicular to the base substrate 100. This increases the amount of light emitted by the blue light-emitting device 210, thereby improving the light extraction efficiency of the entire blue light-emitting device 210. Furthermore, the light extraction element 300 exposes the green and red light-emitting devices, ensuring that the light emitted by these devices is not blocked. This ensures the luminous efficiency of these devices, thereby improving the luminous efficiency of the light-emitting substrate 1000 and the display device 3000.

[0148] FIG. 15 is a comparison diagram between a transmittance curve of a light extraction member and an emission spectrum of a blue light emitting device according to some embodiments.

[0149] In some embodiments, as shown in FIG. 15 , the wavelength λ corresponding to the peak transmittance of the light extraction member 300 is CLC The wavelength λ corresponding to the emission spectrum peak of the blue light emitting device 210 BThe absolute value of the difference is less than or equal to 10 nm, for example, 10 nm, 9 nm, 8 nm, 6 nm, 5 nm, 4 nm, or 3 nm. Limiting the range of the difference between the wavelength corresponding to the peak transmittance of the light extraction element 300 and the wavelength corresponding to the peak emission spectrum of the blue light-emitting device 210 can be understood as bringing the peak transmittance of the light extraction element 300 closer to the peak emission spectrum of the blue light-emitting device 210. This can increase the amount of blue light emitted from the blue light-emitting device 210 that passes through the light extraction element 300, thereby improving the light extraction efficiency of the blue light-emitting device 210.

[0150] In this way, on the basis of improving the light output efficiency of the blue light-emitting device 210, the working load (including driving voltage and / or working current) of the blue light-emitting device 210 can be reduced, thereby extending the service life of the blue light-emitting device 210, and also reducing the probability of the red light-emitting device and / or green light-emitting device adjacent to the blue light-emitting device 210 being lit, thereby improving the color display effect of the light-emitting substrate 1000.

[0151] In some examples, as shown in FIG. 15 , the wavelength λ corresponding to the peak transmittance of the light extraction member 300 is CLC The wavelength λ corresponding to the emission spectrum peak of the blue light emitting device 210 B The absolute value of the difference is less than or equal to 3 nm, for example, 3 nm, 2.5 nm, 2 nm, 1.5 nm, 1 nm, or 0.5 nm. By limiting the difference between the wavelength corresponding to the transmittance peak of the light extraction element 300 and the wavelength corresponding to the emission spectrum peak of the blue light-emitting device 210 to a smaller range, the amount of blue light emitted from the blue light-emitting device 210 that passes through the light extraction element 300 can be maximized, thereby significantly improving the light extraction efficiency of the blue light-emitting device 210.

[0152] In some embodiments, the light extraction element 300 may be a cholesteric liquid crystal (CLC) film layer. Cholesteric liquid crystal films have properties such as optical rotation, selectivity, light scattering, and circular dichroism. Light emitted from the blue light-emitting device 210 enters the cholesteric liquid crystal film layer, which can reflect some of the light emitted by the blue light-emitting device 210 and transmit some of the light. Light reflected by the cholesteric liquid crystal film layer can change its propagation direction after being reflected again by the blue light-emitting device 210. This portion of reflected light will be deflected toward a direction perpendicular to the base substrate 100. Ultimately, this portion of reflected light can also pass through the cholesteric liquid crystal film layer, thereby increasing the amount of light emitted from the blue light-emitting device 210 and thereby improving the light extraction efficiency of the blue light-emitting device 210 in the light-emitting substrate 1000.

[0153] In some embodiments, as shown in FIG3 and FIG9A to FIG9C , the light-emitting substrate 1000 may further include an anti-reflection layer 400. The anti-reflection layer 400 may be provided on the side of the light extraction member 300 away from the base substrate 100. In some examples, the anti-reflection layer 400 may be a polarizer or a filter film. The light emitted from the blue light-emitting layer 21 first passes through the light extraction member 300 and then enters the anti-reflection layer 400. The anti-reflection layer 400 may polarize the light to reduce or even suppress the reflection of the light and enhance the transmission of the light. The light may be further deflected toward a direction perpendicular to the base substrate 100, thereby improving the display effect of the light-emitting substrate 1000.

[0154] Referring to Figures 15 to 19, the present disclosure provides five examples and two comparative examples for comparison. Figures 15 and 19 are graphs comparing the transmittance curves of the light extraction member 300 and the emission spectra of the blue light-emitting device 210 in the five examples and two comparative examples provided herein. Figures 16 to 18 are diagrams illustrating the absorption spectra of the second guest material and the emission spectra of the sensitizer in Examples 2 to 4, respectively.

[0155] Comparative Example 1: The blue light-emitting layer 21 includes a first host material A1 and a first guest material C1, wherein the first guest material C1 is a fluorescent material. The light extraction member 300 is not provided.

[0156] Example 1: The blue light emitting layer 21 includes a first host material A2 and a first guest material C2. The light extraction element 300 uses a CLC film layer D1.

[0157] In Example 1, the triplet energy level of the first host material A2 is 0.15 eV higher than the triplet energy level of the first guest material C2. The first guest material C2 is a platinum metal complex. As shown in FIG15 , the wavelength λ corresponding to the emission spectrum peak of the blue light emitting device 210 is B The wavelength λ corresponding to the peak transmittance of the CLC film is 460nm. CLC The material energy levels of the first host material A2 and the first guest material C2 are shown in Table 1.

[0158] Table 1

[0159] "S1 (eV)" in Table 1 represents the singlet energy level of the first host material A2 and the singlet energy level of the first guest material C2; "T1 (eV)" represents the triplet energy level of the first host material A2 and the triplet energy level of the first guest material C2; "T1 difference (eV)" represents the difference between the triplet energy level of the first host material A2 and the triplet energy level of the first guest material C2.

[0160] Example 2: The blue light-emitting layer 21 includes a second host material A3, a sensitizer B3, and a second guest material C3. The light extraction element 300 uses a CLC film layer D1. The difference between the singlet energy level and the triplet energy level of the sensitizer B3 is 0.22 eV. As shown in Figure 16, the overlapping area between the absorption spectrum of the second guest material C3 and the emission spectrum of the sensitizer B3 accounts for 14.6% of the emission spectrum area of ​​the sensitizer B3. The wavelength corresponding to the peak of the emission spectrum of the blue light-emitting device 210 is 460 nm, and the wavelength corresponding to the peak transmittance of the CLC film layer is 461 nm. The absolute value of the difference between the two is 1 nm. The material energy levels of the sensitizer B3 and the second guest material C3 are detailed in Table 2.

[0161] Table 2

[0162] In Table 2, “S1 (eV)” represents the singlet energy level of the sensitizer B3 and the singlet energy level of the second guest material C3; “T1 (eV)” represents the triplet energy level of the sensitizer B3 and the triplet energy level of the second guest material C3; “ΔE ST (eV)” represents the difference between the singlet energy level of the sensitizer B3 and the triplet energy level of the sensitizer B3, and the difference between the singlet energy level of the second guest material C3 and the triplet energy level of the second guest material C3.

[0163] Comparative Example 2: The structure and material of the blue light-emitting layer 21 are the same as those of the blue light-emitting layer 21 in Example 2, but the light extraction member 300 is not provided.

[0164] Referring to the parameters in the above-mentioned Example 1, Comparative Example 1, Example 2 and Comparative Example 2, the light-emitting substrates 1000 corresponding to Example 1, Comparative Example 1, Example 2 and Comparative Example 2 were subjected to performance tests under the same brightness (e.g., 1000 nit). The test results are detailed in Table 3.

[0165] Table 3

[0166] "Vol." in Table 3 represents the driving voltage of the blue light-emitting device 210; "CE" represents the current luminous efficiency of the blue light-emitting device 210; "Cross-talk" means that when only the blue light-emitting device 210 in the light-emitting substrate 1000 is lit, the other color light-emitting devices adjacent to the blue light-emitting device 210 are lit at the same time by the leakage current, resulting in a deterioration in the display effect of the light-emitting substrate 1000.

[0167] Comparative Example 1 uses a blue fluorescent material, Example 1 uses a blue phosphorescent material, and Example 2 and Comparative Example 2 use a multi-resonance thermally activated delayed fluorescent material. Comparative Examples 1 and 2 do not include a light extraction element 300, while both Examples 1 and 2 use a CLC film.

[0168] Referring to the parameters in Example 1, Comparative Example 1, Example 2, and Comparative Example 2, based on the data in Table 3, it can be seen that, under the same brightness conditions, the driving voltage of the blue light-emitting device 210 in Example 1 and Example 2 is reduced by approximately 15%, the current luminous efficiency is more than doubled, and there is no cross-talk, effectively improving the display effect of the light-emitting substrate 1000. It can be understood that, on the one hand, the light extraction element 300 can increase the light output of the blue light-emitting device 210, thereby improving the light extraction efficiency of the blue light-emitting device 210 in the light-emitting substrate 1000. On the other hand, in the blue phosphorescent material comprising the first host material A2 and the first guest material C2 in the embodiments of the present disclosure, the ratio between the electron mobility of the first host material and the hole mobility of the first host material is limited to a relatively large range, that is, the electron mobility of the first host material is limited to be much greater than the hole mobility of the first host material. This can make the electron transport rate of carriers in the blue light-emitting layer 21 greater than the hole transport rate, and the first host material has good triplet exciton confinement ability, thereby preventing excitons in the blue light-emitting layer 21 from being transmitted to the second electrode (i.e., the cathode), confining the excitons within the blue light-emitting layer 21, while ensuring carrier balance, thereby improving the luminous efficiency of the blue light-emitting layer 21. Based on the improved luminous efficiency, the operating load (including driving voltage and operating current) of the blue light-emitting device 210 can be reduced, thereby extending the service life of the blue light-emitting device 210. It can also reduce the probability of the red light-emitting device and / or green light-emitting device adjacent to the blue light-emitting device 210 being illuminated, thereby improving the color display effect of the light-emitting substrate 1000.

[0169] Example 3: The blue light-emitting layer 21 includes a second host material A3, a sensitizer B3, and a second guest material C4. The light extraction element 300 utilizes a CLC film layer D1. The difference between the singlet energy level of sensitizer B3 and the triplet energy level of sensitizer B3 is 0.22 eV. As shown in Figure 17, the overlapping area between the absorption spectrum of the second guest material C4 and the emission spectrum of sensitizer B3 accounts for 19.3% of the emission spectrum area of ​​sensitizer B3. The wavelength corresponding to the peak emission spectrum of the blue light-emitting device 210 is 460 nm, while the wavelength corresponding to the peak transmittance of the CLC film is 461 nm. The absolute value of the difference between the two is 1 nm.

[0170] Example 4: The blue light-emitting layer 21 includes a second host material A3, a sensitizer B4, and a second guest material C5. The light extraction element 300 utilizes a CLC film layer D1. The difference between the singlet energy level of sensitizer B4 and the triplet energy level of sensitizer B4 is 0.12 eV. As shown in FIG18 , the overlapping area between the absorption spectrum of the second guest material C5 and the emission spectrum of sensitizer B4 accounts for 20.0% of the emission spectrum area of ​​sensitizer B4. The wavelength corresponding to the peak emission spectrum of the blue light-emitting device 210 is 460 nm, and the wavelength corresponding to the peak transmittance of the CLC film is 461 nm. The absolute value of the difference between the two is 1 nm.

[0171] The parameters of Example 2, Example 3 and Example 4 are compared in Table 4.

[0172] Table 4

[0173] The "Sensitizer Energy Level Difference (eV)" in Table 4 represents the difference between the singlet energy level of the sensitizer and the triplet energy level of the sensitizer; the "Overlap Area Ratio" represents the ratio of the overlapping area between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer to the emission spectrum area of ​​the sensitizer.

[0174] Referring to the parameters of Example 2, Example 3 and Example 4 in Table 4 above, performance tests were performed on the light-emitting substrates 1000 corresponding to Example 2, Example 3 and Example 4 respectively under the same brightness (e.g., 1000 nit). The test results are detailed in Table 5.

[0175] Table 5

[0176] “Vol.” in Table 5 represents the driving voltage of the blue light-emitting device 210 ; and “CE” represents the current luminous efficiency of the blue light-emitting device 210 .

[0177] Referring to the parameters in Examples 2, 3, and 4, and based on the data in Tables 4 and 5, it can be seen that, under the same operating conditions, the driving voltage of the blue light-emitting device 210 in Examples 3 and 4 is lower, and the current luminous efficiency is improved, compared to the blue light-emitting device 210 in Example 2. It can be understood that, on the one hand, limiting the difference between the singlet energy level and the triplet energy level of the sensitizer to a smaller range facilitates the conversion of triplet excitons in the sensitizer to singlet excitons via reverse intersystem crossing, improving the exciton utilization rate in the blue light-emitting layer 21 and thereby enhancing the luminous efficiency of the blue light-emitting layer 21. On the other hand, the greater the overlap between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer, the more favorable the transfer of exciton energy from the sensitizer to the second guest material, thereby improving the luminous efficiency of the second guest material and, consequently, the luminous efficiency of the blue light-emitting layer 21. This, in turn, improves the luminous efficiency of the blue light-emitting device 210, and, based on this improved luminous efficiency, allows the driving voltage of the blue light-emitting device 210 to be reduced.

[0178] Example 5: The structure and material of the blue light-emitting layer 21 are the same as those of the blue light-emitting layer 21 in Example 2, and the light extraction element 300 uses a CLC film D2. The emission spectrum peak of the blue light-emitting device 210 corresponds to a wavelength of 460 nm, while the transmittance peak of the CLC film corresponds to a wavelength of 463 nm. The absolute difference between the two values ​​is 3 nm.

[0179] Comparative Example 3: The structure and material of the blue light-emitting layer 21 are the same as those in Example 2, and the light extraction element 300 uses a CLC film D3. The emission spectrum peak of the blue light-emitting device 210 corresponds to a wavelength of 460 nm, while the transmittance peak of the CLC film corresponds to a wavelength of 470 nm. The absolute difference between the two values ​​is 10 nm.

[0180] FIG19 is a comparison diagram between the transmittance curves of each CLC film layer in the above-mentioned Example 2, Example 5 and Comparative Example 3 and the emission spectrum of the blue light-emitting device 210.

[0181] Referring to the parameters in the above-mentioned embodiment 2, embodiment 5 and comparative example 3, the light-emitting substrates 1000 corresponding to embodiment 2, embodiment 5 and comparative example 3 were subjected to performance tests under the same brightness (e.g., 1000 nit). The test results are detailed in Table 6.

[0182] Table 6

[0183] “Vol.” in Table 6 represents the driving voltage of the blue light-emitting device 210 ; and “CE” represents the current luminous efficiency of the blue light-emitting device 210 .

[0184] Referring to the parameters in Examples 2, 5, and Comparative Example 3, based on the data in Table 6, it can be seen that, under the same brightness conditions, the driving voltage of the blue light-emitting device 210 in Examples 2 and 5 is lower, and the current luminous efficiency is improved compared to the blue light-emitting device 210 in Comparative Example 3. It can be understood that the smaller the difference between the wavelength corresponding to the peak transmittance of the light extraction element 300 and the wavelength corresponding to the peak emission spectrum of the blue light-emitting device 210, that is, the closer the peak transmittance of the light extraction element 300 is to the peak emission spectrum of the blue light-emitting device 210, the more blue light emitted from the blue light-emitting device 210 will pass through the light extraction element 300, and the higher the light extraction efficiency of the blue light-emitting device 210. Based on the improved luminous efficiency, the driving voltage of the blue light-emitting device 210 can be reduced.

[0185] In summary, in the light-emitting substrate 1000 and the display device 3000 provided by the embodiment of the present disclosure, the light emitted from the blue light-emitting layer 21 can be transmitted through the second electrode CE and enter the first light enhancement layer 220. Since the refractive index of the first light enhancement layer 220 is relatively large, the amount of light emitted from the blue light-emitting layer 21 can be increased, thereby improving the luminous efficiency and display effect of the light-emitting substrate 1000 and the display device 3000. Secondly, the light transmitted from the first light enhancement layer 220 can enter the second light enhancement layer 230. The light transmitted from the first light enhancement layer 220 can be constrained by the first inorganic layer 24 with a relatively large refractive index, the organic layer 25 with a relatively small refractive index, and the second inorganic layer 26 with a relatively large refractive index in sequence, which can reduce the large refractive index. The effect of blue light on color shift under different viewing angles is reduced, thereby further improving the display quality of the light-emitting substrate 1000 and the display device 3000. Subsequently, light transmitted through the second light-enhancing layer 230 can be emitted outside the display device 300 through the light extraction element 300. By limiting the difference range between the wavelength corresponding to the transmittance peak of the light extraction element 300 and the wavelength corresponding to the emission spectrum peak of the blue light-emitting device 210, the transmittance peak of the light extraction element 300 can be made closer to the emission spectrum peak of the blue light-emitting device 210, thereby increasing the amount of blue light emitted from the blue light-emitting device 210 passing through the light extraction element 300, further improving the luminous efficiency of the light-emitting substrate 1000 and the display device 300. In short, light emitted from the blue light-emitting layer 21 sequentially enters the first light-enhancing layer 220, the second light-enhancing layer 230, and the light extraction element 300, thereby increasing the amount of blue light emitted from the blue light-emitting layer 21 three times, thereby achieving multiple improvements in the luminous efficiency and display quality of the light-emitting substrate 1000 and the display device 300.

[0186] In this way, on the basis of improving the luminous efficiency of the blue light-emitting device 210, the working load of the blue light-emitting device 210 can be reduced, thereby extending the service life of the blue light-emitting device 210, and the probability of the red light-emitting device and / or green light-emitting device adjacent to the blue light-emitting device being lit can also be reduced, thereby improving the color display effect of the light-emitting substrate 1000 and the display device 3000.

[0187] 20 and 21 are flow charts of methods for preparing a light-emitting substrate according to some embodiments.

[0188] As shown in FIG20 , the embodiment of the present disclosure further provides a method for preparing a light-emitting substrate 1000 . The light-emitting substrate 1000 is a top-emitting type light-emitting substrate 1000 . The preparation method may include steps S100 to S300 .

[0189] Step S100: providing a base substrate 100 .

[0190] As shown in Figures 3 and 9A to 9C, in step S100, the substrate 100 may include a first sub-pixel region P1, a second sub-pixel region P2, and a third sub-pixel region P3. The first sub-pixel region P1, the second sub-pixel region P2, and the third sub-pixel region P3 have been described in detail previously and will not be repeated here.

[0191] The substrate 100 may be a rigid substrate or a flexible substrate. For example, the substrate 100 may be made of polyethylene terephthalate (PET), polyimide (PI), cycloolefin polymer (COP), or the like.

[0192] Step S100 may include: forming a pixel circuit layer on the base substrate 100. The pixel circuit layer includes a plurality of pixel circuits. As shown in Figures 9A to 9C, in a pixel unit area PU, the plurality of pixel circuits may include a first pixel circuit S1, a second pixel circuit S2, and a third pixel circuit S3. For example, the first pixel circuit S1 is located in the first sub-pixel area P1, the second pixel circuit S2 is located in the second sub-pixel area P2, and the third pixel circuit S3 is located in the third sub-pixel area P3. Among them, the first pixel circuit S1 is configured to drive the blue light-emitting device 210, the second pixel circuit S2 is configured to drive the green light-emitting device, and the third pixel circuit S3 is configured to drive the red light-emitting device. The specific introduction of the plurality of pixel circuits has been described in detail before and will not be repeated here.

[0193] After forming the plurality of pixel circuits, an insulating layer INL covering the plurality of pixel circuits may be formed.

[0194] The insulating layer INL may be located on the first pixel circuit S1, the second pixel circuit S2, and the third pixel circuit S3. The insulating layer INL may have a planarized surface. The insulating layer INL may be formed by coating an organic layer. For example, the material of the insulating layer INL may include an acrylic resin, an epoxy resin, an imide resin, or an ester resin. The insulating layer INL may have a through hole for exposing the electrodes of the first pixel circuit S1, the second pixel circuit S2, and the third pixel circuit S3 to achieve electrical connection.

[0195] Step S200: Forming a light-emitting unit 200 on one side of a base substrate 100. The light-emitting unit 200 includes at least one blue light-emitting device 210. The blue light-emitting device 210 includes a first electrode AE, at least one blue light-emitting layer 21, and a second electrode CE, stacked in sequence along a direction away from the base substrate 100. The light-emitting unit 200 also includes a first light-enhancing layer 220 and a second light-enhancing layer 230 located on a side of the blue light-emitting device 210 away from the base substrate 100, with the first light-enhancing layer 220 located between the blue light-emitting device 210 and the second light-enhancing layer 230. The second light-enhancing layer 230 includes a first inorganic layer 24, an organic layer 25, and a second inorganic layer 26, stacked in sequence along a direction away from the base substrate 100. The refractive index of the organic layer 25 is lower than that of the first inorganic layer 24 and lower than that of the second inorganic layer 26.

[0196] As shown in FIG. 21 , step S200 may specifically include steps S201 to S206 .

[0197] Step S201 : forming a first electrode AE ​​on one side of the base substrate 100 .

[0198] The first electrode AE ​​may be an anode. As shown in FIG3 , the anode may include a first anode AE1, a second anode AE2, and a third anode AE3. The first anode AE1 is located in the first sub-pixel region P1, the second anode AE2 is located in the second sub-pixel region P2, and the third anode AE3 is located in the third sub-pixel region P3.

[0199] In some examples, the first electrode AE ​​can be formed on the insulating layer INL through a single patterning process. For example, a first anode AE1 located in the first sub-pixel region P1, a second anode AE2 located in the second sub-pixel region P2, and a third anode AE3 located in the third sub-pixel region P3 can be formed in a single process by evaporating an anode material on the insulating layer INL using a mask, and then performing exposure, development, and etching using the mask.

[0200] The anode material can be a metal such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, or Cr, or a mixture thereof, or a conductive metal oxide material such as ITO, IZO, or IGZO. For example, the anode can include a laminated composite structure of transparent conductive oxide / metal / transparent conductive oxide. Examples of the transparent conductive oxide material include ITO or IZO, and examples of the metal material include Au, Ag, Ni, or Pt. For example, the anode structure is: ITO / Ag / ITO.

[0201] Step S202 : forming a pixel defining layer PDL on a side of the first electrode AE ​​away from the base substrate 100 , wherein the pixel defining layer PDL is provided with a plurality of light emitting openings, and the light emitting openings expose the first electrode AE.

[0202] As shown in Figures 9A to 9C , a pixel-defining layer (PDL) can be formed on the insulating layer INL and the first electrode AE. For example, a deposition process is used to form a pixel-defining material layer covering the insulating layer and the anode AE, and an etching process is used to remove a portion of the pixel-defining material layer to obtain the pixel-defining layer (PDL). The pixel-defining layer (PDL) includes a first light-emitting opening K1 located in the first sub-pixel region P1, a second light-emitting opening K2 located in the second sub-pixel region P2, and a third light-emitting opening K3 located in the third sub-pixel region P3. The first light-emitting opening K1 exposes the first anode AE1, the second light-emitting opening K2 exposes the second anode AE2, and the third light-emitting opening K3 exposes the third anode AE3.

[0203] Step S203: forming at least one blue light-emitting layer 21 covering the light-emitting opening.

[0204] For example, in step S203, a fine metal mask (FMM) can be used to form a blue light-emitting layer 21 covering the first light-emitting opening K1 at the first light-emitting opening K1. The number of blue light-emitting layers 21 can be one or more. For example, in step S203, a fine metal mask can be used to form two or three blue light-emitting layers 21 covering the same first light-emitting opening K1 and stacked in sequence along a direction perpendicular to the base substrate 100 at the first light-emitting opening K1.

[0205] In some examples, the blue light-emitting layer 21 may be made of a blue phosphorescent material. The blue light-emitting layer 21 may include a first host material and a first guest material.

[0206] In the blue light-emitting layer 21 , a ratio of the electron mobility of the first host material to the hole mobility of the first host material is greater than or equal to 80, for example, 80, 82, 86, 90, 92, 95, 98, 100, 110 or 120.

[0207] Limiting the ratio between the electron mobility of the first main material and the hole mobility of the first main material within a larger range, that is, limiting the electron mobility of the first main material to be much greater than the hole mobility of the first main material, can make the electron transfer rate of carriers in the blue light-emitting layer 21 greater than the hole transfer rate, so that the first main material has good triplet exciton confinement ability, so as to block the excitons in the blue light-emitting layer 21 from being transmitted to the second electrode CE (i.e., the cathode), confine the excitons within the blue light-emitting layer 21, and at the same time ensure carrier balance, thereby improving the luminous efficiency of the blue light-emitting layer 21.

[0208] Illustratively, the first guest material may be a metal complex comprising any one of iridium, platinum, palladium, or cerium metal elements and at least two nitrogen heterocyclic carbene ligands. For example, the first guest material may be a metal complex comprising iridium metal element and two nitrogen heterocyclic carbene ligands. For another example, the first guest material may be a metal complex comprising platinum metal element and two nitrogen heterocyclic carbene ligands.

[0209] Illustratively, the triplet energy level of the first host material is greater than the triplet energy level of the first guest material, wherein the difference between the triplet energy levels of the first host material and the first guest material is greater than or equal to 0.1 eV, such as 0.1 eV, 0.2 eV, 0.3 eV, 0.5 eV, 0.8 eV, or 1 eV.

[0210] For example, in step S203 , the first host material and the first guest material may be evaporated by a heating device (eg, a crucible), and a high-precision metal mask may be used to form the blue light-emitting layer 21 at the light-emitting opening.

[0211] In other examples, the blue light-emitting layer 21 may use a blue superfluorescent light-emitting material, and the blue light-emitting layer 21 may include a second host material, a sensitizer, and a second guest material.

[0212] In the blue light-emitting layer 21 , a ratio between the electron mobility of the second host material and the hole mobility of the second host material is less than or equal to 0.2, for example, 0.05, 0.1, 0.15 or 0.2.

[0213] By limiting the ratio between the electron mobility of the second main material and the hole mobility of the second main material to a smaller range, the electron transport performance and the hole transport performance in the blue light-emitting layer 21 can be improved, and the electrons and holes in the blue light-emitting layer 21 can be evenly distributed to ensure carrier balance, thereby improving the utilization rate of electrons and holes in the blue light-emitting layer 21, and further improving the luminous efficiency of the blue light-emitting layer 21.

[0214] The sensitizer may be a thermally activated delayed fluorescent material having luminescent properties. For example, the sensitizer may contain at least one carbazole group and at least one cyano group. For example, the sensitizer may include two carbazole groups and one cyano group. For another example, the sensitizer may include four carbazole groups and one cyano group. The ratio between the electron mobility of the sensitizer and the hole mobility of the sensitizer is greater than or equal to 8, for example, 8, 10, 12, 15 or 20. The absolute value of the difference between the singlet energy level of the sensitizer and the triplet energy level of the sensitizer is less than or equal to 0.5 eV, for example, 0.1 eV, 0.2 eV, 0.3 eV, 0.4 eV or 0.5 eV.

[0215] As shown in FIG14 , the overlapping area S between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer accounts for greater than or equal to 8% of the emission spectrum area A of the sensitizer, for example, 8%, 10%, 15%, 20%, 30% or 50%.

[0216] For example, in step S203 , the second host material, the sensitizer, and the second guest material may be evaporated by a heating device (eg, a crucible), and a high-precision metal mask may be used to form the blue light-emitting layer 21 at the light-emitting opening.

[0217] Step S204 : forming a second electrode CE on a side of the at least one blue light emitting layer 21 away from the first electrode AE.

[0218] As shown in FIG3 , the second electrode CE may cover the first light emitting opening K1 , the second light emitting opening K2 , the third light emitting opening K3 and the pixel defining layer PDL, and the portion covering the pixel defining layer PDL and the portion covering the light emitting openings form a continuous film.

[0219] The second electrode CE may be a cathode. In some examples, the second electrode CE may be formed by evaporating a cathode material on a side of the at least one blue light-emitting layer 21 away from the first electrode AE. The cathode material may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, or compounds or mixtures thereof, such as a mixture of Ag and Mg.

[0220] Step S205 : forming a first light enhancement layer 220 on a side of the second electrode CE away from the base substrate 100 .

[0221] The first light enhancement layer 220 may also be referred to as a light extraction layer (CPL) or a light coupling layer. For example, as shown in FIG3 , the first light enhancement layer 220 may be located on a surface of the second electrode CE distal from the blue light-emitting layer 21. This may be understood as the first light enhancement layer 220 directly contacting the surface of the second electrode CE distal from the blue light-emitting layer 21. For example, step S205 may include forming the first light enhancement layer 220 by evaporating a first light enhancement layer material on the surface of the second electrode CE distal from the blue light-emitting layer 21.

[0222] For example, the material of the first light enhancement layer may be an organic material, and the refractive index of the first light enhancement layer 220 may be greater than or equal to 1.8, such as 1.8, 1.9 or 2.0.

[0223] Since the refractive index of the first light enhancement layer 220 is relatively large, the light subsequently emitted from the blue light-emitting layer 21 is refracted through the first light enhancement layer 220, and the refraction angle of the light is smaller than the incident angle, so that the propagation direction of the light emitted from the blue light-emitting layer 21 can be deflected toward a direction close to perpendicular to the base substrate 100, thereby increasing the amount of light emitted from the blue light-emitting layer 21, thereby improving the light extraction efficiency and display effect of the light-emitting substrate 1000 and the display device 3000.

[0224] Step S206 : forming a second light enhancement layer 230 on a side of the first light enhancement layer 220 away from the second electrode CE.

[0225] In some examples, as shown in Figures 9A to 9C, step S206 may include forming a first inorganic layer 24 on a side of the first light enhancement layer 220 away from the second electrode CE by chemical vapor deposition. After forming the first inorganic layer 24, an organic layer 25 is formed on a side of the first inorganic layer 24 away from the second electrode CE by inkjet printing, wherein the organic layer 25 may have a flat surface. After forming the organic layer 25, a second inorganic layer 26 may be formed on the flat surface of the organic layer 25 by chemical vapor deposition.

[0226] In some examples, the second light enhancement layer 230 can have the property of isolating water and oxygen, and the second light enhancement layer 230 can also be configured to encapsulate the light-emitting device in the light-emitting unit 200 and the first light enhancement layer 220. As shown in Figures 9A to 9C, the material of the first inorganic layer 24 and the second inorganic layer 26 in the second light enhancement layer 230 can be selected from at least one of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, silicon oxynitride, or lithium fluoride. The material of the organic layer 25 can be at least one of acrylic resin, methacrylic resin, polyisoprene, vinyl resin, epoxy resin, polyurethane resin, cellulose resin, or perylene resin. Those skilled in the art can change the number of layers, materials, and structures of the thin film encapsulation layer as needed, and the present disclosure is not limited thereto.

[0227] The light emitted from the blue light-emitting layer 21 is constrained in sequence by the first inorganic layer 24 with a larger refractive index, the organic layer 25 with a smaller refractive index, and the second inorganic layer 26 with a larger refractive index, which can reduce the influence of blue light on the color shift phenomenon under a large viewing angle, thereby improving the display effect of the light-emitting substrate 1000.

[0228] 9A and 9B , the second light enhancement layer 230 may further include a third inorganic layer 27. The third inorganic layer 27 may be disposed between the first light enhancement layer 220 and the first inorganic layer 24. The refractive index of the third inorganic layer 27 is less than that of the first light enhancement layer 220 and less than that of the first inorganic layer 24.

[0229] For example, the refractive index of the first light enhancement layer 220 may be greater than or equal to 1.8 (e.g., 1.8, 1.9, or 2.0), the refractive index of the third inorganic layer 27 may be less than or equal to 1.5 (e.g., 1.3, 1.4, or 1.5), and the refractive index of the first inorganic layer 24 may also be greater than or equal to 1.8 (e.g., 1.8, 1.9, or 2.0).

[0230] For example, step S206 may further include forming a third inorganic layer 27 by chemical vapor deposition on a side of the first light enhancement layer 220 away from the second electrode CE. After forming the third inorganic layer 27, the first inorganic layer 24, the organic layer 25, and the second inorganic layer 26 are sequentially formed according to the method described in the above example, which will not be further described here.

[0231] The light emitted from the blue light-emitting layer 21 is constrained in turn by the first light enhancement layer 220 with a larger refractive index, the third inorganic layer 27 with a smaller refractive index, and the first inorganic layer 24 with a larger refractive index, which can reduce the influence of blue light on the color shift phenomenon under a large viewing angle, thereby improving the display effect of the light-emitting substrate 1000 and the display device.

[0232] Step S300 : forming a light extraction member 300 on a side of the second light enhancement layer 230 away from the base substrate 100 .

[0233] The orthographic projection of the light extraction element 300 on the base substrate 100 at least partially overlaps with the orthographic projection of the blue light emitting device 210 on the base substrate 100 .

[0234] For example, in step S300 , the light extraction member 300 may be bonded to the surface of the second light enhancement layer 230 away from the base substrate 100 by using an optically transparent adhesive.

[0235] As shown in FIG. 9A to FIG. 9C , the blue light emitting device 210 covers the first light emitting opening K1 , the green light emitting device covers the second light emitting opening K2 , and the red light emitting device covers the third light emitting opening K3 .

[0236] In some examples, as shown in FIG9A , the light extraction member 300 may be a patterned structure, and the orthographic projection of the light extraction member 300 on the base substrate 100 may only cover a portion of the orthographic projection of the light emitting portion of the blue light emitting device 210 on the base substrate 100. Furthermore, the light extraction member 300 exposes the green and red light emitting devices.

[0237] In step S300, the light extraction member 300 can be adhered to the surface of the second inorganic layer 26 away from the base substrate 100 using optically transparent adhesive only in the area corresponding to the first light-emitting opening K1, forming a light extraction member 300 that only covers the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the base substrate 100. The remaining portions of the light-emitting substrate 1000 (including the areas corresponding to the second light-emitting opening K2 and the third light-emitting opening K3) on the same layer as the patterned light extraction member 300 can be made flat by filling them with optically transparent adhesive to facilitate the fabrication of components in subsequent processes.

[0238] In some examples, as shown in FIG9B , the light extraction member 300 may be a patterned structure, and the orthographic projection of the light extraction member 300 on the base substrate 100 may completely overlap with the orthographic projection of the light emitting portion of the blue light emitting device 210 on the base substrate 100. Furthermore, the light extraction member 300 exposes the green and red light emitting devices.

[0239] In step S300, the light extraction member 300 can be bonded to the surface of the second inorganic layer 26 away from the base substrate 100 at a position directly corresponding to the blue light-emitting device 210 using optically transparent adhesive. This forms a light extraction member 300 that completely covers the orthographic projection of the light-emitting portion of the blue light-emitting device 210 on the base substrate 100. Other portions of the light-emitting substrate 1000 that are on the same layer as the patterned light extraction member 300 (including the area corresponding to the second light-emitting opening K2 and the area corresponding to the third light-emitting opening K3) can be made flat by filling them with optically transparent adhesive to facilitate the fabrication of components in subsequent processes.

[0240] In some examples, as shown in FIG9C , the light extraction member 300 may be a whole-layer structure, and the orthographic projection of the light extraction member 300 on the substrate 100 may cover the orthographic projection of the blue light-emitting device 210 on the substrate 100, the orthographic projection of the green light-emitting device on the substrate 100, and the orthographic projection of the red light-emitting device on the substrate 100, and may also cover the thin film connecting the blue light-emitting device 210, the green light-emitting device, and the red light-emitting device.

[0241] In step S300 , the entire light extraction member 300 may be directly bonded to the surface of the second inorganic layer 26 away from the base substrate 100 by using an optically transparent adhesive.

[0242] The light emitted from the blue light-emitting device 210 can enter the light extraction element 300, so that the propagation direction of the light emitted from the blue light-emitting device 210 is deflected toward a direction close to perpendicular to the base substrate 100, thereby improving the light extraction efficiency of the partial area of ​​the blue light-emitting device 210 corresponding to the light extraction element 300.

[0243] The absolute value of the difference between the wavelength corresponding to the peak transmittance of the light extraction element 300 and the wavelength corresponding to the peak emission spectrum of the blue light-emitting device 210 is less than or equal to 10 nm, such as 10 nm, 9 nm, 8 nm, 6 nm, 5 nm, 4 nm, or 3 nm. Limiting the range of the difference between the wavelength corresponding to the peak transmittance of the light extraction element 300 and the wavelength corresponding to the peak emission spectrum of the blue light-emitting device 210 can be understood as bringing the peak transmittance of the light extraction element 300 closer to the peak emission spectrum of the blue light-emitting device 210. This can increase the amount of blue light emitted from the blue light-emitting device 210 that passes through the light extraction element 300, thereby improving the light extraction efficiency of the blue light-emitting device 210.

[0244] In some examples, the light extraction member 300 may be a cholesteric liquid crystal film layer.

[0245] In some examples, as shown in FIG3 and FIG9A to FIG9C , after step S300, an anti-reflection layer 400 may be formed on the side of the light extraction member 300 away from the second light enhancement layer 230. For example, the anti-reflection layer 400 may be a polarizer or a filter film, which may be adhered to the side of the light extraction member 300 away from the second light enhancement layer 230 using optically transparent adhesive. Light emitted from the blue light-emitting layer 21 first passes through the light extraction member 300 before entering the anti-reflection layer 400. The anti-reflection layer 400 can polarize the light to reduce or even suppress light reflection and enhance light transmission. The light can be further deflected toward a direction perpendicular to the base substrate 100, thereby improving the display effect of the light-emitting substrate 1000.

[0246] Since the light-emitting substrate and display device provided by the embodiments of the present disclosure have been previously described in detail as having the beneficial effects of high overall luminous efficiency, low workload, long effective service life, and excellent display effects, the light-emitting substrate and display device prepared by the method for preparing the light-emitting substrate provided by the embodiments of the present disclosure can also achieve the beneficial effects of the light-emitting substrate and display device described above, and no further details will be given here.

[0247] The above are only specific embodiments of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that a person skilled in the art can conceive within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A light-emitting substrate, which is a top-emitting light-emitting substrate, comprising: substrate substrate; A light emitting unit is located on one side of the substrate; The light emitting unit comprises: At least one blue light emitting device; the blue light emitting device comprises a first electrode, at least one blue light emitting layer and a second electrode stacked in sequence in a direction away from the base substrate; a first light enhancement layer and a second light enhancement layer located on a side of the blue light emitting device away from the substrate, wherein the first light enhancement layer is located between the blue light emitting device and the second light enhancement layer; the second light enhancement layer comprises a first inorganic layer, an organic layer, and a second inorganic layer stacked in sequence along a direction in which the first light enhancement layer is away from the substrate, wherein the refractive index of the organic layer is less than the refractive index of the first inorganic layer and less than the refractive index of the second inorganic layer; A light extraction member is located on a side of the second light enhancement layer away from the base substrate; an orthographic projection of the light extraction member on the base substrate at least partially overlaps with an orthographic projection of the blue light emitting device on the base substrate; The absolute value of the difference between the wavelength corresponding to the peak transmittance of the light extraction element and the wavelength corresponding to the peak emission spectrum of the blue light emitting device is less than or equal to 10 nm.

2. The light-emitting substrate according to claim 1, wherein: The absolute value of the difference between the wavelength corresponding to the transmittance peak of the light extraction member and the wavelength corresponding to the emission spectrum peak of the blue light emitting device is less than or equal to 3 nm.

3. The light-emitting substrate according to claim 1 or 2, wherein: The orthographic projection of the light extraction member on the base substrate covers the orthographic projection of the light emitting portion of the blue light emitting device on the base substrate.

4. The light-emitting substrate according to any one of claims 1 to 3, wherein The light extraction member is a cholesteric liquid crystal film layer.

5. The light emitting substrate according to any one of claims 1 to 4, wherein The second light enhancement layer further includes a third inorganic layer; the third inorganic layer is disposed between the first light enhancement layer and the first inorganic layer; and the refractive index of the third inorganic layer is smaller than the refractive index of the first light enhancement layer and smaller than the refractive index of the first inorganic layer.

6. The light emitting substrate according to any one of claims 1 to 5, wherein The blue light-emitting layer includes a first host material and a first guest material; In the blue light-emitting layer, a ratio between the electron mobility of the first host material and the hole mobility of the first host material is greater than or equal to 80.

7. The light-emitting substrate according to claim 6, wherein: The first guest material is a metal complex including any one of iridium, platinum, palladium or cerium metal elements and at least two nitrogen heterocyclic carbene ligands.

8. The light-emitting substrate according to claim 6 or 7, wherein: In the blue light-emitting layer, the triplet energy level of the first host material is greater than the triplet energy level of the first guest material.

9. The light emitting substrate according to any one of claims 1 to 5, wherein The blue light-emitting layer includes a second host material, a sensitizer and a second guest material; In the blue light-emitting layer, the electron mobility of the second host material is equal to the hole mobility of the second host material. The ratio between the rates is less than or equal to 0.

2.

10. The light emitting substrate according to claim 9, wherein: The ratio of the electron mobility of the sensitizer to the hole mobility of the sensitizer is greater than or equal to 8.

11. The light-emitting substrate according to claim 9 or 10, wherein: An absolute value of a difference between a singlet energy level of the sensitizer and a triplet energy level of the sensitizer is less than or equal to 0.5 eV.

12. The light emitting substrate according to any one of claims 9 to 11, wherein The weight of the sensitizer accounts for a ratio of the sum of the weight of the second host material and the weight of the sensitizer that is less than or equal to 30%.

13. The light emitting substrate according to any one of claims 9 to 12, wherein The ratio of the weight of the second guest material to the sum of the weight of the second host material and the weight of the sensitizer is less than or equal to 5%.

14. The light emitting substrate according to any one of claims 9 to 13, wherein The ratio of the overlapping area between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer to the emission spectrum area of ​​the sensitizer is greater than or equal to 8%.

15. The light emitting substrate according to any one of claims 9 to 14, wherein The ratio of the overlapping area between the absorption spectrum of the second guest material and the emission spectrum of the sensitizer to the emission spectrum area of ​​the sensitizer is less than or equal to 80%.

16. The light emitting substrate according to any one of claims 9 to 15, wherein The second guest material is selected from any one of the structures shown in the following general formula: Wherein, the substituents R1 to R18 are the same or different, and are independently selected from any one of hydrogen, alkyl, aryl or heteroaryl; adjacent substituents R1 to R18 may form a condensed ring or not.

17. The light emitting substrate according to any one of claims 1 to 16, wherein The wavelength corresponding to the peak value of the emission spectrum of the blue light-emitting device is within the range of 440nm to 480nm, and the full width at half maximum of the emission spectrum of the blue light-emitting device is less than or equal to 50nm.

18. The light-emitting substrate according to any one of claims 1 to 17, further comprising an anti-reflection layer; the anti-reflection layer is arranged on a side of the light extraction member away from the base substrate.

19. A method for preparing a light-emitting substrate, wherein the light-emitting substrate is a top-emitting light-emitting substrate, the method comprising: providing a substrate base plate; forming a light emitting unit on one side of the base substrate; The light emitting unit comprises at least one blue light emitting device; The blue light-emitting device comprises a first electrode, at least one blue light-emitting layer, and a second electrode which are sequentially stacked in a direction away from the base substrate; the light-emitting unit further comprises a first light enhancement layer and a second light enhancement layer which are located on a side of the blue light-emitting device away from the base substrate, wherein the first light enhancement layer is located between the blue light-emitting device and the second light enhancement layer; the second light enhancement layer comprises a first inorganic layer, an organic layer, and a second inorganic layer which are sequentially stacked in a direction of the first light enhancement layer away from the base substrate, wherein the refractive index of the organic layer is less than the refractive index of the first inorganic layer and less than the refractive index of the second inorganic layer; A light extraction member is formed on a side of the second light enhancement layer away from the base substrate; an orthographic projection of the light extraction member on the base substrate at least partially overlaps with an orthographic projection of the blue light emitting device on the base substrate; The absolute value of the difference between the wavelength corresponding to the transmittance peak of the light extraction member and the wavelength corresponding to the emission spectrum peak of the blue light emitting device is less than or equal to 10 nm.

20. A display device, comprising: Circuit boards; The light-emitting substrate according to any one of claims 1 to 18, wherein the light-emitting substrate is coupled to the circuit board.

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