WO2024066157A1

WO2024066157A1 - Light-emitting layer, light-emitting element, and display panel

Info

Publication number: WO2024066157A1
Application number: PCT/CN2023/074775
Authority: WO
Inventors: 张宇; 袁莉; 杨杰; 李们在
Original assignee: 武汉华星光电半导体显示技术有限公司
Priority date: 2022-09-26
Filing date: 2023-02-07
Publication date: 2024-04-04
Also published as: CN115513394A

Abstract

Disclosed in the embodiments of the present invention are a light-emitting layer, a light-emitting element, and a display panel. The light-emitting layer comprises: 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; and a first excited triplet state energy level of the auxiliary material is lower than a first excited triplet state energy level of the exciplex, and the first excited triplet state energy level of the auxiliary material is higher than a first excited triplet state energy level of the guest material.

Description

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

Technical Field

The present invention relates to the field of display, and in particular to a light-emitting layer, a light-emitting element and a display panel.

Background technique

At present, organic light-emitting elements have attracted widespread attention in the display field due to their excellent properties such as thinness, light weight, high-speed response to input signals, and DC low-voltage drive. Display panels using organic light-emitting elements have excellent display capabilities, low power consumption, and excellent bending performance. With the development of display panels with organic light-emitting elements and the increase in user demand, the improvement of the luminous efficiency and service life of organic light-emitting elements is a key to improving the competitiveness of display panels including organic light-emitting elements. The luminous efficiency and service life of existing organic light-emitting elements are often in a competitive relationship. Prolonging the life of organic light-emitting elements requires sacrificing the luminous efficiency of organic light-emitting elements. For example, the method of designing and using small singlet-triplet energy gap materials has the problem of torsion of energy transfer between the host material and the guest material, which leads to a decrease in the luminous efficiency of the light-emitting element.

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.

technical problem

The present invention provides a light-emitting layer, a light-emitting element and a display panel, which can alleviate the current technical problem that the light-emitting efficiency of the light-emitting element cannot be guaranteed while the service life of the light-emitting element is increased.

Technical Solutions

To solve the above problems, the technical solutions provided by this application are as follows:

The present invention provides a light-emitting layer, comprising:

a pair of electrodes;

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;

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.

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 main 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 main 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.

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 main 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 main 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.

Preferably, the first excited singlet energy level of the first main material is higher than the first excited singlet energy level of the auxiliary material, the first excited singlet energy level of the second main material is higher than the first excited singlet energy level of the auxiliary material, and the first excited singlet energy level of the auxiliary material is higher than the first excited singlet energy level of the guest material.

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;

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.

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;

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

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 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.

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 smaller than the peak wavelength of the emission peak of the guest material.

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 excited complex is greater than or equal to the peak wavelength of the emission peak of the guest material and the wavelength of the emission peak of the auxiliary material.

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 excited complex is less than or equal to 30 nanometers, and the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material are less than or equal to 10 nanometers.

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

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,

The guest material is an organic metal compound of osmium, and the auxiliary material is an organic metal compound of osmium.

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.

Preferably, at the first temperature, the peak wavelength of the light emitted by the light emitting element is between 500 nanometers and 700 nanometers.

Preferably, at the first temperature, the peak wavelength of the light emitted by the light emitting element is between 500 nanometers and 560 nanometers.

The present invention also provides a light-emitting element, comprising:

a pair of electrodes, including a first electrode and a second electrode;

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 first host material is a hole-transporting organic compound, and the second host material is an electron-transporting organic compound. The type of the first host material includes: aromatic amine compounds or carbazole compounds, and the type of the second host material includes: heteroaromatic compounds.

Preferably, the mobility of the first host material is 1.29*10^(-7)[m2/(V·s)] to 1.93*10^(-7)[m2/(V·s)], and the mobility of the second host material is 6.4*10^(-8)[m2/(V·s)] to 9.6*10^(-8)[m2/(V·s)].

Preferably, the mobility of the first host material is 1.61*10^(-7)[m2/(V·s)], and the mobility of the second host material is 8*10^(-8)[m2/(V·s)].

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

Preferably, the light emitting element further comprises:

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;

Wherein, the ratio of the mobility of the hole transport layer to the mobility of the electron transport layer is 5-200.

Preferably, the mobility of the hole transport layer is 1 to 10*10^(-4)[m2/(V·s)], and the mobility of the electron transport layer is 5*10^(-6) to 2*10^(-5)[m2/(V·s)].

Preferably, the ratio of the thickness of the hole transport layer to the thickness of the electron transport layer is 3.5:1 to 5.5:1.

Preferably, the light emitting element further comprises:

A first blocking layer 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 exciplex is less than 0.3 eV.

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 excited complex 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 blocking 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 blocking layer is greater than 0.05 eV.

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 0.3 eV, and the lowest unoccupied molecular orbital energy level of the electron transport layer is less than 0.3 eV. The difference between the energy level of the first barrier layer and the lowest unoccupied molecular orbital energy level is less than 0.3 eV.

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 excited complex 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 blocking layer is less than 0.3 eV.

The present invention further provides a display panel, comprising any of the above-mentioned light-emitting elements.

Beneficial Effects

The present invention increases the energy transfer path from the exciton complex to the guest material by adding auxiliary materials, and the first excited triplet energy level of the auxiliary materials is between the first excited triplet energy levels of the exciton complex and the guest material, thereby reducing the energy loss in the energy transfer process, ensuring the luminous efficiency of the light-emitting element and extending the service life of the light-emitting element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the light-emitting principle of an existing light-emitting element;

FIG2 is a schematic diagram of the light-emitting principle of a light-emitting element provided in an embodiment of the present invention;

FIG3 is a schematic diagram of a first structure of a light emitting element provided in an embodiment of the present invention;

FIG4 is a schematic diagram of a second structure of a light emitting element provided in an embodiment of the present invention;

FIG5 is a schematic diagram of a third structure of a light emitting element provided in an embodiment of the present invention;

FIG6 is a schematic diagram of a fourth structure of a light emitting element provided in an embodiment of the present invention;

7 is a schematic diagram of triplet energy levels of an exciplex, an auxiliary material, and a guest material of a light-emitting element provided in an embodiment of the present invention;

8 is a schematic diagram of the HOMO energy level, LUMO energy level and energy difference of each material of the light-emitting element provided in an embodiment of the present invention;

9 is a schematic diagram of absorption and emission spectra of an exciplex, an auxiliary material, and a guest material of a light-emitting element provided in an embodiment of the present invention;

FIG10 is a schematic diagram of an emission spectrum of a light-emitting element provided in an embodiment of the present invention;

FIG. 11 is a schematic diagram of the luminescence lifetime of a light-emitting element provided in an embodiment of the present invention.

Embodiments of the present invention

The present application provides a light-emitting layer, a light-emitting element and a display panel. To make the purpose, technical solution and effect of the present application clearer and more specific, the present application is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

The embodiments of the present application provide a light-emitting layer, a light-emitting element and a display panel. The following are detailed descriptions of each embodiment. It should be noted that the description order of the following embodiments is not intended to limit the preferred order of the embodiments.

The present invention provides a light-emitting layer, 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 excited complex; the first excited triplet energy level of the auxiliary material is lower than the first excited triplet energy level of the excited complex, 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 present invention increases the energy transfer path from the exciplex to the guest material by adding an 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 guest material, thereby reducing the energy loss in the energy transfer process, ensuring the luminous efficiency of the light-emitting layer and extending the service life of the light-emitting element.

In this embodiment, the first host material and the second host material are the two materials with the largest 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 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. The guest material and the auxiliary material are dispersed in the first host material and the second host material, which 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.

Please refer to Figure 1, the general light-emitting process of the light-emitting element is as follows:

(1) When the electrons and holes in the guest material molecules recombine and the guest material molecules are in an excited state: when the excited state of the guest material molecules is the first excited triplet state (T1), the guest material molecules emit phosphorescence; when the excited state of the guest material molecules is the first excited singlet state (S1), the guest material molecules in the first excited singlet state cross to the first excited triplet state through intersystem crossing, and then the guest material molecules emit phosphorescence.

(2) When the electrons and holes in the main material molecules recombine and the main material molecules are in an excited state: When the excited state of the host material molecule is the 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 molecule, 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 is a possibility that energy is transferred 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 major energy transfer pathway, so the description is omitted here. When the excited state of the host material molecule is the first excited singlet state, the first excited singlet state energy level of the host material is 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 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 through intersystem crossing to the first excited triplet state.

Please refer to FIG. 2 . In this embodiment, by adding the auxiliary material, a pathway for energy transfer from the main material to the guest material is increased, which is specifically 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, and there is a pathway for the excitation energy to be transferred 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 of the auxiliary material molecule The energy level of the hexagonal state and the first excited triplet state 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 is transferred from the exciplex to the guest material in the following ways: 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 there is intersystem crossing from the first excited singlet state to the first excited triplet state in the auxiliary material molecule. After receiving 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. This embodiment increases the exciplex by adding auxiliary materials. The energy transfer pathway between the excimer complex and the guest material is improved, and since the energy level gap in the energy transfer process is reduced, the energy loss of the energy transfer pathway through the auxiliary material is less than the direct energy transfer between the excimer complex and the guest material, thereby improving the energy transfer efficiency and thus extending the life of the light-emitting element.

The guest material may be a phosphorescent compound, and the guest material and the auxiliary material are selected from one of the organometallic compounds of platinum, iridium or osmium, respectively. By setting the guest material and the auxiliary material as organometallic compounds, the auxiliary material improves the π-π stacking between the guest material molecules, improves the dispersibility of the guest material in the light-emitting layer, reduces the probability of mutual collision between the guest materials in the first excited triplet state, reduces the damage to the guest material caused by the collision, and prolongs the life of the light-emitting element; at the same time, the guest material molecules in the first excited triplet state that release energy in the form of light increase, which also improves the luminous efficiency of the light-emitting element and prolongs the life of the light-emitting element.

Preferably, taking into account the difference in the first excited triplet energy level between metal organic compounds formed by different types 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; when the guest material is an organic metal compound of osmium, the auxiliary material is an organic metal compound of osmium.

Specifically, the guest material may be selected from any one or more combinations of the following compounds, and the auxiliary material may be selected from any one or more combinations of the following compounds:

At the first temperature, which may be room temperature, the first host material and the second host material are organic compounds, so the emission spectrum of the excited complex formed by the two at room temperature is generally the emission spectrum from the first excited singlet state; the guest material and the auxiliary material are The emission spectrum of the phosphorescent compound at room temperature is usually from the emission spectrum of the first excited triplet state; therefore, the exciplex, the auxiliary material and the guest material can reflect the relative sizes of the first excited singlet energy level of the exciplex, the first excited triplet energy level of the auxiliary material and the first excited triplet 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.

The first excited singlet energy level of the excited complex is higher than the first excited triplet energy level. To ensure that the first excited triplet energy level of the excited complex is sufficiently higher than the first excited triplet energy level of the auxiliary material so that energy can be transferred from the excited complex to the auxiliary 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 excited complex is greater than or equal to the peak wavelength of the emission peak of the guest material and the wavelength of the emission peak of the auxiliary material.

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. 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 regulating 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 regulated. 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. Orbital energy level. 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.

At the first temperature, the wavelength of the light emitted by the guest material is in the range of 500 nanometers to 700 nanometers; preferably, the guest material may be a green phosphorescent material, and at this time, the peak wavelength of the light emitted by the guest material is in the range of 500 nanometers to 560 nanometers.

Correspondingly, at the first temperature, the wavelength of the light emitted by the light-emitting element is in the range of 500 nanometers to 700 nanometers; preferably, the light-emitting element can be a green light-emitting element, at which time, the peak wavelength of the light emitted by the light-emitting element is in the range of 500 nanometers to 560 nanometers.

According to the different colors of the light emitted by the guest material, the light-emitting element used for the light-emitting layer can be a blue light-emitting element, a green light-emitting element, and a red light-emitting element. When the light-emitting layer is used for light-emitting elements of different colors, the thickness of the light-emitting layer will also be different. When the light-emitting layer is a red light-emitting layer, the thickness of the light-emitting layer is preferably 160 angstroms to 240 angstroms, more preferably 190 angstroms, 200 angstroms, 210 angstroms; when the light-emitting layer is a blue light-emitting layer, the thickness of the light-emitting layer is preferably 160 angstroms to 240 angstroms, more preferably 190 angstroms, 200 angstroms, 210 angstroms; when the light-emitting layer is a red light-emitting layer, the thickness of the light-emitting layer is preferably 320 angstroms to 480 angstroms, more preferably 390 angstroms, 400 angstroms, 410 angstroms.

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

(1) Forster energy transfer mechanism: Energy transfer occurs through the resonance phenomenon of dipole oscillations between the host molecule and the guest molecule. Through the resonance phenomenon of dipole oscillations, the host material molecule transfers energy to the guest material molecule, the host material molecule returns to the ground state, and the guest material molecule is in an excited state.

(2) Dexter energy transfer mechanism: When the host material molecule and the guest material molecule are close to the effective contact distance that produces orbital overlap, the electrons of the excited host material molecule and the ground state guest material molecule exchange electrons, thereby energy transfer occurs.

In the above two energy transfer mechanisms, the greater the overlap between the emission spectrum of the host material molecule (the fluorescence spectrum produced by the first excited singlet state returning to the singlet ground state, and the phosphorescence spectrum produced by the first excited triplet state returning to the singlet ground state) and the absorption spectrum of the guest material molecule, the more conducive it is to energy transfer.

In this embodiment, the first host material and the second host material first form an excited complex, and the excited complex is formed by the interaction between the excited state of the first host material molecules and the excited state of the second host material molecules. The first host material can be one of the hole-transporting organic compound and the electron-transporting compound, and the second host material can be the other of the hole-transporting organic compound and the electron-transporting compound. For example, the first host material is a hole-transporting organic compound, and the second host material is an electron-transporting compound.

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

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

Specifically, the first host material and the second host material can be selected from any one or more combinations of the following compounds:

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 greater 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 that is most conducive to luminescence in the absorption spectrum of the guest material (that is, the absorption wavelength of the guest material molecule directly transitioning from the singlet ground state to the first excited triplet state and the absorption near it) 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 conducive to improving the efficiency of energy transfer to the guest material molecule.

For organometallic compounds, the absorption wavelength of direct transition from the singlet ground state to the first excited triplet state and the absorption near it often appear in the range of 400 nanometers to 550 nanometers. In this wavelength range, due to the existence of ³ MLCT (charge transfer from metal to ligand) triplet transitions, as well as the possible existence of triplet π-π ^* transitions, singlet ¹ MLCT transitions, etc. Therefore, the absorption spectra of the guest material molecules and the auxiliary material molecules in the range of 400 nanometers to 550 nanometers show a wide absorption band. At the same time, in this embodiment, there is a path for the exciplex to transfer energy to the auxiliary material, and then to the guest material through the auxiliary material. Therefore, the overlap of the emission spectrum of the exciplex and the absorption spectrum of the auxiliary material and the absorption spectrum of the guest material in the range of 400 nanometers to 550 nanometers is conducive to improving the efficiency of energy transfer to the guest material and extending the life of the light-emitting element.

Preferably, the first absorption band of the auxiliary material in the range of 400 nanometers to 550 nanometers overlaps with the second absorption band of the guest material in the range of 400 nanometers to 550 nanometers, and the excited base complex has a first emission band in the range of 400 nanometers to 550 nanometers; 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.

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 may be less than 400 nm or greater than 550 nm, or the peak wavelength of the first emission peak may 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. The greater the overlap of the second absorption bands, the more efficient the energy transfer to the guest material. The first temperature may be room temperature.

Considering that the generation of the exciplex requires the driving of a driving voltage, the smaller the peak wavelength of the emission peak of the exciplex is, the greater the driving voltage required to excite the first host material and the second host material to form the exciplex is. Therefore, while energy transfer can occur, the larger the peak wavelength of the emission peak of the exciplex is, the more conducive 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 nanometers to 550 nanometers, the guest material has a second absorption peak in the range of 400 nanometers to 550 nanometers, and 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 overlap between the first emission band and 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 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.

Referring to FIG. 3 , the present invention provides a light emitting element, including:

a pair of electrodes, including a first electrode and a second electrode;

The light-emitting layer 105 as described above, wherein the light-emitting layer 105 is located between the pair of electrodes;

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

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.

The first electrode 101 is preferably at least one of a metal, an alloy, and a conductive compound. Specifically, it can be a metal oxide such as indium tin oxide, indium zinc oxide, indium zinc tungsten oxide, indium tin zinc, zinc oxide, or 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.

The second electrode 109 is preferably made of 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. The material of the second electrode 109 may include alkali metal elements, alkaline earth metal elements, rare earth metal elements, such as Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca, LiF/Al, Mo, Ti, Yb, W, or magnesium-silver alloy, aluminum-lithium alloy, etc.; or, the material of the second electrode 109 may also be selected from indium tin oxide, indium zinc oxide, zinc oxide, indium tin zinc oxide, etc., and a combination of the optional materials of the aforementioned second electrode 109. The thickness of the second electrode 109 is preferably 112 angstroms to 168 angstroms, more preferably 130 angstroms, 140 angstroms or 150 angstroms.

The recombination of the holes generated by the first host material and the electrons generated by the second host material is an important way to generate the excited complex. The mobility of the first host material and the mobility of the second host material are controlled within a certain range, which is beneficial to the unbalanced matching of the holes and electrons used to generate the excited complex, thereby avoiding a reduction in the luminous efficiency of the light-emitting element.

In some embodiments, the ratio of the mobility of the first host material to the mobility of the second host material is 1: 1 to 21: 1. The first host material is a material having hole transport properties, and its mobility is hole mobility, and the second host material is a material having electron transport properties, and its mobility is electron mobility.

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 mobility of the first host material is 1.29*10^(-7)[m ² /(V·s)] to 1.93*10^(-7)[m ² /(V·s)], and more preferably, the mobility of the first host material is 1.61*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)]. Preferably, the mobility of the second host material is 6.4*10^(-8)[m ² /(V·s)] to 9.6*10^(-8)[m ² /(V·s)]. More preferably, the mobility of the second host material is 8*10^(-8)[m ² /(V·s)].

When the mobility of the first host material is within the above range, especially 1.61*10^(-7)[m ² /(V·s)], and the mobility of the second host material is within the above range, especially 8*10^(-8)[m ² /(V·s)], the matching effect of holes and electrons for generating the excited complex in the light-emitting layer 105 is optimal, which is most conducive to improving the luminous efficiency of the light-emitting element.

The ratio of the first host material to the second host material affects the ratio of the number of holes and free electrons generated in the light-emitting layer 105. To achieve the matching of holes and electrons used to generate the exciplex, controlling the doping ratio of the first host material to the second host material is also beneficial. The matching of holes and electrons used to generate the exciplex is not unbalanced, thereby avoiding a reduction in the luminous efficiency of the light-emitting element.

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 occupied by the first host material in the light-emitting layer 105 to the volume occupied by the second host material in the light-emitting layer 105.

Please refer to FIG. 4 , the light emitting element further includes:

A hole transport layer 103 located between the first electrode 101 and the light-emitting layer 105;

An electron transport layer 107 located between the light emitting layer 105 and the second electrode 109;

The ratio of the mobility of the first hole transport layer 103 to the mobility of the electron transport layer 107 is 5-200.

The hole transport layer 103 includes a material having hole transport properties, such as 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 Aniline (2-TNATA), poly (3,4-ethylenedioxythiophene) / poly (4-styrene sulfonate) (PEDOT / PSS), polyaniline / dodecylbenzenesulfonic acid (PANI / DBSA), polyaniline / camphorsulfonic acid (PANI / CSA), polyaniline / poly (4-styrene sulfonate) (PANI / PSS), N, N-di (naphthalene-1-yl) -N, N-diphenylbenzidine (NPB), triphenylamine-containing polyether ketone (TPAPEK), 4-isopropyl-4'-methyldiphenyliodonium [tetrakis (pentafluorophenyl) borate], dipyridamole azine[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"-tri(N-carbazolyl)triphenylamine (TCTA), N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine (NPB), 4,4'-cyclohexylenebis[ N,N-bis(4-methylphenyl)aniline] (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-carbazole-9-yl)benzene (mDCP), etc.; combinations of the aforementioned compounds having hole transport properties. The hole transport layer The thickness of 103 is preferably 1040 angstroms to 1560 angstroms, more preferably 1200 angstroms, 1300 angstroms or 1400 angstroms.

The electron transport layer 107 includes a material having an electron transport property, such as tris(8-hydroxyquinoline)aluminum (Alq3), 1,3,5-tris[(3-pyridyl)-phenyl-3-yl]benzene, 2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine, 2-(4-(N-phenylbenzimidazol-1-yl)phenyl)-9,10-dinaphthothracene, 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(pyridin-3-yl)phenyl]benzene (BmPyPhB); metal halides such as LiF, NaCl, CsF, RbCl, RbI, CuI, KI, lanthanide metals such as Yb, and co-deposited materials of the above-mentioned metal halides and lanthanide metals; metal oxides, such as _Li2O , BaO; combinations of the above-mentioned materials with electron transport properties. Alternatively, the electron transport layer 107 may be formed of a mixture of an electron transport material and an insulating organic metal salt, wherein the organic metal salt may include, for example, metal acetate, metal benzoate, metal acetoacetate, metal acetylacetonate or metal stearate. The thickness of the electron transport layer 107 is preferably 240 angstroms to 420 angstroms, more preferably 300 angstroms or 350 angstroms.

During the light-emitting process of the light-emitting element, holes are transported from the hole transport layer 103 to the light-emitting layer 105, and free 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 beneficial to controlling the matching degree of holes and electrons used to generate the excited base complex, thereby avoiding reducing the light-emitting efficiency of the light-emitting element.

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

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. In order to achieve the matching of holes and electrons for generating the exciplex, the thickness ratio of the hole transport layer 103 and the electron transport layer 107 is controlled, which is also beneficial to the matching of holes and electrons for generating the exciplex without imbalance, thereby avoiding the reduction of The luminous efficiency of the light-emitting element.

In some embodiments, the ratio of the thickness of the hole transport layer 103 to 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, etc.; preferably, the ratio of the thickness of the hole transport layer 103 to the thickness of the electron transport layer 107 is 4:1.

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 the Mott-Gurney equation and the Frenkel effect: Taking the logarithm of both sides gives: It can be seen that there is a linear relationship between In(J/E2) and . The function graph of In(J/E2) is plotted as it changes, and the zero-field mobility of carriers in organic materials is calculated based on the intercept of the straight line. After substituting it into the Poole-Frenkel formula, the field-dependent mobility of carriers under a fixed electric field can be obtained.

Please refer to FIG5 , the light emitting element further includes:

A first blocking layer 104 located between the hole transport layer 103 and the light emitting layer 105;

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.

The first blocking layer 104 directly contacts the light-emitting layer 105 and the hole transport layer 103. The material of the first blocking 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 blocking layer 104 can be different from the material of the hole transport layer 103. Preferably, the material of the first blocking layer 104 includes an aromatic amine compound, such as a triarylamine compound. The thickness of light-emitting elements of different colors is different, so as to adjust the microcavity of light-emitting elements of different colors and effectively improve the luminous efficiency of the light-emitting element. Therefore, when the light-emitting element is a blue light-emitting element, the thickness of the first blocking layer 104 is preferably 40 angstroms to 60 angstroms, and 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 blocking layer 104 is preferably 320 angstroms to 480 angstroms, and 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 blocking layer 104 is preferably 720 angstroms to 1080 angstroms, and more preferably 850 angstroms, 900 angstroms or 950 angstroms.

The highest occupied molecular orbital energy level of the first barrier layer 104 is equal to the highest energy level of the exciplex The difference in energy levels of the occupied molecular orbitals is less than 0.3 eV, which is beneficial for holes to be transferred from the first blocking layer 104 to the light-emitting layer 105, thereby reducing the driving voltage of the light-emitting element.

In some embodiments, the difference between the lowest unoccupied molecular orbital energy level of the first blocking layer 104 and the lowest unoccupied molecular orbital energy level of the excited complex is greater than 0.05 eV, which is beneficial to the first blocking layer 104 blocking the electrons from the light-emitting layer 105 to the first blocking layer 104.

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 blocking layer 104 is less than 0.3 eV, which is beneficial for the transfer of holes from the hole transport layer 103 to the first blocking layer 104 and reduces the driving voltage of the light-emitting element.

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 blocking layer 104 is greater than 0.05 eV, which is beneficial to the hole transport layer 103 blocking the electrons from the first blocking layer 104 to the hole transport layer 103.

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 is beneficial for energy transfer from the first blocking layer 104 to the exciplex and reduces the driving voltage of the light-emitting element.

In some embodiments, the electron transport 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 transport layer 107 and the lowest unoccupied molecular orbital energy level of the excited complex is less than 0.3 eV, which is beneficial to the electron transport layer 107's blocking effect on holes from the light-emitting layer 105 to the electron transport layer 107.

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

In some embodiments, the light-emitting element further includes a second blocking layer 106 located between the light-emitting layer 105 and the electron transport layer 107. 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 is conducive to the transfer of electrons from the second blocking layer 106 to the light-emitting layer 105, thereby reducing 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 transport layer 107. The material selection range of the second blocking layer 106 is the same as the material selection range of the electron transport layer 107. In the same light-emitting element, the material of the second blocking layer 106 is different from that of the electron transport layer 107. Preferably, the material of the second blocking layer 106 can be a heteroaromatic compound, such as tris(III). Azinopyrimidine derivatives, etc. The thickness of the second barrier layer 106 is preferably 40 angstroms to 60 angstroms, more preferably 45 angstroms, 50 angstroms or 55 angstroms, which is beneficial to control the distance between the light-emitting layer 105 and the second electrode 109 .

Preferably, the difference between the lowest unoccupied molecular orbital energy level of the electron transport layer 107 and the lowest unoccupied molecular orbital energy level of the second blocking layer 106 is less than 0.3 eV, which is conducive to the transfer of electrons from the electron transport layer 107 to the second blocking layer 106, thereby reducing the driving voltage of the light-emitting element.

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

In some embodiments, the difference between the highest occupied molecular orbital energy level of the second blocking layer 106 and the highest occupied molecular orbital energy level of the excited complex is greater than 0.3 eV. Preferably, the difference between the highest occupied molecular orbital energy level of the second blocking layer 106 and the highest occupied molecular orbital energy level of the excited complex is greater than 0.4 eV. More preferably, the difference between the highest occupied molecular orbital energy level of the second blocking layer 106 and the highest occupied molecular orbital energy level of the excited complex is greater than 0.5 eV, which is beneficial to blocking holes moving from the light-emitting layer 105 to the second blocking layer, thereby improving the luminescence efficiency of the light-emitting element.

The above-mentioned light-emitting element may further include a hole injection layer 102 located between the first electrode 101 and the hole transport layer 103, wherein the hole injection layer 102 includes a material having a hole injection property, such as: metal oxides such as molybdenum oxide, titanium oxide, tungsten oxide, silver oxide, etc.; phthalocyanine compounds such as copper phthalocyanine, etc.; such as: 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"-tri(N-carbazolyl)triphenylamine (TCTA), N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine (NPB), 4,4'-cyclohexylenebis[N,N-bis(4-methylphenyl)-1,1-biphenyl]-4,4'-diamine (TPD), 4,4',4"-tri(N-carbazolyl)triphenylamine (TCTA), N,N'-di(naphthalene-1-yl)-N,N'-diphenylbenzidine (NPB), 4,4'-cyclohexylenebis[N,N-bis(4-methylphenyl)-1,1-biphenyl]-4,4'-diamine (TPD), 4,4'-di(1,1-biphenyl)- )aniline] (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-carbazole-9-yl)benzene (mDCP), etc. or a combination thereof. The material having hole injection properties in the hole injection layer 102 is doped in the hole injection layer 102, and the doping ratio is 1% to 3% (volume fraction). The thickness of the hole injection layer 102 is preferably 80 angstroms to 120 angstroms, and more preferably 90 angstroms, 100 angstroms or 110 angstroms.

The above-mentioned light-emitting element may further include a 109, the electron injection layer 108 includes a material with electron injection properties, such as alkali metal, alkaline earth metal, rare earth metal or alkali metal compound, alkaline earth metal compound, rare earth metal compound, etc., such as lithium, lithium fluoride, lithium oxide, calcium fluoride, ytterbium, Liq, KI, NaCl, CsF, Li2O, BaO, etc. 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 is conducive to injecting electrons into the electron transport layer 107.

The above-mentioned light-emitting element may further include a covering layer located on the second electrode 109, and the material of the covering layer may be an organic material or an inorganic material. When the material of the covering layer is an inorganic material, the inorganic material may include an alkali metal compound, such as LiF, or an alkaline earth metal compound, such as MgF ₂ , SiON, SiNx, SiOy, etc., or a combination thereof. When the material of the covering layer is an organic material, the organic material may include α-NPD, NPB, TPD, m-MTDATA, Alq3, CuPc, N4, N4, N4', N4'-tetrakis(biphenyl-4-yl)biphenyl-4,4'-diamine (TPD15), 4,4',4"-tris(carbazole-9-yl)triphenylamine (TCTA), etc., epoxy resin, or acrylate (such as methacrylate), or a combination thereof.

Please refer to FIG. 6 . The present invention further provides a light emitting element, which is the same or similar to the above light emitting element, except that:

A pair of electrodes, including a first electrode 101 and a second electrode 109;

The light-emitting layer 105 as described above, wherein the light-emitting layer 105 is located between the pair of electrodes, and the light-emitting layer 105 includes a first sub-light-emitting layer 113 and a second sub-light-emitting layer 120 located between the first sub-light-emitting layer 113 and the second electrode 109;

a first hole transport layer 111 located between the first electrode 101 and the first sub-light emitting layer 113;

A first sub-blocking layer 112 located between the first hole transport layer 111 and the first sub-light emitting layer 113;

a first electron transport layer 122 located between the second sub-light emitting layer 120 and the second electrode 109;

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

The third sub-blocking layer located on the side of the first sub-light emitting layer 113 close to the second sub-light emitting layer 120 Layer 114;

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

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

A second charge generation layer 117 located at a side of the first charge generation layer 116 close to the second sub-light emitting layer 120;

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

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

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

The electron injection layer 108 is located between the second electrode 109 and the first electron transport layer 122 .

Among them, along 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-light-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-light-emitting layer 120, the second sub-blocking layer 121, the first electron transport layer 122, and the electron injection layer 108 are stacked in sequence, and adjacent film layers are in contact with each other.

In this embodiment, the first hole transport layer 111 and the second hole transport layer 118 have the same or similar functions as the "hole transport layer" in the aforementioned light-emitting element, and therefore the materials having hole transport properties and the material selection range of the materials having hole transport properties are the same, and the range of the difference in the highest occupied molecular orbital energy level and the difference in the lowest unoccupied molecular orbital energy level between the first hole transport layer 111 and the first sub-blocking layer 112, and between the second hole transport layer 118 and the fourth sub-blocking layer 119 are the same as the range of the difference in the highest occupied molecular orbital energy level and the difference in the lowest unoccupied molecular orbital energy level between the "hole transport layer" and the "first blocking layer" in the aforementioned light-emitting element.

In this embodiment, the first electron transport layer 122 and the second electron transport layer 115 have the same or similar functions as the "electron transport layer" in the aforementioned light-emitting element, so the material having electron transport properties is The material selection range of the material with electron transport properties is the same, and the range of the difference in the highest occupied molecular orbital energy level and the difference in the lowest unoccupied molecular orbital energy level between the first electron transport layer 122 and the second sub-blocking layer 121, as well as the second electron transport layer 115 and the third sub-blocking layer 114 are the same as the range of the difference in the highest occupied molecular orbital energy level and the difference in the lowest unoccupied molecular orbital energy level between the "electron transport layer" and the "second blocking layer" in the aforementioned light-emitting element.

In this embodiment, the first sub-blocking layer 112 and the fourth sub-blocking layer 119 have the same or similar functions as the "first blocking layer" in the aforementioned light-emitting element, and therefore have the same range of material selection. The range of the difference in the highest occupied molecular orbital energy level, the difference in the lowest unoccupied molecular orbital energy level, and the difference in the first excited triplet energy level between the first sub-blocking layer 112 and the excited radical complex in the first sub-light-emitting layer 113, and the difference in the fourth sub-blocking layer 119 and the second sub-light-emitting layer 120 are the same as the range of the difference in the highest occupied molecular orbital energy level, the difference in the lowest unoccupied molecular orbital energy level, and the difference in the first excited triplet energy level between the "first blocking layer" and the "exciton complex" in the aforementioned light-emitting element.

In this embodiment, the second sub-blocking layer 121 and the third sub-blocking layer 114 have the same or similar functions as the "second blocking layer" in the aforementioned light-emitting element, and therefore have the same range of material selection. The range of the difference in the highest occupied molecular orbital energy level, the difference in the lowest unoccupied molecular orbital energy level, and the difference in the first excited triplet energy level between the second sub-blocking layer 121 and the excited radical complex in the second sub-light-emitting layer 120, and the range of the difference in the highest occupied molecular orbital energy level, the difference in the lowest unoccupied molecular orbital energy level, and the difference in the first excited triplet energy level between the "second sub-blocking layer" and the "exciton complex" in the aforementioned light-emitting element is the same.

In this embodiment, the thickness of the first charge generation layer 116 can be 80 angstroms to 120 angstroms, preferably 90 angstroms to 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 with electron transport properties of the "electron transport layer" in 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 with electron injection properties of the "charge injection layer" in 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, etc., preferably 95:5. Among them, 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.

In this embodiment, the thickness of the second charge generation layer 117 can be 80 angstroms to 120 angstroms, preferably 90 angstroms to 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 materials with hole transport properties in the "hole transport layer" in the aforementioned light-emitting element, and the selection range of the fourth charge-doped material is the same as the selection range of materials with hole injection properties in the "hole injection layer" in 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, etc., preferably 95:5. Among them, the doping ratio refers to the ratio of the volume occupied by the third charge-doped material in the second charge generation layer 117 to the volume occupied by the fourth charge-doped material.

Referring to FIG. 7 to FIG. 9 , a combination of the first host material, the second host material, the auxiliary material and the guest material of the light-emitting element provided in an embodiment of the present invention is described as follows:

The structural formulas of the first main material and the second main material are as follows:

First main material: Second main material:

The auxiliary material structural formula is as follows:

The structural formula of the guest material is as follows:

Please refer to FIG. 7 . In this embodiment, the first excited triplet energy levels of the exciplex formed by the first host material and the second host material, the auxiliary material and the guest material are respectively As shown in the figure, it is shown that 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 above results are obtained by converting the peak wavelength of the emission peak obtained in THF solution at 77K.

Please refer to Figure 8. In this embodiment, the HOMO, LUMO, and 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. The HOMO energy levels of the first host material, the second host material, the auxiliary material, and the guest material increase in sequence, and the LUMO energy levels of the first host material, the second host material, the auxiliary material, and the guest material decrease in sequence; the energy difference between HOMO and LUMO of the first host material and the second host material is greater than the energy difference between HOMO and LUMO of the auxiliary material, and the energy difference between HOMO and LUMO of the auxiliary material is greater than the energy difference between HOMO and LUMO of the guest material.

Please refer to Figure 9. In this embodiment, the excited complex (represented by "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.

The auxiliary material (indicated by "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.

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

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:

Specifically, the material of the hole transport layer of the light-emitting element is:

The material of the first barrier layer is:

The material of the second barrier layer is:

The material of the electron transport layer is:

Please refer to Figure 10, which shows the test results of the device luminescence spectrum after the first mixture (expressed as "Exciplex+GD") after the first host material, the second host material and the guest material are used as the light-emitting layer, the test results of the device luminescence spectrum after the second mixture (expressed as "Exciplex+AST") after the first host material, the second host material and the auxiliary material are used as the light-emitting layer, and the test results of the device luminescence spectrum after the third mixture (expressed as "Exciplex+GD+AST") after the first host material, the second host material, the auxiliary material and the guest material are used as the light-emitting layer. These three results show that the light-emitting element with the third mixture as the light-emitting layer mainly emits light from the guest material, which indirectly indicates the existence of an energy transfer path from the auxiliary material to the guest material. Among them, the volume ratio of the first main material: the second main material: the guest material in the first mixture is 47:47:6, the volume ratio of the first main material: the second main material: the auxiliary material in the second mixture is 47:47:6, and the volume ratio of the first main material: the second main material: the auxiliary material: the guest material in the third mixture is 44:44:6:6.

Please refer to FIG. 11. Further, the first main body material, the second main body material, the The luminescence lifetime of the light-emitting element combined as the light-emitting layer under different doping ratios of the auxiliary material and the guest material is shown in the figure. Among them, Ref (only GD) represents the first light-emitting layer without the addition of the 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 ratios of the first main material, the second main material, the auxiliary material, and the guest material are 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. It can be seen from the figure that with the addition of the auxiliary dopant, the luminescence lifetime of the light-emitting element increases significantly.

The embodiment of the present invention increases the energy transfer path from the excimer complex 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 levels of the excimer complex and the guest material, thereby reducing the energy loss in the energy transfer process, ensuring the luminous efficiency of the light-emitting element and extending the service life of the light-emitting element.

An embodiment of the present invention further discloses a display panel, which includes any of the above-mentioned light-emitting elements.

The display panel further includes an array substrate located at one side of the light emitting element, and a packaging layer located at a side of the light emitting element away from the array substrate and covering the light emitting element.

The display panel further comprises a polarizer layer located on a side of the encapsulation layer away from the light emitting element and a cover layer located on a side of the polarizer layer away from the light emitting element. The polarizer layer can be replaced by a color filter layer, and the color filter layer can include a plurality of color resists and a black matrix located on both sides of the color resists.

In some embodiments, the display panel includes 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 any of the light-emitting elements described above; preferably, the red light-emitting element, the green light-emitting element and the blue light-emitting element all adopt any of the light-emitting elements described above, which is beneficial to improving the overall luminous efficiency of the display panel while extending the service life of the display panel.

The display panel disclosed in the embodiment of the present invention increases the path of energy transfer from the exciplex to the guest material by adding auxiliary materials, and the first excited triplet energy level of the auxiliary materials is between the first excited triplet energy level of the exciplex and the guest material, thereby reducing the energy in the energy transfer process. Loss, ensuring the luminous efficiency of the light-emitting element while extending the service life of the light-emitting element.

The embodiment of the present invention discloses a light-emitting layer, a light-emitting element and a display panel, wherein the light-emitting layer includes: 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 present invention increases the path for 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 levels of the exciplex and the guest material, reduces the energy loss in the energy transfer process, ensures the luminous efficiency of the light-emitting element and prolongs the service life of the light-emitting element.

It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present application, and all these changes or substitutions should fall within the protection scope of the claims attached to the present application.

Claims

A light-emitting layer, characterized in that it comprises: 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 light-emitting layer according to claim 1 is characterized in that the highest occupied molecular orbital energy level of the auxiliary material is higher than the highest occupied molecular orbital energy level of the first main 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 main 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 light-emitting layer according to claim 2 is characterized in that the lowest unoccupied molecular orbital energy level of the auxiliary material is lower than the lowest unoccupied molecular orbital energy level of the first main 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 main 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.
The light-emitting layer according to claim 1 is characterized in that the first excited singlet energy level of the first main material is higher than the first excited singlet energy level of the auxiliary material, the first excited singlet energy level of the second main material is higher than the first excited singlet energy level of the auxiliary material, and the first excited singlet energy level of the auxiliary material is higher than the first excited singlet energy level of the guest material.
The light-emitting layer according to claim 1, characterized in that 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;

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.
The light-emitting layer according to claim 5, characterized in that the auxiliary material is at 400 nanometers. The guest material has a first absorption peak in the range of 400 nanometers to 550 nanometers, the guest material has a second absorption peak in the range of 400 nanometers to 550 nanometers, and the peak wavelength of the first absorption peak is smaller than the peak wavelength of the second absorption peak;

At a first temperature, the exciplex has a first emission peak, and a peak wavelength of the first emission peak is greater than or equal to a peak wavelength of the second absorption peak.
The light-emitting layer according to claim 6 is 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.
The light-emitting layer according to claim 1 is characterized in that, 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 excited complex, 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.
The light-emitting layer according to claim 8 is 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 excited complex is greater than or equal to the peak wavelength of the emission peak of the guest material and the wavelength of the emission peak of the auxiliary material.
The light-emitting layer according to claim 9 is 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 excited complex is less than or equal to 30 nanometers, and the peak wavelength of the emission peak of the guest material and the peak wavelength of the emission peak of the auxiliary material are less than or equal to 10 nanometers.
The light-emitting layer according to claim 1, characterized in that the auxiliary material and the guest material are respectively selected from one of the organic metal compounds of platinum, iridium or osmium.
The light-emitting layer according to claim 11, characterized in that the guest material is an organic metal compound of platinum or iridium, and the auxiliary material is an organic metal compound of platinum or iridium different from the guest material; or

The guest material is an organic metal compound of osmium, and the auxiliary material is an organic metal compound of osmium.
The light-emitting layer according to claim 1, characterized in that the first host material and the second host material account for 80% to 99.8% of the volume fraction of the light-emitting layer, and the guest material accounts for The volume fraction of the light-emitting layer is 0.1% to 10%, and the auxiliary material accounts for 0.1% to 10% of the volume fraction of the light-emitting layer.
The light-emitting layer according to claim 1 is characterized in that, at the first temperature, the peak wavelength of the light emitted by the light-emitting element is between 500 nanometers and 700 nanometers.
The light-emitting layer according to claim 14 is characterized in that, at the first temperature, the peak wavelength of the light emitted by the light-emitting element is between 500 nanometers and 560 nanometers.
A light emitting element, comprising:

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 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 first host material is a hole-transporting organic compound, the second host material is an electron-transporting compound, the first host material includes aromatic amine compounds or carbazole compounds, and the second host material includes heteroaromatic compounds.
The light-emitting element according to claim 16, 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)], and 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)].
The light-emitting element according to claim 17, characterized in that the doping ratio of the first host material to the second host material is 5:5 to 7:3.
The light-emitting element according to claim 16, characterized in that the light-emitting element further comprises:

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;

Wherein, the ratio of the mobility of the hole transport layer to the mobility of the electron transport layer is 5-200.
The light-emitting element according to claim 19, characterized in that the hole transport layer The mobility is 1*10^(-4) to 10*10^(-4) [m 2 /(V·s)], and the mobility of the electron transport layer is 5*10^(-6) to 2*10^(-5) [m 2 /(V·s)].
The light-emitting element according to claim 19, characterized in that the ratio of the thickness of the hole transport layer to the thickness of the electron transport layer is 3.5:1 to 5.5:1.
The light-emitting element according to claim 16, characterized in that the light-emitting element further comprises:

A first blocking layer 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 exciplex is less than 0.3 eV.
The light-emitting element according to claim 22 is characterized in that 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 excited complex 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 blocking 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 blocking layer is greater than 0.05 eV.
The light-emitting element according to claim 22 is 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 excited complex 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 first blocking layer is less than 0.3 eV.
The light-emitting element according to claim 22 is characterized in that the light-emitting element further comprises a second blocking layer located 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 excited complex 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 blocking layer is less than 0.3 eV.
A display panel, characterized in that the display panel comprises the light emitting element according to any one of claims 16 to 25.