Light emitting device and display apparatus

Abstract

The application provides a light-emitting device and a display device. The light-emitting device comprises a light-emitting layer, wherein the light-emitting layer comprises a first light-emitting sublayer and a second light-emitting sublayer arranged in a stack; the first light-emitting sublayer comprises a first host material and a first guest material, wherein the first host material is a blue fluorescent host material with triplet-triplet annihilation properties; and the second light-emitting sublayer comprises a second host material, a phosphorescent sensitizer and a second guest material, wherein the second host material is a blue phosphorescent host material. The application combines the fluorescent technology and the phosphorescent sensitized fluorescent technology, improves the utilization rate of excitons, improves the efficiency of blue light emission, and improves the low lifetime of phosphorescence.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a light-emitting device and a display apparatus. Background Technology

[0002] With the increasing popularity and technological upgrades of OLED (Organic Light Emitting Device), users have a stronger demand for improved power consumption. However, existing OLED blue light technology is limited by its triplet-triplet annihilation (TTA) light emission mechanism, which cannot fully utilize the energy of triplet excitons, making it very difficult to significantly improve device efficiency. Emerging technologies such as blue phosphorescence technology are limited by the progress of material development and cannot reach mass production levels in the short term, and their lifespan is very poor. Summary of the Invention

[0003] In view of the above problems, the present invention provides a light-emitting device and a display device to solve the problems of low luminous efficiency and short lifespan of existing blue light-emitting devices.

[0004] To achieve the above objectives, the present invention provides a light-emitting device, which includes a light-emitting layer, the light-emitting layer including a first light-emitting sublayer and a second light-emitting sublayer stacked thereon; the first light-emitting sublayer includes a first host material and a first guest material, the first host material being a blue fluorescent host material having triplet-triplet annihilation properties; the second light-emitting sublayer includes a second host material, a phosphorescent photosensitizer and a second guest material, the second host material being a blue phosphorescent host material.

[0005] Furthermore, the first guest material is a blue fluorescent guest material and the mass fraction of the first guest material in the first photonic layer is in the range of 0.5wt%-10wt%.

[0006] Furthermore, the first host material includes anthracene or pyrene materials, and the first guest material includes boron-nitrogen materials;

[0007] Preferably, the first main material includes , , , , Any one of them; the first object material includes , , , Any one of them.

[0008] Furthermore, the phosphorescent photosensitizer is a blue phosphorescent photosensitizer and the mass fraction of the phosphorescent photosensitizer in the second photonic layer is in the range of 5wt%-25wt%; the second guest material is a blue fluorescent guest material and the mass fraction of the second guest material in the second photonic layer is in the range of 0.5wt%-5wt%.

[0009] Furthermore, the second host material includes triarylsilane materials, the phosphorus photosensitizer includes platinum complexes, and the second guest material includes boron-nitrogen materials; preferably, the phosphorus photosensitizer includes , , , Any one of them; the second object material includes , , , Any one of them.

[0010] Furthermore, the second host material is an electronic host material or a hole host material, or a dual host material that simultaneously contains both electronic and hole host materials; preferably, the electronic host material includes , , , Any one of the following; cavity-type main body materials include , , , Any one of them.

[0011] Furthermore, the thickness of the first luminescent layer is in the range of 5nm-20nm, and the thickness of the second luminescent layer is in the range of 20nm-50nm; preferably, the difference between the main peaks of the emission spectra of the first guest material and the second guest material is less than 2nm, and the difference between the full width at half maximum (FWHM) is less than 3nm; or, the first guest material and the second guest material are the same; preferably, the light-emitting device further includes an electron blocking layer and a hole blocking layer, with the luminescent layer located between the electron blocking layer and the hole blocking layer.

[0012] Furthermore, the first photonic layer is close to the electron blocking layer, and the second photonic layer is close to the hole blocking layer; preferably, the difference between the highest occupied orbital energy level of the first host material and the highest occupied orbital energy level of the electron blocking layer is less than 0.3 eV, and the difference between the lowest unoccupied orbital energy level of the second host material and the lowest unoccupied orbital energy level of the hole blocking layer is less than 0.3 eV.

[0013] Furthermore, the first photonic layer is close to the hole blocking layer, and the second photonic layer is close to the electron blocking layer; preferably, the difference between the lowest unoccupied orbital energy level of the first host material and the lowest unoccupied orbital energy level of the hole blocking layer is less than 0.3 eV, and the difference between the highest occupied orbital energy level of the second host material and the highest occupied orbital energy level of the electron blocking layer is less than 0.3 eV.

[0014] The present invention also provides a display device, characterized in that it includes the above-described light-emitting device.

[0015] The beneficial effects of this invention are as follows: By employing a double-layer light-emitting structure in the blue light device, one light-emitting layer uses a blue fluorescent host material and a fluorescent guest material, while the other light-emitting layer uses a blue phosphorescent host material, a blue phosphorescent sensitizer, and a fluorescent guest material. This allows singlet excitons generated by carrier recombination to emit light directly, while triplet excitons can be converted into singlet excitons through the TTA mechanism or the phosphorescent sensitizer. Compared to traditional blue fluorescence technology, this results in higher exciton utilization. Furthermore, due to the presence of the double light-emitting layer, excitons are separated to a certain extent, which can reduce the quenching of excitons and polarons and improve the lifetime degradation caused by phosphorescence technology. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram illustrating the mechanism of blue fluorescent TTA luminescence in related technologies; Figure 2 This is a schematic diagram of the luminescence mechanism of the dual fluorescent luminescent layer in related technologies; Figure 3 This is a schematic diagram illustrating the light-emitting principle of a light-emitting device according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a light-emitting device provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of another light-emitting device provided in an embodiment of the present invention; Marker explanation: 101-First electrode; 102-Hole injection layer; 103-Hole transport layer; 104-Electron blocking layer; 105-Emitting layer; 1051-First luminescent sublayer; 1051a-First host material; 1051b-First guest material; 1052-Second luminescent sublayer; 1052a-Second host material; 1052b-Second guest material; 1052c-Phosphorus photosensitizer; 106-Hole blocking layer; 107-Electron transport layer; 108-Electron injection layer; 109-Second electrode; Detailed Implementation The accompanying drawings illustrate preferred embodiments of the present invention, demonstrating its implementability. These embodiments provide a complete overview of the invention to those skilled in the art, making its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and its scope of protection is not limited to the embodiments mentioned herein.

[0018] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of components is appropriately exaggerated in some places in the drawings.

[0019] Furthermore, the following descriptions of the embodiments of the invention are made with reference to the accompanying illustrations, illustrating specific embodiments in which the invention can be implemented. Directional terms used in this invention, such as "upper," "lower," "front," "rear," "left," "right," "inner," "outer," and "side," are merely directional references to the accompanying drawings. Therefore, the use of directional terms is for better and clearer explanation and understanding of the invention, and does not indicate or imply that the referred device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] When a component is described as being "on" another component, the component may be placed directly on the other component; alternatively, there may be an intermediate component on which the component is placed, and the intermediate component is placed on the other component. When a component is described as being "installed to" or "connected to" another component, both can be understood as being directly "installed" or "connected" to, or as being indirectly "installed to" or "connected to" another component via an intermediate component.

[0021] In related OLED blue light technology, because its light emission mechanism is TTA (Triplet-Triplet Annihilation), it is impossible to fully utilize the ability of triplet excitons, thus failing to effectively improve the light emission efficiency. Blue phosphorescence technology is also limited by the progress of material development and cannot reach the level of mass production in the short term, and its own lifespan is also relatively poor.

[0022] like Figure 1 The diagram illustrates the mechanism of blue fluorescent TTA luminescence, which is also the luminescence mechanism of blue light devices in existing mass-produced OLED products. The TTA luminescence process is as follows: under electrical excitation, electrons and holes recombine in the TTA host layer to form excited excitons, of which 25% are singlet excitons (S1) and 75% are triplet excitons (T1). The TTA host S1 exciton formed by electrical injection transfers energy to the fluorescent guest S1 via Förster resonance energy transfer. When the guest S1 de-excites, it emits transient fluorescence, and at the same time, some of its S1 excitons are converted into low-energy fluorescent guest T1 via intersystem crossing (ISC). Subsequently, due to the triplet energy level matching between the two, the guest T1 transfers energy back to the TTA host T1 through the Dexter electron exchange mechanism, allowing long-lived dark-state excitons to accumulate on the host. When the two TTA host T1 excitons collide and annihilate, a high-energy TTA host S1 is formed through a triplet-triplet annihilation mechanism (the other exciton radiatively transitions back to the ground state). The newly formed host S1 does not emit light directly, but repeats the first step again—transferring energy to the fluorescent guest S1 a second time, driving the guest to emit delayed fluorescence, thus completing a relatively closed energy cycle. Ultimately, the fluorescent guest emits not only nanosecond-level transient fluorescence, but also microsecond- to millisecond-level TTA delayed fluorescence. However, this TTA luminescence also has drawbacks, namely its maximum internal quantum efficiency (IQE) is about 62.5%. In contrast, phosphorescent OLEDs and TADF (thermally activated delayed fluorescence) OLEDs can reach 100%, and their efficiency drops sharply under high current and high brightness conditions.

[0023] Current technologies employ a dual-layer blue light-emitting scheme. This involves generating excitons through carrier recombination in one layer, then transferring these excitons to the other layer for emission. By separating the exciton generation and emission sites, the quenching of excitons and polarons is reduced, thus achieving higher exciton utilization. For example... Figure 2The diagram illustrates the luminescence mechanism of the double-layer blue light-emitting layer. The specific luminescence process is as follows: After electrical excitation, holes and electrons recombine simultaneously in EML1 and EML2, generating 25% singlet S1 excitons and 75% triplet T1 excitons, respectively. In EML1, the host (BH1 in the diagram) S1 transfers energy to the blue fluorescent guest (BD1 in the diagram) S1 via Förster resonance energy transfer (FRET), causing the guest to emit transient fluorescence through radiative transition. Due to the close contact between the two layers, some of the T1 excitons in the host within EML1 undergo nonradiative transitions (generating heat) within the host, while the other part transfers energy to the adjacent TTA host (BH2 in the diagram) in EML2 via Dexter transfer, causing the TTA host to enter the T1 state. At this point, a large number of long-lived T1 excitons accumulate within the host in EML2. In EML2, this layer simultaneously receives T1 excitons transferred from EML1 and T1 excitons generated by its own recombination. When the T1 excitons of two TTA hosts collide, triplet-triplet annihilation occurs, upconverting to a high-energy TTA host S1. Subsequently, this newly formed S1 transfers energy to the blue fluorescent guest (BD2 in the figure) S1 in EML2 via FRET, driving its radiative transition and emitting TTA delayed fluorescence. This design dilutes the local exciton density in a single luminescent layer, thereby significantly suppressing the efficiency roll-off caused by TTA as a quenching channel at high brightness, achieving partitioned utilization of exciton resources and overall efficiency improvement. However, the bilayer structure does not break out of the physical framework of TTA in terms of mechanism. No matter how the layers are layered or how the excitons are transferred, the core of exciton upconversion is still the collision of two triplet states to produce a singlet state. According to spin statistics, only 1 / 9 of the 9 spin state combinations generated by the collision can generate a luminescent singlet state. Moreover, due to the additional interface introduced by the layering, the T1 of the EML1 body needs to be transferred to the EML2 via DET. This transfer process itself is not 100% efficient, and the actual gain is often less than the added loss, resulting in very limited improvement to the overall efficiency.

[0024] Based on the technical problems discovered in the aforementioned related display technologies, this invention provides a light-emitting device. The light-emitting device includes a light-emitting layer comprising a first light-emitting sublayer and a second light-emitting sublayer stacked together. The first light-emitting sublayer comprises a first host material and a first guest material, wherein the first host material is a blue fluorescent host material with triplet-triplet annihilation properties. The second light-emitting sublayer comprises a second host material, a phosphorescent sensitizer, and a second guest material, wherein the second host material is a blue phosphorescent host material. This invention employs a dual-layer light-emitting structure in a blue light-emitting device. One light-emitting layer uses a blue fluorescent host material and a fluorescent guest material, while the other light-emitting layer uses a blue phosphorescent host material, a blue phosphorescent sensitizer, and a fluorescent guest material. This allows singlet excitons generated by carrier recombination to emit light directly, while triplet excitons can be converted into singlet excitons through the TTA mechanism or the phosphorescent sensitizer. Compared to traditional blue fluorescence technology, this results in higher exciton utilization. Furthermore, the presence of the dual light-emitting layers achieves a certain degree of exciton separation, reducing exciton and polaron quenching and mitigating the lifetime degradation caused by phosphorescence technology.

[0025] In this embodiment of the invention, the first host material is a blue fluorescent host material with triplet-triplet annihilation properties, and the first guest material is a blue fluorescent guest material. Specifically, the first host material includes anthracene or pyrene-based materials, and the first guest material includes boron-nitrogen-based materials. Preferably, the first host material includes... , , , , Any one of the following, wherein the first object material includes , , , Any one of them.

[0026] The second host material is a blue phosphorescent host material, the phosphorescent photosensitizer is a blue phosphorescent photosensitizer, and the second guest material is a blue fluorescent guest material. Specifically, the second host material includes triarylsilane materials, the phosphorescent photosensitizer includes platinum complexes, and the second guest material includes boron-nitrogen materials. Preferably, the phosphorescent photosensitizer includes... , , , Any one of them, the second object material includes , , , Any one of them.

[0027] It should be noted that in the light-emitting layer of the light-emitting device provided by the present invention, the difference between the main peak of the emission spectrum of the first guest material and the second guest material is less than 2 nm, and the difference between the full width at half maximum (FWHM) is less than 3 nm; or, the first guest material and the second guest material are the same.

[0028] Optionally, in this embodiment of the invention, the second host material is an electronic host material or a hole host material, or a dual host material containing both electronic and hole host materials. The electronic host material refers to a host material with an electron mobility much greater than a hole mobility, typically containing electron-deficient groups (such as pyridine or triazine), which facilitates electron injection and transport. The hole host material refers to a host material with a hole mobility much greater than an electron mobility, typically containing electron-rich groups (such as carbazole), which facilitates hole injection and transport, but has a high electron injection barrier. For example, the electronic host material can be... , , , Any one of the following, wherein the cavity-type main body material can be , , , Any one of them.

[0029] like Figure 3 The diagram shown illustrates the light-emitting principle of a light-emitting device according to an embodiment of the present invention. The light-emitting layer 105 includes a first light-emitting sublayer 1051 and a second light-emitting sublayer 1052. The first light-emitting sublayer 1051 includes a first host material 1051a (also referred to as BH1 in the figure, full name Blue Host1) and a first guest material 1051b (also referred to as BD1 in the figure, full name Blue Dopant1). The second light-emitting sublayer 1052 includes a second host material 1052a (also referred to as BH2 in the figure, full name Blue Host2), a second guest material 1052b (also referred to as BD2 in the figure, full name Blue Dopant2) and a phosphorescent photosensitizer 1052c (also referred to as PBD in the figure, full name Phosphorescent Blue Dopant).

[0030] Continue to refer to Figure 3The specific light-emitting process of a light-emitting device provided in this embodiment of the invention is as follows: Under the drive of an applied electric field, holes and electrons are injected into the first light-emitting sublayer 1051 and the second light-emitting sublayer 1052, respectively, and recombine on the first host material 1051a and the second host material 1052a, respectively generating 25% singlet excitons (S1) and 75% triplet excitons (T1). The S1 of the second host material 1052a transfers part of its energy directly to the S1 of the first host material 1051a through Förster resonance energy transfer (FRET / FET). The T1 of the second host material 1052a transfers part of its energy directly to the T1 of the first host material 1051a through Dexter electron exchange transfer (DET). This step means that the exciton energy generated in the second light-emitting sublayer 1052 is actively pumped back to the first layer to supplement and enhance the exciton storage in the first light-emitting sublayer 1051. After accumulating excitons generated by itself and transferred from the second host material 1052a, the first photonic layer 1051 undergoes the following parallel processes: the S1 state of the first host material 1051a transfers energy to the S1 state of the first guest material 1051b via FRET. Subsequently, the S1 state of the first guest material 1051b undergoes a radiative transition, returning to the ground state (S0) and emitting nanosecond-level transient blue fluorescence. Simultaneously, a large amount of T1 accumulated on the first host material 1051a (including those generated by itself and transferred from the second host material 1052a) undergoes triplet-triplet annihilation (TTA), converting to the S1 state of the first host material 1051a through bimolecular collisions. The newly generated S1 state of the first host material 1051a is again transferred to the S1 state of the first guest material 1051b via FRET, driving the first guest material 1051b to emit additional microsecond-level TTA delayed fluorescence. That is, the blue light of the first luminescent layer 1051 consists of two parts: the transient fluorescence of the first guest material 1051b and the delayed fluorescence of TTA. Inside the second luminescent layer 1052, the remaining excitons of the second host material 1052a (the portion that has not been transferred to the first luminescent layer 1051) distribute energy through the following multiple pathways: the S1 of the second host material 1052a transfers energy to the S1 of the phosphorescent sensitizer 1052c and the S1 of the second guest material 1052b via FRET; the former is the main sensitization channel, and the latter is the direct sensitization emission channel. The T1 of the second host material 1052a transfers energy to the T1 of the phosphorescent sensitizer 1052c via DET (it should be noted that some of the T1 of the second host material 1052a has been returned to the first luminescent layer 1051, and the remaining portion follows this path). Thanks to the heavy metal spin-orbit coupling effect of phosphorescent sensitizer 1052c, the S1 of phosphorescent sensitizer 1052c subsequently undergoes ultrafast intersystem crossing (ISC), and is almost 100% converted into the T1 of phosphorescent sensitizer 1052c.Ultimately, the T1 state of the phosphorescent sensitizer 1052c transfers energy directly to the S1 state of the second guest material 1052b. The energy gathered on the S1 state of the second guest material 1052b (including the portion of the energy from the S1 state of the second host material 1052a directly FRETed to the S1 state of the second guest material 1052b, and the portion of the energy from the T1 state of the phosphorescent sensitizer 1052c to the S1 state of the second guest material 1052b) undergoes a radiative transition back to the ground state, emitting microsecond-level sensitized delayed blue fluorescence.

[0031] Compared to standalone blue fluorescence technology, the light-emitting device provided in this embodiment utilizes both singlet and triplet excitons for emission, resulting in higher exciton utilization and improved efficiency. Specifically, even with a TTA emission mechanism, the theoretical limit of the internal quantum efficiency (IQE) of standalone fluorescence is limited by spin probability and cannot exceed 62.5%. However, in this embodiment, the randomness of bimolecular collisions of TTA is bypassed, allowing the exciton utilization rate within the second emitting layer 1052 to reach nearly 100%. Combined with the TTA supplementation from the first emitting layer 1051 itself, the overall IQE of the device is significantly higher than that of standalone fluorescence technology. Compared to standalone blue phosphorescence technology, this embodiment achieves exciton separation, resulting in superior lifetime. Specifically, deep blue phosphorescent materials (such as Ir(III) complexes) have short device half-lives due to the high-energy T1 state easily inducing ligand bond breakage and molecular degradation. In this embodiment of the invention, the final light emitter is the first guest material 1051b and the second guest material 1052b. The phosphorescent sensitizer 1052c does not directly participate in the light emission. The device exhibits excellent chemical stability of fluorescent materials, and its working lifetime is close to that of pure fluorescent devices, which is superior to phosphorescent devices alone. Furthermore, due to the presence of the dual light-emitting layers, excitons are separated to a certain extent, reducing the quenching of excitons and polarons. Traditional single-layer or tandem structures often result in the recombination region being confined to a certain interface due to electron / hole mobility mismatch. In this embodiment of the invention, the second host material 1052a actively transmits excitons back to the first host material 1051a, expanding the recombination region from a single interface to a wide distribution region across the two layers, alleviating the quenching of excitons and polarons caused by high-density exciton accumulation at the interface.

[0032] like Figure 4 The diagram shown is a schematic diagram of a light-emitting device provided in an embodiment of the present invention. The light-emitting device includes a first electrode 101, a hole injection layer 102, a hole transport layer 103, an electron blocking layer 104, a light-emitting layer 105 (including a first light-emitting sub-layer 1051 and a second light-emitting sub-layer 1052), a hole blocking layer 106, an electron transport layer 107, an electron injection layer 108, and a second electrode 109, which are stacked together.

[0033] In this embodiment of the invention, the first electrode 101 is the anode with a high work function, used to inject holes into the organic layer, and often includes ITO (indium tin oxide), silver nanowires, graphene or ultrathin metals, etc.; the second electrode 105 is the cathode with a low work function, used to inject electrons into the organic layer, and often includes Al (aluminum), Mg:Ag (magnesium silver alloy), Ca, LiF / Al composite cathode.

[0034] Continue to refer to Figure 4 The first light-emitting layer 1051 is positioned closer to the electron blocking layer 104 (or closer to the anode), and the second light-emitting layer 1052 is positioned closer to the hole blocking layer 106 (or closer to the cathode). Preferably, the difference between the HOMO (highest occupied orbital) energy level of the first host material 1051a and the HOMO energy level of the electron blocking layer 104 is less than 0.3 eV, and the difference between the LUMO (lowest unoccupied orbital) energy level of the second host material 1052a and the LUMO energy level of the hole blocking layer 106 is less than 0.3 eV. This design achieves a lower carrier injection barrier, improves carrier injection, and thus helps to reduce the driving voltage and improve power efficiency. Simultaneously, the electron-blocking properties of the EBL and hole-blocking properties of the HBL, combined with the reduction of the charge injection barrier, cause holes to be mainly retained in the first photonic layer 1051 and electrons to be mainly retained in the second photonic layer 1052. This locks the exciton recombination region near the physical interface of the two photonic layers, ensuring that the interlayer energy backhaul (from T1 of the second host material 1052a to T1 of the first host material 1051a) and the transport from T1 of the first guest material 1051b to T1 of the phosphorescent sensitizer 1052c, which depend on short-range Dexter energy transfer, occur efficiently within the effective radius. Furthermore, it keeps the exciton recombination region away from the defect interface adjacent to the transport layer, effectively suppressing exciton and polaron quenching and extending the device's lifetime. In addition, this synergistic effect makes the first photonic layer 1051 rich in holes, which is beneficial for maximizing the TTA process; and the second photonic layer 1052 rich in electrons, which is beneficial for optimizing the phosphorescence sensitization process, ultimately improving the device's efficiency and lifetime.

[0035] like Figure 5 As shown, the first light-emitting layer 1051 is positioned close to the hole-blocking layer 106, and the second light-emitting layer 1052 is positioned close to the electron-blocking layer 104. Preferably, the difference between the LUMO energy level of the first host material 1051a and the LUMO energy level of the hole-blocking layer 106 is less than 0.3 eV, and the difference between the HOMO energy level of the second host material 1052a and the HOMO energy level of the electron-blocking layer 104 is less than 0.3 eV. This design is similar to... Figure 4 The illustrated embodiment is exactly the opposite, and its core function is also to improve carrier injection.

[0036] The light-emitting device provided by this invention can be either a top-emitting device structure or a bottom-emitting device structure. The vertical stacking order of the organic functional layers for bottom-emitting and top-emitting devices is completely identical, that is, as shown below... Figure 4 , Figure 5 As shown, from bottom to top, the following layers are stacked sequentially: first electrode 101, hole injection layer 102, hole transport layer 103, electron blocking layer 104, light-emitting layer 105, hole blocking layer 106, electron transport layer 107, electron injection layer 108, and second electrode 109. The difference is that the bottom-emitting device replaces the first electrode 101 with transparent ITO to allow light to be emitted from the glass, and replaces the second electrode 109 with a thick metal reflector.

[0037] Furthermore, regardless Figure 4 Whether the light-emitting device shown is a top-emitting device or a bottom-emitting device, the first light-emitting sub-layer 1051 is set close to the hole blocking layer 106, and the second light-emitting sub-layer 1052 is set close to the electron blocking layer 104. Preferably, the difference between the LUMO energy level of the first host material 1051a and the LUMO energy level of the hole blocking layer 106 is less than 0.3 eV, and the difference between the HOMO energy level of the second host material 1052a and the HOMO energy level of the electron blocking layer 104 is less than 0.3 eV, which can also play a role in improving carrier injection.

[0038] regardless Figure 5 Whether the light-emitting device shown is a top-emitting device or a bottom-emitting device, the first light-emitting sub-layer 1051 is set to be close to the electron blocking layer 104, and the second light-emitting sub-layer 1052 is set to be close to the hole blocking layer 106. Preferably, the difference between the HOMO energy level of the first host material 1051a and the HOMO energy level of the electron blocking layer 104 is less than 0.3 eV, and the difference between the LUMO energy level of the second host material 1052a and the LUMO energy level of the hole blocking layer 106 is less than 0.3 eV, which can also play a role in improving carrier injection.

[0039] In the light-emitting device provided by the present invention, the first guest material 1051b accounts for a mass fraction of 0.5wt%-10wt% of the first light-emitting sublayer 1051. For example, the mass fraction of the first guest material 1051b in the first light-emitting sublayer 1051 can be 0.5wt%, 1wt%, 2wt%, 6wt%, 9wt%, or 10wt%. The second guest material 1052b accounts for a mass fraction of 0.5wt%-5wt% of the second light-emitting sublayer 1052. For example, the mass fraction of the second guest material 1052b in the second light-emitting sublayer 1052 can be 0.5wt%, 1wt%, 1.5wt%, 2.5wt%, 4.5wt%, or 5wt%. The phosphorescent photosensitizer 1052c accounts for a mass fraction of 5wt%-25wt% of the second luminescent sublayer 1052. For example, the mass fraction of the phosphorescent photosensitizer 1052c in the second luminescent sublayer 1052 can be 5wt%, 10wt%, 12wt%, 16wt%, 20wt%, or 25wt%.

[0040] In the light-emitting device provided by the present invention, the thickness of the first light-emitting sublayer 1051 is in the range of 5nm-20nm. For example, the thickness of the first light-emitting sublayer 1051 can be 5nm, 10nm, 15nm, 18nm, 19nm, or 20nm; the thickness of the second light-emitting sublayer 1052 is in the range of 20nm-50nm. For example, the thickness of the second light-emitting sublayer 1052 can be 20nm, 25nm, 30nm, 38nm, 46nm, or 50nm.

[0041] The inventors conducted experimental research on the embodiments of the present invention, and the technical effects of the present application solution will be described below in conjunction with the experimental results.

[0042] Comparative Example 1: A light-emitting device with the following structure: first electrode 101 / hole injection layer 102 / hole transport layer 103 / electron blocking layer 104 / light-emitting layer 105 / hole blocking layer 106 / electron transport layer 107 / electron injection layer 108 / second electrode 109. The light-emitting layer 105 uses a blue fluorescent host material. and blue fluorescent guest materials .

[0043] Comparative Example 2: A light-emitting device with the following structure: first electrode 101 / hole injection layer 102 / hole transport layer 103 / electron blocking layer 104 / light-emitting layer 105 / hole blocking layer 106 / electron transport layer 107 / electron injection layer 108 / second electrode 109. The light-emitting layer 105 uses a blue phosphorescent host material. And the blue phosphorescent guest material bis(4,6-difluorophenylpyridine-N,C2)pyridinecarboxyliridium .

[0044] Example 1: A light-emitting device, with the following structure: first electrode 101 / hole injection layer 102 / hole transport layer 103 / electron blocking layer 104 / light-emitting layer 105 / hole blocking layer 106 / electron transport layer 107 / electron injection layer 108 / second electrode 109. The light-emitting layer 105 includes a first light-emitting sublayer 1051 and a second light-emitting sublayer 1052. The first light-emitting sublayer 1051 is located near the first electrode 101, and the second light-emitting sublayer 1052 is located near the second electrode 109. The first light-emitting sublayer 1051 includes a first host material 1051a. and the first object material 1051b The second light-emitting layer 1052 includes a second host material 1052a. Second object material 1052b and phosphorus photosensitizer 1052c .

[0045] Example 2: A light-emitting device, with the following structure: first electrode 101 / hole injection layer 102 / hole transport layer 103 / electron blocking layer 104 / light-emitting layer 105 / hole blocking layer 106 / electron transport layer 107 / electron injection layer 108 / second electrode 109. The light-emitting layer 105 includes a first light-emitting sublayer 1051 and a second light-emitting sublayer 1052. The first light-emitting sublayer 1051 is located near the first electrode 101, and the second light-emitting sublayer 1052 is located near the second electrode 109. The first light-emitting sublayer 1051 includes a first host material 1051a. and the first object material 1051b The second light-emitting layer 1052 includes a second host material 1052a. Second object material 1052b and phosphorus photosensitizer 1052c .

[0046] Example 3: A light-emitting device, with the following structure: first electrode 101 / hole injection layer 102 / hole transport layer 103 / electron blocking layer 104 / light-emitting layer 105 / hole blocking layer 106 / electron transport layer 107 / electron injection layer 108 / second electrode 109. The light-emitting layer 105 includes a first light-emitting sublayer 1051 and a second light-emitting sublayer 1052. The first light-emitting sublayer 1051 is located near the first electrode 101, and the second light-emitting sublayer 1052 is located near the second electrode 109. The first light-emitting sublayer 1051 includes a first host material 1051a. and the first object material 1051b The second light-emitting layer 1052 includes a second host material 1052a. Second object material 1052b and phosphorus photosensitizer 1052c .

[0047] The luminous efficiency and lifetime of the light-emitting devices provided in Examples 1-3 and Comparative Examples 1-2 were tested. With the luminous efficiency and lifetime of Comparative Example 1 as 100%, the relative values ​​of luminous efficiency and lifetime of Comparative Example 2 and Examples 1-3 are shown in Table 1.

[0048] Table 1

[0049] Referring to Table 1, in Example 1 based on the design concept of this invention, the luminous efficiency of the device is significantly improved by 55% compared to traditional fluorescent emission technology, and the luminous lifetime is also effectively improved by 36% compared to traditional phosphorescent emission technology. In Example 2, the luminous efficiency of the device is improved by 58% compared to traditional fluorescent emission technology, and the luminous lifetime is improved by 30% compared to traditional phosphorescent emission technology. In Example 3, the luminous efficiency of the device is improved by 51% compared to traditional fluorescent emission technology, and the luminous lifetime is improved by 40% compared to traditional phosphorescent emission technology. This demonstrates that the embodiments of this invention have a higher exciton utilization rate compared to traditional blue fluorescent technology. Furthermore, thanks to the design of using fluorescent technology in the first luminescent layer 1051 and phosphorescent-sensitized fluorescent technology in the second luminescent layer 1052, excitons are separated to a certain extent, which can reduce the quenching of excitons and polarons and improve the lifetime degradation caused by phosphorescence technology.

[0050] The present invention also provides a display device comprising the light-emitting device described above, or comprising a light-emitting device prepared by the above method, which can be installed as a display device in any electronic terminal with display function, such as a mobile phone, laptop computer, tablet computer, vehicle display, etc. The display device can be used to display static images, such as pictures or photographs. The display device can also be used to display dynamic images, such as videos.

[0051] In addition, the display device can also perform functions such as taking photos, recording videos, fingerprint recognition, and facial recognition. Accordingly, the display device also includes at least one functional module for implementing the above functions, such as an under-display camera or an under-display fingerprint recognition sensor.

[0052] The display device provided in the embodiments of this application and the light-emitting device provided in the embodiments of this application belong to the same inventive concept and have corresponding film layer structures and beneficial effects. Details not described in detail in the embodiments of the display device can be found in the embodiments of the display cover plate, and will not be repeated here.

[0053] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0054] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0055] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0056] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0057] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

[0058] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A light-emitting device, characterized in that, The light-emitting device includes a light-emitting layer, which includes a first light-emitting sub-layer and a second light-emitting sub-layer stacked together. The first luminescent sublayer comprises a first host material and a first guest material, wherein the first host material is a blue fluorescent host material with triplet-triplet annihilation properties; The second luminescent sublayer comprises a second host material, a phosphorescent sensitizer, and a second guest material, wherein the second host material is a blue phosphorescent host material.

2. The light-emitting device according to claim 1, characterized in that, The first guest material is a blue fluorescent guest material and the mass fraction of the first guest material in the first luminescent sublayer is in the range of 0.5wt%-10wt%.

3. The light-emitting device according to claim 2, characterized in that, The first host material includes anthracene or pyrene materials, and the first guest material includes boron-nitrogen materials; Preferably, the first main material includes , , , , Any one of them; The first object material includes , , , Any one of them.

4. The light-emitting device according to claim 1, characterized in that, The phosphorescent photosensitizer is a blue phosphorescent photosensitizer and the mass fraction of the phosphorescent photosensitizer in the second photonic layer is in the range of 5wt%-25wt%. The second guest material is a blue fluorescent guest material and the mass fraction of the second guest material in the second luminescent sublayer is in the range of 0.5wt%-5wt%.

5. The light-emitting device according to claim 4, characterized in that, The second host material includes triarylsilane materials, the phosphorus photosensitizer includes platinum complexes, and the second guest material includes boron nitrogen materials; Preferably, the phosphorus photosensitizer includes , , , Any one of them; The second object material includes , , , Any one of them.

6. The light-emitting device according to claim 5, characterized in that, The second main material is an electronic main material or a hole-type main material, or a dual main material that simultaneously contains electronic main materials and hole-type main materials; Preferably, the electronic body material includes , , , Any one of them; The cavitation-type main material includes , , , Any one of them.

7. The light-emitting device according to claim 1, characterized in that, The thickness of the first light-emitting sublayer is in the range of 5nm-20nm, and the thickness of the second light-emitting sublayer is in the range of 20nm-50nm; Preferably, the difference between the main peaks of the emission spectra of the first guest material and the second guest material is less than 2 nm, and the difference between their full width at half maximum (FWHM) is less than 3 nm. Alternatively, the first object material and the second object material are the same; Preferably, the light-emitting device further includes an electron blocking layer and a hole blocking layer, with the light-emitting layer located between the electron blocking layer and the hole blocking layer.

8. The light-emitting device according to claim 7, characterized in that, The first light-emitting sublayer is close to the electron blocking layer, and the second light-emitting sublayer is close to the hole blocking layer; Preferably, the difference between the highest occupied orbital energy level of the first host material and the highest occupied orbital energy level of the electron blocking layer is less than 0.3 eV, and the difference between the lowest unoccupied orbital energy level of the second host material and the lowest unoccupied orbital energy level of the hole blocking layer is less than 0.3 eV.

9. The light-emitting device according to claim 7, characterized in that, The first light-emitting sublayer is close to the hole blocking layer, and the second light-emitting sublayer is close to the electron blocking layer; Preferably, the difference between the lowest unoccupied orbital energy level of the first host material and the lowest unoccupied orbital energy level of the hole blocking layer is less than 0.3 eV, and the difference between the highest occupied orbital energy level of the second host material and the highest occupied orbital energy level of the electron blocking layer is less than 0.3 eV.

10. A display device, characterized in that, Includes the light-emitting device as described in any one of claims 1-9.

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