CN113644212B - Light emitting device, display panel and display device - Google Patents
Light emitting device, display panel and display device Download PDFInfo
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- CN113644212B CN113644212B CN202110924524.XA CN202110924524A CN113644212B CN 113644212 B CN113644212 B CN 113644212B CN 202110924524 A CN202110924524 A CN 202110924524A CN 113644212 B CN113644212 B CN 113644212B
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- 239000007850 fluorescent dye Substances 0.000 claims abstract description 70
- 150000001454 anthracenes Chemical class 0.000 claims abstract description 20
- GZPPANJXLZUWHT-UHFFFAOYSA-N 1h-naphtho[2,1-e]benzimidazole Chemical class C1=CC2=CC=CC=C2C2=C1C(N=CN1)=C1C=C2 GZPPANJXLZUWHT-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000004770 highest occupied molecular orbital Methods 0.000 claims description 14
- 238000004768 lowest unoccupied molecular orbital Methods 0.000 claims description 14
- 238000002347 injection Methods 0.000 claims description 10
- 239000007924 injection Substances 0.000 claims description 10
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 9
- 230000000903 blocking effect Effects 0.000 claims description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 6
- 229910052796 boron Inorganic materials 0.000 claims description 6
- TXCDCPKCNAJMEE-UHFFFAOYSA-N dibenzofuran Chemical compound C1=CC=C2C3=CC=CC=C3OC2=C1 TXCDCPKCNAJMEE-UHFFFAOYSA-N 0.000 claims description 6
- IYYZUPMFVPLQIF-UHFFFAOYSA-N dibenzothiophene Chemical compound C1=CC=C2C3=CC=CC=C3SC2=C1 IYYZUPMFVPLQIF-UHFFFAOYSA-N 0.000 claims description 6
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 claims description 6
- USIUVYZYUHIAEV-UHFFFAOYSA-N diphenyl ether Chemical compound C=1C=CC=CC=1OC1=CC=CC=C1 USIUVYZYUHIAEV-UHFFFAOYSA-N 0.000 claims description 6
- 230000005525 hole transport Effects 0.000 claims description 6
- YJTKZCDBKVTVBY-UHFFFAOYSA-N 1,3-Diphenylbenzene Chemical group C1=CC=CC=C1C1=CC=CC(C=2C=CC=CC=2)=C1 YJTKZCDBKVTVBY-UHFFFAOYSA-N 0.000 claims description 3
- 125000000094 2-phenylethyl group Chemical group [H]C1=C([H])C([H])=C(C([H])=C1[H])C([H])([H])C([H])([H])* 0.000 claims description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 3
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 3
- 125000001931 aliphatic group Chemical group 0.000 claims description 3
- 125000003545 alkoxy group Chemical group 0.000 claims description 3
- 125000000217 alkyl group Chemical group 0.000 claims description 3
- 125000003277 amino group Chemical group 0.000 claims description 3
- 125000002490 anilino group Chemical group [H]N(*)C1=C([H])C([H])=C([H])C([H])=C1[H] 0.000 claims description 3
- 150000001491 aromatic compounds Chemical class 0.000 claims description 3
- 125000003118 aryl group Chemical group 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 125000001797 benzyl group Chemical group [H]C1=C([H])C([H])=C(C([H])=C1[H])C([H])([H])* 0.000 claims description 3
- 235000010290 biphenyl Nutrition 0.000 claims description 3
- 239000004305 biphenyl Substances 0.000 claims description 3
- 125000006267 biphenyl group Chemical group 0.000 claims description 3
- 125000000609 carbazolyl group Chemical group C1(=CC=CC=2C3=CC=CC=C3NC12)* 0.000 claims description 3
- 125000004432 carbon atom Chemical group C* 0.000 claims description 3
- 125000004093 cyano group Chemical group *C#N 0.000 claims description 3
- LTYMSROWYAPPGB-UHFFFAOYSA-N diphenyl sulfide Chemical compound C=1C=CC=CC=1SC1=CC=CC=C1 LTYMSROWYAPPGB-UHFFFAOYSA-N 0.000 claims description 3
- 125000002541 furyl group Chemical group 0.000 claims description 3
- 125000005843 halogen group Chemical group 0.000 claims description 3
- 125000005842 heteroatom Chemical group 0.000 claims description 3
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 3
- 125000001041 indolyl group Chemical group 0.000 claims description 3
- 125000001624 naphthyl group Chemical group 0.000 claims description 3
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 239000011574 phosphorus Substances 0.000 claims description 3
- 125000004309 pyranyl group Chemical group O1C(C=CC=C1)* 0.000 claims description 3
- 125000004076 pyridyl group Chemical group 0.000 claims description 3
- 125000000168 pyrrolyl group Chemical group 0.000 claims description 3
- 125000005493 quinolyl group Chemical group 0.000 claims description 3
- 229910000077 silane Inorganic materials 0.000 claims description 3
- -1 spirofluorene Chemical compound 0.000 claims description 3
- 239000011593 sulfur Substances 0.000 claims description 3
- 229910052717 sulfur Inorganic materials 0.000 claims description 3
- 125000001544 thienyl group Chemical group 0.000 claims description 3
- 125000003396 thiol group Chemical group [H]S* 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 230000005465 channeling Effects 0.000 abstract description 12
- 238000009825 accumulation Methods 0.000 abstract description 10
- 238000002360 preparation method Methods 0.000 abstract description 9
- 238000007740 vapor deposition Methods 0.000 abstract description 9
- 230000006872 improvement Effects 0.000 abstract description 7
- 230000002349 favourable effect Effects 0.000 abstract description 6
- 230000002035 prolonged effect Effects 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 29
- 238000000034 method Methods 0.000 description 14
- 230000008569 process Effects 0.000 description 8
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 230000003111 delayed effect Effects 0.000 description 6
- 230000008020 evaporation Effects 0.000 description 6
- 238000001704 evaporation Methods 0.000 description 6
- 230000009471 action Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000009477 glass transition Effects 0.000 description 3
- 238000007725 thermal activation Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000002950 deficient Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 238000004020 luminiscence type Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000000859 sublimation Methods 0.000 description 2
- 230000008022 sublimation Effects 0.000 description 2
- 238000005979 thermal decomposition reaction Methods 0.000 description 2
- 239000012780 transparent material Substances 0.000 description 2
- 238000001994 activation Methods 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000000572 ellipsometry Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 239000009289 huang-lien-chieh-tu-tang Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000005424 photoluminescence Methods 0.000 description 1
- 238000000103 photoluminescence spectrum Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
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- 238000006862 quantum yield reaction Methods 0.000 description 1
- 125000001424 substituent group Chemical group 0.000 description 1
Classifications
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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
-
- 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
-
- 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
- H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
-
- 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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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Optics & Photonics (AREA)
- Electroluminescent Light Sources (AREA)
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 thermoexciton fluorescent compound, the relative molecular mass of the thermoexciton fluorescent compound is more than 700 and less than 1000, and the thermoexciton fluorescent compound comprises a phenanthroimidazole derivative, an anthracene derivative and a high triplet energy level molecule which are connected in sequence. The thermoexciton fluorescent compound has better intersystem channeling performance, and intersystem channeling occurs at a higher energy level, so that triplet energy accumulation under high current density can be reduced, the efficiency roll-off of the light-emitting device is improved, and the service life of the light-emitting device is prolonged. In addition, the relative molecular mass of the thermoexciton fluorescent compound is less than 1000, which is favorable for vapor deposition. Thus, the preparation difficulty and the improvement of the efficiency roll-off and 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, thermally activated delayed fluorescent materials are widely used as light emitting materials in light emitting devices, and their unique energy level structure opens up the intersystem crossing channel, so that exciton utilization reaches a very high level. In addition, the thermal activation delay fluorescent material is completely composed of organic molecules, does not contain noble metal elements, and has lower cost, so that the thermal activation delay fluorescent material has wide application. However, the thermal activation delay fluorescent material generally has the problems of severe efficiency roll-off and shorter luminescence life.
Some thermoexciton fluorescent materials are found to improve the efficiency roll-off and the light-emitting life to some extent, but in practical application, the thermoexciton fluorescent materials are unfavorable for vapor deposition, so that the thermoexciton fluorescent materials are difficult to prepare into a light-emitting layer of a light-emitting device. Thus, improvement of efficiency roll-off and light emitting life cannot be achieved at the same time as the difficulty in preparation.
Disclosure of Invention
The invention provides a light-emitting device, a display panel and a display device, which are used for solving the problems that the efficiency roll-off and the light-emitting life of the existing light-emitting device are improved and the preparation difficulty is not compatible.
In order to solve the above problems, the present invention discloses a light emitting device comprising an anode, a cathode, and a light emitting layer between the anode and the cathode, the light emitting layer comprising a thermo-exciton fluorescent compound having a relative molecular mass of more than 700 and less than 1000, the thermo-exciton fluorescent compound comprising a phenanthroimidazole derivative, an anthracene derivative, and a high triplet energy level molecule connected in this order.
Optionally, the thermoexciton fluorescent compound satisfies the following general formula:
Wherein X is the high triplet energy level molecule, L1 is a first bond bridge between the phenanthroimidazole derivative and the anthracene derivative, L2 is a second bond bridge between the anthracene derivative and the high triplet energy 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.
Optionally, the thermo-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 1 < n < 4.
Optionally, the front-line orbitals of the thermo-exciton fluorescent compound satisfy the following energy level relationship:
-HOMO 1-LUMO 1-1.44 eV, or-HOMO 2-LUMO 1-1.44 eV;
│HOMO1-HOMO2│＞0.3eV；
│LUMO1-LUMO2│＞0.2eV；
Wherein, the HOMO1 is a first highest occupied molecular orbital energy level, the HOMO2 is a second highest occupied molecular orbital energy level, and the HOMO1 is higher than the HOMO2; the LUMO1 is the first lowest unoccupied molecular orbital energy level, the LUMO2 is the second lowest unoccupied molecular orbital energy level, and the LUMO1 is higher than the LUMO2.
Optionally, the triplet T1 level of the high triplet level molecule is greater than 2.7eV.
Alternatively, the triplet T1 level of the thermo-exciton fluorescent compound is less than 2.0eV and the triplet T2 level of the thermo-exciton fluorescent compound is greater than 2.7eV.
Optionally, the molecular orientation factor of the light emitting layer is greater than 66%.
Optionally, the high triplet energy level molecule comprises an aromatic compound comprising a heteroatom comprising one or both of boron, nitrogen, oxygen, sulfur, phosphorus.
Alternatively, each of the first, second, and third side groups is 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 and second bridges are each independently selected from any one of carbon atoms, 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 includes 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 problems, the invention also discloses a display panel which comprises the light-emitting device.
In order to solve the problems, the invention also discloses a display device which comprises the display panel.
Compared with the prior art, the invention has the following advantages:
In an embodiment of the invention, a light emitting device comprises an anode, a cathode, and a light emitting layer between the anode and the cathode, the light emitting layer comprising a thermo-exciton fluorescent compound having a relative molecular mass greater than 700 and less than 1000, the thermo-exciton fluorescent compound comprising a phenanthroimidazole derivative, an anthracene derivative, and a high triplet energy level molecule connected in sequence. The thermoexciton fluorescent compound has better intersystem channeling performance, and intersystem channeling occurs at a higher energy level, so that triplet energy accumulation under high current density can be reduced, thereby improving the efficiency roll-off of the light emitting device and prolonging the service life of the light emitting device. In addition, the relative molecular mass of the thermoexciton fluorescent compound is within 1000, which is favorable for the vapor deposition of luminescent materials. Thus, the preparation difficulty and the improvement of the efficiency roll-off and the luminous life are considered.
Drawings
Fig. 1 shows a cross-sectional view of a light emitting device according to a first embodiment of the present invention;
fig. 2 shows a cross-sectional view of another light emitting device of the first embodiment of the present invention;
Fig. 3 shows a cross-sectional view of yet another light emitting device of the first embodiment of the present invention.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
Fig. 1 shows a cross-sectional view of a light emitting device according to a first embodiment of the present invention, 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 thermo-exciton fluorescent compound having a relative molecular mass of more than 700 and less than 1000, the thermo-exciton fluorescent compound including a phenanthroimidazole derivative, an anthracene derivative, and a high triplet energy level molecule connected in this order.
In the embodiment of the invention, the thermo-exciton fluorescent compound is in a D-A (donor-acceptor) structure, and can be used as a luminescent material in a luminescent device, so that the thermo-exciton fluorescent compound keeps the intersystem channeling performance of the thermo-activation delayed fluorescent material, the intersystem channeling occurs at a higher energy level, and the accumulation of triplet energy under high current density can be reduced, thereby improving the efficiency roll-off of the luminescent device and prolonging the service life of the luminescent device.
The inventors carried out a fluorescence emission test on the thermoexciton fluorescent compound, and found that the thermoexciton fluorescent compound molecule has no delayed fluorescence emission in 10 -5 M/L toluene solution at 80K, which means no fluorescence signal after 10 mu s of excitation light is cut off. The fluorescent emission of the thermoexciton fluorescent compound is faster, which means that the exciton channel of the thermoexciton fluorescent compound transfers carrier excitons faster, thus the triplet energy accumulation of the light emitting layer under high current density can be reduced.
In addition, the light-emitting layer is usually prepared through an evaporation process, and the currently mainstream evaporation process has higher requirements on the glass transition temperature and the sublimation temperature of the material, wherein the relative molecular mass of the material is an important influencing factor of the glass transition temperature and the sublimation temperature, so that the preparation of the light-emitting layer through 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 thermoexciton fluorescent compound in the luminescent layer 30 is 700 < M < 1000, and the relative molecular mass is controlled within 1000, so that the thermoexciton fluorescent compound has more suitable glass transition temperature and evaporation temperature, and is beneficial to the evaporation of luminescent materials.
The inventors carried out thermal weightlessness analysis on the thermoexciton fluorescent compound, the thermoexciton fluorescent compound shows more stable thermal decomposition performance, and the corresponding temperature is higher than 400 ℃ when the weight is 95% under the thermal weightlessness analysis, which indicates that the thermoexciton fluorescent compound has high thermal decomposition temperature and is suitable for vapor deposition.
In conclusion, the efficiency roll-off and the improvement of the luminous life can be achieved at the same time as the preparation difficulty.
Alternatively, the thermoexciton fluorescent compound may satisfy the following general formula:
Wherein X is a high triplet energy 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 energy 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 embodiment of the invention, the phenanthroimidazole derivative (left part of L1) and the anthracene derivative (right part of L1) can be bridged by a first bond bridge L1, and the anthracene derivative and the high triplet energy level molecule X can be bridged by a second bond bridge L2. The thermoexciton fluorescent compound meeting the general formula is used as a luminescent material, so that the luminescent device can be ensured to have high-efficiency thermoexciton fluorescent emission, and the problem that the device life is shorter can be solved while the utilization rate of the thermoexciton is ensured to be high.
Compared with a thermally activated delayed fluorescent material, the molecule dihedral angle of the thermal exciton fluorescent compound is increased, so that the thermal exciton fluorescent compound is not easy to crystallize, has good film forming property, is favorable for vapor deposition film forming and fully plays the property of a light-emitting device.
Alternatively, the thermoexciton 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 1 < n < 4.
In the embodiment of the invention, the energy transfer rate of the luminescent layer 30 can be improved by adopting the thermoexciton fluorescent compound with the difference between the singlet S1 energy level and the triplet Tn energy level within 0.4eV, so that the utilization rate of triplet excitons is improved.
Alternatively, the front-line orbitals of the thermoexciton fluorescent compounds satisfy the following energy level relationship:
-HOMO 1-LUMO 1-1.44 eV, or-HOMO 2-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 HOMO2; LUMO1 is the first lowest unoccupied molecular orbital level, LUMO2 is the second lowest unoccupied molecular orbital level, and LUMO1 is higher than LUMO2.
The front orbitals of the thermoexciton fluorescent compound are respectively ordered according to the energy levels, the highest occupied molecular orbitals are ordered into HOMO 1-HOMOx from top to bottom, and the lowest unoccupied molecular orbitals are ordered into LUMO 1-LUMOy from bottom to top, wherein x and y are positive integers. The singlet energy level of the thermoexciton fluorescent compound is sequentially ordered from low to high as S0 to Sp, and the triplet energy level is sequentially ordered from low to high as T1 to Tq, wherein p and q are both positive integers.
In the embodiment of the invention, the front-line orbit of the thermoexciton fluorescent compound meets the energy level relation and can meet the carrier transmission characteristic requirement required by the light-emitting layer.
Alternatively, the triplet T1 level of the high triplet energy level molecule X is greater than 2.7eV.
The triplet energy levels of the high triplet energy level molecules X are sequentially ordered from low to high, and the T1 energy level is the triplet energy level of the first bit, i.e. the triplet energy level with the lowest level.
Alternatively, the triplet T1 level of the thermo-exciton fluorescent compound is less than 2.0eV and the triplet T2 level of the thermo-exciton fluorescent compound is greater than 2.7eV.
The triplet state energy levels of the thermoexciton fluorescent compound are sequentially ordered from low to high, the T1 energy level is the triplet state energy level of the first position, namely the lowest triplet state energy level, and the T2 energy level is the triplet state energy level of the second position, namely the triplet state energy level with the lowest last level.
Alternatively, the molecular orientation factor of the light emitting layer 30 is greater than 66%.
For the films and doped films prepared by using the thermoexcitonic fluorescent compound, the inventors measured that the molecular orientation factor was > 66% by ellipsometry and that the linearly polarized light component perpendicular to the film surface was > 33% by polarization analysis.
In the embodiment of the invention, the thermoexciton fluorescent compound is used as a luminescent material, so that the molecular length in the axial direction of molecules can be prolonged, and the molecular orientation can be improved, thereby enhancing the linear polarized light proportion perpendicular to the light emitting plane and improving the light extraction efficiency.
Optionally, the high triplet energy level molecule X comprises an aromatic compound comprising heteroatoms comprising one or two of boron, nitrogen, oxygen, sulfur, phosphorus. The high triplet energy level molecule X may be either an electron rich structure or an electron deficient structure, which is not particularly limited in the embodiment of the present invention.
Some alternative examples of high triplet energy level molecules X are provided below:
in the above examples, examples 1-23 are electron deficient structures and examples 24-34 are electron rich structures.
Alternatively, the first, second and third side groups R1, R2 and 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 and second bridges L1 and L2 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 thermoexciton fluorescent compounds are provided below:
the molecular torsion degree and the molecular structure of the thermoexciton fluorescent compound can also increase the space distance between molecules, and the test proves that the fluorescence emitted by the thermoexciton fluorescent compound molecule in 10 < -5 > M/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 state excitons can be further reduced, and the efficiency roll-off and the luminous life of the device are improved.
Alternatively, 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. Wherein, for top emission light emitting device, cathode 20 may be made of transparent material, and for bottom emission light emitting device, anode 10 may be made of transparent material, which is not particularly limited in the embodiment of the present invention.
Fig. 3 shows a cross-sectional view of yet another light emitting device of the first embodiment of the present invention, optionally referring to fig. 3, the light emitting device further comprises at least one of an electron blocking layer 80 and a hole blocking layer 90.
Wherein, 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 have also performed a series of calculations and tests on light emitting devices prepared using thermally activated delayed fluorescence materials (comparative examples), and on light emitting devices prepared using the thermally exciton fluorescent compounds provided in the examples of the present invention (example 1, example 2, example 3), the results of which are shown in table 1 below.
TABLE 1
Wherein lambda PL is photoluminescence spectrum, PLQY is photoluminescence quantum yield, EQE max is external quantum efficiency, roll-Off is efficiency, CIE is chromaticity coordinates, lambda PL is luminescence wavelength.
Compared with the prior art, the embodiment of the invention selects the luminescent material with higher luminous efficiency, and the energy transfer rate of the luminescent material is improved through the calibration of the triplet Tn energy level (1 < n < 4) and the singlet S1 energy level, so that the triplet utilization rate is improved, and the luminous efficiency is also improved.
The thermoexciton fluorescent compound can open a thermoexciton transmission channel, and the intersystem crossing occurs at a higher energy level, so that the triplet state energy accumulation under high current density is reduced, and the problems of low efficiency roll-off and short luminous life of the thermoactivation delayed fluorescent material are solved.
The thermoexciton fluorescent compound provided by the embodiment of the invention does not need to have hybridized local charge Transfer state (Hybrid Locally-detected AND CHARGE-transferred, HLCT) thermoexciton fluorescent characteristics, and correspondingly, the thermoexciton channel is not limited to hybridized local charge Transfer state thermoexciton process any more, so that the optional types of the thermoexciton fluorescent material are increased, more thermoexciton fluorescent materials with molecular mass suitable for evaporation process can be found, and specific combination of D-A structures is enriched so as to adapt to the polarity requirement of the material and the carrier transmission characteristic requirement.
The molecule design of the thermoexciton fluorescent compound provided by the embodiment of the invention further prolongs the molecular length of the molecular axis, improves the molecular orientation, enhances the linear polarized light proportion vertical to the light emitting plane, and improves the light extraction efficiency. The degree of molecular twist and molecular design also increases the spatial distance between molecules, further reducing triplet exciton accumulation and interaction.
The embodiment of the invention controls the relative molecular mass of the thermoexciton fluorescent compound within 1000, screens and controls substituent groups in the thermoexciton fluorescent compound, increases the molecular dihedral angle, is beneficial to vapor deposition film formation of materials and fully exerts the performance of devices.
In an embodiment of the invention, a light emitting device comprises an anode, a cathode, and a light emitting layer between the anode and the cathode, the light emitting layer comprising a thermo-exciton fluorescent compound, the thermo-exciton fluorescent compound having a relative molecular mass greater than 700 and less than 1000, the thermo-exciton fluorescent compound comprising a phenanthroimidazole derivative, an anthracene derivative, and a high triplet energy molecule connected in sequence, the phenanthroimidazole derivative having a first pendent group, the anthracene derivative having a second pendent group and a third pendent group. The thermoexciton fluorescent compound has better intersystem channeling performance, and intersystem channeling occurs at a higher energy level, so that triplet energy accumulation under high current density can be reduced, thereby improving the efficiency roll-off of the light emitting device and prolonging the service life of the light emitting device. In addition, the relative molecular mass of the thermoexciton fluorescent compound is within 1000, which is favorable for the vapor deposition of luminescent materials. Thus, the preparation difficulty and the improvement of the efficiency roll-off and the luminous life are considered.
Example two
The embodiment of the invention also discloses a display panel which comprises the light-emitting device.
In an embodiment of the invention, a light emitting device comprises an anode, a cathode, and a light emitting layer between the anode and the cathode, the light emitting layer comprising a thermo-exciton fluorescent compound having a relative molecular mass greater than 700 and less than 1000, the thermo-exciton fluorescent compound comprising a phenanthroimidazole derivative, an anthracene derivative, and a high triplet energy level molecule connected in sequence. The thermoexciton fluorescent compound has better intersystem channeling performance, and intersystem channeling occurs at a higher energy level, so that triplet energy accumulation under high current density can be reduced, thereby improving the efficiency roll-off of the light emitting device and prolonging the service life of the light emitting device. In addition, the relative molecular mass of the thermoexciton fluorescent compound is within 1000, which is favorable for the vapor deposition of luminescent materials. Thus, the preparation difficulty and the improvement of the efficiency roll-off and 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 between the anode and the cathode, the light emitting layer including a thermo-exciton fluorescent compound having a relative molecular mass of more than 700 and less than 1000, the thermo-exciton fluorescent compound including a phenanthroimidazole derivative, an anthracene derivative, and a high triplet energy level molecule connected in this order. The thermoexciton fluorescent compound has better intersystem channeling performance, and intersystem channeling occurs at a higher energy level, so that triplet energy accumulation under high current density can be reduced, thereby improving the efficiency roll-off of the light emitting device and prolonging the service life of the light emitting device. In addition, the relative molecular mass of the thermoexciton fluorescent compound is within 1000, which is favorable for the vapor deposition of luminescent materials. Thus, the preparation difficulty and the improvement of the efficiency roll-off and the luminous life are considered.
For the foregoing method embodiments, for simplicity of explanation, the methodologies are shown as a series of acts, but one of ordinary skill in the art will appreciate that the present invention is not limited by the order of acts, as some steps may, in accordance with the present invention, occur in other orders or concurrently. Further, those skilled in the art will also appreciate that the embodiments described in the specification are all preferred embodiments, and that the acts and modules referred to are not necessarily required for the present invention.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described by differences from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.
Finally, it is further noted that relational terms such as first and second, and the like are 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. Moreover, 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 one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises the element.
The above description of the light emitting device, the display panel and the display device provided by the invention applies specific examples to illustrate the principles and embodiments of the invention, and the above examples are only used to help understand the method and core ideas of the invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Claims (12)
1. A light emitting device comprising an anode, a cathode, and a light emitting layer between the anode and the cathode, the light emitting layer comprising a thermo-exciton fluorescent compound having a relative molecular mass greater than 700 and less than 1000, the thermo-exciton fluorescent compound comprising a phenanthroimidazole derivative, an anthracene derivative, and a high triplet energy level molecule connected in sequence;
wherein the thermoexciton fluorescent compound satisfies the following general formula:
wherein X is the high triplet energy level molecule, L1 is a first bond bridge between the phenanthroimidazole derivative and the anthracene derivative, L2 is a second bond bridge between the anthracene derivative and the high triplet energy 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;
Wherein the front-line orbitals of the thermoexciton fluorescent compound satisfy the following energy level relationship:
-HOMO 1-LUMO 1-1.44 eV, or-HOMO 2-LUMO 1-1.44 eV;
│HOMO1-HOMO2│＞0.3eV；
│LUMO1-LUMO2│＞0.2eV；
wherein, the HOMO1 is a first highest occupied molecular orbital energy level, the HOMO2 is a second highest occupied molecular orbital energy level, and the HOMO1 is higher than the HOMO2; the LUMO1 is a first lowest unoccupied molecular orbital energy level, the LUMO2 is a second lowest unoccupied molecular orbital energy level, and the LUMO1 is higher than the LUMO2;
wherein the high triplet energy level molecule comprises an aromatic compound comprising a heteroatom comprising one or two of boron, nitrogen, oxygen, sulfur, phosphorus.
2. The light-emitting device according to claim 1, wherein the thermo-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 1 < n < 4.
3. The light-emitting device according to claim 1, wherein a triplet T1 level of the high triplet level molecule is greater than 2.7eV.
4. The light-emitting device according to claim 1, wherein a triplet T1 level of the thermo-exciton fluorescent compound is less than 2.0eV and a triplet T2 level of the thermo-exciton fluorescent compound is greater than 2.7eV.
5. The light-emitting device of claim 1 wherein the molecular orientation factor of the light-emitting layer is greater than 66%.
6. The light-emitting device according to claim 1, 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.
7. The light-emitting device according to claim 1, 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.
8. The light-emitting device according to claim 1, wherein the light-emitting device is a blue light-emitting device.
9. The light-emitting device according to any one of claims 1 to 8, further comprising a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer.
10. The light emitting device of claim 9, further comprising at least one of an electron blocking layer and a hole blocking layer.
11. A display panel comprising the light-emitting device according to any one of claims 1 to 10.
12. A display device comprising the display panel of claim 11.
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