CN113644212A - Light-emitting device, display panel and display device - Google Patents
Light-emitting device, display panel and display device Download PDFInfo
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- CN113644212A CN113644212A CN202110924524.XA CN202110924524A CN113644212A CN 113644212 A CN113644212 A CN 113644212A CN 202110924524 A CN202110924524 A CN 202110924524A CN 113644212 A CN113644212 A CN 113644212A
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/10—OLED displays
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- H—ELECTRICITY
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- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/649—Aromatic compounds comprising a hetero atom
- H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/649—Aromatic compounds comprising a hetero atom
- H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
- H10K85/6572—Polycyclic condensed heteroaromatic hydrocarbons comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
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Abstract
The invention provides a light-emitting device, a display panel and a display device, and relates to the technical field of display. The light-emitting device comprises a light-emitting layer positioned between an anode and a cathode, wherein the light-emitting layer comprises a thermal electron fluorescence compound, the relative molecular mass of the thermal electron fluorescence compound is larger than 700 and smaller than 1000, and the thermal electron fluorescence compound comprises a phenanthroimidazole derivative, an anthracene derivative and a high three-linear-state energy level molecule which are sequentially connected. The thermal electron fluorescent compound has good reverse system cross-over performance, reverse system cross-over occurs at a higher energy level, triplet state energy accumulation under high current density can be reduced, the efficiency roll-off of a light-emitting device is improved, and the service life of the light-emitting device is prolonged. In addition, the relative molecular mass of the thermal electron fluorescent compound is less than 1000, which is beneficial to evaporation. Therefore, the preparation difficulty, the efficiency roll-off and the improvement of the luminous life are considered.
Description
Technical Field
The present invention relates to the field of display technologies, and in particular, to a light emitting device, a display panel, and a display apparatus.
Background
Nowadays, the thermally activated delayed fluorescent material is widely used as a luminescent material in a luminescent device, and a unique energy level structure thereof opens a cross channel between opposite systems, so that the exciton utilization rate reaches a high level. In addition, the thermal activation delayed fluorescence material is completely composed of organic molecules, does not contain noble metal elements, and has lower cost, so the thermal activation delayed fluorescence material is very wide in application. However, the thermal activation delayed fluorescence material generally has the problems of severe efficiency roll-off and short luminescence life.
Some thermal exciton fluorescent materials are found to improve efficiency roll-off and luminescence lifetime to some extent, but in practical application, the thermal exciton fluorescent materials are not beneficial to evaporation, so that the thermal exciton fluorescent materials are difficult to prepare into a luminescent layer of a luminescent device. Thus, the efficiency roll-off and the improvement of the light-emitting life cannot be considered with the preparation difficulty.
Disclosure of Invention
The invention provides a light-emitting device, a display panel and a display device, and aims to solve the problem that the efficiency roll-off and the improvement of the light-emitting service life of the conventional light-emitting device cannot be considered at the same time with the preparation difficulty.
In order to solve the above problems, the present invention discloses a light emitting device, including an anode, a cathode, and a light emitting layer located between the anode and the cathode, where the light emitting layer includes a thermal electron fluorescent compound, the relative molecular mass of the thermal electron fluorescent compound is greater than 700 and less than 1000, and the thermal electron fluorescent compound includes a phenanthroimidazole derivative, an anthracene derivative, and a high triplet level molecule, which are connected in sequence.
Optionally, the heat-exciton fluorescent compound satisfies the following general formula:
wherein, X is the high triplet level molecule, L1 is the phenanthroimidazole derivative with first bridge between the anthracene derivative, L2 is the anthracene derivative with second bridge between the high triplet level molecule X, first bridge L1 with there is at least one second bridge L2, phenanthroimidazole derivative has first pendant group, the anthracene derivative has second pendant group and third pendant group, R1 is the first pendant group, R2 is the second pendant group, R3 is the third pendant group.
Optionally, the heat-exciton fluorescent compound satisfies the following energy level relationship:
Δ│S1-Tn│≤0.4eV；
wherein S1 is a singlet S1 energy level, Tn is a triplet Tn energy level, n is a positive integer, and n is more than 1 and less than 4.
Optionally, the front-line orbitals of the thermal electron fluorescent compound satisfy the following energy level relationship:
l HOMO1-LUMO 1-1.44 eV, or l HOMO2-LUMO 1-1.44 eV;
│HOMO1-HOMO2│＞0.3eV；
│LUMO1-LUMO2│＞0.2eV；
wherein the HOMO1 is a first highest occupied molecular orbital level, the HOMO2 is a second highest occupied molecular orbital level, and the HOMO1 is higher than the HOMO 2; the LUMO1 is a first lowest unoccupied molecular orbital level, the LUMO2 is a second lowest unoccupied molecular orbital level, and the LUMO1 is higher than the LUMO 2.
Optionally, the triplet state T1 energy level of the high triplet state level molecule is greater than 2.7 eV.
Optionally, the thermal exciton-fluorescent compound has a triplet T1 energy level of less than 2.0eV and the thermal exciton-fluorescent compound has a triplet T2 energy level of greater than 2.7 eV.
Optionally, the light emitting layer has a molecular orientation factor of greater than 66%.
Optionally, the high triplet energy level molecule comprises an aromatic compound containing heteroatoms including one or both of boron, nitrogen, oxygen, sulfur, phosphorus.
Optionally, the first, second, and third side groups are each independently selected from any one of a hydrogen atom, an alkyl group, a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, a mercapto group, a halogen atom, a phenyl group, a benzyl group, a phenethyl group, a diphenyl group, a naphthyl group, a furyl group, a thienyl group, a pyrrolyl group, a pyridyl group, a pyranyl group, a quinolyl group, an indolyl group, a carbazolyl group, an anilino group, an aromatic group, an aliphatic group, and a halogen-substituted boron atom.
Optionally, the first and second bridges are each independently selected from any one of a carbon atom, benzene, biphenyl, terphenyl, dibenzo, dibenzofuran, dibenzothiophene, silane, spirofluorene, diphenyl ether, and diphenyl sulfide.
Optionally, the light emitting device is a blue light emitting device.
Optionally, the light emitting device further comprises a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.
Optionally, the light emitting device further comprises at least one of an electron blocking layer and a hole blocking layer.
In order to solve the above problems, the present invention also discloses a display panel including the above light emitting device.
In order to solve the above problem, the present invention further discloses a display device including the above display panel.
Compared with the prior art, the invention has the following advantages:
in an embodiment of the present invention, a light emitting device includes an anode, a cathode, and a light emitting layer located between the anode and the cathode, where the light emitting layer includes a thermal electron fluorescent compound, a relative molecular mass of the thermal electron fluorescent compound is greater than 700 and less than 1000, and the thermal electron fluorescent compound includes a phenanthroimidazole derivative, an anthracene derivative, and a high triplet level molecule connected in this order. The thermal electron fluorescent compound has good reverse system cross-over performance, the reverse system cross-over occurs at a higher energy level, and triplet state energy accumulation under high current density can be reduced, so that the efficiency roll-off of a light-emitting device is improved, and the service life of the light-emitting device is prolonged. In addition, the relative molecular mass of the thermal electron fluorescent compound is within 1000, which is beneficial to the evaporation of the luminescent material. Therefore, the preparation difficulty, the efficiency roll-off and the improvement of the luminous life are considered.
Drawings
Fig. 1 is a cross-sectional view showing a light emitting device according to a first embodiment of the present invention;
fig. 2 is a cross-sectional view showing another light emitting device according to the first embodiment of the present invention;
fig. 3 is a cross-sectional view of another light-emitting device according to a first embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example one
Fig. 1 is a cross-sectional view showing a light emitting device according to a first embodiment of the present invention, and referring to fig. 1, the light emitting device includes an anode 10, a cathode 20, and a light emitting layer 30 between the anode 10 and the cathode 20, the light emitting layer 30 includes a thermal electron fluorescent compound, the relative molecular mass of the thermal electron fluorescent compound is greater than 700 and less than 1000, and the thermal electron fluorescent compound includes a phenanthroimidazole derivative, an anthracene derivative, and a high triplet level molecule connected in this order.
In the embodiment of the invention, the thermal electron fluorescent compound is of a D-A (donor-acceptor) structure, and can be used as a luminescent material in a luminescent device, the thermal electron fluorescent compound keeps the transition performance between opposite systems of the thermal activation delayed fluorescent material, the transition between the opposite systems is at a higher energy level, and the triplet state energy accumulation under high current density can be reduced, so that the efficiency roll-off of the luminescent device is improved, and the service life of the luminescent device is prolonged.
The inventor conducts fluorescence radiation test on the thermal exciton fluorescence compound and finds that the molecule of the thermal exciton fluorescence compound is 10 ℃ at the temperature of 80K-5M/L toluene solution without delay of fluorescence emission, refers to the excitation light cut-off after 10 u s after no fluorescence signal. The faster fluorescence emission of the thermal exciton fluorescent compound indicates that the exciton channel of the thermal exciton fluorescent compound has higher speed of transporting the exciton, so that the triplet state energy accumulation of the light-emitting layer under high current density can be reduced.
In addition, the light emitting layer is usually prepared by an evaporation process, and the currently mainstream evaporation process has high requirements on the glass transition temperature and the sublimation temperature of the material, wherein the relative molecular mass of the material is an important influence factor of the glass transition temperature and the sublimation temperature, so that the preparation of the light emitting layer by the evaporation process has certain requirements on the relative molecular mass of the light emitting material. In the embodiment of the invention, the relative molecular mass of the thermal electron fluorescent compound in the light-emitting layer 30 is more than 700 and less than 1000, the relative molecular mass is controlled within 1000, and the glass transition temperature and the evaporation temperature are more suitable, which is beneficial to the evaporation of the light-emitting material.
The inventor conducts thermogravimetric analysis on the thermal proton fluorescent compound, the thermal proton fluorescent compound shows more stable thermal decomposition performance, and the temperature corresponding to 95% of the weight under the thermogravimetric analysis is more than 400 ℃, which shows that the thermal proton fluorescent compound has high thermal decomposition temperature and is suitable for vapor deposition.
In summary, the efficiency roll-off and the improvement of the light-emitting life can be considered with the preparation difficulty.
Alternatively, the heat-exciton-fluorescing compound may satisfy the following general formula:
wherein, X is a high triplet level molecule, L1 is a first bond bridge between a phenanthroimidazole derivative and an anthracene derivative, L2 is a second bond bridge between the anthracene derivative and the high triplet level molecule X, at least one of the first bond bridge L1 and the second bond bridge L2 exists, the phenanthroimidazole derivative has a first side group, the anthracene derivative has a second side group and a third side group, R1 is the first side group, R2 is the second side group, and R3 is the third side group.
In the present embodiment, the phenanthroimidazole derivative (left part of L1) and the anthracene derivative (right part of L1) may be bridged by the first bond L1, and the anthracene derivative and the high triplet level molecule X may be bridged by the second bond L2. The thermal electron fluorescent compound meeting the general formula is used as a luminescent material, so that the luminescent device can be ensured to have high-efficiency thermal electron fluorescence emission, the high exciton utilization rate is ensured, meanwhile, lower efficiency roll-off can be obtained, and the problem of short service life of the device is solved.
Compared with a thermal activation delayed fluorescent material, the thermal electron fluorescent compound has the advantages that the molecular dihedral angle is increased, so that the thermal electron fluorescent compound is not easy to crystallize, has good film-forming property, is beneficial to vapor deposition film-forming and fully exerts the performance of a light-emitting device.
Alternatively, the heat-exciton-fluorescing compound satisfies the following energy level relationship:
Δ│S1-Tn│≤0.4eV；
wherein S1 is a singlet S1 energy level, Tn is a triplet Tn energy level, n is a positive integer, and n is more than 1 and less than 4.
In the embodiment of the present invention, the thermal exciton fluorescent compound having the difference between the singlet S1 energy level and the triplet Tn energy level of 0.4eV or less is used, so that the energy transfer rate of the light emitting layer 30 can be increased, and the triplet exciton utilization rate can be further increased.
Optionally, the front-line orbitals of the thermal electron fluorescent compounds satisfy the following energy level relationships:
l HOMO1-LUMO 1-1.44 eV, or l HOMO2-LUMO 1-1.44 eV;
│HOMO1-HOMO2│＞0.3eV；
│LUMO1-LUMO2│＞0.2eV；
wherein HOMO1 is the first highest occupied molecular orbital level, HOMO2 is the second highest occupied molecular orbital level, HOMO1 is higher than HOMO 2; LUMO1 is the first lowest unoccupied molecular orbital level, LUMO2 is the second lowest unoccupied molecular orbital level, and LUMO1 is higher than LUMO 2.
The front line orbitals of the heat-shock molecular fluorescent compounds are respectively sequenced according to the energy levels, the highest occupied molecular orbital is sequenced from high to low to be HOMO1 → HOMO, and the lowest unoccupied molecular orbital is sequenced from low to high to be LUMO1 → LUMOy, wherein x and y are positive integers. The singlet state energy level of the thermal electron fluorescent compound is sequentially ordered from low to high as S0 → Sp, and the triplet state energy level is sequentially ordered from low to high as T1 → Tq, wherein p and q are positive integers.
In the embodiment of the invention, the front-line orbit of the thermal-electron-excited fluorescent compound meets the energy level relation, and can meet the requirement of the carrier transport property required by the luminescent layer.
Alternatively, the triplet state T1 level of the high triplet state level molecule X is greater than 2.7 eV.
The triplet energy levels of the high three-triplet energy level molecule X are sequentially ordered from low to high, and the T1 energy level is the first triplet energy level, namely the triplet energy level with the lowest energy level.
Alternatively, the triplet T1 energy level of the heat-shock fluorescent compound is less than 2.0eV and the triplet T2 energy level of the heat-shock fluorescent compound is greater than 2.7 eV.
The triplet energy levels of the thermal electron fluorescent compounds are sequentially ordered from low to high, the T1 energy level is the first triplet energy level, namely the lowest triplet energy level, and the T2 energy level is the second triplet energy level, namely the second lowest triplet energy level.
Optionally, the molecular orientation factor of the light emitting layer 30 is greater than 66%.
For the thin film and the doped thin film prepared by the thermal electron fluorescent compound, the molecular orientation factor is more than 66% measured by an ellipsometer, and the linearly polarized light component perpendicular to the surface of the thin film is more than 33% measured by polarization analysis.
In the embodiment of the invention, the thermal-electron fluorescent compound is used as a luminescent material, so that the molecular length in the molecular axial direction can be prolonged, and the molecular orientation is improved, thereby enhancing the proportion of linearly polarized light vertical to a light-emitting plane and improving the light extraction efficiency.
Alternatively, the high triplet energy level molecule X comprises an aromatic compound containing heteroatoms including one or two of boron, nitrogen, oxygen, sulfur, phosphorus. The high triplet level molecule X may be an electron-rich structure or an electron-deficient structure, which is not specifically limited in this embodiment of the present invention.
Some alternative examples of high triplet energy level molecules X are provided below:
in the above examples, examples 1 to 23 are electron-deficient structures, and examples 24 to 34 are electron-rich structures.
Alternatively, the first, second and third side groups R1, R2, R3 are each independently selected from any one of a hydrogen atom, an alkyl group, a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, a mercapto group, a halogen atom, a phenyl group, a benzyl group, a phenethyl group, a diphenyl group, a naphthyl group, a furyl group, a thienyl group, a pyrrolyl group, a pyridyl group, a pyranyl group, a quinolyl group, an indolyl group, a carbazolyl group, an anilino group, an aromatic group, an aliphatic group and a halogen-substituted boron atom.
Alternatively, the first L1 and second L2 bridges are each independently selected from any one of a carbon atom, benzene, biphenyl, terphenyl, dibenzo, dibenzofuran, dibenzothiophene, silane, spirofluorene, diphenyl ether, and diphenyl sulfide.
Some alternative examples of thermal exciton fluorescent compounds are provided below:
the molecular torsion degree and the molecular structure of the thermal electron fluorescent compound can also increase the space distance between molecules, and tests show that the fluorescence emitted by the thermal electron fluorescent compound molecules in a 10-5M/L toluene solution is attenuated in a single exponential manner, so that the space distance between molecules is increased, the accumulation and interaction of triplet excitons can be further reduced, and the efficiency roll-off and the light-emitting life of a device are improved.
Optionally, the light emitting device is a blue light emitting device.
Fig. 2 shows a cross-sectional view of another light-emitting device according to the first embodiment of the present invention, and optionally, referring to fig. 2, the light-emitting device further includes a hole injection layer 40, a hole transport layer 50, an electron transport layer 60, and an electron injection layer 70.
Wherein the hole injection layer 40 is disposed on the anode 10, the hole transport layer 50 is disposed on the hole injection layer 40, the light emitting layer 30 is disposed on the hole transport layer 50, the electron transport layer 60 is disposed on the light emitting layer 30, the electron injection layer 70 is disposed on the electron transport layer 60, and the cathode 20 is disposed on the electron injection layer 70. In the top-emission light-emitting device, the cathode 20 may be made of a transparent material, and in the bottom-emission light-emitting device, the anode 10 may be made of a transparent material, which is not particularly limited in the embodiment of the present invention.
Fig. 3 shows a cross-sectional view of still another light-emitting device according to a first embodiment of the present invention, and optionally, referring to fig. 3, the light-emitting device further includes at least one of an electron blocking layer 80 and a hole blocking layer 90.
Among them, the electron blocking layer 80 may be disposed between the hole transport layer 50 and the light emitting layer 30, and the hole blocking layer 90 may be disposed between the light emitting layer 30 and the electron transport layer 60.
The inventors also performed a series of calculations and tests on light emitting devices (comparative examples) prepared using the thermally activated delayed fluorescence material, and light emitting devices (example 1, example 2, example 3) prepared using the thermally exciton-fluorescent compound provided in the examples of the present invention, and the results are shown in table 1 below.
TABLE 1
Wherein λ isPLFor photoluminescence spectra, PLQY for photoluminescence quantum yield, EQEmaxFor external quantum efficiency, Roll-Off for efficiency Roll-Off, CIE for chromaticity coordinates, λPLIs the wavelength of the emitted light.
Compared with the prior art, the embodiment of the invention selects the luminescent material with higher luminous efficiency, and improves the energy transfer rate of the luminescent material through the calibration of the triplet Tn energy level (1 < n < 4) and the singlet S1 energy level, thereby improving the triplet utilization rate and improving the light-emitting efficiency.
The thermal electron fluorescent compound can open a thermal electron transmission channel, reverse system crossing occurs at a higher energy level, and triplet state energy accumulation under high current density is reduced, so that the problems of efficiency roll-off and short luminescence service life of the thermal activation delayed fluorescent material are solved.
The thermal-exciton fluorescent compound provided by the embodiment of the invention does not need to have the thermal-exciton fluorescence characteristic of Hybrid local Charge-transferred state (Hybrid localized-excited and Charge-Transfer, HLCT), and correspondingly, the thermal-exciton channel is not limited in the thermal-exciton process of the Hybrid local Charge-transferred state, so that the optional types of the thermal-exciton fluorescent material are increased, more thermal-exciton fluorescent materials with relative molecular mass suitable for an evaporation process can be found, and the specific combination of a D-A structure is enriched to adapt to the polarity requirement of the material and the carrier transmission characteristic requirement.
According to the thermal-electron fluorescent compound provided by the embodiment of the invention, the molecular design further prolongs the molecular length of the molecular axis, the molecular orientation is improved, the linearly polarized light proportion vertical to the light-emitting plane is enhanced, and the light extraction efficiency is improved. The degree of molecular twist and molecular design also increase the spatial distance between molecules, further reducing the accumulation and interaction of triplet excitons.
According to the embodiment of the invention, the relative molecular mass of the thermal electron fluorescent compound is controlled within 1000, the substituent groups in the thermal electron fluorescent compound are screened and controlled, the dihedral angle of molecules is increased, and the evaporation coating of materials is facilitated and the performance of devices is fully exerted.
In an embodiment of the present invention, a light emitting device includes an anode, a cathode, and a light emitting layer located between the anode and the cathode, where the light emitting layer includes a thermal electron fluorescent compound, a relative molecular mass of the thermal electron fluorescent compound is greater than 700 and less than 1000, the thermal electron fluorescent compound includes a phenanthroimidazole derivative, an anthracene derivative, and a high triplet level molecule, which are connected in this order, the phenanthroimidazole derivative has a first side group, and the anthracene derivative has a second side group and a third side group. The thermal electron fluorescent compound has good reverse system cross-over performance, the reverse system cross-over occurs at a higher energy level, and triplet state energy accumulation under high current density can be reduced, so that the efficiency roll-off of a light-emitting device is improved, and the service life of the light-emitting device is prolonged. In addition, the relative molecular mass of the thermal electron fluorescent compound is within 1000, which is beneficial to the evaporation of the luminescent material. Therefore, the preparation difficulty, the efficiency roll-off and the improvement of the luminous life are considered.
Example two
The embodiment of the invention also discloses a display panel comprising the light-emitting device.
In an embodiment of the present invention, a light emitting device includes an anode, a cathode, and a light emitting layer located between the anode and the cathode, where the light emitting layer includes a thermal electron fluorescent compound, a relative molecular mass of the thermal electron fluorescent compound is greater than 700 and less than 1000, and the thermal electron fluorescent compound includes a phenanthroimidazole derivative, an anthracene derivative, and a high triplet level molecule connected in this order. The thermal electron fluorescent compound has good reverse system cross-over performance, the reverse system cross-over occurs at a higher energy level, and triplet state energy accumulation under high current density can be reduced, so that the efficiency roll-off of a light-emitting device is improved, and the service life of the light-emitting device is prolonged. In addition, the relative molecular mass of the thermal electron fluorescent compound is within 1000, which is beneficial to the evaporation of the luminescent material. Therefore, the preparation difficulty, the efficiency roll-off and the improvement of the luminous life are considered.
EXAMPLE III
The embodiment of the invention also discloses a display device which comprises the display panel.
In an embodiment of the present invention, a light emitting device in a display panel includes an anode, a cathode, and a light emitting layer located between the anode and the cathode, where the light emitting layer includes a thermal electron fluorescent compound, a relative molecular mass of the thermal electron fluorescent compound is greater than 700 and less than 1000, and the thermal electron fluorescent compound includes a phenanthroimidazole derivative, an anthracene derivative, and a high triplet level molecule connected in sequence. The thermal electron fluorescent compound has good reverse system cross-over performance, the reverse system cross-over occurs at a higher energy level, and triplet state energy accumulation under high current density can be reduced, so that the efficiency roll-off of a light-emitting device is improved, and the service life of the light-emitting device is prolonged. In addition, the relative molecular mass of the thermal electron fluorescent compound is within 1000, which is beneficial to the evaporation of the luminescent material. Therefore, the preparation difficulty, the efficiency roll-off and the improvement of the luminous life are considered.
While, for purposes of simplicity of explanation, the foregoing method embodiments have been described as a series of acts or combination of acts, it will be appreciated by those skilled in the art that the present invention is not limited by the illustrated ordering of acts, as some steps may occur in other orders or concurrently with other steps in accordance with the invention. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required by the invention.
The embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The light emitting device, the display panel and the display device provided by the present invention are described in detail above, and the principle and the embodiment of the present invention are explained in detail herein by applying specific examples, and the description of the above examples is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (15)
1. A light-emitting device is characterized by comprising an anode, a cathode and a light-emitting layer between the anode and the cathode, wherein the light-emitting layer comprises a thermal electron fluorescent compound, the relative molecular mass of the thermal electron fluorescent compound is larger than 700 and smaller than 1000, and the thermal electron fluorescent compound comprises a phenanthroimidazole derivative, an anthracene derivative and three high-linear-state energy level molecules which are sequentially connected.
2. A light emitting device as claimed in claim 1, wherein the thermal exciton fluorescent compound satisfies the following general formula:
wherein, X is the high triplet level molecule, L1 is the phenanthroimidazole derivative with first bridge between the anthracene derivative, L2 is the anthracene derivative with second bridge between the high triplet level molecule X, first bridge L1 with there is at least one second bridge L2, phenanthroimidazole derivative has first pendant group, the anthracene derivative has second pendant group and third pendant group, R1 is the first pendant group, R2 is the second pendant group, R3 is the third pendant group.
3. The light-emitting device according to claim 1, wherein the thermal exciton fluorescent compound satisfies the following energy level relationship:
Δ│S1-Tn│≤0.4eV；
wherein S1 is a singlet S1 energy level, Tn is a triplet Tn energy level, n is a positive integer, and n is more than 1 and less than 4.
4. The light-emitting device of claim 1, wherein the front-line trajectory of the thermal exciton fluorescent compound satisfies the following energy level relationship:
l HOMO1-LUMO 1-1.44 eV, or l HOMO2-LUMO 1-1.44 eV;
│HOMO1-HOMO2│＞0.3eV；
│LUMO1-LUMO2│＞0.2eV；
wherein the HOMO1 is a first highest occupied molecular orbital level, the HOMO2 is a second highest occupied molecular orbital level, and the HOMO1 is higher than the HOMO 2; the LUMO1 is a first lowest unoccupied molecular orbital level, the LUMO2 is a second lowest unoccupied molecular orbital level, and the LUMO1 is higher than the LUMO 2.
5. A light emitting device according to claim 1 wherein the triplet level T1 level of the high triplet level molecule is greater than 2.7 eV.
6. The light-emitting device according to claim 1, wherein the thermal exciton fluorescent compound has a triplet T1 energy level of less than 2.0eV and the thermal exciton fluorescent compound has a triplet T2 energy level of greater than 2.7 eV.
7. The light-emitting device according to claim 1, wherein the light-emitting layer has a molecular orientation factor of greater than 66%.
8. The light-emitting device of claim 1, wherein the high triplet level molecules comprise aromatic compounds containing heteroatoms including one or both of boron, nitrogen, oxygen, sulfur, and phosphorus.
9. The light-emitting device according to claim 2, wherein the first side group, the second side group, and the third side group are each independently selected from any one of a hydrogen atom, an alkyl group, a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, a mercapto group, a halogen atom, a phenyl group, a benzyl group, a phenethyl group, a diphenyl group, a naphthyl group, a furyl group, a thienyl group, a pyrrolyl group, a pyridyl group, a pyranyl group, a quinolyl group, an indolyl group, a carbazolyl group, an anilino group, an aromatic group, an aliphatic group, and a halogen-substituted boron atom.
10. A light-emitting device according to claim 2, wherein the first bond bridge and the second bond bridge are each independently selected from any one of a carbon atom, benzene, biphenyl, terphenyl, dibenzo, dibenzofuran, dibenzothiophene, silane, spirofluorene, diphenyl ether, and diphenyl sulfide.
11. The light-emitting device according to claim 1, wherein the light-emitting device is a blue light-emitting device.
12. The light-emitting device according to any one of claims 1 to 11, further comprising a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.
13. The light-emitting device according to claim 12, further comprising at least one of an electron blocking layer and a hole blocking layer.
14. A display panel comprising the light-emitting device according to any one of claims 1 to 13.
15. A display device characterized by comprising the display panel according to claim 14.
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