Light emitting device and display substrate

Abstract

The invention relates to a light emitting device and a display substrate. The light-emitting device comprises a first electrode, a light-emitting layer, a hole blocking layer and a second electrode which are sequentially stacked. Wherein the light-emitting layer comprises a host material and a guest material, and the hole blocking layer comprises an electron transport material and a quenching agent. The LUMO level of the host material is greater than the LUMO level of the quencher. The light-emitting layer disclosed by the invention can realize phosphorescent light emission. Further, the light-emitting layer further comprises a thermally activated delayed fluorescent material. The light-emitting layer disclosed by the invention can realize super-fluorescent light emission. The light-emitting efficiency of the light-emitting device can be improved, and the service life of the light-emitting device is prolonged.

Description

Technical Field

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

[0002] An organic light emitting device (OLED) is a device that emits light by being driven by electric current. Specifically, an organic light emitting device includes a cathode, an anode, and a light emitting layer located between the cathode and the anode. When voltage is applied, electrons from the cathode and holes from the anode migrate to the light emitting layer and combine to generate excitons, which then emit light of different wavelengths according to the characteristics of the light emitting layer.

[0003] Organic electroluminescent devices have become a research hotspot in flat panel display technology due to their advantages such as low voltage, low cost, wide viewing angle, fast response, and surface luminescence. Summary of the invention

[0004] The present disclosure aims to solve at least one of the technical problems existing in the prior art, and proposes a light emitting device and a display substrate.

[0005] In order to achieve the above object, the present disclosure provides a light-emitting device, comprising: a first electrode, a light-emitting layer, a hole blocking layer, and a second electrode, which are stacked in sequence;

[0006] Wherein, the light-emitting layer comprises a host material and a guest material, and the hole blocking layer comprises an electron transport material and a quencher;

[0007] The LUMO energy level of the host material is greater than the LUMO energy level of the quencher.

[0008] In some embodiments, the difference between the LUMO energy level of the host material and the LUMO energy level of the quencher is greater than 0.4 eV. In some embodiments, the light-emitting layer further comprises a thermally activated delayed fluorescent material, and the LUMO energy level of the thermally activated delayed fluorescent material is greater than the LUMO energy level of the quencher.

[0009] In some embodiments, the difference between the LUMO energy level of the thermally activated delayed fluorescent material and the LUMO energy level of the quencher is greater than 0.4 eV.

[0010] In some embodiments, the doping ratio of the quencher in the hole blocking layer is 0.1 wt % to 10 wt %.

[0011] In some embodiments, the LUMO energy level of the electron transport material is greater than the LUMO energy level of the quencher.

[0012] In some embodiments, the difference between the LUMO energy level of the electron transport material and the LUMO energy level of the quencher is greater than 0.3 eV.

[0013] In some embodiments, the electron transport material includes a first compound, and the structural formula of the first compound is as shown below:

[0014]

[0015] Wherein, AR1 and AR2 are both C1-C40 alkyl groups or C6-C60 aryl groups, n is a positive integer; Z1, Z2, and Z3 are hydrogen or nitrogen, and at least one of Z1, Z2, and Z3 is nitrogen.

[0016] In some embodiments, the electron transport material includes at least one of compounds D1 to D12:

[0017]

[0018]

[0019] In some embodiments, the quencher comprises at least one of compounds E1 to E8:

[0020]

[0021]

[0022] In some embodiments, the light emitted by the light-emitting layer includes blue light.

[0023] The present disclosure also provides a display substrate, comprising a light-emitting device as described in any one of the above. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0025] Figure 1 This is a schematic diagram of the electronic energy level conversion during the fluorescence and phosphorescence processes;

[0026] Figure 2 This is a schematic diagram of the light-emitting principle of superfluorescent display;

[0027] Figure 3 It is a schematic diagram of the cross-sectional structure of the light-emitting device in some embodiments of the present disclosure. DETAILED DESCRIPTION

[0028] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0030] Unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not represent any order, quantity or importance, but are only used to distinguish different components. Similarly, "including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0031] As used herein, "parallel" and "perpendicular" include the described situation and the situation similar to the described situation, and the range of the similar situation is within the acceptable deviation range, wherein the acceptable deviation range is determined by a person of ordinary skill in the art taking into account the measurement in question and the error associated with the measurement of a 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°.

[0032] It will be understood that when a layer or an 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 between the layer or element and the other layer or substrate.

[0033] Exemplary embodiments are described herein with reference to cross-sectional views and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are conceivable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but include deviations in shape due to, for example, manufacturing. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shapes of regions of the device, and are not intended to limit the scope of the exemplary embodiments.

[0034] In the related art, organic electroluminescence can be divided into two categories: fluorescence and phosphorescence. Figure 1 This is a schematic diagram of the electronic energy level conversion during the fluorescence and phosphorescence processes.

[0035] like Figure 1 As shown, electrons in organic light-emitting materials can transition from the ground state to the excited state under the action of an applied voltage. Among them, S0 is the ground state of the electron, that is, the state when the electron is not excited by energy, and the electron energy level is the S0 energy level. S1 and T1 are excited states, that is, the state after the electron is excited. Specifically, S1 belongs to the excited singlet state (also called the excited singlet state), and the electron energy level is the S1 energy level, while T1 belongs to the excited triplet state (also called the excited triplet state), and the electron energy level is the T1 energy level.

[0036] In one example, fluorescence occurs when an electron in an excited singlet state S1 first drops to the lowest vibrational energy level of the excited state through vibrational relaxation and then returns to the ground state S0 by emitting a photon.

[0037] In another example, electrons in the excited singlet state S1 may undergo intersystem crossing (ISC) to enter the excited triplet state T1 with a different spin state and a higher vibrational energy level. Electrons in the excited triplet state T1 first drop to the lowest vibrational energy level through vibrational relaxation, and then return to the ground state S0 by emitting photons, which will produce phosphorescence.

[0038] Obviously, under the action of applied voltage, the ground state electrons of electroluminescent materials are excited to a higher excited state energy level, forming electron-hole pairs, that is, generating excitons. Excitons can return from the excited state to the ground state in the form of radiative recombination to emit light, such as radiative recombination that can produce fluorescence, corresponding to fluorescent display, and radiative recombination that can produce phosphorescence, corresponding to phosphorescent display.

[0039] In the related technology, blue fluorescent light-emitting devices have been widely used in OLED (Organic Light-Emitting Diode) display devices due to their good stability. According to the principle of fluorescent light-emitting, only 25% of the excitons are used for light emission, which greatly limits the luminous efficiency of blue fluorescent light-emitting devices. However, phosphorescent display and superfluorescent display can achieve 100% exciton utilization, greatly improve the luminous efficiency of blue light-emitting devices, and also reduce the power consumption of blue light-emitting devices.

[0040] Figure 2 This is a schematic diagram of the luminescence principle of superfluorescent display.

[0041] like Figure 2 As shown, in the blue light-emitting device of superfluorescence display, the luminescence needs the host material, the guest material and the sensitizer to realize. Under the action of applied voltage, the electrons of the host material will transition from the ground state S0 to the excited singlet state S1 and the excited triplet state T1. When the excitons recombine, the energy of the excitons on the excited triplet state T1 can be confined on the sensitizer, and the electrons in the sensitizer transition from the ground state S0 to the excited singlet state S1 and the excited triplet state T1. The sensitizer adopts the thermally activated delayed fluorescence (TADF) material. Therefore, the sensitizer can convert the excitons on the excited triplet state T1 to the excited singlet state S1 through reverse intersystem crossing (RISC). The energy generated by the recombination of the excitons on the excited singlet state S1 makes the electrons in the guest material transition from the ground state S0 to the excited triplet state T1 and the excited singlet state S1. The excitons on the excited singlet state S1 undergo radiative recombination to realize luminescence, i.e., superfluorescence.

[0042] As can be seen from the above, both phosphorescent display and superfluorescent display use the excitons in the excited triplet state T1 to emit light. However, in general, the lifetime of the excitons in the excited triplet state T1 is longer, and the probability of non-radiative transition of the excitons will increase, resulting in an increase in triplet-triplet exciton annihilation (triplet-triplet annihilation, TTA) and triplet exciton-polaron annihilation (triplet-polaron annihilation, TPA), which in turn leads to a decrease in the luminous efficiency of blue light-emitting devices.

[0043] Moreover, in superfluorescence display, the current density in the organic light-emitting material of the blue light-emitting device is relatively high, which will lead to an increase in negative polarons, thereby causing the triplet exciton-polaron annihilation to intensify, and may also cause the degradation of the organic light-emitting material, seriously affecting the stability of the light-emitting device. Therefore, the luminous efficiency of the light-emitting device will further decrease, and the life of the light-emitting device will also be reduced.

[0044] In order to at least alleviate or solve one of the above-mentioned technical problems, the present disclosure provides a light emitting device and a display substrate.

[0045] Figure 3 It is a schematic diagram of the cross-sectional structure of the light-emitting device in some embodiments of the present disclosure.

[0046] The present disclosure provides a light emitting device, and the color emitted by the light emitting device includes blue, that is, the light emitting device provided by the present disclosure can be a blue light emitting device.

[0047] In some embodiments, Figure 3 As shown, the light emitting device of the present disclosure includes: a first electrode 1, a light emitting layer 5, a hole blocking layer 6 and a second electrode 9 which are stacked in sequence. The first electrode 1 may be, for example, an anode, and the second electrode 9 may be, for example, a cathode.

[0048] The light-emitting layer 5 can emit light under the action of the voltage between the first electrode 1 and the second electrode 9 , for example, can emit blue light.

[0049] In some embodiments, the blue light emitting device of the present disclosure may emit light using a phosphorescent system. In this case, the light emitting layer 5 includes a host material and a guest material, and the hole blocking layer 6 includes an electron transport material and a quencher. Moreover, the LUMO energy level of the host material is greater than the LUMO energy level of the quencher. Further, the LUMO energy level of the electron transport material is greater than the LUMO energy level of the quencher.

[0050] In the embodiments of the present disclosure, the host material and the guest material can realize the phosphorescent display of the light-emitting device. Specifically, under the action of the applied voltage, the electrons of the host material transition from the excited state to the excited singlet state S1 and the excited triplet state T1, and the energy of the excitons in the excited singlet state S1 is transferred to the guest material. After the guest material absorbs the energy, the electrons transition from the ground state S0 to the excited singlet state S1 and the excited triplet state T1, wherein the excitons in the excited triplet state T1 radiate light as phosphorescence.

[0051] Furthermore, the hole blocking layer 6 adjacent to the light-emitting layer 5 is doped with a quencher, and the LUMO energy level of the main material is greater than the LUMO energy level of the quencher. Therefore, in the process of radiative luminescence of electron-hole pairs in the light-emitting layer 5, when the electron concentration is high, the electrons that do not participate in the recombination can be captured by the quencher in the hole blocking layer 6, thereby effectively suppressing non-radiative processes such as triplet exciton-polaron annihilation.

[0052] At the same time, the LUMO energy level of the electron transport material is greater than the LUMO energy level of the quencher, which can also improve the electron transport capacity of the hole blocking layer 6, thereby reducing the electron accumulation on the critical surface between the light-emitting layer 5 and the hole blocking layer 6, broadening the exciton recombination area, and inhibiting triplet-triplet exciton annihilation.

[0053] Optionally, the material of the first electrode 1 and the second electrode 9 may include, for example, indium tin oxide (ITO).

[0054] Optionally, the electron mobility of the host material is μ e1 , the hole mobility is μ h1 , and μ e1 / μ h1 >10, for example, μ e1 / μ h1 The value of can be 50, 100, 200, 500, 1000, etc.

[0055] In the embodiment of the present disclosure, the electron mobility μ of the main material e Much larger than the hole mobility μ h , which can increase the transmission speed of electrons in the light-emitting layer 5, prevent the electrons from staying in the light-emitting layer 5 for a long time, thereby reducing the accumulation of electrons at the critical point between the light-emitting layer 5 and the hole blocking layer 6, and inhibiting the annihilation of triplet-triplet excitons.

[0056] At the same time, the embodiment of the present disclosure can also control the electron mobility μ e and hole mobility μ h The ratio of can make the carriers in the light-emitting device evenly distributed, reduce the voltage of the light-emitting device, and improve the luminous efficiency of the light-emitting device.

[0057] Optionally, the guest material may include a metal complex of an element such as iridium, platinum, palladium, cerium, etc., and the ligand may include at least one nitrogen heterocyclic carbene ligand.

[0058] In the embodiments of the present disclosure, metal complexes of elements such as iridium, platinum, palladium, cerium, etc., whose ligands contain at least one nitrogen heterocyclic carbene ligand, are doped into the host material as guest materials, which can reduce energy loss and improve luminous efficiency.

[0059] Optionally, the T1 energy level of the host material is greater than the T1 energy level of the guest material, and the difference is greater than 0.1 eV. For example, the difference may be 0.11 eV, 0.12 eV, 0.13 eV, 0.14 eV, 0.15 eV, 0.2 eV, etc.

[0060] Optionally, the LUMO energy level of the guest material is greater than -2.4 eV, for example, it may be -2.39 eV, -2.38 eV, -2.37 eV, -2.36 eV, -2.35 eV, -3 eV, etc.

[0061] Optionally, the LUMO energy level of the guest material is greater than the LUMO energy level of the host material, and the difference is greater than 0.2 eV, for example, the difference may be 0.21 eV, 0.22 eV, 0.23 eV, 0.24 eV, 0.25 eV, 0.3 eV, etc.

[0062] In the embodiment of the present disclosure, by setting the relationship between the T1 energy level, LUMO energy level and other energy levels of the main material and the shell material, the phosphorescent light-emitting efficiency of the light-emitting device can be improved.

[0063] Optionally, the mass ratio of the main material to the mass ratio of the light-emitting layer 5 is ≥70%, for example, it can be 70%, 75%, 80%, 85%, 90%, etc., and the mass ratio of the guest material to the mass ratio of the light-emitting layer 5 is ≤30%, for example, it can be 30%, 25%, 20%, 15%, 10%, etc.

[0064] In the embodiments of the present disclosure, by controlling the mass ratio of the main body material and the shell material, the energy conversion rate can be improved and the energy loss can be reduced.

[0065] Optionally, the host material includes at least one of compounds A1 to A8:

[0066]

[0067]

[0068] Optionally, the guest material includes at least one of compounds B1 to B3:

[0069]

[0070] The embodiments of the present disclosure can improve the phosphorescent light-emitting efficiency of the light-emitting device by selecting the specific compound structures contained in the host material and the guest material.

[0071] The light emitted by the light emitting layer 5 in the light emitting device of the embodiment of the present disclosure includes blue light, and the blue light emission peak is located at 450nm-470nm, and the FWHM (Full Wave at Half Maximum) is ≤40nm.

[0072] In some embodiments, the difference between the LUMO energy level of the host material and the LUMO energy level of the quencher is greater than 0.4 eV, and / or the difference between the LUMO energy level of the electron transport material and the LUMO energy level of the quencher is greater than 0.3 eV.

[0073] For example, in one example, the difference between the LUMO energy level of the host material and the LUMO energy level of the quencher is greater than 0.4 eV, for example, the difference between the LUMO energy level of the host material and the LUMO energy level of the quencher may be 0.41 eV, 0.42 eV, 0.43 eV, 0.44 eV, 0.45 eV, 0.46 eV, 0.47 eV, 0.48 eV, 0.49 eV, 0.5 eV, etc. Moreover, the difference between the LUMO energy level of the electron transport material and the LUMO energy level of the quencher is greater than 0.3 eV, for example, 0.31 eV, 0.32 eV, 0.33 eV, 0.34 eV, 0.35 eV, 0.36 eV, 0.37 eV, 0.38 eV, 0.39 eV, 0.4 eV, etc.

[0074] In the embodiment of the present disclosure, by setting the difference between the LUMO energy level of the host material and the LUMO energy level of the electron transport material and the LUMO energy level of the quencher, the quencher can improve the ability to capture excess electrons in the light-emitting layer 5, thereby improving the luminous efficiency of the light-emitting device. Excess electrons generally refer to electrons that do not participate in the recombination.

[0075] In addition, the quencher has a strong ability to capture electrons and can also reduce the accumulation of electrons at the critical point between the light-emitting layer 5 and the hole blocking layer 6, inhibit triplet-triplet exciton annihilation, and increase the life of the light-emitting device.

[0076] In some embodiments, the doping ratio of the quencher in the hole blocking layer 6 is 0.1wt% to 10wt%, for example, it can be 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%.

[0077] In the embodiment of the present disclosure, by setting the doping ratio of the quencher, it is possible to ensure that the quencher captures excess electrons in the light-emitting layer 5, thereby avoiding the accumulation of electrons at the critical point between the light-emitting layer 5 and the hole blocking layer 6, inhibiting triplet-triplet exciton annihilation, and improving the life of the light-emitting device.

[0078] In other embodiments, the blue light emitting device of the present disclosure may emit light using a superfluorescent system. In this case, the light emitting layer 5 includes a host material, a guest material and a sensitizer, and the sensitizer material is a thermally activated delayed fluorescent material. The hole blocking layer 6 includes an electron transport material and a quencher.

[0079] In the disclosed embodiments, the host material, the sensitizer and the guest material can realize superfluorescence display of the light-emitting device. Specifically, when the electron-hole in the host material recombine, the triplet T1 energy is confined on the sensitizer, and the triplet T1 energy is up-converted to the singlet S1 by utilizing the properties of the sensitizer material, and then the energy is transferred to the guest material through energy transfer, and the singlet S1 exciton in the guest material radiates and recombine to emit light.

[0080] Optionally, the host material includes a second compound, and the second compound includes at least one triazine group and at least one carbazole group.

[0081] Optionally, the electron mobility of the host material is μ e2 , the hole mobility is μ h2 , where μ e2 / μ h2 <10 -1 , for example, μ e2 / μ h2 The value can be 20 -1 , 50 -1 , 100 -1 wait.

[0082] Optionally, the electron mobility of the sensitizer is μ e3 , the hole mobility is μ h3 , where μ e3 / μ h3 >10, for example, μ e3 / μ h3 The value of can be 20, 50, 100, etc.

[0083] Optionally, the guest material is a multi-resonance material. Further, the guest material includes a third compound, and the third compound includes at least one B atom and at least one N atom.

[0084] Optionally, the S1 energy level of the host material is greater than the S1 energy level of the sensitizer, and the T1 energy level of the host material is greater than the T1 energy level of the sensitizer.

[0085] Optionally, the S1 energy level of the sensitizer is greater than the S1 energy level of the guest material, and the T1 energy level of the sensitizer is greater than the T1 energy level of the guest material.

[0086] In the embodiments of the present disclosure, the S1 and T1 energy levels of the host material are respectively greater than the S1 and T1 energy levels of the sensitizer, and the S1 and T1 energy levels of the sensitizer are respectively greater than the S1 and T1 energy levels of the guest material, which can enhance the ability of the sensitizer to convert the excitons on the excited triplet state T1 to the excited singlet state S1, thereby enhancing the luminescence efficiency of the superfluorescent display.

[0087] Optionally, the ΔE of the sensitizer ST(the difference between the S1 and T1 energy levels) is less than 0.3 eV, for example, ΔE ST It can be 0.29eV, 0.28eV, 0.27eV, 0.26eV, 0.25eV, etc.

[0088] In the disclosed embodiment, the difference between the S1 and T1 energy levels of the sensitizer is less than 0.3 eV, which is beneficial for the sensitizer to convert the excitons on the excited triplet state T1 to the excited singlet state S1, thereby improving the superfluorescence luminescence efficiency.

[0089] Optionally, the LUMO energy level of the sensitizer is less than -2.7 eV, for example, -2.71 eV, -2.72 eV, -2.73 eV, -2.74 eV, -2.75 eV, -2.8 eV, etc.

[0090] Optionally, the LUMO energy level of the host material is greater than the LUMO energy level of the sensitizer material, and the difference is greater than 0.2 eV, for example, the difference may be 0.21 eV, 0.22 eV, 0.23 eV, 0.24 eV, 0.25 eV, 0.3 eV, etc.

[0091] Optionally, the LUMO energy level of the guest material is greater than the LUMO energy level of the sensitizer material, and the difference is greater than 0.2 eV, for example, the difference may be 0.21 eV, 0.22 eV, 0.23 eV, 0.24 eV, 0.25 eV, 0.3 eV, etc.

[0092] In the disclosed embodiment, by setting the LUMO energy levels of the host material, the sensitizer and the guest material, the conversion rate of the excitons in the excited triplet state T1 to the excited singlet state S1 in the superfluorescent system can be further improved, thereby improving the luminescence efficiency.

[0093] Optionally, the ratio of the overlapping area between the absorption spectrum of the guest material and the emission spectrum of the sensitizer material to the emission spectrum area of ​​the sensitizer material is greater than or equal to 10%, for example, the ratio may be 10%, 15%, 20%, 25%, 30%, etc.

[0094] In the disclosed embodiment, the larger the ratio of the overlapping area between the absorption spectrum of the guest material and the emission spectrum of the sensitizer material to the emission spectrum area of ​​the sensitizer material, the larger the overlapping area between the absorption spectrum of the guest material and the emission spectrum of the sensitizer material. The larger the overlapping area between the absorption spectrum of the guest material and the emission spectrum of the sensitizer material, the more favorable it is for energy transfer, thereby improving the luminous efficiency.

[0095] Optionally, the ratio of the mass of the sensitizer to the total mass of the host material and the sensitizer is less than or equal to 30%, for example, it may be 30%, 25%, 20%, 15%, 10%, etc.

[0096] Optionally, the ratio of the guest material to the total mass of the host material and the sensitizer is less than or equal to 5%, for example, it may be 5%, 4%, 3%, 2%, 1%, etc.

[0097] In the disclosed embodiment, controlling the mass ratio of the sensitizer and the guest material in the light-emitting layer can ensure that the sensitizer converts the excitons in the excited triplet state T1 to the excited singlet state S1, while effectively improving the luminous efficiency of the light-emitting layer.

[0098] Optionally, the host material includes at least one of compounds X1 to X8:

[0099]

[0100]

[0101] Optionally, the sensitizer includes at least one of compounds Y1 to Y4:

[0102]

[0103] Optionally, the guest material includes at least one of compounds Z1 to Z6:

[0104]

[0105]

[0106] In the embodiments of the present disclosure, the superfluorescence luminescence efficiency of the light-emitting device can be improved by selecting the specific compound structures included in the host material, the guest material and the sensitizer.

[0107] The light emitted by the light-emitting layer 5 in the light-emitting device of the embodiment of the present disclosure includes blue light, and the blue light emission peak is located at 450nm~470nm, and the FWHM is ≤40nm.

[0108] In some embodiments, the LUMO energy level of the sensitizer is greater than the LUMO energy level of the quencher, and the LUMO energy level of the electron transport material is greater than the LUMO energy level of the quencher.

[0109] In the disclosed embodiment, the LUMO energy level of the sensitizer is greater than the LUMO energy level of the quencher, which can enable more excitons in the excited triplet state T1 energy level to be converted to the excited singlet state S1 energy level, and promote the radiative recombination of excitons in the excited singlet state S1 energy level on the guest material, thereby improving the luminous efficiency of the light-emitting device.

[0110] At the same time, the LUMO energy level of the electron transport material is greater than the LUMO energy level of the quencher, which can improve the electron transport ability of the hole blocking layer 6 and avoid the accumulation of electrons at the boundary between the hole blocking layer 6 and the light-emitting layer 5, resulting in triplet-triplet exciton annihilation.

[0111] In some embodiments, the difference between the LUMO energy level of the sensitizer and the LUMO energy level of the quencher is greater than 0.4 eV, and / or the difference between the LUMO energy level of the electron transport material and the LUMO energy level of the quencher is greater than 0.3 eV.

[0112] For example, in one example, the difference between the LUMO energy level of the sensitizer and the LUMO energy level of the quencher is greater than 0.4 eV, for example, the difference may be 0.41 eV, 0.42 eV, 0.43 eV, 0.44 eV, 0.45 eV, 0.46 eV, 0.47 eV, 0.48 eV, 0.49 eV, 0.5 eV, etc. Also, the difference between the LUMO energy level of the electron transport material and the LUMO energy level of the quencher is greater than 0.3 eV, for example, the difference may be 0.31 eV, 0.32 eV, 0.33 eV, 0.34 eV, 0.35 eV, 0.36 eV, 0.37 eV, 0.38 eV, 0.39 eV, etc.

[0113] The embodiment of the present disclosure ensures the ability of the sensitizer to convert the excitons of the excited triplet T1 energy level to the excited singlet S1 energy level by setting a specific difference between the LUMO energy level of the sensitizer and the LUMO energy level of the quencher.

[0114] Furthermore, the embodiment of the present disclosure ensures the electron transport capability of the hole blocking layer 6 by setting a specific difference between the LUMO energy level of the electron transport material and the LUMO energy level of the quencher, thereby preventing electrons from accumulating at the boundary between the hole blocking layer 6 and the light-emitting layer 5, leading to triplet-triplet exciton annihilation.

[0115] In summary, the light-emitting layer in the blue light-emitting device in the present disclosure can emit light using a superfluorescent system or a phosphorescent system. Wherein, when the light-emitting layer 5 emits light using a phosphorescent system, the light-emitting layer includes a host material and a guest material. When the light-emitting layer 5 emits light using a superfluorescent system, the light-emitting layer includes a host material, a guest material and a sensitizer, wherein the sensitizer is a thermally activated delayed fluorescent material. On this basis, selecting an electron transport material and a quencher as the material of the hole blocking layer 6 can improve the electron transport capacity and the ability to capture electrons that do not participate in the recombination, and avoid the accumulation of electrons at the interface between the hole blocking layer 6 and the light-emitting layer 5, resulting in triplet-triplet exciton annihilation.

[0116] Therefore, the embodiments of the present disclosure can effectively improve the utilization rate of the excitons in the excited triplet state T1 and increase the luminous efficiency.

[0117] Furthermore, corresponding materials are selected for each part in different systems to further improve the electron transmission capability and electron capture capability, thereby reducing triplet-triplet exciton annihilation and triplet exciton-polaron annihilation in the light-emitting device.

[0118] For the blue light emitting device in the embodiment of the present disclosure, whether it uses a superfluorescent system or a phosphorescent system to emit light, the electron transport material and the quencher in the hole blocking layer 6 can be selected as described below.

[0119] In some embodiments, the electron transport material includes a first compound, wherein the first compound has a structural formula as shown below:

[0120]

[0121] Wherein, AR1 and AR2 are both C1-C40 alkyl groups or C6-C60 aryl groups, n is a positive integer; Z1, Z2, and Z3 are hydrogen or nitrogen, and at least one of Z1, Z2, and Z3 is nitrogen.

[0122] In the disclosed embodiment, selecting a material conforming to the first compound structural formula as the electron transport material can improve the electron mobility of the hole blocking layer 6, thereby avoiding the accumulation of electrons at the critical surface between the light-emitting layer 5 and the hole blocking layer 6, and inhibiting triplet-triplet exciton annihilation.

[0123] In some embodiments, the electron transport material includes at least one of compounds D1 to D12:

[0124]

[0125]

[0126] In the disclosed embodiment, by setting the specific composition of the electron transport material, the electron mobility of the hole blocking layer 6 can be further guaranteed, thereby avoiding the accumulation of electrons at the critical surface between the light-emitting layer 5 and the hole blocking layer 6, and inhibiting the annihilation of triplet-triplet excitons.

[0127] In some embodiments, the quencher comprises at least one of compounds E1 to E8:

[0128]

[0129] In the embodiment of the present disclosure, by setting the specific composition of the quencher, the ability of the quencher to capture electrons can be further guaranteed, thereby further reducing the accumulation of electrons at the critical surface between the light-emitting layer 5 and the hole blocking layer 6, and inhibiting triplet-triplet exciton annihilation.

[0130] In the above-mentioned embodiments of the present disclosure, optionally, Figure 3As shown, the light emitting device further includes a hole injection layer 2 , a hole transport layer 3 and an electron blocking layer 4 which are located between the first electrode 1 and the light emitting layer 5 and are sequentially stacked in a direction away from the first electrode 1 .

[0131] Alternatively, if Figure 3 As shown, the light emitting device further includes an electron transport layer 7 and an electron injection layer 8 which are located between the hole blocking layer 6 and the second electrode 9 and are stacked along one side close to the second electrode 9 .

[0132] Of course, in other embodiments, the light-emitting device may include at least one of the hole injection layer 2, the hole transport layer 3, the electron blocking layer 4, the electron transport layer 7 and the electron injection layer 8, which may be set according to the actual needs of the light-emitting device. The embodiments of the present disclosure are not limited to this.

[0133] The following is a comparative analysis of the technical solutions and effects of the present invention in combination with specific comparative examples 1-4 and embodiments 1-2.

[0134] The structures of the light emitting devices of Comparative Examples 1-4 and Examples 1-2 are as follows: Figure 3 As shown, the relevant parameters of the film layers except the light-emitting layer 5 and the hole blocking layer 6 are the same, for example, the materials and film thickness of the hole injection layer 2, the hole transport layer 3, the electron blocking layer 4, the electron transport layer 7 and the electron injection layer 8 are the same in the comparative example and the embodiment.

[0135] In the light-emitting device of Comparative Example 1, the light-emitting layer 5 includes a host material and a shell material, and the hole blocking layer 6 includes an electron transport material, wherein the host material includes compound A1, the guest material includes compound B1, and the electron transport material includes compound D1.

[0136] In the light-emitting device of Comparative Example 2, the light-emitting layer 5 of the light-emitting device includes a host material and a shell material, and the hole blocking layer 6 includes an electron transport material and a quencher. The host material includes compound A1, the guest material includes compound B1, the electron transport material includes compound D1, the quencher includes compound M1, and the structural formula of compound M1 is shown below:

[0137]

[0138] And, the doping ratio of the quencher is 1 wt %.

[0139] The LUMO energy levels of the materials in Comparative Example 1 and Comparative Example 2 are shown in Table 1:

[0140] Table 1

[0141] Material A1 B1 D1 M1 LUMO level (eV) -2.58 -2.35 -2.79 -2.95

[0142] In the light-emitting device of comparative example 3, the light-emitting layer 5 includes a host material, a sensitizer and a guest material, and the hole blocking layer 6 includes an electron transport material. The host material includes compound X1, the sensitizer includes compound Y1, the guest material includes compound Z1, and the electron transport material includes compound D2.

[0143] In the light-emitting device of Comparative Example 4, the light-emitting layer 5 includes a host material, a sensitizer and a guest material, and the hole blocking layer 6 includes an electron transport material and a quencher. The host material includes compound X1, the sensitizer includes compound Y1, the guest material includes compound Z1, the electron transport material includes compound D2, and the quencher includes compound M1.

[0144] And, the doping ratio of the quencher is 1 wt %.

[0145] The LUMO energy levels of the materials in Comparative Examples 3 and 4 are shown in Table 2:

[0146] Table 2

[0147] Material X1 Y1 Z1 D2 M1 LUMO level (eV) -2.51 -2.76 -2.48 -2.88 -2.95

[0148] In the light-emitting device of Example 1, the light-emitting layer 5 includes a host material and a guest material, and the hole blocking layer 6 includes an electron transport material and a quencher. The host material includes compound A1, the guest material includes compound B1, the electron transport material includes compound D1, and the quencher includes compound E1. In addition, the doping ratio of the quencher is 1wt%.

[0149] The LUMO energy levels of the materials in Example 1 are shown in Table 3:

[0150] Table 3

[0151] Material A1 B1 D1 E1 LUMO level (eV) -2.58 -2.35 -2.79 -3.15

[0152] In the light-emitting device of Example 2, the light-emitting layer 5 includes a host material, a sensitizer material and a guest material Z1, and the hole blocking layer 6 includes an electron transport material and a quencher. The host material includes compound X1, the sensitizer includes compound Y1, the guest material includes compound Z1, the electron transport material includes compound D2, and the quencher includes compound E2. In addition, the doping ratio of the quencher is 1wt%.

[0153] The LUMO energy levels of the materials in Example 2 are shown in Table 4:

[0154] Table 4

[0155] Material X1 Y1 Z1 D2 E2 LUMO level (eV) -2.51 -2.76 -2.48 -2.88 -3.21

[0156] The performance of the light-emitting devices of the above-mentioned comparative examples 1-4 and embodiments 1-2 is shown in Table 5, including current efficiency CE@10nit, CE@1000nit, Roll-off@10~1000nit and lifespan T95@1000nit. Among them, CE@10nit and CE@1000nit respectively represent the current efficiency of the light-emitting device when the brightness is 10nit and 1000nit (the current efficiency of the light-emitting device when the brightness is 10nit is used as a reference). Lifespan T95@1000nit represents the lifespan of the light-emitting device when the brightness is 1000nit (the lifespan in comparative example 1 is used as a reference). Roll-off@10~1000nit refers to the current efficiency roll-off when the brightness increases from 10nit to 1000nit.

[0157] Table 5

[0158]

[0159] Comparing Comparative Example 1 and Example 1, as well as Comparative Example 3 and Example 2, it can be seen that: when the brightness is 10 nit, the current density in the light-emitting device is low, the quencher has little effect on the device performance, and the current efficiency of the light-emitting device is basically close. When the brightness is 1000 nit, the current density in the light-emitting device is high, and the excess electrons in the light-emitting layer 5 can be captured by the quencher, thereby reducing the accumulation of electrons on the interface between the light-emitting layer 5 and the hole blocking layer 6, broadening the exciton recombination area, and improving the current efficiency of the light-emitting device, that is, the luminous efficiency is improved, the roll-off is significantly reduced, and the life of the light-emitting device is improved, and the life improvement is greater than 10%.

[0160] Comparing Comparative Example 2 and Example 1, and Comparative Example 4 and Example 2, it can be seen that: although the quencher material is also doped, the LUMO energy level of the quencher M1 is shallow and cannot effectively capture the excess electrons in the light-emitting layer 5. The compound M1 selected as the quencher in Comparative Example 2 and Comparative Example 4 cannot effectively improve the device current efficiency, reduce roll-off, and increase the device life compared to the compound E1 selected as the quencher in Example 1, or compared to the compound E2 selected as the quencher in the embodiment. Therefore, the compound in the quencher in the embodiment of the present disclosure can effectively improve the current efficiency, reduce roll-off, and increase the device life.

[0161] In summary, the present disclosure provides a blue light emitting device, that is, a blue light display scheme is designed. The light emitting layer 5 of the blue light emitting device adopts a superfluorescent system or a phosphorescent system, and uses an electron transport material as the material of the hole blocking layer 6 adjacent to the light emitting layer 5, so as to improve the electron transport energy capacity of the hole blocking layer 6, and dope a low proportion of quencher in the electron transport material, and use a material with a deep LUMO energy level as a quencher, which can provide good conditions for the storage and transfer of electrons, thereby inhibiting the triplet-polaron annihilation process under high current density, which can improve the luminous efficiency, reduce roll-off, and increase the working life of the light emitting device.

[0162] The present disclosure also provides a display substrate, comprising the light-emitting device described in any one of the embodiments of the present disclosure. The display substrate in the embodiments of the present disclosure comprises a plurality of light-emitting devices, and the plurality of light-emitting devices are arranged in an array.

[0163] In one example, the plurality of light emitting devices may include a red light emitting device, a green light emitting device and a blue light emitting device, wherein the blue light emitting device is the light emitting device described in any one of the embodiments of the present disclosure.

[0164] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A light emitting device, characterized in that: It includes: a first electrode, a light-emitting layer, a hole blocking layer and a second electrode which are stacked in sequence; Wherein, the light-emitting layer comprises a host material and a guest material, and the hole blocking layer comprises an electron transport material and a quencher; The LUMO energy level of the host material is greater than the LUMO energy level of the quencher.

2. The light emitting device according to claim 1, characterized in that: The difference between the LUMO energy level of the host material and the LUMO energy level of the quencher is greater than 0.4 eV.

3. The light emitting device according to claim 1, characterized in that: The light emitting layer further includes a thermally activated delayed fluorescent material, and a LUMO energy level of the thermally activated delayed fluorescent material is greater than a LUMO energy level of the quencher.

4. The light emitting device according to claim 3, characterized in that: The difference between the LUMO energy level of the thermally activated delayed fluorescent material and the LUMO energy level of the quencher is greater than 0.4 eV.

5. The light emitting device according to any one of claims 1 to 4, characterized in that: The doping ratio of the quencher in the hole blocking layer is 0.1 wt % to 10 wt %.

6. The light emitting device according to any one of claims 1 to 4, characterized in that: The LUMO energy level of the electron transport material is greater than the LUMO energy level of the quencher.

7. The light emitting device according to claim 6, characterized in that: The difference between the LUMO energy level of the electron transport material and the LUMO energy level of the quencher is greater than 0.3 eV.

8. The light emitting device according to any one of claims 1 to 4, characterized in that: The electron transport material includes a first compound, and the structural formula of the first compound is shown as follows: Wherein, AR1 and AR2 are both C1-C40 alkyl groups or C6-C60 aryl groups, n is a positive integer; Z1, Z2, and Z3 are hydrogen or nitrogen, and at least one of Z1, Z2, and Z3 is nitrogen.

9. The light emitting device according to claim 8, characterized in that: The electron transport material includes at least one of compounds D1 to D12:

10. The light emitting device according to any one of claims 1 to 4, characterized in that: The quencher comprises at least one of compounds E1 to E8:

11. The light emitting device according to any one of claims 1 to 4, characterized in that: The light emitted by the light-emitting layer includes blue light.

12. A display substrate, characterized in that: The invention comprises the light emitting device according to any one of claims 1 to 11.

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