CN112701231B - Organic electroluminescent device and display device - Google Patents

Organic electroluminescent device and display device Download PDF

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CN112701231B
CN112701231B CN202011642254.5A CN202011642254A CN112701231B CN 112701231 B CN112701231 B CN 112701231B CN 202011642254 A CN202011642254 A CN 202011642254A CN 112701231 B CN112701231 B CN 112701231B
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triplet
organic electroluminescent
electroluminescent device
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CN112701231A (en
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段炼
蔡明瀚
王宏宇
曹方义
张先平
梁倩倩
魏现鹤
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Tsinghua University
Kunshan Govisionox Optoelectronics Co Ltd
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Kunshan Govisionox Optoelectronics Co Ltd
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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
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
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Abstract

The invention provides an organic electroluminescent device and a display device, the organic electroluminescent device includes a light emitting layer; the light-emitting layer includes a triplet-triplet annihilation material and a resonance-type thermally activated delayed fluorescence material; the first excited singlet energy level of the triplet-triplet annihilation material is greater than the first excited singlet energy level of the resonant thermal activation delayed fluorescence material, and the first excited triplet energy level of the triplet-triplet annihilation material is less than the first excited triplet energy level of the resonant thermal activation delayed fluorescence material. Wherein the spin-orbit coupling constant SOC of the n-th excited triplet state and the first excited singlet state of the triplet-triplet annihilation material satisfies the following requirement, n is more than or equal to 2 and less than or equal to 6: SOC is more than or equal to 0.30cm ‑1 . The organic electroluminescent device has excellent luminous efficiency, service life and color purity.

Description

Organic electroluminescent device and display device
Technical Field
The invention relates to an organic electroluminescent device and a display device, and belongs to the technical field of organic electroluminescence.
Background
An organic electroluminescent device is a device that achieves light emission by current driving. Specifically, the organic electroluminescent device includes a cathode, an anode, and functional layers such as a light-emitting layer between the cathode and the anode. When a voltage is applied, electrons from the cathode and holes from the anode migrate to the light emitting layer and combine to generate excitons, respectively, thereby emitting light of different wavelengths according to the characteristics of the light emitting layer.
At present, the blue light material for organic electroluminescent devices on the production line is mainly a common triplet-triplet annihilation material (TTA), which utilizes the annihilation effect of triplet excitons to increase the total amount of singlet excitons, and theoretically, the theoretical limit efficiency of TTA can reach 62.5%.
However, the exciton utilization rate in practical process is often far lower than 62.5%, so the efficiency and the service life of the corresponding organic electroluminescent device can not meet the requirements. In addition, the half-peak width of the common TTA is wide at present, which not only can cause the blue light color coordinate not to reach the standard, but also can cause a certain 'blue harm' problem.
Disclosure of Invention
The invention provides an organic electroluminescent device, which not only can improve the exciton utilization rate of a triplet-triplet annihilation material by pertinently limiting the composition of a light-emitting layer, but also can effectively reduce the high-energy exciton concentration in a system, thereby improving the luminous efficiency, the service life and the color purity of the organic electroluminescent device.
The present invention provides a display device including the above organic electroluminescent device, and thus having excellent luminous efficiency, lifespan, and color purity.
The invention provides an organic electroluminescent device, comprising a luminescent layer; the light-emitting layer includes a triplet-triplet annihilation material and a resonance-type thermally activated delayed fluorescence material; a first excited singlet energy level of the triplet-triplet annihilation material is greater than a first excited singlet energy level of the resonant thermal-activation delayed fluorescence material, and a first excited triplet energy level of the triplet-triplet annihilation material is less than a first excited triplet energy level of the resonant thermal-activation delayed fluorescence material;
wherein the spin-orbit coupling constant SOC of the n-th excited triplet state and the first excited singlet state of the triplet-triplet annihilation material meets the following requirement, n is more than or equal to 2 and less than or equal to 6: SOC is more than or equal to 0.30cm -1 。
Alternatively, the triplet-triplet annihilation material has the structure of formula 1,
Figure BDA0002880019960000011
in the formula 1, A is selected from anthryl, naphthyl, perylenyl, pyrenyl, fluorenyl, phenanthryl, fluoranthenyl, phenylpropenanthryl,
Figure BDA0002880019960000012
One of the group and acenaphthylene, X is independently selected from a group with heteroatom, and m is more than or equal to 1.
Alternatively, in formula 1, X is selected from substituted or unsubstituted C 3 -C 30 Heterocyclic group of (1), C substituted by functional substituent 6 -C 30 One of the aryl groups of (a); the functional substituent is selected from C 3 -C 30 At least one of a heterocyclic group, a straight chain group containing a hetero atom, and a branched group containing a hetero atom.
Alternatively, in formula 1, the X contains 1-10 heteroatoms.
Optionally, in formula 1, the distance between at least one heteroatom in X and the centroid of A is ≦ 10 angstroms.
Optionally, in formula 1, the distance between at least one heteroatom in X and the centroid of A is ≦ 7 angstroms.
Alternatively, the triplet-triplet annihilation material is a compound having one of the structures shown as a1-a 423.
Optionally, in the light-emitting layer, the resonance-type thermally activated delayed fluorescence material has a mass of 0.5% to 30% of the triplet-triplet annihilation material.
Optionally, the thickness of the light emitting layer is 5-100 nm.
The invention also provides a display device comprising the organic electroluminescent device.
The organic electroluminescent device adopts a triplet-triplet annihilation material (TTA material) as a main material to sensitize a resonance type thermal activation delayed fluorescence material (resonance type TADF material) to emit light. The spin-orbit coupling constant SOC of the n-th excited triplet state and the first excited singlet state of the TTA material is higher, so that the intermediate state and the n-th excited triplet state excitons with triplet characteristics can rapidly cross to the first excited singlet state in the TTA process, the phenomenon of energy loss caused by too low crossing speed of the triplet state excitons to the first excited singlet state is greatly inhibited, the exciton utilization rate is further improved, the luminous efficiency and the service life of the organic electroluminescent device are improved, and the efficiency roll-off of the organic electroluminescent device caused by overlong lifetime of the triplet state excitons under high brightness is also reduced. In addition, the resonance type thermal activation delayed fluorescence material is adopted as the dye to emit light, so that the organic electroluminescent device has good color purity.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
A first aspect of the present invention provides an organic electroluminescent device comprising an anode, a hole transport region, a light-emitting layer, an electron transport region, and a cathode sequentially deposited on a substrate.
The substrate, the anode, the hole transport region, the electron transport region, and the cathode may be made of materials commonly used in the art. For example, a glass or polymer material having excellent mechanical strength, thermal stability, water resistance, and transparency; the anode material can be Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), and tin dioxide (SnO) 2 ) Oxide transparent conductive materials such as zinc oxide (ZnO), and any combination thereof; the cathode can be made of magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag), etcGold and any combination thereof.
The light-emitting layer will be described in detail below.
The light-emitting layer of the present invention includes a triplet-triplet annihilation material and a resonance-type thermally activated delayed fluorescence material; a first excited singlet energy level of the triplet-triplet annihilation material is greater than a first excited singlet energy level of the resonant thermal-activation delayed fluorescence material, and a first excited triplet energy level of the triplet-triplet annihilation material is less than a first excited triplet energy level of the resonant thermal-activation delayed fluorescence material; wherein the spin-orbit coupling constant SOC of the n-th excited triplet state and the first excited singlet state of the triplet-triplet annihilation material meets the following requirements, n is more than or equal to 2 and less than or equal to 6, and the SOC is more than or equal to 0.30cm -1 。
In the art, a TTA material is a material that increases the total amount of singlet excitons by utilizing an annihilation effect of the triplet excitons and is capable of emitting fluorescence. Specifically, two triplet excitons collide with each other to form nine possible intermediate states, wherein 1/9 has a singlet characteristic, 1/3 has a triplet characteristic, and 5/9 has a quintet characteristic, and the specific energy path is shown in path 1:
Figure BDA0002880019960000021
since the quintet exciton is extremely unstable and not easy to form, the intermediate 1/4 formed when two triplet excitons collide with each other has singlet characteristics, 3/4 has triplet characteristics, and the two are finally converted into the first excited singlet exciton and the ground state molecule, and the first excited triplet molecule and the ground state molecule, respectively, and the specific energy path is shown in path 2:
Figure BDA0002880019960000022
whereas, if the intermediate state of the TTA material with triplet characteristics in pathway 2 is finally transformed into the first excited singlet and ground state molecules in the form of pathway 3, the theoretical ultimate efficiency of TTA can reach 0.25+ 0.75/2-62.5%.
Figure BDA0002880019960000023
That is, according to route 2, two first excited triplet excitons of the TTA material can generate an intermediate state having a singlet characteristic with a probability of 1/4 and an intermediate state having a triplet characteristic with a probability of 3/4 after colliding with each other. Wherein intermediate states characterized by singlet states eventually generate a ground state molecule and a first excited singlet exciton. While intermediate states characterized by a triplet state have two sub-paths. The first sub-path (i.e., the energy path of the intermediate state of the triplet character in path 2) is to generate a ground state molecule and an n (n ≧ 2) th excited triplet exciton, and the newly generated n-th excited triplet exciton may return to the first excited triplet state or undergo intersystem crossing to the first excited singlet state; the other sub-path (i.e., path 3) is the direct generation of a first excited singlet molecule and a ground state molecule.
In the invention, the spin-orbit coupling constant SOC (not less than 0.3 cm) between the n-th excited triplet state and the first excited singlet state is adopted -1 ) The relatively high TTA material is used as a main material for sensitizing resonance type TADF material to emit fluorescence, so that the luminous efficiency and the color purity of the organic electroluminescent device can be effectively improved, and the service life of the organic electroluminescent device is prolonged. Based on the phenomenon analysis, the inventor believes that the SOC of the TTA material of the present invention is high, so that the speed of the triplet characteristic intermediate state (including the above two sub-paths) crossing to the first excited singlet state system is increased, more first excited triplet excitons can be converted into the first excited singlet state through the TTA process, and energy is transferred to the resonance TADF material to emit fluorescence, so that the difference between the actual internal quantum efficiency and the theoretical internal quantum efficiency of the TTA material is reduced, and the organic electroluminescent device has the advantages of both high efficiency and high color purity. In addition, energetic triplet excitons are one of the key causes of roll-off, while the TTA materials of the present invention are intermediate in their triplet characterThe speed of the state crossing to the first excited singlet state is higher, so that the concentration of high-energy triplet excitons in the system is lower, the service life is shorter, and the roll-off of the organic electroluminescent device is improved to a certain extent.
The invention adopts the resonance type TADF material as the dye, and can further improve the utilization rate of excitons. Because the difference between the singlet state and the triplet state of the resonance type TADF material is small, the triplet excitons of the resonance type TADF material undergo intersystem crossing to the first excited singlet state and then transition back to the ground state to emit light by absorbing ambient heat; in addition, a part of the resonance type TADF material can not generate the transition of triplet excitons of intersystem crossing to the triplet energy level of the TTA material with lower energy level, thereby reducing the concentration of high-energy triplet excitons on the resonance type TADF material, further overcoming the problem that the efficiency of the organic electroluminescent device is seriously rolled down under high current density caused by the high-energy excitons, and further improving the stability of the device to a certain extent.
The resonance type TADF material is a material which has small difference between the energy levels of a singlet state and a triplet state (less than or equal to 0.5eV), weaker intramolecular charge transfer and high stability. For example, a compound having one of the following structures:
Figure BDA0002880019960000031
Figure BDA0002880019960000041
on one hand, the difference between the energy levels of the singlet state and the triplet state of the resonance type TADF material is very small, so that more triplet excitons are easy to undergo up-conversion to singlet state migration to generate delayed fluorescence; on the other hand, because the planar aromatic rigid structure and the molecules do not have obvious donor groups and acceptor groups, the planar conjugation is good, the intramolecular charge transfer is weak, and the stability is high, thereby being beneficial to narrowing the spectrum of the device and improving the color purity of the device.
Alternatively, when the SOC is further larger than 0.5cm -1 This is advantageous in further increasing the rate of intersystem crossing of the intermediate state of the triplet characteristic of the TTA material to the first excited singlet state.
Hereinafter, the energy transfer and the light emitting process of the organic electroluminescent device according to the present invention will be described in detail.
The luminescent layer of the organic electroluminescent device comprises a TTA material and a resonance type TADF material. Wherein the first excited singlet energy level of the TTA material is greater than the first excited singlet energy level of the resonant TADF material, and the first excited triplet energy level of the TTA material is less than the first excited triplet energy level of the resonant TADF material. After the hole and the electron are combined, singlet excitons and triplet excitons can be generated on the TTA material, the first excited triplet excitons in the TTA material can be annihilated pairwise to generate excitons of intermediate states with singlet state and triplet state characteristics, and the spin-orbit coupling constants SOC of the nth excited triplet state and the first excited singlet state of the TTA material are higher, so that the intersystem crossing speed of the intermediate states with triplet state characteristics to the first excited singlet state is higher, and more intermediate states with triplet state characteristics are transited to the first excited singlet state.
Since the first excited singlet level of the TTA material is greater than the first excited singlet level of the resonant TADF material, electrons in the first excited singlet state in the TTA material will be transferred to the first excited singlet state of the resonant TADF material
Figure BDA0002880019960000045
In contrast, most triplet excitons of the resonant TADF material undergo intersystem crossing to transit to the first excited singlet state, and some electrons that do not undergo intersystem crossing can transit to the first excited triplet state of the TTA material in a lower energy state, thereby causing the energy transfer. Therefore, the TTA material in the luminescent layer and the triplet excitons and the singlet excitons in the resonance type TADF material are efficiently utilized, and finally, the first excited singlet state of the resonance type TADF material returns to the ground state to emit fluorescence, so that the luminous efficiency of the organic electroluminescent device is improvedAnd (4) rate.
In addition, the n-th excited triplet exciton in the TTA material can be rapidly transited to the first excited singlet state, and part of electrons which cannot generate reverse intersystem crossing in the resonance TADF material can also be transited to the first excited triplet state of the TTA material with a lower energy state, so that the concentration of the high-energy triplet exciton in the whole system is low, the service life is short, the efficiency roll-off of the organic electroluminescent device is favorably inhibited, and the color purity is improved. Further, the present invention employs a resonance type TADF as a dye, which does not have a significant intramolecular charge transfer excited state inside the molecule, and thus can obtain a narrow emission spectrum.
The method for calculating the spin orbit coupling constant SOC of the n-th excited triplet state and the first excited singlet state of the TTA material specifically uses theoretical calculation software such as Gaussian, ADF, Gamess, VASP and the like to calculate the S-state spin orbit coupling constant SOC of the TTA material 0 ，S 1 ，T 1 ，T n Or S 1 -T n And after the optimal configuration in the transition state, calculating by software such as Gaussian, ORCA, PySOC, ADF, MOMAP and the like to obtain a spin orbit coupling constant SOC between the first excited singlet state and the n-th excited triplet state of the material.
As described above, the TTA material of the present invention has an SOC of not less than 0.3cm -1 . In one embodiment, the TTA material that satisfies the SOC has
The structure of the formula 1 is shown in the specification,
Figure BDA0002880019960000042
in the formula 1, A is selected from anthryl, naphthyl, perylenyl, pyrenyl, fluorenyl, phenanthryl, fluoranthenyl, phenylpropenanthryl,
Figure BDA0002880019960000043
One of the group and acenaphthylene, X is independently selected from a group with heteroatom, and m is more than or equal to 1.
In formula 1, m X's may be independently substituted for the hydrogen atom in A to form a bond with A. Wherein m X's may be different from each other, the same as each other, or partially the same. Optionally, m is an even number, and m xs are identical to each other and symmetrically connected to X, thereby facilitating maintaining the stability of the TTA material.
Anthryl, naphthyl, perylenyl, pyrenyl, fluorenyl, phenanthryl, fluoranthyl, phenylpropenanthryl, phenanthryl, and the like represented by A,
Figure BDA0002880019960000044
Acenaphthylene is a material in the art with a TTA luminescent mechanism. The above X is a group having a hetero atom, and the present invention is not limited to a specific structure of X as long as X has a hetero atom, and may be, for example, 1 to 10 hetero atoms. And the number and type of heteroatoms in each X may be independently selected and not before each other. Specifically, the lone pair of electrons of the heteroatom in the X can effectively enhance the proportion of n-pi in a single triplet state in the TTA material, so that the TTA material conforming to the structure has the SOC meeting the requirement, and the luminous efficiency, the service life and the color purity of the organic electroluminescent device can be optimized.
Further, X is selected from a cyclic group in which the ring-forming atoms include a hetero atom or an aromatic group substituted with a group having a hetero atom.
Wherein the cyclic group in which the ring-forming atoms include hetero atoms means substituted or unsubstituted C 3 -C 30 The heterocyclic group of (1). C 3 -C 30 The heterocyclic group of (A) means a cyclic group in which the ring-forming atoms include 3 to 30 carbon atoms and the ring-forming atoms include a hetero atom, C 3 -C 30 The heterocyclic group of (a) may be a heteroaryl group such as pyrimidinyl, pyrazinyl, thienyl, pyrrolyl, carbazolyl, indolyl, indazolyl, pyridyl, acridinyl, pyrazolyl, imidazolyl, thiazolyl, thienyl, etc., or a non-heteroaryl group such as piperazinyl, furyl, etc. The invention is not limited to C 3 -C 30 The specific atom bonded to A in the heterocyclic group of (2) may be a heteroatom of the ring-forming atom in X directly bonded to A, or may be another atom of the ring-forming atom of X directly bonded to A. When C is present 3 -C 30 When the heterocyclic group of (1) has a substituent, the present invention is not particularly limited with respect to the kind or number of the substituent, and for example, the substituent may be independently selected from the group consisting of halogen, cyano, and C 1 -C 10 Alkyl of (C) 2 -C 6 Alkenyl of, C 1 -C 6 Alkoxy or thioalkoxy of C 6 -C 30 Aryl of (C) 3 -C 30 One or more of (b) heteroaryl.
Aryl substituted by a group bearing a heteroatom means C substituted by a functional substituent 6 -C 30 Aryl group of (2). The functional substituent in the present invention means C 3 -C 30 A heterocyclic group containing a heteroatom, a straight chain group containing a heteroatom, and a branched group containing a heteroatom. C 3 -C 30 The heterocyclic group is the same as described above and is not described herein; by heteroatom-containing straight chain radical is meant a straight chain radical having from 0 to 30 carbon atoms containing a heteroatom, e.g. -NH 2 、-O-CH 3 、 -CH 2 -CH 2 -NH 2 、-CH 2 -O-CH 3 、-NH-CH 3 Etc.; heteroatom-containing branched radicals are branched radicals having from 3 to 30 carbon atoms containing heteroatoms, e.g. -O-CH (CH) 3 )-CH 3 、-CH 2 -CH(NH 2 )-CH 3 、-CH(OH)-CH 3 、-NH-CH(CH 3 )-CH 3 And the like. The invention is not restricted to the substitution of C 6 -C 30 And in addition to the functional substituents, C 6 -C 30 The other hydrogen atoms of the aryl radicals in question may also be simultaneously substituted by non-functional substituents, but it must be ensured that C is present 6 -C 30 Has a site in the aryl group to replace the hydrogen atom in a.
The heteroatom referred to herein means an atom other than carbon and hydrogen atoms, and the TTA material in which the heteroatom is a nitrogen atom, an oxygen atom, a phosphorus atom, a sulfur atom, a selenium atom, and a tellurium atom is exemplified herein. The inventor finds that the larger the atomic number of the same group element is, the more remarkable the improvement effect on the organic electroluminescent device is.
In the present invention, X is preferably a cyclic group in which the ring-forming atoms include a nitrogen atom. The structure of the TTA material is more stable, and the improvement of the performance of the organic electroluminescent device is facilitated.
Further, the present invention prefers TTA materials with a very strong induction effect. In formula 1, when the distance from at least one heteroatom in X to the centroid of a is less than or equal to 10 angstroms, the TTA material exhibits a stronger induction effect, and lone pair electrons of the heteroatom in X can further enhance the ratio of n-pi in a single triplet state in the TTA material, so that the SOC is larger, and the light-emitting efficiency and the lifetime of the organic electroluminescent device can be further optimized. The SOC of the TTA material is greater when the distance of at least one heteroatom in X to the centroid of a is smaller, e.g., 7 angstroms or less. It can be understood that, when the number of the heteroatoms less than or equal to 10 angstroms away from the centroid of the distance a in X is larger, the more significant the TTA material has effects of improving the light emitting efficiency of the organic electroluminescent device and prolonging the service life of the organic electroluminescent device.
The centroid of A as referred to herein refers to the closest point to all atoms in group A, and in the case of disubstituted naphthalene, the centroid of the naphthalene group is the closest point to a total of 22 atoms (14 carbon atoms and 8 hydrogen atoms) of the naphthalene, which can be determined, for example, by software such as Gaussian, Mercury, and Diamond (e.g., Centroids function in Mercury). The Distance of each heteroatom from the centroid of the group a in the TTA material having the structure of formula 1 can also be determined by software such as Gaussian, Mercury, and Diamond (e.g., measurement Distance function in Mercury, modification Bond function in Gaussian).
In particular embodiments, the TTA materials of the present invention may be, and are not limited to, compounds described by one of the following structures:
Figure BDA0002880019960000051
Figure BDA0002880019960000061
Figure BDA0002880019960000071
Figure BDA0002880019960000081
Figure BDA0002880019960000091
Figure BDA0002880019960000101
Figure BDA0002880019960000111
Figure BDA0002880019960000121
Figure BDA0002880019960000131
Figure BDA0002880019960000141
Figure BDA0002880019960000151
Figure BDA0002880019960000161
Figure BDA0002880019960000171
Figure BDA0002880019960000181
Figure BDA0002880019960000191
in addition, the performance of the organic electroluminescent device can be further optimized by controlling the ratio of the TTA material and the resonance type TADF material in the light-emitting layer.
In the implementation process of the invention, the proportion of TTA material and resonance type TADF material in the luminescent layer is reasonably controlled, which is beneficial to further improving the efficiency and color purity of the device. The inventors have found that when the mass of the resonant TADF material is 0.5-30% of the mass of the TTA material, the efficiency and lifetime of the organic electroluminescent device are improved to a large extent.
Generally, different host materials and dyes in the light emitting layer of an organic electroluminescent device have an effect on the performance of the device. In the invention, the SOC is more than 0.3cm -1 The TTA material and the resonant TADF material of (a) are used as the host material and the dye, respectively, and therefore, in general, when the mass of the resonant TADF material is 0.5 to 10% of the mass of the TTA material, and further 0.5 to 5%, excellent efficiency and lifetime of the device can be substantially ensured.
In the organic electroluminescent device, the thickness of the luminescent layer is generally controlled to be 5-100nm, so that the luminous efficiency and the service life of the organic electroluminescent device are ensured.
The hole transport region and the electron transport region of the present invention will be described below. The hole transport region is located between the anode and the light emitting layer. The hole transport region may be a Hole Transport Layer (HTL) of a single layer structure including a single layer containing only one compound and a single layer containing a plurality of compounds. The hole transport region may also be a multilayer structure including at least two layers of a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), and an Electron Blocking Layer (EBL).
The materials of the hole transport region, including HIL, HTL and EBL, may be selected from, but are not limited to, phthalocyanine derivatives such as CuPc, conductive polymers or polymers containing conductive dopants such as polyphenylenevinylene, polyaniline/dodecylbenzenesulfonic acid (Pani/DBSA), poly (3, 4-ethylenedioxythiophene)/poly (4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphorsulfonic acid (Pani/CSA), polyaniline/poly (4-styrenesulfonate) (Pani/PSS), aromatic amine derivatives.
Wherein the aromatic amine derivatives are compounds represented by the following HT-1 to HT-34. If the material of the hole transport region 3 is an aromatic amine derivative, it may be one or more of compounds represented by HT-1 to HT-34 and PH-47 to PH-85.
Figure BDA0002880019960000192
Figure BDA0002880019960000201
Figure BDA0002880019960000211
Figure BDA0002880019960000221
The hole injection layer is located between the anode and the hole transport layer. The hole injection layer may be a single compound material or a combination of a plurality of compounds. For example, the hole injection layer may employ one or more compounds of HT-1 to HT-34 described above, or one or more compounds of HI1-HI3 described below; one or more of the compounds HT-1 to HT-34 may also be used to dope one or more of the compounds HI1-HI3 described below. The thickness of the hole injection layer is generally 5 to 30nm, and the thickness of the hole transport layer is generally 5 to 50 nm.
Figure BDA0002880019960000222
The electron transport region may be an Electron Transport Layer (ETL) of a single-layer structure including a single-layer electron transport layer containing only one compound and a single-layer electron transport layer containing a plurality of compounds. The electron transport region may also be a multilayer structure including at least two layers of an Electron Injection Layer (EIL), an Electron Transport Layer (ETL), and a Hole Blocking Layer (HBL).
In one aspect, the electron transport layer material may be selected from, but is not limited to, the combinations of one or more of ET-1 to ET-57 and PH-1 to PH-46 listed below. The thickness of the electron transport layer is generally 5 to 30 nm.
Figure BDA0002880019960000223
Figure BDA0002880019960000231
Figure BDA0002880019960000241
Figure BDA0002880019960000251
Figure BDA0002880019960000261
The light emitting device may further include an electron injection layer between the electron transport layer and the cathode in the structure, and the electron injection layer includes, but is not limited to, one or more of the following combinations. The thickness of the electron injection layer is generally 0.5 to 5 nm.
LiQ,LiF,NaCl,CsF,Li 2 O,Cs 2 CO 3 ,BaO,Na,Li,Ca。
The thickness of the various layers described above may be any thickness conventional in the art for such layers.
The invention also provides a preparation method of the organic electroluminescent device, which comprises the steps of depositing the anode, the hole transmission area, the luminescent layer, the electron transmission area and the cathode on the substrate in sequence, and then packaging. When the luminescent layer is prepared, the evaporation rate of the TTA material and the evaporation rate of the resonance type TADF material are adjusted by a multi-source co-evaporation method to enable the dye to reach a preset doping ratio, and the luminescent layer is formed by any one of the methods of the TTA material source and the resonance type TADF material source through co-evaporation. The anode, the hole transport region, the electron transport region and the cathode are deposited in the same manner as the conventional manner in the art.
The embodiment of the invention also provides a display device which comprises the organic electroluminescent device provided as above. The display device can be specifically a display device such as an OLED display, and any product or component with a display function including the display device, such as a television, a digital camera, a mobile phone, a tablet computer, and the like. The display device has the same advantages as the organic electroluminescent device compared with the prior art, and the description is omitted here.
For example, the organic electroluminescent device can be used as a red light quantum dot film and a green light quantum dot film in a backlight excitation device, so that the color development area is improved.
The following will describe the specific preparation method of TTA material represented by formula 1 of the present invention by taking a plurality of synthesis examples as examples, but the preparation method of the present invention is not limited to these synthesis examples.
Basic chemical materials such as palladium tetrakistriphenylphosphine, sodium carbonate, toluene, tert-butyl lithium, tetrahydrofuran, ethanol, and various reaction materials used in the present invention were purchased from Beijing Bailingwei science and technology Co., Ltd and Beijing Yinuoka science and technology Co., Ltd. 1 The H-NMR spectrum was measured by means of a nuclear magnetic resonance spectrometer JNM-ECA600 of JEOL, Japan. The mass spectrum was measured using a high performance liquid-electrospray-ion trap/time-of-flight tandem mass spectrometer (Shimadzu) of Shimadzu, japan.
Synthetic examples
Synthesis example 1: synthesis of Compound A4
Figure BDA0002880019960000271
5-bromo-2-phenylpyridine (10g) was dissolved in super-dry tetrahydrofuran (200mL) under argon, and n-butyllithium (2.5M, 17mL) was slowly added to the above solution at-80 ℃. Then, anthracene-9, 10-dione (3.4g) was added in one portion. The resulting mixture was stirred for 2 hours, during which time the temperature was raised to 20 ℃. Subsequently, cold water (100mL) was added and the organic phase was separated. The aqueous phase was extracted with ethyl acetate (100 mL). The organic portion was dried over magnesium sulfate and the volatiles were removed in vacuo to leave a foamy solid. To the solid were added potassium iodide (14g), sodium hypophosphite (10g) and acetic acid (150mL), and the mixture was heated under reflux for 2 h. After cooling, the precipitate was collected and washed with copious amounts of THF/H2O (7: 3). After drying, 3.4g of yellow compound 1 were collected. The compound A4 has a hydrogen spectrum by nuclear magnetic resonance ( 1 HNMR) and High Resolution Mass Spectrometry (HRMS) were characterized as follows:
1 H NMR(600MHz,CDCl 3 -d6,δppm):8.86(s,2H),8,208(s,4H),8.085–8.028(m,2H),7.964(d, 2H),7.743(s,4H),7.582–7.513(m,6H),7.427(d,4H)；
HRMS(ESI)m/z:[M+H] + calcd for C 36 H 24 N 2 ,484.19；found,485.20.
synthesis example 2: synthesis of Compound A421
Figure BDA0002880019960000272
Under the protection of argon, 9, 10-bis (3-bromophenyl) anthracene (5.36g), pyridine-3-boric acid (3.10g) and palladium chloride (PdCl) 2 0.266g), triphenyl phosphite (0.786g), potassium carbonate (12.4g), toluene (166mL), ethanol (120mL) and distilled water (153mL) were added to the glass flask in that order. The reaction mixture was heated at reflux for 5h, and the organic portion was separated. The volatiles were removed in vacuo leaving a grey residue which was purified by silica gel column chromatography using petroleum ether/ethyl acetate (1: 1) as eluent. 3.7g of white Compound A421 are obtained. The compound is prepared by nuclear magnetic resonance hydrogen spectrum ( 1 HNMR) and highResolution Mass Spectrometry (HRMS) was characterized as follows:
1 H NMR(600MHz,CDCl 3 -d6,δ):8.97(s,2H),8.61(d,J＝7.2Hz,2H),7.97(d,J＝12.4Hz,2H), 7.81(s,2H),7.78–7.74(m,8H),7.56(t,J＝10Hz,2H),7.39–7.37(m,6H)；
HRMS(ESI)m/z:[M+H] + calcd for C 36 H 24 N 2 ,484.19；found,485.22.
synthetic example 3: synthesis of Compound A422
Figure BDA0002880019960000273
Under the protection of argon, 5- (10-bromoanthracene-9-yl) -2-phenylpyridine (4.09g), (4- (2-phenyl-1H-benzo [ d ]]Imidazol-1-yl) phenyl) boronic acid (3.14g) and tetrakis (triphenylphosphine) palladium (0) (1.5g) were dissolved in a mixture of ethanol (50mL) and toluene (100 mL). A solution of sodium carbonate (6.5g) in water (50mL) was added to the solution and stirred at 85 ℃ for 24 h. After cooling to room temperature, water (100mL), dichloromethane (100mL) was added and stirred. After filtering the solution, the solution was partitioned between dichloromethane and water. The product was extracted from the organic layer and evaporated under reduced pressure. The product was purified by column chromatography on silica gel using petroleum ether/ethyl acetate (1: 1) as eluent to give 4.8g of yellow compound A422. The compound is prepared by nuclear magnetic resonance hydrogen spectrum ( 1 HNMR) and High Resolution Mass Spectrometry (HRMS) were characterized as follows:
1 H NMR(600MHz,CDCl 3 -d6,δ):9.293(d,1H),8.484(d,2H),8.288(d,1H),8.225(d,1H), 8.152–8.135(m,1H),7.977–7.905(m,6H),7.804–7.768(m,2H),7.741–7.697(m,4H),7.674–7.607 (m,2H),7.588–7.491(m,9H)；
HRMS(ESI)m/z:[M+H]+calcd for C 44 H 29 N 3 ,599.24；found,599.3214.
hereinafter, the organic electroluminescent element according to the present invention will be further described with reference to specific examples.
Examples 1 to 20
Examples 1 to 20 each provide an organic electroluminescent device having a device structure including an ITO anode, a hole injection layer (HATCN, 5nm), a hole transport layer (NPB, 30nm), an electron blocking layer (TCTA, 10nm), a light-emitting layer, an electron transport layer (BPBiPA: Liq ═ 5: 5, 30nm), an electron injection layer (LiF, 1nm), and a cathode (Al, 150nm) in this order.
Figure BDA0002880019960000281
Wherein, the composition of the luminescent layer of each organic electroluminescent device is different, and the specific composition and the thickness of the luminescent layer are shown in table 1. The SOCs of TTA materials a5 and a9 in examples 6 and 7 are spin-orbit coupling constants of the third excited triplet state and the first excited singlet state, and the SOCs of TTA materials in the remaining examples are spin-orbit coupling constants of the second excited triplet state and the first excited singlet state.
Comparative examples 1 to 6
Comparative examples 1 to 6 provide organic electroluminescent devices having device structures in accordance with examples 1 to 20, and parameters of respective functional layers in accordance with examples 1 to 20, differing only in the composition of the light-emitting layer from those of the examples. The selection of specific materials is shown in table 1.
The structures of the host materials A1-A6, A9, A10, A12, A419 and A420 in Table 1 are as shown above, and the structures of A001 and A002 are as shown below
Figure BDA0002880019960000282
Figure BDA0002880019960000291
The electrical properties (EQE, spectrum and the like) of the device are obtained by adopting a Keithley2400 test carried by a Japanese Koimangson C9920-12 absolute electroluminescence quantum efficiency test system. When assuming that the device light extraction efficiency is 0.2 and the photoluminescence quantum efficiency is 1, the internal quantum efficiency of the material can be obtained by directly dividing the external quantum efficiency by 0.2. The lifetime of the devices was tested at 1000nits initial brightness using a model ZJZCL-2 lifetime testing equipment of Shanghai university.
TABLE 1
Figure BDA0002880019960000292
Figure BDA0002880019960000301
From table 1, it can be seen that:
1. compared with the comparative example, when the SOC is more than 0.3cm -1 When the TTA material is used, the organic electroluminescent device has small efficiency roll-off under high brightness, narrow half-peak width, better color purity and longer service life, and the overall characteristics of the organic electroluminescent device are obviously superior to those of comparative examples 1-6;
2. from examples 1 to 7 (the central group is an anthracene group, and the heteroatom is N), it can be seen that the larger the SOC is, the more excellent the overall performance of the organic electroluminescent device is;
although the SOC of the TTA material in example 14 was higher than that of the TTA material in example 3, the device performance of example 14 was slightly worse than that of example 3, probably because: compared with a nitrogen-containing heterocyclic ring, the TTA material in example 14 has poor stability of the methoxy group containing a heteroatom, and thus has some negative influence on the device performance of example 14;
although the SOC of the TTA material in example 16 was higher than that of the TTA material in example 6, the device performance of example 16 was slightly worse than that of example 6, probably because: compared with the TTA material in example 6, the TTA material in example 16 has too many free-mobile groups, so that the TTA material in example 16 has relatively poor stability, which may have some negative effects on the device performance of example 16;
3. it can be seen from comparative examples 2 and 8-12 that the performance of the organic electroluminescent device is better when the mass of the resonance type TADF material is 0.5-10% of the mass of the TTA material, and the performance of the organic electroluminescent device is more remarkably improved especially when the mass is 0.5-5%; when the mass of the resonance type TADF material is more than 10% of the mass of the TTA material, the performance of the organic electroluminescent device tends to decrease, but the performance is excellent as compared with the comparative example;
therefore, when the mass of the resonant TADF material is 0.5 to 10% of that of the TTA material, the organic electroluminescent device is more excellent in roll-off, lifetime, and half-peak width;
4. in examples 1, 4, 5, the device performance of example 1 was better than that of example 4, and the device performance of example 4 was better than that of example 5, probably because: the TTA materials in examples 1, 4, and 5 all contain 1N atom, but since the N atom of the TTA material in example 1 is closer to the centroid of anthracene (3.78 angstroms), the SOC of the TTA material in example 1 is larger, and thus more excellent performance is exhibited; since the centroid distance (5.16 angstroms) of the N atom and anthracene of the TTA material in example 4 is smaller than the centroid distance (7.93 angstroms) of the N atom and anthracene of the TTA material in example 5, the device performance of example 4 is more excellent than that of example 5;
similarly, in examples 2, 3 and 6, the centroid distance between the N atom of the TTA material and anthracene in example 2 (3.77 angstroms), the centroid distance between the N atom of the TTA material and anthracene in example 3 (5.16 angstroms), and the centroid distance between the N atom of the TTA material and anthracene in example 6 (7.95 angstroms), therefore, the device performance of example 2 is better than that of example 3, and the device performance of example 3 is better than that of example 6;
5. in examples 1 and 2, the device performance of example 2 was superior to that of example 1, probably because: compared with the example 1, the heteroatom is more in the example 2, so that the SOC of the TTA material in the example 2 is larger, and the more excellent performance is shown;
also, example 3 is superior to example 4 in device performance due to more heteroatoms in the TTA material in example 3 relative to example 4;
6. from examples 13 and 14, it can be seen that, when the heteroatoms are the same family atoms, the heteroatoms with larger atomic number are more beneficial to improve the device performance, probably because: atoms with larger atomic numbers enhance SOC more significantly because lone-pair electrons are closer to the central group.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (12)

1. An organic electroluminescent device comprising a light-emitting layer; the light-emitting layer includes a triplet-triplet annihilation material and a resonance-type thermally activated delayed fluorescence material; a first excited singlet energy level of the triplet-triplet annihilation material is greater than a first excited singlet energy level of the resonant thermal-activation delayed fluorescence material, and a first excited triplet energy level of the triplet-triplet annihilation material is less than a first excited triplet energy level of the resonant thermal-activation delayed fluorescence material;
wherein the spin-orbit coupling constant SOC of the n-th excited triplet state and the first excited singlet state of the triplet-triplet annihilation material satisfies the following requirement, n is more than or equal to 2 and less than or equal to 6:
SOC≥0.30cm -1 ；
the difference between the singlet state energy level and the triplet state energy level of the resonance type thermal activation delayed fluorescence material is less than or equal to 0.5 eV.
2. The organic electroluminescent device according to claim 1, wherein the triplet-triplet annihilation material has a structure of formula 1,
Figure FDA0003771658310000011
in formula 1A is selected from anthryl, naphthyl, perylenyl, pyrenyl, fluorenyl, phenanthryl, fluoranthenyl, benzophenanthryl, phenanthryl,
Figure FDA0003771658310000013
One of the group and acenaphthylene, X is independently selected from a group with heteroatom, and m is more than or equal to 1.
3. The organic electroluminescent device according to claim 2, wherein in formula 1, X is selected from substituted or unsubstituted C 3 -C 30 Heterocyclic group of (a), C substituted by a functional substituent 6 -C 30 One of the aryl groups of (a);
the functional substituent is selected from C 3 -C 30 At least one of a heterocyclic group, a straight chain group containing a hetero atom, and a branched group containing a hetero atom.
4. The organic electroluminescent device according to claim 2 or 3, wherein in formula 1, the X contains 1 to 10 heteroatoms.
5. The organic electroluminescent device according to claim 2 or 3, wherein in formula 1, the distance between at least one heteroatom in X and the centroid of A is 10 angstrom or less.
6. The organic electroluminescent device according to claim 4, wherein in formula 1, the distance between at least one heteroatom in X and the centroid of A is ≤ 10 angstroms.
7. The organic electroluminescent device according to claim 5, wherein in formula 1, the distance between at least one heteroatom in X and the centroid of A is less than or equal to 7 angstroms.
8. The organic electroluminescent device according to claim 6, wherein in formula 1, the distance between at least one heteroatom in X and the centroid of A is less than or equal to 7 angstroms.
9. The organic electroluminescent device according to any one of claims 1 to 3 and 6 to 8, wherein the triplet-triplet annihilation material is a compound having one of the structures shown below:
Figure FDA0003771658310000012
Figure FDA0003771658310000021
Figure FDA0003771658310000031
Figure FDA0003771658310000041
Figure FDA0003771658310000051
Figure FDA0003771658310000061
Figure FDA0003771658310000071
Figure FDA0003771658310000081
Figure FDA0003771658310000091
Figure FDA0003771658310000101
Figure FDA0003771658310000111
Figure FDA0003771658310000121
Figure FDA0003771658310000131
Figure FDA0003771658310000141
Figure FDA0003771658310000151
10. the organic electroluminescent device according to any one of claims 1 to 3 and 6 to 8, wherein the mass of the resonance type thermally activated delayed fluorescence material in the light-emitting layer is 0.5 to 30% of the mass of the triplet-triplet annihilation material.
11. The organic electroluminescent device according to any one of claims 1 to 3 and 6 to 8, wherein the thickness of the light-emitting layer is 5 to 100 nm.
12. A display device comprising the organic electroluminescent element as claimed in any one of claims 1 to 11.
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