Light-emitting layer, light-emitting element, and display panel

Abstract

The embodiment of the present application discloses a light-emitting layer, a light-emitting element and a display panel, the light-emitting layer comprising: a first host material, a second host material, a guest material and an auxiliary material; wherein the first host material and the second host material form an excimer; the first excited triplet state energy level of the auxiliary material is lower than the first excited triplet state energy level of the excimer, and the first excited triplet state energy level of the auxiliary material is higher than the first excited triplet state energy level of the guest material. The present application increases the path of energy transfer from the excimer to the guest material by adding the auxiliary material, and the first excited triplet state energy level of the auxiliary material is between the first excited triplet state energy levels of the excimer and the guest material, reduces the energy loss in the energy transfer process, ensures the light-emitting efficiency of the light-emitting element and prolongs the service life of the light-emitting element.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of display, in particular to a light-emitting layer, a light-emitting element and a display panel. BACKGROUND

[0002] At present, organic light-emitting elements are widely concerned in the field of display due to their thinness, lightness, high-speed response to input signals, direct-current low-voltage driving and other excellent properties. The display panel using the organic light-emitting element has excellent display capability, low power consumption and superior bending performance. With the development of the display panel with the organic light-emitting element and the improvement of user demand, the improvement of the light-emitting efficiency and the service life of the organic light-emitting element is a key to the competitiveness of the display panel including the organic light-emitting element. The light-emitting efficiency and the service life of the existing organic light-emitting element often present a competitive relationship. Prolonging the service life of the organic light-emitting element needs to sacrifice the light-emitting efficiency of the organic light-emitting element, for example: the method of designing and using small singlet-triplet energy gap materials, which has the problem of energy transfer between the host material and the guest material, thereby causing the reduction of the light-emitting efficiency of the light-emitting element.

[0003] Therefore, there is an urgent need for a light-emitting layer, a light-emitting element and a display panel to solve the above technical problems. SUMMARY

[0004] The present application provides a light-emitting layer, a light-emitting element and a display panel, which can alleviate the technical problem that the service life of the light-emitting element cannot be improved while ensuring the light-emitting efficiency of the light-emitting element.

[0005] The present application provides a light-emitting layer, comprising:

[0006] a pair of electrodes;

[0007] a light-emitting layer located between the pair of electrodes, the light-emitting layer comprising a first host material, a second host material, a guest material and an auxiliary material;

[0008] wherein the first host material and the second host material form an exciplex;

[0009] The first excited triplet energy level of the auxiliary material is lower than the first excited triplet energy level of the exciplex, and the first excited triplet energy level of the auxiliary material is higher than the first excited triplet energy level of the guest material.

[0010] Preferably, the highest occupied molecular orbital energy level of the auxiliary material is higher than the highest occupied molecular orbital energy level of the first host material, the highest occupied molecular orbital energy level of the auxiliary material is higher than the highest occupied molecular orbital energy level of the second host material, and the highest occupied molecular orbital energy level of the auxiliary material is lower than the highest occupied molecular orbital energy level of the guest material.

[0011] Preferably, the lowest unoccupied molecular orbital energy level of the auxiliary material is lower than the lowest unoccupied molecular orbital energy level of the first host material, the lowest unoccupied molecular orbital energy level of the auxiliary material is lower than the lowest unoccupied molecular orbital energy level of the second host material, and the lowest unoccupied molecular orbital energy level of the auxiliary material is higher than the lowest unoccupied molecular orbital energy level of the guest material.

[0012] Preferably, the first excited singlet state energy level of the first host material is higher than the first excited singlet state energy level of the auxiliary material, the first excited singlet state energy level of the second host material is higher than the first excited singlet state energy level of the auxiliary material, and the first excited singlet state energy level of the auxiliary material is higher than the first excited singlet state energy level of the guest material.

[0013] Preferably, the first absorption band of the auxiliary material in the range of 400 nm to 550 nm overlaps with the second absorption band of the guest material in the range of 400 nm to 550 nm, and the exciplex has a first emission band in the range of 400 nm to 550 nm.

[0014] Wherein, the first emission band at least partially overlaps with the first absorption band, the first emission band at least partially overlaps with the second absorption band, and the first absorption band at least partially overlaps with the second absorption band.

[0015] Preferably, the auxiliary material has a first absorption peak in the range of 400 nm to 550 nm, the guest material has a second absorption peak in the range of 400 nm to 550 nm, and the peak wavelength of the first absorption peak is smaller than the peak wavelength of the second absorption peak.

[0016] At the first temperature, the exciplex has a first emission peak, and the peak wavelength of the first emission peak is greater than or equal to the peak wavelength of the second absorption peak.

[0017] Preferably, at the first temperature, the difference between the peak wavelength of the first emission peak and the peak wavelength of the first absorption peak is greater than or equal to 60 nm, and the difference between the peak wavelength of the first emission peak and the peak wavelength of the second absorption peak is less than or equal to 30 nm.

[0018] Preferably, at the first temperature, the peak wavelength of the emission peak of the auxiliary material is greater than the peak wavelength of the emission peak of the exciplex, and the peak wavelength of the emission peak of the auxiliary material is less than the peak wavelength of the emission peak of the guest material.

[0019] Preferably, at the first temperature, the difference between the peak wavelength of the emission peak of the auxiliary material and the peak wavelength of the emission peak of the exciplex is greater than or equal to the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material.

[0020] Preferably, at the first temperature, the difference between the peak wavelength of the emission peak of the auxiliary material and the peak wavelength of the emission peak of the exciplex is less than or equal to 30 nanometers, and the difference between the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material is less than or equal to 10 nanometers.

[0021] Preferably, the auxiliary material and the guest material are respectively selected from one of the organometallic compounds of platinum, iridium or osmium.

[0022] Preferably, the guest material is an organometallic compound of platinum or iridium, and the auxiliary material is an organometallic compound of platinum or iridium different from the guest material; or,

[0023] The guest material is an organometallic compound of osmium, and the auxiliary material is an organometallic compound of osmium.

[0024] Preferably, the first host material and the second host material account for 80% to 99.8% of the volume fraction of the light-emitting layer, the guest material accounts for 0.1% to 10% of the volume fraction of the light-emitting layer, and the auxiliary material accounts for 0.1% to 10% of the volume fraction of the light-emitting layer.

[0025] Preferably, at the first temperature, the peak wavelength of the light emitted by the light-emitting element is 500 nanometers to 700 nanometers.

[0026] Preferably, at the first temperature, the peak wavelength of the light emitted by the light-emitting element is 500 nanometers to 560 nanometers.

[0027] The application also provides a light-emitting element, comprising:

[0028] A pair of electrodes, comprising a first electrode and a second electrode;

[0029] A light-emitting layer between the pair of electrodes, the light-emitting layer comprising a first host material, a second host material, a guest material and an auxiliary material;

[0030] The first host material and the second host material form an exciplex.

[0031] the first excited triplet energy level of the auxiliary material is lower than the first excited triplet energy level of the exciplex, and the first excited triplet energy level of the auxiliary material is higher than the first excited triplet energy level of the guest material;

[0032] the first host material is a hole-transporting organic compound, and the second host material is an electron-transporting organic compound, and the first host material is selected from the group consisting of an aromatic amine compound and a carbazole compound, and the second host material is selected from the group consisting of a heteroaromatic compound.

[0033] Preferably, the mobility of the first host material is 1.29*10^(-7) [m / (V·s)] to 1.93*10^(-7) [m / (V·s)], and the mobility of the second host material is 6.4*10^(-8) [m / (V·s)] to 9.6*10^(-8) [m / (V·s)]. 2 2 2 2

[0034] Preferably, the mobility of the first host material is 1.61*10^(-7) [m / (V·s)], and the mobility of the second host material is 8*10^(-8) [m / (V·s)]. 2 2

[0035] Preferably, the doping ratio of the first host material to the second host material is 5:5 to 7:3.

[0036] Preferably, the light-emitting element further comprises:

[0037] a hole-transporting layer between the first electrode and the light-emitting layer;

[0038] an electron-transporting layer between the light-emitting layer and the second electrode.

[0039] Preferably, the ratio of the mobility of the hole-transporting layer to the mobility of the electron-transporting layer is 5 to 200.

[0040] Preferably, the mobility of the hole-transporting layer is 1 to 10*10^(-4) [m / (V·s)], and the mobility of the electron-transporting layer is 5*10^(-6) to 2*10^(-5) [m / (V·s)]. 2 2

[0041] Preferably, the ratio of the thickness of the hole-transporting layer to the thickness of the electron-transporting layer is 3.5:1 to 5.5:1. ​​​​​​​​

[0042] Preferably, the light-emitting element further comprises:

[0043] a first blocking layer between the hole transport layer and the light-emitting layer;

[0044] wherein the difference between the highest occupied molecular orbital energy level of the first blocking layer and the highest occupied molecular orbital energy level of the exciplex is less than 0.3eV.

[0045] Preferably, the difference between the lowest unoccupied molecular orbital energy level of the first blocking layer and the lowest unoccupied molecular orbital energy level of the exciplex is greater than 0.05eV, the difference between the highest occupied molecular orbital energy level of the hole transport layer and the highest occupied molecular orbital energy level of the first blocking layer is less than 0.3eV, and the difference between the lowest unoccupied molecular orbital energy level of the hole transport layer and the lowest unoccupied molecular orbital energy level of the first blocking layer is greater than 0.05eV.

[0046] Preferably, the electron transport layer is in direct contact with the light-emitting layer, the electron transport layer is in direct contact with the light-emitting layer, the difference between the lowest unoccupied molecular orbital energy level of the electron transport layer and the lowest unoccupied molecular orbital energy level of the exciplex is less than 0.3eV, and the difference between the lowest unoccupied molecular orbital energy level of the electron transport layer and the lowest unoccupied molecular orbital energy level of the first blocking layer is less than 0.3eV.

[0047] Preferably, the light-emitting element further comprises a second blocking layer between the light-emitting layer and the electron transport layer, the difference between the lowest unoccupied molecular orbital energy level of the second blocking layer and the lowest unoccupied molecular orbital energy level of the exciplex is less than 0.3eV, and the difference between the lowest unoccupied molecular orbital energy level of the electron transport layer and the lowest unoccupied molecular orbital energy level of the second blocking layer is less than 0.3eV.

[0048] The present application also provides a display panel comprising the light-emitting element as described above.

[0049] The present application increases the path of energy transfer from the exciplex to the guest material by adding the auxiliary material, and the first excited triplet energy level of the auxiliary material is between the first excited triplet energy level of the exciplex and the first excited triplet energy level of the guest material, reduces the energy loss in the energy transfer process, ensures the light-emitting efficiency of the light-emitting element, and prolongs the service life of the light-emitting element. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0051] Figure 1 is a schematic diagram of the light emitting principle of the existing light emitting element;

[0052] Figure 2 is a schematic diagram of the light emitting principle of the light emitting element provided by the embodiment of the present application;

[0053] Figure 3 is a schematic diagram of the first structure of the light emitting element provided by the embodiment of the present application;

[0054] Figure 4 is a schematic diagram of the second structure of the light emitting element provided by the embodiment of the present application;

[0055] Figure 5 is a schematic diagram of the third structure of the light emitting element provided by the embodiment of the present application;

[0056] Figure 6 is a schematic diagram of the fourth structure of the light emitting element provided by the embodiment of the present application;

[0057] Figure 7 is a schematic diagram of the triplet energy level of the exciplex, the auxiliary material and the guest material of the light emitting element provided by the embodiment of the present application;

[0058] Figure 8 is a schematic diagram of the HOMO energy level, the LUMO energy level and the energy difference of each material of the light emitting element provided by the embodiment of the present application;

[0059] Figure 9 is a schematic diagram of the absorption spectrum and the emission spectrum of the exciplex, the auxiliary material and the guest material of the light emitting element provided by the embodiment of the present application;

[0060] Figure 10 is a schematic diagram of the emission spectrum of the light emitting element provided by the embodiment of the present application;

[0061] Figure 11 is a schematic diagram of the light emitting lifetime of the light emitting element provided by the embodiment of the present application. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device.

[0063] At present, the service life and the luminous efficiency of the existing organic light-emitting element are in a competitive relationship, and there is a problem that it is difficult to improve the service life of the organic light-emitting element while ensuring the luminous efficiency of the organic light-emitting element.

[0064] The present application provides a light-emitting layer, comprising:

[0065] A first host material, a second host material, a guest material and an auxiliary material; wherein the first host material and the second host material form an exciplex; the first excited triplet energy level of the auxiliary material is lower than the first excited triplet energy level of the exciplex, and the first excited triplet energy level of the auxiliary material is higher than the first excited triplet energy level of the guest material.

[0066] The present application adds the auxiliary material, and the first excited triplet energy level of the auxiliary material is between the first excited triplet energy levels of the exciplex and the guest material, thereby increasing the path of energy transfer from the exciplex to the guest material, reducing the energy loss in the energy transfer process, and ensuring the luminous efficiency of the light-emitting layer while prolonging the service life of the light-emitting element.

[0067] In the present embodiment, the first host material and the second host material are the two materials with the highest content in the light-emitting layer. The volume fraction of the first host material and the second host material in the light-emitting layer accounts for 80% to 99.8% of the light-emitting layer; the guest material and the auxiliary material are dispersed in the first host material and the second host material, the volume fraction of the guest material in the light-emitting layer accounts for 0.1% to 10%, and the volume fraction of the auxiliary material in the light-emitting layer accounts for 0.1% to 10%. The dispersion of the guest material and the auxiliary material in the first host material and the second host material is conducive to inhibiting the crystallization of the light-emitting layer and inhibiting the concentration quenching of the guest material and the auxiliary material due to high concentration, thereby ensuring the luminous efficiency of the light-emitting element.

[0068] Referring to Figure 1 The general light emitting process of the light emitting element is as follows.

[0069] (1) When an electron and a hole are recombined in a guest material molecule, the guest material molecule is in an excited state: when the excited state of the guest material molecule is a first excited triplet state (T1), the guest material molecule emits phosphorescence; when the excited state of the guest material molecule is a first excited singlet state (S1), the guest material molecule in the first excited singlet state undergoes intersystem crossing to the first excited triplet state, and then the guest material molecule emits phosphorescence.

[0070] (2) When an electron and a hole are recombined in a host material molecule, the host material molecule is in an excited state: when the excited state of the host material molecule is a first excited triplet state, the first excited triplet state energy level of the host material is higher than the first excited triplet state energy level of the guest material, the excitation energy is transferred from the host material to the guest material, the guest material molecule is in the first excited triplet state, and the guest material molecule emits phosphorescence; at this time, although there may be a possibility of energy transfer to the first excited singlet state of the guest material molecule, in most cases the first excited singlet state energy level of the guest material molecule is higher than the first excited triplet state energy level of the host material, and it is not easy to form a main energy transfer path, so the description is omitted. When the excited state of the host material molecule is a first excited singlet state, the first excited singlet state energy level of the host material is higher than the first excited singlet state energy level of the guest material molecule and the first excited triplet state energy level of the guest material molecule, the excitation energy is transferred from the host material to the guest material, the guest material molecule is in the first excited singlet state or the first excited triplet state, the guest material molecule in the first excited triplet state emits phosphorescence, and the guest material molecule in the first excited singlet state emits phosphorescence by undergoing intersystem crossing to the first excited triplet state.

[0071] Referring to Figure 2The embodiment adds the auxiliary material to increase the energy transfer path from the host material to the guest material, and the energy transfer path is as follows: when the excited state of the exciplex is the first excited triplet state, the first excited triplet state energy level of the exciplex is higher than the first excited triplet state energy level of the auxiliary material molecule, the first excited triplet state energy level of the auxiliary material molecule is higher than the first excited triplet state energy level of the guest material molecule, the excitation energy exists in the transfer path from the exciplex to the guest material and from the exciplex to the auxiliary material and then to the guest material, the guest material molecule is in the first excited triplet state, and the guest material molecule emits phosphorescence; when the excited state of the exciplex molecule is the first excited singlet state, the first excited singlet state energy level of the exciplex is higher than the first excited singlet state energy level and the first excited triplet state energy level of the auxiliary material molecule, the first excited singlet state energy level and the first excited triplet state energy level of the auxiliary material molecule are higher than the first excited singlet state of the guest material molecule and the first excited triplet state of the guest material molecule, the excitation energy exists in the transfer path from the exciplex to the guest material and from the exciplex to the auxiliary material and then to the guest material, after the energy is transferred from the exciplex to the auxiliary material, the auxiliary material molecule is in the first excited singlet state or the first excited triplet state, and the auxiliary material molecule exists in the intersystem crossing from the first excited singlet state to the first excited triplet state, after the guest material molecule receives the energy from the first excited singlet state and the first excited triplet state of the auxiliary material molecule, the guest material molecule is in the first excited singlet state or the first excited triplet state, the guest material molecule in the first excited triplet state emits phosphorescence, and the guest material molecule in the first excited singlet state emits phosphorescence by intersystem crossing to the first excited triplet state. The embodiment increases the energy transfer path between the exciplex and the guest material by adding the auxiliary material, and the energy loss of the energy transfer path through the auxiliary material is less than the direct energy transfer between the exciplex and the guest material due to the decrease of the energy level gap in the energy transfer process, thereby improving the energy transfer efficiency and prolonging the service life of the light-emitting element.

[0072] Preferably, the first excited singlet state energy level of the first host material is higher than the first excited singlet state energy level of the auxiliary material, the first excited singlet state energy level of the second host material is higher than the first excited singlet state energy level of the auxiliary material, and the first excited singlet state energy level of the auxiliary material is higher than the first excited singlet state energy level of the guest material.

[0073] The guest material can be a phosphorescent compound, and the guest material and the auxiliary material are each selected from one of organic metal compounds of platinum, iridium or osmium. By virtue of the guest material and the auxiliary material being organic metal compounds, the auxiliary material improves the π-π stacking between guest material molecules, improves the dispersibility of the guest material in the light-emitting layer, reduces the probability of mutual collision between the guest material in the first excited triplet state, reduces the damage to the guest material caused by collision, and prolongs the service life of the light-emitting element; at the same time, the number of guest material molecules in the first excited triplet state that release energy in the form of light is increased, which also improves the light-emitting efficiency of the light-emitting element and prolongs the service life of the light-emitting element.

[0074] Preferably, in consideration of the difference in the first excited triplet state energy level between metal organic compounds formed by different kinds of metals, when the guest material is an organic metal compound of platinum or iridium, the auxiliary material is an organic metal compound of platinum or iridium different from the guest material; and when the guest material is an organic metal compound of osmium, the auxiliary material is an organic metal compound of osmium.

[0075] Specifically, the guest material can be selected from any one or a combination of the following compounds, and the auxiliary material can be selected from any one or a combination of the following compounds:

[0076]

[0077]

[0078] At the first temperature, which can be room temperature, the first host material and the second host material are organic compounds, so that the emission spectrum of the exciplex formed by the two at room temperature is generally an emission spectrum from the first excited singlet state; the guest material and the auxiliary material are phosphorescent compounds, and the emission spectrum at room temperature is generally an emission spectrum from the first excited triplet state; thus, the exciplex, the auxiliary material and the guest material can reflect the relative sizes of the first excited singlet state energy level of the exciplex, the first excited triplet state energy level of the auxiliary material and the first excited triplet state energy level of the guest material. Preferably, at the first temperature, the peak wavelength of the emission peak of the auxiliary material is greater than the peak wavelength of the emission peak of the exciplex, and the peak wavelength of the emission peak of the auxiliary material is less than the peak wavelength of the emission peak of the guest material.

[0079] The first excited singlet energy level of the exciplex is higher than the first excited triplet energy level, and the first excited triplet energy level of the exciplex is high enough to the first excited triplet energy level of the auxiliary material so that energy can be transferred from the exciplex to the auxiliary material, and the difference between the peak wavelength of the emission peak of the auxiliary material and the peak wavelength of the emission peak of the exciplex is greater than or equal to the difference between the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material at the first temperature.

[0080] Preferably, the difference between the peak wavelength of the emission peak of the auxiliary material and the peak wavelength of the emission peak of the exciplex is less than or equal to 30 nanometers, and the difference between the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material is less than or equal to 10 nanometers at the first temperature.

[0081] The emission wavelength depends on the energy difference between the highest occupied molecular orbital (HOMO) energy level and the lowest unoccupied molecular orbital (LUMO) energy level, and therefore, the highest occupied molecular orbital energy level of the auxiliary material is higher than the highest occupied molecular orbital energy level of the exciplex, and the highest occupied molecular orbital energy level of the auxiliary material is lower than the highest occupied molecular orbital energy level of the guest material; the lowest unoccupied molecular orbital energy level of the auxiliary material is lower than the lowest unoccupied molecular orbital energy level of the exciplex, and the lowest unoccupied molecular orbital energy level of the auxiliary material is higher than the lowest unoccupied molecular orbital energy level of the guest material. By adjusting the energy difference between the HOMO and LUMO of the exciplex, the auxiliary material and the guest material, the peak wavelength of the emission peak of the exciplex, the auxiliary material and the guest material can be controlled. Preferably, the highest occupied molecular orbital energy level of the auxiliary material is higher than the highest occupied molecular orbital energy level of the first host material, and the highest occupied molecular orbital energy level of the auxiliary material is higher than the highest occupied molecular orbital energy level of the second host material, and the highest occupied molecular orbital energy level of the auxiliary material is lower than the highest occupied molecular orbital energy level of the guest material. The lowest unoccupied molecular orbital energy level of the auxiliary material is lower than the lowest unoccupied molecular orbital energy level of the first host material, and the lowest unoccupied molecular orbital energy level of the auxiliary material is lower than the lowest unoccupied molecular orbital energy level of the second host material, and the lowest unoccupied molecular orbital energy level of the auxiliary material is higher than the lowest unoccupied molecular orbital energy level of the guest material.

[0082] The light emitted by the guest material at the first temperature has a wavelength in the range of 500 nm to 700 nm. Preferably, the guest material is a green phosphorescent material, and the light emitted by the guest material has a peak wavelength in the range of 500 nm to 560 nm.

[0083] Correspondingly, the light emitted by the light emitting element at the first temperature has a wavelength in the range of 500 nm to 700 nm. Preferably, the light emitting element is a green light emitting element, and the light emitted by the light emitting element has a peak wavelength in the range of 500 nm to 560 nm.

[0084] The light emitting layer can be used in a blue light emitting element, a green light emitting element, or a red light emitting element, depending on the color of the light emitted by the guest material. The thickness of the light emitting layer varies depending on the color of the light emitting element. When the light emitting layer is a red light emitting layer, the thickness of the light emitting layer is preferably in the range of 160 A to 240 A, more preferably 190 A, 200 A, or 210 A. When the light emitting layer is a blue light emitting layer, the thickness of the light emitting layer is preferably in the range of 160 A to 240 A, more preferably 190 A, 200 A, or 210 A. When the light emitting layer is a green light emitting layer, the thickness of the light emitting layer is preferably in the range of 320 A to 480 A, more preferably 390 A, 400 A, or 410 A.

[0085] The general process of energy transfer in the light emitting layer of a light emitting element is as follows:

[0086] (1) Forster energy transfer mechanism: energy transfer occurs through resonance of dipole oscillation between the host molecule and the guest molecule. Through resonance of dipole oscillation, the host material molecule transfers energy to the guest material molecule, and the host material molecule returns to the ground state, while the guest material molecule is in the excited state.

[0087] (2) Dexter energy transfer mechanism: the host material molecule and the guest material molecule are in contact at a distance close enough to produce orbital overlap, and the electron of the excited state host material molecule and the electron of the ground state guest material molecule exchange, thereby causing energy transfer.

[0088] In the above two energy transfer mechanisms, the greater the overlap between the emission spectrum of the host material molecule (fluorescence spectrum produced when the first excited singlet state returns to the singlet ground state, and phosphorescence spectrum produced when the first excited triplet state returns to the singlet ground state) and the absorption spectrum of the guest material molecule, the more conducive to energy transfer.

[0089] The first embodiment is first formed by the first host material and the second host material to form an exciplex, the exciplex is formed by the interaction of the first host material molecule in the excited state and the second host material molecule in the excited state, the first host material can be one of a hole transport organic compound or an electron transport property compound, the second host material can be the other of a hole transport organic compound or an electron transport property compound, for example, the first host material is a hole transport organic compound, and the second host material is an electron transport property compound.

[0090] Among them, the compound with hole transport property includes aromatic amine or carbazole compound, and the compound with electron transport property includes heteroaromatic compound.

[0091] The first host material and the second host material can be independently selected from bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO), 4,4'-bis(carbazol-9-yl)diphenyl (CBP), 1,3-bis(carbazol-9-yl)benzene (mCP), 2,8-bis(diphenylphosphoryl)dibenzo[b,d]furan (PPF), 4,4',4"-tris(carbazol-9-yl)-triphenylamine (TCTA), 1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi), tris(8-hydroxyquinoline)aluminum (Alq3), 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), poly(N-vinylcarbazole) (PVK), 9,10-bis(naphthalen-2-yl)anthracene (ADN), 4,4',4"-tris(carbazol-9-yl)-triphenylamine (TCTA), 2-tert-butyl-9,10-bis(naphthalen-2-yl)anthracene (TBADN), diphenylstyrylarylidene (DSA), 4,4'-bis(9-carbazolyl)-2,2'-dimethylbiphenyl (CDBP), 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN), hexaphenylcyclotriphosphazene (CP1), 1,4-bis(triphenylsilyl)benzene (UGH2), hexaphenylcyclotrisiloxane (DPSiO3), octaphenylcyclotetrasiloxane (DPSiO4), and the like.

[0092] Specifically, the first host material and the second host material can be selected from any one or a combination of the following compounds:

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101] The lowest unoccupied molecular orbital energy level and the highest occupied molecular orbital energy level of the exciplex are derived from the first host material and the second host material, respectively. Therefore, the energy difference of the exciplex is smaller than the energy difference of the first host material molecule and the energy difference of the second host material molecule, that is, the wavelength of the light emitted by the exciplex is larger than the wavelength of the light emitted by the first host material molecule and the wavelength of the light emitted by the second host material molecule. The emission band of the exciplex is closer to the absorption band in the absorption spectrum of the guest material that is most helpful for light emission (i.e., the absorption at the absorption wavelength at which the guest material molecule directly transitions from the singlet ground state to the first excited triplet state and the absorption near the absorption wavelength) than the emission band of the first host material and the emission band of the second host material. Therefore, the formation of the exciplex is beneficial to improving the efficiency of energy transfer to the guest material molecule.

[0102] For the organometallic compound, the absorption at the absorption wavelength at which the guest material molecule directly transitions from the singlet ground state to the first excited triplet state and the absorption near the absorption wavelength often occur in the range of 400 nm to 550 nm, and in this wavelength range, there are 3 MLCT (metal-to-ligand charge transfer) triplet transitions, and possibly existing triplet π-π * transitions, singlet 1 MLCT transitions, and the like. Therefore, the absorption spectrum of the guest material molecule and the absorption spectrum of the auxiliary material molecule in the range of 400 nm to 550 nm exhibit a wide absorption band. Meanwhile, in the present embodiment, there is a route in which the exciplex transfers energy to the auxiliary material, and then the auxiliary material transfers energy to the guest material. Therefore, the overlap of the emission spectrum of the exciplex with the absorption spectrum of the auxiliary material and the absorption spectrum of the guest material in the range of 400 nm to 550 nm is beneficial to improving the efficiency of energy transfer to the guest material and prolonging the lifetime of the light-emitting element.

[0103] Preferably, the first absorption band of the auxiliary material in the range of 400 nm to 550 nm overlaps with the second absorption band of the guest material in the range of 400 nm to 550 nm, and the exciplex has a first emission band in the range of 400 nm to 550 nm; wherein the first emission band at least partially overlaps with the first absorption band, the first emission band at least partially overlaps with the second absorption band, and the first absorption band at least partially overlaps with the second absorption band.

[0104] When the first emission band overlaps with the first absorption band and the second absorption band in the range of 400 nm to 550 nm, at the first temperature, the exciplex has a first emission peak, and the peak wavelength of the first emission peak can be less than 400 nm or greater than 550 nm, or the peak wavelength of the first emission peak can be between 400 nm and 550 nm. When the peak wavelength of the first emission peak is between 400 nm and 550 nm, the first emission band overlaps with the first absorption band and the second absorption band to a greater extent, which is beneficial to improving the efficiency of energy transfer to the guest material. The first temperature can be room temperature.

[0105] Considering that the exciplex needs to be driven by a driving voltage, the smaller the peak wavelength of the emission peak of the exciplex, the greater the driving voltage required to excite the first host material and the second host material to form the exciplex. Therefore, while the energy transfer occurs, the greater the peak wavelength of the emission peak of the exciplex, the more beneficial it is to reduce the driving voltage of the light-emitting element. Therefore, the auxiliary material has a first absorption peak in the range of 400 nm to 550 nm, the guest material has a second absorption peak in the range of 400 nm to 550 nm, the peak wavelength of the first absorption peak is less than the peak wavelength of the second absorption peak; at the first temperature, the exciplex has a first emission peak, and the peak wavelength of the first emission peak is greater than or equal to the peak wavelength of the second absorption peak. On this basis, in order to ensure the degree of overlap of the first emission band with the first absorption band and the second absorption band, preferably, at the first temperature, the difference between the peak wavelength of the first emission peak and the peak wavelength of the first absorption peak is greater than or equal to 60 nm, and the difference between the peak wavelength of the first emission peak and the peak wavelength of the second absorption peak is less than or equal to 30 nm.

[0106] Please refer to Figure 3 The present application provides a light-emitting element, comprising:

[0107] a pair of electrodes comprising a first electrode and a second electrode;

[0108] The light-emitting layer 105 is located between the pair of electrodes.

[0109] The first host material is a hole-transporting organic compound, and the second host material is an electron-transporting organic compound. The first host material includes an aromatic amine compound or a carbazole compound, and the second host material includes a heteroaromatic compound.

[0110] In this embodiment, the pair of electrodes includes a first electrode 101 and a second electrode 109. The first electrode 101 is an anode, and the second electrode 109 is a cathode.

[0111] The first electrode 101 is preferably at least one of a metal, an alloy, and a conductive compound. Specifically, the first electrode 101 can be a metal oxide such as indium tin oxide, indium zinc oxide, indium zinc tungsten oxide, indium tin zinc oxide, or zinc oxide, or can be graphene, gold, platinum, nickel, tungsten, chromium, molybdenum, or a nitride of a metal material. The thickness of the first electrode 101 is preferably 960 angstroms to 1440 angstroms, and more preferably 1100 angstroms, 1200 angstroms, or 1300 angstroms.

[0112] The second electrode 109 preferably uses a material having a work function lower than that of the first electrode 101. The second electrode 109 is preferably at least one of a metal, an alloy, and a conductive compound. Specifically, the second electrode 109 can include an alkali metal element, an alkaline earth metal element, and a rare earth metal element such as Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, Yb, W, or a magnesium-silver alloy, an aluminum-lithium alloy, or the like. Alternatively, the second electrode 109 can be selected from indium tin oxide, indium zinc oxide, zinc oxide, indium tin zinc oxide, and the like, and a combination of the aforementioned optional materials for the second electrode 109. The thickness of the second electrode 109 is preferably 112 angstroms to 168 angstroms, and more preferably 130 angstroms, 140 angstroms, or 150 angstroms.

[0113] The holes generated by the first host material and the electrons generated by the second host material are recombined, which is an important way of generating the exciplex. The mobility of the first host material and the mobility of the second host material are controlled within a certain range, which is conducive to the matching of the holes and the electrons for generating the exciplex and avoids the reduction of the light-emitting efficiency of the light-emitting element.

[0114] In some embodiments, the ratio of the mobility of the first host material to the mobility of the second host material is from 1:1 to 21:1. The first host material is a material with hole transport properties, and its mobility is the hole mobility; the second host material is a material with electron transport properties, and its mobility is the electron mobility.

[0115] Specifically, the mobility of the first host material is 6.4*10^(-8)[m 2 / (V·s)] to 1.93*10^(-7)[m 2 [ / (V·s)], preferably, the migration rate of the first host material is 1.29*10^(-7)[m 2 / (V·s)] to 1.93*10^(-7)[m 2 More preferably, the mobility of the first host material is 1.61 * 10^(-7) [m]. 2 / (V·s)].

[0116] The mobility of the second host material is 6.4*10^(-8)[m 2 / (V·s)] to 1.93*10^(-7)[m 2 / (V·s)], preferably, the migration rate of the second host material is 6.4*10^(-8)[m 2 / (V·s)] to 9.6*10^(-8)[m 2 More preferably, the mobility of the second host material is 8*10^(-8)[m] / (V·s)]. 2 / (V·s)].

[0117] When the migration rate of the first host material is within the above range, especially 1.61*10^(-7)[m 2 When the migration rate of the second host material is within the above range, especially 8*10^(-8)[m], the migration rate of the second host material is within the above range, especially 8*10^(-8)[m]. 2 When the light-emitting layer 105 is at a ratio of / (V·s), the matching effect between holes and electrons used to generate the excimer complex is optimal, which is most conducive to improving the luminous efficiency of the light-emitting element.

[0118] The ratio of the first host material to the second host material affects the ratio of holes and free electrons generated by the light-emitting layer 105. In order to achieve the matching of holes and electrons used to generate the excimer compound, controlling the doping ratio of the first host material to the second host material is also beneficial to ensure that the matching of holes and electrons used to generate the excimer compound is not unbalanced, thereby avoiding a reduction in the luminous efficiency of the light-emitting element.

[0119] In some embodiments, the doping ratio of the first host material to the second host material is 5:5 to 7:3, such as 5.5:4.5, 5.9:4.1, 6:4, 6.5:3.5, 6.8:3.2, 7:3, etc. Preferably, the doping ratio of the first host material to the second host material is 7:3, 6:4 or 5:5, and most preferably, the doping ratio of the first host material to the second host material is 7:3. The doping ratio of the first host material to the second host material refers to the ratio of the volume of the first host material in the light-emitting layer 105 to the volume of the second host material in the light-emitting layer 105.

[0120] Referring to Figure 4 , the light-emitting element further includes:

[0121] a hole transport layer 103 between the first electrode 101 and the light-emitting layer 105;

[0122] an electron transport layer 107 between the light-emitting layer 105 and the second electrode 109;

[0123] wherein the ratio of the mobility of the first hole transport layer 103 to the electron transport layer 107 is 5-200.

[0124] The hole transport layer 103 includes a material having a hole transport property, for example: a phthalocyanine compound (such as copper phthalocyanine), N1,N1'-([1,1'-biphenyl]-4,4'-diyl)bis(N1-phenyl-N4,N4-di-m-tolylbenzene-1,4-diamine) (DNTPD), 4,4',4"-[tris(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), 4,4',4"-tris(N,N-diphenylamino)triphenylamine (TDATA), 4,4',4"-tris[N(2-naphthyl)-N-phenylamino]-triphenylamine (2-TNATA), poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT / PSS), polyaniline / dodecylbenzenesulfonic acid (PANI / DBSA), polyaniline / camphorsulfonic acid (PANI / CSA), polyaniline / poly(4-styrenesulfonate) (PANI / PSS), N,N-bis(naphthalen-1-yl)-N,N-diphenylbenzidine (NPB), triphenylamine-containing polyether ketone (TPAPEK), 4-isopropyl-4'-methyl diphenyl iodonium [tetrakis(pentafluorophenyl)borate], dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HATCN); carbazole derivatives such as N-phenylcarbazole and polyvinylcarbazole, fluorene derivatives; triphenylamine derivatives such as N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4,4'-diamine (TPD) and 4,4',4"-tris(N-carbazolyl)triphenylamine (TCTA), N,N'-di(naphthalen-1-yl)-N,N'-diphenylbenzidine (NPB), 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC), 4,4'-bis[N,N'-(3-methylphenyl)amino]-3,3'-dimethylbiphenyl (HMTPD), 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi), 9-phenyl-9H-3,9'-bicarbazole (CCP), 1,3-bis(N-carbazolyl)benzene (mCP), 1,3-bis(1,8-dimethyl-9H-carbazol-9-yl)benzene (mDCP), and the like; a combination of the aforementioned compounds having a hole transport property. The thickness of the hole transport layer 103 is preferably 1040 angstroms to 1560 angstroms, more preferably 1200 angstroms, 1300 angstroms, or 1400 angstroms.

[0125] The electron transport layer 107 includes a material having electron transport properties, such as tris(8-hydroxyquinoline)aluminum (Alq3), 1,3,5-tris[(3-pyridyl)-phen-3-yl]benzene, 2,4,6-tris(3'-(pyridine-3-yl)biphenyl-3-yl)-1,3,5-triazine, 2-(4-(N-phenylbenzoimidazole-1-yl)phenyl)-9,10-dinaphthylanthracene, 1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen), 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), 4-(naphthalene-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ), 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD), Liq, BAlq, Bebq2, 9,10-di(naphthalene-2-yl)anthracene (ADN), 1,3-bis[3,5-di(pyridine-3-yl)phenyl]benzene (BmPyPhB); halogenated metals such as LiF, NaCl, CsF, RbCl, RbI, CuI, KI, lanthanide metals such as Yb, and co-deposited materials of the above halogenated metals and lanthanide metals; metal oxides such as Li2O, BaO; combinations of the aforementioned materials having electron transport properties. Alternatively, the electron transport layer 107 can be formed of a mixture material of an electron transport material and an insulating organic metal salt, which can include, for example, a metal acetate, a metal benzoate, a metal acetylacetate, a metal acetylacetonate, or a metal stearate. The thickness of the electron transport layer 107 is preferably 240 angstroms to 420 angstroms, more preferably 300 angstroms or 350 angstroms.

[0126] During the light emission of the light emitting element, holes are transported from the hole transport layer 103 to the light emitting layer 105 and electrons are transported from the electron transport layer 107 to the light emitting layer 105. Therefore, controlling the ratio of the mobility of the hole transport layer 103 to the mobility of the electron transport layer 107 is advantageous for controlling the matching degree of holes and electrons used to generate the exciplex, thereby avoiding a reduction in the light emission efficiency of the light emitting element.

[0127] The mobility of the hole transport layer 103 is a hole mobility, and the mobility of the electron transport layer 107 is an electron mobility. Preferably, the mobility of the hole transport layer 103 is 1-10*10^(-4) [m / (V·s)], and the mobility of the electron transport layer 107 is 5*10^(-6)-2*10^(-5) [m / (V·s)]. 2 2 ​​

[0128] The thickness of the hole transport layer 103 and the electron transport layer 107 affects the ratio of the number of holes and free electrons transported to the light-emitting layer 105. To achieve a match of holes and electrons for generating the exciplex, it is advantageous to control the ratio of the thickness of the hole transport layer 103 and the electron transport layer 107, so as to avoid imbalance of the match of holes and electrons for generating the exciplex, thereby avoiding reduction of the light-emitting efficiency of the light-emitting element.

[0129] In some embodiments, the ratio of the thickness of the hole transport layer 103 and the thickness of the electron transport layer 107 is 3.5:1 to 5.5:1, such as 3.6:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, 5:1, 5.2:1, or the like; preferably, the ratio of the thickness of the hole transport layer 103 and the thickness of the electron transport layer 107 is 4:1.

[0130] In the light-emitting element, the mobility of the first host material, the second host material, the electron transport layer 107, and the hole transport layer 103 can be obtained by SCLC (Space-Charge-Limited-Current) test. Specifically, the test results are combined with Mott-Gurney equation and Frenkel effect: Taking the logarithm of both sides, we have: It can be seen that there is a linear relationship between In(J / E2) and μ. The function graph of In(J / E2) with μ is drawn, and the carrier zero-field mobility of the organic material is calculated according to the intercept of the straight line. After being brought into the Poole-Frenkel formula, the field-dependent mobility of the carrier under a fixed electric field can be obtained.

[0131] Please refer to Figure 5 The light-emitting element further comprises:

[0132] A first barrier layer 104 between the hole transport layer 103 and the light-emitting layer 105;

[0133] The difference between the highest occupied molecular orbital energy level of the first barrier layer 104 and the highest occupied molecular orbital energy level of the exciplex is less than 0.3 eV.

[0134] The first barrier layer 104 directly contacts the light-emitting layer 105 and the hole transport layer 103. The material of the first barrier layer 104 can be selected from the same range as the material of the hole transport layer 103. In the same light-emitting element, the material of the first barrier layer 104 can be different from the material of the hole transport layer 103. Preferably, the material of the first barrier layer 104 includes an aromatic amine compound, such as a triarylamine compound. The thickness of the light-emitting element of different colors is different, so as to adjust the microcavity of the light-emitting element of different colors, so that the light-emitting efficiency of the light-emitting element is effectively improved. Therefore, when the light-emitting element is a blue light-emitting element, the thickness of the first barrier layer 104 is preferably 40 angstroms to 60 angstroms, more preferably 45 angstroms, 50 angstroms, or 55 angstroms; when the light-emitting element is a green light-emitting element, the thickness of the first barrier layer 104 is preferably 320 angstroms to 480 angstroms, more preferably 350 angstroms, 400 angstroms, or 450 angstroms; when the light-emitting element is a red light-emitting element, the thickness of the first barrier layer 104 is preferably 720 angstroms to 1080 angstroms, more preferably 850 angstroms, 900 angstroms, or 950 angstroms.

[0135] The difference between the highest occupied molecular orbital energy level of the first barrier layer 104 and the highest occupied molecular orbital energy level of the exciplex is less than 0.3 eV, which is conducive to the transmission of holes from the first barrier layer 104 to the light-emitting layer 105 and reduces the driving voltage of the light-emitting element.

[0136] In some embodiments, the difference between the lowest unoccupied molecular orbital energy level of the first barrier layer 104 and the lowest unoccupied molecular orbital energy level of the exciplex is greater than 0.05 eV, which is conducive to the blocking effect of the first barrier layer 104 on the electrons from the light-emitting layer 105 to the first barrier layer 104.

[0137] In some embodiments, the difference between the highest occupied molecular orbital energy level of the hole transport layer 103 and the highest occupied molecular orbital energy level of the first barrier layer 104 is less than 0.3 eV, which is conducive to the transmission of holes from the hole transport layer 103 to the first barrier layer 104 and reduces the driving voltage of the light-emitting element.

[0138] Preferably, the difference between the lowest unoccupied molecular orbital energy level of the hole transport layer 103 and the lowest unoccupied molecular orbital energy level of the first barrier layer 104 is greater than 0.05 eV, which is conducive to the blocking effect of the hole transport layer 103 on the electrons from the first barrier layer 104 to the hole transport layer 103.

[0139] In some embodiments, the difference between the first excited triplet energy level of the first blocking layer 104 and the first excited triplet energy level of the exciplex is greater than 0.15 eV, which facilitates energy transfer from the first blocking layer 104 to the exciplex, and reduces the driving voltage of the light-emitting element.

[0140] In some embodiments, the electron-transporting layer 107 is in direct contact with the light-emitting layer 105, and the difference between the lowest unoccupied molecular orbital energy level of the electron-transporting layer 107 and the lowest unoccupied molecular orbital energy level of the exciplex is less than 0.3 eV, which facilitates the blocking of holes from the light-emitting layer 105 to the electron-transporting layer 107.

[0141] In some embodiments, the difference between the first excited triplet energy level of the electron-transporting layer 107 and the first excited triplet energy level of the exciplex is greater than 0.05 eV, which facilitates energy transfer from the electron-transporting layer 107 to the exciplex, and reduces the driving voltage of the light-emitting element.

[0142] In some embodiments, the light-emitting element further comprises a second blocking layer 106 between the light-emitting layer 105 and the electron-transporting layer 107, and the difference between the lowest unoccupied molecular orbital energy level of the second blocking layer 106 and the lowest unoccupied molecular orbital energy level of the exciplex is less than 0.3 eV, which facilitates the transfer of electrons from the second blocking layer 106 to the light-emitting layer 105, and reduces the driving voltage of the light-emitting element. The second blocking layer 106 is in direct contact with the light-emitting layer 105 and the electron-transporting layer 107, and the material selection range of the second blocking layer 106 is the same as that of the electron-transporting layer 107. In the same light-emitting element, the material of the second blocking layer 106 is different from that of the electron-transporting layer 107. Preferably, the material of the second blocking layer 106 can be a heteroaromatic compound, such as a triazinopyrimidine derivative. The thickness of the second blocking layer 106 is preferably 40 angstroms to 60 angstroms, more preferably 45 angstroms, 50 angstroms, or 55 angstroms, which facilitates the control of the distance between the light-emitting layer 105 and the second electrode 109.

[0143] Preferably, the difference between the lowest unoccupied molecular orbital energy level of the electron-transporting layer 107 and the lowest unoccupied molecular orbital energy level of the second blocking layer 106 is less than 0.3 eV, which facilitates the transfer of electrons from the electron-transporting layer 107 to the second blocking layer 106, and reduces the driving voltage of the light-emitting element.

[0144] In some embodiments, the difference between the first excited triplet energy level of the second barrier layer 106 and the first excited triplet energy level of the exciplex is greater than 0.05 eV, which facilitates energy transfer from the second barrier layer 106 to the exciplex, and reduces the driving voltage of the light-emitting element.

[0145] In some embodiments, the difference between the highest occupied molecular orbital energy level of the second barrier layer 106 and the highest occupied molecular orbital energy level of the exciplex is greater than 0.3 eV, preferably, the difference between the highest occupied molecular orbital energy level of the second barrier layer 106 and the highest occupied molecular orbital energy level of the exciplex is greater than 0.4 eV, more preferably, the difference between the highest occupied molecular orbital energy level of the second barrier layer 106 and the highest occupied molecular orbital energy level of the exciplex is greater than 0.5 eV, which facilitates blocking of holes moving from the light-emitting layer 105 to the second barrier layer, and improves the light-emitting efficiency of the light-emitting element.

[0146] In the above light-emitting element, a hole injection layer 102 can be further included between the first electrode 101 and the hole transport layer 103. The hole injection layer 102 includes a material having a hole injection property, such as a metal oxide such as molybdenum oxide, titanium oxide, tungsten oxide, silver oxide, or the like; a phthalocyanine-based compound such as copper phthalocyanine or the like; a carbazole derivative such as N-phenylcarbazole and polyvinylcarbazole, a fluorene derivative, a triphenylamine derivative such as N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4,4'-diamine (TPD) and 4,4',4"-tris(N-carbazolyl)triphenylamine (TCTA), N,N'-di(naphthalen-1-yl)-N,N'-diphenylbenzidine (NPB), 4,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine] (TAPC), 4,4'-bis[N,N'-(3-methylphenyl)amino]-3,3'-dimethylbiphenyl (HMTPD), 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi), 9-phenyl-9H-3,9'-bicarbazole (CCP), 1,3-bis(N-carbazolyl)benzene (mCP), 1,3-bis(1,8-dimethyl-9H-carbazol-9-yl)benzene (mDCP), or the like, or a combination thereof. The material having a hole injection property in the hole injection layer 102 is doped in the hole injection layer 102 at a doping ratio of 1% to 3% (volume fraction). The thickness of the hole injection layer 102 is preferably 80 angstroms to 120 angstroms, more preferably 90 angstroms, 100 angstroms, or 110 angstroms.

[0147] The light emitting element can further include an electron injection layer 108 between the electron transport layer 107 and the second electrode 109. The electron injection layer 108 includes a material having electron injection properties, such as an alkali metal, an alkaline earth metal, a rare earth metal, or an alkali metal compound, an alkaline earth metal compound, a rare earth metal compound, and the like, such as lithium, lithium fluoride, lithium oxide, calcium fluoride, ytterbium, Liq, KI, NaCl, CsF, Li2O, BaO, and the like. The thickness of the electron injection layer 108 is preferably 8 angstroms to 12 angstroms, more preferably 9 angstroms, 10 angstroms, or 11 angstroms. The work function of the electron injection layer 108 is lower than the work function of the second electrode 109, which facilitates the injection of electrons into the electron transport layer 107.

[0148] The light emitting element can further include a capping layer on the second electrode 109. The capping layer can be an organic material or an inorganic material. When the capping layer is an inorganic material, the inorganic material can include an alkali metal compound, such as LiF, or an alkaline earth metal compound, such as MgF2, SiON, SiNx, SiOy, and the like, or a combination thereof. When the capping layer is an organic material, the organic material can include α-NPD, NPB, TPD, m-MTDATA, Alq3, CuPc, N4, N4, N4', N4'-Tetrakis(3-methyl-4-phenylphenyl)amorphous (TPD15), 4,4',4"-tris(9H-carbazol-9-yl)-phenylamine (TCTA), and the like, an epoxy resin, or an acrylate (such as a methacrylate), or a combination thereof.

[0149] The light emitting element can further include a capping layer on the second electrode 109. The capping layer can be an organic material or an inorganic material. When the capping layer is an inorganic material, the inorganic material can include an alkali metal compound, such as LiF, or an alkaline earth metal compound, such as MgF2, SiON, SiNx, SiOy, and the like, or a combination thereof. When the capping layer is an organic material, the organic material can include α-NPD, NPB, TPD, m-MTDATA, Alq3, CuPc, N4, N4, N4', N4'-Tetrakis(3-methyl-4-phenylphenyl)amorphous (TPD15), 4,4',4"-tris(9H-carbazol-9-yl)-phenylamine (TCTA), and the like, an epoxy resin, or an acrylate (such as a methacrylate), or a combination thereof. Figure 6 The light emitting element can further include a capping layer on the second electrode 109. The capping layer can be an organic material or an inorganic material. When the capping layer is an inorganic material, the inorganic material can include an alkali metal compound, such as LiF, or an alkaline earth metal compound, such as MgF2, SiON, SiNx, SiOy, and the like, or a combination thereof. When the capping layer is an organic material, the organic material can include α-NPD, NPB, TPD, m-MTDATA, Alq3, CuPc, N4, N4, N4', N4'-Tetrakis(3-methyl-4-phenylphenyl)amorphous (TPD15), 4,4',4"-tris(9H-carbazol-9-yl)-phenylamine (TCTA), and the like, an epoxy resin, or an acrylate (such as a methacrylate), or a combination thereof.

[0150] a pair of electrodes including a first electrode 101 and a second electrode 109;

[0151] a light emitting layer 105 between the pair of electrodes, the light emitting layer 105 including a first sub light emitting layer 113 and a second sub light emitting layer 120 between the first sub light emitting layer 113 and the second electrode 109;

[0152] a first hole transport layer 111 between the first electrode 101 and the first sub light emitting layer 113;

[0153] a first sub blocking layer 112 between the first hole transport layer 111 and the first sub light emitting layer 113;

[0154] a first electron transport layer 122 between the second sub light emitting layer 120 and the second electrode 109;

[0155] a second sub-blocking layer 121 located between the second sub-emitting layer 120 and the first electron transport layer 122;

[0156] a third sub-blocking layer 114 located on the side of the first sub-emitting layer 113 close to the second sub-emitting layer 120;

[0157] a second electron transport layer 115 located on the side of the third sub-blocking layer 114 close to the second sub-emitting layer 120;

[0158] a first charge generation layer 116 located on the side of the second electron transport layer 115 close to the second sub-emitting layer 120;

[0159] a second charge generation layer 117 located on the side of the first charge generation layer 116 close to the second sub-emitting layer 120;

[0160] a second hole transport layer 118 located on the side of the second charge generation layer 117 close to the second sub-emitting layer 120;

[0161] a fourth sub-blocking layer 119 located between the second hole transport layer 118 and the second sub-emitting layer 120;

[0162] a hole injection layer 102 located between the first electrode 101 and the first hole transport layer 111;

[0163] an electron injection layer 108 located between the second electrode 109 and the first electron transport layer 122.

[0164] In the direction from the first electrode 101 to the second electrode 109, the hole injection layer 102, the first hole transport layer 111, the first sub-blocking layer 112, the first sub-emitting layer 113, the third sub-blocking layer 114, the second electron transport layer 115, the first charge generation layer 116, the second charge generation layer 117, the second hole transport layer 118, the fourth sub-blocking layer 119, the second sub-emitting layer 120, the second sub-blocking layer 121, the first electron transport layer 122, and the electron injection layer 108 are sequentially stacked and contact each other.

[0165] In this embodiment, the first hole transport layer 111, the second hole transport layer 118, and the "hole transport layer" in the aforementioned light-emitting element have the same or similar functions, and thus the material having a hole-transport property and the range of materials to be selected as the material having a hole-transport property are the same. Further, the first hole transport layer 111 and the first sub-blocking layer 112, and the second hole transport layer 118 and the fourth sub-blocking layer 119 have the same range of difference between the highest occupied molecular orbital level and the lowest unoccupied molecular orbital level as the "hole transport layer" and the "first blocking layer" in the aforementioned light-emitting element.

[0166] In this embodiment, the first electron transport layer 122, the second electron transport layer 115, and the "electron transport layer" in the aforementioned light-emitting element have the same or similar functions, and thus the material having an electron-transport property and the range of materials to be selected as the material having an electron-transport property are the same. Further, the first electron transport layer 122 and the second sub-blocking layer 121, and the second electron transport layer 115 and the third sub-blocking layer 114 have the same range of difference between the highest occupied molecular orbital level and the lowest unoccupied molecular orbital level as the "electron transport layer" and the "second blocking layer" in the aforementioned light-emitting element.

[0167] In this embodiment, the first sub-blocking layer 112 and the fourth sub-blocking layer 119 have the same function as the "first blocking layer" in the aforementioned light-emitting element, and thus the range of materials to be selected is the same. Further, the first sub-blocking layer 112 and the first sub-light-emitting layer 113, and the fourth sub-blocking layer 119 and the second sub-light-emitting layer 120 have the same range of difference between the highest occupied molecular orbital level and the lowest unoccupied molecular orbital level, the difference between the first excited triplet energy level as the "first blocking layer" and the "excited complex" in the aforementioned light-emitting element.

[0168] In this embodiment, the second sub-blocking layer 121 and the third sub-blocking layer 114 have the same function as the "second blocking layer" in the aforementioned light-emitting element, and thus the range of materials to be selected is the same. Further, the second sub-blocking layer 121 and the second sub-light-emitting layer 120, and the third sub-blocking layer 114 and the first sub-light-emitting layer 113 have the same range of difference between the highest occupied molecular orbital level and the lowest unoccupied molecular orbital level, the difference between the first excited triplet energy level as the "second sub-blocking layer" and the "excited complex" in the aforementioned light-emitting element.

[0169] In the embodiment, the thickness of the first charge generation layer 116 can be 80-120 angstroms, preferably 90-110 angstroms, and more preferably 100 angstroms. The first charge generation layer 116 includes a first charge-doped material and a second charge-doped material, the selection range of the first charge-doped material is the same as the selection range of the material having electron transport property in the "electron transport layer" of the aforementioned light emitting element, and the selection range of the second charge-doped material is the same as the selection range of the material having electron injection property in the "charge injection layer" of the aforementioned light emitting element. In the first charge generation layer 116, the doping ratio of the first charge-doped material to the second charge-doped material is 85:15 to 96:4, such as 88:12, 90:10, 92:8, 95:5, and the like, and preferably 95:5. Here, the doping ratio refers to the ratio of the volume occupied by the first charge-doped material to the volume occupied by the second charge-doped material in the first charge generation layer 116.

[0170] In the embodiment, the thickness of the second charge generation layer 117 can be 80-120 angstroms, preferably 90-110 angstroms, and more preferably 100 angstroms. The second charge generation layer 117 includes a third charge-doped material and a fourth charge-doped material, the selection range of the third charge-doped material is the same as the selection range of the material having hole transport property in the "hole transport layer" of the aforementioned light emitting element, and the selection range of the fourth charge-doped material is the same as the selection range of the material having hole injection property in the "hole injection layer" of the aforementioned light emitting element. In the second charge generation layer 117, the doping ratio of the third charge-doped material to the fourth charge-doped material is 85:15 to 96:4, such as 88:12, 90:10, 92:8, 95:5, and the like, and preferably 95:5. Here, the doping ratio refers to the ratio of the volume occupied by the third charge-doped material to the volume occupied by the fourth charge-doped material in the second charge generation layer 117.

[0171] Please refer to Figures 7 to 9 , the first host material, the second host material, the auxiliary material, and the guest material of the light emitting element provided by the embodiment of the present application are illustrated as follows:

[0172] The structural formula of the first host material and the second host material is as follows:

[0173] The first host material is as follows: The second host material is as follows:

[0174] The structural formula of the auxiliary material is as follows:

[0175] The structure of the guest material is as follows:

[0176] Referring to Figure 7 In the embodiment, the first excited triplet energy level of the exciplex formed by the first host material and the second host material, the auxiliary material and the guest material is shown in the figure, which indicates that the first excited triplet energy level of the auxiliary material is lower than that of the exciplex, and the first excited triplet energy level of the auxiliary material is higher than that of the guest material. The above results are obtained by converting the peak wavelength of the emission peak obtained in THF solution at 77K.

[0177] Referring to Figure 8 In the embodiment, the HOMO, LUMO, and the energy difference between HOMO and LUMO of the first host material, the second host material, the auxiliary material and the guest material are shown in the figure. Among them, the HOMO energy level of the first host material, the second host material, the auxiliary material and the guest material increases in turn, and the LUMO energy level of the first host material, the second host material, the auxiliary material and the guest material decreases in turn; the energy difference between HOMO and LUMO of the first host material and the second host material is greater than that of the auxiliary material, and the energy difference between HOMO and LUMO of the auxiliary material is greater than that of the guest material.

[0178] Referring to Figure 9 In the embodiment, the exciplex (indicated as "Exciplex" in the figure) formed by the first host material and the second host material has a wide emission spectrum in the range of 375 nanometers to 625 nanometers when the concentration is 0.01 mmol / L in dichloromethane solvent, and the peak wavelength of the emission spectrum is 504 nanometers.

[0179] The auxiliary material (indicated as "AST" in the figure) has an emission spectrum in the range of 475 nanometers to 625 nanometers when the concentration is 0.01 mmol / L in dichloromethane solvent, and the peak wavelength of the emission spectrum is 530 nanometers; at the same time, the absorption spectrum of the auxiliary material in the same solvent and the same concentration shows that it has a wide absorption band in the range of 400 nanometers to 550 nanometers compared with other wavelength ranges.

[0180] The guest material (indicated as "GD" in the figure) has an emission spectrum in the range of 500 nm to 625 nm with a peak wavelength of 536 nm when the concentration of the guest material in dichloromethane solvent is 0.01 mmol / L. Meanwhile, the absorption spectrum of the guest material in the same solvent and at the same concentration shows that the guest material has a wide absorption band in the range of 400 nm to 550 nm compared to other wavelength ranges.

[0181] The performance parameters of a light emitting element using the above-mentioned first host material, second host material, auxiliary material, and guest material combination as a light emitting layer are as follows:

[0182] Specifically, the material of the hole transport layer of the light emitting element is:

[0183] The material of the first barrier layer is:

[0184] The material of the second barrier layer is:

[0185] The material of the electron transport layer is:

[0186] Please refer to Figure 10 , the light emitting spectrum test results of the device after the first mixture (indicated as "Exciplex+GD") of the first host material, the second host material, and the guest material is used as a light emitting layer, the light emitting spectrum test results of the device after the second mixture (indicated as "Exciplex+AST") of the first host material, the second host material, and the auxiliary material is used as a light emitting layer, and the light emitting spectrum test results of the device after the third mixture (indicated as "Exciplex+GD+AST") of the first host material, the second host material, the auxiliary material, and the guest material is used as a light emitting layer, the results of the three show that the light emission of the light emitting element with the third mixture as a light emitting layer mainly comes from the guest material, which indirectly indicates the existence of the energy transfer path from the auxiliary material to the guest material. In the first mixture, the volume ratio of the first host material: the second host material: the guest material is 47:47:6, in the second mixture, the volume ratio of the first host material: the second host material: the auxiliary material is 47:47:6, and in the third mixture, the volume ratio of the first host material: the second host material: the auxiliary material: the guest material is 44:44:6:6.

[0187] Please refer to Figure 11Further, the first host material, the second host material, the auxiliary material and the guest material are combined as the light-emitting layer of the light-emitting element in different doping ratios, and the light-emitting life of the light-emitting element is shown in the figure. Wherein, Ref (only GD) represents the first light-emitting layer without adding auxiliary dopant, GD: AST (6:1) is the second light-emitting layer, GD: AST (6:2) is the third light-emitting layer, GD: AST (6:4) is the fourth light-emitting layer, GD: AST (6:6) is the fifth light-emitting layer, and GD: AST (6:8) is the sixth light-emitting layer. In the first light-emitting layer to the sixth light-emitting layer, the volume ratio of the first host material, the second host material, the auxiliary material and the guest material is respectively: 47:47:6; 46.5:46.5:6:1; 46:46:6:2; 45:45:6:4; 44:44:6:6; 43:43:6:8. As can be seen from the figure, with the addition of the auxiliary dopant, the light-emitting life of the light-emitting element is significantly increased.

[0188] The embodiment of the present application increases the path of energy transfer from the exciplex to the guest material by adding the auxiliary material, and the first excited triplet energy level of the auxiliary material is between the first excited triplet energy level of the exciplex and the first excited triplet energy level of the guest material, reduces the energy loss in the energy transfer process, ensures the light-emitting efficiency of the light-emitting element and prolongs the service life of the light-emitting element.

[0189] The embodiment of the present application also discloses a display panel, which comprises the light-emitting element as any of the above.

[0190] The display panel further comprises an array substrate located on one side of the light-emitting element, and an encapsulation layer located on the side of the light-emitting element away from the array substrate and covering the light-emitting element.

[0191] The display panel further comprises a polarizer layer located on the side of the encapsulation layer away from the light-emitting element and a cover plate layer located on the side of the polarizer layer away from the light-emitting element. Wherein, the polarizer layer can be replaced by a color film layer, and the color film layer can comprise a plurality of color resist and a black matrix located on both sides of the color resist.

[0192] In some embodiments, the display panel comprises a red light-emitting element, a green light-emitting element and a blue light-emitting element, and at least one of the red light-emitting element, the green light-emitting element and the blue light-emitting element adopts the light-emitting element as any of the above; preferably, the red light-emitting element, the green light-emitting element and the blue light-emitting element all adopt the light-emitting element as any of the above, which is conducive to improving the overall light-emitting efficiency of the display panel and prolonging the service life of the display panel.

[0193] The display panel disclosed by the embodiment of the present application increases the path of energy transfer from the exciplex to the guest material by adding the auxiliary material, reduces the energy loss in the energy transfer process, ensures the light emitting efficiency of the light emitting element, and prolongs the service life of the light emitting element.

[0194] The embodiment of the present application discloses a light emitting layer, a light emitting element and a display panel, the light emitting layer comprising: a first host material, a second host material, a guest material and an auxiliary material; wherein the first host material and the second host material form an exciplex; the first excited triplet energy level of the auxiliary material is lower than the first excited triplet energy level of the exciplex, and the first excited triplet energy level of the auxiliary material is higher than the first excited triplet energy level of the guest material. The embodiment of the present application increases the path of energy transfer from the exciplex to the guest material by adding the auxiliary material, reduces the energy loss in the energy transfer process, ensures the light emitting efficiency of the light emitting element, and prolongs the service life of the light emitting element.

[0195] The above describes the light emitting layer, the light emitting element and the display panel provided by the embodiment of the present application in detail, the principle and the implementation mode of the present application are described by applying specific examples in this paper, the above embodiment is only used for helping to understand the method and the core idea of the present application; meanwhile, for the person skilled in the art, according to the idea of the present application, the specific implementation mode and the application range will be changed, and the above description should not be understood as the limitation of the present application.

Claims

1. A light-emitting layer, characterized in that, include: Primary material, secondary material, object material, and auxiliary material; Wherein, the first host material and the second host material form an excitocomplex; The first excited triplet energy level of the auxiliary material is lower than the first excited triplet energy level of the excitocomplex, and the first excited triplet energy level of the auxiliary material is higher than the first excited triplet energy level of the guest material; At the first temperature, the peak wavelength of the emission peak of the auxiliary material is greater than the peak wavelength of the emission peak of the exopolymer, and the peak wavelength of the emission peak of the auxiliary material is less than the peak wavelength of the emission peak of the guest material. At the first temperature, the difference between the peak wavelength of the emission peak of the auxiliary material and the peak wavelength of the emission peak of the exopolymer is greater than or equal to the difference between the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material. The first temperature is room temperature; The auxiliary material has a first absorption band in the range of 400 nm to 550 nm, and the excitocomplex has a first emission band in the range of 400 nm to 550 nm; the first emission band and the first absorption band at least partially overlap.

2. The light-emitting layer according to claim 1, characterized in that, The highest occupied molecular orbital energy level of the auxiliary material is higher than that of the first host material, the highest occupied molecular orbital energy level of the auxiliary material is higher than that of the second host material, and the highest occupied molecular orbital energy level of the auxiliary material is lower than that of the guest material.

3. The light-emitting layer according to claim 2, characterized in that, The lowest unoccupied molecular orbital energy level of the auxiliary material is lower than that of the first host material, the lowest unoccupied molecular orbital energy level of the auxiliary material is lower than that of the second host material, and the lowest unoccupied molecular orbital energy level of the auxiliary material is higher than that of the guest material.

4. The light-emitting layer according to claim 1, characterized in that, The first excited singlet state energy level of the first host material is higher than the first excited singlet state energy level of the auxiliary material, the first excited singlet state energy level of the second host material is higher than the first excited singlet state energy level of the auxiliary material, and the first excited singlet state energy level of the auxiliary material is higher than the first excited singlet state energy level of the guest material.

5. The light-emitting layer according to claim 1, characterized in that, The first absorption band overlaps with the second absorption band of the guest material in the range of 400 nm to 550 nm. The first emission band and the second absorption band at least partially overlap.

6. The light-emitting layer according to claim 5, characterized in that, The auxiliary material has a first absorption peak in the range of 400 nm to 550 nm, and the guest material has a second absorption peak in the range of 400 nm to 550 nm. The peak wavelength of the first absorption peak is smaller than the peak wavelength of the second absorption peak. At the first temperature, the excitocomplex has a first emission peak, the peak wavelength of which is greater than or equal to the peak wavelength of the second absorption peak.

7. The light-emitting layer according to claim 6, characterized in that, At the first temperature, the difference between the peak wavelength of the first emission peak and the peak wavelength of the first absorption peak is greater than or equal to 60 nanometers, and the difference between the peak wavelength of the first emission peak and the peak wavelength of the second absorption peak is less than or equal to 30 nanometers.

8. The light-emitting layer according to claim 1, characterized in that, At the first temperature, the difference between the peak wavelength of the emission peak of the auxiliary material and the peak wavelength of the emission peak of the excitocomplex is less than or equal to 30 nanometers, and the difference between the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material is less than or equal to 10 nanometers.

9. The light-emitting layer according to claim 1, characterized in that, The auxiliary material and the guest material are each selected from one of the organometallic compounds of platinum, iridium, or osmium.

10. The light-emitting layer according to claim 9, characterized in that, The guest material is an organometallic compound of platinum or iridium, and the auxiliary material is an organometallic compound of platinum or iridium that is different from the guest material; or... The guest material is an organometallic compound of osmium, and the auxiliary material is an organometallic compound of osmium.

11. The light-emitting layer according to claim 1, characterized in that, The first and second main materials account for 80% to 99.8% of the volume fraction of the light-emitting layer, the guest material accounts for 0.1% to 10% of the volume fraction of the light-emitting layer, and the auxiliary material accounts for 0.1% to 10% of the volume fraction of the light-emitting layer.

12. The light-emitting layer according to claim 1, characterized in that, At the first temperature, the peak wavelength of the light emitted by the light-emitting layer is between 500 nanometers and 700 nanometers.

13. The light-emitting layer according to claim 12, characterized in that, At the first temperature, the peak wavelength of the light emitted by the light-emitting layer is between 500 nanometers and 560 nanometers.

14. A light-emitting element, characterized in that, include: A pair of electrodes, including a first electrode and a second electrode; A light-emitting layer located between the pair of electrodes, the light-emitting layer comprising a first host material, a second host material, a guest material, and auxiliary materials; Wherein, the first host material and the second host material form an excitocomplex; The first excited triplet energy level of the auxiliary material is lower than the first excited triplet energy level of the excitocomplex, and the first excited triplet energy level of the auxiliary material is higher than the first excited triplet energy level of the guest material; At the first temperature, the peak wavelength of the emission peak of the auxiliary material is greater than the peak wavelength of the emission peak of the exopolymer, and the peak wavelength of the emission peak of the auxiliary material is less than the peak wavelength of the emission peak of the guest material. At the first temperature, the difference between the peak wavelength of the emission peak of the auxiliary material and the peak wavelength of the emission peak of the exopolymer is greater than or equal to the difference between the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material. The auxiliary material has a first absorption band, and the excitocomplex has a first emission band, wherein the first emission band at least partially overlaps with the first absorption band. The first host material is a hole-transporting organic compound, and the second host material is an electron-transporting compound. The types of the first host material include aromatic amine compounds or carbazole compounds, and the types of the second host material include heteroaromatic compounds.

15. The light-emitting element according to claim 14, characterized in that, The mobility of the first host material is 6.4*10^(-8)[m 2 / (V·s)] to 1.93*10^(-7)[m 2 / (V·s)], the mobility of the second host material is 6.4*10^(-8)[m 2 / (V·s)] to 1.93*10^(-7)[m 2 / (V·s)].

16. The light-emitting element according to claim 15, characterized in that, The doping ratio of the first host material to the second host material is 5:5 to 7:

3.

17. The light-emitting element according to claim 14, characterized in that, The light-emitting element also includes: A hole transport layer located between the first electrode and the light-emitting layer; An electron transport layer located between the light-emitting layer and the second electrode; The ratio of the mobility of the hole transport layer to the mobility of the electron transport layer is 5 to 200.

18. The light-emitting element according to claim 17, characterized in that, The mobility of the hole transport layer is 1*10^(-4)~10*10^(-4)[m 2 / (V·s)], the mobility of the electron transport layer is 5*10^(-6)~2*10^(-5)[m 2 / (V·s)].

19. The light-emitting element according to claim 17, characterized in that, The ratio of the thickness of the hole transport layer to the thickness of the electron transport layer is from 3.5:1 to 5.5:

1.

20. The light-emitting element according to claim 17, characterized in that, The light-emitting element also includes: The first blocking layer is located between the hole transport layer and the light-emitting layer; The difference between the highest occupied molecular orbital energy level of the first barrier layer and the highest occupied molecular orbital energy level of the excitocomplex is less than 0.3 eV.

21. The light-emitting element according to claim 20, characterized in that, The difference between the lowest unoccupied molecular orbital energy level of the first barrier layer and the lowest unoccupied molecular orbital energy level of the excitocomplex is greater than 0.05 eV, the difference between the highest occupied molecular orbital energy level of the hole transport layer and the highest occupied molecular orbital energy level of the first barrier layer is less than 0.3 eV, and the difference between the lowest unoccupied molecular orbital energy level of the hole transport layer and the lowest unoccupied molecular orbital energy level of the first barrier layer is greater than 0.05 eV.

22. The light-emitting element according to claim 20, characterized in that, The electron transport layer is in direct contact with the light-emitting layer. The difference between the lowest unoccupied molecular orbital energy level of the electron transport layer and the lowest unoccupied molecular orbital energy level of the excitocomplex is less than 0.3 eV. The difference between the lowest unoccupied molecular orbital energy level of the electron transport layer and the lowest unoccupied molecular orbital energy level of the first blocking layer is less than 0.3 eV.

23. The light-emitting element according to claim 20, characterized in that, The light-emitting element further includes a second barrier layer located between the light-emitting layer and the electron transport layer, wherein the difference between the lowest unoccupied molecular orbital energy level of the second barrier layer and the lowest unoccupied molecular orbital energy level of the excitocomplex is less than 0.3 eV, and the difference between the lowest unoccupied molecular orbital energy level of the electron transport layer and the lowest unoccupied molecular orbital energy level of the second barrier layer is less than 0.3 eV.

24. A display panel, characterized in that, The display panel includes a light-emitting element as described in any one of claims 14 to 23.

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